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Among acute myeloid leukemia (AML) patients with a normal karyotype (CN-AML), NPM1and CEBPAmutations define World Health Organization 2008 provisional entities accounting for approximately 60% of patients, but the remaining 40% are molecularly poorly characterized. Using whole-exome sequencing of one CN-AML patient lacking mutations in NPM1, CEBPA, FLT3-ITD, IDH1, and MLL-PTD, we newly identified a clonal somatic mutation in BCOR(BCL6corepressor), a gene located on chromosome Xp11.4. Further analyses of 553 AML patients showed that BCORmutations occurred in 3.8% of unselected CN-AML patients and represented a substantial fraction (17.1%) of CN-AML patients showing the same genotype as the AML index patient subjected to whole-exome sequencing. BCORsomatic mutations were: (1) disruptive events similar to the germline BCORmutations causing the oculo-facio-cardio-dental genetic syndrome; (2) associated with decreased BCORmRNA levels, absence of full-length BCOR, and absent or low expression of a truncated BCOR protein; (3) virtually mutually exclusive with NPM1mutations; and (4) frequently associated with DNMT3Amutations, suggesting cooperativity among these genetic alterations. Finally, BCORmutations tended to be associated with an inferior outcome in a cohort of 422 CN-AML patients (25.6% vs 56.7% overall survival at 2 years; P= .032). Our results for the first time implicate BCORin CN-AML pathogenesis.

Among acute myeloid leukemia (AML) patients with a normal karyotype (CN-AML), NPM1 and CEBPA mutations define World Health Organization 2008 provisional entities accounting for approximately 60% of patients, but the remaining 40% are molecularly poorly characterized. Using whole-exome sequencing of one CN-AML patient lacking mutations in NPM1, CEBPA, FLT3-ITD, IDH1, and MLL-PTD, we newly identified a clonal somatic mutation in BCOR (BCL6 corepressor), a gene located on chromosome Xp11.4. Further analyses of 553 AML patients showed that BCOR mutations occurred in 3.8% of unselected CN-AML patients and represented a substantial fraction (17.1%) of CN-AML patients showing the same genotype as the AML index patient subjected to whole-exome sequencing. BCOR somatic mutations were: (1) disruptive events similar to the germline BCOR mutations causing the oculo-facio-cardio-dental genetic syndrome; (2) associated with decreased BCOR mRNA levels, absence of full-length BCOR, and absent or low expression of a truncated BCOR protein; (3) virtually mutually exclusive with NPM1 mutations; and (4) frequently associated with DNMT3A mutations, suggesting cooperativity among these genetic alterations. Finally, BCOR mutations tended to be associated with an inferior outcome in a cohort of 422 CN-AML patients (25.6% vs 56.7% overall survival at 2 years; P = .032). Our results for the first time implicate BCOR in CN-AML pathogenesis.

After the discovery of NPM1-mutated acute myeloid leukemia (AML) in 2005 and its subsequent inclusion as a provisional entity in the 2008 World Health Organization classification of myeloid neoplasms, several controversial issues remained to be clarified. It was unclear whether the NPM1 mutation was a primary genetic lesion and whether additional chromosomal aberrations and multilineage dysplasia had any impact on the biologic and prognostic features of NPM1-mutated AML. Moreover, it was uncertain how to classify AML patients who were double-mutated for NPM1 and CEBPA. Recent studies have shown that: (1) the NPM1 mutant perturbs hemopoiesis in experimental models; (2) leukemic stem cells from NPM1-mutated AML patients carry the mutation; and (3) the NPM1 mutation is usually mutually exclusive of biallelic CEPBA mutations. Moreover, the biologic and clinical features of NPM1-mutated AML do not seem to be significantly influenced by concomitant chromosomal aberrations or multilineage dysplasia. Altogether, these pieces of evidence point to NPM1-mutated AML as a founder genetic event that defines a distinct leukemia entity accounting for approximately one-third of all AML.

After the discovery of NPM1-mutated acute myeloid leukemia (AML) in 2005 and its subsequent inclusion as a provisional entity in the 2008 World Health Organization classification of myeloid neoplasms, several controversial issues remained to be clarified. It was unclear whether the NPM1mutation was a primary genetic lesion and whether additional chromosomal aberrations and multilineage dysplasia had any impact on the biologic and prognostic features of NPM1-mutated AML. Moreover, it was uncertain how to classify AML patients who were double-mutated for NPM1and CEBPA. Recent studies have shown that: (1) the NPM1mutant perturbs hemopoiesis in experimental models; (2) leukemic stem cells from NPM1-mutated AML patients carry the mutation; and (3) the NPM1mutation is usually mutually exclusive of biallelic CEPBAmutations. Moreover, the biologic and clinical features of NPM1-mutated AML do not seem to be significantly influenced by concomitant chromosomal aberrations or multilineage dysplasia. Altogether, these pieces of evidence point to NPM1-mutated AML as a founder genetic event that defines a distinct leukemia entity accounting for approximately one-third of all AML.

Acute myeloid leukemia (AML) with mutated NPM1 shows distinctive biologic and clinical features, including absent/low CD34 expression, the significance of which remains unclear. Therefore, we analyzed CD34+ cells from 41 NPM1-mutated AML. At flow cytometry, 31 of 41 samples contained less than 10% cells showing low intensity CD34 positivity and variable expression of CD38. Mutational analysis and/or Western blotting of purified CD34+ cells from 17 patients revealed NPM1-mutated gene and/or protein in all. Immunohistochemistry of trephine bone marrow biopsies and/or flow cytometry proved CD34+ leukemia cells from NPM1-mutated AML had aberrant nucleophosmin expression in cytoplasm. NPM1-mutated gene and/or protein was also confirmed in a CD34+ subfraction exhibiting the phenotype (CD34+/CD38−/CD123+/CD33+/CD90−) of leukemic stem cells. When transplanted into immunocompromised mice, CD34+ cells generated a leukemia recapitulating, both morphologically and immunohistochemically (aberrant cytoplasmic nucleophosmin, CD34 negativity), the original patient's disease. These results indicate that the CD34+ fraction in NPM1-mutated AML belongs to the leukemic clone and contains NPM1-mutated cells exhibiting properties typical of leukemia-initiating cells. CD34− cells from few cases (2/15) also showed significant leukemia-initiating cell potential in immunocompromised mice. This study provides further evidence that NPM1 mutation is a founder genetic lesion and has potential implications for the cell-of-origin and targeted therapy of NPM1-mutated AML.

Acute myeloid leukemia (AML) with mutated NPM1shows distinctive biologic and clinical features, including absent/low CD34 expression, the significance of which remains unclear. Therefore, we analyzed CD34+cells from 41 NPM1-mutated AML. At flow cytometry, 31 of 41 samples contained less than 10% cells showing low intensity CD34 positivity and variable expression of CD38. Mutational analysis and/or Western blotting of purified CD34+cells from 17 patients revealed NPM1-mutated gene and/or protein in all. Immunohistochemistry of trephine bone marrow biopsies and/or flow cytometry proved CD34+leukemia cells from NPM1-mutated AML had aberrant nucleophosmin expression in cytoplasm. NPM1-mutated gene and/or protein was also confirmed in a CD34+subfraction exhibiting the phenotype (CD34+/CD38−/CD123+/CD33+/CD90−) of leukemic stem cells. When transplanted into immunocompromised mice, CD34+cells generated a leukemia recapitulating, both morphologically and immunohistochemically (aberrant cytoplasmic nucleophosmin, CD34 negativity), the original patient's disease. These results indicate that the CD34+fraction in NPM1-mutated AML belongs to the leukemic clone and contains NPM1-mutated cells exhibiting properties typical of leukemia-initiating cells. CD34−cells from few cases (2/15) also showed significant leukemia-initiating cell potential in immunocompromised mice. This study provides further evidence that NPM1mutation is a founder genetic lesion and has potential implications for the cell-of-origin and targeted therapy of NPM1-mutated AML.

Mathematical models are finding an increasing use in bio-medical scientific investigations as effective means of putting the interpretation of biological phenomena on a more quantitative basis. Besides the well established mathematical paradigm based on differential equations, another approach that takes full advantage of the steadily increasing computing power, is gaining increasing consensus: micro-simulation. Micro-simulation is based on the idea of mimicking the behavior of the system under investigation through the specification of the rules of interaction among its individual constituents. This rule-driven (sometimes called equation-free) approach allows a smoother upgrade of models sophistication and reduces the gap between the abstract level of description typical of mathematical models and the complexity of the biological world. In this article we aim at illustrating, through specific examples, some of the potential advantages that micro-simulation has to offer in order to gain a better grasp and understanding of complex phenomena in biology and medicine.

Because of a lack of specific clonality markers, information on lineage involvement and cell of origin of acute myeloid leukemia with normal karyotype (AML-NK), is missing. Because Nucleophosmin (NPM)gene is frequently mutated in AML-NK and causes aberrant NPM cytoplasmic localization (NPMc+), it was used as an AML lineage clonality marker. Clonal NPMexon 12 mutations were detected in myeloid, monocytic, erythroid, and megakaryocytic cells but not in fibroblasts or endothelia that were laser-microdissected from 3 patients with NPMc+AML. Aberrant cytoplasmic expression of mutated NPM proteins was identified with anti-NPM antibodies in 2 or more myeloid hemopoietic cell lineages in 99 (61.5%) of 161 of NPMc+AML paraffin-embedded bone marrow biopsies; lymphoid involvement was excluded in 3 investigated cases. These findings suggest that NPMc+AML derives from either a common myeloid or earlier progenitor. Immunohistochemical studies show that varying combinations and ratios of NPMc+leukemic cells from distinct lineages are responsible for heterogeneity within each French-American-British (FAB) classification type and for NPMc+AML falling into different FAB categories. These findings question the value of FAB criteria in subdividing the WHO category of “AML not otherwise characterized” and suggest that, for clinical use, NPMc+AML be provisionally regarded as a separate AML with prognostic significance.

Because of a lack of specific clonality markers, information on lineage involvement and cell of origin of acute myeloid leukemia with normal karyotype (AML-NK), is missing. Because Nucleophosmin (NPM) gene is frequently mutated in AML-NK and causes aberrant NPM cytoplasmic localization (NPMc+), it was used as an AML lineage clonality marker. Clonal NPM exon 12 mutations were detected in myeloid, monocytic, erythroid, and megakaryocytic cells but not in fibroblasts or endothelia that were laser-microdissected from 3 patients with NPMc+ AML. Aberrant cytoplasmic expression of mutated NPM proteins was identified with anti-NPM antibodies in 2 or more myeloid hemopoietic cell lineages in 99 (61.5%) of 161 of NPMc+ AML paraffin-embedded bone marrow biopsies; lymphoid involvement was excluded in 3 investigated cases. These findings suggest that NPMc+ AML derives from either a common myeloid or earlier progenitor. Immunohistochemical studies show that varying combinations and ratios of NPMc+ leukemic cells from distinct lineages are responsible for heterogeneity within each French-American-British (FAB) classification type and for NPMc+ AML falling into different FAB categories. These findings question the value of FAB criteria in subdividing the WHO category of “AML not otherwise characterized” and suggest that, for clinical use, NPMc+ AML be provisionally regarded as a separate AML with prognostic significance.

Nucleophosmin (NPM)exon-12 mutations occur in 50% to 60% of adult acute myeloid leukemia (AML) with normal karyotype and are predictors of favorable prognosis. We evaluated bone marrow or peripheral blood samples from 450 adult patients with AML of the GIMEMA (Gruppo Italiano Malattie Ematologiche Maligne dell'Adulto)/AML12 EORTC (European Organization for Research and Treatment of Cancer) trial to (1) search for new exon-12 NPMmutations; (2) determine whether NPM immunostaining on paraffin-embedded biopsies predicts NPMmutations; and (3) investigate altered nucleocytoplasmic NPM traffic in primary AML cells. Fourteen NPMmutations, including 8 new variants, were identified. All 200 AML cases expressing cytoplasmic NPM (NPMc+AML) carried NPMmutations. None of the 250 cases with nucleus-restricted NPM (NPMc–AML) was mutated. At the C-terminus, NPM leukemic mutants carried mutations of only tryptophan 290 or of both tryptophans 288 and 290 and a new nuclear export signal (NES) motif, which appear to underlie their nuclear export. The specific Crm1/exportin-1 inhibitor leptomycin-B relocated NPM mutants from cytoplasm to nucleus of primary NPMc+AML cells, demonstrating that nuclear export is NES dependent. NPM mutants bound and recruited wild-type NPM into leukemic cell cytoplasm. Because alterations at C-terminus of leukemic NPM mutants are similar, immunohistochemistry detects all exon-12 NPMmutations and is a valuable, inexpensive tool in the diagnostic-prognostic work-up of patients with AML with normal karyotype.

Nucleophosmin (NPM) exon-12 mutations occur in 50% to 60% of adult acute myeloid leukemia (AML) with normal karyotype and are predictors of favorable prognosis. We evaluated bone marrow or peripheral blood samples from 450 adult patients with AML of the GIMEMA (Gruppo Italiano Malattie Ematologiche Maligne dell'Adulto)/AML12 EORTC (European Organization for Research and Treatment of Cancer) trial to (1) search for new exon-12 NPM mutations; (2) determine whether NPM immunostaining on paraffin-embedded biopsies predicts NPM mutations; and (3) investigate altered nucleocytoplasmic NPM traffic in primary AML cells. Fourteen NPM mutations, including 8 new variants, were identified. All 200 AML cases expressing cytoplasmic NPM (NPMc+ AML) carried NPM mutations. None of the 250 cases with nucleus-restricted NPM (NPMc– AML) was mutated. At the C-terminus, NPM leukemic mutants carried mutations of only tryptophan 290 or of both tryptophans 288 and 290 and a new nuclear export signal (NES) motif, which appear to underlie their nuclear export. The specific Crm1/exportin-1 inhibitor leptomycin-B relocated NPM mutants from cytoplasm to nucleus of primary NPMc+ AML cells, demonstrating that nuclear export is NES dependent. NPM mutants bound and recruited wild-type NPM into leukemic cell cytoplasm. Because alterations at C-terminus of leukemic NPM mutants are similar, immunohistochemistry detects all exon-12 NPM mutations and is a valuable, inexpensive tool in the diagnostic-prognostic work-up of patients with AML with normal karyotype.

Aberrant somatic hypermutation (SHM) has been identified as a mechanism for genomewide instability in diffuse large B-cell lymphoma (DLBCL). To assess whether aberrant SHM plays a role in the molecular pathogenesis of Hodgkin lymphoma (HL), we investigated microdissected neoplastic cells of nodular lymphocyte-predominant HL (NLPHL; n = 10) and classic HL (cHL; n = 9) for the presence of mutations in the 5′ sequences of 4 previously identified aberrant SHM targets (PIM1, PAX5, RhoH/TTF, c-MYC). Mutations in one or more genes were detected in 80% of NLPHLs and 55% of cHLs, with 50% and 30% of patients carrying mutations in 2 or more genes, respectively. The most frequently involved protooncogene was PAX5, mutated in 7 of 9 patients with NLPHL and 2 of 9 patients with cHL. In total, 34 mutations were detected in NLPHL (frequency, 1.04/1000 bp) and 35 were detected in patients with cHL (frequency, 1.92/1000 bp). Mutations were of somatic origin because they were absent in control T cells and shared most of the features of the immunoglobulin variable (IGV)gene–associated SHM mechanism—ie, single nucleotide substitutions (n = 63) with rare deletions/insertions (n = 6) and a predominance of transitions over transversions with preferential targeting motifs. Our finding that NLPHL and cHL are targeted by aberrant SHM, as is DLBCL, suggests that these lymphomas may share common molecular pathogenetic events.

Aberrant somatic hypermutation (SHM) has been identified as a mechanism for genomewide instability in diffuse large B-cell lymphoma (DLBCL). To assess whether aberrant SHM plays a role in the molecular pathogenesis of Hodgkin lymphoma (HL), we investigated microdissected neoplastic cells of nodular lymphocyte-predominant HL (NLPHL; n = 10) and classic HL (cHL; n = 9) for the presence of mutations in the 5′ sequences of 4 previously identified aberrant SHM targets (PIM1, PAX5, RhoH/TTF, c-MYC). Mutations in one or more genes were detected in 80% of NLPHLs and 55% of cHLs, with 50% and 30% of patients carrying mutations in 2 or more genes, respectively. The most frequently involved protooncogene was PAX5, mutated in 7 of 9 patients with NLPHL and 2 of 9 patients with cHL. In total, 34 mutations were detected in NLPHL (frequency, 1.04/1000 bp) and 35 were detected in patients with cHL (frequency, 1.92/1000 bp). Mutations were of somatic origin because they were absent in control T cells and shared most of the features of the immunoglobulin variable (IGV) gene–associated SHM mechanism—ie, single nucleotide substitutions (n = 63) with rare deletions/insertions (n = 6) and a predominance of transitions over transversions with preferential targeting motifs. Our finding that NLPHL and cHL are targeted by aberrant SHM, as is DLBCL, suggests that these lymphomas may share common molecular pathogenetic events.

We recently identified aberrant cytoplasmic expression of nucleophosmin (NPM) as the immunohistochemical marker of a large subgroup of acute myeloid leukemia (AML) (about one-third of adult AML) that is characterized by normal karyotype and mutations occurring at the exon-12 of the NPMgene. In this paper, we have elucidated the molecular mechanism underlying the abnormal cytoplasmic localization of NPM. All 29 AML-associated mutated NPMalleles so far identified encode abnormal proteins which have acquired at the C-terminus a nuclear export signal (NES) motif and lost both tryptophan residues 288 and 290 (or only the residue 290) which determine nucleolar localization. We show for the first time that both alterations are crucial for NPM mutant export from nucleus to cytoplasm. In fact, the cytoplasmic accumulation of NPM is blocked by leptomycin-B and ratjadones, specific exportin-1/Crm1-inhibitors, and by reinsertion of tryptophan residues 288 and 290, which respectively relocate NPM mutants in the nucleoplasm and nucleoli. NPM leukemic mutants in turn recruit the wild-type NPM from nucleoli to nucleoplasm and cytoplasm. These findings indicate that potential therapeutic strategies aimed to retarget NPM to its physiological sites will have to overcome 2 obstacles, the new NES motif and the mutated tryptophan(s) at the NPM mutant C-terminus.

We recently identified aberrant cytoplasmic expression of nucleophosmin (NPM) as the immunohistochemical marker of a large subgroup of acute myeloid leukemia (AML) (about one-third of adult AML) that is characterized by normal karyotype and mutations occurring at the exon-12 of the NPM gene. In this paper, we have elucidated the molecular mechanism underlying the abnormal cytoplasmic localization of NPM. All 29 AML-associated mutated NPM alleles so far identified encode abnormal proteins which have acquired at the C-terminus a nuclear export signal (NES) motif and lost both tryptophan residues 288 and 290 (or only the residue 290) which determine nucleolar localization. We show for the first time that both alterations are crucial for NPM mutant export from nucleus to cytoplasm. In fact, the cytoplasmic accumulation of NPM is blocked by leptomycin-B and ratjadones, specific exportin-1/Crm1-inhibitors, and by reinsertion of tryptophan residues 288 and 290, which respectively relocate NPM mutants in the nucleoplasm and nucleoli. NPM leukemic mutants in turn recruit the wild-type NPM from nucleoli to nucleoplasm and cytoplasm. These findings indicate that potential therapeutic strategies aimed to retarget NPM to its physiological sites will have to overcome 2 obstacles, the new NES motif and the mutated tryptophan(s) at the NPM mutant C-terminus.

We generated a murine monoclonal antibody (B28p) detecting an antigenic determinant shared by the immunoglobulin superfamily receptor translocation-associated 1 (IRTA1) receptor (the immunogen used to raise B28p) and an unrelated 28-kDa protein that was subsequently subjected to extensive characterization. The expression of the 28-kDa protein in normal lymphohematopoietic tissues was restricted to B cells and plasma cells and clearly differed from that expected for IRTA1 (selectively expressed by mucosa-associated lymphoid tissue [MALT] marginal zone B cells). Two-dimensional polyacrylamide gel electrophoresis (2D-PAGE)/mass-spectrometry analysis identified the 28-kDa protein as human tumor protein D52 (TPD52), whose expression had been previously described only in normal and neoplastic epithelia. Specific B28p reactivity with TPD52 was confirmed by immunostaining/immunoblotting of TPD52-transfected cells. TPD52 expression pattern in normal and neoplastic B cells was unique. In fact, unlike other B-cell molecules (paired box 5 [PAX5], CD19, CD79a, CD20, CD22), which are down-regulated during differentiation from B cells to plasma cells, TPD52 expression reached its maximum levels at the plasma cell stage. In the Thiel myeloma cell line, TPD52 bound to annexin VI in a Ca2+-dependent manner, suggesting that these molecules may act in concert to regulate secretory processes in plasma cells, similarly to what was observed in pancreatic acinar cells. Finally, the anti-TPD52 monoclonal antibody served as a valuable tool for the diagnosis of B-cell malignancies.

We generated a murine monoclonal antibody (B28p) detecting an antigenic determinant shared by the immunoglobulin superfamily receptor translocation-associated 1 (IRTA1) receptor (the immunogen used to raise B28p) and an unrelated 28-kDa protein that was subsequently subjected to extensive characterization. The expression of the 28-kDa protein in normal lymphohematopoietic tissues was restricted to B cells and plasma cells and clearly differed from that expected for IRTA1 (selectively expressed by mucosa-associated lymphoid tissue [MALT] marginal zone B cells). Two-dimensional polyacrylamide gel electrophoresis (2D-PAGE)/mass-spectrometry analysis identified the 28-kDa protein as human tumor protein D52 (TPD52), whose expression had been previously described only in normal and neoplastic epithelia. Specific B28p reactivity with TPD52 was confirmed by immunostaining/immunoblotting of TPD52-transfected cells. TPD52 expression pattern in normal and neoplastic B cells was unique. In fact, unlike other B-cell molecules (paired box 5 [PAX5], CD19, CD79a, CD20, CD22), which are down-regulated during differentiation from B cells to plasma cells, TPD52 expression reached its maximum levels at the plasma cell stage. In the Thiel myeloma cell line, TPD52 bound to annexin VI in a Ca2+-dependent manner, suggesting that these molecules may act in concert to regulate secretory processes in plasma cells, similarly to what was observed in pancreatic acinar cells. Finally, the anti-TPD52 monoclonal antibody served as a valuable tool for the diagnosis of B-cell malignancies.

The development of multiple myeloma (MM) bone disease is mediated by increased number and activity of osteoclasts (OCs). Using an in vitro osteoclastogenesis model consisting of unstimulated and unfractionated peripheral blood mononuclear cells (PBMCs) from patients with MM, we showed that T cells support the formation of OCs with longer survival. Different from T-cell–depleted MM PBMC cultures, exogenous macrophage-colony stimulating factor (M-CSF) and receptor activator of nuclear factor-κB ligand (RANKL) were necessary for the formation of OCs; however, they did not exhibit longer survival. We found up-regulated production of RANKL, osteoprotegerin (OPG), and TNF-related apoptosis-inducing ligand (TRAIL) by fresh MM T cells. Despite high OPG levels, the persistence of osteoclastogenesis can be related to the formation of the OPG/TRAIL complex demonstrated by immunoprecipitation experiments and the addition of anti-TRAIL antibody which decreases OC formation. OCs overexpressed TRAIL decoy receptor DcR2 in the presence of MM T cells and death receptor DR4 in T-cell–depleted cultures. In addition, increased Bcl-2/Bax (B-cell lymphoma-2/Bcl2-associated protein X) ratio, following Bcl-2 up-regulation, was detected in OCs generated in the presence of T cells. Our results highlight that MM T cells support OC formation and survival, possibly involving OPG/TRAIL interaction and unbalanced OC expression of TRAIL death and decoy receptors.

The development of multiple myeloma (MM) bone disease is mediated by increased number and activity of osteoclasts (OCs). Using an in vitro osteoclastogenesis model consisting of unstimulated and unfractionated peripheral blood mononuclear cells (PBMCs) from patients with MM, we showed that T cells support the formation of OCs with longer survival. Different from T-cell–depleted MM PBMC cultures, exogenous macrophage-colony stimulating factor (M-CSF) and receptor activator of nuclear factor-κB ligand (RANKL) were necessary for the formation of OCs; however, they did not exhibit longer survival. We found up-regulated production of RANKL, osteoprotegerin (OPG), and TNF-related apoptosis-inducing ligand (TRAIL) by fresh MM T cells. Despite high OPG levels, the persistence of osteoclastogenesis can be related to the formation of the OPG/TRAIL complex demonstrated by immunoprecipitation experiments and the addition of anti-TRAIL antibody which decreases OC formation. OCs overexpressed TRAIL decoy receptor DcR2 in the presence of MM T cells and death receptor DR4 in T-cell–depleted cultures. In addition, increased Bcl-2/Bax (B-cell lymphoma-2/Bcl2-associated protein X) ratio, following Bcl-2 up-regulation, was detected in OCs generated in the presence of T cells. Our results highlight that MM T cells support OC formation and survival, possibly involving OPG/TRAIL interaction and unbalanced OC expression of TRAIL death and decoy receptors.

Hairy cell leukemia (HCL) is a chronic B cell malignancy characterized by the diffuse infiltration of bone marrow and spleen by cells displaying a typical “hairy” morphology. However, the nature of the HCL phenotype and its relationship to normal B cells and to other lymphoma subtypes remains unclear. Using gene expression profiling, we show here that HCL displays a homogeneous pattern of gene expression, which is clearly distinct from that of other B cell non-Hodgkin lymphomas. Comparison with the gene expression profiles of purified normal B cell subpopulations, including germinal center (GC), pre-GC (naive), and post-GC (memory) B cells, shows that HCL cells are more related to memory cells, suggesting a derivation from this B cell population. Notably, when compared with memory cells, HCL cells displayed a remarkable conservation in proliferation, apoptosis, and DNA metabolism programs, whereas they appeared significantly altered in the expression of genes controlling cell adhesion and response to chemokines. Finally, these analyses have identified several genes that are specifically expressed in HCL and whose expression was confirmed at the protein level by immunocytochemical analysis of primary HCL cases. These results have biological implications relevant to the pathogenesis of this malignancy as well as clinical implications for its diagnosis and therapy.

Abstract: We report the use of Alemtuzumab (Campath-1H) as salvage treatment in three patients with advanced mycosis fungoides/Sézary syndrome who had previously been treated with conventional chemotherapy. Two patients (case 1 and case 2), aged 42 and 68 yr, respectively, were heavily pretreated (more than three prior therapy regimens, including autologous transplant in case 2) and refractory to conventional chemotherapy, and the third patient (case 3), aged 80 yr, who had refused any chemotherapy, had been resistant to treatment with cyclosporine and steroids. Campath-1H was administered intravenously, after an escalating dose from 3 to 10 mg, at the dose of 30 mg, three times weekly, to a total dose of 1080, 223, and 480 mg, respectively. The patients with Sézary syndrome (case 2 and case 3) showed clearance of circulating Sézary cells and clinical improvement of the skin lesions after 2 wk of treatment. Two patients (case 1 and case 3) completed the treatment (12 and 6 wk) without significant toxicity, the former achieving a partial response and the latter a clinical complete response. The patient (case 2), who suffered from ischemic cardiopathy and diabetes, quickly achieved a clinical improvement of the Sézary syndrome, but he died because of a myocardial infarction after 3 wk of treatment. Our report shows that the treatment with Campath-1H is active even in patients with advanced refractory mycosis fungoides/Sézary syndrome. Further clinical observations on a larger cohort of patients are needed to establish if Campath-1H may have a role as first line therapy in addition to conventional therapy including chemotherapy.

The idiotype (Id) determinants on the multiple myeloma immunoglobulin can serve as tumor-specific antigens. An anti-Id immune response may stem the growth of the malignant clone. We report on 26 patients treated at our institution with high-dose chemotherapy and peripheral blood progenitor cell transplantation (PBPCT) and vaccinated with the Id protein. The patients received chemotherapy and PBPCT to establish a minimal residual disease state. After high-dose therapy, the patients received a series of monthly immunizations consisting of 2 intravenous infusions of dendritic cells (DCs) pulsed with either Id protein or Id coupled with keyhole limpet hemocyanin (KLH) as an immunogenic carrier protein, followed by subcutaneous boosts of Id-KLH conjugates. DCs were obtained in all patients from a leukapheresis product 3 to 9 months after PBPCT. Patients were observed for toxicity, immune responses, and tumor status. The DC infusions and the administration of Id-KLH boosts were well tolerated, with patients experiencing only minor and transient side effects. Of the patients, 24 of 26 generated a KLH-specific cellular proliferative immune response. Only 4 patients developed an Id-specific proliferative immune response. Three of these immune responders were in complete remission at the time of vaccination. A total of 17 patients are alive at a median follow-up of 30 months after transplantation. Id vaccination with autologous DCs is feasible for myeloma patients after transplantation. Id-specific cellular responses can be induced in patients who are in complete remission. Further studies are needed to increase the rate of anti-Id immune responses in patients who do not achieve complete remission.

The idiotype (Id) determinant on the multiple myeloma (MM) protein can be regarded as a tumor-specific marker. Immunotherapy directed at the MM Id may stem the progression of this disease. We report here on the first 12 MM patients treated at our institution with high-dose therapy and peripheral blood stem cell transplantation (PBSCT) followed by Id immunizations. MM patients received PBSCT to eradicate the majority of the disease. PBSCT produced a complete response in 2 patients, a partial response in 9 patients and stable disease in 1 patient. Three to 7 months after high-dose therapy, patients received a series of monthly immunizations that consisted of two intravenous infusions of Id-pulsed autologous dendritic cells (DC) followed by five subcutaneous boosts of Id/keyhole limpet hemocyanin (KLH) administered with adjuvant. Between 1 and 11 × 106DC were obtained by leukapheresis in all patients even after PBSCT. The administration of Id-pulsed DC and Id/KLH vaccines were well tolerated with patients experiencing only minor and transient side effects. Two of 12 patients developed an Id-specific, cellular proliferative immune response and one of three patients studied developed a transient but Id-specific cytotoxic T-cell (CTL) response. Eleven of the 12 patients generated strong KLH-specific cellular proliferative immune responses showing the patients' immunocompetence at the time of vaccination. The two patients who developed a cellular Id-specific immune response remain in complete remission. Of the 12 treated patients, 9 are currently alive after autologous transplantation with a minimum follow-up of 16 months, 2 patients died because of recurrent MM and 1 patient succumbed to acute leukemia. These studies show that patients make strong anti-KLH responses despite recent high-dose therapy and that DC-based Id vaccination is feasible after PBSCT and can induce Id-specific T-cell responses. Further vaccine development is necessary to increase the proportion of patients that make Id-specific immune responses. The clinical benefits of Id vaccination in MM remain to be determined.

The idiotype (Id) determinant on the multiple myeloma (MM) protein can be regarded as a tumor-specific marker. Immunotherapy directed at the MM Id may stem the progression of this disease. We report here on the first 12 MM patients treated at our institution with high-dose therapy and peripheral blood stem cell transplantation (PBSCT) followed by Id immunizations. MM patients received PBSCT to eradicate the majority of the disease. PBSCT produced a complete response in 2 patients, a partial response in 9 patients and stable disease in 1 patient. Three to 7 months after high-dose therapy, patients received a series of monthly immunizations that consisted of two intravenous infusions of Id-pulsed autologous dendritic cells (DC) followed by five subcutaneous boosts of Id/keyhole limpet hemocyanin (KLH) administered with adjuvant. Between 1 and 11 × 106 DC were obtained by leukapheresis in all patients even after PBSCT. The administration of Id-pulsed DC and Id/KLH vaccines were well tolerated with patients experiencing only minor and transient side effects. Two of 12 patients developed an Id-specific, cellular proliferative immune response and one of three patients studied developed a transient but Id-specific cytotoxic T-cell (CTL) response. Eleven of the 12 patients generated strong KLH-specific cellular proliferative immune responses showing the patients’ immunocompetence at the time of vaccination. The two patients who developed a cellular Id-specific immune response remain in complete remission. Of the 12 treated patients, 9 are currently alive after autologous transplantation with a minimum follow-up of 16 months, 2 patients died because of recurrent MM and 1 patient succumbed to acute leukemia. These studies show that patients make strong anti-KLH responses despite recent high-dose therapy and that DC-based Id vaccination is feasible after PBSCT and can induce Id-specific T-cell responses. Further vaccine development is necessary to increase the proportion of patients that make Id-specific immune responses. The clinical benefits of Id vaccination in MM remain to be determined.

Acute promyelocytic leukemia (APL) is characterized by a reciprocal 15; 17 chromosomal translocation, which fuses the promyelocytic leukemia (PML) and retinoic acid receptor α (RARα) genes, leading to the expression of the PML/RARα fusion oncoprotein. Immunocytochemical labeling of the wild-type PML protein with the PG-M3 monoclonal antibody (MoAb) directed against the amino terminal portion of the human PML gene product, produces a characteristic nuclear speckled pattern that is due to localization of the protein into discrete dots (5 to 20 per nucleus), named PML nuclear bodies. The architecture of PML nuclear bodies appears to be disrupted in APL cells that bear the t(15; 17), thus resulting in a change of the nuclear staining pattern from speckled (wild-type PML protein) to microgranular (PML-RARα fusion protein). To assess whether the PG-M3 MoAb could assist in the diagnosis of APL (M3), bone marrow and/or peripheral blood samples from 100 cases of acute nonlymphoid leukemias of different subtypes were blindly immunostained with the PG-M3 MoAb, using the immunoalkaline phosphatase (APAAP) or immunofluorescence technique as detection system. Notably, the abnormal (micropunctate) pattern of the PML/RARα fusion protein (usually ≥50 small granules/per nucleus) was observed in APL (M3) samples, but not in other types of acute nonlymphoid leukemias. Immunocytochemical labeling with PG-M3 was particularly useful in the diagnosis of microgranular variant of APL (M3V) (three cases misdiagnosed as M4 and M5), and also to exclude a morphologic misdiagnosis of APL (six of 78 cases). In all cases investigated, immunocytochemical results were in agreement with those of reverse transcription-polymerase chain reaction (RT-PCR) for PML/RARα. Because the epitope identified by PG-M3 is located in the aminoterminal portion of PML (AA 37 to 51), the antibody was suitable for recognizing APL cases characterized by breakpoint occurring at different sites of PML (bcr 1, bcr 2 and bcr 3). In conclusion, immunocytochemical labeling with PG-M3 represents a rapid, sensitive, and highly-specific test for the diagnosis of APL that bears the t(15; 17). This should allow an easy and correct diagnosis of this subtype of acute leukemia to any laboratory provided with a minimal equipment for immunocytochemistry work.

Acute promyelocytic leukemia (APL) is characterized by a reciprocal 15; 17 chromosomal translocation, which fuses the promyelocytic leukemia (PML) and retinoic acid receptor α (RARα) genes, leading to the expression of the PML/RARα fusion oncoprotein. Immunocytochemical labeling of the wild-type PML protein with the PG-M3 monoclonal antibody (MoAb) directed against the amino terminal portion of the human PML gene product, produces a characteristic nuclear speckled pattern that is due to localization of the protein into discrete dots (5 to 20 per nucleus), named PML nuclear bodies. The architecture of PML nuclear bodies appears to be disrupted in APL cells that bear the t(15; 17), thus resulting in a change of the nuclear staining pattern from speckled (wild-type PML protein) to microgranular (PML-RARα fusion protein). To assess whether the PG-M3 MoAb could assist in the diagnosis of APL (M3), bone marrow and/or peripheral blood samples from 100 cases of acute nonlymphoid leukemias of different subtypes were blindly immunostained with the PG-M3 MoAb, using the immunoalkaline phosphatase (APAAP) or immunofluorescence technique as detection system. Notably, the abnormal (micropunctate) pattern of the PML/RARα fusion protein (usually ≥50 small granules/per nucleus) was observed in APL (M3) samples, but not in other types of acute nonlymphoid leukemias. Immunocytochemical labeling with PG-M3 was particularly useful in the diagnosis of microgranular variant of APL (M3V) (three cases misdiagnosed as M4 and M5), and also to exclude a morphologic misdiagnosis of APL (six of 78 cases). In all cases investigated, immunocytochemical results were in agreement with those of reverse transcription-polymerase chain reaction (RT-PCR) for PML/RARα. Because the epitope identified by PG-M3 is located in the aminoterminal portion of PML (AA 37 to 51), the antibody was suitable for recognizing APL cases characterized by breakpoint occurring at different sites of PML (bcr 1, bcr 2 and bcr 3). In conclusion, immunocytochemical labeling with PG-M3 represents a rapid, sensitive, and highly-specific test for the diagnosis of APL that bears the t(15; 17). This should allow an easy and correct diagnosis of this subtype of acute leukemia to any laboratory provided with a minimal equipment for immunocytochemistry work.

Fever-like hyperthermia is known to stimulate innate and adaptive immune responses. Although pyrogenic cytokines can stage the ground for immune defense (e.g. during the mobilization of lymphocytes to the lymphoid organs) hyperthermia per seis able to activate immune-competent cells and to induce a specific immunophenotype and gene expression profile. Hyperthermia-induced immune stimulation is also accompanied with, and likely conditioned by, changes in the cell metabolism and, in particular, mitochondrial metabolism is now recognized to play a pivotal role in this context, both as energy supplier and as signaling platform. In this study we asked if challenging human monocyte-derived dendritic cells with a relatively short-time thermal shock in the fever-range, typically observed in humans, caused alterations in the mitochondrial oxidative metabolism. We found that following hyperthermic stress (3 h exposure at 39°C) TNF-alpha-releasing dendritic cells undergo rewiring of the oxidative metabolism hallmarked by decrease of the mitochondrial respiratory activity and of the oxidative phosphorylation and increase of lactate production. Moreover, enhanced production of reactive oxygen and nitrogen species and accumulation of mitochondrial Ca2+was consistently observed in hyperthermia-conditioned dendritic cells and exhibited a reciprocal interplay. The hyperthermia-induced impairment of the mitochondrial respiratory activity was (i) irreversible following re-conditioning of cells to normothermia, (ii) mimicked by exposing normothermic cells to the conditioned medium of the hyperthermia-challenged cells, (iii) largely prevented by antioxidant and inhibitors of the nitric oxide synthase and of the mitochondrial calcium porter, which also inhibited release of TNF-alpha. These observations combined with gene expression analysis support a model based on a thermally induced autocrine signaling, which rewires and sets a metabolism checkpoint linked to immune activation of dendritic cells.

Falini: Xenomics: Patents & Royalties.

Abstract 480

The expression of CXCR4 (CD184) has been associated with poor prognosis in Acute Myeloid Leukemia (AML) and it has also been suggested that the CXCL12(SDF-1a)/CXCR4 interaction contributes to the resistance of leukemia cells to chemotherapy-induced apoptosis. Inhibition of CXCR4 was found to enhance chemotherapy-induced apoptosis in a subset of leukemic myeloblasts that carry Flt3 mutations and to overcome chemoresistance associated with stromal activity. NPM variants with a cytoplasmic localization represent the most common mutation detected in myeloid malignancies and are associated with a favourable clinical outcome. A recent study provides biological evidence for a novel role for NPM as a negative regulator of CXCR4 signalling induced by CXCL12: suppression of NPM expression enhanced chemotactic responses to CXCL12, and conversely, over-expression of a cytosolic NPM mutant reduced chemotaxis induced by CXCL12. We investigated whether CD184 expression is a negative predictor factor for response to chemotherapy and if there is clinical evidence that NPM mutations could overcome chemoresistance to induction therapy in this subset of patients. The expression of CD184 was analyzed by flow cytometric methods in a group of 70 cases of adult AML at onset of disease, diagnosed at our Institution since January 2006. The diagnosis was performed according to FAB/WHO criteria; all patients received intensive chemotherapy according to institutional protocols. There were 34 males and 36 females and median age was 46 years (range 18–65). AML cells were gated based upon their CD45 expression and samples were considered positive if CD184 was expressed by more than 20% of blasts. CD184 was positive in 45 and negative in 25 cases. There was no significant difference between the two groups in terms of sex, age, Hb level, WBC and Plt counts, percentage of blasts, and occurrence of the NPM mutation. The CR rate was 45% in CD184+ and 82% in CD184- (p=0.03); among CD184+ cases, the CR rate was significantly higher in NPMc+ cases, (p=0.03). Our results show that CD184 expression is associated with a lower rate of CR after induction therapy and this association is stronger in NPM unmutated cases, suggesting that CD184 expression is a negative predictive factor for response to chemotherapy. Further data are needed to verify if the biological role of the cytosolic NPM mutant as a negative regulator of CXCR4 signalling induced by CXCL12 could have a clinical role contributing to overcome the resistance of leukemic cells to induction chemotherapy.

Acute myeloid leukemia expressing mutated NPM1 gene and cytoplasmic nucleophosmin (NPMc+ AML) [Falini B et al, NEJM2005;352:254–266] is a new entity of WHO classification that shows distinctive biological and clinical features, including a unique molecular signature characterized by downregulation of CD34 and upregulation of most HOX genes [Falini B et al, Blood2007;109:874–885]. Involvement of HOX genes in the maintenance of the stem-cell phenotype strongly suggest that AML with mutated NPM1 originates from a multipotent hematopoietic progenitor (HSC). This view is also supported by immunohistological findings showing that AML with mutated NPM1 frequently displays multilineage involvement [Pasqualucci L et al, Blood2006;108:4146–4155]. On the other hand, the frequent negativity of NPMc+ AML for the HSC-associated antigen CD34 raises the question of whether the mutation event occurs in a CD34-negative HSC (these cells have been identified in mice) or whether a minimal pool of CD34-positive NPM1-mutated leukemic cells does exist. Currently, the hierarchical level of stem cell involvement in NPMc+ AML is unknown. To address this issue, we purified CD34+ cells from NPMc+ AML patients and detected NPM1 mutant protein in the sorted population by Western blot with anti-NPM mutant specific antibodies [Martelli MP et al, Leukemia 2008] (Figure 1A). We investigated 6 NPMc+ AML patients presenting at diagnosis with 0.12%, 0.14%, 0.38%, 5%, 22%, and 28% of CD34+ cells in the peripheral blood. In all cases, CD34+ fractions (purity >90%) harboured NPM1 mutant protein, indicating they belong to the leukemic clone (Figure 1B). The percentage of most undifferentiated CD34+/CD38− cells in the CD34+ fractions ranged from 5 to 97%. Notably, in at least one case, all CD34+ NPM1-mutated leukemic cells were CD38−negative. Moreover in all cases, CD34+ NPM1-mutated leukemic cells appeared to express CD123 (IL-3 receptor), considered a marker of the leukemic stem cell and target of potential therapy. Double staining of bone marrow biopsies with anti-CD34 and anti-NPM antibodies revealed that the rare CD34+ cells expressed NPM1 aberrantly in the cytoplasm. Inoculation of CD34+ NPM1-mutated AML cells into sublethally irradiated NOD/SCID mice resulted into leukemia engrafment in various body sites, especially bone marrow, spleen, lung and liver. Preliminary results showed that CD34+ leukemic cells reacquired the same leukemic phenotype as the original patient’s, including CD34-negativity of the leukemic bulk in spite of any lack of differentiation. This finding suggests that NPM1 mutant protein may be involved in downregulation of CD34 antigen, while keeping a gene expression profile typical of the hematopoietic stem cell. These findings suggest the CD34+ fraction contains the SCID-leukemia initiating cells (SL-IC) and point to CD34+/CD38− HSC as the cell of origin of AML with mutated NPM1. Figure Figure

The expression of CXCR4 (CD184) has been associated with poor prognosis in Acute Myeloid Leukemia (AML) and it has also been suggested that the CXCL12(SDF-1a)/CXCR4 interaction contributes to the resistance of leukemia cells to chemotherapy-induced apoptosis. Inhibition of CXCR4 was found to enhance chemotherapy-induced apoptosis in a subset of leukemic myeloblasts that carry Flt3 mutations and to overcome chemoresistance associated with stromal activity. NPM variants with a cytoplasmic localization represent the most common mutation detected in myeloid malignancies and are associated with a favourable clinical outcome. A recent study provides biological evidence for a novel role for NPM as a negative regulator of CXCR4 signalling induced by CXCL12: suppression of NPM expression enhanced chemotactic responses to CXCL12, and conversely, over-expression of a cytosolic NPM mutant reduced chemotaxis induced by CXCL12. We investigated whether CD184 expression is a negative predictor factor for response to chemotherapy and if there is clinical evidence that NPM mutations could overcome chemoresistance to induction therapy in this subset of patients. The expression of CD184 was analyzed by flow cytometric methods in a group of 70 cases of adult AML at onset of disease, diagnosed at our Institution since January 2006. The diagnosis was performed according to FAB/WHO criteria; all patients received intensive chemotherapy according to institutional protocols. There were 34 males and 36 females and median age was 46 years (range 18–65). AML cells were gated based upon their CD45 expression and samples were considered positive if CD184 was expressed by more than 20% of blasts. CD184 was positive in 45 and negative in 25 cases. There was no significant difference between the two groups in terms of sex, age, Hb level, WBC and Plt counts, percentage of blasts, and occurrence of the NPM mutation. The CR rate was 45% in CD184+ and 82% in CD184- (p=0.03); among CD184+ cases, the CR rate was significantly higher in NPMc+ cases, (p=0.03). Our results show that CD184 expression is associated with a lower rate of CR after induction therapy and this association is stronger in NPM unmutated cases, suggesting that CD184 expression is a negative predictive factor for response to chemotherapy. Further data are needed to verify if the biological role of the cytosolic NPM mutant as a negative regulator of CXCR4 signalling induced by CXCL12 could have a clinical role contributing to overcome the resistance of leukemic cells to induction chemotherapy.

Acute myeloid leukemia expressing mutated NPM1gene and cytoplasmic nucleophosmin (NPMc+ AML) [Falini B et al, NEJM 2005; 352:254–266] is a new entity of WHO classification that shows distinctive biological and clinical features, including a unique molecular signature characterized by downregulation of CD34 and upregulation of most HOXgenes [Falini B et al, Blood 2007; 109:874–885]. Involvement of HOXgenes in the maintenance of the stem-cell phenotype strongly suggest that AML with mutated NPM1originates from a multipotent hematopoietic progenitor (HSC). This view is also supported by immunohistological findings showing that AML with mutated NPM1frequently displays multilineage involvement [Pasqualucci L et al, Blood 2006; 108:4146–4155]. On the other hand, the frequent negativity of NPMc+ AML for the HSC-associated antigen CD34 raises the question of whether the mutation event occurs in a CD34-negative HSC (these cells have been identified in mice) or whether a minimal pool of CD34-positive NPM1-mutated leukemic cells does exist. Currently, the hierarchical level of stem cell involvement in NPMc+ AML is unknown. To address this issue, we purified CD34+ cells from NPMc+ AML patients and detected NPM1 mutant protein in the sorted population by Western blot with anti-NPM mutant specific antibodies [Martelli MP et al, Leukemia2008] (Figure 1A). We investigated 6 NPMc+ AML patients presenting at diagnosis with 0.12%, 0.14%, 0.38%, 5%, 22%, and 28% of CD34+ cells in the peripheral blood. In all cases, CD34+ fractions (purity >90%) harboured NPM1 mutant protein, indicating they belong to the leukemic clone (Figure 1B). The percentage of most undifferentiated CD34+/CD38− cells in the CD34+ fractions ranged from 5 to 97%. Notably, in at least one case, all CD34+ NPM1-mutated leukemic cells were CD38−negative. Moreover in all cases, CD34+ NPM1-mutated leukemic cells appeared to express CD123 (IL-3 receptor), considered a marker of the leukemic stem cell and target of potential therapy. Double staining of bone marrow biopsies with anti-CD34 and anti-NPM antibodies revealed that the rare CD34+ cells expressed NPM1 aberrantly in the cytoplasm. Inoculation of CD34+ NPM1-mutated AML cells into sublethally irradiated NOD/SCID mice resulted into leukemia engrafment in various body sites, especially bone marrow, spleen, lung and liver. Preliminary results showed that CD34+ leukemic cells reacquired the same leukemic phenotype as the original patient's, including CD34-negativity of the leukemic bulk in spite of any lack of differentiation. This finding suggests that NPM1 mutant protein may be involved in downregulation of CD34 antigen, while keeping a gene expression profile typical of the hematopoietic stem cell. These findings suggest the CD34+ fraction contains the SCID-leukemia initiating cells (SL-IC) and point to CD34+/CD38− HSC as the cell of origin of AML with mutated NPM1.

Acute myeloid leukemia (AML) carrying nucleophosmin (NPM1) mutations and cytoplasmic NPM (NPMc+ AML) accounts for about one-third of all AML patients, and exhibits distinctive biological and clinical features. The role of NPM1 mutations in leukemogenesis remains elusive. Mathematical models have been developed that, starting from cancer incidence data, allow to infer the somatic mutation rate, or the number of genetic events required to cause cancer. We collected data on age at diagnosis of AML patients from four centers in three different countries, and calculated age-specific rates of NPMc+ AML. A total of 4,155 AML patients were investigated. NPM1 mutations these were detected in 1288. Patients carrying NPM1 mutations with age below 20 years and above 59 years were excluded from the study because of the low number of younger cases and because older patients are not always referred to major institutions for diagnosis and treatment. To investigate NPMc+ AML we adapted one-mutation model published by Michor et al (PNAS, 2006; 103: 14931). The mathematical model consider a population of N (hemopoietic stem) cells that at beginning are wild-type. These cells proliferate according to the Moran process. The growth follows a logistic law with a saturation term. Our process follows the “classical” Moran process up to the appearance of a successful mutant. After that, the clone expands to a limiting population size. This is done to account for the dramatic expansion of the initial compartment peculiar of AML. Finally the rate of AML detection is proportional to the number of mutated cells. Experimental incidence curves of AML in Germany (Ge), Netherlands (Nl), and Italy (It) plotted simultaneously with predicted one-mutation model estimates are shown in Fig. 1. Linear regression of curves representing age-specific rate of diagnoses per year showed similar slopes (about 4 on a double-log scale) in different countries. The one-event model reproduces well the “exponential phenotype” of NPMc+ AML. In conclusion the model is in accordance with the hypothesis that NPM1 mutations by themselves are sufficient to cause NPMc+ AML. Alternatively, it is still possible that NPM1 mutations might cooperate with other molecular alterations to cause AML. In particular, since NPM1 mutations cause haploinsufficiency of wild-type NPM in leukemic cells and in knock-out mice NPM haploinsufficiency results in a MDS-like syndrome and given that the NPM1 mutant has oncogenic properties, these alterations could act in concert to cause AML. Indeed, the effect of these two alterations occurring simultaneously could be seen as a single genetic event. Figure Figure

Acute myeloid leukemia (AML) carrying nucleophosmin (NPM1)mutations and cytoplasmic NPM (NPMc+ AML) accounts for about one-third of all AML patients, and exhibits distinctive biological and clinical features. The role of NPM1mutations in leukemogenesis remains elusive. Mathematical models have been developed that, starting from cancer incidence data, allow to infer the somatic mutation rate, or the number of genetic events required to cause cancer. We collected data on age at diagnosis of AML patients from four centers in three different countries, and calculated age-specific rates of NPMc+ AML. A total of 4,155 AML patients were investigated. NPM1mutations these were detected in 1288. Patients carrying NPM1mutations with age below 20 years and above 59 years were excluded from the study because of the low number of younger cases and because older patients are not always referred to major institutions for diagnosis and treatment. To investigate NPMc+ AML we adapted one-mutation model published by Michor et al (PNAS , 2006; 103: 14931). The mathematical model consider a population of N (hemopoietic stem) cells that at beginning are wild-type. These cells proliferate according to the Moran process. The growth follows a logistic law with a saturation term. Our process follows the “classical” Moran process up to the appearance of a successful mutant. After that, the clone expands to a limiting population size. This is done to account for the dramatic expansion of the initial compartment peculiar of AML. Finally the rate of AML detection is proportional to the number of mutated cells. Experimental incidence curves of AML in Germany (Ge), Netherlands (Nl), and Italy (It) plotted simultaneously with predicted one-mutation model estimates are shown in Fig. 1. Linear regression of curves representing age-specific rate of diagnoses per year showed similar slopes (about 4 on a double-log scale) in different countries. The one-event model reproduces well the “exponential phenotype” of NPMc+ AML. In conclusion the model is in accordance with the hypothesis that NPM1mutations by themselves are sufficient to cause NPMc+ AML. Alternatively, it is still possible that NPM1mutations might cooperate with other molecular alterations to cause AML. In particular, since NPM1mutations cause haploinsufficiency of wild-type NPM in leukemic cells and in knock-out mice NPM haploinsufficiency results in a MDS-like syndrome and given that the NPM1 mutant has oncogenic properties, these alterations could act in concert to cause AML. Indeed, the effect of these two alterations occurring simultaneously could be seen as a single genetic event.

Extramedullary infiltration (EMI) of malignant myeloid precursor cells in acute myeloid leukemia (AML) may occasionally be a presenting clinical symptom at onset and may develop at any site in the body but most commonly in the gum, skin, central nervous system (CNS) and soft tissue. There is controversy about the prognostic significance of extramedullary disease in AML. The present study examines the incidence, the biological features and prognostic significance of EMI at diagnosis in adult patients with AML. From January 1997 to December 2004, 213 untreated patients with de novo AML were studied. According to Grimwade et al, 14 patients were in the favorable-risk group, 159 in the intermediate-risk group, 25 in the poor risk group and in 15 the karyotype was not available. All patients had been treated with induction therapy according to the GIMEMA protocols including cytarabine, etoposide and idarubicin (15 pts), or mitoxantrone (15 pts) or daunorubicin (183 pts). Of 213 cases with de novo AML, 29 (14%) had EMI at diagnosis. Ten patients (34.8%) had skin infiltrates, 12 (41.4%) had gum hypertrophy, 5 (17.2%) had CNS involvement and 2 (6.9%) had soft tissue infiltration. No significant differences in terms of sex, age median Hb level and platelets count were found between patients with EMI and patients without EMI. The patients with EMI had higher median WBC counts (27 × 109/L) than patients without EMI (8.5 × 109/L) (p=0.05). The patients with EMI had a higher incidence of the M4/M5 FAB subtype (62%) than patients without EMI (27.4%) (p=0.005). Cytogenetic analysis was performed in patients with and without EMI; none of the abnormal cytogenetic findings was associated with EMI. We evaluated the relationship between the AML blasts surface antigen expression and EMI; the association between CD56/CD4 and CD56/CD14 was more significantly expressed in patients with EMI (35% and 29%, respectively) than without EMI (10.4% and 6.9%, respectively) (p=0.004, p=0.003). The overall CR rate was 65%; the CR rate was lower in patients with EMI (48.2%) than patients without EMI (76.1%) (p=0.001) and their disease free survival was also shorter (p=0.017); the median duration of CR was 10 and 25 months (range 2–96) in EMI and no EMI group, respectively. Our data show that a high WBC count, M4/M5 subtype, CD56/CD4 and CD56/CD14 expression are associated with extramedullary infiltrates of AML at diagnosis; the presence of EMI adversely affects the complete response rate to induction chemotherapy and the OS rate. Analysis of the clinical and biologic features in a larger series of adult AML patients is needed to evaluate the allocation of this subgroup in a different or more intensive treatment arm.

Extramedullary infiltration (EMI) of malignant myeloid precursor cells in acute myeloid leukemia (AML) may occasionally be a presenting clinical symptom at onset and may develop at any site in the body but most commonly in the gum, skin, central nervous system (CNS) and soft tissue. There is controversy about the prognostic significance of extramedullary disease in AML. The present study examines the incidence, the biological features and prognostic significance of EMI at diagnosis in adult patients with AML. From January 1997 to December 2004, 213 untreated patients with de novo AML were studied. According to Grimwade et al, 14 patients were in the favorable-risk group, 159 in the intermediate-risk group, 25 in the poor risk group and in 15 the karyotype was not available. All patients had been treated with induction therapy according to the GIMEMA protocols including cytarabine, etoposide and idarubicin (15 pts), or mitoxantrone (15 pts) or daunorubicin (183 pts).

We recently found that about one-third of adult AML (60% of all AML with normal karyotype) display aberrant cytoplasmic expression of nucleophosmin (NPM) which is due to mutations occurring at the exon-12 of NPM gene (Falini B, et al., Cytoplasmic nucleophosmin in acute myelogenous leukemia with a normal karyotype..N Engl J Med2005; 352: 254–266). Hereby, we clarify the molecular mechanism underlying cytoplasmic NPM accumulation that yet remained to be elucidated. AML-associated mutated NPM alleles encode abnormal NPM proteins (25 mutants so far identified) which have acquired at the C-terminus a nuclear export signal-(NES) motif and lost at least one of tryptophan residues 288 and 290 which determine nucleolar localization. Both alterations are crucial for mutant NPM export from nucleus to cytoplasm. In fact, the cytoplasmic NPM accumulation is blocked by leptomycin-B and ratjadones which are specific inhibitors of exportin-1/CRM1, and by re-insertion of tryptophan residues 288 and 290, which respectively relocate NPM mutants in the nucleoplasm and nucleoli. Thus, for cytoplasmic accumulation of NPM to occur, the NES motif and tryptophan mutations must act in concert. Possibly, when NPM mutans enter the nucleus by virtue of their nuclear localization signals (NLS), their capability to bind nucleoli must be hindered at least partially to become a CRM-1 target. Specific antibodies anti-NPM mutant proteins showed that the mutants localized exclusively in the cytoplasm and recruited in that site the wild-type NPM protein which is physiologically located in the nucleoli. These findings suggest that the NPM mutants may interfere with the functions of wild-type NPM and possibly contribute to leukemogenesis. Immunostaining of 393 AML cases using anti-NPM monoclonal antibodies predicted the presence of NPM exon-12 mutations in all 191 NPM-cytoplasmic positive cases. This finding is consistent with the fact that, despite genomic heterogeneity, all NPM mutants contain a NES motif which, in the presence of altered tryptophans, promotes their rapid export from the nucleus to the cytoplasm. The immunohistochemical test is diagnostically relevant since it can be used as simple first-step procedure in molecular-genetic characterization of AML and as a surrogate for mutational analysis in selected cases. These findings are also clinically relevant since cytoplasmic NPM/NPM mutations are predictors of good response to induction therapy and favourable prognosis in AML with a normal karyotype.

Wild-type nucleophosmin (NPM) is a multifunctional protein shuttling between the nucleus and the cytoplasm. Chromosomal rearrangements leading to NPM fusion proteins occur in leukemias and lymphomas (e.g. with partners RARA, ALK). Recently, Falini et al. reported that 60% of acute myeloid leukemia (AML) patients with normal karyotype carry mutations at exon-12 of the NPM gene. This results in frame shifts that lead to alterations of the C-terminus of NPM resulting in the aberrant cytoplasmic localization of the mutated protein (NPMc+) (1). The effects of a mutationally altered protein on cellular functions like proliferation, differentiation or apoptosis, have often been revealed using immortalized cell lines that carry the mutation in question. Therefore, we screened a panel of 79 myeloid leukemia cell lines for presence of mutations - 4 bp insertions - at the exon-12 of the NPM gene. We performed polymerase chain reaction (PCR) analysis with fluorescent dye-labeled primers. For fragment size determination, the PCR products were mixed with dye-labeled size standards and separated by capillary electrophoresis. OCI-AML3 was the only cell line that expressed a signal in addition to and 4 bp larger than the wild-type NPM signal. Sequencing of the cloned NPM-mutated PCR product showed TCTG duplication at positions 956–959 of exon-12. This mutation was heterozygous and corresponded to the type that occurs in 77% of primary NPMc+ AMLs. OCI-AML3 cells have a hyperdiploid karyotype with 48(45–50)<2n>X/XY, +1, +5, +8, der(1)t(1;18)(p11;q11), i(5p),del(13)(q13q21), dup(17)(q21q25); sideline with r(Y)x1-2 and show the following immunoprofile: CD3−, CD4+, CD7−, CD8−, CD10−, CD13+, CD14−, CD15+, CD19−, CD30−, CD33−, CD34−, CD41+, CD42b−, CD68+, CD235a+, HLA-DR-. Especially the presence of myeloid markers and absence of CD34 is typical for NPMc+ cells (1). Furthermore, immunostaining with anti-NPM antibodies confirmed that the OCI-AML3 cells, like primary NPMc+ AML and in contrast to NPM wild-type cells, show cytoplasmic expression of NPM. Functional studies showed that the altered nucleo-cytoplasmic transport of NPM was nuclear export signalling-dependent and could be blocked by using the specific CRM1/exportin-1 inhibitor leptomycin B. In conclusion, cell line OCI-AML3 promises to be an important tool for studying the biological properties and response to new drugs of NPMc+ AML.

We recently found that about one-third of adult AML (60% of all AML with normal karyotype) display aberrant cytoplasmic expression of nucleophosmin (NPM) which is due to mutations occurring at the exon-12 of NPMgene (Falini B, et al., Cytoplasmic nucleophosmin in acute myelogenous leukemia with a normal karyotype.. N Engl J Med 2005; 352: 254–266). Hereby, we clarify the molecular mechanism underlying cytoplasmic NPM accumulation that yet remained to be elucidated. AML-associated mutated NPMalleles encode abnormal NPM proteins (25 mutants so far identified) which have acquired at the C-terminus a nuclear export signal-(NES) motif and lost at least one of tryptophan residues 288 and 290 which determine nucleolar localization. Both alterations are crucial for mutant NPM export from nucleus to cytoplasm. In fact, the cytoplasmic NPM accumulation is blocked by leptomycin-B and ratjadones which are specific inhibitors of exportin-1/CRM1, and by re-insertion of tryptophan residues 288 and 290, which respectively relocate NPM mutants in the nucleoplasm and nucleoli. Thus, for cytoplasmic accumulation of NPM to occur, the NES motif and tryptophan mutations must act in concert. Possibly, when NPM mutans enter the nucleus by virtue of their nuclear localization signals (NLS), their capability to bind nucleoli must be hindered at least partially to become a CRM-1 target. Specific antibodies anti-NPM mutant proteins showed that the mutants localized exclusively in the cytoplasm and recruited in that site the wild-type NPM protein which is physiologically located in the nucleoli. These findings suggest that the NPM mutants may interfere with the functions of wild-type NPM and possibly contribute to leukemogenesis. Immunostaining of 393 AML cases using anti-NPM monoclonal antibodies predicted the presence of NPMexon-12 mutations in all 191 NPM-cytoplasmic positive cases. This finding is consistent with the fact that, despite genomic heterogeneity, all NPM mutants contain a NES motif which, in the presence of altered tryptophans, promotes their rapid export from the nucleus to the cytoplasm. The immunohistochemical test is diagnostically relevant since it can be used as simple first-step procedure in molecular-genetic characterization of AML and as a surrogate for mutational analysis in selected cases. These findings are also clinically relevant since cytoplasmic NPM/NPM mutations are predictors of good response to induction therapy and favourable prognosis in AML with a normal karyotype.

Wild-type nucleophosmin (NPM) is a multifunctional protein shuttling between the nucleus and the cytoplasm. Chromosomal rearrangements leading to NPM fusion proteins occur in leukemias and lymphomas (e.g. with partners RARA, ALK). Recently, Falini et al. reported that 60% of acute myeloid leukemia (AML) patients with normal karyotype carry mutations at exon-12 of the NPMgene. This results in frame shifts that lead to alterations of the C-terminus of NPMresulting in the aberrant cytoplasmic localization of the mutated protein (NPMc+) (1). The effects of a mutationally altered protein on cellular functions like proliferation, differentiation or apoptosis, have often been revealed using immortalized cell lines that carry the mutation in question. Therefore, we screened a panel of 79 myeloid leukemia cell lines for presence of mutations - 4 bp insertions - at the exon-12 of the NPMgene. We performed polymerase chain reaction (PCR) analysis with fluorescent dye-labeled primers. For fragment size determination, the PCR products were mixed with dye-labeled size standards and separated by capillary electrophoresis. OCI-AML3 was the only cell line that expressed a signal in addition to and 4 bp larger than the wild-type NPMsignal. Sequencing of the cloned NPM-mutated PCR product showed TCTG duplication at positions 956–959 of exon-12. This mutation was heterozygous and corresponded to the type that occurs in 77% of primary NPMc+ AMLs. OCI-AML3 cells have a hyperdiploid karyotype with 48(45–50)<2n>X/XY, +1, +5, +8, der(1)t(1;18)(p11;q11), i(5p),del(13)(q13q21), dup(17)(q21q25); sideline with r(Y)x1-2 and show the following immunoprofile: CD3−, CD4+, CD7−, CD8−, CD10−, CD13+, CD14−, CD15+, CD19−, CD30−, CD33−, CD34−, CD41+, CD42b−, CD68+, CD235a+, HLA-DR-. Especially the presence of myeloid markers and absence of CD34 is typical for NPMc+ cells (1). Furthermore, immunostaining with anti-NPM antibodies confirmed that the OCI-AML3 cells, like primary NPMc+ AML and in contrast to NPM wild-type cells, show cytoplasmic expression of NPM. Functional studies showed that the altered nucleo-cytoplasmic transport of NPM was nuclear export signalling-dependent and could be blocked by using the specific CRM1/exportin-1 inhibitor leptomycin B. In conclusion, cell line OCI-AML3 promises to be an important tool for studying the biological properties and response to new drugs of NPMc+ AML.

Background. Proteomics can integrate hybridoma technology in discovering new antigens through the characterization of monoclonal antibodies (mAbs) of unknown specificity, that are generated when using whole cells and even purified known proteins as immunogens. Aim. To characterize, by means of a new mAb (B28p), a protein sharing an antigenic determinant with IRTA1, i.e. the unrelated immunogen used in the unforeseen generation of B28p. Methods/Results. Among ~1000 hybridomas from mice immunized with IRTA1, one producing an IgG1 mAb (B28p), cross-reactive with IRTA1, recognized also a 28 kDa cytoplasmic protein expressed strongly by all mature B cell subsets, with the highest levels in plasma cells (PC), and weakly by epithelial cells. This pattern clearly differs from that expected for IRTA1, a 70 kDa cell membrane receptor selectively expressed in MALT marginal zone B cells (Falini et al, Blood2003;102:3684). To identify the 28 kDa antigen, the proteome of a B28p+ B-NHL was resolved by 2D-PAGE, and tandem mass spectrometry analysis revealed the B28p-immunoreactive spot as human tumor protein D52 (TPD52), previously described to be expressed only in epithelial tissues. The specificity of B28p mAb for TPD52 was confirmed by immunostaining/immunoblotting TPD52-transfected cells and by observing an identical labeling pattern (mature B cells/PC and, less strongly, epithelial cells) upon immunohistology with a specfic anti-TPD52 polyclonal antibody. In routine tumor biopsies, TPD52 was expressed in all peripheral B-NHL subtypes (except some DLCLs) and most abundantly in multiple myeloma (MM). TPD52-staining proved to be a useful diagnostic tool in the quantification of bone marrow PC infiltration (thus helping in discriminating between MGUS and MM and in assessing minimal residual disease after therapy for MM), as well as in the evaluation of lymphomas associated with PC differentiation (including transplant-associated lymphomas, plasmablastic lymphomas of the oral cavity and primary effusion lymphomas). Notably, TPD52 was also expressed by a proportion of tumor cells in about 40% classical Hodgkin’s lymphomas, including cases misdiagnosed as ALK− ALCL with null phenotype. Unlike other B cell markers (PAX5,CD19,C79a,CD22,CD20), TPD52 represents the first example of a B cell protein whose expression increases during PC differentiation Intriguingly, in the Thiel myeloma cell line (similarly to what previously observed during zymogen secretion in pancreatic acinar cells), we found a strong and Ca+2-dependent co-immunoprecipitation of TPD52 with annexin VI, suggesting TPD52 up-regulation in PC may play a role in immunoglobulin-related secretory processes through interaction with annexin VI (which we also showed to be strongly expressed in PC). Conclusions. By combining proteomic and hybridoma technologies, we first identified the epithelium-associated TPD52 protein as a new B cell/plasma cell protein showing unique expression pattern, diagnostic value and, likely, biological importance.

Background.Proteomics can integrate hybridoma technology in discovering new antigens through the characterization of monoclonal antibodies (mAbs) of unknown specificity, that are generated when using whole cells and even purified known proteins as immunogens.

Translocation t(8;21)(q22;q22) is a common karyotypic abnormality detected in about 15% of Acute Myeloid Leukemia (AML) cases. The rearrangement results in fusion of the RUNX1 (also known as AML1) and CBFA2T1 (also known as ETO) genes generating a 5′RUNX1/3′CBFA2T1 transcriptionally active fusion gene on derivative chromosome 8. In 1 to 8.5% of AML cases insertions events generating a 5′RUNX1/3′CBFA2T1 fusion gene have been reported, whereas the occurrence of inversions accompanying the t(8;21) has never been observed. We report a screening of 82 AML cases bearing the RUNX1/CBFA2T1 rearrangement detected by RT-PCR; all cases were tested by Fluorescence In Situ Hybridization (FISH) with BAC and PAC clones specific for CBFA2T1 and RUNX1 genes. This analysis allowed us to reveal five cases with ins(21;8), one with ins(8;21), and two with a pericentric chromosome 8 inversion followed by a t(8;21) translocation. A detailed molecular cytogenetic characterization of breakpoints has been performed in all cases. FISH co-hybridization experiments with CBFA2T1 and RUNX1 probes revealed the presence of a functional fusion gene on the der(21) instead of the der(8) chromosome in five cases with ins(21;8); a single fusion signal on the der(8) chromosome was detected in the case with ins(8;21). The use of the same clones in FISH studies showed the presence of a single unexpected fusion signal on the 8p derivative chromosome in addition to faint CBFA2T1 and RUNX1 signals on the long arm of der(8) and der(21) chromosomes, respectively. These results suggested that a pericentric chromosome 8 inversion involving CBFA2T1 gene occurred and that the chromosome 21 was rearranged with the 8p derivative chromosome. Appropriate chromosome 21 and 8 BAC clones were employed to precisely define the size of inserted regions in cases with insertions and the breakpoint on the 8p derivative chromosome in cases showing pericentric chromosome 8 inversion. The insertion size turned out to be very heterogeneous, ranging from a minimum of 2.4 Mb to a maximum of 44 Mb. In both cases with chromosome 8 inversion, the CBFA2T1 gene represents the breakpoint at the chromosome 8 long arm whereas the 8p breakpoint showed different mapping positions in 8p21.3 and 8p21.1, respectively. Our results illustrate that (1) heterogeneous mechanisms can lead to the generation of the 5′RUNX1/3′CBFA2T1 chimeric gene; (2) molecular cytogenetic techniques may identify cryptic chromosomal changes, not detected by conventional cytogenetic analysis; (3) the crucial role of the 5′RUNX1/3′CBFA2T1 fusion gene in leukemogenesis does not depend on its location.

Translocation t(8;21)(q22;q22) is a common karyotypic abnormality detected in about 15% of Acute Myeloid Leukemia (AML) cases. The rearrangement results in fusion of the RUNX1(also known as AML1) and CBFA2T1(also known as ETO) genes generating a 5′RUNX1/3′CBFA2T1transcriptionally active fusion gene on derivative chromosome 8. In 1 to 8.5% of AML cases insertions events generating a 5′RUNX1/3′CBFA2T1fusion gene have been reported, whereas the occurrence of inversions accompanying the t(8;21) has never been observed. We report a screening of 82 AML cases bearing the RUNX1/CBFA2T1rearrangement detected by RT-PCR; all cases were tested by Fluorescence In Situ Hybridization (FISH) with BAC and PAC clones specific for CBFA2T1and RUNX1genes. This analysis allowed us to reveal five cases with ins(21;8), one with ins(8;21), and two with a pericentric chromosome 8 inversion followed by a t(8;21) translocation. A detailed molecular cytogenetic characterization of breakpoints has been performed in all cases.