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Myasthenia gravis (MG) is an autoimmune disease leading to varying degrees of skeletal muscle weakness. It is caused by specific antibodies directed against definite components in the postsynaptic membrane at the neuromuscular junction (NMJ), such as the acetylcholine receptor (AChR) and the muscle-specific kinase (MUSK) receptor. In clinical practice, MG patients may be classified into three main subgroups based on the occurrence of serum autoantibodies directed against AChR or MUSK receptor or antibody-negative. As the MG subgroups differ in terms of clinical characteristics, disease pathogenesis, prognosis, and response to therapies, they could benefit from targeted treatment as well as the detection of other possible disease biomarkers. We performed proteomics on plasma fractions enriched in low-abundance proteins to identify potential biomarkers according to different autoimmune responses. By this approach, we evidenced a significant reduction of vitronectin in MG patients compared to healthy controls, irrespective of the autoantibodies NMJ target. The obtained results were validated by mono- and two-dimensional Western blotting analysis. Vitronectin is a multifunctional glycoprotein involved in the regulation of several pathophysiological processes, including complement-dependent immune response, coagulation, fibrinolysis, pericellular proteolysis, cell attachment, and spreading. The pathophysiological significance of the reduction of plasma vitronectin in MG patients has yet to be fully elucidated. It could be related either to a possible deposition of vitronectin at NMJ to counteract the complement-mediated muscle damage at this level or to a parallel variation of this glycoprotein in the muscle extracellular matrix with secondary induced alteration in clustering of AChRs at NMJ, as it occurs with variation in concentrations of agrin, another extracellular matrix component. The clinical value of measuring plasma vitronectin has yet to be defined. According to present findings, significantly lower plasma values of this glycoprotein might be indicative of an impaired complement-dependent immune response.

BACKGROUND Factors that are predictive of carrying BRCA1 and BRCA2 germline mutations in patients with breast carcinoma are awaited widely. The genetically homogeneous Sardinian population may be useful for defining the role of such genetic alterations further through a clinical evaluation program. METHODS One hundred two of 659 patients with breast carcinoma (15.5%) who were collected consecutively had a family history of breast carcinoma and were screened for BRCA1/2 mutations by denaturing high-performance liquid chromatography and DNA sequencing. RESULTS Three deleterious germline BRCA1/2 mutations were detected in 15 of 102 families (14.7%), including 13 families (86.7%) with BRCA2 mutations and 2 families (13.3%) with BRCA1 mutations. A single variant, BRCA2-8765delAG, was the most recurrent mutation in the series and was found in 12 of 102 families (11.8%) and in 18 of 657 patients (2.7%). The average age at diagnosis was significantly younger in families with BRCA1/2 mutations (48.6 yrs) compared with the age of patients who had no detectable mutation (52.9 yrs; P = 0.039). Moreover, BRCA1/2 mutations were found at a significantly higher rate in families who had at least 1 member with ovarian carcinoma or male breast carcinoma (5 of 12 families; 41.7%) than in families without such an association (10 of 90 families; 11.1%; P = 0.003). CONCLUSIONS BRCA2 mutations were approximately 6 times more prevalent than BRCA1 mutations. A diagnosis of breast carcinoma before age 50 years, ovarian carcinoma, male breast carcinoma, and 3 affected generations all were associated significantly with BRCA1/2 mutations. Although the current findings provided further support for the hypothesis that additional breast carcinoma susceptibility genes remain to be identified, such indicators of the presence of BRCA1/2 mutations may be useful in counseling patients about undergoing genetic testing. Cancer 2005. © 2005 American Cancer Society.

Allelic deletions, which are suggestive for the presence of tumor suppressor genes, represent a common event in endometrial cancer (EC). Previous loss-of-heterozygosity studies for human chromosome 10q identified a candidate deletion interval at 10q25-q26, which we further narrowed to a 160-kb region at 10q26, bounded by markers D10S1236 and WIAF3299. Using a positional candidate approach, we identified three alternative transcripts of a novel human gene, CASC2 (cancer susceptibility candidate 2; formely C10orf5). One of such transcripts, CASC2a, encodes a short protein of 102 amino acids with no similarity to any other known gene product. Three (7%) CASC2a mutations were identified in tumor DNA from 44 EC patients. While c.-156G>T and c.22C>T (p.Pro8Ser) are sequence variants with unknown functional significance, c.84delA is a mutation with a truncation effect on the predicted protein (p. Asn28fsX50). Expression studies by real-time RT-PCR on several normal and tumor cells revealed that CASC2a mRNA is downregulated in cancer, suggesting that it may act as a potential tumor suppressor gene. The very low mutation rate seems to also indicate that inactivation of CASC2a might probably be due to mechanisms different from genetic alterations.

Summary Background The chromosome 9p21 and its CDKN locus, with the p16 tumour suppressor gene (CDKN2A), are recognized as the genomic regions involved in the pathogenesis of melanoma. Objectives To elucidate further the role of such regions during the different phases of melanocytic tumorigenesis. Methods Tissue sections from naevi, primary and metastatic melanomas were investigated by fluorescence in situ hybridization for allelic loss at the 9p21 chromosome and by immunochemistry for p16CDKN2A expression. Results Dysplastic naevi and primary or secondary melanomas were found to carry hemizygous deletions within the entire 9p21 region at similar frequencies (varying from 55% to 62%). Allelic deletion spanning the CDKN locus was observed at significantly increased rates moving from early (7%) to advanced (28%) primary melanomas and to secondary melanoma lesions (37%) (P = 0·018). Also, inactivation of the p16 gene (CDKN2A) was absent in naevi and present at steadily increasing rates moving from primary melanomas (7% early lesions to 17% advanced lesions) to melanoma metastases (62%) (P = 0·004). Conclusions Our findings indicate that, in a model of sequential accumulation of genetic alterations, 9p21 deletions may play a role in melanocytic transformation and tumour initiation whereas rearrangements at the CDKN locus, and p16 gene (CDKN2A) inactivation may contribute to tumour progression.

Background The BRCA2-8765delAG mutation was firstly described in breast cancer families from French-Canadian and Jewish-Yemenite populations; it was then reported as a founder mutation in Sardinian families. We evaluated both the prevalence of the BRCA2-8765delAG variant in Sardinia and the putative existence of a common ancestral origin through a haplotype analysis of breast cancer family members carrying such a mutation. Methods Eight polymorphic microsatellite markers (D13S1250, centromeric, to D13S267, telomeric) spanning the BRCA2 gene locus were used for the haplotype analysis. Screening for the 8765delAG mutation was performed by PCR-based amplification of BRCA2-exon 20, followed by automated sequencing. Results Among families with high recurrence of breast cancer (≥ 3 cases in first-degree relatives), those from North Sardinia shared the same haplotype whereas the families from French Canadian and Jewish-Yemenite populations presented distinct genetic assets at the BRCA2 locus. Screening for the BRCA2-8765delAG variant among unselected and consecutively-collected breast cancer patients originating from the entire Sardinia revealed that such a mutation is present in the northern part of the island only [9/648 (1.4%) among cases from North Sardinia versus 0/493 among cases from South Sardinia]. Conclusion The BRCA2-8765delAG has an independent origin in geographically and ethnically distinct populations, acting as a founder mutation in North but not in South Sardinia. Since BRCA2-8765delAG occurs within a triplet repeat sequence of AGAGAG, our study further confirmed the existence of a mutational hot-spot at this genomic position (additional genetic factors within each single population might be involved in generating such a mutation).

Factors predictive of carrying MLH1 and MSH2 germline mutations in patients with colorectal cancer (CRC) are as yet unknown. The aim of this population-based study, was to further define the role of MLH1/MSH2 mutations through an evaluation clinic program with 362 consecutive Sardinian CRC patients. Eight MLH1/MSH2 germline mutations were detected in 21 (6%) patients. Examining family cancer history, MLH1/MSH2 mutations were found in 14/48 (29.2%) probands from CRC families and, among them, in 10/13 (76.9%) families fulfilling the Amsterdam criteria. The patients with low familial recurrence (two CRCs in the family) presented a much lower frequency of MLH1/MSH2 mutations (2/55; 3.6%). Significantly higher rates of MLH1/MSH2 mutations were found in patients with age of onset 45 years (P=0.012) or with 3 affected family members (P=0.009). While no significant predictive value was found for the presence of endometrial cancer within the family, earlier age of diagnosis and/or familial CRC recurrence should be considered as strong predictors for the occurrence of MLH1/MSH2 mutations, and therefore useful in recommending CRC patients for genetic testing.

BACKGROUND Microsatellite instability (MSI) has been reported in endometrial carcinoma (EC) and in colorectal carcinoma (CRC), primarily as a result of defective DNA mismatch repair (MMR). The MMR gene hMLH1 commonly is inactivated in both EC and CRC. In the current study, epigenetic mechanisms involved in hMLH1 inactivation have been investigated to further elucidate the role of these mechanisms in the pathogenesis of EC and CRC. METHODS Polymerase chain reaction (PCR)-based microsatellite analysis performed on paraffin-embedded tissues was used to select 42 sporadic carcinomas (21 ECs and 21 CRCs) with MSI. Immunohistochemistry (IHC), using the anti-hMLH1 antibody, and mutation analysis, using denaturing high-performance liquid chromatography and automated sequencing, were performed on unstable carcinoma samples. Methylation analysis, using modified protocols for bisulfite treatment and methylation-specific PCR (MSP), was performed on DNA from archival tissue samples. RESULTS No MSI-positive tumor samples with normal hMLH1 immunostaining (n = 7) exhibited hMLH1 promoter methylation, whereas 8 of 35 unstable cases with loss of hMLH1 expression (23%) exhibited MSP amplification. Among analyzed cases, germ-line mutations of hMLH1 were found in 4 of 20 unmethylated samples (20%) and in 0 of 8 methylated samples. Bisulfite sequencing of amplification products from methylated samples demonstrated that almost all CpG dinucleotides within the hMLH1 promoter elements underwent methylation. CONCLUSIONS Although an MMR gene other than hMLH1 may be responsible for genetic instability in MSI-positive/IHC-positive tumors, the presence of MSP amplification and allelic deletions within the hMLH1 locus in subsets of MSI-positive/IHC-negative cases strongly suggests that hMLH1 promoter methylation may contribute to the inactivation of both hMLH1 alleles. Bisulfite analysis suggests that the mechanisms of hMLH1 silencing may depend on CpG density rather than site-specific methylation. Cancer 2003;98:1540–6. © 2003 American Cancer Society. DOI 10.1002/cncr.11651

Defective DNA mismatch repair and nonfunctional mechanisms controlling the proper progression of the cell cycle have been proposed as being responsible for the genomic instability and accumulation of karyotypic alterations in endometrial cancer (EC). To assess whether numerical chromosomal anomalies (aneuploidy) and microsatellite instability (MSI) might be representative of distinctive tumour behaviour, paraffin-embedded tissue samples from 86 patients with sporadic EC were evaluated by both fluorescence in situ hybridisation (FISH) and microsatellite analysis, using free nuclei and genomic DNAs (respectively). Approximately one-third of the tumours analysed (24/74; 32%) exhibited MSI, whereas 38/86 (44%) of the EC samples displayed aneuploidy. The majority of the unstable cases (15/24; 63%) were from advanced-stage patients. Conversely, 23 (61%) out of the 38 tumours with aneuploidy were from early-stage patients. No apparent correlation was found between MSI and aneuploidy, whereas the immunohistochemical (IHC) analysis revealed that inactivation of the MLH1 mismatch repair gene may be involved in the majority of the MSI+ sporadic ECs. No genetic or cytogenetic alteration analysed here seems to add any significant predictive value to the stage of disease. © 2002 Elsevier Science Ltd. All rights reserved.

Expression of Bcl-2 protein has been demonstrated to reduce the apoptotic response to cytotoxic chemotherapy, and induction of apoptosis may become one of the main molecular targets in the treatment of melanoma (which indeed presents a well-recognized high resistance to conventional anticancer therapies) [1]. In recent past years, addition of oblimersen (G3139; Genta International Inc., NJ), an antisense oligonucleotide downregulating Bcl-2 expression, to a dacarbazine-based chemotherapy for the treatment of advanced melanoma has increased tumor-cell apoptosis in a phase I–II study [2] and improved overall survival in patients with normal serum lactate dehydrogenase in a randomized phase III clinical trial [3]. However, questions arise over the cause–effect relationship between the antiproliferative activity of oblimersen and somatic expression levels of the Bcl-2 protein. On this regard, our preliminary evidence indicated that the effect of oblimersen on proliferation of melanoma cells seems to be independent on Bcl-2 expression. In particular, several melanoma cell lines established as short term cultures from primary tumors of melanoma patients (after obtaining their informed consent) were treated with oblimersen and the cytotoxic response, in terms of cell growth reduction, was investigated. In our experience, the poorest antiproliferative activity of oblimersen was surprisingly detected in melanoma cell lines with the highest Bcl-2 expression levels; conversely, inhibition of cell growth was observed in cultured melanomas which did not express any detectable level of the Bcl-2 protein (Figure 1). Putting together ours with the published findings [2, 3], one could speculate that oblimersen, despite its putative high specificity (it is a phosphorothioate oligonucleotide recognizing the initiation codon region of the Bcl-2 mRNA), may induce a Bcl-2-independent cellular apoptosis and, thus, target different molecular pathways. Figure 1. Effect of oblimersen on growth of human melanoma cell lines. (A) Seven melanoma cell lines were cultured in presence of RPMI medium alone (negative control), 250 μM of oblimersen, and 10 μM etoposide (cytotoxic agent as positive control) ... Analogously, majority of the recently developed tyrosine-kinase inhibitors, which were firstly isolated as active on specific molecular effectors, indeed target several types of cancer cell receptors and inhibit multiple molecular mechanisms [4]. Nevertheless, resistance to apoptosis through the Bcl-2 pathway is yet to be clarified and defective apoptotic response to anticancer agents may be caused by mechanisms other than Bcl-2 expression (silencing of Bcl-2 gene by highly specific interfering RNA has been demonstrated to fail in increasing the sensitiveness to a variety of cytotoxic agents in melanoma cells [5]). In the light of recent advances, it appears evident that targeting a single component within the multiple signaling pathways involved in development and progression of human cancers is unlikely to yield significant antitumor responses. Therefore, further clarification of the main mechanisms implicated into the control of the apoptotic machinery (i.e., activation of other effectors of the apoptosis cascade and/or release of mitochondrial apoptogenic proteins) could permit to select the subsets of patients who would be expected to be more likely to respond to the anti-Bcl-2 treatment. More in general, making correlations between functionally associated molecular signatures and clinical response to therapy may avoid that targeted treatments in patients carrying one specific molecular alteration achieve different clinical outcomes due to the coexistence of additional alterations in alternative pathways. For sure, the introduction of targeted therapies is generating more questions than answers.

20028 Characterization of the different molecular mechanisms involved in development and progression of melanoma (referred to as melanomagenesis) could represent a potential tool to identify the mo...

3629 Background: Fanconi Anemia (FA) is an autosomal recessive disease marked by congenital defects, bone marrow failure, and high incidence of leukemia and solid tumors. Eight FA associated genes have been cloned, and their products are thought to function in an integrated pathway which includes BRCA genes and maintains genomic stability. A molecular mechanism involved in the development and progression of some human malignancies, including colorectal cancer, is represented by a defective replication fidelity. Here we tested the role of the main FA genes in colorectal cancer (CRC). Methods: One hundred consecutively-collected patients with histologically-proven diagnosis of CRC and no mutation in the main mismatch repair genes (MLH1 and MSH2) were included into the study. Genomics DNA was screened using DHPLC for FANC-C/G/E/F genes and using MPLA for FANC-A/D2 genes. All PCR products with abnormal DHPLC profiles were sequenced on an automated sequencer. For 28 cases, tumor tissue samples were also analyzed. To date, total RNA was isolated from paired normal and tumor samples of 12 CRC patients. Gene expression was quantified by real-time RT-PCR using the Taqman approach. Results: At germline level, 2 cases presented FANC-C sequence variations (Asp267Ser, Val449Ser) and 5 cases showed a exon 26 deletion in FANC-A as detected by MLPA analysis. Among the 28 tumor samples available from patients negative for mutations in germline DNA, 2 (7%) cases presented a FANC-E mutation (Ala552Thr). Moreover, one of such somatic samples presented a BRCA2–8765delAG mutation (BRCA2 is also recognized as FANC-D1 gene). Assuming as significant difference in gene expression the presence of a variation of more than 50% in mRNA levels between normal and corresponding tumor samples, all tested FA genes (FANC-C/G/E/F) were found overexpressed in 5/12 (42%) tumor samples. Conclusions: Although preliminary, our findings seem to identify a subset of CRC patients with alterations in the FA/BRCA pathway which is required for the activation of DNA repair. Ongoing molecular analyses will better clarify the real frequency of each alteration in FA genes and their relationship with the histological and/or clinical features in colorectal cancer. No significant financial relationships to disclose.