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Purpose: Inhibitors of Bruton's tyrosine kinase (BTKi) and PI3K (PI3Ki) have significantly improved therapy of chronic lymphocytic leukemia (CLL). However, the emergence of resistance to BTKi has introduced an unmet therapeutic need. Hence, we sought evidence for essential roles of PI3K-δi and PI3K-γi in treatment-naïve and BTKi-refractory CLL. Experimental Design: Responses to PI3K-δi, PI3K-γi, and the dual-inhibitor duvelisib in each B, T, and myeloid cell compartments of CLL were studied in vitro, and in a xenograft mouse model using primary cells from treatment-naïve and ibrutinib-resistant patients, and finally, in a patient with ibrutinib-resistant CLL treated with duvelisib. Results: We demonstrate the essential roles of PI3K-δ for CLL B-cell survival and migration, of PI3K-γ for T-cell migration and macrophage polarization, and of dual inhibition of PI3K-δ,γ for efficacious reduction of leukemia burden. We also show that samples from patients whose disease progressed on ibrutinib were responsive to duvelisib therapy in a xenograft model, irrespective of BTK mutations. In support of this, we report a patient with ibrutinib-resistant CLL, bearing a clone with BTK and PLCγ2 mutations, who responded immediately to single-agent duvelisib with redistribution lymphocytosis followed by a partial clinical remission associated with modulation of T and myeloid cells. Conclusions: Our data define the mechanism of action whereby dual inhibition of PI3K-δ,γ affects CLL B-cell numbers and T and myeloid cell pro-leukemia functions and support the use of duvelisib as a valuable approach for therapeutic interventions, including for patients refractory to BTKi.

Effects of inhibition of PI3K isoforms on CLL-cell proliferation, survival, and migration.

Purpose:Inhibitors of Bruton's tyrosine kinase (BTKi) and PI3K (PI3Ki) have significantly improved therapy of chronic lymphocytic leukemia (CLL). However, the emergence of resistance to BTKi has introduced an unmet therapeutic need. Hence, we sought evidence for essential roles of PI3K-δi and PI3K-γi in treatment-naïve and BTKi-refractory CLL.Experimental Design:Responses to PI3K-δi, PI3K-γi, and the dual-inhibitor duvelisib in each B, T, and myeloid cell compartments of CLL were studied in vitro, and in a xenograft mouse model using primary cells from treatment-naïve and ibrutinib-resistant patients, and finally, in a patient with ibrutinib-resistant CLL treated with duvelisib.Results:We demonstrate the essential roles of PI3K-δ for CLL B-cell survival and migration, of PI3K-γ for T-cell migration and macrophage polarization, and of dual inhibition of PI3K-δ,γ for efficacious reduction of leukemia burden. We also show that samples from patients whose disease progressed on ibrutinib were responsive to duvelisib therapy in a xenograft model, irrespective of BTK mutations. In support of this, we report a patient with ibrutinib-resistant CLL, bearing a clone with BTK and PLCγ2 mutations, who responded immediately to single-agent duvelisib with redistribution lymphocytosis followed by a partial clinical remission associated with modulation of T and myeloid cells.Conclusions:Our data define the mechanism of action whereby dual inhibition of PI3K-δ,γ affects CLL B-cell numbers and T and myeloid cell pro-leukemia functions and support the use of duvelisib as a valuable approach for therapeutic interventions, including for patients refractory to BTKi.

IC50 values of PI3K isoform inhibitors used. Duvelisib5, IPI-3063 (PI3K-d inhibitor)5, IPI-549 (PI3K-g inhibitor used in vitro)50, IPI-5243 (PI3K-g inhibitor used in vivo).

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mp3 file (7.8 MB). In the January edition of the Cancer Discovery podcast, Executive Editor Mark Landis talks with David Weinstock about his paper, in which analysis of a donor-recipient pair of sisters with follicular lymphoma reveals the time-course of somatic mutations acquired during lymphomagenesis.

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Supplementary Data from MLL-Rearranged B Lymphoblastic Leukemias Selectively Express the Immunoregulatory Carbohydrate-Binding Protein Galectin-1

Purpose: Asparaginase (ASNase) is a standard and critical component in the therapy of childhood acute lymphoblastic leukemia (ALL), but it is also associated with several toxicities.Experimental design: We recently reported the results of an association study between ASNase pathway genes and event-free survival (EFS) in childhood patients with ALL. The same polymorphisms were interrogated here in relation to allergies, pancreatitis, and thrombotic events following treatment with E. coli ASNase.Results: Among patients of the discovery group, allergies, and pancreatitis were more frequent in individuals who are homozygous for the triple-repeat allele (3R) of the asparagine synthetase (ASNS) gene, resulting in remarkably higher risk of these toxicities associated with 3R3R genotype [OR for allergies, 14.6; 95% confidence interval (CI), 3.6–58.7; P < 0.0005 and OR for pancreatitis, 8.6; 95% CI, 2.0–37.3; P = 0.01]. In contrast, the ASNS haplotype *1 harboring double-repeat (2R) allele had protective effect against these adverse reactions (P ≤ 0.01). The same haplotype was previously reported to confer reduction in EFS. The risk effect of 3R3R genotype was not replicated in the validation cohort, whereas the protective effect of haplotype *1 against allergies was maintained (P ≤ 0.002). Analysis with additional polymorphisms in ASNS locus in lymphoblastoid cell lines showed that haplotype *1 is diversified in several subtypes of which one was associated with reduced in vitro sensitivity to ASNase (rs10486009, P = 0.01) possibly explaining an association seen in clinical setting.Conclusions: This finding might have implication for treatment individualization in ALL and other cancers using asparagine depletion strategies. Clin Cancer Res; 21(2); 329–34. ©2014 AACR.See related commentary by Avramis, p. 230

Purpose: Patients with mixed lineage leukemia (MLL)–rearranged B-lymphoblastic leukemias (B-ALL) have an unfavorable prognosis and require intensified treatment. Multiple MLL fusion partners have been identified, complicating the diagnostic evaluation of MLL rearrangements. We analyzed molecular markers of MLL rearrangement for use in rapid diagnostic assays and found the immunomodulatory protein, Galectin-1 (Gal-1), to be selectively expressed in MLL-rearranged B-ALL.Experimental Design: Transcriptional profiling of ALL subtypes revealed selective overexpression of Gal-1 in MLL-rearranged ALLs. For this reason, we analyzed Gal-1 protein expression in MLL-germline and MLL-rearranged adult and infant pediatric B-ALLs and cell lines by immunoblotting, immunohistochemistry, and intracellular flow cytometry of viable tumor cell suspensions. Because deregulated gene expression in MLL-rearranged leukemias may be related to the altered histone methyltransferase activity of the MLL fusion protein complex, we also analyzed histone H3 lysine 79 (H3K79) dimethylation in the LGALS1 promoter region using chromatin immunoprecipitation.Results: Gal-1 transcripts were significantly more abundant in MLL-rearranged B-ALLs. All 32 primary MLL-rearranged B-ALLs exhibited abundant Gal-1 immunostaining, regardless of the translocation partner, whereas only 2 of 81 germline-MLL B-ALLs expressed Gal-1. In addition, Gal-1 was selectively detected in newly diagnosed MLL-rearranged B-ALLs by intracellular flow cytometry. The LGALS1 promoter H3K79 was significantly hypermethylated in MLL-rearranged B-ALLs compared with MLL-germline B-ALLs and normal pre-B cells.Conclusion: In B-ALL, Gal-1 is a highly sensitive and specific biomarker of MLL rearrangement that is likely induced by a MLL-dependent epigenetic modification. Clin Cancer Res; 16(7); 2122–30. ©2010 AACR.

PDF file, 871K, S1 Chromogenic staining (DAB, brown) of paraffin-embedded DLBCL cell lines DHL4, and Toledo, untreated and BCR crosslinked, with anti-pLYN (Y396), anti-pSYK (Y323), and anti-pBTK (Y551); S2 Schematic illustration of Tissuequest analysis workflow. Individual cells are first identified by finding the nuclei (DAPI); S3 Qualitative Western blot of whole cell lysates for untreated (BCR-) and crosslinked (BCR+) cell lines; S4 S4 Chromogenic staining (DAB, brown) of two paraffin-embedded patient DLBCL specimens with anti-pLYN (Y396), anti-pSYK (Y323), and anti-pBTK (Y551); S5 (A) Schematic illustration of Tissuequest workflow extended to subcellular localization of FOXO1. In this example there are 83% of all cells that are positive for FOXO1 and 67% of the cells show cytoplasmic FOXO1 staining (67%). The ratio of these percentages is used to calculate the Fcyt score; S6 (A) Chromogenic staining (DAB, brown) of paraffin-embedded DLBCL cell lines DHL4, and Toledo, untreated and BCR crosslinked, with anti- FOXO1; S7 (A) IHC staining of paraffin-embedded DLBCL cell lines U2932, DHL6 and Toledo, untreated and crosslinked, with anti-pAKTsub (red) and DAPI (blue); S8 (A) Comparison of immunofluorescent images evaluated by an expert using a 3-tier system (0 - negative, 1 - weak positive, 2 - strong positive); S9 Comparison of FOXO1 cytoplasmic localization and BCR signaling in primary DLBCL tumors.

PDF file - 462K, Table S1: pLYN, pSYK and pBTK levels in DLBCL cell lines; S2 DLBCL cell line classification

PDF file - 80K, Polymorphisms in ATF5, ASNS and ASS1 genes analyzed in the relation to ASNase related complications.

Supplementary Table 1 and 2 - PDF file 68K, Supplementary Table 1. Identity of tagSNPs, details of PCR and ASO hybridization Supplementary Table 2. Identity of polymorphisms genotyped only in controls

Purpose: B-cell receptor (BCR)–mediated signaling is important in the pathogenesis of a subset of diffuse large B-cell lymphomas (DLBCL) and the BCR-associated kinases SYK and BTK have recently emerged as potential therapeutic targets. We sought to identify a signature of activated BCR signaling in DLBCL to aid the identification of tumors that may be most likely to respond to BCR-pathway inhibition.Experimental Design: We applied quantitative immunofluorescence (qIF) using antibodies to phosphorylated forms of proximal BCR signaling kinases LYN, SYK, and BTK and antibody to BCR-associated transcription factor FOXO1 on BCR-cross-linked formalin-fixed paraffin-embedded (FFPE) DLBCL cell lines as a model system and on two clinical cohorts of FFPE DLBCL specimens (n = 154).Results: A robust signature of active BCR signaling was identified and validated in BCR-cross-linked DLBCL cell lines and in 71/154 (46%) of the primary DLBCL patient specimens. Further analysis of the primary biopsy samples revealed increased nuclear exclusion of FOXO1 among DLBCL with qIF evidence of active BCR signaling compared with those without (P = 0.004). Nuclear exclusion of FOXO1 was also detected in a subset of DLBCL without evidence of proximal BCR signaling suggesting that alternative mechanisms for PI3K/AKT activation may mediate FOXO1 subcellular localization in these cases.Conclusion: This study establishes the feasibility of detecting BCR activation in primary FFPE biopsy specimens of DLBCL. It lays a foundation for future dissection of signal transduction networks in DLBCL and provides a potential platform for evaluating individual tumors in patients receiving novel therapies targeting the BCR pathway. Clin Cancer Res; 18(22); 6122–35. ©2012 AACR.

Purpose: Corticosteroids induce apoptosis in the malignant lymphoid cells and are critical component of combination therapy for acute lymphoblastic leukemia (ALL). Several genome-wide microarray studies showed major implication of proapoptotic Bim in mediating corticosteroid-related resistance in leukemia cells.Experimental Design: We investigated Bim gene polymorphisms and their association with childhood ALL outcome, and the mechanism underlying the observed finding.Results: Lower overall survival (OS) was associated with BimC29201T located in Bcl-2 homology 3 (BH3) domain (P = 0.01). An association remained significant in multivariate model (P = 0.007), was more apparent in high-risk patients (P = 0.004) and patients treated with dexamethasone (P = 0.009), and was subsequently confirmed in the replication patient cohort (P = 0.03). RNA analysis revealed that C29201T affects generation of γ isoforms (γ1) that lack proapoptotic BH3 domain. The phenotypic effect was minor suggesting the influence of additional factors that may act in conjunction with Bim genotype. Combined analysis with Mcl gene polymorphism (G-486T) revealed profound reduction in OS in individuals with both risk genotypes (P < 0.0005 in discovery and P = 0.002 in replication cohort) and particularly in high-risk patients (P ≤ 0.008).Conclusions: Increased expression of prosurvival Mcl1 and presence of Bim isoforms lacking proapoptotic function might explain marked reduction of OS in a disease and dose-dependent manner in ALL patients carrying Bim- and Mcl1-risk genotypes. Clin Cancer Res; 19(18); 5240–9. ©2013 AACR.

Supplementary Figure 3 from Proteasome Inhibition Causes Regression of Leukemia and Abrogates BCR-ABL–Induced Evasion of Apoptosis in Part through Regulation of Forkhead Tumor Suppressors

Supplementary Figure 10 from Proteasome Inhibition Causes Regression of Leukemia and Abrogates BCR-ABL–Induced Evasion of Apoptosis in Part through Regulation of Forkhead Tumor Suppressors

Galectins, a family of glycan-binding proteins, influence tumor progression by modulating interactions between tumor, endothelial, stromal, and immune cells. Despite considerable progress in identifying the roles of individual galectins in tumor biology, an integrated portrait of the galectin network in different tumor microenvironments is still missing. We undertook this study to analyze the “galectin signature” of the human prostate cancer microenvironment with the overarching goal of selecting novel-molecular targets for prognostic and therapeutic purposes. In examining androgen-responsive and castration-resistant prostate cancer cells and primary tumors representing different stages of the disease, we found that galectin-1 (Gal-1) was the most abundantly expressed galectin in prostate cancer tissue and was markedly upregulated during disease progression. In contrast, all other galectins were expressed at lower levels: Gal-3, -4, -9, and -12 were downregulated during disease evolution, whereas expression of Gal-8 was unchanged. Given the prominent regulation of Gal-1 during prostate cancer progression and its predominant localization at the tumor-vascular interface, we analyzed the potential role of this endogenous lectin in prostate cancer angiogenesis. In human prostate cancer tissue arrays, Gal-1 expression correlated with the presence of blood vessels, particularly in advanced stages of the disease. Silencing Gal-1 in prostate cancer cells reduced tumor vascularization without altering expression of other angiogenesis-related genes. Collectively, our findings identify a dynamically regulated “galectin-specific signature” that accompanies disease evolution in prostate cancer, and they highlight a major role for Gal-1 as a tractable target for antiangiogenic therapy in advanced stages of the disease. Cancer Res; 73(1); 86–96. ©2012 AACR.

Supplementary Figure 4 from Proteasome Inhibition Causes Regression of Leukemia and Abrogates BCR-ABL–Induced Evasion of Apoptosis in Part through Regulation of Forkhead Tumor Suppressors

Supplementary Figure 5 from Proteasome Inhibition Causes Regression of Leukemia and Abrogates BCR-ABL–Induced Evasion of Apoptosis in Part through Regulation of Forkhead Tumor Suppressors

Supplementary Table 1 from Serologic Markers of Effective Tumor Immunity against Chronic Lymphocytic Leukemia Include Nonmutated B-Cell Antigens

Supplementary Figure 8 from Proteasome Inhibition Causes Regression of Leukemia and Abrogates BCR-ABL–Induced Evasion of Apoptosis in Part through Regulation of Forkhead Tumor Suppressors

PDF file - 88K, Table S1. Primers used to delineate the 'galectin signature' of prostate cancer cells Table S2. Primers used to determine angiogenesis-related genes

Supplementary Methods from Proteasome Inhibition Causes Regression of Leukemia and Abrogates BCR-ABL–Induced Evasion of Apoptosis in Part through Regulation of Forkhead Tumor Suppressors

Supplementary Figure 9 from Proteasome Inhibition Causes Regression of Leukemia and Abrogates BCR-ABL–Induced Evasion of Apoptosis in Part through Regulation of Forkhead Tumor Suppressors

Recent studies suggest that NOTCH signaling can promote epithelial-mesenchymal transitions and augment signaling through AKT, an important growth and survival pathway in epithelial cells and prostate cancer in particular. Here we show that JAGGED1, a NOTCH receptor ligand, is significantly more highly expressed in metastatic prostate cancer as compared with localized prostate cancer or benign prostatic tissues, based on immunohistochemical analysis of JAGGED1 expression in human tumor samples from 154 men. Furthermore, high JAGGED1 expression in a subset of clinically localized tumors was significantly associated with recurrence, independent of other clinical parameters. These findings support a model in which dysregulation of JAGGED1 protein levels plays a role in prostate cancer progression and metastasis and suggest that JAGGED1 may be a useful marker in distinguishing indolent and aggressive prostate cancers.

Supplementary Figure 7 from Proteasome Inhibition Causes Regression of Leukemia and Abrogates BCR-ABL–Induced Evasion of Apoptosis in Part through Regulation of Forkhead Tumor Suppressors

Supplementary Figure 6 from Proteasome Inhibition Causes Regression of Leukemia and Abrogates BCR-ABL–Induced Evasion of Apoptosis in Part through Regulation of Forkhead Tumor Suppressors

Supplementary Figure 2 from Serologic Markers of Effective Tumor Immunity against Chronic Lymphocytic Leukemia Include Nonmutated B-Cell Antigens

PDF file - 123K, Figure S1. Gal-1 mRNA expression and PSA mRNA expression in hormone-responsive (HR) and castration-resistant (CR) LNCaP cells Figure S2: Immunoreactivity of anti-galectin antibodies

Supplementary Figure 2 from Proteasome Inhibition Causes Regression of Leukemia and Abrogates BCR-ABL–Induced Evasion of Apoptosis in Part through Regulation of Forkhead Tumor Suppressors

Supplementary Figure Legends 1-10 from Proteasome Inhibition Causes Regression of Leukemia and Abrogates BCR-ABL–Induced Evasion of Apoptosis in Part through Regulation of Forkhead Tumor Suppressors

Supplementary Figure 1 from Serologic Markers of Effective Tumor Immunity against Chronic Lymphocytic Leukemia Include Nonmutated B-Cell Antigens

Supplementary Figure 1 from JAGGED1 Expression Is Associated with Prostate Cancer Metastasis and Recurrence

Duvelisib (IPI-145), a first-in-class, oral, dual PI3K-δ,γ inhibitor, has been approved by the FDA for the treatment of patients with chronic lymphocytic leukemia (CLL), small lymphocytic and follicular lymphoma. Duvelisib potently inhibits PI3K-δ and PI3K-γ, thereby offering a novel therapeutic approach. Here we aimed to understand how duvelisib targets CLL cells and the tumor microenvironment (TME) and hence how it affects CLL, even with BTK-resistant disease. We first assessed the distinct contributions of PI3K-δ and PI3K-γ on CLL cell survival, proliferation, and migration in vitro by using PI3K-δ (PI3K-δi) or PI3K-γ (PI3K-γi) specific inhibitors in addition to duvelisib. We found a significant reduction in viable CLL cells after exposure to PI3K-δi and duvelisib. By measuring Ki67 and p-AKT levels, we found duvelisib and PI3K-δi more potently block CLL cell proliferation than PI3K-γi. PI3K-δi and duvelisib also significantly reduced the migration of CLL B cells into the spleen relative to control. In contrast, PI3K-γi inhibited T cell not B cell homing in vitro and in vivo. We then investigated the impact of single versus dual inhibitory agents on myeloid cells. Tumor-associated macrophages (TAMs) of the “M2 phenotype” contribute to a pro-tumor TME by preventing the induction of T cell mediated anti-tumor immunity. We expanded murine bone marrow derived monocytes and then polarized them to M2 macrophages, in the absence or presence of PI3Ki. At 100nM, PI3K-γi, but not PI3K-δi, significantly inhibited M2 polarization. Duvelisib significantly reduced Arg1 expression at doses equal to or above 10nM. While co-culturing leukemic B cells with M2-polarized murine macrophages increased CLL-cell survival, addition of duvelisib to such co-cultures significantly reduced CLL cell survival. Altogether, duvelisib sensitizes primary CLL cells to apoptosis and abrogates M2 cell-mediated CLL-cell survival. Finally, in a patient-derived xenograft mouse model (PDX), we demonstrated the essential roles of PI3K-δ and PI3K-γ in the CLL TME. Specifically, we found a more efficacious inhibition in CLL cell burden by dual inhibition of PI3K-δ,γ. Also, samples from patients whose disease progressed on ibrutinib were responsive to duvelisib therapy in PDX, irrespective of BTK mutations. In support of this, we identified an ibrutinib resistant CLL patient, with a clone exhibiting BTK and PLCγ2 mutations who responded immediately to single agent duvelisib with redistribution lymphocytosis followed by a partial clinical remission associated with subsequent modulation of T and myeloid cells. In conclusion, our data define the mechanism of action whereby dual inhibition of PI3K-δ,γ affects CLL B cell numbers and T and myeloid cell pro-leukemia functions, supporting the use of duvelisib as a potentially valuable therapeutic intervention, including for patients refractory to BTKi. Citation Format: Shih-Shih Chen, Jacqueline C. Barrientos, Gerardo Ferrer, Priyadarshini Ravichandran, Michael Ibrahim, Yasmine Kieso, Jeffery L. Kutok, Marisa Peluso, Sujata Sharma, David T. Weaver, Jonathan A. Pachter, Kanti R. Rai, Nicholas Chiorazzi. Duvelisib eliminates CLL B Cells, impairs CLL-supporting cells, and overcomes ibrutinib resistance in a patient-derived xenograft model. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 4933.

Aim: To evaluate top-ranking genes identified through genome-wide association studies for an association with corticosteroid-related osteonecrosis in children with acute lymphoblastic leukemia (ALL) who received Dana–Farber Cancer Institute treatment protocols. Patients & methods: Lead SNPs from these studies, as well as other variants in the same genes, pooled from whole exome sequencing data, were analyzed for an association with osteonecrosis in childhood ALL patients from Quebec cohort. Top-ranking variants were verified in the replication patient group. Results: The analyses of variants in the ACP1-SH3YL1 locus derived from whole exome sequencing data showed an association of several correlated SNPs (rs11553746, rs2290911, rs7595075, rs2306060 and rs79716074). The rs79716074 defines *B haplotype of the APC1 gene, which is well known for its functional role. Conclusion: This study confirms implication of the ACP1 gene in the treatment-related osteonecrosis in childhood ALL and identifies novel, potentially causal variant of this complication.

SETD2 is the only known histone methyltransferase (HMT) capable of catalyzing H3K36 trimethylation (H3K36me3). It plays a critical role in several biological processes such as DNA damage repair and B cell development. Dysregulation in H3K36 methylation can occur in B cell malignancies, including multiple myeloma (MM) and diffuse large B cell lymphoma (DLBCL), often as a result of mutational events incurred during normal B cell development. For example, 15%-20% of MM patients harbor the high risk (4;14) chromosomal translocation (t), resulting in high expression of the multiple myeloma SET domain (MMSET) gene. MMSET (also known as NSD2) is an HMT that catalyzes H3K36me1 and H3K36me2 formation, which leads to increased levels of H3K36me2 in t(4;14) MM patients. Because H3K36me2 is the substrate of SETD2, we hypothesized that inhibiting SETD2 could target the underlying oncogenic mechanism driven by the dysregulated H3K36 methylation from MMSET overexpression in t(4;14) MM patients, and would establish proof of concept in this and other B cell malignancies (e.g. DLBCL) that may demonstrate dysregulated H3K36me3 or a dependency on SETD2. In this presentation, we will describe the discovery and structure of our clinical candidate EZM0414, a first-in-class, potent, selective, orally bioavailable small molecule inhibitor of the enzymatic activity of SETD2; robust anti-tumor effects of SETD2 inhibition with EZM0414 in MM (including t(4;14) MM) and DLBCL preclinical studies; and the outline of the ongoing first-in-human Ph1/1b open-label, multicenter study of EZM0414 in patients with relapsed/refractory MM or DLBCL. Citation Format: Jeffery L. Kutok. Discovery and First Structural Disclosure of EZM0414: A potent and selective small molecule inhibitor of the histone methyltransferase SETD2 [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr ND12.