Combined epigenetic and immunotherapy for blastic and classical mantle cell lymphoma.

Classical MCL (cMCL) constitutes 6-8% of all B cell NHL. Despite recent advances, MCL is incurable except with allogeneic stem cell transplant. Blastic mantle cell lymphoma (bMCL) is a rarer subtype of cMCL associated with an aggressive clinical course and poor treatment response, frequent relapse and poor outcomes. We treated 13 bMCL patients with combined epigenetic and immunotherapy treatment consisting of vorinostat, cladribine and rituximab (SCR). We report an increased OS greater than 40 months with several patients maintaining durable remissions without relapse for longer than 5 years. This is remarkably better then current treatment regimens which in bMCL range from 14.5-24 months with conventional chemotherapy regimens. We demonstrate that the G/A870 CCND1 polymorphism is predictive of blastic disease, nuclear localization of cyclinD1 and response to SCR therapy. The major resistance mechanisms to SCR therapy are loss of CD20 expression and evasion of treatment by sanctuary in the CNS. These data indicate that administration of epigenetic agents improves efficacy of anti-CD20 immunotherapies. This approach is promising in the treatment of MCL and potentially other previously treatment refractory cancers.

Mantle cell lymphoma management trends and novel agents: where are we going?

The heterogeneity in disease pathology, the unpredictability in disease prognosis, and the variability in response to therapy make mantle cell lymphoma (MCL) a focus of novel therapeutic development. MCL is characterized by dysregulated expression of cyclin D1 through a chromosome t(11;14) translocation. MCL international prognostic index (MIPI), ki-67 proliferation index, and TP53 mutation status are currently utilized for prognostication. With advances in pharmacokinetic analysis and drug discovery, treatment strategy has evolved from chemotherapy to combination of targeted, epigenetic, and immune therapies. In this review, we discuss investigational and newly approved treatment approaches. In a short time, the US Food and Drug Administration (FDA) has approved five agents for the treatment of MCL: lenalidomide, an immunomodulatory agent; bortezomib, a proteasome inhibitor; and ibrutinib, acalabrutinib, and zanubrutinib, all Bruton kinase inhibitors. Epigenetic agents (e.g. cladribine and vorinostat), mammalian target of rapamycin (mTOR) inhibitors (e.g. temsirolimus and everolimus), and monoclonal antibodies and/or antibody-drug conjugates (e.g. obinutuzumab, polatuzumab, and ublituximab) are promising therapeutic agents currently under clinical trial investigation. Most recently, chimeric antigen receptor (CAR)-T cell therapy and bispecific T-cell engager (BiTE) therapy even open a new venue for MCL treatment. However, due to its intricate pathology nature and high relapse incidence, there are still unmet needs in developing optimal therapeutic strategies for both frontline and relapsed/refractory settings. The ultimate goal is to develop innovative personalized combination therapy approaches for the purpose of delivering precision medicine to cure this disease.

Phase 1-2 study of vorinostat (SAHA), cladribine and rituximab (SCR) in relapsed B-cell non-Hodgkin lymphoma and previously untreated mantle cell lymphoma.

Altered DNA methylation and histone acetylation in lymphoma provided the rationale for using vorinostat (SAHA), cladribine and rituximab (SCR) in non-Hodgkin lymphomas (NHL) in this phase 1-2 study (NCT00764517). Treatment included cladribine 5 mg/m2 intravenously (IV) (days 1-5), rituximab 375 mg/m2 IV (weekly 4× for cycle 1 and 1×/month) and vorinostat orally once daily (days 1-14) every 28 days for up to six cycles. Phase 1 included relapsed patients (n = 10) in a standard 3 + 3 dose escalation design (vorinostat: 200, 300 and 400 mg). No dose-limiting toxicities were seen. The phase 2 dose for vorinostat was 400 mg po (days 1-14). The majority of phase 2 patients had mantle cell lymphoma (MCL) (n = 57; 39 previously untreated, 10 relapsed). The primary objective was objective response rate [complete response (CR) + partial response] which was 39% (7/18) in relapsed patients and 97% (38/39) with 80% (31/39) attaining a CR in previously untreated MCL. At a median follow-up of 42 months, median progression-free survival (PFS) and overall survival (OS) for relapsed NHL were 19·5 [95% confidence interval (CI): 2·0-33·0] and 25·0 (95% CI: 12·0-45·0) months respectively. Median PFS for previously untreated MCL was 84·0 months; OS could not be estimated. Toxicities were primarily haematological.

Mantle cell lymphoma and its management: where are we now?

Mantle cell lymphoma is a relatively new recognized hematological malignant disease, comprising of 2.5-6% non-Hodgkin's lymphomas. The complexity of its clinical presentations (nodular pattern, diffuse pattern, and blastoid variant), variety in disease progression, and treatment response, make this disease a research focus to both experimental oncology and clinical oncology. Overexpression of cyclin D1 and chromosome t(11,14) translocation are the known molecular biomarkers of this disease. Mantle cell international prognostic index (MIPI), ki-67 proliferation index, and TP53 mutation are emerging as the prognostic biomarkers. Epigenetic profile variance and SOX11 gene expression profile correlate with treatment response. Over the years, the treatment strategy has been gradually evolving from combination chemotherapy to combination of targeted therapy, epigenetic modulation therapy, and immunotherapy. In a surprisingly short period of time, FDA specifically approved 4 drugs for treating mantle cell lymphoma: lenalidomide, an immunomodulatory agent; Bortezomib, a proteasome inhibitor; and Ibrutinib and acalabrutinib, both Bruton kinase inhibitors. Epigenetic agents (e.g. Cladribine and Vorinostat) and mTOR inhibitors (e.g. Temsirolimus and Everolimus) have been showing promising results in several clinical trials. However, treating aggressive variants of this disease that appear to be refractory/relapse to multiple lines of treatment, even after allogeneic stem cell transplant, is still a serious challenge. Developing a personalized, precise therapeutic strategy combining targeted therapy, immunotherapy, epigenetic modulating therapy, and cellular therapy is the direction of finding a curative therapy for this subgroup of patients.

Combination epigenetic and immunotherapy overcomes resistance to monoclonal antibodies in hematologic malignancies: A new therapeutic approach.

We recently reported that addition of epigenetic agents could overcome resistance of leukemic cells to monoclonal antibody-mediated anti-tumor effects in T-cell prolymphocytic leukemia. We also reported that epigenetic agents could induce expression of the CD30 gene, thus providing a therapeutic target for the antibody drug conjugate brentuximab vedotin. Here we discuss these findings and their generality to treatment of other hematologic and solid malignancies.

Epigenetic therapy overcomes treatment resistance in T cell prolymphocytic leukemia.

T cell prolymphocytic leukemia (T-PLL) is a rare, mature T cell neoplasm with distinct features and an aggressive clinical course. Early relapse and short overall survival are commonplace. Use of the monoclonal anti-CD52 antibody alemtuzumab has improved the rate of complete remission and duration of response to more than 50% and between 6 and 12 months, respectively. Despite this advance, without an allogeneic transplant, resistant relapse is inevitable. We report seven complete and one partial remission in eight patients receiving alemtuzumab and cladribine with or without a histone deacetylase inhibitor. These data show that administration of epigenetic agents can overcome alemtuzumab resistance. We also report epigenetically induced expression of the surface receptor protein CD30 in T-PLL. Subsequent treatment with the anti-CD30 antibody-drug conjugate brentuximab vedotin overcame organ-specific (skin) resistance to alemtuzumab. Our findings demonstrate activity of combination epigenetic and immunotherapy in the incurable illness T-PLL, particularly in the setting of previous alemtuzumab therapy.

Vorinostat downregulates CD30 and decreases brentuximab vedotin efficacy in human lymphocytes.

With an increasing number of clinical trials looking at combination therapies in cancer, potential drug-drug interactions require particular attention. One such instance is the treatment of CD30(+) tumors after previous vorinostat (SAHA; suberoylanilide hydroxyamic acid) failure with the anti-CD30 antibody-drug conjugate brentuximab vedotin. Using B-, T-, and natural killer (NK)-cell lines in vitro, we demonstrate that SAHA downregulates the expression of CD30 and lowers the efficacy of subsequent brentuximab vedotin treatment if baseline CD30 levels are reduced by 50% or more. Interestingly, low-dose SAHA treatment that maintained 50% or more of basal CD30 expression followed by subsequent treatment with brentuximab vedotin led to enhanced antitumor activity. The downregulation of CD30 was short lived upon SAHA removal, suggesting that allowing SAHA washout may circumvent any interactions with subsequent drug therapies. Our findings confirm the requirement of CD30 for brentuximab vedotin efficacy and suggest that combination treatment with SAHA in CD30(dim) tumors may decrease efficacy. Combination treatment in highly CD30(+) tumors, however, increases efficacy and warrants further consideration as a new treatment paradigm.

Current approaches to epigenetic therapy for the treatment of mantle cell lymphoma.

Epigenetics is the study of heritable changes in phenotype or gene expression caused by mechanisms other than changes in the underlying DNA sequence. Such changes can include DNA methylation or histone modifications which both serve to silence gene expression. This review describes a new development in pharmacology, epigenetic therapy, which attempts to correct these epigenetic changes for the treatment of mantle cell lymphoma (MCL) and other B cell malignancies for which no consensus on standard therapy exists. One class of drugs utilized are the histone deacetylase inhibitors, (HDACi) which result in the accumulation of acetylated histones. Hyperacetylation of histones and nonhistone proteins are postulated to mediate the anticancer effects of these drugs. Another class of epigenetic agents are hypomethylating agents, that can cause both DNA and histone hypomethylation. Epigenetic drugs may be useful in the treatment of cancer where hypermethylation of tumor suppressor genes is known to lead to silencing of these genes. The purine analog cladribine has been shown to have hypomethylating properties and has activity as a single agent or in combination with other therapies for mantle cell lymphoma. Epigenetic therapy with the DNA hypomethylating agent 5-aza-2-deoxycytidine can also cause restoration of cell surface expression of the CD20 protein and increase rituximab sensitivity in vitro. Combinations of epigenetic agents may act synergistically to further potentiate the efficacy of monoclonal antibodies like rituximab and ofatumumab and improve the treatment outcome in MCL.

Cladribine plus rituximab is an effective therapy for newly diagnosed mantle cell lymphoma.

Mantle cell lymphoma (MCL) is a non-Hodgkin lymphoma that is incurable with standard chemotherapy. There is no consensus on the best initial therapy, especially for elderly patients, who are not candidates for aggressive treatment approaches. Current National Comprehensive Cancer Network (NCCN) treatment guidelines include rituximab (R) plus cladribine for the initial treatment of MCL. However, few data are available to substantiate this recommendation. Therefore, to further define the role of R-cladribine for the initial treatment of MCL, we performed a retrospective chart review of 31 patients with MCL (median age, 67) treated with R-cladribine. The majority of responding patients also received R maintenance. The overall response rate was 87%, with 61% of patients achieving a complete remission (CR/CRu). The estimated median follow-up was 32.5 months, median PFS was 37.5 months, and median OS was 85.2 months. One of 19 (5.3%) subjects in CR/CRu relapsed (median follow-up of 23 months). CR/CRu was associated with improved survival (p < 0.0001), while a high mantle cell international prognostic index (MIPI) was associated with worse survival (p = 0.05). There was one toxic death (neutropenic pseudomonal sepsis) related to treatment. R-cladribine is an effective therapy for previously untreated MCL, and these results validate the use of R-cladribine for the initial treatment of MCL.

Cladribine: not just another purine analogue?

Cladribine was synthesized as a purine analogue drug that inhibited adenosine deaminase. It received FDA approval in the 1980s for treatment of hairy cell leukemia. Given its toxicity towards lymphocytes and its corresponding immunosuppressive effects, it has been studied and found efficacious in a variety of hematologic malignancies and autoimmune conditions, most recently multiple sclerosis. This review highlights pharmacological, toxicological and clinical data for the use of cladribine. It also discusses existing and new mechanisms that may contribute to its unique clinical activity. Emerging data show that in addition to its known purine nucleoside analogue activity, cladribine possesses epigenetic properties, inhibiting S-adenosylhomocysteine hydrolase and DNA methylation. This may contribute to its efficacy and highlights the importance of studying combination therapy with other epigenetic or targeted agents. Clinical trials are underway in a variety of malignant and nonmalignant conditions.

Sox6 directly silences epsilon globin expression in definitive erythropoiesis.

Sox6 is a member of the Sox transcription factor family that is defined by the conserved high mobility group (HMG) DNA binding domain, first described in the testis determining gene, Sry. Previous studies have suggested that Sox6 plays a role in the development of the central nervous system, cartilage, and muscle. In the Sox6-deficient mouse, p100H, epsilony globin is persistently expressed, and increased numbers of nucleated red cells are present in the fetal circulation. Transfection assays in GM979 (erythroleukemic) cells define a 36-base pair region of the epsilony proximal promoter that is critical for Sox6 mediated repression. Electrophoretic mobility shift assay (EMSA) and chromatin immunoprecipitation (ChIP) assays demonstrate that Sox6 acts as a repressor by directly binding to the epsilony promoter. The normal expression of Sox6 in wild-type fetal liver and the ectopic expression of epsilony in p100H homozygous fetal liver demonstrate that Sox6 functions in definitive erythropoiesis. The present study shows that Sox6 is required for silencing of epsilony globin in definitive erythropoiesis and suggests a role for Sox6 in erythroid cell maturation. Thus, Sox6 regulation of epsilony globin might provide a novel therapeutical target in the treatment of hemoglobinopathies such as sickle cell anemia and thalassemia.

Targeted deletion of the chicken beta-globin regulatory elements reveals a cooperative gene silencing activity.

The chicken beta-globin locus represents a well characterized system to study the role of both proximal and distal regulatory elements in a eukaryotic multigene domain. The function of the chicken beta(A)/epsilon-intergenic enhancer and upstream regulatory elements 5'-HS1 and 5'-HS2 were studied using a gene targeting approach in chicken DT40 cells followed by microcell-mediated chromosome transfer into human erythroleukemia cells (K562). These regulatory elements all repressed expression of the rho- and beta(H)-chicken globin genes in the chromosome transfer assay. No rho- or beta(H)-globin gene expression was detected in K562 cells containing the chicken chromosome without deletions, whereas rho- and beta(H)-mRNA was activated in K562 cells containing chicken chromosomes with deletions of the intergenic enhancers, 5'-HS1 and 5'-HS2. Transcriptional activation of the rho- and beta(H)-globin genes correlated with hyperacetylation of histones H3 and H4, loss of histone H3 lysine 9 methylation, and binding of RNA polymerase II to the gene promoters. Surprisingly, the status of CpG dinucleotide methylation at the promoters did not correlate with the transcriptional status of the genes. Our results using a chromosomal transfer assay demonstrate an identical silencing function for these regulatory elements, which suggests they function as part of a common silencing pathway or complex.

Cyclin D1 activation in B-cell malignancy: association with changes in histone acetylation, DNA methylation, and RNA polymerase II binding to both promoter and distal sequences.

Cyclin D1 expression is deregulated by chromosome translocation in mantle cell lymphoma and a subset of multiple myeloma. The molecular mechanisms involved in long-distance gene deregulation remain obscure, although changes in acetylated histones and methylated CpG dinucleotides may be important. The patterns of DNA methylation and histone acetylation were determined at the cyclin D1 locus on chromosome 11q13 in B-cell malignancies. The cyclin D1 promoter was hypomethylated and hyperacetylated in expressing cell lines and patient samples, and methylated and hypoacetylated in nonexpressing cell lines. Domains of hyperacetylated histones and hypomethylated DNA extended over 120 kb upstream of the cyclin D1 gene. Interestingly, hypomethylated DNA and hyperacetylated histones were also located at the cyclin D1 promoter but not the upstream major translocation cluster region in cyclin D1-nonexpressing, nontumorigenic B and T cells. RNA polymerase II binding was demonstrated both at the cyclin D1 promoter and 3' immunoglobulin heavy-chain regulatory regions only in malignant B-cell lines with deregulated cyclin D1 expression. Our results suggest a model where RNA polymerase II bound at IgH regulatory sequences can activate the cyclin D1 promoter by either long-range polymerase transfer or tracking.

Replication initiation patterns in the beta-globin loci of totipotent and differentiated murine cells: evidence for multiple initiation regions.

The replication initiation pattern of the murine beta-globin locus was analyzed in totipotent embryonic stem cells and in differentiated cell lines. Initiation events in the murine beta-globin locus were detected in a region extending from the embryonic Ey gene to the adult betaminor gene, unlike the restricted initiation observed in the human locus. Totipotent and differentiated cells exhibited similar initiation patterns. Deletion of the region between the adult globin genes did not prevent initiation in the remainder of the locus, suggesting that the potential to initiate DNA replication was not contained exclusively within the primary sequence of the deleted region. In addition, a deletion encompassing the six identified 5' hypersensitive sites in the mouse locus control region had no effect on initiation from within the locus. As this deletion also did not affect the chromatin structure of the locus, we propose that the sequences determining both chromatin structure and replication initiation lie outside the hypersensitive sites removed by the deletion.