Biology Of Mantle Cell Lymphoma Research Articles

Impact of PIK3CA gain and PTEN loss on mantle cell lymphoma biology and sensitivity to targeted therapies

AbstractBesides many other mutations in known cancer driver genes, mantle cell lymphoma (MCL) is characterized by recurrent genetic alterations of important regulators of the phosphoinositol-3-kinase (PI3K) cascade including PIK3CA gains and PTEN losses. To evaluate the biological and functional consequences of these aberrations in MCL, we have introduced transgenic expression of PIK3CA (PIK3CA UP) and performed knockout/knockdown of PTEN gene (PTEN KO/KD) in 5 MCL cell lines. The modified cell lines were tested for associated phenotypes including dependence on upstream B-cell receptor (BCR) signaling (by an additional BCR knockout). PIK3CA overexpression decreased the dependence of the tested MCL on prosurvival signaling from BCR, decreased levels of oxidative phosphorylation, and increased resistance to 2-deoxy-glucose, a glycolysis inhibitor. Unchanged protein kinase B (AKT) phosphorylation status and unchanged sensitivity to a battery of PI3K inhibitors suggested that PIK3CA gain might affect MCL cells in AKT-independent manner. PTEN KO was associated with a more distinct phenotype: AKT hyperphosphorylation and overactivation, increased resistance to multiple inhibitors (most of the tested PI3K inhibitors, Bruton tyrosine kinase inhibitor ibrutinib, and BCL2 inhibitor venetoclax), increased glycolytic rates with resistance to 2-deoxy-glucose, and significantly decreased dependence on prosurvival BCR signaling. Our results suggest that the frequent aberrations of the PI3K pathway may rewire associated signaling with lower dependence on BCR signaling, better metabolic and hypoxic adaptation, and targeted therapy resistance in MCL.

Twenty Years of Advancing Discoveries and Treatment of Mantle Cell Lymphoma.

Mantle cell lymphoma (MCL) is an aggressive subtype of non-Hodgkin lymphoma characterized by the t(11;14) chromosomal translocation, which leads to the dysregulation of the cell cycle through overexpression of cyclin D1. Although advances in treatment have improved outcomes, in particular the introduction of Bruton tyrosine kinase inhibitors to the treatment armamentarium and more recently chimeric antigen receptor T-cell therapy, MCL often rapidly develops resistance and has a high rate of relapse. In addition, MCL is clinically heterogeneous. Response to treatment can vary, making it difficult to establish a standard treatment approach. Thus, there remains a significant need for more research on MCL biology, including those molecular mechanisms underpinning treatment response or lack thereof, so that novel agents may be identified and/or the use of existing agents may be optimized. At the Lymphoma Research Foundation's 20th MCL Scientific Consortium and Workshop, researchers gathered to discuss recent developments in both basic scientific and clinical research to continue to develop an understanding of MCL and improve outcomes for patients. This report, which includes a summary of each presentation, reviews the findings presented at the workshop and highlights opportunities, open questions, and areas for future study that would pave the way for a cure for this disease in the coming decades.

NOTCH Signaling in Mantle Cell Lymphoma: Biological and Clinical Implications.

Despite major progress in mantle cell lymphoma (MCL) therapeutics, MCL remains a deadly disease with a median survival not exceeding four years. No single driver genetic lesion has been described to solely give rise to MCL. The hallmark translocation t(11;14)(q13;q32) requires additional genetic alterations for the malignant transformation. A short list of recurrently mutated genes including ATM, CCND1, UBR5, TP53, BIRC3, NOTCH1, NOTCH2, and TRAF2 recently emerged as contributors to the pathogenesis of MCL. Notably, NOTCH1 and NOTCH2 were found to be mutated in multiple B cell lymphomas, including 5-10% of MCL, with most of these mutations occurring within the PEST domain of the protein. The NOTCH genes play a critical role in the early and late phases of normal B cell differentiation. In MCL, mutations in the PEST domain stabilize NOTCH proteins, rendering them resistant to degradation, which subsequently results in the upregulation of genes involved in angiogenesis, cell cycle progression, and cell migration and adhesion. At the clinical level, mutated NOTCH genes are associated with aggressive features in MCL, such as the blastoid and pleomorphic variants, a shorter response to treatment, and inferior survival. In this article, we explore in detail the role of NOTCH signaling in MCL biology and the ongoing efforts toward targeted therapeutic interventions.

Mantle cell lymphoma-Advances in molecular biology, prognostication and treatment approaches.

Mantle cell lymphoma (MCL) is clinically characterized by its heterogenous behavior with courses ranging from indolent cases that do not require therapy for years to highly aggressive MCL with very limited prognosis. A better understanding of the complex biology of MCL has already led to the approval of several innovative agents, expanding the landscape of MCL therapies and improving therapeutic options especially for refractory or relapsed disease. Nevertheless, to further optimize MCL treatment, early identification of individual risk profile and risk-adapted, patient-tailored choice of therapeutic strategy needs to be prospectively incorporated in clinical patient management. This review highlights recent advances in deciphering the molecular background of MCL, the definition of prognostically relevant factors and the identification of potential druggable targets and summarizes current treatment recommendations for primary and relapsed/refractory MCL including novel targeted therapies.

Mantle cell lymphoma - advances in molecular biology, prognostication and treatment approaches.

Mantle cell lymphoma (MCL) is clinically characterised by its heterogenous behaviour with courses ranging from indolent cases that do not require therapy for years to highly aggressive MCL with a very limited prognosis. A better understanding of the complex biology of MCL has already led to the approval of several innovative agents, expanding the landscape of MCL therapies and improving therapeutic options especially for refractory/relapsed (R/R) disease. Nevertheless, to further optimise MCL treatment, early identification of individual risk profile and risk-adapted, patient-tailored choice of therapeutic strategy needs to be prospectively incorporated into clinical patient management. The present review highlights recent advances in deciphering the molecular background of MCL, the definition of prognostically relevant factors and the identification of potential druggable targets and summarises current treatment recommendations for primary and R/R MCL including novel targeted therapies.

Towards ecosystem integration for a better understanding of aggressiveness of B-cell lymphomas.

Towards ecosystem integration for a better understanding of aggressiveness of B-cell lymphomas.

High-Risk Mantle Cell Lymphoma in the Era of Novel Agents.

Mantle cell lymphoma (MCL) is a heterogenous disease with a variety of morphologic and genetic features, some of which are associated with high risk disease. Here we critically analyze the current state of the understanding of MCL's biology and its implications in therapy, with a focus on chemotherapy-free and targeted therapy regimens. Mantle cell lymphoma (MCL) is a rare subtype of non-Hodgkin's lymphoma, defined by a hallmark chromosomal translocation t(11;14) which leads to constitutive expression of cyclin D1. Recent discoveries in the biology of MCL have identified a number of factors, including TP53 mutations and complex karyotype, that lead to unresponsiveness to traditional chemoimmunotherapy and poor outcomes. Bruton tyrosine kinase inhibitors, BH3-mimetics and other novel agents thwart survival of the neoplastic B-cells in a manner independent of high-risk mutations and have shown promising activity in relapsed/refractory MCL. These therapies are being investigated in the frontline setting, while optimal responses to chemotherapy-free regimens, particularly in high-risk disease, might require combination approaches. High-risk MCL does not respond well to chemoimmunotherapy. Targeted agents are highly active in the relapsed refractory setting and show promise in high-risk disease. Novel approaches may soon replace the current standard of care in both relapsed and frontline settings.

Population Based Analysis of Mantle Cell Lymphoma in Texas: Are Outcomes Any Different in Hispanics?

Introduction: Mantle cell lymphoma (MCL) is a rare type of incurable B-cell lymphoma with an incidence rate of ~0.8/100,000 in the United States (US) (Blood, PMID: 30154113; CA Cancer J Clin, PMID: 27618563). Recent advances in understanding of MCL biology, development of new therapeutic modalities such as Bruton tyrosine kinsase inhibitors (BTKi), and advancement of treatment strategy incorporating chemotherapy and non-chemotherapy treatment modalities have improved survival (Am J Hematol, PMID: 30963600; Blood, PMID: 26059948; Blood, PMID: 28899853). However, prognosis for MCL remains poor overall (Blood, PMID: 30154113). Although variations in incidence in MCL by race has been reported in the literature (CA Cancer J Clin, PMID: 27618563), there is currently limited data available on differences in demographics, treatment patterns, and outcomes in Hispanic (H) MCL patients. Methods: In this retrospective cohort study, de-identified data was obtained from the Texas Cancer Registry (TCR) database for those diagnosed with MCL between 2006-2016. Standard demographic variables collected include gender, race, ethnicity, birthplace, dates at diagnosis and death, primary payer at diagnosis, stage, type of treatment, poverty index, and vitality status among others. The significance of variation in the distribution of outcomes with ethnicity [H, non-Hispanic (NH)] was assessed with Fisher's Exact test, Pearson's Chi-square test, T-test, or Wilcoxon test as appropriate. Survival time was measured in years from date of primary diagnosis to date of death. Patients not coded as dead were considered censored on survival time at the date last seen. Survival distributions were described with Kaplan-Meier curves and significance of variation in median survival with ethnicity was assessed with log rank testing. All statistical testing was two-sided with a significance level of 0.05. Results: A total of 1852 (296 H, 1556 NH) patients were included in the final analysis. Median age at diagnosis were 65.5 (H) and 68.0 (NH). 72.6% of H and 72.7% of NH cohorts were male. Of the NH cohort, 92.5% were White, 5.3% Black, 1.5% Asian, 0.4% Native American and 0.1% with unknown race. There was a statistically significant difference between the cohorts in the poverty index. Most H (50.5%) were in the 20-100% bracket, while the majority of NH (36.2%) were in the 10-19.9%. The majority of the cohort were from metro areas (90.2% H and 82.6% NH) and non-border counties (72.6% H and 97.2% NH). There was a statistically significant difference in insurance status at diagnosis between the cohorts. Medicare was the most common type for both H (41.1%) and NH (50.2%), while 13.4% of H and 4.0% of NH were uninsured. The majority of H (66.2%) and NH (64.0%) were diagnosed with stages 3-4 MCL; for H, stage 1 10.5%, stage 2 6.1%, stages 3-4 66.2%; for NH, stage 1 10.4%, stage 2 6.6%, stages 3-4 64.0%. The most common treatment received was combination chemotherapy (43.2% H, 38.8% NH); for H, combination chemotherapy (CC) 43.2%, single agent chemotherapy (SAC) 7.4%, chemotherapy not otherwise specified (CNOS) 14.5%, died prior to recommended treatment (PRI) 1%, refused recommended treatment (REF) 0.7%, treatment recommended but not given (NG) 0.3%, treatment contraindicated (CI) 0.7%, no treatment (NT) 18.6% and unknown treatment status (UTS) 13.5%; for NH, CC 38.8%, SAC 10.5%, CNOS 14.5%, PRI 0.2%, REF 1.3%, NG 0.3%, CI 0.8%, NT 23.0% and UTS 10.4%. Regarding BMT/stem cell infusion, 3.1% H and 3.6 NH were confirmed to have received it; 2.5% H and 2.1% NH were confirmed to have received treatment involving radiation. Median survival was 3.7 years (y) and 3.8 y for H and NH respectively; the survival probability at 2 y was 0.65 (0.59-0.71) vs 0.65 (0.62-0.68), 5 y 0.40 (0.33-0.48) vs 0.41 (0.38-0.44) and 10 y 0.19 (0.12-0.30) vs 0.14 (0.09-0.21) for H and NH respectively. There was no statistically significant differences between the cohorts on stage of disease at diagnosis, types of treatment received or overall survival probability. Conclusions: In Texas residents diagnosed with mantle cell lymphoma between 2006-2016, there were statistically significant differences in the level of poverty and insurance coverage between H and NH cohorts but no differences in stage at diagnosis, type of treatment received, or survival. Disclosures Diaz Duque: ADCT Therapeutics: Research Funding; Molecular Templates: Research Funding; AstraZeneca: Research Funding; Hutchinson Pharmaceuticals: Research Funding; Seattle Genetics: Speakers Bureau; Verastem: Speakers Bureau; AbbVie: Speakers Bureau.

Advances in Molecular Biology and Targeted Therapy of Mantle Cell Lymphoma.

Mantle cell lymphoma (MCL) is a heterogeneous malignancy with a broad spectrum of clinical behavior from indolent to highly aggressive cases. Despite the fact that MCL remains in most cases incurable by currently applied immunochemotherapy, our increasing knowledge on the biology of MCL in the last two decades has led to the design, testing, and approval of several innovative agents that dramatically changed the treatment landscape for MCL patients. Most importantly, the implementation of new drugs and novel treatment algorithms into clinical practice has successfully translated into improved outcomes of MCL patients not only in the clinical trials, but also in real life. This review focuses on recent advances in our understanding of the pathogenesis of MCL, and provides a brief survey of currently used treatment options with special focus on mode of action of selected innovative anti-lymphoma molecules. Finally, it outlines future perspectives of patient management with progressive shift from generally applied immunotherapy toward risk-stratified, patient-tailored protocols that would implement innovative agents and/or procedures with the ultimate goal to eradicate the lymphoma and cure the patient.

Risk stratification of mantle cell lymphoma (MCL)

Despite of a better understanding of the biology of mantle cell lymphoma (MCL), it remains an incurable disease with very variable disease courses. The biological heterogeneity of MCL requires the identification of prognostic markers for risk stratification and tailored treatment of MCL. The combined MCL International Prognostic Index (MIPI-c) represents a well-established clinical risk stratification model. Based on four clinical parameters: age, performance status, lactate dehydrogenase and leucocyte count combined with the percentage of Ki-67 positive MCL cells the model distinguishes four MCL subgroups with very different outcomes. Further prognostic markers, in particular molecular lesions might help to further improve clinical scoring. We discuss the value of clinical and molecular markers to predict outcome of MCL and how these markers could influence treatment decisions.

Current overview and treatment of mantle cell lymphoma.

Mantle cell lymphoma (MCL) is a B-cell non-Hodgkin lymphoma with historically poor long-term survival compared with other B-cell malignancies. Treatment strategies for this disease are variable and dependent on symptoms and patient fitness. Despite recent advances, MCL remains incurable and patients with high-risk disease have particularly poor outcomes. This review focuses on recent developments that enhance our understanding of the biology of MCL and new treatment approaches that have led to substantial improvements in clinical outcomes. We will outline induction immuno-chemotherapy and maintenance strategies in transplant-eligible patients. In addition, effective strategies for patients unfit for intensive induction will be discussed, with a particular focus on novel molecular therapies with activity in MCL. Lastly, a number of ongoing clinical trials will be presented; the data from these trials are anticipated to redefine standards of care in the near future.

Role of SOX11 and Genetic Events Cooperating with Cyclin D1 in Mantle Cell Lymphoma.

Mantle cell lymphoma (MCL) is an aggressive lymphoid neoplasm, incurable with current therapies. The t(11;14)(q13;q32) involving cyclin D1 is considered the first oncogenic hit found in virtually all MCLs. However, additional secondary genomic alterations are essential for complete transformation. MCLs are genetically very unstable with several genetic alterations associated with its high proliferative behavior involving several oncogenic pathways. Furthermore, SOX11 is overexpressed in the majority of conventional MCLs (cMCL), including cyclin D1-negative cases, but absent in non-nodal leukemic MCL with indolent clinical behavior (nnMCL). Recent data have revealed the potential oncogenic role of SOX11 in MCL biology, highlighting its implication in tumor aggressiveness and progression. This review addresses the implication of SOX11 overexpression and frequent genetic lesions, cooperating with cyclin D1 underlying the pathogenesis of this aggressive disease.

Recommendations for Clinical Trial Development in Mantle Cell Lymphoma.

Mantle cell lymphoma (MCL) comprises around 6% of all non-Hodgkin's lymphoma (NHL) diagnoses. In younger patients, age less than 60 to 65 years, aggressive induction often followed by consolidation with autologous stem cell transplant has suggested improved outcomes in this population. Less intensive therapies in older patients often followed by maintenance have been studied or are under active investigation. However, despite recent advances, MCL remains incurable, with a median overall survival of around five years. Patients with high-risk disease have particularly poor outcomes. Treatment varies widely across institutions, and to date no randomized trials comparing intensive vs less intensive approaches have been reported. Although recent data have highlighted the heterogeneity of MCL outcomes, patient assessment for treatment selection has largely been driven by patient age with little regard to fitness, disease biology, or disease risk. One critical advance is the finding that minimal residual disease status (MRD) after induction correlates with long-term outcomes. As such, its use as a potential end point could inform clinical trial design. In order to more rapidly improve the outcomes of MCL patients, clinical trials are needed that prospectively stratify patients on the basis of MCL biology and disease risk, incorporate novel agents, and use MRD to guide the need for additional therapy.

B-Cell Receptor Driven MALT1 Activity Regulates MYC Signaling in Mantle Cell Lymphoma

Mantle cell lymphoma (MCL) is a mature B-cell lymphoma characterized by poor prognosis. Recent studies revealed the importance of constitutive B-cell receptor (BCR) signaling in maintaining survival of a subset of MCLs. MALT1 is an essential component of the CARD11-BCL10-MALT1 (CBM) complex that links BCR signaling to the nuclear factor kappa-B (NF-κB) pathway. Additionally, MALT1 functions as a protease that cleaves various substrates to promote proliferation and survival. However, its role in the molecular pathogenesis of MCL is unknown.To elucidate the functional role of MALT1 in the biology of MCL, we determined its proteolytic activity in primary MCL cells and in MCL derived cell lines. A large fraction of MCLs displayed constitutive activity of MALT1. This MALT1 activity is driven by constitutive BCR signaling, as we were able to show that RNA interference-mediated knockdown of central components of the BCR cascade abolished MALT1 activity.To gain insights into the functional significance of MALT1 in MCL, we knocked down its expression by different MALT1 shRNAs. Transduction of these shRNAs induced cytotoxicity in models that are characterized by constitutive MALT1 activity, whereas no effect on survival was observable in MCLs without MALT1 activation. To determine if this MALT1 addiction translates into an in vivosetting, we knocked down MALT1 in mouse MCL models and detected a significant inhibition of tumor growth. This indicates that MALT1-activated MCLs are dependent on the function of MALT1. These results were confirmed as pharmacologic inhibition of MALT1 significantly reduced cell viability in MALT1-activated MCLs, implying that MALT1 inhibition might represent a promising therapeutic strategy for MCL patients.To understand which biologic processes are regulated by MALT1 in MCL, we profiled gene expression changes at different time points following MALT1 inhibition. An unbiased gene set enrichment analysis identified various previously described MYC gene expression signatures to be among the top downregulated signatures, suggesting that MALT1 regulates MYC expression. MYC downregulation following MALT1 inhibition or MALT1 knockdown was confirmed at the protein level and various analyses revealed that MALT1 regulates MYC expression posttranslationally by preventing its proteasomal degradation. These results were further confirmed in primary mouse splenocytes, indicating that this novel molecular mechanism of regulating MYC expression is not restricted to MCL.To confirm that MYC is indeed expressed in primary MCLs, we determined MYC expression in 234 primary MCL samples by immunohistochemistry. These analyses revealed that 75 samples (32.1%) displayed an intermediate and 55 samples (23.5%) a high MYC positivity, suggesting that MYC is expressed in a substantial number of primary MCLs. As common alterations such as MYC high-levelamplifications and translocations determined by FISH occurred extremely rarely in our primary MCL samples (1% of samples), it is conceivable that BCR-driven MALT1 signaling is the predominant mechanism of MYC upregulation in MCL.In summary, we report for the first time that a substantial fraction of MCLs is addicted to constitutive MALT1 signaling. Thus, MCLs can be divided based on their MALT1 activation status into two distinct subgroups. We further identified a novel regulatory mechanism of MYC expression by MALT1. Thus, our study provides a strong mechanistic rationale to investigate the therapeutic efficacy in targeting the MALT1-MYC axis in MCL patients. DisclosuresTrneny:Janssen Research & Development: Consultancy, Honoraria, Membership on an entity’s Board of Directors or advisory committees; BMS: Consultancy, Honoraria, Membership on an entity’s Board of Directors or advisory committees; Gilead: Consultancy, Honoraria, Membership on an entity’s Board of Directors or advisory committees; Roche: Consultancy, Honoraria, Membership on an entity’s Board of Directors or advisory committees, Research Funding; Celgene: Consultancy, Honoraria, Membership on an entity’s Board of Directors or advisory committees, Research Funding; Takeda: Consultancy, Honoraria, Membership on an entity’s Board of Directors or advisory committees. Dreyling:Roche: Consultancy, Honoraria, Research Funding, Speakers Bureau. Tzankov:Novartis: Speakers Bureau; Abbott: Speakers Bureau.

The G-Protein Coupled Receptors and G-Proteins Alpha Expression in Mantle Cell Lymphoma

Mantle cell lymphoma (MCL) is a B cell Non-Hodgkin lymphoma comprising approximately 8% of malignant lymphomas. MCL is considered to be an incurable disease even though survival has improved with novel biological therapies that interrupt survival signaling from the lymphoma microenvironment. The signaling pathways that are deregulated and the factors leading to systemic dissemination of the disease are still poorly understood. There is also a clear need to identify additional druggable targets for therapy (Saba and Wiestner, Curr Opin Hematol, 2014). Druggable targets may be G-protein coupled receptors (GPCRs) and G-proteins. GPCRs belong to the family of seven transmembrane receptors, which upon activation by extracellular ligands transfer the signals inside the cell for activation of the specific pathway. The signaling involves G-proteins. G-proteins consist of the subunits: alpha, beta and gamma and their subtypes. During GPCR activation the G alpha subunit is released and the subtype of G-protein subunit determines which downstream signaling pathways (including Akt, PI3K, ERK, JNK, MAPK, NFkappaB and others) is then activated. In the immune cells different subtypes of G-proteins alpha are instrumental for leukocyte migration, architecture of B cells compartments in spleen, thymus, lymph nodes, and gastrointestinal tract (Hwang et al., PlosOne, 2013) and BCR-mediated cell death (Misra et al., J Exp Med, 2010). G alpha13 signaling is involved in development of germinal centre-derived lymphomas (Muppidi et al., Nature, 2014).In order to map the aberrant expression of GPCR and G-proteins in MCL, the expression of genes encoding for GPCRs and G-protein alpha subunits was analyzed by Affymetrix U133A Array of seventeen MCL biopsies and eight non-malignant lymph nodes. Among investigated GPCR and G-protein alpha subunit genes 25/298 were differently expressed in MCL compared to reactive lymph nodes (moderated t-test, adj. p=or< than 0.05). The four most significantly different genes expressed were: LPAR6, GPRC5C, OPN3 and GNAZ (all adj.p<0.003). The latter, GNAZ, encodes for G-protein alpha z. The analysis of GNAZ by qPCR in 77 additional MCL biopsies from a population-based Stockholm MCL cohort showed varied expression of GNAZ. Interestingly, the MCL cases, which expressed the highest levels of GNAZ, had significantly worse survival (Kaplan-Meier, log rank, p<0.003) suggesting that GNAZ has, a yet unknown, role in MCL biology. Further analysis showed that GNAZ expression was correlated to lymphocytosis (Mann-Whitney test, p=0.023) and leukocytosis (Mann-Whitney test, p=0.011) in MCL patients but not to: high tumor cell proliferation, blastoid morphology nor to p53 immunoreactivity. Our results suggest that GNAZ-signaling is of importance for cell-cell interaction in the tumor microenvironment and/or for egress of lymphoma cells to the blood. DisclosuresNo relevant conflicts of interest to declare.

A Systemic Review of CD5-Negative Mantle Cell Lymphoma Identifies Potential Clinical and Biological Implications

Introduction: Mantle cell lymphoma (MCL) is an aggressive subtype of non-Hodgkin lymphoma (NHL) with a median survival of 3 to 5 years. MCL is characterized by the translocation t(11;14)(q13;32) which results in the overexpression of cyclin-D1 and ultimately an uninhibited G1/S cell cycle transition. MCL has a distinctive immunophenotype among B-cell NHL, characterized by a strong expression of the pan B-cell markers CD19 and CD20, absence of CD10 and CD23, overexpression of the anti-apoptotic protein BCL2, and aberrant expression of the T-cell marker CD5. However, up to 10% of MCL lack CD5 expression and remain ill-characterized. Whether this absence of CD5 expression impacts MCL biology and clinical course remains unknown. We performed a systematic review of all reported cases of CD5-negative MCL and analyzed their biological and clinical characteristics.Patients and methods: A systematic literature search was performed and included studies published from 1st June 1994 to 1st June 2016 in PubMed, Embase, and Web of Science. We used the key words CD5 negative, CD5-, mantle cell lymphoma, and MCL. Data was tabulated regarding the following 16 variables: t(11;14)(q13;q32), cyclin-D1, CD5, CD10, CD19, CD20, CD23, BCL2, BCL6, Ki-67 (higher or lower than 30%), IGHV mutation status (mutated IGHV >3% discordance with germline), male to female ratio, light chain expression (kappa or lambda), presence of a leukemic phase, stage, and overall survival (OS). Data was reported as percent and total number of cases with available data of each variable.Results and discussion: 68 out of 470 screened articles included CD5-negative MCL cases. After exclusion of duplicates, 50 sources (46 full articles and 4 abstracts) were included. Data of 222 cases of CD5-negative MCL were collected.To a degree, reviewed cases of CD-5 negative MCL shared similarities to classic MCL. Both sub-types had a median age at diagnosis of approximately 65 and presented as stage IV disease 70% of the time. Both subtypes overexpressed cyclin-D1 (100%, 222/222), possessed the t(11;14)(q13;q32) (93%, 49/53: 49 of 53 cases with available data on the translocation), were CD-19 positive (100%,18/18), CD20-positive (100%, 58/58), BCL2-positive (97%, 34/35), CD10-negative (93%, 42/45), and CD23-negative (95%,56/59). Presence or absence of leukemic phase was reported in 16 cases, 8 of those were positive for circulating MCL cells (50%). The proliferation marker Ki-67 was reported in 22 cases, 7 (32%) of which were >30%.CD5-negative MCL deviated from the classic MCL presentation in a number of clinical and biological variables. Most importantly, the median OS of 47 cases with available follow-up was greater than 16 years (Figure 1), which compared very favorably to the historic survival of 3 to 5 years in classic MCL. Interestingly, the number of affected males was less than expected in the CD5-negative group. Male-to-female ratio was 2:1 (74 males and 36 females of 110 cases with available gender data), which is lower than the expected 3:1 ratio.From a biological standpoint, the CD5-negative MCL cohort had more kappa than lambda-restricted cases (62%, 13 of 21 available light chain data), and more mutated than unmutated IGHV (61% mutated, 11 of 18 cases with available IGHV data). Classically, lambda-restricted MCL and unmutated IGHV are more commonly seen and were associated with worse clinical outcomes. In addition, we observed BCL6 expression in 23% of CD5-negative MCL cases, which is higher than expected (6 of 26 cases with BCL6 available data).Conclusions: To our knowledge this is the most comprehensive review of CD5-negative MCL. Lack of CD5 expression was associated with important clinical and biological differences compared to classic MCL. The higher survival observed in our analysis suggest that CD5 can potentially be incorporated in identifying a subset of a more indolent MCL that might benefit from a watch and wait approach. Currently, treatment in MCL can be differed in a subset of patients with an indolent presentation characterized by leukemic-only disease with absence of lymphadenopathy, mutated IGHV, and lack of SOX11 expression. SOX11 data was not available in our cohort, and only 18 patients had available IGHV mutation data. While the exact role of CD5 in MCL remains unknown, our findings highlight the need for a deeper investigation of CD5-negative MCL at the genetic, phenotypic, and clinical levels. [Display omitted] DisclosuresNo relevant conflicts of interest to declare.

Mantle Cell Lymphoma.

Mantle cell lymphoma (MCL) is an uncommon subtype of non-Hodgkin lymphoma previously considered to have a poor prognosis. Large gains were made in the first decade of the new century when clinical trials established the importance of high-dose therapy and autologous stem-cell rescue and high-dose cytarabine in younger patients and the benefits of maintenance rituximab and bendamustine in older patients. In particular, greater depth of understanding of the molecular pathophysiology of MCL has resulted in an explosion of specifically targeted new efficacious agents. In particular, agents recently approved by the Food and Drug Administration include the proteasome inhibitor bortezomib, immunomodulator lenalidomide, and Bruton's tyrosine kinase inhibitor ibrutinib. We review recent advances in the understanding of MCL biology and outline our recommended approach to therapy, including choice of chemoimmunotherapy, the role of stem-cell transplantation, and mechanism-based targeted therapies, on the basis of a synthesis of the data from published clinical trials.

Do mantle cell lymphomas have an 'Achilles heel'?

Mantle cell lymphoma (MCL) is a mature B-cell malignancy that continues to have a high mortality rate. In this article, we discuss key pathogenic pathways in MCL biology and their possible therapeutic targeting. In addition to cyclin-D1, the transcription factor SOX-11 emerged as a common characteristic of MCL. Genomic studies have identified a number of recurrently mutated genes; in order of descending frequency these include ATM, CCND1, UBR5, TP53, BIRC3, NOTCH1/2 and TRAF2. However, no clear oncogenic driver has been identified. In contrast, several observations indicate that MCL cells are antigen-experienced cells and that the tumor microenvironment and B-cell receptor engagement are important. This is underscored by the impressive clinical responses achieved with the Bruton's tyrosine kinase inhibitor ibrutinib. Recently identified activating mutations in the noncanonical nuclear factor-kappa B pathway could give rise to ibrutinib resistance. Poly-ADP ribose polymerase and aurora kinase inhibitors may be synthetic lethal with the common aberrations in DNA damage pathways found in MCL. Also, ABT-199, a potent and selective inhibitor of B-cell lymphoma 2, has promising activity in early studies. MCL is a heterogeneous disease, and no single Achilles heel has been identified. Nevertheless, genomic, molecular and clinical studies have revealed vulnerabilities that can be exploited for effective therapy.

In Vivo Growth of Mantle Cell Lymphoma Xenografts in Immunodeficient Mice Is Positively Regulated by VEGF and Associated with Significant Up-regulation of CD31/PECAM1

Mantle cell lymphoma (MCL) is an aggressive lymphoma subtype with dismal prognosis. New treatments are needed to improve outcome of relapsed/refractory disease. Recently, several drugs targeting at least partially the process of angiogenesis have been successfully tested in the therapy of MCL. Molecular mechanisms that regulate MCL-induced angiogenesis and that might represent potential new druggable targets remain, however, incompletely understood. We established two mouse models of human MCL by subcutaneous xenotransplantation of JEKO-1 and HBL-2 cell lines into immunodeficient mice. Histological analyses of xenografts confirmed their neovascularization. The growth of xenografts was significantly suppressed by single-agent therapy with bevacizumab, monoclonal antibody targeting vascular endothelial growth factor (VEGF). Subsequently, we analysed expression of 94 angiogenesis-related genes in ex vivo isolated JEKO-1 and HBL-2 cells compared to in vitro growing cells using TaqMan low-density arrays. The most up-regulated genes in both JEKO-1 and HBL-2 xenografts were genes encoding platelet/endothelial cell-adhesion molecule (CD31/PECAM1), VEGF receptor 1 (FLT1), hepatocyte growth factor (HGF), angiogenin (ANG) and transcription factor PROX1. The most downregulated genes in both JEKO-1 and HBL-2 xenografts were midkine (MDK) and ephrine B2 (EPHB2). In summary, our results demonstrate an important role of angiogenesis in the biology of MCL and provide preclinical evidence of potent anti-MCL activity of bevacizumab. In addition, gene expression profiling of 94 angiogenesis-related targets revealed several in vivo up-regulated and down-regulated transcripts. The most differentially expressed target in both MCL tumours was CD31/PECAM1. Whether any of these molecules might represent a potential druggable target in MCL patients remains to be elucidated.

CD31/PECAM-1 Is Overexpressed On Mantle-Cell Lymphoma (MCL) Primary Cells and Positively Regulates Engraftment and Growth of MCL Cell Lines in Immunodeficient Mice.

AbstractAbstract 2681Mantle-cell lymphoma (MCL) is a lymphoma subtype with poor prognosis. Recently, new drugs targeting at least partially the angiogenesis cascade have been successfully tested in the therapy of relapsed MCL patients, including temsirolimus, enzastaurin and lenalidomide. To reveal molecular mechanisms that regulate MCL-induced angiogenesis (and that might represent potential new druggable targets), we established and analyzed two mouse models of human MCL. Immunodeficient mice were subcutaneously (s.c.) xenografted with MCL cell lines JEKO-1 and HBL-2, and when tumor diameters reached 3cm in any size, the mice were sacrificed, and the excized tumors subjected to immunohistochemical (IHC) analysis. Alternatively, ex vivo obtained MCL cells were magnetically sorted using CD45 microbeads, and subjected to gene expression and flow cytometry analyses compared to the in vitro growing controls.IHC analysis proved that the tumors were neovascularized. Gene expression profiling by TaqMan Human Angiogenesis Array revealed that the most upregulated gene in both JEKO-1 and HBL-2 in vivo vs. in vitro growing cells was platelet/endothelial cell adhesion molecule CD31/PECAM-1 (fold change 148.9 ± 19.4, and 127.6 ± 10.5, respectively). Recently, Boyd et al. reported upregulation of CD31 in three of five primary MCL samples compared to normal B cells by Western blotting. By flow cytometry we assessed surface expression of CD31 on primary cells obtained from peripheral blood and bone marrow of 25 MCL patients before therapy. The percentage of CD31 positive cells was significantly higher in the subset of CD19+CD5+ peripheral blood MCL cells compared to CD19+CD5+ healthy donor B-cells (78.6± 4.4 vs. 14.7±2.6, p< 0.001), as well as in the subset of CD19+CD5+ bone marrow MCL cells compared to CD19+CD5+ B-cells obtained from the bone marrow of patients with various lymphoma subtypes with no detectable bone marrow involvement (81.9±3.9 vs. 20.5±4.8, p< 0.0001).In addition to surface CD31 we asked if patients with MCL have increased levels of soluble form of CD31 (sCD31) compared to healthy volunteers. We measured concentrations of sCD31 in plasma samples obtained from 17 MCL patients before therapy by ELISA. Despite the fact that MCL patients demonstrated higher variability in sCD31 concentrations (range 10.7–135.6 ng/ml) compared to healthy volunteers (range 43.3– 92.0 ng/ml), the medians were not statistically different (56.4 vs. 53.3 ng/ml). We also measured concentrations of sCD31 in plasma of two patients with MCL before treatment and after three cycles of chemotherapy, and found that the post-chemotherapy levels of sCD31 were lower in both patients (91.8 vs. 60.7 ng/ml; 56.4 vs. 30.4 ng/ml).To investigate the role of CD31 in the biology of MCL we derived JEKO-1 and HBL-2 clones with stable downregulation of CD31 by siRNA approach. In addition, two JEKO-1 subclones with upregulated CD31 were established by limiting dilution from the original cell line (=controls). The limiting dilution approach was not feasible in HBL-2 cells, which completely lack CD31 expression. While HBL-2 clones with downregulated CD31 engrafted constantly, JEKO-1 clones with downregulated CD31 engrafted only in 2 out of 8 mice. Growth of the tumors derived from both HBL-2 and JEKO-1 clones with downregulated CD31 was significantly slower compared to that of control tumors (HBL-2: 2.1±0.4 g versus 4.1±0.2 g, p=0.002; JEKO-1: 0.5±0.1 g versus 2.2±0.2 g, p=0.0019). Xenotransplantation of JEKO-1 clones with upregulated CD31 resulted in accelerated tumor growth compared to controls (3.4±0.2 g versus 2.2±0.2 g, p=0.0027). Importantly, the in vitro proliferation rate between the clones with changed CD31 expression and the original cell lines were not statistically different suggesting that the different growth pattern of tumors was a consequence of altered interaction between the tumor cells and the murine microenvironment.In summary, CD31/PECAM-1 antigen is overexpressed on primary CD19+CD5+ MCL cells obtained from the peripheral blood and bone marrow of MCL patients before therapy compared to control CD19+CD5+ B-cells. The upregulated CD31/PECAM-1 appears to play important role in MCL biology, and might represent potential druggable target.Financial Support: IGA-MZ NT13201-4/2012, GAUK 259211/110709, GAUK 446211, UNCE 204021, PRVOUK P24/LF1/3, PRVOUK 1–5101–280002 PVK, SVV-2012–254260507 Disclosures:No relevant conflicts of interest to declare.