New molecular targets in mantle cell lymphoma

The extracts from centaurea species abolished the cytotoxic effects of doxorubicin on breast cancer cell line - MCF-7 and bortezomib on prostate cancer cell line- PC3

The use of plant extracts by cancer patients during chemotherapy poses potential risks, as they may reduce the effectiveness of treatment or interact negatively with chemotherapeutic drugs. There is a lack of comprehensive studies evaluating the effects of various Centaurea spp. plant extracts on chemotherapy outcomes, highlighting the need for caution and medical supervision. Therefore, the aim of this study was to evaluate the effects of five Centaurea spp. extracts in concentrations of 125 μg/ml and 250 μg/ml on the cytotoxicity induced by doxorubicin (DOX, 1 μM) in MCF-7 breast cancer cells and by bortezomib (BOR, 7 nM) in PC-3 prostate cancer cells. Selected cell lines were treated with drugs and extracts or combined for 48 h. Biological assays revealed that four out of five tested extracts abolished the cytotoxic effects of DOX and BOR. The extracts showed low antioxidant activity compared to Trolox, with no correlation to total compound content, indicating the abolition of the cytotoxic effect was not due to antioxidant activity. However, genotoxicity and DNA damage response studies showed a protective effect of the extract on the DNA of cancer cells and upregulation of DNA repair, which may underlie the reversal of the chemotherapy effect.

p53 directly downregulates the expression of CDC20 to exert anti-tumor activity in mantle cell lymphoma

BACKGROUND

Cell cycle dysregulation characterized by cyclin D1 overexpression is common in mantle cell lymphoma (MCL), while mitotic disorder was less studied. Cell division cycle 20 homologue (CDC20), an essential mitotic regulator, was highly expressed in various tumors. Another common abnormality in MCL is p53 inactivation. Little was known about the role of CDC20 in MCL tumorigenesis and the regulatory relationship between p53 and CDC20 in MCL.

METHODS

CDC20 expression was detected in MCL patients and MCL cell lines harboring mutant p53 (Jeko and Mino cells) and wild-type p53 (Z138 and JVM2 cells). Z138 and JVM2 cells were treated with CDC20 inhibitor apcin, p53 agonist nutlin-3a, or in combination, and then cell proliferation, cell apoptosis, cell cycle, cell migration and invasion were determined by CCK-8, flow cytometry and Transwell assays. The regulatory mechanism between p53 and CDC20 was revealed by dual-luciferase reporter gene assay and CUT&Tag technology. The anti-tumor effect, safety and tolerability of nutlin-3a and apcin were investigated in vivo in the Z138-driven xenograft tumor model.

RESULTS

CDC20 was overexpressed in MCL patients and cell lines compared with their respective controls. The typical immunohistochemical marker of MCL patients, cyclin D1, was positively correlated with CDC20 expression. CDC20 high expression indicated unfavorable clinicopathological features and poor prognosis in MCL patients. In Z138 and JVM2 cells, either apcin or nutlin-3a treatment could inhibit cell proliferation, migration and invasion, and induce cell apoptosis and cell cycle arrest. GEO analysis, RT-qPCR and WB results showed that p53 expression was negatively correlated with CDC20 expression in MCL patients, Z138 and JVM2 cells, while this relationship was not observed in p53-mutant cells. Dual-luciferase reporter gene assay and CUT&Tag assay revealed mechanistically that CDC20 was transcriptionally repressed by p53 through directly binding p53 to CDC20 promoter from - 492 to + 101 bp. Moreover, combined treatment of nutlin-3a and apcin showed better anti-tumor effect than single treatment in Z138 and JVM2 cells. Administration of nutlin-3a/apcin alone or in combination confirmed their efficacy and safety in tumor-bearing mice.

CONCLUSIONS

Our study validates the essential role of p53 and CDC20 in MCL tumorigenesis, and provides a new insight for MCL therapeutics through dual-targeting p53 and CDC20.

HSP90 Inhibitor Ganetespib Enhances the Sensitivity of Mantle Cell Lymphoma to Bruton’s Tyrosine Kinase Inhibitor Ibrutinib

Mantle cell lymphoma (MCL) is a highly aggressive and heterogeneous B-cell lymphoma. Though Bruton’s tyrosine kinase (BTK) inhibitor ibrutinib has shown great efficacy as a single agent for MCL treatment, the real-world use of ibrutinib is still subject to limitations. Our previous study has shown the treatment with HSP90 inhibitor ganetespib can attack major targets of MCL, luckily complementary to ibrutinib’s targets. In this study, transient ganetespib treatment sensitizes MCL cells to ibrutinib as manifested by the significant decrease of IC50 values, percentages of EdU (5-Ethynyl-2′-deoxyuridine) positive cells, and levels of p-AKT and NF-κB after combinational treatment. Additionally, pretreatment with ganetespib enhanced cell cycle arrest induced by ibrutinib at G0/G1 phase and significantly decreased levels of cell cycle promoting proteins CDK2, 4, and 6. Pretreatment with ganetespib also enhanced cell apoptosis induced by ibrutinib through the upregulation of cleaved-caspase 9 and downregulation of BCL-2 in MCL cells at the molecular level. The sequential administration of ganetespib and ibrutinib had similar effects on increasing DNA damage as the transient treatment with ganetespib as demonstrated by the improved percentage of γH2AX and 53BP1 foci. Furthermore, ganetespib significantly increased inhibition of tumor growth mediated by ibrutinib in vivo, confirmed by the changes of the expression levels of Ki-67 and BCL-2 through immunohistochemistry assays. This study indicates that HSP90 inhibitor ganetespib maybe ideal for the combinational use with BTK inhibitor ibrutinib to target major pathogenesis-associated signaling pathways for MCL treatment which may help identify new possibilities for clinical trials.

Modulation of Cellular Redox Parameters for Improving Therapeutic Responses in Multiple Myeloma

Raised oxidative stress and abnormal redox status are typical features of multiple myeloma cells, and the identification of the intimate mechanisms that regulate the relationships between neoplastic cells and redox homeostasis may reveal possible new anti-myeloma therapeutic targets to increase the effectiveness of anti-myeloma drugs synergistically or to eradicate drug-resistant clones while reducing toxicity toward normal cells. An alteration of the oxidative state is not only responsible for the onset of multiple myeloma and its progression, but it also appears essential for the therapeutic response and for developing any chemoresistance. Our review aimed to evaluate the literature’s current data on the effects of oxidative stress on the response to drugs generally employed in the therapy of multiple myeloma, such as proteasome inhibitors, immunomodulators, and autologous transplantation. In the second part of the review, we analyzed the possibility of using other substances, often of natural origin, to modulate the oxidative stress to interfere with the progression of myelomatous disease.

Specific targeting of the KRAS mutational landscape in myeloma as a tool to unveil the elicited antitumor activity

Alterations in KRAS have been identified as the most recurring somatic variants in the multiple myeloma (MM) mutational landscape. Combining DNA and RNA sequencing, we studied 756 patients and observed KRAS as the most frequently mutated gene in patients at diagnosis; in addition, we demonstrated the persistence or de novo occurrence of the KRAS aberration at disease relapse. Small-molecule inhibitors targeting KRAS have been developed; however, they are selective for tumors carrying the KRASG12C mutation. Therefore, there is still a need to develop novel therapeutic approaches to target the KRAS mutational events found in other tumor types, including MM. We used AZD4785, a potent and selective antisense oligonucleotide that selectively targets and downregulates all KRAS isoforms, as a tool to dissect the functional sequelae secondary to KRAS silencing in MM within the context of the bone marrow niche and demonstrated its ability to significantly silence KRAS, leading to inhibition of MM tumor growth, both in vitro and in vivo, and confirming KRAS as a driver and therapeutic target in MM.

SOX11 Inhibitors Are Cytotoxic in Mantle Cell Lymphoma

PURPOSE

Mantle cell lymphoma (MCL) is a fatal subtype of non-Hodgkin lymphoma. SOX11 transcription factor is overexpressed in the majority of nodal MCL. We have previously reported that B cell-specific overexpression of SOX11 promotes MCL pathogenesis via critically increasing BCR signaling in vivo. SOX11 is an attractive target for MCL therapy; however, no small-molecule inhibitor of SOX11 has been identified to date. Although transcription factors are generally considered undruggable, the ability of SOX11 to bind to the minor groove of DNA led us to hypothesize that there may exist cavities at the protein-DNA interface that are amenable to targeting by small molecules.

EXPERIMENTAL DESIGN

Using a combination of in silico predictions and experimental validations, we report here the discovery of three structurally related compounds (SOX11i) that bind SOX11, perturb its interaction with DNA, and effect SOX11-specific anti-MCL cytotoxicity.

RESULTS

We find mechanistic validation of on-target activity of these SOX11i in the inhibition of BCR signaling and the transcriptional modulation of SOX11 target genes, specifically, in SOX11-expressing MCL cells. One of the three SOX11i exhibits relatively superior in vitro activity and displays cytotoxic synergy with ibrutinib in SOX11-expressing MCL cells. Importantly, this SOX11i induces cytotoxicity specifically in SOX11-positive ibrutinib-resistant MCL patient samples and inhibits Bruton tyrosine kinase phosphorylation in a xenograft mouse model derived from one of these subjects.

CONCLUSIONS

Taken together, our results provide a foundation for therapeutically targeting SOX11 in MCL by a novel class of small molecules.

HSP90 inhibition downregulates DNA replication and repair genes via E2F1 repression

Mantle cell lymphoma (MCL) is an especially aggressive and highly heterogeneous mature B-cell lymphoma. Heat shock protein 90 (HSP90) is considered an attractive therapeutic target in a variety of cancers, including MCL, but no HSP90 inhibitors have succeeded in the clinical trials to date. Exploring fine mechanisms of HSP90 inhibition in cancer cells may shed light on novel therapeutic strategies. Here, we found that HSP90 knockdown and continuous inhibition with ganetespib inhibited growth of MCL cells in vitro and in vivo. To our surprise, transient exposure over 12 h was almost as efficient as continuous exposure, and treatment with ganetespib for 12 h efficiently inhibited growth and induced G1 cell cycle arrest and apoptosis of MCL cells. Transcriptome analysis complemented by functional studies was performed to define critical MCL signaling pathways that are exceptionally sensitive to HSP90 inhibition and vital to cell fate. Six genes (cell division cycle 6, cell division cycle 45, minichromosome maintenance 4, minichromosome maintenance 7, RecQ-mediated genome instability 2, and DNA primase polypeptide 1) involved in DNA replication and repair were identified as consistently downregulated in three MCL cell lines after transient ganetespib treatment. E2F1, an important transcription factor essential for cell cycle progression, was identified as a ganetespib target mediating transcriptional downregulation of these six genes, and its stability was also demonstrated to be maintained by HSP90. This study identifies E2F1 as a novel client protein of HSP90 that is very sensitive and worthy of targeting and also finds that HSP90 inhibitors may be useful in combination therapies for MCL.

A Rare Manifestation of a Rare Disease: Mantle Cell Lymphoma Presenting With Aseptic Meningitis

Mantle cell lymphoma (MCL) is a rare form of non-Hodgkin lymphoma characterized by clonal proliferation of follicular mantle zone B lymphocytes. It is caused by abnormal chromosomal translocation t(11;14) resulting in aberrant expression of cyclin D1. This leads to activation of anti-apoptotic pathways and abnormal proliferation of MCL cells. Patients can present with an indolent course or a fulminant disease with short overall survival. The disease frequently involves extranodal organs, but rarely manifests with neurological symptoms. We report a rare case of aberrant CD5-negative MCL presenting with aseptic meningitis.

The Role of Macrophage/B-Cell Interactions in the Pathophysiology of B-Cell Lymphomas

Macrophages (MPs) are heterogeneous, multifunctional, myeloid-derived leukocytes that are part of the innate immune system, playing wide-ranging critical roles in basic biological activities, including maintenance of tissue homeostasis involving clearance of microbial pathogens. Tumor-associated MPs (TAMs) are MPs with defined specific M2 phenotypes now known to play central roles in the pathophysiology of a wide spectrum of malignant neoplasms. Also, TAMs are often intrinsic cellular components of the essential tumor microenvironment (TME). In concert with lymphoid-lineage B and T cells at various developmental stages, TAMs can mediate enhanced tumor progression, often leading to poor clinical prognosis, at least partly through secretion of chemokines, cytokines, and various active proteases shown to stimulate tumor growth, angiogenesis, metastasis, and immunosuppression. Researchers recently showed that TAMs express certain key checkpoint-associated proteins [e.g., programmed cell death protein 1 (PD-1), programmed cell death-ligand 1 (PD-L1)] that appear to be involved in T-cell activation and that these proteins are targets of other specific checkpoint-blocking immunotherapies (anti-PD-1/PD-L1) currently part of new therapeutic paradigms for chemotherapy-resistant neoplasms. Although much is known about the wide spectrum and flexibility of MPs under many normal and neoplastic conditions, relatively little is known about the increasingly important interactions between MPs and B-lymphoid cells, particularly in the TME in patients with aggressive B-cell non-Hodgkin lymphoma (NHL-B). Normal and neoplastic lymphoid and myeloid cell/MP lineages appear to share many primitive cellular characteristics as well as transcriptional factor interactions in human and animal ontogenic studies. Such cells are capable of ectopic transcription factor-induced lineage reprogramming or transdifferentiation from early myeloid/monocytic lineages to later induce B-cell lymphomagenesis in experimental in vivo murine systems. Close cellular interactions between endogenous clonal neoplastic B cells and related aberrant myeloid precursor cells/MPs appear to be important interactive components of aggressive NHL-B that we discuss herein in the larger context of the putative role of B-cell/MP cellular lineage interactions involved in NHL-B pathophysiology during ensuing lymphoma development.

BET protein proteolysis targeting chimera (PROTAC) exerts potent lethal activity against mantle cell lymphoma cells

Bromodomain extraterminal protein (BETP) inhibitors transcriptionally repress oncoproteins and nuclear factor-κB (NF-κB) target genes that undermines the growth and survival of mantle cell lymphoma (MCL) cells. However, BET bromodomain inhibitor (BETi) treatment causes accumulation of BETPs, associated with reversible binding and incomplete inhibition of BRD4 that potentially compromises the activity of BETi in MCL cells. Unlike BETi, BET-PROTACs (proteolysis-targeting chimera) ARV-825 and ARV-771 (Arvinas, Inc.) recruit and utilize an E3-ubiquitin ligase to effectively degrade BETPs in MCL cells. BET-PROTACs induce more apoptosis than BETi of MCL cells, including those resistant to ibrutinib. BET-PROTAC treatment induced more perturbations in the mRNA and protein expressions than BETi, with depletion of c-Myc, CDK4, cyclin D1 and the NF-κB transcriptional targets Bcl-xL, XIAP and BTK, while inducing the levels of HEXIM1, NOXA and CDKN1A/p21. Treatment with ARV-771, which possesses superior pharmacological properties compared with ARV-825, inhibited the in vivo growth and induced greater survival improvement than the BETi OTX015 of immune-depleted mice engrafted with MCL cells. Cotreatment of ARV-771 with ibrutinib or the BCL2 antagonist venetoclax or CDK4/6 inhibitor palbociclib synergistically induced apoptosis of MCL cells. These studies highlight promising and superior preclinical activity of BET-PROTAC than BETi, requiring further in vivo evaluation of BET-PROTAC as a therapy for ibrutinib-sensitive or -resistant MCL.

Phase II Study of Bortezomib in Combination with Cyclophosphamide and Rituximab for Relapsed or Refractory Mantle Cell Lymphoma

BACKGROUND

Relapsed or refractory mantle cell lymphoma (MCL) has a poor prognosis. The best outcome is achieved in patients who have a partial or complete response to salvage treatment and proceed to allogeneic stem cell transplant.

PATIENTS AND METHODS

Twenty-one patients were given a combination regimen of bortezomib, cyclophosphamide, and rituximab at MD Anderson Cancer Center as part of a single-arm, prospective, open-label phase II clinical trial. The median age was 66 years, with a median number of prior treatments of three. Sixty-seven percent had failed intensive chemoimmunotherapy and 43% were intermediate/high risk according to the MCL international prognostic index score, with a median Ki-67 proliferation index of 45% in those who were tested.

RESULTS

The rates of overall and complete response achieved were 74% and 42%, respectively, with median progression-free and overall survivals of 9 months and 36.4 months, respectively. The regimen's toxicity profile was acceptable; only 25% of the cycles resulted in grade 3 or 4 neutropenia or thrombocytopenia, and only 3% of cycles produced grade 3-4 fatigue. There were no episodes of grade 3-4 neuropathy.

CONCLUSION

The combination of bortezomib with cyclophosphamide and rituximab is an effective and well-tolerated regimen in patients with relapsed/refractory MCL. Because of its low toxicity, future combinations of this regimen with other promising drugs that have different mechanisms of action offer a realistic possibility that may improve outcomes for patients who have MCL. The Oncologist 2017;22:549-553 IMPLICATIONS FOR PRACTICE: The combination of bortezomib with cyclophosphamide and rituximab represents an additional effective novel salvage regimen for mantle cell lymphoma. This combination adds to the growing list of treatment options available for patients with mantle cell lymphoma.

ZGDHu-1 promotes apoptosis of mantle cell lymphoma cells

Mantle cell lymphoma (MCL) is a well-defined aggressive Non-Hodgkin-lymphoma with short survival rates and remains incurable to date. Previously, we demonstrated the antitumor activity of ZGDHu-1(N, N'-di-(m-methylphenyi)-3, 6-dimethyl-1, 4-dihydro-1, 2, 4, 5-tetrazine-1, 4-dicarboamide) in chronic lymphocytic leukemia. In this study, ZGDHu-1 shows potent anti-lymphoma activity in MCL cells. ZGDHu-1 significantly induces cell cycle G2/M phase arrest and apoptosis in MCL cells. ZGDHu-1 reduces the protein levels of Mcl-1, Bcl-XL and cyclin D1. Importantly, ZGDHu-1 inhibits TNFα-induced IkBa phosphorylation, p65 nuclear translocation and NF-kB downstream target gene expression in MCL cells. MCL samples expressing high levels of Bcl-2 and high Bcl-2/Bax ratios tend to be less effective to ZGDHu-1. Together, these results suggest that ZGDHu-1 could inhibit the NF-kB signaling pathway partly, which may lead to the suppression of cell proliferation and the induction of apoptosis in MCL cells. Thus, our studies provide evidence of the potential of ZGDHu-1 in treating mantle cell lymphoma.

Modulation of p73 isoforms expression induces anti-proliferative and pro-apoptotic activity in mantle cell lymphoma independent of p53 status

Mantle cell lymphoma (MCL) is characterized by a clinically aggressive course with frequent relapse and poor survival. The p53 pathway is frequently dysregulated and p53 status predicts clinical outcome. In this report, we investigated whether modulation of p73 isoforms by diclofenac inhibits cell growth, induces apoptosis and/or cell cycle arrest in MCL relative to p53 status. Wild-type p53 [Granta-519 and JVM-2], mutant p53 [Jeko-1 and Mino-1] expressing cells, therapy resistant cell lines, and primary human cells isolated from MCL patients were used. Overexpression of pro-apoptotic TAp73 enhanced MCL cell apoptosis. Diclofenac induced a concentration- and duration-dependent increase in TAp73, cell cycle arrest, cell death, and inhibited MCL cell growth independent of p53 status. Diclofenac treatment was associated with increased activity of caspases 3, 7, and 8 and induction of p53 transcriptional target genes. These studies demonstrate the potential for diclofenac as novel therapeutic agent in MCL independent of p53 status.

Bortezomib, Ifosfamide, Carboplatin, and Etoposide in a Patient with HIV-Negative Relapsed Plasmablastic Lymphoma

Plasmablastic lymphoma (PBL) is a rare subtype of diffuse large B cell lymphoma (DLBCL), often associated with HIV infection. We present a case of a 53-year-old HIV-negative man with untreated hepatitis C viral infection who presented with abdominal pain and lymphadenopathy. Lymph node and bone marrow biopsies were consistent with plasmablastic lymphoma. He had partial response (PR) to 6 cycles of EPOCH but disease progressed seven weeks later. Repeat biopsy was consistent with plasmablastic lymphoma. Three cycles of bortezomib, ifosfamide, carboplatin, and etoposide (B-ICE) chemotherapy resulted in a partial response (PR). Five months later, he presented with widespread lymphadenopathy and tumor lysis syndrome with circulating blasts. Flow cytometry revealed a different population of lymphoma cells, this time positive for CD5, CD19, CD20, and CD22, with dim expression of CD45 and CD38. The patient died on the first day of ESHAP chemotherapy. There are no treatment recommendations or standard of care for plasmablastic lymphoma. A literature search yielded 10 cases in which bortezomib was administered in either HIV-positive or HIV-negative PBL. Six reported a partial response, 3 reported a complete response, and 1 was a near-complete response. Bortezomib, in combination with chemotherapy, may be an effective treatment option in PBL as reported here.

Bcl-2high mantle cell lymphoma cells are sensitized to acadesine with ABT-199

Acadesine is a nucleoside analogue with known activity against B-cell malignancies. Herein, we showed that in mantle cell lymphoma (MCL) cells acadesine induced caspase-dependent apoptosis through turning on the mitochondrial apoptotic machinery. At the molecular level, the compound triggered the activation of the AMPK pathway, consequently modulating known downstream targets, such as mTOR and the cell motility-related vasodilator-stimulated phosphoprotein (VASP). VASP phosphorylation by acadesine was concomitant with a blockade of CXCL12-induced migration. The inhibition of the mTOR cascade by acadesine, committed MCL cells to enter in apoptosis by a translational downregulation of the antiapoptotic Mcl-1 protein. In contrast, Bcl-2 protein levels were unaffected by acadesine and MCL samples expressing high levels of Bcl-2 tended to have a reduced response to the drug. Targeting Bcl-2 with the selective BH3-mimetic agent ABT-199 sensitized Bcl-2 high MCL cells to acadesine. This effect was validated in vivo, where the combination of both agents displayed a more marked inhibition of tumor outgrowth than each drug alone. These findings support the notions that antiapoptotic proteins of the Bcl-2 family regulate MCL cell sensitivity to acadesine and that the combination of this agent with Bcl-2 inhibitors might be an interesting therapeutic option to treat MCL patients.

Oxidative stress and proteasome inhibitors in multiple myeloma

Multiple myeloma is a form of plasma cell neoplasm that accounts for approximately 10% of all hematological malignancies. Recently, several novel drugs have been discovered that almost doubled the overall survival of multiple myeloma patients. One of these drugs, the first-in-class proteasome inhibitor bortezomib (Velcade) has demonstrated remarkable response rates in multiple myeloma patients, and yet, currently this disease remains incurable. The major factor undermining the success of multiple myeloma treatment is a rapidly emerging resistance to the available therapy. Thus, the development of stand-alone or adjuvant anti-myeloma agents becomes of paramount importance. Overproduction of intracellular reactive oxygen species (ROS) often accompanies malignant transformation due to oncogene activation and/or enhanced metabolism in tumor cells. As a result, these cells possess higher levels of ROS and lower levels of antioxidant molecules compared to their normal counterparts. Unbalanced production of ROS leads to oxidative stress which, if left unchecked, could be toxic for the cell. In multiple myeloma cells where high rates of immunoglobulin synthesis is an additional factor contributing to overproduction of ROS, further induction of oxidative stress can be an effective strategy to cope with this disease. Here we will review the available data on the role of oxidative stress in the cytotoxicity of proteasome inhibitors and the use of ROS-inducing compounds as anti-myeloma agents.

Novel agents in mantle cell lymphoma

Mantle cell lymphoma (MCL) is an uncommon B-cell non-Hodgkin lymphoma, comprising approximately 6-8% of all non-Hodgkin lymphomas. MCL is biologically and clinically heterogeneous, and there is no standard treatment for MCL. Although untreated MCL often responds well to frontline combination chemotherapy, relapsed, refractory MCL can be challenging to treat and traditional cytotoxic chemotherapy is typically not highly effective. In recent years, increased insight into the molecular and genomic diversity of MCL and the pathogenesis of the disease has given rise to the development of many new biologically targeted therapies. Ibrutinib was recently FDA approved for relapsed, refractory MCL and will likely have a significant impact on treatment paradigms for MCL. In addition to ibrutinib, there are many classes of novel agents that are currently in development. This review focuses on recent developments in the management of relapsed, refractory MCL, describing the growing armamentarium of novel agents available to combat this disease.

Arsenic trioxide rewires mantle cell lymphoma response to bortezomib

Although most of the mantle cell lymphoma (MCL) patients initially responded well to bortezomib (BTZ), the dose-dependent toxicities have greatly limited the application of BTZ to MCL. To investigate the efficacy and mechanism of arsenic trioxide (ATO) with BTZ in inducing apoptosis of MCL cells, two MCL cell lines, along with primary cells from MCL patients (n = 4), were used. Additionally, the NOD-SCID mice xenograft model of Jeko-1 cells was established to study the anti-MCL mechanisms in an in vivo setting. ATO treatment highly improved BTZ capacity to inhibit proliferation and induce apoptosis of MCL cells. Furthermore, the interaction of Noxa and Mcl-1 leads Bak to release from Mcl-1 or from Bcl-xl, which could further activate Bak and Bax and then induce cell apoptosis. We also found that when lower doses of BTZ were used in combination with ATO, more effective proapoptotic effects in both the cell lines and the primary cells were obtained compared to the effects of BTZ used alone at higher doses. Simultaneously, the combination of these two drugs delayed the tumor growth in mice more effectively than BTZ alone. The cooperative anti-MCL effects of this combination therapy both in vitro and in vivo strongly provided a new strategy to the clinical treatment of MCL.

Dual inhibition of CDK4/Rb and PI3K/AKT/mTOR pathways by ON123300 induces synthetic lethality in mantle cell lymphomas

This study describes the characterization of a novel kinase inhibitor, ON123300, which inhibits CDK4/6 and PI3K-δ and exhibits potent activity against mantle cell lymphomas (MCLs) both in vitro and in vivo. We examined the effects of PD0332991 and ON 123300 on cell cycle progression, modulation of the Rb and PI3K/AKT pathways, and the induction of apoptosis in MCL cell lines and patient-derived samples. When Granta 519 and Z138C cells were incubated with PD0332991 and ON123300, both compounds were equally efficient in their ability to inhibit the phosphorylation of Rb family proteins. However, only ON123300 inhibited the phosphorylation of proteins associated with the PI3K/AKT pathway. Cells treated with PD0332991 rapidly accumulated in the G₀/G₁ phase of cell cycle as a function of increasing concentration. Although ON123300-treated cells arrested similarly at lower concentrations, higher concentrations resulted in the induction of apoptosis, which was not observed in PD 0332991-treated samples. Mouse xenograft assays also showed a strong inhibition of MCL tumor growth in ON123300-treated animals. Finally, treatment of ibrutinib-sensitive and resistant patient-derived MCLs with ON123300 also triggered apoptosis and inhibition of the Rb and PI3K/AKT pathways, suggesting that this compound might be an effective agent in MCL, including ibrutinib-resistant forms of the disease.

The STAT3 inhibitor WP1066 synergizes with vorinostat to induce apoptosis of mantle cell lymphoma cells

Mantle cell lymphoma (MCL) is an aggressive B-cell non-Hodgkin lymphoma (NHL) characterized by the translocation t (11; 14) (q13; q32). Drug resistance remains a formidable obstacle to treatment and the median survival for MCL patients is between 3 and 5 years. Thus, there is an urgent need to discover novel approaches to MCL therapy. The signal transducer and activation of transcription 3 (STAT3) has been found to be constitutively activated in several subtypes of MCL cell lines and MCL tumors. WP1066, a small-molecule inhibitor of STAT3, exerted antitumor activity in hematological and solid malignancies by inhibiting key survival and growth signaling pathways. In the present study, we evaluated the antiproliferative and proapoptotic activity of WP1066 combined with pan-histone deacetylase (HDAC) inhibitor vorinostat (SAHA) in a panel of MCL cell lines. In addition, potential mechanisms involved were also explored. The outcome showed that combination of WP1066 with SAHA resulted in synergistic growth inhibition and apoptosis induction in MCL cell lines in vitro. Furthermore, combination of WP1066 with SAHA inhibited the constitutive STAT3 activation and modulated mRNA expressions of anti- and pro-apoptotic genes. Our findings suggest that agents targeting the STAT3 pathway such as WP1066 may be useful therapeutic drugs for MCL when combined with SAHA.

Perturbations of the endocannabinoid system in mantle cell lymphoma: correlations to clinical and pathological features

The cannabinoid receptors are upregulated in many types of cancers, including mantle cell lymphoma (MCL) and have been suggested to constitute novel therapeutic targets. The expression pattern of the key members of the endocannabinoid system was analyzed in a well-characterized MCL patient cohort and correlated to biological features. 107 tumor tissues were analyzed for the mRNA levels of cannabinoid receptors 1 and 2 (CNR1 and CNR2) and the two main enzymes regulating the endocannabinoid anandamide levels in tissue: NAPEPLD and FAAH (participating in synthesis and degradation, respectively). NAPEPLD, CNR1 and CNR2 were overexpressed while FAAH expression was reduced in MCL compared to non-malignant B-cells. Both low CNR1 and high FAAH levels correlated with lymphocytosis (p=0.016 and p=0.022, respectively) and with leukocytosis (p=0.0018 and p=0.047). Weak to moderate CNR1 levels were a feature of SOX11 negative MCL (p=0.006). Both high CNR2 and high FAAH levels correlated to anemia (p=0.0006 and p=0.038, respectively). In conclusion, the relative expression of the anandamide synthesizing and metabolizing enzymes in MCL is heavily perturbed. This finding, together with high expression of cannabinoid receptors, could favor enhanced anandamide signaling and suggest that targeting the endocannabinoid system might be considered as part of lymphoma therapy.

Characterization of ibrutinib-sensitive and -resistant mantle lymphoma cells

Ibrutinib inhibits Bruton tyrosine kinase (BTK), a key component of early B-cell receptor (BCR) signalling pathways. A multicentre phase 2 trial of ibrutinib in patients with relapsed/refractory mantle cell lymphoma (MCL) demonstrated a remarkable response rate. However, approximately one-third of patients have primary resistance to the drug while other patients appear to lose response and develop secondary resistance. Understanding the molecular mechanisms underlying ibrutinib sensitivity is of paramount importance. In this study, we investigated cell lines and primary MCL cells that display differential sensitivity to ibrutinib. We found that the primary cells display a higher BTK activity than normal B cells and MCL cells show differential sensitivity to BTK inhibition. Genetic knockdown of BTK inhibits the growth, survival and proliferation of ibrutinib-sensitive but not resistant MCL cell lines, suggesting that ibrutinib acts through BTK to produce its anti-tumour activities. Interestingly, inhibition of ERK1/2 and AKT, but not BTK phosphorylation per se, correlates well with cellular response to BTK inhibition in cell lines as well as in primary tumours. Our study suggests that, to prevent primary resistance or to overcome secondary resistance to BTK inhibition, a combinatory strategy that targets multiple components or multiple pathways may represent the most effective approach.

A novel melphalan polymeric prodrug: preparation and property study

The clinical application of melphalan (Me), an anticancer drug for the treatment of hematologic malignancies, has been limited due to its poor water solubility, rapid elimination and lack of target specificity. To solve these problems, O,N-carboxymethyl chitosan-peptide-melphalan conjugates were synthesized and characterized. All polymeric prodrugs showed satisfactory water solubility. It was found that the molecular weight of O,N-carboxymethyl chitosan (O,N-CMCS) and the peptide spacer played a crucial role in controlling the drug content, diameter and drug release properties of O,N-carboxymethyl chitosan-peptide-melphalan conjugates. The studies of in vitro drug release and cell cytotoxicity by MTT assay revealed that, employing the polymeric conjugation strategy and using the peptides glycylglycine (Gly-Gly) as a spacer, the conjugates have good cathepsin X-sensitivity and lower toxicity and the drug release behavior improved remarkably. In conclusion, O,N-carboxymethyl chitosan-peptide-melphalan conjugates could be promising prodrugs for anticancer application.

Involvement of tumor-associated macrophage activation in vitro during development of a novel mantle cell lymphoma cell line, PF-1, derived from a typical patient with relapsed disease

Human mantle cell lymphoma (MCL) cell lines are scarce and have been only sporadically described and validated, and only a few have been thoroughly molecularly or genetically characterized. We describe here the successful establishment of a new MCL line, PF-1, with typical MCL characteristics. Culturing primary MCL cells in vitro initially gave rise to an essential generative microenvironment "niche" involving macrophages required for MCL growth, and eventually produced the PF-1 MCL cell line. Our analysis revealed that PF-1 is morphologically and genotypically nearly identical to the original tumor cells. The PF-1 MCL cell line that we have developed will be useful for in vitro and in vivo studies of MCL pathogenesis and therapeutics.

B-cell activating factor-receptor specific activation of tumor necrosis factor receptor associated factor 6 and the phosphatidyl inositol 3-kinase pathway in lymphoma B cells

B-cell activating factor-receptor (BAFF-R) is the primary BAFF receptor that is responsible for promoting B-cell development and survival. Malignant B-cells exploit the BAFF/BAFF-R system, and high serum BAFF levels or genetic alterations in BAFF receptors have been found in B-cell cancers. BAFF signaling impacts pro-survival pathways. However, other than nuclear factor-κB2 (NF-κB2), little is known about the specific pathways activated by individual BAFF receptors. Using a novel BAFF-R expression model we have demonstrated that activation of BAFF-R, independent of transmembrane activator and cytophilin ligand interactor (TACI) and B-cell maturation antigen (BCMA), can induce phosphorylation of Akt and glycogen synthase kinase 3β (GSK3β). Expression of an activated form of BAFF-R also enhanced a pro-survival gene expression pattern, including the novel BAFF-regulated gene Pin1, whose expression was phosphatidyl inositol 3-kinase (PI3K)-dependent. Additionally, we showed that TRAF6 is essential for mediating BAFF-R dependent activation of Akt. Together these data describe a novel role for TRAF6 in BAFF-R-specific activation of the PI3K pathway and provide evidence suggesting a new role for Pin1 in BAFF-R signaling.

Egress of CD19(+)CD5(+) cells into peripheral blood following treatment with the Bruton tyrosine kinase inhibitor ibrutinib in mantle cell lymphoma patients

Ibrutinib (PCI-32765) is a highly potent oral Bruton tyrosine kinase (BTK) inhibitor in clinical development for treating B-cell lymphoproliferative diseases. Patients with chronic lymphocytic leukemia (CLL) often show marked, transient increases of circulating CLL cells following ibrutinib treatments, as seen with other inhibitors of the B-cell receptor (BCR) pathway. In a phase 1 study of ibrutinib, we noted similar effects in patients with mantle cell lymphoma (MCL). Here, we characterize the patterns and phenotypes of cells mobilized among patients with MCL and further investigate the mechanism of this effect. Peripheral blood CD19(+)CD5(+) cells from MCL patients were found to have significant reduction in the expression of CXCR4, CD38, and Ki67 after 7 days of treatment. In addition, plasma chemokines such as CCL22, CCL4, and CXCL13 were reduced 40% to 60% after treatment. Mechanistically, ibrutinib inhibited BCR- and chemokine-mediated adhesion and chemotaxis of MCL cell lines and dose-dependently inhibited BCR, stromal cell, and CXCL12/CXCL13 stimulations of pBTK, pPLCγ2, pERK, or pAKT. Importantly, ibrutinib inhibited migration of MCL cells beneath stromal cells in coculture. We propose that BTK is essential for the homing of MCL cells into lymphoid tissues, and its inhibition results in an egress of malignant cells into peripheral blood. This trial was registered at www.clinicaltrials.gov as #NCT00114738.

Genome-wide methylation analyses identify a subset of mantle cell lymphoma with a high number of methylated CpGs and aggressive clinicopathological features

Mantle cell lymphoma (MCL) is a B-cell neoplasm with an aggressive clinical behavior characterized by the t(11;14)(q13;q32) and cyclin D1 overexpression. To clarify the potential contribution of altered DNA methylation in the development and/or progression of MCL, we performed genome-wide methylation profiling of a large cohort of primary MCL tumors (n = 132), MCL cell lines (n = 6) and normal lymphoid tissue samples (n = 31), using the Infinium HumanMethylation27 BeadChip. DNA methylation was compared to gene expression, chromosomal alterations and clinicopathological parameters. Primary MCL displayed a heterogeneous methylation pattern dominated by DNA hypomethylation when compared to normal lymphoid samples. A total of 454 hypermethylated and 875 hypomethylated genes were identified as differentially methylated in at least 10% of primary MCL. Annotation analysis of hypermethylated genes recognized WNT pathway inhibitors and several tumor suppressor genes as frequently methylated, and a substantial fraction of these genes (22%) showed a significant downregulation of their transcriptional levels. Furthermore, we identified a subset of tumors with extensive CpG methylation that had an increased proliferation signature, higher number of chromosomal alterations and poor prognosis. Our results suggest that a subset of MCL displays a dysregulation of DNA methylation characterized by the accumulation of CpG hypermethylation highly associated with increased proliferation that may influence the clinical behavior of the tumors.

Clinical efficacy and management of temsirolimus in patients with relapsed or refractory mantle cell lymphoma

Most patients with mantle cell lymphoma (MCL) relapse within a few years of treatment. Conventional agents provide little benefit, thus identification of new therapies is critical to improve patient outcomes. Temsirolimus, an inhibitor of mammalian target of rapamycin, is an effective, well-tolerated option authorized in Europe for treatment of patients with relapsed/refractory MCL. Intravenous temsirolimus has been extensively studied in MCL and has consistently demonstrated single-agent antitumor activity. In the pivotal phase III trial, treatment with temsirolimus 175 mg weekly for 3 weeks followed by 75 mg weekly (175/75 mg) resulted in significant improvements in progression-free survival (P = .0009) and objective response rate (P = .002) vs. investigator's choice of therapy. Hematologic toxicities (thrombocytopenia, neutropenia) were the principal grade 3/4 adverse events associated with temsirolimus 175/75 mg. Other toxicities included increases in serum cholesterol and triglycerides, hyperglycemia, fatigue, and dyspnea. Overall, the safety profile of temsirolimus is acceptable in this setting, and most toxicities are manageable with dose modification or medical intervention. Clinical studies of temsirolimus in relapsed or refractory MCL patients aim to clarify the optimal treatment schedule and to assess rational combinations with other therapeutic agents, such as rituximab or chemotherapy. Practical considerations are discussed for the clinical use of temsirolimus in patients with MCL.

Molecular pathogenesis of mantle cell lymphoma

Mantle cell lymphoma is a B cell malignancy in which constitutive dysregulation of cyclin D1 and the cell cycle, disruption of DNA damage response pathways, and activation of cell survival mechanisms contribute to oncogenesis. A small number of tumors lack cyclin D1 overexpression, suggesting that its dysregulation is always not required for tumor initiation. Some cases have hypermutated IGHV and stable karyotypes, a predominant nonnodal disease, and an indolent clinical evolution, which suggests that they may correspond to distinct subtypes of the disease. In this review, we discuss the molecular pathways that contribute to pathogenesis, and how improved understanding of these molecular mechanisms offers new perspectives for the treatment of patients.

Flipping the cyclin D1 switch in mantle cell lymphoma

Mantle cell lymphoma (MCL) is a rare, aggressive subtype of B cell NHL for which there is no standard of care. It is characterized by the t(11;14) translocation, implicating cyclin D1 (CCND1) in its pathogenesis. Cyclin D1 is one of a family of 3 unlinked D type cyclin genes, CCND1, 2, 3. CCND1 is not expressed in normal B cells. Deregulated expression occurs as a result of juxtaposition of cis IgH enhancer elements, Eμ and 3' Cα, to the cyclin D1 gene. These enhancer elements and regions upstream of the CCND1 gene are hypomethylated on the translocated allele. Histones surrounding the translocation have shown hyperacetylation as well, a hallmark of transcriptionally active chromatin. The t(11;14) translocation is an epigenetic event, leading to cyclin D1 deregulated transcription. These findings provide the rationale for the use of epigenetic and targeted cyclin D1 therapies to overcome resistance and induce durable remissions in MCL.

An overview of the mTOR pathway as a target in cancer therapy

INTRODUCTION

The mammalian target of rapamycin (mTOR) signaling cascade is a key regulatory pathway controlling initiation of mRNA translation in mammalian cells. The mTOR inhibitor rapamycin and its derivatives have shown potent antineoplastic activities in many preclinical models and clinical trials. First-generation mTOR inhibitors are now FDA-approved for the treatment of renal cell carcinoma.

AREAS COVERED

This article reviews the components of the mTOR pathway and their normal functions, highlighting the most common alterations in the pathway, seen in various human malignancies. It also discusses elements and effectors of this signaling cascade and reviews the therapeutic relevance of pharmacological inhibitors of the pathway in several malignancies, including lymphomas, leukemias, sarcomas, renal cell carcinoma, and breast cancer.

EXPERT OPINION

mTOR targeting is a highly promising therapeutic approach. First-generation mTOR inhibitors have already shown substantial activity in the treatment of certain tumors, while the emergence of second-generation catalytic mTOR inhibitors provides a better approach to target the pathway in malignant cells and has raised the potential for better clinical outcomes in the future.

Whole transcriptome sequencing reveals recurrent NOTCH1 mutations in mantle cell lymphoma

Mantle cell lymphoma (MCL), an aggressive subtype of non-Hodgkin lymphoma, is characterized by the hallmark translocation t(11;14)(q13;q32) and the resulting overexpression of cyclin D1 (CCND1). Our current knowledge of this disease encompasses frequent secondary cytogenetic aberrations and the recurrent mutation of a handful of genes, such as TP53, ATM, and CCND1. However, these findings insufficiently explain the biologic underpinnings of MCL. Here, we performed whole transcriptome sequencing on a discovery cohort of 18 primary tissue MCL samples and 2 cell lines. We found recurrent mutations in NOTCH1, a finding that we confirmed in an extension cohort of 108 clinical samples and 8 cell lines. In total, 12% of clinical samples and 20% of cell lines harbored somatic NOTCH1 coding sequence mutations that clustered in the PEST domain and predominantly consisted of truncating mutations or small frame-shifting indels. NOTCH1 mutations were associated with poor overall survival (P = .003). Furthermore, we showed that inhibition of the NOTCH pathway reduced proliferation and induced apoptosis in 2 MCL cell lines. In summary, we have identified recurrent NOTCH1 mutations that provide the preclinical rationale for therapeutic inhibition of the NOTCH pathway in a subset of patients with MCL.