Molecular biology of mantle cell lymphoma: From profiling studies to new therapeutic strategies

Elevated expression of NFE2L3 predicts the poor prognosis of pancreatic cancer patients

The highly malignant feature and difficulties for early diagnosis are the key reasons contributing to the poor prognosis of pancreatic cancer (PC) patients. NFE2L3 is a nuclear transcription factor, which has been reported an important biomarker of several tumors. But the role of NFE2L3 in PC remained undefined. Herein, through qPCR and immunohistochemistry, we found a significantly increased NFE2L3 in PC tissues as compared with adjacent non-tumor tissues. While reducing NFE2L3 expression suppressed the invasion abilities of PC cells, elevated NFE2L3 was found associated with lymph node metastasis (P = 0.001; HR = 3.95; 95% CI: 1.70 - 9.17) and advanced TNM stages (P < 0.001; HR = 4.06; 95% CI: 1.74 - 9.46). Consistently, data from both our two cohorts and the TCGA database revealed that higher NFE2L3 PC carriers had worse outcomes than those lower NFE2L3 expressers. Lastly, we confirmed the regulatory role of NFE2L3 on VEGFA, an important player involved in tumor angiogenesis. Collectively, our investigations suggested the oncogenic role of NFE2L3 in PC development and provided the rational for future adding NFE2L3 for the risk assessment of PC patients.

ABBREVIATIONS

NFE2L3: NF-E2-related factor 3; UHMK1: U2AF homology motif kinase 1; VEGFA: vascular endothelial growth factor A; GEO: gene expression omnibus; TCGA: The Cancer Genome Atlas; HPDE: human pancreas duct cells; OS: overall survival; IHC: immunohistochemistry; FFPE: formalin-fixed and paraffin-embedded; SEM: standard error of mean.

Mantle cell lymphoma in the era of precision medicine-diagnosis, biomarkers and therapeutic agents

Despite advances in the development of clinical agents for treating Mantle Cell Lymphoma (MCL), treatment of MCL remains a challenge due to complexity and frequent relapse associated with MCL. The incorporation of conventional and novel diagnostic approaches such as genomic sequencing have helped improve understanding of the pathogenesis of MCL, and have led to development of specific agents targeting signaling pathways that have recently been shown to be involved in MCL. In this review, we first provide a general overview of MCL and then discuss about the role of biomarkers in the pathogenesis, diagnosis, prognosis, and treatment for MCL. We attempt to discuss major biomarkers for MCL and highlight published and ongoing clinical trials in an effort to evaluate the dominant signaling pathways as drugable targets for treating MCL so as to determine the potential combination of drugs for both untreated and relapse/refractory cases. Our analysis indicates that incorporation of biomarkers is crucial for patient stratification and improve diagnosis and predictability of disease outcome thus help us in designing future precision therapies. The evidence indicates that a combination of conventional chemotherapeutic agents and novel drugs designed to target specific dysregulated signaling pathways can provide the effective therapeutic options for both untreated and relapse/refractory MCL.

Gene methylation and silencing of SOCS3 in mantle cell lymphoma

The significance of loss of SOCS3, a negative regulator of signalling pathways including those of STAT3 and NF-κB, was examined in mantle cell lymphoma (MCL). The protein expression and gene methylation status of SOCS3 were detected using immunohistochemistry/Western blots and methylation-specific polymerase chain reaction, respectively. To evaluate its functional importance, SOCS3 was restored in two SOCS3-negative MCL cell lines using a lentiviral vector. Loss of SOCS3 protein expression was found in 3/4 MCL cell lines and 18/33 (54.5%) tumours. SOCS3 was found consistently methylated in cell lines (3/4) and tumours (7/7) negative for SOCS3, and was unmethylated in all SOCS3-positive cell line (1/1) and tumours (5/5) examined. Treatment of all three SOCS3-negative cell lines with 2'-deoxy-5-azacytidine restored SOCS3 expression. SOCS3 is biologically important in MCL, as lentiviral transfer of SOCS3 in SOCS3-negative cell lines increased their apoptotic activity, downregulated nuclear factor (NF)-κB-p65, cyclin D1 (CCND1), BCL2 and BCL-XL (BCL2L1), and substantially dampened interleukin 10-induced STAT3 activation. In 19 patients aged ≤ 69 years at time of diagnosis, we found that those that carried SOCS3-negative tumours showed a trend toward a worse outcome (P = 0.1, log-rank).

Combined administration of rituximab and on 013105 induces apoptosis in mantle cell lymphoma cells and reduces tumor burden in a mouse model of mantle cell lymphoma

PURPOSE

Mantle cell lymphoma (MCL) is an incurable B-cell lymphoma, and new therapeutic strategies are urgently needed.

EXPERIMENTAL DESIGN

The effects of ON 013105, a novel benzylstyryl sulfone kinase inhibitor, alone or with doxorubicin or rituximab, were examined in Granta 519 and Z138C cells. For in vivo studies, CB17/SCID mice were implanted subcutaneously with Z138C cells and treated with various combinations of ON 013105, doxorubicin, and rituximab. Tumor burden and body weight were monitored for 28 days.

RESULTS

ON 013105 induced mitochondria-mediated apoptosis in MCL cells. Death was preceded by translocation of tBid to the mitochondria and cytochrome c release. In addition, ON 013105-treated cells exhibited reduced levels of cyclin D1, c-Myc, Mcl-1, and Bcl-xL. Using nuclear magnetic resonance (NMR) spectroscopy, we showed specific binding of ON 013105 to eIF4E, a critical factor for the initiation of protein translation. We proffer that this drug-protein interaction preferentially prevents the translation of the aforementioned proteins and may be the mechanism by which ON 013105 induces apoptosis in MCL cells. Efficacy studies in a mouse xenograft model showed that ON 013105 inhibited MCL tumor growth and that combining ON 013105 with rituximab reduced tumor burden further with negligible unwanted effects.

CONCLUSIONS

Our findings suggest that ON 013105, alone or in combination with rituximab, may be a potent therapeutic agent to treat MCLs.

The tumour suppressor FOXO3 is a key regulator of mantle cell lymphoma proliferation and survival

The FOXO3 (Forkhead/winged helix box class O 3) transcription factor is a crucial regulator of haematopoietic cell fate that controls proliferation and apoptosis, among other processes. Despite the central role of FOXO3 as a tumour suppressor and phosphatidylinositol 3-kinase (PI3K)/AKT effector, little is known about its involvement in mantle cell lymphoma (MCL) biology. This study investigated the expression and activity of FOXO3 in MCL cell lines and in primary cultures. We analysed the expression of key FOXO regulators and targets, and studied the effect of modulators of FOXO function on cell viability and apoptosis. FOXO3 was constitutively inactivated in MCL cell lines, and showed cytoplasmic localization in patient-derived cells. PI3K and AKT, but not mammalian target of rapamycin (mTOR), inhibitors induced FOXO3 nuclear translocation and activation in correlation with their impact on MCL proliferation and survival. Moreover, FOXO3-defective cells were resistant to PI3K/AKT inhibitors. Reactivation of FOXO function with a nuclear export inhibitor had a profound effect on cell viability, consistent with FOXO3 nuclear accumulation. Interestingly, inhibition of FOXO3 nuclear export enhanced the effect of doxorubicin. Taken together, our results confirm that FOXO3 is a relevant regulator of proliferation and apoptosis in MCL, and suggest that reactivation of FOXO3 function might be a useful therapeutic strategy in MCL patients.

Stem-like tumor cells confer drug resistant properties to mantle cell lymphoma

We recently identified clonogenic malignant stem cell populations in human mantle cell lymphoma (MCL), a particularly deadly subtype of non-Hodgkin lymphoma (NHL). We discovered that CD45+CD19- MCL cells, which we termed MCL-initiating cells (MCL-ICs), are highly tumorigenic and display self-renewal capacity in vivo; in contrast, CD45+CD19+ MCL cells, which constitute the vast majority of cells within the tumors, show no self-renewal capacity and greatly reduced tumorigenicity. Given the newly appreciated role of cancer-initiating cells in the drug resistance of cancers, it is critical to investigate whether CD45+CD19- MCL-ICs play a role in the drug resistance of human MCL. We discovered that MCL-ICs were more resistant to clinically relevant chemotherapeutic agents, in combination or in a single regimen, compared to CD45+CD19+ cells, and that this drug resistance was largely due to quiescent properties with enriched ABC transporters. In conclusion, designing novel therapies to kill CD45+CD19- MCL-ICs may prevent relapse and increase patient survival.

NFE2L3 (NRF3): the Cinderella of the Cap'n'Collar transcription factors

NFE2L3 [Nuclear factor (erythroid-derived 2)-like 3] or NRF3, a member of the Cap'n'Collar (CNC) family, is a basic-region leucine zipper (bZIP) transcription factor that was first identified over 10 years ago. Contrary to its extensively studied homolog NFE2L2 (NRF2), the regulation and function of the NFE2L3 protein have not yet attracted as much attention. Nevertheless, several recent reports have now shed light on the possible roles of NFE2L3. Structural and biochemical studies revealed a series of domains and modifications that are critical for its cellular regulation. The control of the subcellular localization of NFE2L3 appears to be essential for understanding its role in various cellular processes. Importantly, newer studies provide fascinating insights linking NFE2L3 to differentiation, inflammation, and carcinogenesis. Here, we present an overview of the current level of knowledge of NFE2L3 transcription factor biology in humans and mice. From being the Cinderella of the CNC transcription factors for many years, NFE2L3 may now rapidly come into its own.

Knock-down of SOX11 induces autotaxin-dependent increase in proliferation in vitro and more aggressive tumors in vivo

The transcription factor SOX11 is a novel diagnostic marker for mantle cell lymphoma (MCL), distinguishing this aggressive tumor from potential simulators. Recent data also show that the level of SOX11 correlates to in vitro growth properties in MCL, as well as the clinical progression. We have previously shown that MCL-associated pathways, such as Rb-E2F, are dysregulated leading to decreased proliferation upon overexpression of SOX11, emphasizing the impact of SOX11 on MCL-specific gene expression and growth control. However, it remains to be determined which growth regulatory pathways that are induced upon SOX11 knock-down, leading to an increased cellular growth. Consequently, we established a model cell line with constitutive down-regulation of SOX11. The highly proliferative features of this cell line were investigated by gene expression analysis, proliferation assay, cell cycle distribution and potential to induce tumors in NOD-SCID mice. Our in vitro studies demonstrated a SOX11-dependent regulation of MCL-specific gene expression. In addition, we identified autotaxin (ATX) to be regulated by SOX11. Our results clearly showed a correlation between SOX11 level and cellular growth rate, which was dependent on ATX, as well as a direct relation between the level of SOX11 in tumorigenic cells and the growth rate of these tumors in NOD-SCID mice.

Nfe2l3 (Nrf3) deficiency predisposes mice to T-cell lymphoblastic lymphoma

We have previously generated mice deficient for Nfe213 (NF-E2 p45 related factor 3 or Nrf3), a member of the cap 'n' collar family of basic-leucine zipper transcription factors. To examine whether Nrf3 is involved in chemical-induced carcinogenesis, we exposed the mice to benzo[a]pyrene (B[a]P), a carcinogen found in cigarette smoke. Contrary to wild-type mice, Nrf3-null animals are highly susceptible to B[a]P, exhibiting significantly increased mortality. Pathology analysis of affected tissue sections revealed a high incidence of T-cell lymphoblastic lymphoma in B[a]P-treated Nrf3(-/-) mice. Lymphoblastic lymphoma occasionally metastasized into the lung as demonstrated by perivascular malignant lymphocytic infiltration. Together, our studies show that the absence of Nrf3 predisposes mice to lymphoma development, suggesting a protective role of this transcription factor in hematopoietic malignancies. Our data demonstrate the first in vivo function of Nrf3 and its link to tumor development. Nrf3-deficient mice may serve as a preclinical mouse model to study carcinogen-induced lymphomagenesis.

The PARP inhibitor olaparib induces significant killing of ATM-deficient lymphoid tumor cells in vitro and in vivo

The Ataxia Telangiectasia Mutated (ATM) gene is frequently inactivated in lymphoid malignancies such as chronic lymphocytic leukemia (CLL), T-prolymphocytic leukemia (T-PLL), and mantle cell lymphoma (MCL) and is associated with defective apoptosis in response to alkylating agents and purine analogues. ATM mutant cells exhibit impaired DNA double strand break repair. Poly (ADP-ribose) polymerase (PARP) inhibition that imposes the requirement for DNA double strand break repair should selectively sensitize ATM-deficient tumor cells to killing. We investigated in vitro sensitivity to the poly (ADP-ribose) polymerase inhibitor olaparib (AZD2281) of 5 ATM mutant lymphoblastoid cell lines (LCL), an ATM mutant MCL cell line, an ATM knockdown PGA CLL cell line, and 9 ATM-deficient primary CLLs induced to cycle and observed differential killing compared with ATM wildtype counterparts. Pharmacologic inhibition of ATM and ATM knockdown confirmed the effect was ATM-dependent and mediated through mitotic catastrophe independently of apoptosis. A nonobese diabetic/severe combined immunodeficient (NOD/SCID) murine xenograft model of an ATM mutant MCL cell line demonstrated significantly reduced tumor load and an increased survival of animals after olaparib treatment in vivo. Addition of olaparib sensitized ATM null tumor cells to DNA-damaging agents. We suggest that olaparib would be an appropriate agent for treating refractory ATM mutant lymphoid tumors.

Degrasyn potentiates the antitumor effects of bortezomib in mantle cell lymphoma cells in vitro and in vivo: therapeutic implications

Mantle cell lymphoma (MCL) is an aggressive histotype of B-cell non-Hodgkin lymphoma that has increased in incidence over the past few decades and is incurable, usually poorly responsive to standard chemotherapy combinations, and associated with poor prognoses. Discovering new therapeutic agents with low toxicity that produce better outcomes in patients with MCL is an ongoing challenge. Recent studies showed that degrasyn, a novel small-molecule inhibitor of the Janus kinase/signal transducer and activation of transcription (JAK/STAT) pathway, exerts antitumor activity in lymphoid tumors by inhibiting key growth and survival signaling (JAK/STAT) pathways. In the present study, we found that treatment of both typical and blastoid-variant MCL cells with degrasyn in combination with bortezomib resulted in synergistic growth inhibition and apoptosis induction in vitro. The apoptosis in these cells was correlated with the downregulation of constitutive NF-kappaB and phosphorylated STAT3 activation, leading to the inhibition of c-Myc, cyclin D1, and bcl-2 protein expression and the upregulation of bax protein expression. In vivo, degrasyn and bortezomib interacted to synergistically prevent tumor development and prolong survival durations in a xenotransplant severe combined immunodeficient mouse model of MCL. These findings suggest that agents such as degrasyn that can pharmacologically target constitutively expressed NF-kappaB and STAT3 in MCL cells may be useful therapeutic agents for MCL when administered together with bortezomib.