A major role for Mcl-1 antiapoptotic protein in the IL-6-induced survival of human myeloma cells

Navigating IL-6: From molecular mechanisms to therapeutic breakthroughs

This concise review navigates the intricate realm of Interleukin-6 (IL-6), an important member of the cytokine family. Beginning with an introduction to cytokines, this narrative review unfolds with the historical journey of IL-6, illuminating its evolving significance. A crucial section unravels the three distinct signaling modes employed by IL-6, providing a foundational understanding of its versatile interactions within cellular landscapes. Moving deeper, the review meticulously dissects IL-6's signaling mechanisms, unraveling the complexities of its pleiotropic effects in both physiological responses and pathological conditions. A significant focus is dedicated to the essential role IL-6 plays in inflammatory diseases, offering insights into its associations and implications for various health conditions. The review also takes a therapeutic turn by exploring the emergence of anti-IL-6 monoclonal inhibitors, marking a profound stride in treatment modalities. Diving into the molecular realm, the review explores small molecules as agents for IL-6 inhibition, providing a nuanced perspective on diverse intervention strategies. As the review embarks on the final chapters, it contemplates future aspects, offering glimpses into potential research trajectories and the evolving landscape of IL-6-related studies.

CX3CR1-Expressing Immune Cells Infiltrate the Tumor Microenvironment and Promote Radiation Resistance in a Mouse Model of Lung Cancer

INTRODUCTION

Chemokine (C-X3-C Motif) Receptor 1 (CX3CR1) is present in a subset of the immune cells in the tumor microenvironment (TME) and plays an essential and diverse role in cancer progression. However, its potential function in the irradiated TME remains unknown.

MATERIALS AND METHODS

A mouse lung cancer model was performed by subcutaneously inoculating Lewis Lung Carcinoma (LLC) cells expressing luciferase (Luc-2) and mCherry cells in CX3CR1GFP/GFP, CX3CR1DTR/+, and wild-type (WT) mice. Bioluminescence imaging, clonogenic assay, and flow cytometry were used to assess tumor progression, proliferation, and cell composition after radiation.

RESULTS

Radiation provoked a significant influx of CX3CR1-expressing immune cells, notably monocytes and macrophages, into the TME. Co-culturing irradiated LLC cells with CX3CR1-deficient monocytes, and macrophages resulted in reduced clonogenic survival and increased apoptosis of the cancer cells. Interestingly, deficiency of CX3CR1 in macrophages led to a redistribution of the irradiated LLC cells in the S-phase, parallel to increased expression of cyclin E1, required for cell cycle G1/S transition. In addition, the deficiency of CX3CR1 expression in macrophages altered the cytokine secretion with a decrease in interleukin 6, a crucial mediator of cancer cell survival and proliferation. Next, LLC cells were injected subcutaneously into CX3CR1DTR/+ mice, sensitive to diphtheria toxin (DT), and WT mice. After injection, tumors were irradiated with 8 Gy, and mice were treated with DT, leading to conditional ablation of CX3CR1-expressing cells. After three weeks, CX3CR1-depleted mice displayed reduced tumor progression. Furthermore, combining the S-phase-specific chemotherapeutic gemcitabine with CX3CR1 cell ablation resulted in additional attenuation of tumor progression.

CONCLUSIONS

CX3CR1-expressing mononuclear cells invade the TME after radiation therapy in a mouse lung cancer model. CX3CR1 cell depletion attenuates tumor progression following radiation and sensitizes the tumor to S-phase-specific chemotherapy. Thus, we propose a novel strategy to improve radiation sensitivity by targeting the CX3CR1-expressing immune cells.

Autophagy: A Potential Therapeutic Target to Tackle Drug Resistance in Multiple Myeloma

Multiple myeloma (MM) is the second most prevalent hematologic malignancy. In the past few years, the survival of MM patients has increased due to the emergence of novel drugs and combination therapies. Nevertheless, one of the significant obstacles in treating most MM patients is drug resistance, especially for individuals who have experienced relapses or developed resistance to such cutting-edge treatments. One of the critical processes in developing drug resistance in MM is autophagic activity, an intracellular self-digestive process. Several possible strategies of autophagy involvement in the induction of MM-drug resistance have been demonstrated thus far. In multiple myeloma, it has been shown that High mobility group box protein 1 (HMGB1)-dependent autophagy can contribute to drug resistance. Moreover, activation of autophagy via proteasome suppression induces drug resistance. Additionally, the effectiveness of clarithromycin as a supplemental drug in treating MM has been reported recently, in which autophagy blockage is proposed as one of the potential action mechanisms of CAM. Thus, a promising therapeutic approach that targets autophagy to trigger the death of MM cells and improve drug susceptibility could be considered. In this review, autophagy has been addressed as a survival strategy crucial for drug resistance in MM.

Bone marrow microenvironment- induced regulation of Bcl-2 family members in multiple myeloma (MM): Therapeutic implications

In Multiple Myeloma (MM) the finely tuned homeostasis of the bone marrow (BM) microenvironment is disrupted. Evasion of programmed cell death (apoptosis) represents a hallmark of cancer. Besides genetic aberrations, the supportive and protective MM BM milieu, which is constituted by cytokines and growth factors, intercellular and cell: extracellular matrix (ECM) interactions and exosomes, in particular, plays a key role in the abundance of pro-survival members of the Bcl-2 family (i.e., Mcl-1, Bcl-2, and Bcl-xL) in tumor cells. Moreover, microenvironmental cues have also an impact on stability- regulating post-translational modifications of anti-apoptotic proteins including de/phosphorylation, polyubiquitination; on their intracellular binding affinities, and localization. Advances of our molecular knowledge on the escape of cancer cells from apoptosis have informed the development of a new class of small molecules that mimic the action of BH3-only proteins. Indeed, approaches to directly target anti-apoptotic Bcl-2 family members are among today's most promising therapeutic strategies and BH3-mimetics (i.e., venetoclax) are currently revolutionizing not only the treatment of CLL and AML, but also hold great therapeutic promise in MM. Furthermore, approaches that activate apoptotic pathways indirectly via modification of the tumor microenvironment have already entered clinical practice. The present review article will summarize our up-to-date knowledge on molecular mechanisms by which the MM BM microenvironment, cytokines, and growth factors in particular, mediates tumor cell evasion from apoptosis. Moreover, it will discuss some of the most promising science- derived therapeutic strategies to overcome Bcl-2- mediated tumor cell survival in order to further improve MM patient outcome.

Critical role of TLR activation in viral replication, persistence, and pathogenicity of Theiler's virus

Theiler's murine encephalomyelitis virus (TMEV) establishes persistent viral infections in the central nervous system and induces chronic inflammatory demyelinating disease in susceptible mice. TMEV infects dendritic cells, macrophages, B cells, and glial cells. The state of TLR activation in the host plays a critical role in initial viral replication and persistence. The further activation of TLRs enhances viral replication and persistence, leading to the pathogenicity of TMEV-induced demyelinating disease. Various cytokines are produced via TLRs, and MDA-5 signals linked with NF-κB activation following TMEV infection. In turn, these signals further amplify TMEV replication and the persistence of virus-infected cells. The signals further elevate cytokine production, promoting the development of Th17 responses and preventing cellular apoptosis, which enables viral persistence. Excessive levels of cytokines, particularly IL-6 and IL-1β, facilitate the generation of pathogenic Th17 immune responses to viral antigens and autoantigens, leading to TMEV-induced demyelinating disease. These cytokines, together with TLR2 may prematurely generate functionally deficient CD25-FoxP3+ CD4⁺ T cells, which are subsequently converted to Th17 cells. Furthermore, IL-6 and IL-17 synergistically inhibit the apoptosis of virus-infected cells and the cytolytic function of CD8+ T lymphocytes, prolonging the survival of virus-infected cells. The inhibition of apoptosis leads to the persistent activation of NF-κB and TLRs, which continuously provides an environment of excessive cytokines and consequently promotes autoimmune responses. Persistent or repeated infections of other viruses such as COVID-19 may result in similar continuous TLR activation and cytokine production, leading to autoimmune diseases.

Mechanisms of venetoclax resistance and solutions

The BCL-2 inhibitor venetoclax is currently approved for treatment of hematologic diseases and is widely used either as monotherapy or in combination strategies. It has produced promising results in the treatment of refractory or relapsed (R/R) and aged malignant hematologic diseases. However, with clinical use, resistance to venetoclax has emerged. We review the mechanism of reduced dependence on BCL-2 mediated by the upregulation of antiapoptotic proteins other than BCL-2, such as MCL-1 and BCL-XL, which is the primary mechanism of venetoclax resistance, and find that this mechanism is achieved through different pathways in different hematologic diseases. Additionally, this paper also summarizes the current investigations of the mechanisms of venetoclax resistance in terms of altered cellular metabolism, changes in the mitochondrial structure, altered or modified BCL-2 binding domains, and some other aspects; this article also reviews relevant strategies to address these resistance mechanisms.

Multiple Myeloma With Amplification of Chr1q: Therapeutic Opportunity and Challenges

Multiple myeloma (MM) is an incurable plasma cell malignancy with a heterogeneous genetic background. Each MM subtype may have its own therapeutic vulnerabilities, and tailored therapy could improve outcomes. However, the cumulative frequency of druggable targets across patients is very low, which has precluded the widespread adoption of precision therapy for patients with MM. Amplification of the long arm of chromosome 1 (Amp1q) is one of the most frequent genetic alterations observed in patients with MM, and its presence predicts inferior outcomes in the era of proteasome inhibitors and immunomodulatory agents. Therefore, establishing precision medicine for MM patients with Amp1q stands to benefit a large portion of patients who are otherwise at higher risk of relapse. In this article, we review the prevalence and clinical significance of Amp1q in patients with MM, its pathogenesis and therapeutic vulnerabilities, and discuss the opportunities and challenges for Amp1q-targeted therapy.

Translationally Controlled Tumor Protein-Mediated Stabilization of Host Antiapoptotic Protein MCL-1 Is Critical for Establishment of Infection by Intramacrophage Parasite Leishmania donovani

In the early phase of infection, the intramacrophage pathogen Leishmania donovani protects its niche with the help of the antiapoptotic protein myeloid cell leukemia-1 (MCL-1). Whether Leishmania could exploit MCL-1, an extremely labile protein, at the late phase is still unclear. A steady translational level of MCL-1 observed up to 48 h postinfection and increased caspase-3 activity in MCL-1-silenced infected macrophages documented its importance in the late hours of infection. The transcript level of MCL-1 showed a sharp decline at 6 h postinfection, and persistent MCL-1 expression in cyclohexamide-treated cells negates the possibility of de novo protein synthesis, thereby suggesting infection-induced stability. Increased ubiquitination, a prerequisite for proteasomal degradation of MCL-1, was also found to be absent in the late hours of infection. Lack of interaction with its specific E3 ubiquitin ligase MULE (MCL-1 ubiquitin ligase E3) and specific deubiquitinase USP9X prompted us to search for blockade of the ubiquitin-binding site in MCL-1. To this end, TCTP (translationally controlled tumor protein), a well-known binding partner of MCL-1 and antiapoptotic regulator, was found to be strongly associated with MCL-1 during infection. Phosphorylation of TCTP, a requirement for MCL-1 binding, was also increased in infected macrophages. Knockdown of TCTP decreased MCL-1 expression and short hairpin RNA-mediated silencing of TCTP in an infected mouse model of visceral leishmaniasis showed decreased parasite burden and induction of liver cell apoptosis. Collectively, our investigation revealed a key mechanism of how L. donovani exploits TCTP to establish infection within the host.

Pathogenic signaling in multiple myeloma

Multiple myeloma is a common hematological malignancy of plasma cells, the terminally differentiated B cells that secrete antibodies as part of the adaptive immune response. Significant progress has been made in treating multiple myeloma, but this disease remains largely incurable, and most patients will eventually suffer a relapse of disease that becomes refractory to further therapies. Moreover, a portion of patients with multiple myeloma present with disease that is refractory to all treatments from the initial diagnosis, and no current therapeutic approaches can help. Therefore, the task remains to advance new therapeutic strategies to help these vulnerable patients. One strategy to meet this challenge is to unravel the complex web of pathogenic signaling pathways in malignant plasma cells and use this information to design novel precision medicine strategies to assist these patients most at risk.

Therapeutic effects of an innovative BS-HH-002 drug on pancreatic cancer cells via induction of complete MCL-1 degradation

BS-HH-002 is a newly developed drug with excellent antitumor activity, which resulted from the modification and optimization of the side structure of the homoharringtonine (HHT). It is particularly efficient in treatment for acute myeloid leukemia and myelodysplastic syndromes. Here we tested whether BS-HH-002 also had anti-cancer effects on solid tumors, especially pancreatic cancer. The results showed that BS-HH-002 treatment resulted in the complete degradation of the anti-apoptosis protein MCL-1, thereby inhibiting proliferation and inducing apoptosis of pancreatic cancer cells. In contrast, BCL-2 and BCL-XL protein levels were still detected in apoptotic cells. Further, we compared HHT and BS-HH-002 in terms of PK and heart toxicity in animals. Compared to HHT, BS-HH-002 quickly reached high blood concentration after intravenous injection or oral administration, without causing obvious cardiac toxicity. These results indicate that BS-HH-002 is a promising new anti-cancer drug to treat pancreatic and other solid tumors.

Multipeptide stimulated PBMCs generate TEM/TCM for adoptive cell therapy in multiple myeloma

Multiple Myeloma (MM) patients suffer disease relapse due to the development of therapeutic resistance. Increasing evidence suggests that immunotherapeutic strategies can provide durable responses. Here we evaluate the possibility of adoptive cell transfer (ACT) by generating ex vivo T cells from peripheral blood mononuclear cells (PBMCs) isolated from MM patients by employing our previously devised protocols. We designed peptides from antigens (Ags) including cancer testis antigens (CTAs) that are over expressed in MM. We exposed PBMCs from different healthy donors (HDs) to single peptides. We observed reproducible Ag-specific cluster of differentiation 4⁺ (CD4⁺) and CD8⁺ T cell responses on exposure of PBMCs to different single peptide sequences. These peptide sequences were used to compile four different peptide cocktails. Naïve T cells from PBMCs from MM patients or HDs recognized the cognate Ag in all four peptide cocktails, leading to generation of multiclonal Ag-specific CD4⁺ and CD8⁺ effector and central memory T (T_EM and T_CM, respectively) cells which produced interferon-gamma (IFN-γ), granzyme B and perforin on secondary restimulation. Furthermore, this study demonstrated that immune cells from MM patients are capable of switching metabolic programs to induce effector and memory responses. Multiple peptides and cocktails were identified that induce IFN-γ⁺, T1-type, metabolically active T cells, thereby paving the way for feasibility testing of ACT in phase I clinical trials.

A Novel Orthotopic Liver Cancer Model for Creating a Human-like Tumor Microenvironment

Simple Summary

Hepatocellular carcinoma is the most common form of liver cancer. The lack of models that resemble actual tumor development in patients, limits the research to improve the diagnosis rate and develop new treatments. This study describes a novel mouse model that involves organoid formation and an implantation technique. This mouse model shares human genetic profiles and factors around the tumor, resembling the actual tumor development in patients. We demonstrate the roles of different cell types around the tumor, in promoting tumor growth, using this model. This model will be useful to understand the tumor developmental process, drug testing, diagnosis, prognosis, and treatment development.

Abstract

Hepatocellular carcinoma (HCC) is the most common form of liver cancer. This study aims to develop a new method to generate an HCC mouse model with a human tumor, and imitates the tumor microenvironment (TME) of clinical patients. Here, we have generated functional, three-dimensional sheet-like human HCC organoids in vitro, using luciferase-expressing Huh7 cells, human iPSC-derived endothelial cells (iPSC-EC), and human iPSC-derived mesenchymal cells (iPSC-MC). The HCC organoid, capped by ultra-purified alginate gel, was implanted into the disrupted liver using an ultrasonic homogenizer in the immune-deficient mouse, which improved the survival and engraftment rate. We successfully introduced different types of controllable TME into the model and studied the roles of TME in HCC tumor growth. The results showed the role of the iPSC-EC and iPSC-MC combination, especially the iPSC-MC, in promoting HCC growth. We also demonstrated that liver fibrosis could promote HCC tumor growth. However, it is not affected by non-alcoholic fatty liver disease. Furthermore, the implantation of HCC organoids to humanized mice demonstrated that the immune response is important in slowing down tumor growth at an early stage. In conclusion, we have created an HCC model that is useful for studying HCC development and developing new treatment options in the future.

AKT signaling restrains tumor suppressive functions of FOXO transcription factors and GSK3 kinase in multiple myeloma

The phosphatidylinositide-3 kinases and the downstream mediator AKT drive survival and proliferation of multiple myeloma (MM) cells. AKT signaling is active in MM and has pleiotropic effects; however, the key molecular aspects of AKT dependency in MM are not fully clear. Among the various downstream AKT targets are the Forkhead box O (FOXO) transcription factors (TFs) and glycogen synthase kinase 3 (GSK3), which are negatively regulated by AKT signaling. Here we show that abrogation of AKT signaling in MM cells provokes cell death and cell cycle arrest, which crucially depends on both FOXO TFs and GSK3. Based on gene expression profiling, we defined a FOXO-repressed gene set that has prognostic significance in a large cohort of patients with MM, indicating that AKT-mediated gene activation is associated with inferior overall survival. We further show that AKT signaling stabilizes the antiapoptotic myeloid cell leukemia 1 (MCL1) protein by inhibiting FOXO- and GSK3-mediated MCL1 turnover. In concordance, abrogation of AKT signaling greatly sensitized MM cells for an MCL1-targeting BH3-mimetic, which is currently in clinical development. Taken together, our results indicate that AKT activity is required to restrain the tumor-suppressive functions of FOXO and GSK3, thereby stabilizing the antiapoptotic protein MCL1 in MM. These novel insights into the role of AKT in MM pathogenesis and MCL1 regulation provide opportunities to improve targeted therapy for patients with MM.

Curcuma amarissima Extract Activates Growth and Survival Signal Transduction Networks to Stimulate Proliferation of Human Keratinocyte

Simple Summary

Like many plants in the family of Zingiberaceae, Curcuma amarissima has been traditionally used to induce healing and tissue regeneration. However, there is no scientific evidence to explain how Curcuma amarissima works to accelerate wound healing. Our data clearly proved that Curcuma amarissima extract could potentially accelerate the closure of scratch wounds of human keratinocytes by stimulating cell proliferation. The potential mechanisms underlying these effects were defined to be associated with the activated signal transduction pathways relevant to cell proliferation and survival. This strongly suggests the ability of Curcuma amarissima to enhance the process of keratinocyte reepithelization during wound healing. Our current study provides convincing evidence that supports the possibility to develop an effective wound-healing promoting agent from this plant.

Abstract

Many medicinal plants have been used to treat wounds. Here, we revealed the potential wound healing effects of Curcuma amarissima (CA). Our cell viability assay showed that CA extract increased the viability of HaCaT cells that were cultured in the absence of serum. This increase in cell viability was proved to be associated with the pharmacological activities of CA extract in inducing cell proliferation. To further define possible molecular mechanisms of action, we performed Western blot analysis and immunofluorescence study, and our data demonstrated that CA extract rapidly induced ERK1/2 and Akt activation. Consistently, CA extract accelerated cell migration, resulting in rapid healing of wounded human keratinocyte monolayer. Specifically, the CA-induced increase of cell monolayer wound healing was blocked by the MEK inhibitor (U0126) or the PI3K inhibitor (LY294002). Moreover, CA extract induced the expression of Mcl-1, which is an anti-apoptotic protein, supporting that CA extract enhances human keratinocyte survival. Taken together, our study provided convincing evidence that Curcuma amarissima can promote proliferation and survival of human keratinocyte through stimulating the MAPK and PI3K/Akt signaling cascades. These promising data emphasize the possibility to develop this plant as a wound healing agent for the potential application in regenerative medicine.

Susceptibility of multiple myeloma to B-cell lymphoma 2 family inhibitors

Multiple myeloma (MM) is a biologically complex hematological disorder defined by the clonal proliferation of malignant plasma cells producing excessive monoclonal immunoglobulin that interacts with components of the bone marrow microenvironment, resulting in the major clinical features of MM. Despite the development of numerous protocols to treat MM patients, this cancer remains currently incurable; due in part to the emergence of resistant clones, highlighting the unmet need for innovative therapeutic approaches. Accumulating evidence suggests that the survival of MM molecular subgroups depends on the expression profiles of specific subsets of anti-apoptotic B-cell lymphoma (BCL)-2 family members. This review summarizes the mechanisms underlying the anti-myeloma activities of the potent BCL-2 family protein inhibitors, individually or in combination with conventional therapeutic options, and provides an overview of the strong rationale to clinically investigate such interventions for MM therapy.

Roles and mechanisms of adipokines in drug resistance of tumor cells

The drug resistance of cancer cells has become one of the biggest obstacles of effective anticancer treatments. Adipocytes produce plenty of cytokines (also known as adipokines), which remarkably affect the drug resistance exhibited by cancer cells. Different adipokines (leptin, visfatin, resistin, adiponectin, Interleukin 6, and tumor necrosis factor α) can induce drug resistance in different cancer cells by various functional mechanisms. This phenomenon is of great interest in pharmacological anti-cancer studies since it indicates that in the cancers with adipocyte-rich microenvironment, all adipokines join together to assist cancer cells to survive by facilitating drug resistance. Studies on adipokines contribute to the development of novel pharmacological strategies for cancer therapy if their roles and molecular targets are better understood. The review will elucidate the roles and the underlying mechanisms of adipokines in drug resistance, which may be of great significance for revealing new strategies for cancer treatment.

BCL2 Family Inhibitors in the Biology and Treatment of Multiple Myeloma

Although much progress has been made in the treatment of multiple myeloma, the majority of patients fail to be cured and require numerous lines of therapy. Inhibitors of the BCL2 family represent an exciting new class of drugs with a novel mechanism of action that are likely to have activity as single agents and in combination with existing myeloma therapies. The BCL2 proteins are oncogenes that promote cell survival and are frequently upregulated in multiple myeloma, making them attractive targets. Venetoclax, a BCL2 specific inhibitor, is furthest along in development and has shown promising results in a subset of myeloma characterized by the t(11;14) translocation. Combining venetoclax with proteasome inhibitors and monoclonal antibodies has improved responses in a broader group of patients, but has come at the expense of a toxicity safety signal that requires additional follow-up. MCL1 inhibitors are likely to be effective in a broader range of patients and are currently in early clinical trials. This review will cover much of what is known about the biology of these drugs, biomarkers that predict response, mechanisms of resistance, and unanswered questions as they pertain to multiple myeloma.

Stroma-Mediated Resistance to S63845 and Venetoclax through MCL-1 and BCL-2 Expression Changes Induced by miR-193b-3p and miR-21-5p Dysregulation in Multiple Myeloma

BH3-mimetics targeting anti-apoptotic proteins such as MCL-1 (S63845) or BCL-2 (venetoclax) are currently being evaluated as effective therapies for the treatment of multiple myeloma (MM). Interleukin 6, produced by mesenchymal stromal cells (MSCs), has been shown to modify the expression of anti-apoptotic proteins and their interaction with the pro-apoptotic BIM protein in MM cells. In this study, we assess the efficacy of S63845 and venetoclax in MM cells in direct co-culture with MSCs derived from MM patients (pMSCs) to identify additional mechanisms involved in the stroma-induced resistance to these agents. MicroRNAs miR-193b-3p and miR-21-5p emerged among the top deregulated miRNAs in myeloma cells when directly co-cultured with pMSCs, and we show their contribution to changes in MCL-1 and BCL-2 protein expression and in the activity of S63845 and venetoclax. Additionally, direct contact with pMSCs under S63845 and/or venetoclax treatment modifies myeloma cell dependence on different BCL-2 family anti-apoptotic proteins in relation to BIM, making myeloma cells more dependent on the non-targeted anti-apoptotic protein or BCL-X_L. Finally, we show a potent effect of the combination of S63845 and venetoclax even in the presence of pMSCs, which supports this combinatorial approach for the treatment of MM.

IL-6 as a major regulator of MDSC activity and possible target for cancer immunotherapy

Myeloid-derived suppressor cells (MDSC) are generated during tumor progression and suppress the anti-tumor functions of T and natural killer (NK) cells. Their enrichment is associated with a bad prognosis and a worse outcome of immunotherapy in cancer patients. The cytokine interleukin (IL)-6 was found to be a crucial regulator of MDSC accumulation and activation as well as a factor, stimulating tumor cell proliferation, survival, invasiveness and metastasis. Accordingly, IL-6 can serve as a negative prognostic marker in cancer. On the other hand, this cytokine is also involved in T cell activation. This review discusses the pleiotropic effects of IL-6 on immune cell populations that are critical for tumor development, such as MDSC and T cells, and summarizes the data on targeting IL-6 or IL-6 receptor (IL-6R) for tumor immunotherapy to block MDSC-mediated immunosuppression in cancer patients.

Combined targeting of MEK and the glucocorticoid receptor for the treatment of RAS-mutant multiple myeloma

BACKGROUND

Multiple myeloma (MM) remains incurable despite recent therapeutic advances. RAS mutations are frequently associated with relapsed/refractory disease. Efforts to target the mitogen-activated protein kinase (MAPK) pathway with the MEK inhibitor, trametinib (Tra) have been limited by toxicities and the development of resistance. Dexamethasone (Dex) is a corticosteroid commonly used in clinical practice, to enhance efficacy of anti-myeloma therapy. Therefore, we hypothesised that the combination of Tra and Dex would yield synergistic activity in RAS-mutant MM.

METHODS

The response of human MM cell lines to drug treatment was analysed using cell proliferation assays, Western blotting, Annexin V and propidium iodide staining by flow cytometry and reverse phase protein arrays. The efficacy of trametinib and dexamethasone treatment in the MM.1S xenograft model was assessed by measuring tumor volume over time.

RESULTS

The Tra/Dex combination demonstrated synergistic cytotoxicity in KRAS^G12A mutant lines MM.1S and RPMI-8226. The induction of apoptosis was associated with decreased MCL-1 expression and increased BIM expression. Reverse phase proteomic arrays revealed suppression of FAK, PYK2, FLT3, NDRG1 and 4EBP1 phosphorylation with the Tra/Dex combination. Notably, NDRG1 expression was associated with the synergistic response to Tra/Dex. MM cells were sensitive to PDK1 inhibition and IGF1-induced signalling partially protected from Tra/Dex treatment, highlighting the importance of this pathway. In the MM.1S tumor xenograft model, only the combination of Tra/Dex resulted in a significant inhibition of tumor growth.

CONCLUSIONS

Overall Tra/Dex demonstrates antiproliferative activity in RAS-mutant MM cell lines associated with suppression of pro-survival PDK1 signalling and engagement of apoptotic pathways. Our data support further investigation of this combination in RAS-mutant MM.

Multiple Myeloma: Available Therapies and Causes of Drug Resistance

Multiple myeloma (MM) is the second most common blood cancer. Treatments for MM include corticosteroids, alkylating agents, anthracyclines, proteasome inhibitors, immunomodulatory drugs, histone deacetylase inhibitors and monoclonal antibodies. Survival outcomes have improved substantially due to the introduction of many of these drugs allied with their rational use. Nonetheless, MM patients successively relapse after one or more treatment regimens or become refractory, mostly due to drug resistance. This review focuses on the main drugs used in MM treatment and on causes of drug resistance, including cytogenetic, genetic and epigenetic alterations, abnormal drug transport and metabolism, dysregulation of apoptosis, autophagy activation and other intracellular signaling pathways, the presence of cancer stem cells, and the tumor microenvironment. Furthermore, we highlight the areas that need to be further clarified in an attempt to identify novel therapeutic targets to counteract drug resistance in MM patients.

CircRBM33 regulates IL-6 to promote gastric cancer progression through targeting miR-149

There is increasing evidence of the vital role played by circular RNAs (circRNAs) in the progression of gastric cancer (GC). A circRNA, hsa_circ_0001772, was generated from the RBM33 gene and named circRBM33. The aim of this study was to investigate the role of circRBM33 in GC. Quantitative real-time PCR (qRT-PCR) was used to quantify the expression of circRBM33 in 79 pairs of GC tissues and paracancerous tissues and 4 GC cell lines (MGC-803, BGC-823, SGC-7901, and AGS). Bioinformatics databases were used to predict downstream targets of circRNA and micro RNA (miRNA). Dual luciferase reporter assay was used to verify whether miR-149 was a direct binding target for circRBM33. Cell Counting Kit-8 (CCK-8) assay, 5-Ethynyl-2´-deoxyuridine (EDU) assay, transwell assay, and flow-cytometric analyses were performed to determine the role of circRBM33 in the biological functioning of GC cells. Western blot technique was used to quantify the levels of interleukin-6 (IL-6). CircRBM33 was distinctly upregulated in GC specimens and cell lines and a close correlation between circRBM33 expression and clinical characteristics of GC was observed. After silencing circRBM33, the apoptosis of GC cells increased, while proliferation, migration, and invasion decreased. Rescue experiments indicated that circRBM33 manipulates biological function in GC cells through the circRBM33/miR-149/IL-6 axis. CircRBM33 can be used as a tumor biomarker and a possible therapeutic target in the future.

Kaempferia parviflora Extract Inhibits STAT3 Activation and Interleukin-6 Production in HeLa Cervical Cancer Cells

Kaempferia parviflora (KP) has been reported to have anti-cancer activities. We previously reported its effects against cervical cancer cells and continued to elucidate the effects of KP on inhibiting the production and secretion of interleukin (IL)-6, as well as its relevant signaling pathways involved in cervical tumorigenesis. We discovered that KP suppressed epidermal growth factor (EGF)-induced IL-6 secretion in HeLa cells, and it was associated with a reduced level of Glycoprotein 130 (GP130), phosphorylated signal transducers and activators of transcription 3 (STAT3), and Mcl-1. Our data clearly showed that KP has no effect on nuclear factor kappa B (NF-κB) localization status. However, we found that KP inhibited EGF-stimulated phosphorylation of tyrosine 1045 and tyrosine 1068 of EGF receptor (EGFR) without affecting its expression level. The inhibition of EGFR activation was verified by the observation that KP significantly suppressed a major downstream MAP kinase, ERK1/2. Consistently, KP reduced the expression of Ki-67 protein, which is a cellular marker for proliferation. Moreover, KP potently inhibited phosphorylation of STAT3, Akt, and the expression of Mcl-1 in response to exogenous IL-6 stimulation. These data suggest that KP suppresses EGF-induced production of IL-6 and inhibits its autocrine IL-6/STAT3 signaling critical for maintaining cancer cell progression. We believe that KP may be a potential alternative anti-cancer agent for suppressing cervical tumorigenesis.

STAT3: A Promising Therapeutic Target in Multiple Myeloma

Multiple myeloma (MM) is an incurable plasma cell malignancy for which novel treatment options are required. Signal Transducer and Activator of Transcription 3 (STAT3) overexpression in MM appears to be mediated by a variety of factors including interleukin-6 signaling and downregulation of Src homology phosphatase-1 (SHP-1). STAT3 overexpression in MM is associated with an adverse prognosis and may play a role in microenvironment-dependent treatment resistance. In addition to its pro-proliferative role, STAT3 upregulates anti-apoptotic proteins and leads to microRNA dysregulation in MM. Phosphatase of regenerating liver 3 (PRL-3) is an oncogenic phosphatase which is upregulated by STAT3. PRL-3 itself promotes STAT-3 phosphorylation resulting in a positive feedback loop. PRL-3 is overexpressed in a subset of MM patients and may cooperate with STAT3 to promote survival of MM cells. Indirectly targeting STAT3 via JAK (janus associated kinase) inhibition has shown promise in early clinical trials. Specific inhibitors of STAT3 showed in vitro efficacy but have failed in clinical trials while several STAT3 inhibitors derived from herbs have been shown to induce apoptosis of MM cells in vitro. Optimising the pharmacokinetic profiles of novel STAT3 inhibitors and identifying how best to combine these agents with existing anti-myeloma therapy are key questions to be addressed in future clinical trials.

Role and Regulation of Pro-survival BCL-2 Proteins in Multiple Myeloma

Apoptosis plays a key role in protection against genomic instability and maintaining tissue homeostasis, and also shapes humoral immune responses. During generation of an antibody response, multiple rounds of B-cell expansion and selection take place in germinal centers (GC) before high antigen affinity memory B-cells and long-lived plasma cells (PC) are produced. These processes are tightly regulated by the intrinsic apoptosis pathway, and malignant transformation throughout and following the GC reaction is often characterized by apoptosis resistance. Expression of pro-survival BCL-2 family protein MCL-1 is essential for survival of malignant PC in multiple myeloma (MM). In addition, BCL-2 and BCL-XL contribute to apoptosis resistance. MCL-1, BCL-2, and BCL-XL expression is induced and maintained by signals from the bone marrow microenvironment, but overexpression can also result from genetic lesions. Since MM PC depend on these proteins for survival, inhibiting pro-survival BCL-2 proteins using novel and highly specific BH3-mimetic inhibitors is a promising strategy for treatment. This review addresses the role and regulation of pro-survival BCL-2 family proteins during healthy PC differentiation and in MM, as well as their potential as therapeutic targets.

MCL-1 inhibition in cancer treatment

Myeloid cell leukemia-1 (MCL-1), a member of antiapoptotic BCL-2 family proteins, is a key regulator of mitochondrial homeostasis. Frequent overexpression of MCL-1 in human primary and drug-resistant cancer cells makes it an attractive cancer therapeutic target. Significant progress has been made in the development of small-molecule MCL-1 inhibitors in recent years, and three MCL-1 selective inhibitors have advanced to clinical trials. This review briefly discusses recent advances in the development of small molecules targeting MCL-1 for cancer therapy.

The association between preoperative serum interleukin-6 levels and postoperative prognosis in patients with T2 gallbladder cancer

BACKGROUND

Interleukin-6 (IL-6) is closely associated with tumor progression. Whether it can predict postoperative prognosis of patients with T2 gallbladder cancer (GBC) remains controversial.

METHODS

We retrospectively collected the medical records of 125 patients with T2 GBC. Then, we analyzed the association between preoperative serum IL-6 levels and postoperative survival by multivariate Cox analyses and Kaplan-Meier curves in exploratory subgroups.

RESULTS

Predictive effects of serum IL-6 levels on overall survival were similar across most of the evaluated subgroups, except in different tumor location subgroups. The independent odds ratio (OR) of serum IL-6 levels was 2.57 (95%CI 1.73-3.82) in the hepatic side subgroup, while it was 1.15 (95%CI 0.68-1.93) in the peritoneal side subgroup (P = 0.014 for interaction). When we categorized serum IL-6 levels by median value (4.2 pg/mL), the 5-year survival rate of patients with high serum IL-6 levels was significantly higher in the hepatic side subgroup (58.5% vs 14.8%, P < 0.001), but no such difference was found in the peritoneal side subgroup (62.2% vs 67.6%, P = 0.722).

CONCLUSIONS

Preoperative serum IL-6 is significantly associated with prognostic implications in patients with hepatic side T2 GBC, not in those with peritoneal side tumors.

DNMTi/HDACi combined epigenetic targeted treatment induces reprogramming of myeloma cells in the direction of normal plasma cells

Background

Multiple myeloma (MM) is the second most common hematologic malignancy. Aberrant epigenetic modifications have been reported in MM and could be promising therapeutic targets. As response rates are overall limited but deep responses occur, it is important to identify those patients who could indeed benefit from epigenetic-targeted therapy.

Methods

Since HDACi and DNMTi combination have potential therapeutic value in MM, we aimed to build a GEP-based score that could be useful to design future epigenetic-targeted combination trials. In addition, we investigated the changes in GEP upon HDACi/DNMTi treatment.

Results

We report a new gene expression-based score to predict MM cell sensitivity to the combination of DNMTi/HDACi. A high Combo score in MM patients identified a group with a worse overall survival but a higher sensitivity of their MM cells to DNMTi/HDACi therapy compared to a low Combo score. In addition, treatment with DNMTi/HDACi downregulated IRF4 and MYC expression and appeared to induce a mature BMPC plasma cell gene expression profile in myeloma cell lines.

Conclusion

In conclusion, we developed a score for the prediction of primary MM cell sensitivity to DNMTi/HDACi and found that this combination could be beneficial in high-risk patients by targeting proliferation and inducing maturation.

The phosphatase of regenerating liver-3 (PRL-3) is important for IL-6-mediated survival of myeloma cells

Multiple myeloma (MM) is a neoplastic proliferation of bone marrow plasma cells. PRL-3 is a phosphatase induced by interleukin (IL)-6 and other growth factors in MM cells and promotes MM-cell migration. PRL-3 has also been identified as a marker gene for a subgroup of patients with MM. In this study we found that forced expression of PRL-3 in the MM cell line INA-6 led to increased survival of cells that were depleted of IL-6. It also caused redistribution of cells in cell cycle, with an increased number of cells in G2M-phase. Furthermore, forced PRL-3 expression significantly increased phosphorylation of Signal transducer and activator of transcription (STAT) 3 both in the presence and the absence of IL-6. Knockdown of PRL-3 with shRNA reduced survival in MM cell line INA-6. A pharmacological inhibitor of PRL-3 reduced survival in the MM cell lines INA-6, ANBL-6, IH-1, OH-2 and RPMI8226. The inhibitor also reduced survival in 9 of 9 consecutive samples of purified primary myeloma cells. Treatment with the inhibitor down-regulated the anti-apoptotic protein Mcl-1 and led to activation of the intrinsic apoptotic pathway. Inhibition of PRL-3 also reduced IL-6-induced phosphorylation of STAT3. In conclusion, our study shows that PRL-3 is an important mediator of growth factor signaling in MM cells and hence possibly a good target for treatment of MM.

YM155 exerts potent cytotoxic activity against quiescent (G0/G1) multiple myeloma and bortezomib resistant cells via inhibition of survivin and Mcl-1

YM155, a novel small molecule inhibitor of survivin, shows broad anticancer activity. Here, we have focused on the cytotoxic activity of YM155 against multiple myeloma (MM) including cytokinetically quiescent (G₀/G₁) cells and bortezomib resistant cells. YM155 strongly inhibited the growth of MM cell lines with the IC₅₀ value of below 10 nM. YM155 also showed potent anti-myeloma activity in mouse xenograft model. YM155 suppressed the expression of survivin and rapidly directed Mcl-1 protein for proteasome degradation. YM155 abrogated the interleukin-6-induced STAT3 phosphorylation, subsequently blocked Mcl-1 expression and induced apoptosis in MM cells. Triple-color flow cytometric analysis revealed that YM155 potently induced cell death of MM cells in G₀ phase. Quiescent primary MM cells were also sensitive to YM155. We established bortezomib-resistant MM cell line, U266/BTZR1, which possess a point mutation G322A. YM155 exhibited similar cytotoxic potency against U266/BTZR1 compared with parental cells. Interestingly, survivin expression was markedly elevated in U266/BTZR1 cells. Treatment with YM155 significantly down-regulated this increased survivin and Mcl-1 expression in U266/BTZR1 cells. In conclusion, our data indicate that YM155 exhibits potent cytotoxicity against quiescent (G₀/G₁) MM cells and bortezomib-resistant cells. These unique features of YM155 may be beneficial for the development of new therapeutic strategies to eliminate quiescent MM cells and overcome bortezomib resistance.

Culturing with modified EGM2 medium enhances porcine neonatal islet-like cell clusters resistance to apoptosis in islet xenotransplantation

BACKGROUND

Neonatal pig islet-like cell clusters (NICC) are an attractive source of insulin-producing tissue for potential transplantation treatment of type 1 diabetic patients. However, a considerable loss of NICC after their transplantation due to apoptosis resulted from islet isolation and instant blood-mediated inflammatory reaction remains to be overcome.

METHODS

EGM2 medium depleted with hydrocortisone and supplemented with 50 mmol/L isobutylmethylxanthine, 10 mmol/L nicotinamide, and 10 mmol/L glucose was used to culture NICC at day 1, the day after isolation and changed every other day. NICC cultured with EGM2 or control Ham's F-10 medium were collected at day 7 of culture for the following assays. The viability of NICC was evaluated by AO/EB staining and FACS. Static assay and oxygen consumption rate analysis were performed to assess the function of NICC. Insulin and glucagon gene expression were measured by real-time PCR. Tubing loops model and TUNEL assay were performed to confirm the apoptosis-resistant ability of NICC cultured with modified EGM2 medium. Serum starvation and hypoxia treatment were used to test the tolerant capability of NICC in the microenvironment of hypoxia/nutrient deficiency in vitro. The molecules involved in apoptosis pathways in NICC were analyzed by Western blotting.

RESULTS

Compared with Ham's F-10 medium, culturing NICC with EGM2 medium led to increased number and viability of NICC with higher stimulation index, upregulated gene expression of both insulin and glucagon, and enhanced mitochondria function. Furthermore, fewer modified EGM2 medium cultured NICC were found under apoptosis when evaluated in an in vitro tubing loop model of IBMIR. Moreover, EGM2 medium cultured NICC demonstrated much less apoptotic cells under either serum starvation or hypoxia condition than their Ham's F-10 medium cultured counterparts. The enhanced capability of EGM2 cultured NICC to resist apoptosis was associated with their elevated protein levels of anti-apoptotic Bcl-2 family member Mcl-1.

CONCLUSION

Culturing NICC with EGM2 provides a simple and effective approach not only to increase NICC yield, viability, and maturation but also to enhance their resistance to apoptosis to preserve the initial graft mass for successful islet xenotransplantation.

MK2206 enhances the cytocidal effects of bufalin in multiple myeloma by inhibiting the AKT/mTOR pathway

Despite the development of promising cancer therapeutic drugs, multiple myeloma (MM) remains an incurable disease. Bufalin is a bufanolide steroid compound of the traditional Chinese medicine Chan Su that was previously shown to exert growth suppression effects on myeloma cell lines. Previous studies conducted by our group demonstrated that bufalin activated the AKT/mTOR pathway in myeloma cells, which is considered an essential pathway to disease progression and is related to drug resistance in MM. In view of the significant role of AKT in MM, the allosteric AKT inhibitor MK2206 was selected in order to enhance the antitumor effects of bufalin in different MM cell lines (NCI-H929, U266, LP-1 and RPMI8226). The data indicated that MK2206 enhanced the cytotoxicity of bufalin in MM cells, via the suppression of cellular proliferation and the induction of apoptosis, as demonstrated by cleavage of apoptosis-related proteins. This effect was further noted in the presence of exogenous interleukin-6 and/or following the co-culture of MM cells with bone marrow stromal cells (BMSC). This process was associated with the inhibition of the AKT/mTOR pathway. The combination of bufalin with MK2206 reduced the secretion of IL-6 in U266 cells. The combined treatment exhibited similar anti-MM effects in bortezomib-resistant cell lines (NCI-H929R, U266R). In addition to the in vitro cell line models, the synergistic effect was noted in primary MM cells and in MM xenografts of BALB-c and NOD-SCID mice. In conclusion, the data suggested that MK2206 significantly enhanced the cytocidal effects of bufalin in MM cells, regardless of the sensitivity to bortezomib, via the inhibition of the AKT/mTOR pathway. The study provided the basis of a promising treatment approach for MM.

Targeting executioner procaspase-3 with the procaspase-activating compound B-PAC-1 induces apoptosis in multiple myeloma cells

Multiple myeloma (MM) is a plasma cell neoplasm that has a low apoptotic index. We investigated a new class of small molecules that target the terminal apoptosis pathway, called procaspase activating compounds (PACs), in myeloma cells. PAC agents (PAC-1 and B-PAC-1) convert executioner procaspases (procaspase 3, 6, and 7) to active caspases 3, 6, and 7, which cleave target substrates to induce cellular apoptosis cascade. We hypothesized that targeting this terminal step could overcome survival and drug-resistance signals in myeloma cells and induce programmed cell death. Myeloma cells expressed executioner caspases. Additionally, our studies demonstrated that B-PAC-1 is cytotoxic to chemotherapy-resistant or sensitive myeloma cell lines (n = 7) and primary patient cells (n = 11). Exogenous zinc abrogated B-PAC-1-induced cell demise. Apoptosis induced by B-PAC-1 treatment was similar in the presence or absence of growth-promoting cytokines such as interleukin 6 and hepatocyte growth factor. Presence or absence of antiapoptotic proteins such as BCL-2, BCL-XL, or MCL-1 did not impact B-PAC-1-mediated programmed cell death. Collectively, our data demonstrate the proapoptotic effect of B-PAC-1 in MM and suggest that activating terminal executioner procaspases 3, 6, and 7 bypasses survival and drug-resistance signals in myeloma cells. This novel strategy has the potential to become an effective antimyeloma therapy.

Fas and TRAIL 'death receptors' as initiators of inflammation: Implications for cancer

Fas (CD95/APO-1) and TRAIL (CD253, TNFSF10, APO2) are members of a subset of the TNF receptor superfamily known as 'death receptors'. To date, the overwhelming majority of studies on Fas and TRAIL (TNF-related apoptosis-inducing ligand) have explored the role of these receptors as initiators of apoptosis. However, sporadic reports also suggest that engagement of the Fas and TRAIL receptors can lead to other outcomes such as cytokine and chemokine production, cell proliferation, cell migration and differentiation. Indeed, although transformed cells frequently express Fas and TRAIL, most do not undergo apoptosis upon engagement of these receptors and significant effort has been devoted toward exploring how to sensitize such cells to the pro-apoptotic effects of 'death receptor' stimulation. Moreover, the expression of Fas and TRAIL receptors is greatly elevated in many cancer types such as hepatocellular carcinoma, renal carcinoma and ovarian cancer, suggesting that such tumors benefit from the expression of these receptors. Furthermore, several studies have shown that tumor proliferation, progression and invasion can be impaired through blocking or downregulation of Fas expression, but the mechanistic basis for these effects is largely unknown. Thus, the characterization of Fas and TRAIL as 'death receptors' is a gross oversimplification, especially in the context of cancer. It is becoming increasingly clear that 'death receptor' engagement can lead to outcomes, other than apoptosis, that become subverted by certain tumors to their benefit. Here we will discuss death-independent outcomes of Fas and TRAIL signaling and their implications for cancer.

A phase 2, randomized, double-blind, placebo-controlled study of siltuximab (anti-IL-6 mAb) and bortezomib versus bortezomib alone in patients with relapsed or refractory multiple myeloma

We compared the safety and efficacy of siltuximab (S), an anti-interleukin-6 chimeric monoclonal antibody, plus bortezomib (B) with placebo (plc) + B in patients with relapsed/refractory multiple myeloma in a randomized phase 2 study. Siltuximab was given by 6 mg/kg IV every 2 weeks. On progression, B was discontinued and high-dose dexamethasone could be added to S/plc. Response and progression-free survival (PFS) were analyzed pre-dexamethasone by European Group for Blood and Marrow Transplantation (EBMT) criteria. For the 281 randomized patients, median PFS for S + B and plc + B was 8.0 and 7.6 months (HR 0.869, P = 0.345), overall response rate was 55 versus 47% (P = 0.213), complete response rate was 11 versus 7%, and median overall survival (OS) was 30.8 versus 36.8 months (HR 1.353, P = 0.103). Sustained suppression of C-reactive protein, a marker reflective of inhibition of interleukin-6 activity, was seen with S + B. Siltuximab did not affect B pharmacokinetics. Siltuximab/placebo discontinuation (75 versus 66%), grade ≥3 neutropenia (49 versus 29%), thrombocytopenia (48 versus 34%), and all-grade infections (62 versus 49%) occurred more frequently with S + B. The addition of siltuximab to bortezomib did not appear to improve PFS or OS despite a numerical increase in response rate in patients with relapsed or refractory multiple myeloma.

Silence of MCL-1 upstream signaling by shRNA abrogates multiple myeloma growth

Objectives

Multiple myeloma (MM) is an incurable B-cell cancer with accumulated clonal abnormal plasma cells in bone marrow of patients. MCL-1 (myeloid cell leukemia sequence 1) protein is an anti-apoptotic molecule in MM cells and regulated by pro-inflammatory cytokine IL-6 and downstream signaling molecules STAT3, PI3K and MAPK. The purpose of this study is to investigate the effect of STAT3, PI3K and MAPK gene silence on MCL-1 expression in human MM cells and the consequence of cell survival.

Methods

Lentivirus small hairpin RNA (shRNA) interference techniques were utilized to knock down STAT3, PI3K or MAPK genes. Gene and protein expression was quantified by quantitative real-time PCR and Western Blot. MM cell apoptosis was examined by annexin-V FITC/propidium iodide staining.

Results

Efficient silence of STAT3, PI3K, MAPK1 or MAPK2 gene robustly abrogated IL-6 enhanced MCL-1 expression and suppressed MM cell growth. Silencing STAT3 gene inhibited PI3K expression, silencing PI3K markedly abrogated STAT3 and MAPK production. Inhibition of MAPK2 gene by shMAPK2 suppressed STAT3, PI3K and MAPK1 expression in the cells. Silencing of STAT3, PI3K and MAPK2 together completely blocked MCL-1 expression in MM cells.

Conclusion

There is a syngeneic effect among the three independent STAT3, PI3K and MAPK2 survival-signaling pathways related to MCL-1 expression in MM cells. shRNAs silencing of STAT3, PI3K and MAPK2 together could provide an effective strategy to treat MM.

Circumvention of Mcl-1-dependent drug resistance by simultaneous Chk1 and MEK1/2 inhibition in human multiple myeloma cells

The anti-apoptotic protein Mcl-1 plays a major role in multiple myeloma (MM) cell survival as well as bortezomib- and microenvironmental forms of drug resistance in this disease. Consequently, there is a critical need for strategies capable of targeting Mcl-1-dependent drug resistance in MM. The present results indicate that a regimen combining Chk1 with MEK1/2 inhibitors effectively kills cells displaying multiple forms of drug resistance stemming from Mcl-1 up-regulation in association with direct transcriptional Mcl-1 down-regulation and indirect disabling of Mcl-1 anti-apoptotic function through Bim up-regulation and increased Bim/Mcl-1 binding. These actions release Bak from Mcl-1, accompanied by Bak/Bax activation. Analogous events were observed in both drug-naïve and acquired bortezomib-resistant MM cells displaying increased Mcl-1 but diminished Bim expression, or cells ectopically expressing Mcl-1. Moreover, concomitant Chk1 and MEK1/2 inhibition blocked Mcl-1 up-regulation induced by IL-6/IGF-1 or co-culture with stromal cells, effectively overcoming microenvironment-related drug resistance. Finally, this regimen down-regulated Mcl-1 and robustly killed primary CD138+ MM cells, but not normal hematopoietic cells. Together, these findings provide novel evidence that this targeted combination strategy could be effective in the setting of multiple forms of Mcl-1-related drug resistance in MM.

Mechanism of immunomodulatory drugs' action in the treatment of multiple myeloma

Although immunomodulatory drugs (IMiDs), such as thalidomide, lenalidomide, and pomalidomide, are widely used in the treatment of multiple myeloma (MM), the molecular mechanism of IMiDs' action is largely unknown. In this review, we will summarize recent advances in the application of IMiDs in MM cancer treatment as well as their effects on immunomodulatory activities, anti-angiogenic activities, intervention of cell surface adhesion molecules between myeloma cells and bone marrow stromal cells, anti-inflammatory activities, anti-proliferation, pro-apoptotic effects, cell cycle arrest, and inhibition of cell migration and metastasis. In addition, the potential IMiDs' target protein, IMiDs' target protein's functional role, and the potential molecular mechanisms of IMiDs resistance will be discussed. We wish, by presentation of our naive discussion, that this review article will facilitate further investigation in these fields.

Targeting the apoptosis pathway in hematologic malignancies

Apoptosis is a cell death program that is well-orchestrated for normal tissue homeostasis and for removal of damaged, old or infected cells. It is regulated by intrinsic and extrinsic pathways. The intrinsic pathway responds to signals such as ultraviolet radiation or DNA damage and activates "executioner" caspases through a mitochondria-dependent pathway. The extrinsic pathway is activated by death signals induced, for example, by an infection that activates the immune system or receptor-mediated pathways. The extrinsic pathway signals also cascade down to executioner caspases that cleave target proteins and lead to cell death. Strict control of cellular apoptosis is important for the hematopoietic system as it has a high turnover rate. However, the apoptosis program is often deregulated in hematologic malignancies leading to the accumulation of malignant cells. Therefore, apoptosis pathways have been identified for the development of anticancer therapeutics. We review here the proteins that have been targeted for anticancer drug development in hematologic malignancies. These include BCL-2 family proteins, death ligands and receptors, inhibitor of apoptosis family proteins and caspases. Except for caspase activators, drugs that target each of these classes of proteins have advanced into clinical trials.

Triptolide induces apoptotic cell death of multiple myeloma cells via transcriptional repression of Mcl-1

Triptolide, a diterpenoid trioxide purified from the Chinese herb Tripterygium wilfordii Hook F, has been used as a natural medicine in China for hundreds of years. Several reports have demonstrated that triptolide inhibits the proliferation of cancer cells in vitro and reduces the growth of several types of tumors in vivo. To address the potential of triptolide as a novel therapeutic agent for patients with multiple myeloma, we investigated the effects of triptolide on the induction of apoptosis in human multiple myeloma cells in vitro. Triptolide rapidly induces apoptotic cell death in various myeloma cell lines. Triptolide-induced apoptosis in myeloma cells is associated with the loss of mitochondrial transmembrane potential (∆ψm), the release of cytochrome c and Smac/DIABLO from mitochondria into the cytosol, and the activation of caspase-3 and caspase-9. Furthermore, triptolide induces a rapid decline in the levels of Mcl-1 protein that correlates with caspase activation and induction of apoptosis. Inhibition of Mcl-1 synthesis by triptolide occurs at the level of mRNA transcription and is associated with an inhibition of phosphorylation of RNA polymerase II CTD. These results indicate that Mcl-1 is an important target for triptolide-induced apoptosis in myeloma cells that occurs via inhibition of Mcl-1 mRNA transcription coupled with rapid protein degradation through the ubiquitin-proteasome pathway.

CD38 ligation in peripheral blood mononuclear cells of myeloma patients induces release of protumorigenic IL-6 and impaired secretion of IFNγ cytokines and proliferation

CD38, a surface receptor that controls signals in immunocompetent cells, is densely expressed by cells of multiple myeloma (MM). The immune system of MM patients appears as functionally impaired, with qualitative and quantitative defects in T cell immune responses. This work answers the issue whether CD38 plays a role in the impairment of T lymphocyte response. To this aim, we analyzed the signals implemented by monoclonal antibodies (mAb) ligation in peripheral blood mononuclear cells (PBMC) obtained from MM patients and compared to benign monoclonal gammopathy of undetermined significance (MGUS). PBMC from MM both failed to proliferate and secrete IFNγ induced by CD38 ligation while it retained the ability to respond to TCR/CD3. The impaired CD38-dependent proliferative response likely reflects an arrest in the progression of cell cycle, as indicated by the reduced expression of PCNA. CD38 signaling showed an enhanced ability to induce IL-6 secretion. PBMC from MM patients displays a deregulated response possibly due to defects of CD38 activation pathways and CD38 may be functionally involved in the progression of this pathology via the secretion of high levels of IL-6 that protects neoplastic cells from apoptosis.

Apoptotic machinery diversity in multiple myeloma molecular subtypes

Multiple myeloma (MM) is a plasma-cell (PC) malignancy that is heterogeneous in its clinical presentation and prognosis. Monoclonal gammopathy of undetermined significance (MGUS) consistently preceded development of MM. The presence of primary IgH translocations and the universal overexpression of cyclin D genes led to a molecular classification of MM patients into different disease subtypes. Since Bcl-2 family proteins determine cell fate, we analyzed a publicly available Affymetrix gene expression of 44 MGUS and 414 newly diagnosed MM patients to investigate (1) the global change of Bcl-2 family members in MM versus MGUS (2) whether the four major subtypes defined as hyperdiploid, CyclinD1, MAF, and MMSET, display specific apoptotic machineries. We showed that among the main anti-apoptotic members (Bcl-2, Bcl-x_L, and Mcl-1), Mcl-1 up-regulation discriminated MM from MGUS, in agreement with the prominent role of Mcl-1 in PC differentiation. Surprisingly, the expression of multi-domain pro-apoptotic Bak and Bax were increased during the progression of MGUS to MM. The combined profile of Bcl-2, Bcl-x_L, and Mcl-1 was sufficient to distinguish MM molecular groups. While specific pro-apoptotic members expression was observed for each MM subtypes, CyclinD1 subgroup, was identified as a particular entity characterized by a low expression of BH3-only (Puma, Bik, and Bad) and multi-domain pro-apoptotic members (Bax and Bak). Our analysis supports the notion that MM heterogeneity is extended to the differential expression of the Bcl-2 family content in each MM subgroup. The influence of Bcl-2 family profile in the survival of the different patient groups will be further discussed to establish the potential consequences for therapeutic interventions. Finally, the use of distinct pro-survival members in the different steps of immune responses to antigen raises also the question of whether the different Bcl-2 anti-apoptotic profile could reflect a different origin of MM cells.

AT-101 downregulates BCL2 and MCL1 and potentiates the cytotoxic effects of lenalidomide and dexamethasone in preclinical models of multiple myeloma and Waldenström macroglobulinaemia

Multiple myeloma, the second most common haematological malignancy in the U.S., is currently incurable. Disruption of the intrinsic apoptotic pathway by BCL2 and MCL1 upregulation is observed in >80% of myeloma cases and is associated with an aggressive clinical course. Remarkably, there is no approved drug with the ability to target BCL2 or MCL1. Thus, we investigated the anti-tumour effects of a pan-BCL2 inhibitor, AT-101, which has high binding specificity for BCL2 and MCL1 in preclinical models of plasma cell cancers (Multiple myeloma and Waldenström macroglobulinaemia). Gene expression and immunoblot analysis of six plasma cell cancer models showed upregulation of BCL2 family members. AT-101 was able to downregulate BCL2 and MCL1 in all plasma cell cancer models and induced apoptotic cell death in a caspase-dependent manner by altering mitochondrial membrane permeability. This cytotoxic effect and BCL2 downregulation were further potentiated when AT-101 was combined with lenalidomide/dexamethasone (LDA). NanoString nCounter mRNA quantification and Ingenuity Pathways Analysis revealed differential changes in the CCNA2, FRZB, FYN, IRF1, PTPN11 genes in LDA-treated cells. In summary, we describe for the first time the cellular and molecular events associated with the use of AT-101 in combination with lenalidomide/dexamethasone in preclinical models of plasma cell malignancy.

Targeting Mcl-1 for multiple myeloma (MM) therapy: drug-induced generation of Mcl-1 fragment Mcl-1(128-350) triggers MM cell death via c-Jun upregulation

Myeloid cell leukemia-1 (Mcl-1, HGNC: 6943), a pro-survival member of the Bcl-2 family, plays a crucial role in Multiple Myeloma (MM) pathogenesis and drug resistance, thus representing a promising therapeutic target in MM. A novel strategy to inhibit Mcl-1 activity is the induction of ubiquitin-independent Mcl-1 degradation. Our own and other previous studies have demonstrated caspase-dependent generation of a 28kDa Mcl-1 fragment, Mcl-1(128-350), which inhibits MM cell proliferation and survival. Here, we show that similar to bortezomib, the novel proteasome inhibitors carfilzomib and ixazomib, as well as staurosporine and adaphostin, induce the generation of Mcl-1(128-350) in MM cells. Next, the molecular sequelae downstream of Mcl-1(128-350), which mediate its pro-apoptotic activity, were delineated. Surprisingly, we observed nuclear accumulation of drug-induced or exogenously overexpressed Mcl-1(128-350), followed by elevated mRNA and protein levels of c-Jun, as well as enhanced AP-1 reporter activity. Moreover, drug-induced AP-1 activity was blocked after introducing a point mutation into the highly conserved Mcl-1 caspase-cleavage site Asp127, but not Asp157. Consequently, drug-triggered cell death was significantly decreased in MM cells transfected with Mcl-1 D127A, but not with Mcl-1 D157A. Consistent with these data, treatment with bortezomib triggered c-Jun upregulation followed by apoptosis in Mcl-1(wt/wt), but not Mcl-1(Δ/null) murine embryonic fibroblasts (MEFs). Transfection of a plasmid carrying Mcl-1(wt) into Mcl-1(Δ/null) MEFs restored bortezomib-induced Mcl-1 fragmentation, c-Jun upregulation and AP-1 reporter activity. Finally, our data indicate that drug-induced generation of a pro-apoptotic Mcl-1 fragment followed by c-Jun upregulation may also be a novel therapeutic approach in other tumor entities.

Gene expression-based prediction of myeloma cell sensitivity to histone deacetylase inhibitors

Background:

Multiple myeloma (MM) is still a fatal plasma cell cancer. Novel compounds are currently clinically tested as a single agent in relapsing patients, but in best cases with partial response of a fraction of patients, emphasising the need to design tools predicting drug efficacy. Histone deacetylase inhibitors (HDACi) are anticancer agents targeting epigenetic regulation of gene expression and are in clinical development in MM.

Methods:

To create a score predicting HDACi efficacy, five MM cell lines were treated with trichostatin A (TSA) and gene expression profiles were determined.

Results:

The expression of 95 genes was found to be upregulated by TSA, using paired supervised analysis with Significance Analysis of Microarrays software. Thirty-seven of these 95 genes had prognostic value for overall survival in a cohort of 206 newly diagnosed MM patients and their prognostic information was summed up in a histone acetylation score (HA Score); patients with the highest HA Score had the shorter overall survival. It is worth noting that MM cell lines or patients' primary MM cells with a high HA Score had a significant higher sensitivity to TSA, valproic acid, panobinostat or vorinostat.

Conclusion:

In conclusion, the HA Score allows identification of MM patients with poor survival, who could benefit from HDACi treatment.

Candidate genes of Waldenström's macroglobulinemia: current evidence and research

Waldenström's macroglobulinemia (WM) is a relatively uncommon, indolent malignancy of immunoglobulin M-producing B cells. The World Health Organization classifies it as a lymphoplasmacytic lymphoma and patients typically present with anemia, hepatosplenomegaly and diffuse lymphadenopathies. Historically, the genetic characterization of the disease has been hampered by the relatively low proliferative rate of WM cells, thus making karyotyping challenging. The use of novel technologies such as fluorescence in situ hybridization, gene array, and whole genome sequencing has contributed greatly to establishing candidate genes in the pathophysiology of WM and to identifying potential treatment targets, such as L265P MYD88. The discovery of microRNAs and the recognition of epigenetics as a major modulatory mechanism of oncogene expression and/or oncosuppressor silencing have aided in further understanding the pathogenesis of WM. Once thought to closely resemble multiple myeloma, a cancer of terminally differentiated, immunoglobulin-secreting plasma cells, WM appears to genetically cluster with other indolent B-cell lymphomas such as chronic lymphocytic leukemia/small cell lymphoma. The relative high incidence of familial cases of WM and other B-cell malignancies has been helpful in identifying high-risk gene candidates. In this review, we focus on the established genes involved in the pathogenesis of WM, with special emphasis on the key role of derangement of the nuclear factor kappa B signaling pathway and epigenetic mechanisms.