Aspirin enhances the cytotoxic activity of bortezomib against myeloma cells via suppression of Bcl-2, survivin and phosphorylation of AKT

Co-operation of MCL-1 and BCL-XL anti-apoptotic proteins in stromal protection of MM cells from carfilzomib mediated cytotoxicity

Introduction

BCL-2 family proteins are important for tumour cell survival and drug resistance in multiple myeloma (MM). Although proteasome inhibitors are effective anti-myeloma drugs, some patients are resistant and almost all eventually relapse. We examined the function of BCL-2 family proteins in stromal-mediated resistance to carfilzomib-induced cytotoxicity in MM cells.

Methods

Co-cultures employing HS5 stromal cells were used to model the interaction with stroma. MM cells were exposed to CFZ in a 1-hour pulse method. The expression of BCL-2 family proteins was assessed by flow cytometry and WB. Pro-survival proteins: MCL-1, BCL-2 and BCL-XL were inhibited using S63845, ABT-199 and A-1331852 respectively. Changes in BIM binding partners were examined by immunoprecipitation and WB.

Results

CFZ induced dose-dependent cell death of MM cells, primarily mediated by apoptosis. Culture of MM cells on HS-5 stromal cells resulted in reduced cytotoxicity to CFZ in a cell contact-dependent manner, upregulated expression of MCL-1 and increased dependency on BCL-XL. Inhibiting BCL-XL or MCL-1 with BH-3 mimetics abrogated stromal-mediated protection only at high doses, which may not be achievable in vivo. However, combining BH-3 mimetics at sub-therapeutic doses, which alone were without effect, significantly enhanced CFZ-mediated cytotoxicity even in the presence of stroma. Furthermore, MCL-1 inhibition led to enhanced binding between BCL-XL and BIM, while blocking BCL-XL increased MCL-1/BIM complex formation, indicating the cooperative role of these proteins.

Conclusion

Stromal interactions alter the dependence on BCL-2 family members, providing a rationale for dual inhibition to abrogate the protective effect of stroma and restore sensitivity to CFZ.

MicroRNA-744 promotes cell apoptosis via targeting B cell lymphoma-2 in gastric cancer cell line SGC-7901

Gastric cancer (GC) affects the health of 1,000,000 people per year worldwide; however, the biological basis of GC remains largely unknown. The current study aimed to investigate the aberrant expression of miR-744 in GC for the effective treatment of patients with GC. Tumor and adjacent tissues were obtained from 30 patients who underwent tumor resection surgery at Dongying People's Hospital. The results of reverse transcription-quantitative polymerase chain reaction indicated that the expression of miR-744 was significantly decreased in tumor tissues compared with the levels in adjacent tissues. Human gastric cancer cell line SGC-7901 was then randomly divided into three different groups, including the control, miR-negative control (NC) and miR-744 mimic groups. A Cell Counting Kit-8 assay demonstrated that there was a significant decrease in the proliferation rate of SGC-7901 cells in the miR-744 mimics group compared with that observed in the control and miR-NC mimics groups. In addition, flow cytometry demonstrated that apoptosis was significantly increased in the miR-744 mimics group compared with that observed in the control and miR-NC mimics groups. Western blotting indicated that the expression of B cell lymphoma 2 (Bcl-2), B cell lymphoma-2-associated X protein and caspase-3 protein was significantly increased, while the expression of Bcl-2 was significantly decreased in the miR-744 mimics group compared with the levels observed in the control and miR-NC mimics groups. A dual-luciferase assay verified that miR-744 directly targeted the 3'-untranslated region of Bcl-2. Taken together, the present study suggested that miR-744 serves a tumor suppressive role in GC by targeting Bcl-2.

ZIC1 acts a tumor suppressor in breast cancer by targeting survivin

In this study, we aimed to identify the tumor suppressive roles of zinc finger of the cerebellum 1 (ZIC1) in patients with malignant breast neoplasms and to examine the association between ZIC1 and survivin expression. For this purpose, 140 invasive breast cancer specimens, 1,075 RNA breast cancer samples from The Cancer Genome Atlas (TCGA), 6 human breast cancer cell lines and MCF-10A normal breast epithelial cells were selected in order to compare the expression level of ZIC1 with that of survivin via immunohistochemistry and western blot analysis. Subsequently, the MDA-MB-231 and SK-BR3 cells with a lower ZIC1 expression were transfected with rLV-Zic1-PGK-Puro lentivirus or rLV-ZsGreen-PGK-Puro lentivirus in order to observe any alterations in cell proliferation and apoptosis through MTT assay, colony formation assay, mitochondrial membrane potential assay and flow cytometric analysis, and to analyze the modulation of molecular mechanisms by western blot analysis. In addition, xenograft mouse models were constructed to explore the role of ZIC1 in the growth of implanted tumors. The results revealed that ZIC1 negatively correlated with survivin in tumors and cells, and a higher ZIC1 RNA expression indicated a better overall survival in the 1,075 TCGA RNA breast cancer samples. In vitro, the overexpression of ZIC1 inhibited cell proliferation, reduced mitochondrial membrane potential and promoted the apoptosis of the MDA-MB-231 and SK-BR3 breast cancer cells by inactivating the Akt/mTOR/P70S6K pathway, suppressing survivin expression, modulating the cell cycle, releasing cytochrome c (Cyto-c) into the cytosol and activating caspase proteins. In vivo, an elevated ZIC1 expression suppressed the growth of implanted tumors and downregulated survivin expression in tumors. On the whole, the findings of this study demonstrate that ZIC1 plays a tumor suppressive role in breast cancer, by targeting surviving, significantly downregulating its expression.

Antiplatelet agents for cancer treatment: a real perspective or just an echo from the past?

The association between coagulation and cancer development has been observed for centuries. However, the connection between inflammation and malignancy is also well-recognized. The plethora of evidence indicates that among multiple hemostasis components, platelets play major roles in cancer progression by providing surface and granular contents for several interactions as well as behaving like immune cells. Therefore, the anticancer potential of anti-platelet therapy has been intensively investigated for many years. Anti-platelet agents may prevent cancer, decrease tumor growth, and metastatic potential, as well as improve survival of cancer patients. On the other hand, there are suggestions that antiplatelet treatment may promote solid tumor development in a phenomenon described as "cancers follow bleeding." The controversies around antiplatelet agents justify insight into the subject to establish what, if any, role platelet-directed therapy has in the continuum of anticancer management.

Soluble and Cell-Cell-Mediated Drivers of Proteasome Inhibitor Resistance in Multiple Myeloma

It is becoming clear that myeloma cell-induced disruption of the highly organized bone marrow components (both cellular and extracellular) results in destruction of the marrow and support for multiple myeloma (MM) cell proliferation, survival, migration, and drug resistance. Since the first phase I clinical trial on bortezomib was published 15 years ago, proteasome inhibitors (PIs) have become increasingly common for treatment of MM and are currently an essential part of any anti-myeloma combination therapy. PIs, either the first generation (bortezomib), second generation (carfilzomib) or oral agent (ixazomib), all take advantage of the heavy reliance of myeloma cells on the 26S proteasome for their degradation of excessive or misfolded proteins. Inhibiting the proteasome can create a crisis specifically for myeloma cells due to their rapid production of immunoglobulins. PIs have relatively few side effects and can be very effective, especially in combination therapy. If PI resistance can be overcome, these drugs may prove even more useful to a greater range of patients. Both soluble and insoluble (contact mediated) signals drive PI-resistance via activation of various intracellular signaling pathways. This review discusses the currently known mechanisms of non-autonomous (microenvironment dependent) mechanisms of PI resistance in myeloma cells. We also introduce briefly cell-autonomous and stress-mediated mechanisms of PI resistance. Our goal is to help researchers design better ways to study and overcome PI resistance, to ultimately design better combination therapies.

The MIP-1α autocrine loop contributes to decreased sensitivity to anticancer drugs

Several autocrine soluble factors, including macrophage inflammatory protein-1α (MIP-1α), tumor necrosis factor-α, and hepatocyte growth factor, promote cell survival and growth in multiple myeloma (MM) cells. We hypothesized that inhibition of the MIP-1α autocrine loop may enhance the cytotoxic effect of anticancer drugs in MM cell lines. In the present study, an MIP-1α neutralizing antibody suppressed cell proliferation and enhanced the cytotoxic effect of melphalan or bortezomib on MM cells. In addition, melphalan resistance cells (RPMI8226/L-PAM and HS-sultan/L-PAM cells) secreted MIP-1α and neutralizing antibody of MIP-1α partially overcame melphalan resistance. Moreover, combination treatment with MIP-1α neutralizing antibody and melphalan or bortezomib inhibited extracellular signal regulated kinase 1/2 (ERK1/2), Akt, and mammalian target of rapamycin (mTOR) activation, Bcl-2, Bcl-xL, and Survivin expression, and upregulated the expression of Bim and cleaved Poly (ADP-ribose) polymerase (PARP). Treatment of IM9 cells with MIP-1α siRNA suppressed the activation of ERK1/2, Akt, and mTOR, and enhanced the cytotoxic effect of melphalan and bortezomib. These results indicate that MIP-1α neutralizing antibodies or MIP-1α siRNA enhance the cytotoxic effect of melphalan and bortezomib by suppressing the chemokine receptor/ERK and chemokine receptor/Akt/mTOR pathways. The inhibition of MIP-1α may thus provide a new therapeutic approach to control tumor progression and bone destruction in patients with MM.

ClC5 Decreases the Sensitivity of Multiple Myeloma Cells to Bortezomib via Promoting Prosurvival Autophagy

Resistance to bortezomib (BZ) is the major problem that largely limits its clinical application in multiple myeloma treatment. In the current study, we investigated whether ClC5, a member of the chloride channel family, is involved in this process. The MTT assay showed that BZ treatment decreased cell viability in three multiple myeloma cell lines (ARH77, U266, and SKO-007), with IC₅₀ values of 2.83, 4.37, and 1.91 nM, respectively. Moreover, BZ increased the conversion of LC3B-I to LC3B-II and expressions of beclin-1 and ATG5, concomitantly with a decreased p62 expression. Pharmacological inhibition of autophagy with 3-MA facilitated cell death in response to BZ treatment. Additionally, BZ increased ClC5 protein expression in ARH77, U266, and SKO-007 cells. Knockdown of ClC5 with small interfering RNA sensitized cells to BZ treatment, and upregulation of ClC5 induced chemoresistance to BZ. Furthermore, ClC5 downregulation promoted BZ-induced LC3B-I to LC3B-II conversion and beclin-1 expression, whereas overexpression of ClC5 showed the opposite results in ARH77 cells. Finally, BZ induced dephosphorylation of AKT and mTOR, which was significantly attenuated by ClC5 inhibition. However, ClC5 upregulation further enhanced AKT and mTOR dephosphorylation induced by BZ. Our study demonstrates that ClC5 induces chemoresistance of multiple myeloma cells to BZ via increasing prosurvival autophagy by inhibiting the AKT–mTOR pathway. These data suggest that ClC5 may play a critical role in future multiple myeloma treatment strategies.