Aspirin inhibits proliferation and induces apoptosis of multiple myeloma cells through regulation of Bcl-2 and Bax and suppression of VEGF.

OBJECTIVES: Aspirin (ASA) has been frequently used for thromboprophylaxis in patients with multiple myeloma (MM) when treated with thalidomide or lenalidomide. Despite the well-recognized chemopreventive role of ASA in some solid tumors particularly for colon cancer, whether ASA displays the antimyeloma activity remains unclear. METHODS: MM1.S and RPMI-8226 cell lines harboring K-Ras and N-Ras mutation, respectively, were treated with various concentrations of ASA for different hours. The cell proliferation and apoptosis were performed to explore the effects of ASA on myeloma. Then, the exact mechanisms governing ASA's antimyeloma were explored by qRT-PCR and Western blot. Also, the effect of ASA on tumor growth was observed in NOD/SCID mice bearing myeloma xenografts. RESULTS: ASA of 0-10 mm concentration inhibits proliferation MM1.S and RPMI-8226 cells in time- and dose-dependent manner. The myeloma cells exposed to ASA treatment displayed concentration-dependent apoptosis, which was closely associated with activation of caspases, upregulation of Bax, and downregulation of Bcl-2 and VEGF. Study in vivo revealed that ASA administration retarded the tumor growth accompanying the survival time of mice bearing myeloma xenografts. CONCLUSIONS: ASA exerted antiproliferative and pro-apoptotic action in myeloma cells in vitro and delayed the growth of human myeloma cells in vivo. The underlying mechanisms were ascribed to regulation of Bcl-2 and Bax and suppression of VEGF.

[Effect of PKM2 on Osteogenic and Adipogenic Differentiation of Bone Marrow Mesenchymal Stem Cells in Myeloma Bone Disease].

OBJECTIVE: To investigate the expression of pyruvate kinase M2 (PKM2) in bone marrow mesenchymal stem cells (BMSCs) in myeloma bone disease (MBD) and its effect on osteogenic and adipogenic differentiation of BMSCs. METHODS: BMSCs were isolated from bone marrow of five patients with multiple myeloma (MM) (MM group) and five with iron deficiency anemia (control group) for culture and identification. The expression of PKM2 protein were compared between the two groups. The differences between osteogenic and adipogenic differentiation of BMSCs were assessed by using alkaline phosphatase (ALP) and oil red O staining, and detecting marker genes of osteogenesis and adipogenesis. The effect of MM cell line (RPMI-8226) and BMSCs co-culture on the expression of PKM2 was explored. Functional analysis was performed to investigate the correlations of PKM2 expression of MM-derived BMSCs with osteogenic and adipogenic differentiation by employing PKM2 activator and inhibitor. The role of orlistat was explored in regulating PKM2 expression, osteogenic and adipogenic differentiation of MM-derived BMSCs. RESULTS: Compared with control, MM-originated BMSCs possessed the ability of increased adipogenic and decreased osteogenic differentiation, and higher level of PKM2 protein. Co-culture of MM cells with BMSCs markedly up-regulated the expression of PKM2 of BMSCs. Up-regulation of PKM2 expression could promote adipogenic differentiation and inhibit osteogenic differentiation of MM-derived BMSCs, while down-regulation of PKM2 showed opposite effect. Orlistat significantly promoted osteogenic differentiation in MM-derived BMSCs via inhibiting the expression of PKM2. CONCLUSION: The overexpression of PKM2 can induce the inhibition of osteogenic differentiation of BMSCs in MBD. Orlistat can promote the osteogenic differentiation of BMSCs via inhibiting the expression of PKM2, indicating a potential novel agent of anti-MBD therapy.

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

In our previous study, it was found that aspirin (ASA) exerted antimyeloma actions in vivo and in vitro. The resistance to bortezomib (BTZ) in multiple myeloma (MM) is partly due to AKT activation and the upregulation of survivin induced by BTZ, which are the targets of ASA in gastric and ovarian cancer, respectively. Thus, the present study investigated the interaction between ASA and BTZ in MM and further clarified the underlying mechanisms. MM1.S and RPMI-8226 cell lines harboring the N- and K-Ras mutations, respectively, were treated with 2.5 mM ASA, 10 nM BTZ and ASA+BTZ for different durations. The proliferation and apoptosis of the cells were determined, and the underlying mechanisms governing the interaction of ASA and BTZ were examined in the MM cells. Treatment with ASA+BTZ caused higher rates of proliferative inhibition and apoptosis in the MM1.S and RPMI-8226 cells in time-dependent manner, compared with either agent alone. A drug interaction assay revealed the additive effect of ASA and BTZ on the myeloma cells. ASA alone inhibited the levels of phosphorylated AKT (p-AKT) and survivin, whereas BTZ alone augmented the levels of p-AKT and survivin. Of note, ASA markedly decreased the upregulation of p-AKT and survivin induced by BTZ. Treatment with ASA+BTZ significantly suppressed the level of Bcl-2, compared with either agent alone. ASA may potentiate the antimyeloma activity of BTZ against myeloma cells via suppression of AKT phosphorylation, survivin and Bcl-2, indicating the potential of ASA+BTZ in treating MM, particularly for cases of BTZ-refractory/relapsed MM.

Atrial natriuretic peptide: a possible mediator involved in dexamethasone's inhibition of cell proliferation in multiple myeloma.

Atrial natriuretic peptide (ANP) has been recognized for several decades for its role of regulating blood pressure. Recently, cumulating evidences show that ANP plays an anticancer role in various solid tumors via blocking the kinase cascade of Ras-MEK1/2-ERK1/2 with the result of inhibition of DNA synthesis. ANP, as well as its receptors (NPR-A and NPR-C) has been identified present in the embryonic stem cell and a wide range of cancer cells. Various lymphoid organs, such as lymph nodes, have been detected the presence of ANP. Multiple myeloma (MM), though the therapies have evolved significantly, is still an incurable disease as B lymphocyte cell neoplasm. Dexamethasone is the cornerstone in treatment of MM via inactivation of Ras-MEK1/2-ERK1/2 cascade reaction. Coincidently, dexamethasone can increase the expression of ANP markedly. Nevertheless, the role of ANP in MM is unclear. Based on these results above, we raise the hypothesis that ANP is involved in mediating dexamethasone's inhibition of proliferation in MM cells, which suggests that ANP may be a potential agent to treat MM.