Synergistic effects of valproic acid and arsenic trioxide on RPMI8226 cells in vitro and the possible underlying mechanisms

Abstract

Abstract. The aim of the present study was to investigate the synergistic effects of valproic acid (VPA) and arsenic trioxide (ATO) on the proliferation of RPMI8226 cells and the possible underlying mechanisms. Cell apoptosis was assessed by flow cytometry. The mRNA expression levels were analyzed by semi-quantitative polymerase chain reaction, and the protein expression levels were analyzed by western blotting. The histone acetylation and methylation states of the gene promoters were detected using a chromatin immunoprecipitation technique. The apoptotic rates of the RPMI8226 cells in the combined drug groups were significantly increased compared with those of the single drug groups (P<0.05). The mRNA and protein expression levels of Bcl-2 and the expression levels of HDAC1 mRNA and H3K9me2 protein decreased significantly in the combined groups compared with the single drug groups. The mRNA and protein expression levels of Bax, Caspase 8, Caspase 9 and LSD1, and the protein expression of acetylated H3 increased significantly in the combination groups compared with the single drug groups. Histone methylation and acetylation of the Bcl-2 and bax gene promoters were increased in the combination groups compared with the single drug groups. VPA and ATO had synergistic effects on the proliferation of RPMI8226 cells, which may have been associated with the decreased expression of Bcl-2 and the increased expression levels of Bcl-2-associated X protein, Caspase 8 and Caspase 9. Therefore, the expression levels of the Bcl-2 gene family may have been regulated by the levels of gene promoter methylation and acetylation. IntroductionMultiple myeloma (MM) is a plasma cell disorder, characterized by anemia, renal disease, lytic bone disease, and immune dysfunction. MM is one of the most common types of hematological malignancy in China (1). Although currently approved treatments for newly diagnosed MM, including high-dose chemotherapy followed by autologous transplantation, and novel drugs, including proteasome inhibitors and immunomodulatory agents (IMiDs), have led to increased survival rates, the majority of patients will eventually relapse and become refractory to treatment (2). Therefore, patients with relapsed or refractory MM have an unmet requirement for safe and efficacious novel therapies.Arsenic trioxide (ATO) has been suggested as an option for the treatment of relapsing or refractory MM. In vitro, ATO has been found to induced myeloma cell apoptosis, and monotherapy with ATO results in partial response rates between 0 and 17%, and minimal responses between 7 and 33%, resulting in mean overall response rates of 30% for treatment of myeloma (3-5).In order to improve the treatment response rates in patients with MM, ATO has been combined with other novel drugs, including proteasome inhibitors, IMiDs and dexamethsone, for the treatment of MM. The overall response rates in these combined regimens vary widely between 12 and 100% (6-8). It is necessary to identify novel combinations of ATO with other drugs, to offer nov...

Arsenic compounds activate the MAPK and caspase pathways to induce apoptosis in OEC‑M1 gingival epidermal carcinoma

“…Studies have demonstrated that arsenic compounds could only activate the caspase-8 pathway to induce human melanoma cell apoptosis by enhancing TRAIL-induced apoptosis with the suppression of the NF-κB and STAT3-transcriptional targets (59) and could only stimulate the caspase-9 pathway to induce liver cancer cell apoptosis by downregulating phosphorylated-STAT3 expression with Bcl-2, XIAP, and surviving proteins (60), respectively. Studies have also revealed that arsenic compounds could activate both the caspase-8 and caspase-9 pathways concurrently to induce myeloma and promonocytic leukemia cell apoptosis by decreasing the expression of Bcl-2 families and/or regulating p38-MAPK process (61,62). In the present study, NaAsO 2 and DMA could concurrently induce both the caspase-8 and -9 pathways in OEC-M1 cells, indicating that our observations are not unprecedented.…”

“…In the present study, NaAsO 2 and DMA could concurrently induce both the caspase-8 and -9 pathways in OEC-M1 cells, indicating that our observations are not unprecedented. It is well known that up-and downstream of the caspase-8 and -9 pathways, pathways including Fas/Fas ligand, BCL-2, ER stress, and/or p53, are markedly involved with the finer regulation of cancer cell apoptosis (59)(60)(61)(62). Thus, it is worth further investigating how caspase-8 and -9 pathways are regulated by up-and downstream regulators to induce OEC-M1 cell apoptosis.…”

Realgar nanoparticles versus ATO arsenic compounds induce in vitro and in vivo activity against multiple myeloma

“…Several preclinical studies have shown that ATO in combination with (i) signalling inhibitors, including recombinant mutant human TRAIL (Zhou et al , ), PD184352 (Lunghi et al , ), and sulforaphane (SFN) (Doudican et al , ); (ii) oxidative stress pathway modulators [such as AA (Bahlis et al , )]; and (iii) therapeutic drugs [MEL, BTZ (Wen et al , ), imatinib, 5‐azacytidine (Chen et al , ), valproic acid (Wang & Zhang, ) and ATRA] exhibits synergistic anti‐MM activity both in vitro and in vivo . Our previous study shows that SFN, a dietary isothiocyanate found in cruciferous vegetables, has anti‐MM activity associated with induction of apoptosis (Jakubikova et al , ).…”