BIM-Mediated AKT Phosphorylation Is a Key Modulator of Arsenic Trioxide-Induced Apoptosis in Cisplatin-Sensitive and -Resistant Ovarian Cancer Cells

Abstract

BackgroundChemo-resistance to cisplatin-centered cancer therapy is a major obstacle to the effective treatment of human ovarian cancer. Previous reports indicated that arsenic trioxide (ATO) induces cell apoptosis in both drug-sensitive and -resistant ovarian cancer cells.Principal FindingsIn this study, we determined the molecular mechanism of ATO-induced apoptosis in ovarian cancer cells. Our data demonstrated that ATO induced cell apoptosis by decreasing levels of phosphorylated AKT (p-AKT) and activating caspase-3 and caspase-9. Importantly, BIM played a critical role in ATO-induced apoptosis. The inhibition of BIM expression prevented AKT dephosphorylation and inhibited caspase-3 activation during cell apoptosis. However, surprisingly, gene silencing of AKT or FOXO3A had little effect on BIM expression and phosphorylation. Moreover, the activation of caspase-3 by ATO treatment improved AKT dephosphorylation, not only by cleaving the regulatory A subunit of protein phosphatase 2A (PP2A), but also by increasing its activation. Furthermore, our data indicated that the c-Jun N-terminal kinases (JNK) pathway is involved in the regulation of BIM expression.ConclusionsWe demonstrated the roles of BIM in ATO-induced apoptosis and the molecular mechanisms of BIM expression regulated by ATO during ovarian cancer cell apoptosis. Our findings suggest that BIM plays an important role in regulating p-AKT by activating caspase-3 and that BIM mediates the level of AKT phosphorylation to determine the threshold for overcoming cisplatin resistance in ovarian cancer cells.

Inhibition of rapamycin-induced Akt phosphorylation by cotylenin A correlates with their synergistic growth inhibition of cancer cells

“…Therefore, new strategies to enhance the efficacy of ATO, while reducing the dose of ATO in order to avoid severe side-effects, are essential. Previous reports showed that ATO decreased not only Akt activity but also total Akt protein and that the sensitivity to ATO correlated with the degree of Akt protein reductions in leukemia cells, prostate cancer cells, and ovarian cancer cells (25)(26)(27). In this study, we found that ATO at lower doses could inhibit Rapa-induced phosphorylation of Akt (Ser473) in MCF-7 cells, and that ATO and Rapa synergistically inhibited the proliferation of MCF-7 cells (Fig.…”

“…6A). Arsenic trioxide (ATO) is also known to inhibit phosphorylation of Akt in several solid tumor cells (25)(26)(27). Therefore, we examined the effect of ATO on Rapa-induced phosphorylation of Akt (Ser473) and Rapa-induced growth inhibition of MCF-7 cells.…”

Proapoptotic Protein Smac Mediates Apoptosis in Cisplatin-resistant Ovarian Cancer Cells When Treated with the Anti-tumor Agent AT101

“…Cell Fractionation-Mitochondria and cytoplasm from cells were fractionated by differential centrifugation as described previously (20,22). Briefly, cells were harvested and resuspended in 3 volumes of hypotonic buffer (210 mM sucrose, 70 mM mannitol, 10 mM Hepes, pH 7.4, 1 mM EDTA) containing 1 mM phenylmethylsulfonyl fluoride, 50 mg/ml trypsin inhibitor, 10 mg/ml leupeptin, 5 mg/ml aprotinin, and 10 mg/ml pepstatin.…”

High BIM mRNA levels are associated with longer survival in advanced gastric cancer

“…In a previous study by the present authors, the median OS was 25.8 months for patients with high messenger RNA (mRNA) expression levels of breast cancer susceptibility gene 1 (BRCA1) treated with second-line docetaxel-based chemotherapy (6). Recent evidence also suggests that an underlying cause of drug resistance may be the failure of drug-induced apoptosis (7)(8)(9). Platinum treatment initiates apoptosis through the formation of DNA adducts, which primarily form intrastrand crosslinks that activate the apoptotic pathway, eventually resulting in cell death (10,11).…”