ABSTRACT
This research explored the synergistic effects and the potential mechanisms of RCE-4 and various nonsteroidal anti-inflammatory drugs (NSAIDs) on the proliferation of cervical cancer Ca Ski cells. The MTT assay and CalcuSyn V2.0 software were used to detect cell proliferation and calculate the combination index (CI); the expression levels of various proteins were analyzed using Western blot assay; mitochondrial membrane potential (MMP) was assessed using JC-1 staining; acridine orange/ethidium bromide (AO/EB) double-fluorescence staining was used to detect the apoptosis of Ca Ski cells; a co-immunoprecipitation (Co-IP) assay was used to analyze the relative content of Bcl-2-Beclin 1 complex in Ca Ski cells. The results demonstrate that the combination of RCE-4 and NSAIDs increases the inhibition of Ca Ski cells compared to the single-RCE-4 group, and celecoxib provided the best synergistic effect among the four NSAIDs tested, with a CI of 0.32. The combination of RCE-4 and celecoxib significantly down-regulated the expression of cyclooxygenase-2 (COX-2) and nuclear transcription factor-κB (NF-κB), and promoted the expression of non-steroidal anti-inflammatory drugs activity gene-1 (NAG-1). In addition, autophagy induced by RCE-4 was markedly inhibited in combination with celecoxib, which was associated with down-regulation of the expression of microtubule-associated protein 3 (LC3)-II, Beclin 1, p62 and autophagy-related gene (ATG) 3/4B/5/7/14. RCE-4-induced apoptosis was significantly enhanced by altering the depolarization of mitochondrial membrane potential and the expression of B cell lymphoma-2 (Bcl-2), B cell lymphoma-xl (Bcl-xl), Bcl-2 associated X protein (Bax), Bcl-2/Bcl-xl-associated death promoter (Bad) and cleaved cysteinyl aspartate specific proteinase (cleaved-caspase) 3/7/9. Furthermore, the formation of the Bcl-2-Beclin 1 complex was significantly inhibited in Ca Ski cells treated with RCE-4 in combination with celecoxib. Taken together, this research shows that the combination of RCE-4 and celecoxib has a significant synergistic effect on the proliferation of Ca Ski cells by promoting apoptosis, inhibiting autophagy and disturbing the formation of the Bcl-2-Beclin 1 complex, which may be a novel strategy to increase the sensitivity of anti-cervical cancer drugs.