RKIP promotes cisplatin-induced gastric cancer cell death through NF-κB/Snail pathway

Investigation on the mechanism of the combination of eremias multiocellata and cisplatin in reducing chemoresistance of gastric cancer based on in vitro and in vivo experiments

BACKGROUND

Cisplatin (DDP) is one of the important chemotherapy drugs for patients with advanced gastric cancer and metastasis, but its resistance is a bottleneck problem that affects clinical efficacy and patient survival. Eremias multiocellata (EM) is a traditional Chinese herbal medicine, which has been used in the treatment of precancerous lesions, gastric cancer, liver fibrosis, and other digestive diseases. However, the mechanism of reducing chemotherapy resistance to gastric cancer is still unclear.

METHODS

We used the MTT assay to evaluate the proliferative viability of gastric cancer parental cell line MKN45 and its drug-resistant cell line MKN45/DDP, and compared their drug-resistance indices. The migration and invasion abilities of MKN45/DDP drug-resistant cells were evaluated using the Transwell assay. Apoptosis in MKN45/DDP drug-resistant cells was detected using flow cytometry. The effect of a combination of EM and cisplatin on the levels of reactive oxygen species (ROS) and lipid peroxides (LPO) in cisplatin-resistant gastric cancer cells was detected using ROS fluorescent probes and a lipid peroxidation assay kit in conjunction with flow cytometry. The effect of EM combined with cisplatin on the level of iron ions was detected by fluorescence probe and confocal laser technique. Hematoxylin-eosin staining (HE staining) was used to detect the histopathologic morphology of drug-resistant gastric cancer in nude mice. Ferroptosis-related proteins were measured using immunohistochemistry. Real-time fluorescence quantitative polymerase chain reaction (RT-qPCR) was used to detect tumor drug resistance-related genes. The NF-κB/Snail pathway-related proteins, PI3K/AKT/mTOR pathway-related proteins, and drug resistance-related proteins were detected by Western blot.

RESULTS AND CONCLUSIONS

The results of in vitro and in vivo experiments showed that EM combined with DDP could effectively inhibit the migration and invasive ability of MKN45/DDP cells, as well as induce apoptosis of MKN45/DDP cells; the combination of the two drugs could significantly increase the levels of ROS, lipid peroxidation and divalent ferric ions in MKN45/DDP cells, at the same time reducing the levels of Ferroptosis-related proteins, which could induce Ferroptosis. In addition, EM combined with DDP can also exert the effect of reversing DDP resistance and increasing the sensitivity of gastric cancer drug-resistant cells to DDP by regulating the NF-κB/Snail signaling pathway, PI3K/AKT/mTOR signaling pathway, and the expression of drug resistance-related proteins and genes.

Polyphyllin I and VII potentiate the chemosensitivity of A549/DDP cells to cisplatin by enhancing apoptosis, reversing EMT and suppressing the CIP2A/AKT/mTOR signaling axis

Poor response and resistance to cisplatin (DDP)-based chemotherapy frequently leads to treatment failure in advanced non-small cell lung cancer (NSCLC). The underlying molecular mechanism is extremely complex and currently remains unclear. The overexpression of cancerous inhibitor of protein phosphatase 2A (CIP2A) indicates poor prognosis and promotes the epithelial-to-mesenchymal transition (EMT) and metastasis. The EMT has been reported to promote drug resistance in numerous previous studies. CIP2A and its downstream protein kinase B (AKT)/mammalian target of rapamycin (mTOR) pathway also plays a role in mediating DDP resistance. Polyphyllin I (PPI) and polyphyllin VII (PPVII) are natural components extracted from Paris polyphylla that display anti-cancer properties. In the present study, the chemosensitizing effects of PPI and PPVII were investigated in the DDP-resistant NSCLC cell line A549/DDP, as well as the underlying molecular mechanisms. The results demonstrated that PPI and PPVII could significantly inhibit cell proliferation and enhance the sensitivities of A549/DDP cells to DDP. When assessing the underlying molecular mechanism, it was revealed that PPI and PPVII enhanced DDP-induced apoptosis in A549/DDP cells via p53 upregulation and the caspase-dependent pathway. Furthermore, PPI and PPVII reversed the EMT and suppressed CIP2A and its downstream AKT/mTOR signaling cascade in A549/DDP cells. Overall, the results from the present study demonstrated that PPI and PPVII may function as chemosensitizers by enhancing apoptosis via the p53 pathway, reversing EMT and suppressing the CIP2A/AKT/mTOR signaling axis, and the combination with DDP may be a promising strategy for the development of new therapeutic agents.

Reduced RKIP enhances nasopharyngeal carcinoma radioresistance by increasing ERK and AKT activity

Raf kinase inhibitory protein (RKIP) functions as a chemo-immunotherapeutic sensitizer of cancers, but regulation of RKIP on tumor radiosensitivity remains largely unexplored. In this study, we investigate the role and mechanism of RKIP in nasopharyngeal carcinoma (NPC) radioresistance. The results showed that RKIP was frequently downregulated in the radioresistant NPC tissues compared with radiosensitive NPC tissues, and its reduction correlated with NPC radioresistance and poor patient survival, and was an independent prognostic factor. In vitro radioresponse assay showed that RKIP overexpression decreased while RKIP knockdown increased NPC cell radioresistance. In the NPC xenografts, RKIP overexpression decreased while RKIP knockdown increased tumor radioresistance. Mechanistically, RKIP reduction promoted NPC cell radioresistance by increasing ERK and AKT activity, and AKT may be a downstream transducer of ERK signaling. Moreover, the levels of phospho-ERK-1/2 and phospho-AKT were increased in the radioresistant NPC tissues compared with radiosensitive ones, and negatively associated with RKIP expression, indicating that RKIP-regulated NPC radioresponse is mediated by ERK and AKT signaling in the clinical samples. Our data demonstrate that RKIP is a critical determinant of NPC radioresponse, and its reduction enhances NPC radioresistance through increasing ERK and AKT signaling activity, highlighting the therapeutic potential of RKIP-ERK-AKT signaling axis in NPC radiosensitization.

Paris Saponin I Sensitizes Gastric Cancer Cell Lines to Cisplatin via Cell Cycle Arrest and Apoptosis

BACKGROUND Dose-related toxicity is the major restriction of cisplatin and cisplatin-combination chemotherapy, and is a challenge for advanced gastric cancer treatment. We explored the possibility of using Paris saponin I as an agent to sensitize gastric cancer cells to cisplatin, and examined the underlying mechanism. MATERIAL AND METHODS Growth inhibition was detected by MTT assay. The cell cycle and apoptosis were detected using flow cytometry and Annexin V/PI staining. The P21waf1/cip1, Bcl-2, Bax, and caspase-3 protein expression were detected using Western blot analysis. RESULTS The results revealed that PSI sensitized gastric cancer cells to cisplatin, with low toxicity. The IC50 value of cisplatin in SGC-7901 cell lines was decreased when combined with PSI. PSI promoted cisplatin-induced G2/M phase arrest and apoptosis in a cisplatin concentration-dependent manner. Bcl-2 protein expression decreased, but Bax, caspase-3, and P21waf1/cip1 protein expression increased with PSI treatment. CONCLUSIONS The underlying mechanism of Paris saponin I may be related to targeting the apoptosis pathway and cell cycle blocking, which suggests that PSI is a potential therapeutic sensitizer for cisplatin in treating gastric cancer.