Abstract.The small molecule multi-kinase inhibitor sorafenib has become the standard systemic treatment for patients with advanced hepatocellular carcinoma (HCC) and renal cell carcinoma. Similar to other kinase inhibitors, drug resistance hinders its clinical use; thus, combination therapy to improve sorafenib sensitivity is a promising approach. The present study shows for the first time that the combination of sorafenib and wogonin exerts a significant potentiation of cytotoxicity in a number of human HCC cell lines in a dose-dependent manner. Enhanced cell death was due to potentiation of apoptosis, which was demonstrated by increased apoptotic cell populations, caspase activation and suppression of cell death by the pan-caspase inhibitor carbobenzoxy-valyl-alanyl-aspartyl. Sorafenib induced autophagy activation, which was shown by autophagic flux. Suppression of autophagy with the autophagy inhibitors chloroquine or 3-methyladenine significantly enhanced cytotoxicity, suggesting that sorafenib-induced autophagy is cytoprotective. Notably, wogonin effectively inhibited sorafenib-induced autophagy. Altogether, our results indicate that the combination of wogonin and sorafenib effectively kills human HCC cells. This occurs, at least in part, through autophagy inhibition, which potentiates apoptosis. Thus, wogonin could be an ideal candidate for increasing sorafenib's activity in HCC therapy, which warrants further investigation in vivo.
Sorafenib is a small-molecule multi-kinase inhibitor approved by FDA as an oral agent for the treatment of hepatocellular carcinoma (HCC) and renal cell carcinoma. However, unresponsiveness and acquired resistance are commonly observed, which hinder the clinical use of sorafenib. As combination therapy is a promising approach to improve its efficacy, we investigated if sorafenib and luteolin combination is effective in killing human HCC cells. Cell death was examined by lactate dehydrogenase (LDH) releasing assay. Apoptosis was detected by flow cytometric. The activation of apoptotic pathway and c-Jun N-terminal kinase (JNK) signaling pathway was measured by western blot. The results showed that sorafenib and luteolin combination synergistically induced cytotoxicity in HCC cells, which was accompanied by potentiation of apoptosis as demonstrated by increased apoptotic cell populations, caspase activation, and suppression of cell death by the pan-caspase inhibitor z-VAD-fmk. Furthermore, the combination of both agents enhanced expression of phosphorylated form of JNK, and the JNK inhibitor SP600125 effectively attenuated cell death induced by the combination treatment. Thus, sorafenib and luteolin combination synergistically kills HCC cells through JNK-mediated apoptosis, and luteolin may be an ideal candidate for increasing the activity of sorafenib in HCC therapy.
Exosomes, which are small extracellular vesicles, have been unveiled to carry circular RNAs (circRNAs). CircRNA paired-related homeobox 1 (circPRRX1) can be transferred by exosomes derived from gastric cancer cells. Here, we investigated the activity and mechanism of exosomal circPRRX1 in gastric tumorigenesis and radiation sensitivity. CircPRRX1, microRNA (miR)-596, and NF-κB activating protein (NKAP) were quantified by quantitative real-time PCR and immunoblotting. Cell proliferation, motility, and invasion were detected by 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2-H-tetrazolium bromide and transwell assays, respectively. Cell colony formation and survival were assessed by colony formation assays. Dual-luciferase reporter assays were performed to verify the direct relationship between miR-596 and circPRRX1 or NKAP. In-vivo xenograft studies were used to evaluate the role of exosomal circPRRX1 in tumor growth. Our data showed that circPRRX1 expression was elevated in human gastric cancer, and circPRRX1 could be transferred by exosomes from gastric cancer cells. Exosomal circPRRX1 affected cell proliferation, motility, invasion, and radiation sensitivity in vitro and tumor growth in vivo. Mechanistically, circPRRX1 directly regulated miR-596 expression, and exosomal circPRRX1 affected cell biological functions at least in part through miR-596. NKAP was identified as a direct target and functionally downstream effector of miR-596. Exosomal circPRRX1 modulated NKAP expression by acting as a competing endogenous RNA (ceRNA) for miR-596. Our findings suggest a new mechanism, the exosomal circPRRX1/ miR-596/NKAP ceRNA crosstalk, in regulating gastric tumorigenesis and radiation sensitivity. Anti-Cancer Drugs 33: 1114
Rong et al.: Effect of Shikonin on the Oxidative Damage of Lung Cancer Cells To investigate the effect of shikonin on the oxidative damage of lung cancer cells and promotes cell senescence through p53/p21Waf signaling pathway. The lung adenocarcinoma A549 cells were cultured and made into cell suspension. The lung adenocarcinoma A549 cells were cultured for 12 h, 24 h and 48 h respectively with different concentrations of shikonin (0 μm, 2 μm and 4 μm) and the activity of lung adenocarcinoma A549 cells was detected by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide method. The cell cycle of each group was measured by flow cytometry after 48 h of action of shikonin. The aging of each group of cells was determined by beta-galactosidase staining after 48 h of action of shikonin. The reactive oxygen species content in each group was determined by flow cytometry 48 h after the action of shikonin. The expression levels of cyclin D1, demethylase KDM2B, deoxyribonucleic acid damage marker protein p-H2AX, p53 and p21WAF were measured by Western blot. With the increase of shikonin concentration, the cell activity and the expression levels of cyclin D1 and KDM2B were significantly decreased, the proportion of resting phase/intermediate phase cells and senescent cells were significantly increased, the level of reactive oxygen species and the expression levels of p-H2AX, p53 and p21WAF were significantly increased (p<0.05). Shikonin can inhibit cell activity, induce oxidative damage and promote cell senescence, which may be achieved by activating p53/p21WAF signaling pathway.
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