Autophagy inhibition has been demonstrated to increase the efficacy of conventional chemotherapy. In this study, we identified hederagenin, a triterpenoid derived from Hedera helix, as a potent inhibitor of autophagy and then hypothesized that hederagenin might synergize with chemotherapeutic drugs (e.g., cisplatin and paclitaxel) to kill lung cancer cells. Firstly, we observed that hederagenin induced the increased autophagosomes in lung cancer cells concomitantly with the upregulation of LC3-II and p62, which indicated the impairment of autophagic flux. The colocalization assay indicated hederagenin could not block the fusion of lysosomes and autophagosomes, whereas the lysosomal acidification might be inhibited by hederagenin as revealed by the reduced staining of acidity-sensitive reagents (i.e., Lysotracker and acridine orange). The aberrant acidic environment then impaired the function of lysosome, which was evidenced by the decrease of mature cathepsin B and cathepsin D. Lastly, hederagenin, in agree with our hypothesis, promoted pro-apoptotic effect of cisplatin and paclitaxel with the accumulation of reactive oxygen species (ROS); while the synergistic effect could be abolished by the ROS scavenger, N-acetyl-L-cysteine. These data summarily demonstrated hederagenin-induced accumulation of ROS by blocking autophagic flux potentiated the cytotoxicity of cisplatin and paclitaxel in lung cancer cells.
The protein EPHB4 plays a vital role in various tumor types. However, few studies into the function of circ‐EPHB4 (hsa_circ_0001730) in tumors have been conducted. This study aimed to investigate the functions of circ‐EPHB4 and the underlying mechanism of circ‐EPHB4 in regulating hepatocellular carcinoma (HCC). The expression of circ‐EPHB4 was found to be downregulated in HCC tumor tissues, whereas circ‐EPHB4 overexpression suppressed cell viability, induced apoptosis, and inhibited cell migration and invasion in Huh7 and HepG2 cells. circ‐EPHB4 levels were negatively correlated with tumor weight, size, and metastasis foci in nude mouse models, suggesting circ‐EPHB4 inhibits tumorigenesis, tumor development, and metastasis. In addition, HIF‐1α and PI3K–AKT pathways were markedly affected by circ‐EPHB4 overexpression. HIF‐1α could potentially be the target of circ‐EPHB4. By overexpressing both HIF‐1α and circ‐EPHB4, the antitumor effect of circ‐EPHB4 should be most probably correlated with HIF‐1α. In conclusion, circ‐EPHB4 is a tumor inhibitor in HCC and functions by inhibiting HIF‐1α expression.
Dioscin is a natural steroidal saponin that can be isolated from Chinese medicine, such as Dioscoreae rhizoma. It has wild range of pharmacological activities such as hepatoprotection, a lipid-lowering effect, and anti-inflammation. Recently, mounting studies reported the anticancer effect of dioscin on a variety of tumor cells. However, the potential effect of dioscin on the epithelial-mesenchymal transition (EMT) of HepG2 cells is unclear. In the present study, dioscin was identified to inhibit transforming growth factor-β1 (TGF-β1) and induced invasive and migratory behavior of HepG2 cells. Consistently, the expression of the epithelial marker E-cadherin and gap junction proteins increased following dioscin treatment, while mesenchymal markers decreased, including N-cadherin, Vimentin, Snail, and Slug. Furthermore, we discovered that TGF-β1 induces phosphorylation of JNK, p38, and Erk, whereas the activation of these kinases was reversed by dioscin treatment in a dose-dependent manner. With the addition of Asiatic acid, a p38 activator, the inhibitory effect of dioscin on EMT was reversed. Taken together, these data indicated that dioscin inhibits EMT in HepG2 cells, which is mediated in large part by inhibition of the p38-MAPK signaling.
Abstract. Tanshinone IIA (Tan IIA), isolated from the Chinese medicinal herb Danshen, has been reported to have anticancer effects in several tumor models, while its effects on renal cell carcinoma have not been studied. In the present study, we evaluated the effects of Tan IIA on growth inhibition and apoptosis in the renal cancer cell line 786-O and its mechanism of action. Results of the MTT assay indicated that the treatment of 786-O cells with Tan IIA resulted in a concentration-dependent decrease in cell viability. Flow cytometry analysis revealed that Tan IIA treatment caused apoptosis following cell cycle perturbation. Furthermore, we examined the expression of cell cycle and apoptosis-related proteins using immunoblotting, which indicated an upregulation of p53, p21, bax and caspase-3 in Tan IIA-treated cells compared with Tan IIA-untreated cells. These results suggest that the activation of p53 and the upregulation of its target genes, including p21 and bax, may be involved in the mitochondrial apoptosis induced by Tan IIA in 786-O cells.
Identification of safe, effective radiosensitizing agents is urgently needed to improve the outcome of radiotherapy in nasopharyngeal cancer (NPC). In this study, we assessed the ability of the polyphenol resveratrol to act as a radiosensitizer in vitro and in vivo. CNE-1 cells were treated with 50 µM resveratrol for 24 h, then irradiated. E2F transcription factor 1 (E2F1) was stably knocked down and overexpressed using lentiviruses. A xenograft model of NPC was established in nude mice using CNE-1 cells. Compared to control DMSO‑treated CNE-1 cells, resveratrol inhibited colony-forming ability and induced G1 phase cell cycle arrest. Radiation survival curves confirmed resveratrol significantly sensitized CNE-1 cells, and resveratrol in combination with 2 Gy irradiation synergistically increased apoptosis. Immunoblotting showed resveratrol dose- and time-dependently downregulated E2F1 and phospho-AKT (p-AKT). Knockdown of E2F1 significantly increased radiosensitivity and downregulated p-AKT; overexpression of E2F1 reversed resveratrol-induced radiosensitivity and upregulated p-AKT. In vivo, 50 mg/kg/day resveratrol and 4 Gy irradiation led to significantly lower tumor volume and tumor weight compared to resveratrol or irradiation alone. Our findings show that resveratrol increases the radiosensitivity of NPC cells by downregulating E2F1 and inhibiting p-AKT, and therefore has potential as a radiosensitizer for NPC.
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