Background Dihydroartemisinin (DHA) has been shown to exert anticancer activity through iron-dependent reactive oxygen species (ROS) generation, which is similar to ferroptosis, a novel form of cell death. However, whether DHA causes ferroptosis in glioma cells and the potential regulatory mechanisms remain unclear. Methods Effects of DHA on the proliferation, cell death, ROS and lipid ROS generation as well as reduced gluthione consumption were assessed in glioma cells with or without ferroptosis inhibitor. The biological mechanisms by which glioma cells attenuate the pro-ferroptotic effects of DHA were assessed using molecular methods. Results DHA induced ferroptosis in glioma cells, as characterized by iron-dependent cell death accompanied with ROS generation and lipid peroxidation. However, DHA treatment simultaneously activated a feedback pathway of ferroptosis by increasing the expression of heat shock protein family A (Hsp70) member 5 (HSPA5). Mechanistically, DHA caused endoplasmic reticulum (ER) stress in glioma cells, which resulted in the induction of HSPA5 expression by protein kinase R-like ER kinase (PERK)-upregulated activating transcription factor 4 (ATF4). Subsequent HSPA5 upregulation increased the expression and activity of glutathione peroxidase 4 (GPX4), which neutralized DHA-induced lipid peroxidation and thus protected glioma cells from ferroptosis. Inhibition of the PERK-ATF4-HSPA5-GPX4 pathway using siRNA or small molecules increased DHA sensitivity of glioma cells by increasing ferroptosis both in vitro and in vivo. Conclusions Collectively, these data suggested that ferroptosis might be a novel anticancer mechanism of DHA in glioma and HSPA5 may serve as a negative regulator of DHA-induced ferroptosis. Therefore, inhibiting the negative feedback pathway would be a promising therapeutic strategy to strengthen the anti-glioma activity of DHA.

Background/Aim: Treatment of human non-small-cell lung cancer (NSCLC) often involves uses of multiple therapeutic strategies with different mechanisms of action. Here we found that resveratrol (RV) enhanced the anti-tumor effects of epidermal growth factor receptor (EGFR) inhibitor erlotinib in NSCLC cells. Methods: Cell viability was measured by MTT assay and clonogenicity assay. Western blot was applied to assess the protein expression levels of target genes. Cell apoptosis was monitored by AnnexinV-FITC assay and sub-G1 population assay. Intracellular ROS were measured by flow cytometric analysis. Cell caspase activities were carried out by fluorometric assays. Results: Exposure of H460, A549, PC-9 and H1975 cells to minimal or non-toxic concentrations of RV and erlotinib synergistically reduced cell viability, colony formation and induced cell apoptosis. Furthermore, RV synergistically enhanced erlotinib-induced apoptosis was involved in ROS production. Additionally, co-treatment with RV and erlotinib repressed the expressions of anti-apoptosis proteins, such as survivin and Mcl-1, whereas promoted p53 and PUMA expression and caspase 3 activity. Moreover, the combination was also more effective at inhibiting the AKT/mTOR/S6 kinase pathway. Subsequently, small interfering RNA (siRNA) depletion of PUMA and overexpression of survivin significantly attenuated NSCLC cells apoptosis induced by the combination of the two drugs. Conclusion: Our findings suggested that RV synergistically enhanced the anti-tumor effects of erlotinib in NSCLC cells were involved in decrease of survivin expression and induction of PUMA expression. In conclusion, based on the observations from our study, we indicated that the combined administration of these two drugs might be considered as a novel therapeutic regimen for treating NSCLC.

BackgroundA major challenge in the treatment of pancreatic ductal adenocarcinoma is the failure of chemotherapy, which is likely due to the presence of the cancer stem cells (CSCs).ObjectiveTo identify side population (SP) cells and characterize s-like properties in human pancreatic cancer cell lines (h-PCCLs) and to exploit the efficacy of concomitant targeting of multiple key transcription factors governing the stemness of pancreatic CSCs in suppressing CSC-like phenotypes.MethodsFlow cytometry and Hoechst 33342 DNA-binding dye efflux assay were used to sort SP and non-SP (NSP) cells from three h-PCCLs: PANC-1, SW1990, and BxPc-3. The self-renewal ability, invasiveness, migration and drug resistance of SP cells were evaluated. Expression of CSC marker genes was analyzed. Tumorigenicity was assessed using a xenograft model in nude mice. Effects of a complex decoy oligonucleotide (cdODN-SCO) designed to simultaneously targeting Sox2, Oct4 and c-Myc were assessed.ResultsCSCs were enriched in the side proportion (SP) cells contained in the h-PCCLs and they possessed aggressive growth, invasion, migration and drug-resistance properties, compared with NSP cells. SP cells overexpressed stem cell markers CD133 and ALDH1, pluripotency maintaining factors Nanog, Sox2 and Oct4, oncogenic transcription factor c-Myc, signaling molecule Notch1, and drug resistant gene ABCG2. Moreover, SP cells consistently demonstrated significantly greater tumorigenicity than NSP cells in xenograft model of nude mice. CdODN–SOC efficiently suppressed all CSC properties and phenotypes, and minimized the tumorigenic capability of the SP cells and the resistance to chemotherapy. By comparison, the negative control failed to do so.ConclusionThe findings indicate that targeting the key genes conferring the stemness of CSCs can efficiently eliminate CSC-like phenotypes, and thus may be considered a new approach for cancer therapy. Specifically, the present study establishes the combination of Sox2/Oct4/c-Myc targeting as a potential anti-pancreatic cancer agent worthy of further studies in preclinical settings.

Sulforaphane is recognized as a safe antitumor agent derived from various cruciferous vegetables, including broccoli. It has been demonstrated that sulforaphase is a potent antitumor agent in diverse cancers. However, its effect on hepatocellular carcinoma remains largely unknown. Here, we show that sulforaphane inhibits TGF-β-induced epithelial-mesenchymal transition of hepatocellular carcinoma cell via the reactive oxygen species-dependent pathway. We found sulforaphane inhibited hepatocellular carcinoma cell proliferation in a dose- and time-dependent manner. Sulforaphane induced G0/G1 phase cell cycle arrest and promoted cell apoptosis. A set of experiments showed that sulforaphase inhibited hepatocellular carcinoma cell migration and invasion, inhibited the formation of fibroblast like mesenchymal cells and the expression of Vimentin, but increased the expression of E-cadherin, suggesting sulforaphane suppresses epithelial-mesenchymal transition (EMT) process. Cotreatment with N-acetyl-L-cysteine inhibited sulforaphane-inhibited invasion and upregulation of E-cadherin and almost completely abolished the sulforaphane-induced expression of Vimentin. The effect of sulforaphane on the growth of hepatocellular carcinoma cells was confirmed by a xenograft tumor growth model. All our finding indicated that sulforaphane is a promising and safe strategy for treating hepatocellular carcinoma.

Here, we showed the antibiotic salinomycin (SAL) combined with GEF exerted synergistic cytotoxicity effects in colorectal cancer cells irrespective of their EGFR and KRAS status, with a relatively low toxicity to normal cells. Additionally, combination of the two drugs overcame Ras-induced resistance and the acquired resistance to GEF. Further, we identified a new potential mechanism of this cooperative interaction by showing that GEF and SAL acted together to enhance production of reactive oxygen species (ROS), loss of mitochondrial membrane potential (MMP) and lysosomal membrane potential (LMP). And the ROS contributed the loss of MMP and LMP. We also found that GEF and SAL acted in concert to induce apoptosis via a mitochondrial-lysosomal cross-talk and caspase-independent pathway triggered by cathepsin B and D. Lastly, SAL in combination with GEF sensitized GEF-resistant cells to GEF in a nude mouse xenograft model. This novel combination treatment might provide a potential clinical application to overcome GEF resistance in colorectal cancer.