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.

Liver receptor homolog-1 (LRH1) has been shown to promote tumor proliferation and development. However, the functions of LRH1 in mediating cancer cells chemoresistance are still not clear. Here, we found LRH1 levels were significantly elevated in primary breast cancer tissues in patients who developed early recurrence. Similarly, adriamycin (ADR)-resistant breast cancer cell lines also exerted high LRH1 expression. Indeed, overexpression of LRH1 attenuated cytotoxicity of chemotherapeutic drugs ADR and cisplatin (DDP) in breast cancer cells in vitro and in nude mice tumor model. Comet and BrdU assays showed overexpression of LRH1 blocked breast cancer cells DNA damage by chemotherapeutic drug, whereas depletion of LRH1 enhanced DNA damage. Remarkably, knockdown of LRH1 decreased the levels and foci of DNA damage marker γH2AX induced by ADR and DDP. Furthermore, plasmid end-joining assay indicated that knockdown of LRH1 significantly decreased non-homologous end-joining (NHEJ)-mediated double-strand break (DSB) repair efficiencies. Afterwards, we provided evidences that LRH1 promoted MDC1 transcription by directly activating MDC1 promoter and therefore increased γH2AX levels. Importantly, a LRH1-binding site mapped between -1812 and -1804 bp of the proximal MDC1 promoter was identified. Moreover, LRH1 and MDC1 mRNA levels were positively correlated in recurrent breast cancer samples. These results implied LRH1 enhanced breast cancer cell chemoresistance by upregulating MDC1 and attenuating DNA damage. Additionally, we elucidated the coactivator NCOA3 acted synergistically with LRH1 to promote MDC1 expression and chemoresistance. Altogether, LRH1-MDC1 signaling might be considered as a novel molecular target for designing novel therapeutic regimen in chemotherapy resistance breast cancer.

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Despite recent advances in the therapy of non-small cell lung cancer (NSCLC), the chemotherapy efficacy against NSCLC is still unsatisfactory. Previous studies show the herbal antimalarial drug dihydroartemisinin (DHA) displays cytotoxic to multiple human tumors. Here, we showed that DHA decreased cell viability and colony formation, induced apoptosis in A549 and PC-9 cells. Additionally, we first revealed DHA inhibited glucose uptake in NSCLC cells. Moreover, glycolytic metabolism was attenuated by DHA, including inhibition of ATP and lactate production. Consequently, we demonstrated that the phosphorylated forms of both S6 ribosomal protein and mechanistic target of rapamycin (mTOR), and GLUT1 levels were abrogated by DHA treatment in NSCLC cells. Furthermore, the upregulation of mTOR activation by high expressed Rheb increased the level of glycolytic metabolism and cell viability inhibited by DHA. These results suggested that DHA-suppressed glycolytic metabolism might be associated with mTOR activation and GLUT1 expression. Besides, we showed GLUT1 overexpression significantly attenuated DHA-triggered NSCLC cells apoptosis. Notably, DHA synergized with 2-Deoxy-D-glucose (2DG, a glycolysis inhibitor) to reduce cell viability and increase cell apoptosis in A549 and PC-9 cells. However, the combination of the two compounds displayed minimal toxicity to WI-38 cells, a normal lung fibroblast cell line. More importantly, 2DG synergistically potentiated DHA-induced activation of caspase-9, -8 and -3, as well as the levels of both cytochrome c and AIF of cytoplasm. However, 2DG failed to increase the reactive oxygen species (ROS) levels elicited by DHA. Overall, the data shown above indicated DHA plus 2DG induced apoptosis was involved in both extrinsic and intrinsic apoptosis pathways in NSCLC cells.