Ferroptosis-inducing compounds synergize with docetaxel to overcome chemoresistance in docetaxel-resistant non-small cell lung cancer cells.

Development of resistance to therapy-induced cell death is a major hurdle in the effective treatment of advanced solid tumors. Erastin and RSL3 were originally found to induce synthetic lethality by induction of a novel form of cell death termed ferroptosis. Emerging evidence suggests that ferroptosis inducers enhance chemosensitivity of classic therapeutic agents by triggering ferroptotic cell death. In this study we evaluated the effects of erastin and RSL3 on the resistance of docetaxel, doxorubicin, and cisplatin, and revealed a mechanism whereby these ferroptosis inducers augment docetaxel efficacy in non-small cell lung cancer by regulating redox signaling to promote ferroptosis. Transcriptome analysis revealed that combination treatment modulated not only p53 signaling pathway but also immune responses and several signaling pathways including MAPK, NF-κB and PI3K/Akt. Considering that glutathione peroxidase 4 (GPX4) serves as the main effector to protect cells from ferroptosis, this study identified three novel non-covalent GPX4 inhibitors with the aid of pharmacophore-based virtual screening. The new ferroptosis-inducing compounds synergized with docetaxel to increase the cytotoxicity by promoting ferroptotic cell death in docetaxel-resistant A549/DTX cells. Collectively, the induction of ferroptosis contributed to docetaxel-induced cytotoxic effects and overcame drug resistance in A549/DTX cells. Ferroptosis has a great potential to become a new approach to attenuate resistance to some classic therapeutic drugs in cancer patients.

Wip1 contributes to the adaptation of HepG2 human liver cancer cells to stress hormone-induced DNA damage.

Numerous studies have shown that the release of stress hormones resulting from repeated exposure to chronic psychological stress increases DNA damage and promotes tumorigenesis. However, the mechanisms that enable cancerous cells adapt to stress hormone-induced DNA damage and survive remain unclear. The present study aimed to investigate the impact of stress hormones on the survival of liver cancer cells and the underlying mechanism. HepG2 human liver cancer cells were treated with dexamethasone (DEX), epinephrine (EPI) and norepinephrine (NE) and subjected to the testing of DNA damage, cell survival and cell apoptosis by alkaline comet assay, CCK-8 viability assay and flow cytometry, respectively. The protein expression levels of DNA damage response factors were determined by western blotting analysis. The results revealed that treatment of HepG2 cells with DEX, EPI and NE induced DNA damage without affecting cell survival or inducing apoptosis. The protein levels of wild-type p53-induced phosphatase 1 (Wip1), a type 2C family serine/threonine phosphatase, were increased, and the dephosphorylation of DNA damage response factors, including phosphorylated (p-)ataxia-telangiectasia mutated and p-checkpoint kinase 2, occurred following treatment with DEX, EPI and NE. In addition, a cycloheximide chase assay was performed to explore the protein stability under treatment with stress hormones. Compared with vehicle-treated cells, Wip1 exhibited increased protein stability in stress hormone-treated HepG2 cells. Eventually, the depletion of Wip1 using small interfering RNA verified the role of Wip1 in the modulation of stress hormone-induced DNA damage. These findings suggest that cancerous cells likely adapt to stress hormone-induced DNA damage via Wip1 upregulation. The present study provides an insight into the underlying mechanism that links chronic psychological stress with tumor growth and progression.

Chronic stress promotes tumor immune evasion via the suppression of MHC-I expression and the upregulation of PD-L1.

Chronic stress induces cancer initiation and progression via regulation of diverse cancer risk factors including immune evasion. Our previous research demonstrated that ß-adrenergic blockade with propranolol almost completely reversed the accelerated tumor growth induced by chronic restraint stress, but the underlying mechanism of immune escape remains largely unknown. In the present study, a chronic restraint stress paradigm was applied to the H22 hepatocellular carcinoma (HCC) bearing mice to mimic the psychological stress. We observed that chronic restraint stress significantly promoted HCC growth and tumor escape from T cell surveillance. Chronic restraint stress reduced intratumor MHC-I expression and enhanced PD-L1 expression, whereas propranolol rectified the changes of MHC-I and PD-L1. Under chronic stress, the activated MAPK pathway suppressed MHC-I production by inactivating STAT1/IRF1 signaling pathway, and promoted PD-L1 translation by elevating eIF2α phosphorylation. These findings support the crucial role of ß-adrenergic signaling cascade in the tumor escape from T cell surveillance under chronic restraint stress.