GPX4 overexpressed non-small cell lung cancer cells are sensitive to RSL3-induced ferroptosis.

Ferroptosis can be induced by inhibiting antioxidant enzymes GPX4 or system Xc-, increased intracellular iron concentrations, and lipid peroxidation. Recently, it has been suggested that ferroptosis can be an effective way to induce cancer cell death, although the specific relevance and mechanism of ferroptosis have not been fully elucidated. Here, we investigated the anticancer effects of ferroptosis inducers erastin and RSL3 on non-small cell lung cancer (NSCLC) cells. RSL3 induced cell death more effectively in NSCLC cells than erastin, with limited cytotoxicity in BEAS-2B normal bronchial epithelial cells. The sensitivity of NSCLC cells to RSL3 induced death was dependent on GPX4 expression levels; the effect of RSL3 was reversed by ferrostatin-1 (a ferroptosis inhibitor) but not by Z-VAD-FMK, chloroquine, bafilomycin A1, or necrostatin-1. RSL3 induced ferroptosis by promoting lipid peroxidation, elevating intracellular LIP concentration and ROS level, and blocking GSH-to-GSSH conversion through the inhibition of GPX4 and induction of Nrf2/HO1. Furthermore, RSL3 induced autophagosomes but disrupted the formation of autolysosomes with lysosomal membrane destabilization. GPX4 knockdown had a similar effect on ferroptosis phenotypes as RSL3. Taken together, RSL3-induced ferroptosis depends on the regulation of GPX4-Nrf2/HO1 in NSCLC cells. These results may be useful in predicting the ferroptosis response in NSCLC as well as drug resistant cancer cells.

Nrf2 regulates cell motility through RhoA-ROCK1 signalling in non-small-cell lung cancer cells.

Nuclear factor-erythroid 2-related factor 2 (Nrf2) is a key transcriptional regulator of several antioxidant and anti-inflammatory enzymes. It binds to its endogenous inhibitor Kelch-like ECH-associated protein 1 (Keap1) in the cytoplasm under normal conditions. Various endogenous or environmental oxidative stresses can disrupt the Nrf2/Keap1 complex, allowing Nrf2 to translocate into the nucleus, where it induces the transcription of various cytoprotective enzymes by binding to antioxidant responsive elements. These enzymes have been reported to play a role in regulating tumour growth, angiogenesis, and chemoprevention. Invasion and migration are the most harmful aspects of cancer; they directly impacts the patients' survival. Although the roles of Keap1/Nrf2 and their downstream genes in various cancers have been widely documented, their role in regulating cell motility still remains unclear, particularly in cancer cells. We observed that Nrf2 suppression following treatment with brusatol in non-small-cell lung cancer (NSCLC) cells with either exogenously introduced Keap1 or siNrf2 resulted in the inhibition of cell migration and invasion, with shrinking cell morphology due to decreased focal adhesions via inhibition of the RhoA-ROCK1 pathway. Nrf2 overexpression showed opposite results. Thus, the Nrf2/Keap1 pathway may affect cell motility by dysregulating the RhoA-ROCK1 signalling pathway in NSCLC.