Upregulation and activation of p53 by erastin‑induced reactive oxygen species contribute to cytotoxic and cytostatic effects in A549 lung cancer cells

The tumour‑suppressor protein p53 is a key regulator of multiple cellular processes and exerts its tumour‑suppressor function by inducing apoptotic cell death. However, emerging evidence indicates that p53 is also involved in inducing ferroptosis, which is a unique iron‑dependent form of non‑apoptotic cell death triggered by the RAS‑selective lethal small molecule erastin. Previous studies have shown that erastin exposure induces increased ROS accumulation and oxidative stress. In the present study, we incubated A549 cells with erastin and detected ROS accumulation. Semi‑quantitative western blotting was performed to analyse the effect of the induced ROS on p53 activity. To determine how ROS activate p53, NAC, an ROS scavenger, and KU‑55933, an ATM kinase inhibitor, were employed to co‑incubate with erastin, followed by western blot analysis. Either p53 or SLC7A11 siRNA was introduced into A549 cells to silence the target‑gene expression, followed by ROS detection to illustrate the regulatory role of ROS‑activated p53 on its target gene SLC7A11. Annexin V‑FITC/PI staining was performed to detect the induction of apoptotic cell death by erastin exposure. To further assess the effects of erastin treatment on cellular proliferation, EdU staining and cell cycle flow cytometric analysis were performed. Erastin exposure upregulated and activated p53 and thus, transcriptionally activated its downstream target genes, including p21 and Bax, in lung cancer A549 cells dependent on erastin‑induced ROS. Subsequently, activated p53 by erastin treatment suppressed SLC7A11 and induced ROS accumulation, indicating the potential feedback loop between p53 and erastin‑induced ROS. By employing the caspase inhibitor Z‑VAD‑FMK, it was revealed that erastin‑induced p53 contributed to both ferroptotic and apoptotic cell death and inhibited cell proliferation via arresting the cell cycle at G1 phase. Collectively, these results indicated that p53 may contribute to the cytotoxic and cytostatic effects associated with establishing a feedback loop with ROS induced by erastin.