Our previous findings demonstrated that
Helichrysetin possessed promising anti-
cancer activity. It was able to induce apoptosis in the A549 cell line. However, its mechanism of action is unknown. The present study aimed to unravel possible underlying molecular mechanisms of
helichrysetin-induced apoptosis in A549 (human lung
carcinoma) cells using comparative quantitative proteomics (iTRAQ labeled), followed by an exhaustive bioinformatics analysis. Our results suggested that DNA damage response (DDR) and cell cycle arrest were responsible for
lung cancer cell death with
helichrysetin treatment. Among
proteins that changed in abundance were Nrf2 and HMOX1. They are oxidative stress-related
proteins and were increased in abundance. BRAT1 was also increased in abundance, suggesting an increase in DNA damage repair, indicating the occurrence of DNA damage due to oxidative stress. However, several essential DDR downstream
proteins such as p-ATM, BRCA1, FANCD2, and Rb1 that would further increase DNA damage were found to be dramatically decreased in relative abundance. Cell cycle-related
proteins, p53, p21, and
cyclin D1, were increased while
cyclin A,
cyclin E, and cdk2 were decreased. This is predicted to facilitate S-phase arrest. Furthermore, excessive DNA damage and prolonged arrest would in turn result in the induction of mitochondrial-mediated apoptosis. Based on these observations, we postulate that the effects of
helichrysetin were in part via the suppression of DNA damage response which led to DNA damage and prolonged cell cycle arrest. Subsequently, this event initiated mitochondrial-mediated apoptosis in A549
lung cancer cells.