Xanthohumol, a major prenylated chalcone found in female hop plant, Humulus lupulus, was reported to have various chemopreventive and anti-cancer properties. However, its apoptotic effect on human alveolar adenocarcinoma cell line (A549) of non-small cell lung cancer (NSCLC) was unknown.
Researchers are looking into the potential development of natural compounds for anticancer therapy. Previous studies have postulated the cytotoxic effect of helichrysetin towards different cancer cell lines. In this study, we investigated the cytotoxic effect of helichrysetin, a naturally occurring chalcone on four selected cancer cell lines, A549, MCF-7, Ca Ski, and HT-29, and further elucidated its biochemical and molecular mechanisms in human lung adenocarcinoma, A549. Helichrysetin showed the highest cytotoxic activity against Ca Ski followed by A549. Changes in the nuclear morphology of A549 cells such as chromatin condensation and nuclear fragmentation were observed in cells treated with helichrysetin. Further evidence of apoptosis includes the externalization of phosphatidylserine and the collapse of mitochondrial membrane potential which are both early signs of apoptosis. These signs of apoptosis are related to cell cycle blockade at the S checkpoint which suggests that the alteration of the cell cycle contributes to the induction of apoptosis in A549. These results suggest that helichrysetin has great potentials for development as an anticancer agent.
Dengue is endemic throughout tropical and subtropical regions of the world. Currently, there is no clinically approved therapeutic drug available for this acute viral infection. Although the first dengue vaccine Dengvaxia has been approved for use in certain countries, it is limited to those without a previous dengue infection while the safety and efficacy of the vaccine in those elderly and younger children still need to be identified. Therefore, it is becoming increasingly important to develop therapeutics/drugs to combat dengue virus (DENV) infection. YK51 is a synthetic analogue of 4-Hydroxypandurantin A (a compound found in the crude extract of the rhizomes of Boesenbergia rotunda) that has been extensively studied by our research group. It has been shown to possess outstanding antiviral activity due to its inhibitory activity against NS2B/NS3 DENV2 protease. However, it is not known how YK51 affects the proteome of DENV infected cells. Therefore, we performed a comparative proteomics analysis to identify changes in protein expression in DENV infected HepG2 cells treated with YK51. Classical two-dimensional gel electrophoresis followed by protein identification using tandem mass spectrometry was employed in this study. Thirty proteins were found to be down-regulated with YK51 treatment. In silico analysis predicted that the down-regulation of eight of these proteins may inhibit viral infection. Our results suggested that apart from inhibiting the NS2B/NS3 DENV2 protease, YK51 may also be causing the down-regulation of a number of proteins that may be responsible in, and/or essential to virus infection. However, functional characterization of these proteins will be necessary before we can conclusively determine their roles in DENV infection.
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.