Antitumor effects of helenalin in doxorubicin-resistant leukemia cells are mediated via mitochondrial mediated apoptosis, loss of mitochondrial membrane potential, inhibition of cell migration and invasion and downregulation of PI3-kinase/AKT/m-TOR signalling pathway.

Purpose: The main purpose of the current study was to investigate the antitumor effects of helenalin - a plant derived sesquiterpene lactone, against doxorubicin-resistant acute myeloid leukemia HL60 cells, along with evaluating its effects on apoptosis induction, mitochondrial membrane potential (MMP), cell migration and inhibition and PI3K/AKT/M-TOR signalling pathway.

Methods: Antiproliferative effects were evaluated with CCK8 cell viability assay and colony formation assay. Cell apoptotic effects were studied by (acridine orange) AO/ethidium bromide (EB) staining assay. To further estimate the extent of apoptosis, flow cytometry using annexin V assay was used. Effects on MMP were estimated by flow cytometry, while transwell migration assay was used to study the effects on cell migration and invasion. Protein expression was estimated by western blot method.

Results: The results showed that helenalin inhibits the growth of the HL60 cells significantly and exhibited an IC50 of 23.5 µM. In addition, it was observed that the anticancer effects of helenalin are due to induction of mitochondrial-mediated apoptosis which was also associated with enhancement of the expression of Bax and decrease in the expression of Bcl-2. Helenalin also caused loss of MMP in the doxorubicin-resistant HL-60 cells and also inhibited their migratory and invasive properties via modulation of the PI3K/AKT/M-TOR signalling pathway.

Conclusions: In conclusion, the present study reveals that helenalin sesquiterpene lactone exhibits significant antitumor activity in doxorubicin-resistant acute myeloid leukemia HL60 cells by targeting some key pathways and as such this molecule could prove to be a potential drug candidate for future investigations.