Anticancer activity of globularifolin against human adenoid cystic carcinoma cells is due to ROS-mediated apoptotic cell death and modulation of the JAK/STAT signalling pathway

Purpose: Adenoid cystic carcinoma is a rare and under researched disease. There is hardly any chemotherapy available for it, hence the urgent need to develop novel and efficient chemotherapy. Therefore, we examined the anticancer effects of globularifolin, an acylated iridoid glucoside, against salivary adenoid cystic carcinoma (SACC-83) cell line and normal human salivary gland (HSG) cell line. Methods: Cell counting and colony formation assays were used to determine cell viability. Acridin orange (AO)/ethidium bromide (EB) staining and comet assay were used for the detection of apoptosis. Reactive oxygen species (ROS) determination and cell cycle analysis were performed by flow cytometry. Transwell assay was used to monitor cell migration and Western blot analysis was used to determine protein expression. Results: Globularifolin inhibited the growth of SACC-83 cell line and exhibited an IC50 of 10 mu M. Nonetheless, the cytotoxic effects of globularifolin were comparatively negligible against normal HGS cells with an IC50 of 80 mu M. The investigation of the mechanism of action revealed that the anticancer effects of globularifolin against the SACC-83 cells was due to the induction of apoptotic cell death as indicated by AO/EB staining. Globularifolin treatment also resulted in enhancement of the Box, Caspase 3 and 9 expression and decline of the Bcl-2 expression. Globularifolin also blocked the SACC-83 cells at the GO/G1 phase of the cell cycle. Moreover, cell invasion assay revealed that globularifolin inhibited the migration of the SACC-83 cells concentration-dependently, which was also coupled with the downregulation of metalloproteinase (MMP) 2 and 9. JAK/STAT is an important pathway involved in the proliferation and tumorigenesis of cancer cells and this research found that globularifolin could inhibit this pathway. Conclusion: We conclude that globularifolin may prove essential in the development of systemic therapy for adenoid cystic carcinoma.