Activated signaling pathways and apoptotic mechanisms in resveratrol applied chronic myeloid leukemia cells and the involvement of ceramide metabolizing genes on these mechanisms
Resveratrol, an important phytoalexin in many plants, has cytotoxic effects on several cancer cells. Ceramide is a significant sphingolipid which affects many signaling pathways regulating cell senescence, migration, and cell cycle arrest. Intracellular ceramide level is balanced by glucosylceramide synthase (GCS), the converter of ceramide to glucosylceramide, and sphingosine kinase-1 (SK-1) that convert ceramide to sphingosine 1-phosphate (S1P). Ceramide functions as an apoptotic molecule whereas glucosylceramide S1P function as anti-apoptotic. An important cell-permeable analogue of natural ceramides, C8:ceramide, increases intracellular ceramide levels significantly, while 1-phenyl-2-decanoylamino-3-morpholino-1-propanol (PDMP) and SK-1 inhibitor increase accumulation of ceramides by inhibiting GCS and SK-1, respectively. Chronic myelogenous leukemia (CML), a hematological disorder, results from the generation of BCR/ABL oncogene. In this study, we examined the roles of ceramide metabolizing genes in resveratrol-induced apoptosis, and the expression profiles of 84 genes underlying apoptosis, cell cycle control, DNA damage repair, and invasion and metastasis in human K562 CML cells treated with resveratrol. There were synergistic cytotoxic and apoptotic effects of resveratrol with coadministration of C8:ceramide, PDMP and SK-1 inhibitor. We observed significant increases in expression levels of LASS genes, and decreases in expression levels of GCS and SK-1 in K562 cells in response to increasing concentrations of resveratrol. There were also significant increases in the expression levels of SERPINB5, FAS, TNFRSF, MTSS that are related with tumor suppression, and decreases in Myc expression. Our data, in total, showed for the first time that resveratrol might kill CML cells through increasing intracellular generation and accumulation of apoptotic ceramides.