Anticancer effects and antimetastatic mechanisms of novel indirubin derivatives

摘要

In this current study, we are investigating the influence of 6-bromo-indirubin-3’oxime (6BIO) and 7-bromo-indirubin-3’oxime (7BIO) on induction of apoptosis, cell proliferation, and anti-migratory effects in the well characterized pancreatic carcinoma L3.6pl and breast carcinoma Skbr3 tumor cell lines and characterize underlying mechanisms. 6BIO and 7BIO at doses of 10 µM were shown to significantly reduce the proliferation and viability as well as induce apoptosis in both cell lines. In addition, 6BIO, but not 7BIO, significantly reduced the migration of both cell lines, nearly halting them completely in the Skbr3 wound healing assay at sub-apoptotic doses (3 µM). Chemotaxis was dramatically disrupted and tumor cells significantly lost their ability to invade through membranes or MatrigelTM layers in response to chemoattractants. An increase of the phosphorylation site S785 of beta1 integrin is seen upon 6BIO which has been linked to decreased motility of carcinoma cells. Additionally, adhesion of Skbr3 tumor cells to fibronectin was reduced by 6BIO stimulation. The effects of 6BIO can be attributed to its reduction of the T308 phosphorylation site of Akt, most likely through its direct inhibition of PDK1, ultimately causing long term alterations to the actin cytoskeleton. Erk, FAK and Rac1 levels are unaffected, but cycling of these signaling molecules appears to be disrupted upon treatment. Finally 6BIO reduced the metabolic capabilities of Skbr3 spheroids at low doses, caused the dissolution of spheroid structures at higher doses and significantly blocked the migration of Skbr3 spheroids. Taken together, the results of this study strongly suggest that the indirubin derivative 6BIO operates by inhibiting different mechanisms in human tumor cells to exert their potent anti-tumor efficacy.