Indirubin derivatives inhibit malignant lymphoid cell proliferation

Indirubin-3'-monoxime (IO) is a derivative of indirubin, an active compound of a traditional Chinese medicinal recipe used to treat various inflammatory and malignant diseases. The main in vitro targets of IO (i.e. cyclin dependent kinases, glycogen synthase kinase-3beta, Stat 3 and Aryl hydrocarbon receptor) are regulators of lymphocyte activation. We investigated the interest of IO and its derivative 6-bromo-indirubin-3'oxime (6BIO) for inhibiting the growth of malignant lymphoid cells. IO (1-20 microM) induced cell cycle inhibition and cell death in malignant B- (IM9, Reh6) and T- (Jurkat, CEM-T) lymphoid cell lines depending to cell type, doses, and duration of treatment. IO and 6BIO (10 microM) treatment for 24 and 48 h were compared: 6BIO treatment resulted in a stronger cytotoxicity and more profound inhibition of cell proliferation. Taken together, these results showed that IO and, moreover, its derivative 6BIO may be potent antiproliferative agents in malignant lymphoid cells.