Inhibition of PI3-kinase sensitises HL60 human leukaemia cells to both chemotherapeutic drug- and Fas-induced apoptosis by a JNK independent pathway

Increasing resistance to chemotherapeutic regimes remains a serious problem in the treatment of acute myeloid leukaemia. We have shown that phosphatid ylinositol (PI) 3-kinase inhibition significantly sensitises the AML derive d cell line, HL60 to chemotherapeutic drug- and Fas-induced apoptosis. P13- kinase inhibition significantly potentiates cytotoxic drug-induced c-jun N- terminal kinase (JNK) activation, reported to be a requirement for apoptosi s. However. JNK inhibition does not enhance cell viability following treatm ent with drug and inhibitor. Furthermore, P13-kinase inhibition significant ly increases sensitivity to apoptosis mediated by an exogenous receptor ago nist, again by a JNK independent mechanism. These results suggest that P13- kinase inhibitors could be of significant therapeutic importance, lowering the threshold for apoptosis induced by both chemotherapy and cell-mediated immune response. (C) 2001 Elsevier Science Ltd. All rights reserved.