It was also shown that IL-6 and other cytokines such as IL-1, IL-2, and IL-4 can suppress induction of apoptosis in normal and leukemic lymphoid cells by various cytotoxic agents (reviewed in refs. 33 and 81). Different hematopoietic cytokines can thus decrease the effectiveness of cancer therapeutic compounds against leukemic cells, and this has implications for cancer development and cancer therapy (33, 81).