Abstract
There is no evidence that cancer cells including leukemic cells are immortal. It has been clearly indicated that certain cytokines can significantly stimulate leukemic cell proliferation in vitro, and sustain the circuit of autocrine or paracrine stimulation. More interestingly, DNA fragmentation and specific morphologic changes including chromatin condensation and nuclear fragmentation can be demonstrated and programmed cell death (apoptosis) is rapidly induced in the majority of primary leukemic cells, when they are placed in culture, indicating leukemic cells still maintain the suicide program for cell death that can be activated. Leukemic cells require specific factors (surviving factors) to remain viable and removal of these factors results in programmed cell death. Additionally, deregulated expression of genes such as c-myc, bcl-2, and tumor-suppressor gene p53 may suppress programmed cell death of leukemic cells. Reduction of surviving factors to activate the suicide program in leukemic cells, and alteration of sensitivity to cytotoxic drugs by cytokine stimulation may be the new strategy for biologic therapy of acute leukemia.
