The cellular and molecular environment in leukemia.

Identification of normal viability-, growth-, and differentiation-inducing cytokines, the cells that produce them, and how cytokines interact in normal development, has made it possible to identify the cellular and molecular basis of normal development and changes in the developmental program that result in leukemia. When normal cells have been changed into leukemic cells, the malignant phenotype can again be suppressed in various ways. Results on the molecular control of growth, differentiation, and apoptosis in normal myeloid hematopoietic cells, changes in the normal developmental program in myeloid leukemia, and the suppression of malignancy in myeloid leukemia, have shown that (A) malignancy can be suppressed either with or without genetic changes in the tumor cells, (B) suppression of malignancy by inducing differentiation does not have to restore all the normal controls, and (C) genetic abnormalities which give rise to malignancy can be bypassed and their effects nullified by inducing differentiation and apoptosis which stop cells from multiplying.