Kinetic studies of cells in childhood leukemias.

A review of cell kinetic studies in acute childhood leukemia with a comparison of leukemic transformation of non-Hodgkin's lymphoma is presented in this paper. Leukemic cell populations have a longer cell cycle than their normal cell counterparts. The cell populations are comprised of proliferating and resting fractions and are capable of self-maintaining growth. Growth regulation is determined primarily by the size of the proliferating cell population or growth fraction. The growth fraction can vary as to site of disease, the clinical phase, following chemotherapeutic perturbation, and most importantly is related to the specific tumor cell type. Within a specific type of leukemia there is considerable variability of proliferative activity at time of diagnosis, but this variability bears no relationship to the subsequent clinical course. Those leukemias, such as the E rosette-positive form of lymphocytic leukemia characterized by rapid tumor growth and large tumor bulk, are also associated with tumor cell populations having larger growth fractions than standard lymphocytic leukemia. There is evidence for growth regulation of leukemic cell populations on systemic, regional, and, perhaps most importantly of all, intrinsic cell levels. It is this area of growth regulation for these tumor cell populations which currently needs the greatest research attention.