RESIDUAL PH-NEGATIVE STEM-CELLS IN CHRONIC MYELOID-LEUKEMIA - SOMETIMES OR ALWAYS

Some patients with Philadelphia (Ph) chromosome-positive chronic myelo id leukemia (CML) may achieve partially or completely Ph-negative hemo poiesis after treatment with high doses of cytotoxic drugs or interfer on-alpha at standard dosage. This observation leads to three important questions: 1) are Ph-negative myeloid cells in such patients strictly normal? 2) can such Ph-negative cells be identified in all newly diag nosed patients or only in a minority? and 3) what is the basis for the proliferative advantage manifested by CML cells and why might it be t emporarily lost as a result of treatment? The mechanisms that might pr event the proliferation of normal cells in an environment of Ph-positi ve cells and the relevance of these questions to the design of a strat egy aimed at obtaining complete remission in the majority of patients are considered. Such a strategy might incorporate auto-grafting with P h-negative stem cells harvested during the recovery phase of high dose chemotherapy.