Changes in clonal expression during the course of acute leukemia: possible subsets in childhood leukemia.

We studied cell surface markers and chromosomes in the leukemia cells of a boy with the initial diagnosis of acute lymphocytic leukemia during 18 months from diagnosis to demise. During this time he received induction therapy, underwent bone marrow transplantation, and relapsed. The leukemia cells expressed three membrane phenotypes during different stages of disease: T-cell at diagnosis; T-cell, B-cell, and monocyte during the induction period; T-cell in the first relapse after bone marrow transplantation; and T-cell and B-cell during the terminal stage. Some cells expressed markers of two cell types, indicating a common origin of these cells. Cytogenetic studies during post-transplantation relapse showed abnormal marker chromosomes that indicated two major sublines. However, there was enough sharing of other aberrant chromosomes to suggest that these two populations presented sublines within the same neoplastic clone. We suggest that these leukemia cells were derived from a pluripotential cell prior to differentiation into cells of the lymphoid and monocytic series. This particular case may represent a subset of acute leukemia and may account for the resistance to conventional therapy.