Detection and possible significance of a common leukemia-associated antigen, CAMAL, in human myeloid leukemia

Human acute nonlymphoblastic or myelogenous leukemia (ANLL or AML) is a malignant disease of the bone marrow involving hemopoietic (blood-forming) cells of the myeloid lineage. ANLL is a complex neoplastic disease, whose fundamental nature is only partially understood despite intensive research. The disease is complicated by its apparent heterogeneity in terms of the degree of differentiation of hemopoietic stem cell involvement in different patients and the cellular expression of immunologically defined surface markers. The presence of a common antigen in myelogenous leukemia (CAMAL) has been previously identified. This thesis examines the expression of the CAMAL marker in or on bone marrow (BM) and peripheral blood (PB) cells using a monoclonal antibody-based indirect immunoperoxidase slide test. Increased numbers of CAMAL-positive cells were found in or on BM and PB of myeloid leukemia patients (with acute or chronic forms of the disease) compared with those found in normals or most lymphoid malignancies. Results presented herein have demonstrated that fluctuations in CAMAL BM values (% positive cells) correlated with survival time prior to relapse. In a blind study, ANLL patients Whose CAMAL BM values decreased post-chemotherapy had significantly (p < 0.025) longer first remission times (x = 19.2 months) than patients with increasing or static CAMAL BM values (x = 6.8 months). CAMAL BM values were often observed to increase during remission, prior to relapse, suggesting the presence of residual subclinical disease. Addition of excess purified leukemia-derived CAMAL to an in vitro myeloid progenitor cell assay caused profound inhibition of normal CFU-c growth but had no inhibitory effect on CFU-c growth from myeloid leukemia patients in active disease states. Depletion of CAHAL from normal plasma and conditioned media (sources of numerous hemopoietic growth regulatory factors) caused significant inhibition of normal, but not myeloid leukemic, CFU-c growth. These results indicated that myeloid leukemic cells possessed apparent differences in responsiveness to CAMAL-mediated hemopoietic regulation compared to normal cells. Lack of responsiveness to inhibition by leukemia-derived CAMAL may facilitate dominance of the malignant clone over normal cells.Science, Faculty ofMicrobiology and Immunology, Department ofGraduat