DEVELOPMENT OF A MODEL FOR EVALUATING THE INTERACTION BETWEEN HUMAN PRE-B ACUTE LYMPHOBLASTIC LEUKEMIC-CELLS AND THE BONE-MARROW STROMAL CELL MICROENVIRONMENT

Clonal expansion of B-cell precursor acute lymphoblastic leukemia (ALL ) is potentially regulated by survival, growth, and death signals tran sduced by the bone marrow (BM) microenvironment. Using a human BM stro mal cell culture that supports the growth of normal human B-cell precu rsors, we established a pre-B ALL cell line designated BLIN-2. BLIN-2 has a clonal rearrangement of the Ig heavy chain locus, a dic(9;20) ch romosomal abnormality, and a bi-allelic deletion of the p16(INK4a) and p19(ARF) genes. The most interesting feature of BLIN-2 is an absolute dependence on adherent human BM stromal cells for sustained survival and growth. BLIN-2 cultured in the absence of BM stromal cells undergo apoptosis, and direct contact with viable BM stromal cells is essenti al for optimal growth, BLIN-2 cells also grow on vascular cell adhesio n molecule-1 (VCAM-1)-negative human skin fibroblasts, making it unlik ely that a very late antigen-4 (VLA-4)/VCAM-1 interaction is required for BLIN-2 growth. Western blot analysis of BLIN-2 cells cultured in t he presence or absence of BM stromal cells demonstrates that contact o f BLIN-2 with BM stromal cells induces hyperphosphorylation of Rb. In contrast, the pre-B ALL cell line BLIN-1, which has a bi-allelic delet ion of p16(INK4a) p19(ARF) but does not require BM stromal cells for g rowth, does not undergo Rb phosphorylation after BM stromal cell conta ct. The BLIN-2 cell line will facilitate identification of ligand/rece ptor interactions at the B-cell precursor/BM stromal cell interface an d may provide new insight into microenvironmental regulation of leukem ic cell survival and growth. (C) 1998 by The American Society of Hemat ology.