Comparison of BM stromal cells from CLL patients to normal individuals

Abstract

CLL is one of the most common types of adult leukemia and presents as an abnormal population of B lymphocytes. CLL cells are clonal and characterized phenotypically by expression of B cell markers with co-expression of CD5. In vivo CLL cells display characteristics consistent with a defect in apoptosis and exhibit prolonged survival, however in vitro CLL cells undergo rapid spontaneous apoptosis. These data have led to the current view that survival and proliferation of CLL cells depends on the microenvironment. We therefore compared BM MSCs from CLL (CLL-MSCs) patients to MSCs from normal individuals (N-MSCs) for their ability to support growth of hematopoietic cells in vitro. Culture of cord blood (CB) mononuclear cells and CB CD34+ on CLL-MSCs resulted in equivalent total nucleated cell (TNC) numbers as N-MSCs. There was heterogeneity in support of CD34+ cells on CLL-MSCs with 2 of 3 lines generating 2 fold or higher CD34+ cells compared to N-MSCs. The levels of B cells (CD19+ cells) were similar between the CLL-MSCs and N-MSCs. Increased CFU-GM resulted on CLL-MSCs compared to N-MSCs. We also evaluated the effects of added growth factors (GFs) to the cultures, with both cocktails generating equivalent levels of TNCs but increased CD34. Both cocktails resulted in increased B cells with CLL-MSCs. Experiments were also performed using CD34+ cells purified from CB and cultured on CLL-MSCs and N-MSCs. Equivalent levels of TNCs, CD34+ and CD19+ cells were obtained from CLL-MSCs to N-MSCs. We have also evaluated support of CLL cells from patients, N-MSCs failed to support the proliferation of CLL cells, while CLL-MSCs supported long term growth of CLL cells with one sample maintained for more than 9 months. In conclusion, the data in this study suggest that CLL-MSCs are similar to N-MSCs in their capacity to support hematopoiesis but provide a shift to B cells in the presence of added GFs.