In vitro culture of common acute lymphoblastic leukemia blasts: effects of interleukin-3, interleukin-7, and accessory cells

We investigated the effects of interleukin-3 (IL-3), IL-7, IL-1, and IL- 6, of irradiated bone marrow-derived fibroblasts (Fb) and of in vitro matured peripheral blood macrophages (M phi), on the survival, proliferation, and maturation of purified blasts from nine common acute lymphoblastic leukemias (cALLs) in 7-day suspension culture. Exposure to IL-3, IL-7, IL-1, and IL-6 resulted in a mean 2.8-, 1.5-, 1.4-, and 1.6-fold stimulation of 3H-thymidine (3H-TdR) incorporation, respectively. Cocultures of cALL blasts with irradiated M phi, either allowing direct cell-cell contact or preventing it by membrane filters, or with irradiated Fb, resulted in a mean 31.7-, 4.1-, and 11.2-fold increase of 3H-TdR incorporation, respectively. Southern blot analysis of immunoglobulin and T-cell receptor (TCR) gene rearrangements before and after culture indicated exclusive proliferation of the leukemic clone in three of eight samples, whereas additional generation of nonleukemic cells was found in five samples. Polyclonal growth pattern corresponded to the detection of heterogeneous cell populations using FACS analysis. Survival of cALL blasts as defined by the detection of cells coexpressing both CD10 and CD19 after culture was supported by accessory cells in five of eight samples. No evidence of induced lymphoid maturation was found under any culture condition. Our data demonstrate supportive effects of stromal cells on cALL growth, which cannot be replaced by IL-3 or IL-7.