Growth inhibition of follicular small-cleaved-cell lymphoma cells in short-term culture by interleukin-3

Background: The role of interleukin-3 (IL-3) in stimulating the growth of early myeloid progenitor cells is very well established. Therefore, IL-3 has been incorporated into many post-bone-marrow transplantation and intensive chemotherapy programs for the treatment of solid tumors and hematologic malignancies, including lymphomas. However, the effect of IL-3 on normal and malignant lymphocytes has not been well studied. Purpose: The purpose of this study was to evaluate the in vitro effect of IL-3 on the growth of follicular small-cleavedcell lymphoma (FSCCL). Materials and methods: IL-3 receptor expression on the surface of CD19⁺ cells was determined by two-color flow cytometry measuring the receptor-binding of biotinylated IL-3 to CD19⁺ B-cells. Seven cases of FSCCL were compared to six normal controls. Cell proliferation was evaluated by [³H]thymidine incorporation into cells grown in suspension cultures. Results: All seven cases of FSCCL expressed the IL-3 receptor on the surface of CD19⁺ cells, whereas all six cases of CD19⁺ cells isolated from the peripheral blood of normal donors did not express IL-3 receptors. IL-3 had antiproliferative activity against FSCCL as manifested by a decrease in [³H]thymidine incorporation and a decrease in the total number of cells after 72 hours of culture. Conclusion: IL-3 inhibits the growth of FSCCL cells in vitro. Clinical trials to evaluate the in vivo effect of IL-3 in patients with FSCCL are warranted.