In vitro hematopoiesis in patients with malignant lymphoma during active disease and at complete clinical remission after chemotherapy.

Malignant lymphomas are neoplastic diseases of lymphoid cells, which usually originate in the lymph nodes. During the last two decades, significant progress has been made in the characterization of chromosomal and molecular alterations in these malignancies. To date, however, the composition and function of the hematopoietic system in this group of hematological disorders is still not fully understood. In the present study, we have determined the progenitor cell content in 10 patients with diffuse large-cell lymphoma (DLCL) and characterized the proliferation of these cells in long-term marrow cultures. We have also addressed some issues regarding the composition and function of the hematopoietic microenvironment in this malignancy. All the patients included in this study showed normal hematological parameters in peripheral blood, both before and after chemotherapy, however, significant hematopoietic alterations were consistently observed. As compared to normal subjects, lymphoma patients showed a 35% reduction in progenitor cell numbers, including myeloid, erythroid and multipotent progenitors. The in vitro proliferation of these cells was also deficient, since their levels in long-term marrow cultures were significantly lower than those observed in normal bone marrow cultures. Fibroblastic progenitors were reduced by >50% and this correlated with a deficient adherent cell layer development in culture. A reduction was also seen in the levels in culture supernatant of the stimulatory cytokines Stem Cell Factor and Interleukin-6. Interestingly, all the hematopoietic alterations mentioned above were still present in patients at complete clinical remission after chemotherapy. Thus, in the present study we have demonstrated significant in vitro deficiencies in the composition and function of the hematopoietic system in patients with diffuse large-cell lymphoma, both during active disease and at the time of complete clinical remission.