Development of a Bioassay for Putative Human

We attempted to define the conditions that promote growth of putative lymphoma stem cell colonies in vitro in a soft agar system. Growth was promoted by feeder layers containing medium conditioned by adherent spleen cells of mineral oil-primed BALB/c mice or by cells from a human B lymphocyte cell line (RPMI-1788). There were 65 patients with all histologic types of non-Hodgkin lymphoma studied. Lymphoid colony growth was obtained in 1 1 (61%) of 18 bone marrows and in 3 (50%) of 6 lymph nodes histologically involved by lymphocytic lymphoma Conversely, colony growth was observed In only a single instance from 49 bone marrows without overt lymphoma and was not observed in cultures of normal lymph nodes (4), spleens (2), bone marrows (10), or peripheral blood (6). In a group of 1 2 patients whose bone marrows were studied serially before, during, and after chemotherapy, positive cultures correlated well with bone marrow involvement by lymphoma and dm1cal status. In positive cultures, colonies appeared withIn 4 days of plating and reached peak size (nearly 1000 cells per colony) in 7-10 days. Plating efficiency ranged from 0.001% to 01%. Morphologic, histochemical, and immunologic studies of cells from the colonies identIfied them as lymphoid. This assay system should permit further identification of the characteristics of lymphomas that grow in vitro and may prove amenable for evaluating effects of anticancer drugs on the survival of human lymphoma colony-forming cells.