Proliferation, differentiation, and cytogenetics of chronic leukemic B lymphocytes cultured with mitomycin-treated normal cells

Lymphocytes from 6 patients with chronic lymphocytic leukemia of the B-cell variety (B-CLL) were cultured with equal numbers of mitomycin-treated mononuclear cells from normal blood. When stimulated with pokeweed mitogen (PWM), phytohemagglutinin (PHA), or the tumor-promoting agent, phorbol tetradecanoyl-acetate (TPA), the CLL cells proliferated actively by day 3 or 4 of culture, and in four cases, differentiated to significant numbers of immunoglobulin-containing cells. Chromosome studies on the proliferating lymphocytes demonstrated a cytogenetically abnormal clone in three patients, including two with a 14q+ marker chromosome and two with a translocation involving the short arm of chromosome 9. One patient had a translocation from 22q to 14q, producing a Philadelphia chromosome as well as the 14q+ marker. The results indicate that the neoplastic lymphocytes of B-CLL may proliferate and differentiate when appropriately stimulated in vitro, and that chromosomally abnormal clones are not uncommon. With several techniques now available for successful short-term culture of B-CLL lymphocytes, there is opportunity for better understanding of the cellular alterations in this disease.