Heterogeneity in TPA-induced differentiation of B-chronic lymphocytic leukemia cells: development of hairy cell or plasmacytoid features are time and dose dependent.

Cells from 11 chronic lymphocytic leukemic (CLL) patients were induced to differentiate with various doses of tetradecanoyl phorbol-13-acetate (TPA) and the degree of induction was followed up to six days by measuring the expression of two surface membrane markers (SmIg and GP-70), Ig secretion, tartrate-resistant acid phosphatase (TRAP), and ultrastructural changes. The results indicate dose and time dependency of the TPA effect and a great heterogeneity in the response to TPA among cells from different CLL patients. Furthermore, the two main TPA-induced features, the "plasmacytoid" or "hairy cell" features depended on the dose and duration of treatment with the phorbolester. The plasmacytoid features were more frequently encountered at low doses (1 ng/ml) of TPA and were evident after short exposures to TPA (1-2 days). The hairy cell features were more obvious after incubation with higher doses of TPA (10-100 ng/ml) or at Day 6 with lower doses of TPA. The differentiation features measured, including cell morphology, surface membrane markers, Ig secretion, and TRAP staining, appeared to be independent of each other suggesting an autonomous pathway of differentiation for some of these features.