Bryostatin 1-induced modulation of the acute lymphoblastic leukemia cell line Reh.

We have previously reported that the phorbol ester, 12-O-tetradecanoylphorbol 13-acetate (TPA) induces further differentiation of the human acute lymphoblastic leukemia cell line Reh to a monocytoid B lymphocyte stage. In the present study, we investigated the differentiating capacity of another protein kinase C (PKC) activator, bryostatin 1 (bryo). Reh cells were treated in vitro with TPA, bryo, or interferon-alpha (IFN-alpha) for a period of 5 days during which cells were analyzed for changes in growth patterns, morphology, cytochemistry, and surface phenotype. Bryo caused a dose-dependent growth inhibition of Reh cells. Morphologically, the treated cells expressed monocytoid features with development of filopodia and numerous vacuoles indicating phagocytic activity. Bryo induced similar phenotypic changes to TPA, including induction of CD11c, increased expression of CD22 and down-regulation of CD10 and CD19. Enzymatically, bryo, like TPA, induced tartrate-sensitive acid phosphatase expression but failed to induce periodic acid Schiff (PAS) and nonspecific esterase (NSE). Bryo inhibited the TPA action on NSE and CD10. IFN-alpha showed additive growth inhibitory and phenotypic effects to bryo. Collectively, our findings indicate that bryo is capable of inducing further differentiation of the Reh cells along the B cell lineage similar to those of TPA.