Cytochalasin B is a potent mitogen for chronic lymphocytic leukemia cells in vitro.

Abstract

A B S T R A C T It is widely accepted that the neoplastic B cells from patients with chronic lymphocytic leukemia (CLL) respond poorly to common mitogens. The fungal metabolite cytochalasin B (0.5 ,ug/ml) is a weak mitogen for normal lymphocytes. However, when peripheral blood lymphocytes from 19 patients with CLL of B cell origin (B-CLL) were cultured with 0.5 Mg cytochalasin B/ml, significant new DNA synthesis (['4C]thymidine incorporation) occurred in 18. Stimulation indices with cytochalasin B varied widely (range = 1.9-28.2, mean ± SD = 10.6 ± 7.5; Acpm range = 1,157-153,818; n = 26) but in 11 cases exceeded those seen with concanavalin A (Con A), phytohemagglutinin, or pokeweed mitogen. In all 11, the mitogenic response to cytochalasin B exceeded that to pokeweed mitogen, which is believed to be a T celldependent B cell mitogen. In three cases, the responses to cytochalasin B were 8.6, 3.5, and 2.3 times greater than those to Con A. As with other mitogens, the DNA synthetic response to cytochalasin B was time and dose dependent. Peak thymidine incorporation occurred at 72-88 h and declined thereafter. Significant mitogenic effects were observed with 0.1-5 pig cytochalasin B/ml with a peak at 0.5-2 ,ug/ml. Stimulated DNA synthesis was abolished by 1 mM hydroxyurea. Cells from two patients with B-CLL were separated by rosetting with sheep erythrocytes (E). Depletion of E-rosette-positive cells from the CLL cell population abolished the response to Con A but did not affect the response to

Morphological modifications of apoptosis in HL-60 cells: effects of homocysteine and cytochalasins on apoptosis initiated by 3-deazaadenosine

“…In contrast to other cytochalasins, cytochalasin B (CB) also affects glucose transport at site I as defined by Rampal et al [45;also 7]. In addition, several non motility related effects of CB are demonstrated including mitogen stimulation [33] and elevation of intracellular calcium levels [20,52]. CB and cytochalsin E (CE) have been shown to prevent formation of APB without affecting DNA degradation in HL-60 cells undergoing apoptosis [11].…”