Drug-induced apoptosis in chronic lymphocytic leukemia

Abstract

Glucocorticoids and fludarabine are able to induce typical features of apoptosis in CLL lymphocytes. Cysteinyl aspartate specific proteases (caspases) play a key biochemical role in the apoptotic pathway. Caspase activation following cytotoxic stimuli leads to highly specific proteolytic cleavage of functionally important cellular enzymes. One of them is poly ADPribose) polymerase (PARP). To some extent caspase activation seems to be under the control of the Bcl-2 family of interacting proteins. We determined the role of Bcl-2-family proteins Bcl-2 (anti-apoptotic) and Bax (pro-apoptotic), activation of caspase-3 (CPP32/Yama) and activation of PARP in CLL apoptosis. All 21 analyzed CLL samples expressed Bcl-2 and Bax. Four of 13 (31%) samples with a low Bcl-2/Bax ratio exhibited in vitro prednisolone resistance, whereas eight of nine (88%) samples with a high Bcl-2/Bax ratio were in vitro resistant (р0.025). There was no significant correlation between clinical pre-treatment status and Bcl-2/Bax ratio. Caspase-3/CPP32 activity increase was registered after dexamethasone as well as after fludarabine treatment in CLL lymphocytes in vitro. Caspase inhibitor Z-VAD.fmk was only able to partially block dexamethasone-induced and spontaneous apoptosis but not fludarabine-induced apoptosis in CLL lymphocytes. PARP activity decreased after dexamethasone and fludarabine treatment. PARP inhibitor 3-aminobenzamide (3-AB) was able to partially inhibit dexamethasone-induced apoptosis but not fludarabineinduced and spontaneous apoptosis.

Characterization of cell death induced by vinflunine, the most recent Vinca alkaloid in clinical development

“…A higher level of Bcl-2, coupled with an absence of any modification of the expression of the pro-apoptotic factor Bax, was found in vinflunine-resistant P388 cells, associating a high Bcl-2/Bax ratio with vinflunine resistance. These data are consistent with reports of high Bcl-2/Bax ratios being associated with drug resistance, as discussed in a recent review (Fujita and Tsuruo, 2000) although any predictive value of the Bcl-2/Bax ratio in terms of clinical studies remains to be demonstrated (Stoetzer et al, 1999). In addition, P388/VFL resistant cells exhibited a higher relative level of Bfl-1/A1 expression, another Bcl-2 family anti-apoptotic member (Zhang et al, 2000), which appears to play a role in the apoptotic response of tumour cells to chemotherapy, having been shown to inhibit etoposide-induced apoptosis (Wang et al, 1999a).…”

Role of caspases and apoptosis-inducing factor (AIF) in cladribine-induced apoptosis of B cell chronic lymphocytic leukemia

“…Most works have investigated the apoptotic mechanism triggered by F-ara-A and the information concerning 2CdA is more limited. Treatment of sensitive B-CLL cells with F-ara-A induces caspase-3 activation in vitro 3,4 and treatment with the pan-caspase inhibitor Z-VAD-fmk prevented caspase-3 activity but not cell death. 3,5 It is not known whether other caspases are also activated.…”

“…Treatment of sensitive B-CLL cells with F-ara-A induces caspase-3 activation in vitro 3,4 and treatment with the pan-caspase inhibitor Z-VAD-fmk prevented caspase-3 activity but not cell death. 3,5 It is not known whether other caspases are also activated. In a previous work on the mechanism of 2CdA-induced apoptosis in B-CLL cells, 6 the induction of caspase activity upon 2CdA-treatment was established but the precise identity of activated caspases and the necessity of caspases for cell death was not established.…”

Fludarabine-induced apoptosis of B chronic lymphocytic leukemia cells includes early cleavage of p27kip1 by caspases

“…1 Expression of several apoptosis-regulating proteins have been tested in B-CLL, but none of them proved unambiguously correlated to disease progression or drug sensitivity. [2][3][4] p27kip1 is highly expressed in B-CLL and high expression of p27kip1 is an adverse prognostic factor in B-CLL. 5 The cyclindependent kinase inhibitor p27kip1 plays a major role in G0/G1 cell cycle arrest.…”