Apoptosis induction with three nucleoside analogs on freshly isolated B‐chronic lymphocytic leukemia cells

Abstract

The cytotoxic effects and the induction of programmed cell death (apoptosis) by Fludarabine (FLU), 2-chlorodeoxyadenosine (2-CdA), and deoxycoformycin (DCF) with/without alpha-interferon (alpha-IFN) were evaluated in vitro against freshly isolated B-chronic lymphocytic leukemia (B-CLL) cells. Cytotoxicity was evaluated according to the soluble tetrazolium/formazan assay. Regarding the cytotoxicity, FLU, 2-CdA, and DCF showed a mean antitumor activity of 45% +/- 3.39 (mean +/- S.D.), 55% +/- 4.72, and 20% +/- 3.16, respectively. alpha-IFN alone showed a mean cytotoxic activity of 10% +/- 2.72. The cytotoxicity of these purine analogues in combination with alpha-IFN was 52% +/- 2.97, 75% +/- 3.41, and 26% +/- 7.09, respectively. We observed a statistically significant increase of cytotoxicity compared to controls in FLU alone (P < 0.05), 2-CdA (P < 0.05), and their combination with alpha-IFN (P < 0.05). Apoptosis was evaluated by electrophoresis gel of DNA oligonucleosomal fragments and by a cytofluorimetric method. Only FLU and 2-CdA activated the apoptosis and DCF showed a minor apoptotic pathway amount. These apoptosis data were confirmed by both gel electrophoresis of DNA and by propidium iodide cytofluorimetric method. FLU and 2-CdA show activity in B-CLL cells by direct cytotoxic action and the induction of cell death by apoptosis; in the future, it would be interesting to utilize these in vitro assays in monitoring chemosensitivity and predicting response for the clinical use.

Fludarabine ability to down‐regulate Bcl‐2 gene product in CD5+ leukaemic B cells: in vitro/in vivo correlations

“…This occurs both spontaneously (Collins et al, 1989), suggesting that the culture systems lack a cytokine that in vivo ensures survival (Mainou-Fowler et al, 1996), or upon exposure to glucocorticoid hormones (McConkey et al, 1991) or drugs used clinically such as fludarabine (9-b-D-arabinofuranosyl-2-fluoradenine, F-ara-A), a purine nucleoside analogue resistant to adenosine deaminase Zinzani et al, 1994;McConkey et al, 1996). F-ara-A is of great interest because of its strong therapeutic activity in low-grade lymphoid malignancies (Keating et al, 1989).…”

“…F-ara-A is of great interest because of its strong therapeutic activity in low-grade lymphoid malignancies (Keating et al, 1989). Though F-ara-A is a potent inducer of apoptosis in CLL cell Zinzani et al, 1994;McConkey et al, 1996), the precise molecular mechanism through which it exerts this effect has not yet been fully established (Robertson et al, 1992;Miyashita & Reed, 1992Menzel et al, 1996). Recently, it has been reported that apoptosis sensitivity in CLL cells is determined by endogenous endonuclease content and by the relative expression of Bcl-2 and Bax (McConkey et al, 1996;Petersen et al, 1996;Thomas et al, 1996).…”

Equilibrative nucleoside transporter-2 (hENT2) protein expression correlates with ex vivo sensitivity to fludarabine in chronic lymphocytic leukemia (CLL) cells

“…3 Several in vitro studies indicate that in CLL cells fludarabine induces apoptosis, suggesting that programmed cell death is the mechanism of their therapeutic action. [4][5][6][7][8][9] As CLL cells are predominantly quiescent cells, the proapoptotic activity of fludarabine could be due to inhibition of RNA synthesis or alteration of DNA repair. Both p53-dependent and -independent mechanisms have been described.…”

Nucleoside transporters in chronic lymphocytic leukaemia

“…18 Experimental evidence indicates that in CLL cells most of these drugs induce apoptosis ex vivo, suggesting that programmed cell death is the mechanism of their therapeutic action. 11,14,[19][20][21][22] Thus, in response to apoptotic signals, cytochrome c is released from mitochondria and binds to the adaptor protein Apaf-1. This results in the activation of caspase-9, which triggers downstream caspases, such as caspase-3.…”