The influence of venetoclax, used alone or in combination with cladribine (2-CdA), on CLL cells apoptosis in vitro: Preliminary results.

BACKGROUND

Venetoclax (VEN), a highly selective BCL-2 inhibitor, is successfully used in the treatment of chronic lymphocytic leukemia (CLL). The purine analogue - cladribine (2-CdA) - is also administered to CLL patients, especially as a part of chemoimmunotherapy.

OBJECTIVES

To compare the effects of the VEN+2-CdA regimen with that of the 2 drugs used alone on the apoptosis of CLL lymphocytes in vitro.

MATERIAL AND

METHODS

Mononuclear cells were collected from 103 previously untreated CLL patients. They were incubated with VEN (40 nM) or/and 2-CdA (16 μM) for 48 h. Cytotoxicity, overall apoptosis, mitochondrial transmembrane potential changes (ΔΨm), and expression of selected apoptosis-involved proteins were measured.

RESULTS

The cytotoxicity, overall apoptosis, caspase-3 or caspase-9 expression, and ΔΨm were significantly higher after VEN+2-CdA addition compared to both drugs used alone, with a very strong synergistic effect observed. The percentage of BCL-2-positive cells decreased after VEN and VEN+2-CdA addition compared to controls. The TP53-expressing cells increased under the influence of all tested regimens. The VEN+2-CdA increased the expression of BIM, BAX and NOXA compared to either controls or VEN or 2-CdA alone. Similar increases in PUMA expression were observed after VEN, 2-CdA and VEN+2-CdA addition. The FAS-associated death-domain protein (FADD) expression was significantly higher after 2-CdA and 2-CdA+VEN addition as compared to control.

CONCLUSIONS

Our results confirm the involvement of both VEN and 2-CdA in the intrinsic apoptotic pathway. They also demonstrate that these agents have a synergistic effect on CLL cells in vitro. Further studies are needed to assess the influence of VEN+2-CdA on the expression of apoptosis-involved genes.