CONICET | Buscador de Institutos y Recursos Humanos

Calcitriol has been evaluated as anticancer agent in many cancer cells. This effect may be increased with glutathione-depleting drugs such as L-Buthionine-S,R-Sulfoximine (BSO), which may be applied as an alternative to avoid bone complications associated with breast cancer metastasis. Our aim was to investigate calcitriol and BSO actions, alone or in combination, on breast cancer cells. MCF-7 cells were treated with 100 nM calcitriol, 20 μM BSO or both at different times. Cell growth was evaluated by crystal violet staining. GSH content was measured by spectrophotometry, while reactive oxygen species (ROS) and cell cycle by flow citometry. Apoptosis was analyzed by phase contrast microscopy and immunocytochemistry and TRPV6 gene expression by qPCR. Results were analyzed using ANOVA and Bonferroni. BSO, calcitriol and the combination reduced MCF-7 proliferation at 96 h. GSH levels were also reduced by BSO, calcitriol or the combination in a time-dependent way. ROS levels were increased in cells treated with calcitriol or calcitriol+BSO (96 h). Calcitriol and the combination augmented the proportion of cells in G1 phase (72 h) and induced DNA fragmentation and changes in Cit c localization (96 h). TRPV6 gene expression resulted 6-fold higher in cells treated with calcitriol and with the combination (96 h). Altogether, these results may indicate that calcitriol and BSO inhibited MCF-7 cell growth altering cell redox state due to GSH reduction and ROS production. Cell arrest in G1 phase may contribute to the reduced cellular growth. DNA fragmentation and Cit c release from the mitochondria suggest apoptotic effects of calcitriol and calcitriol+BSO. Finally, calcitriol and its combination with BSO induced TRPV6 gene expression, which implies a possible role of calcium underlying these effects.

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