[Arsenic trioxide restores ERα expression in ERα-negative human breast cancer cells and its treatment efficacy in combination with tamoxifen in xenografts in nude mice].

Objective: To study the demethylation effect of arsenic trioxide (As2O3) on ERα-negative human breast cancer MDA-MB-435s cells and its possible mechanisms, and to observe its treatment efficacy in combination with tamoxifen (TAM) after ERα re-expression.

Methods: MTT assay was used to examine the inhibitory effect of As2O3 treatment alone or in combination with TAM on cell proliferation. A nude mouse xenograft model was used to further examine the treatment efficacy in vivo.