Breast cancer susceptibility gene 1 regulates oxidative damage via nuclear factor erythroid 2-related factor 2 in oral cancer cells

Abstract

ObjectiveTo determine whether the breast cancer susceptibility gene 1 (BRCA1) regulates oxidative damage in oral cancer cells by interacting with nuclear factor erythroid 2-like 2 (NRF2). DesignThe BRCA1 gene was silenced in CAL-27 and DOK cells using specific shRNA, and NRF2 was activated with sulforaphane. The expression levels of BRCA1, NRF2 and its target genes were assessed by quantitative real-time polymerase chain reaction and western blotting. Cell counting kit-8 assay was used to detect cell proliferation, apoptosis was detected by flow cytometry, and 8-OXo-2’-deoxyguanosine level was measured by enzyme-linked immunosorbent assay. The expression of BRCA1 and NRF2 in patients with oral leukoplakia and oral squamous cell carcinoma were evaluated by immunohistochemistry. ResultsBRCA1 knockdown downregulated NRF2 and its target genes, increased proliferation rates, reduced apoptosis, and increased 8-OXo-2’-deoxyguanosine levels compared to the control. Activation of NRF2 by sulforaphane significantly upregulated NRF2 levels in the BRCA1-depleted cells, and restored proliferation, apoptosis and 8-OXo-2’-deoxyguanosine level in a dose-dependent manner. Compared with patients with leukoplakia, BRCA1 and NRF2 expression were increased in patients with oral squamous cell carcinoma. ConclusionsBRCA1 depletion increases oxidative damage and promotes the malignant phenotype, which may eventually promote oral carcinogenesis. The NRF2-activator sulforaphane is a potential chemo-preventive agent for oral cancer.