Downregulating RRM2B expression to increase radiation sensitivity of breast cancer cells

Abstract

Objective To identify genes that confer radiation sensitivity in breast cancer cells using transcriptome sequencing technology, and investigate effects of their expression on radiation sensitivity of breast cancer cells. Methods Differential expression analysis was performed using transcriptome sequencing to compare post-radiation breast cancer cells with normal breast cancer cells. Genes associated with DNA damage and repair pathways were selected and analyzed from the differentially expressed genes. The TCGA-BRCA database was used to analyze the expression of RRM2B in breast cancer tissues and its correlation with prognosis. Stable knockdown of RRM2B was achieved in ZR-75-1 and MCF-7 cells, and the expression of RRM2B was confirmed by Western blotting and RT-qPCR. The effect of RRM2B knockdown on the expression of γ-H2AX, a marker protein for DNA damage in radiation cells, was assessed using Western blotting and immunofluorescence assay. The effects of RRM2B knockdown on cell proliferation and apoptosis in radiation cells were evaluated through colony formation, CCK-8 assays, Hoechst/PI staining and flow cytometry. Results Radiation exposure upregulated the expression of the RRM2B in cultured breast cancer cells. Analysis of the TCGA-BRCA database revealed a negative correlation between RRM2B expression and overall survival of breast cancer patients (P < 0.05). Following knockdown of RRM2B, the expression of γ-H2AX in radiation-induced breast cancer cells was significantly increased (P < 0.05), while cell proliferation capacity was decreased significantly (P < 0.05), and cell apoptosis was markedly increased (P < 0.05). Conclusion The DNA repair factor RRM2B is upregulated in response to radiation. Downregulation of RRM2B expression enhances the sensitivity of breast cancer cells to radiation by increasing radiation-induced DNA damage, inhibiting cell proliferation and promoting apoptosis.

Keywords

• transcriptome sequencing
• breast cancer
• radiation
• rrm2b