Changes in DNA damage repair gene expression and cell cycle gene expression do not explain radioresistance in tamoxifen-resistant breast cancer.

Changes in DNA damage repair gene expression and cell cycle gene expression do not explain radioresistance in tamoxifen-resistant breast cancer. Oncol Res. 2019 Apr 18;: Authors: Post AEM, Bussink J, Sweep FCGJ, Span PN Abstract Tamoxifen-induced radioresistance, reported in vitro, might pose a problem for patients who receive neo-adjuvant tamoxifen treatment and subsequently receive radiotherapy after surgery. Previous studies suggested that DNA damage repair or cell cycle genes are involved, and could therefore be targeted to preclude the occurrence of cross-resistance. We aimed to characterize the observed cross resistance by investigating gene expression of DNA damage repair genes and cell cycle genes in estrogen receptor-positive MCF-7 breast cancer cells that were cultured to tamoxifen resistance. RNA sequencing was performed and expression of genes characteristic for several DNA damage repair pathways was investigated; as well as expression of genes involved in different phases of the cell cycle. The association of differentially expressed genes with outcome after radiotherapy was assessed in silico in a large breast cancer cohort. None of the DNA damage repair pathways showed differential gene expression in tamoxifen resistant cells compared to wild-type cells. Two DNA damage repair genes were more than 2 times upregulated: NEIL1 and EME2; and three DNA damage repair genes were more than 2 times downregulated: PCNA, BRIP1, an...
Source: Oncology Research - Category: Cancer & Oncology Tags: Oncol Res Source Type: research