Mutant BRAF induces DNA strand breaks, activates DNA damage response pathway, and up-regulates glucose transporter-1 in nontransformed epithelial cells

Jim Jinn Chyuan Sheu, Bin Guan, Fuu Jen Tsai, Erin Yi Ting Hsiao, Chih Mei Chen, Raquel Seruca, Tian Li Wang, Ie Ming Shih

Research output: Contribution to journalArticle

Abstract

Although the oncogenic functions of activating BRAF mutations have been clearly demonstrated in human cancer, their roles in nontransformed epithelial cells remain largely unclear. Investigating the cellular response to the expression of mutant BRAF in nontransformed epithelial cells is fundamental to the understanding of the roles of BRAF in cancer pathogenesis. In this study, we used two nontransformed cyst108 and RK3E epithelial cell lines as models in which to compare the phenotypes of cells expressing BRAF WT and BRAF V600E. We found that transfection of the BRAF V600E, but not the BRAF WT, expression vector suppressed cellular proliferation and induced apoptosis in both cell types. BRAF V600E generated reactive oxygen species, induced DNA double-strand breaks, and caused subsequent DNA damage response as evidenced by an increased number of pCHK2 and γH2AX nuclear foci as well as the up-regulation of pCHK2, p53, and p21. Because BRAF and KRAS (alias Ki-ras) mutations have been correlated with GLUT1 up-regulation, which encodes glucose transporter-1, we demonstrated here that expression of BRAF V600E, but not BRAF WT, was sufficient to up-regulate GLUT1. Taken together, our findings provide new insights into mutant BRAF-induced oncogenic stress that is manifested by DNA damage and growth arrest by activating the pCHK2-p53-p21 pathway in nontransformed cells, while it also confers tumor-promoting phenotypes such as the up-regulation of GLUT1 that contributes to enhanced glucose metabolism that characterizes tumor cells.

Original languageEnglish (US)
Pages (from-to)1179-1188
Number of pages10
JournalAmerican Journal of Pathology
Volume180
Issue number3
DOIs
StatePublished - Mar 1 2012

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ASJC Scopus subject areas

  • Pathology and Forensic Medicine

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