Title: Utilization of Rad51C promoter for transcriptional targeting of cancer cells
Abstract: // Yan Cao 1,* , Yan Xu 1,* , Lei Zhang 1,* , Zhen Li 1 , Ying Jiang 1 , Xiao Tian 2 , Andrei Seluanov 2 , Vera Gorbunova 2 , and Zhiyong Mao 1 1. School of Life Sciences and Technology, Tongji University, Shanghai, China 2. Department of Biology, University of Rochester, Rochester, NY, USA * These authors contributed equally to the work Correspondence: Vera Gorbunova, email: // Zhiyong Mao, email: // Keywords : Rad51C promoter, Rad51 paralogs, cancer therapy, DNA double strand break repair, homologous recombination Received : January 12, 2014 Accepted : February 18, 2014 Published : February 19, 2014 Abstract Cancer therapy that specifically targets malignant cells with minimal or no toxicity to normal tissue has been a long-standing goal of cancer research. Rad51 expression is elevated in a wide range of cancers and Rad51 promoter has been used to transcriptionally target tumor cells, however, a large size of Rad51 promoter limits its application for gene therapy. To identify novel tumor-specific promoters, we examined expression levels of Rad51 paralogs, Rad51B, Rad51C, and Rad51D as well as Rad52 in a panel of normal and tumor cell lines. We found that Rad51C is significantly overexpressed in cancer cells. The expression was up-regulated by approximately 6-fold at the mRNA level and 9-fold at the protein level. Interestingly, the 2064 bp long Rad51C promoter fragment was approximately 300-fold higher in cancer cells than in normal cells. A construct containing Rad51C promoter driving diphtheria toxin A efficiently killed several types of cancer cells with very mild effect to normal cells. These results underscore the potential of targeting the homologous recombination pathway in cancer cells and provide a proof of principle that the Rad51C promoter fragment can be used to transcriptionally target cancer cells.