Characterization of HR-Killer1 and identification of small molecules for cancer therapy and enhanced gene editing using CRISPR/Cas9-based DNA repair strategies

Inherited diseases arise from mutations in our genes, and similarly genetic mutations underlie the development of a variety of cancers. These mutations arise from DNA damage that is repaired incorrectly in our cells, and ironically radiation or drugs that damage DNA are the most common form of cancer therapy. Thus, if you can manipulate DNA repair you can also enhance DNA damage in cancer cells as a means of therapy. In 2013, scientists discovered that you could efficiently edit DNA in human cells using a system from bacteria called CRISPR (clustered regularly-interspaced short palindromic repeats). CRISPR represents a primitive immune system found in many species of bacteria, which provides them with the ability to "fight" viruses by cutting the viral DNA into pieces. This cutting activity is provided by the CRISPR-associated protein 9 (Cas9), which uses small guide RNAs (gRNAs) to pair with and target DNA molecules for cleavage. CRISPR/Cas9 can be applied to genome editing by using the DNA cutting activity to repair damaged genes, or to insert new genes; and for this advance, CRISPR/Cas9 was named "Breakthrough of the Year" by Science Magazine in 2015. Using a novel assay based on CRISPR/Cas9 gene editing we have identified a new small molecule inhibitor of DNA repair called HRK1, which we will characterize as a potential new cancer therapy. In addition, we have partnered with the Centre for Drug Research and Development (Vancouver B.C.) to screen for both enhancers and inhibitors of CRISPR/Cas9-mediated gene editing. Enhancers of CRISPR/Cas9 can be used to improve the efficiency of gene editing; whereas inhibitors will likely block DNA repair, and thus can be used to sensitize cancers to radiation and chemotherapy. Ultimately, the compounds we identify and characterize will provide new therapeutics for cancer and agents to enhance the efficiency of gene therapy.