The construction of drug-resistant cancer cell lines by CRISPR/Cas9 system for drug screening.

Cancer therapy is often hampered by the rapid emergence of drug resistance. Drug-resistant cellular models are essential for understanding the drug resistance and developing new therapeutics. The low efficiency and long time required in creating these models are major obstacles hindering drug resistance research and drug screening. Herein, we report an approach that can accelerate (shortening the time from years to 3 weeks) the establishment of cancer cell line-based, inheritable drug resistance models by specific knockout of MED12 gene using CRISPR/Cas9 system. The resultant MED12 A375 (melanoma) cell line was resistant to inhibitors of B-Raf proto-oncogene, serine/threonine kinase (BRAF), whereas the resultant MED12 PC9 (non-small cell lung cancer) cell line was resistant to inhibitors of epidermal growth factor receptor (EGFR). Evaluation of anti-cancer drugs and their combinations shows that certain combinations of BRAF inhibitors and TGF-β receptor (TGF- βR) inhibitors are active in suppressing the growth of MED12 A375 cells, and a few combinations of EGFR inhibitors and TGF-βR inhibitors were active in suppressing the growth of MED12 PC9 cells. The drug-resistant models will be useful in screening novel drugs and drug combinations for multi-drug-resistant cancer therapy.