Establishment of Cas9 stably expressed human hepatocellular carcinoma and cholangiocarcinoma cell lines

Abstract

Objective: To facilitate using the CRISPR/Cas9 gene editing system in human liver and gallbladder cancer cells, we established Cas9 stably expressed human liver and gallbladder cancer cell lines, and validated the gene editing activity of Cas9. Methods: Human liver cancer cell lines (Huh7, PLC/PRF/5, HepG2, Hep3b, SK-HEP-1 and Li-7), human cholangiocarcinoma cells (RBE) and human gallbladder cancer cells (GBC-SD) were infected with 3 Cas9-expressing lentivirus vectors (pLv-EF1α-Cas9-Flag-Neo, pLv-EF1α-Cas9-Flag-Puro, Cas9m1.1), respectively, and Cas9 stably expressed colonies were screened and selected. We extracted the genomic DNA and protein, validated the stable expression of Cas9 by using genomic polymerase chain reaction (PCR) and western blot. Three of cell lines were further infected with Lv-EF1α-mCherry. Then mCherry positive cells were sorted by flow cytometry and infected with designed guide RNA (gRNA) vectors which targeted mCherry gene. Subsequently the gene editing activity of Cas9 was detected by genomic PCR, fluorescence microscopic observation and flow cytometry analysis. Results: One hundred Cas9-expressing human liver and gallbladder cancer cell lines were selected. Among them, 35 cell lines expressed Cas9-Neo, 25 expressed Cas9-puro, and 40 expressed mutant Cas9 (mCas9). We also established 3 cell lines with stable expression of mCherry (Huh7-mCas9-M, PLC/PRF/5-Cas9-M and SK-HEP-1-Cas9-M). The results of genomic PCR and sequencing showed that by lentiviral infection with 2 types of designed gRNA, the long fragment deletion of mCherry gene was found in these 3 cell lines. Moreover, mCherry(-)EGFP(+) cells infected with 2 types of gRNA were observed by fluorescence microscope. The results of flow cytometry showed that mCherry(-)EGFP(+) cells accounted from 0.3% to 93.6%. Conclusion: We successfully establish 100 human liver and gallbladder cancer cell lines with stable expression of Cas9 protein and validate their activities of gene editing.