Gene expression profiling of MYC-driven tumor signatures in porcine liver stem cells by transcriptome sequencing

AIM:To identify the genes induced and regulated by the MYC protein in generating tumors from liver stem cells.METHODS:In this study,we have used an immortal porcine liver stem cell line,PICM-19,to study the role of c-MYC in hepatocarcinogenesis.PICM-19 cells were converted into cancer cells(PICM-19-CSCs)by overexpressing human MYC.To identify MYC-driven differential gene expression,transcriptome sequencing was carried out by RNA sequencing,and genes identified by this method were validated using real-time PCR.In vivo tumorigenicity studies were then conducted by injecting PICM-19-CSCs into the flanks of immunodeficient mice.RESULTS:Our results showed that MYC-overexpressing PICM-19 stem cells formed tumors in immunodeficient mice demonstrating that a single oncogene was sufficient to convert them into cancer cells(PICM-19-CSCs).By using comparative bioinformatics analyses,we have determined that>1000 genes were differentially expressed between PICM-19 and PICM-19-CSCs.Gene ontology analysis further showed that the MYCinduced,altered gene expression was primarily associated with various cellular processes,such as metabolism,cell adhesion,growth and proliferation,cell cycle,inflammation and tumorigenesis.Interestingly,six genes expressed by PICM-19 cells(CDO1,C22orf39,DKK2,ENPEP,GPX6,SRPX2)were completely silenced after MYC-induction in PICM-19-CSCs,suggesting that the absence of these genes may be critical for inducingtumorigenesis.CONCLUSION:MYC-driven genes may serve as promising candidates for the development of hepatocellular carcinoma therapeutics that would not have deleterious effects on other cell types in the liver.