Identification of the innate normal tissue specific genes and acquired tumor specific genes in determining the tumor transcriptional profiles
Abstract Background: For a specific cancer type, the transcriptional profile is determined by the combination of innate transcriptional features of the original normal tissue and the acquired transcriptional characteristics mediated by genomic and epigenetic aberrations in the tumor development. However, the classification of innate normal tissue specific genes and acquired tumor specific genes is not studied in a pan-cancer manner. Methods: The innate and acquired gene expression profiles in each tumor type were studied using The Cancer Genome Atlas (TCGA) RNA-seq dataset. The prognostic effects of the tumor acquired genes were determined by “survival” package in R software. The methylation of the tumor acquired genes was delineated using TCGA HumanMethylation450 microarray data. Results: 90% liver hepatocellular carcinoma (LIHC) specific genes are derived from innate normal liver specific genes. On the contrary, 90.3% kidney clear cell carcinoma (KIRC) specific genes and 90.9 % lung squamous cell carcinoma (LUSC) specific genes are acquired in the tumor developmental progress. The innate normal tissue specific genes are down regulated in tumor tissues, while, the tumor acquired specific genes are up regulated in the tumor tissues. The innate normal tissue specific genes and the tumors acquired specific genes are both associated with the tumor overall survival in some tumor types. The hyper-DNA methylation of normal tissue specific genes is contributing to the inhibition of normal tissue specific genes expression in cancer cells. And the tumor acquired specific genes are activated by hypo-DNA methylation and genomic aberrations. Conclusions: Our results provide descriptions of the specific transcriptional features across cancer types and suggest that the tumor acquired specific genes are potential targets for anti-cancer therapy.