Construction of ceRNA networks reveals differences between distal and proximal colon cancers.

Although colon cancer is often referred to as a homogeneous entity, an increasing number of studies have revealed that colon cancer can be divided according to the anatomic site of the cancer. However, few studies have reported the difference between distal and proximal colon cancer with regard to molecular mechanism, and especially non‑coding RNA molecules. In the present study, the data of 186 colon tumour tissues and 17 adjacent non‑tumour colon tissues in the left colon and 229 colon tumour tissues and 21 adjacent non‑tumour colon tissues in the right colon were obtained from The Cancer Genome Atlas (TCGA). A total of 879 lncRNAs, 165 miRNAs and 2,028 mRNAs were identified as left‑specific RNAs [log2(fold change)>2, FDR<0.01]. There were 916 lncRNAs, 227 miRNAs and 2,069 mRNAs identified in right colon cancer. The Kyoto Encyclopaedia of Genes and Genomes (KEGG) pathways were analysed for 2,028 mRNAs from left colon cancer and 2,069 mRNAs from right colon cancer. After removing the elements of the intersection from side‑specific lncRNAs of the left and right, we identified specific lncRNAs included exclusively in left or right colon cancer, including 277 lncRNAs in left colon cancer and 314 lncRNAs in right colon cancer. Among these lncRNAs, 20 lncRNAs from the left and 25 lncRNAs from the right were revealed to be associated with overall survival. Then, ceRNA networks were constructed. There were 18 lncRNAs, 22 miRNAs and 57 mRNAs included in the left colon cancer ceRNA network and 21 lncRNAs, 27 miRNAs and 55 mRNAs included in the right ceRNA network. In total, 15 lncRNAs were revealed to be significantly related to clinical features, two of which were ascertained by testing the mRNA expression of tissues. In conclusion, our research aimed to detect the difference between colon cancer in the left and the right colon and to assist in the identification of new potential biomarkers to be used for diagnostic and prognostic purposes.