Discovery of Aberrant Alteration of Genome in Colorectal Cancer by Exome Sequencing

Background: This study analyzed multiple parameters including somatic single nucleotide variations (SNVs), Insertion/Deletions, significantly mutated genes (SMGs), copy number variations and frequently altered pathways aims to discover novel aberrances in the tumorigenesis of colorectal cancer (CRC). Materials and Methods: Exome sequencing was performed on an Illumina platform to identify novel potential somatic variances in 34 paired tumor and adjacent normal tissues from 17 CRC patients. Results were compared with databases (dbSNP138, 1000 genomes SNP, Hapmap, Catalogue of Somatic Mutation of Cancer and ESP6500) and analyzed. MuSic software was used to identify SMGs. Results: In total, 1,637 somatic SNVs in 17 analyzed tumors were identified. Only 7 SNVs were shared by more than 1 tumor, suggesting that over 99% of the analyzed SNVs were independent events. Mutation of KRAS p. G12D and ZNF717 p. L39V were the most common SNVs. Moreover, 10 SMGs namely KRAS, TP53, SMAD4, ZNF717, FBXW7, APC, ZNF493, CDR1, the Armadillo repeat containing 4 (ARMC4) and sulfate-modifying factor 2 (SUMF2) were found. Among those, ZNF717, ZNF493, CDR1, ARMC4 and SUMF2 were novel frequent genes in CRC. For copy number variations analysis, gains in 10q25.3, 1p31.1, 1q44, 10q23.33, 11p15.4 and 20q13.33, and loss of 3q21.3 and 3q29 were frequent aberrations identified in our results. Conclusions: We frequently found novel genes ZNF717, ZNF493, CDR1, ARMC4 and SUMF2 and gains in 10q25.3, which may be functional mutation in CRC. The high-frequency private events such as SNVs confirm the highly heterogeneous mutations found in CRCs. The mutated genes sites in different patients may vary significantly, which may also be more challenging for clinical treatment.