Key Gene Mutations In Colorectal Cancer Progression

Colorectal cancer(colorectal cancer,CRC)remains one of the leading types of malignancy.Despite early detection and therapeutic advances,the overall survival of advanced CRC remains unsatisfactory.Metastasis,including lymphatic and distant metastases,remains the major cause of death in newly diagnosed CRC patients.In addition,Multiple genetic alterations exist in CRC development,but the driving mutations for CRC progression,especially for metastasis,have not been identified.Therefore,current study aimed to validate the relationship between key driver genes mutations and CRC metastasis.1.Mutations of key genes in colorectal cancer progression and metastasisCRC exhibits a linear progression from normal colonic epithelium,adenoma initiation,carcinoma transformation and even to metastasis.Additionally,as CRC evolves from benign to malignant lesions,some key driver genes acquire a series of mutations over time.Thus far,many studies have estimated the association between mutations of the key driver genes and CRC metastasis,but the results of these studies have been contradictory due to heterogeneous factors such as restriction of sample size or population differences.Using bioinformatics analysis,we identified 6 key driver genes,including APC,KRAS,BRAF,PIK3CA,SAMD4,and p53.Through a systematic search in PubMed,Embase,Cochrane Library and TCGA databases,120 articles published by November 30,2017 were included.Then,a meta-analysis was performed to validate the roles of these gene mutations in CRC metastasis.The results showed that KRAS mutations(OR:1.18,95%CI:1.05-1.33)and p53 mutations(OR:1.49,95%CI:1.23-1.80)were associated with CRC metastasis,including lymphatic and distant metastases.Moreover,CRC patients with a KRAS mutation(OR:1.29,95%CI:1.13-1.47),p53 mutation(OR:1.35,95%Cl:1.06-1.72)or SMAD4 mutation(OR:2.04,95%CI:1.41-2.95)were at a higher risk of distant metastasis.Subgroup analysis stratified by ethnic populations indicated that the BRAF mutation was related to CRC metastasis(OR:1.42,95%CI:1.18-1.71)and distant metastasis(OR:1.51,95%CI:1.20-1.91)in an Asian population.No significant association was found between mutations of APC or PIK3CA and CRC metastasis.2.Mutations of AMER1 in colorectal cancer progression and metastasisAnalysing the sequencing samples of 87 CRC patients from MSKCC data and local data(according to doctoral thesis of Sun Wenjie from department of pathology,Zhejiang University),we found that AMER1 gene was highly-frequently mutated in CRC,which were all truncated mutations.Interestingly,AMER1 mutation was significantly associated with concurrent liver metastasis.We knocked down/out AMER1 in SW480 and RKO cell lines using siRNA and Crispr/cas9.Consequently,the migration and invasion potentials of knockdown and knockout CRC cells were significantly enhanced compared with the control group.In addition,decreased expression of E-cadherin and Zo-1,increased expression of Vimentin and MMP9 were observed in AMER1-knockout cells,which suggested that AMER1 inhibited EMT in CRC cells.Furthermore,the nuclear enrichment of ?-catenin appeared in the AMER1 knocked out cells.Further overexpressing AMER1 truncated protein(1-358,1-565,1-830,566-1135,831-1135 and Full),we found the domain of amino acid sequence at positions 831 to 1135 of AMER1 really suppressed ability of migration and invasion of CRC cells.In conclusion:1.Mutations of KRAS,p53,SMAD4 and BRAF play significant roles in CRC metastasis;2.As a cancer suppressor gene,AMER1 gene was highly-frequently mutated in CRC,which was significantly associated with concurrent liver metastasis.3.AMER1 inhibited EMT and metastasis in CRC;and the domain of amino acid sequence at positions 831 to 1135 of AMER1 really suppressed CRC metastasis.