Screening Of Cancer Associated Gene Mutations And Its Clinical Significance In Oral Squamous Cell Carcinoma

Purpose: To investigate the mutation status of oral squamous cell carcinoma-cancer associated gene exons(OSCC-CAGE)(including TP53,NOTCH1,CDKN2 A,CASP8,PTEN,TP63,ANXA1,CDH1,CTNNB1,TGFB1,IGFBP3,GDF15,EGFR)in patients with OSCC,as well as the prognostic value of OSCC-CAGE mutations.Methods:1.The clinical data from 46 locally advanced OSCC patients were collected.2.Patients’ formalin-fixed paraffin-embedded(FFPE)biopsy samples were collected,as well as the matched normal samples from negative lymph nodes.The tumor and normal areas on hematoxylin-eosin stained slide were determined for microdissection and DNA extraction.3.OSCC-CAGE were sequenced for mutations using the Ion Torrent Personal Genome Machine in locally advanced OSCC.GDF15 protein expression was detected using immunohistochemistry.4.Torrent Suite Software v.3.6,Integrative Genomics Viewer v.2.3.Statistical software SPSS18.0 for Windows were used for the analysis of the prognostic function of OSCC-CAGE mutations in OSCC.Results: 1.The mean coverage achieved was 3049-fold in the tumor tissues for OSCC-CAGE sequencing.99% of the targeted bases were represented by at least 10 reads.The more frequently mutated genes are TP53(78%),NOTCH1(33%),CASP8(13%)and CDKN2A(11%).2.78% of TP53 non-synonymous mutations which caused amino acid residue-alterings were distributed in p53 DNA-binding domain;80% of NOTCH1 non-synonymous mutations which caused amino acid residuealterings were distributed in EGF-like domain;55% of CASP8 nonsynonymous mutations which caused amino acid residue-alterings were distributed in interleukin-1 beta converting enzyme homologues;100% of CDKN2 A non-synonymous mutations which caused amino acid residuealterings were distributed in ankyrin repeats.3.Non-synonymous GDF15 mutation was an increased risk factor of loco-regional recurrence-free survival(P=0.035),and there was a tendency that the patients with non-synonymous GDF15 mutation had a worse overall survival(P=0.073)and disease-free survival(P=0.058)than those without it.4.The patients with missense GDF15 mutations had poorer prognostic outcomes than those with wild-type GDF15,including overall survival(P = 0.035),disease-free survival(P = 0.032),loco-regional recurrence-free survival(P = 0.015),and distant metastasis-free survival(P = 0.070).Missense GDF15 mutations was an independent increased risk factor of overall survival(P=0.003),disease-free survival(P=0.015),loco-regional recurrence-free survival(P = 0.008),and distant metastasis-free survival(P = 0.009).Conclusions: 1.TP53,NOTCH1,CASP8 and CDKN2 A are more frequently mutated in locally advanced OSCC,it suggests that their targetable mutations has close relations to the development of OSCC.Our finding that OSCCs have few directly targetable genes has implications for controlling this disease in the future.2.p53 DNA-binding domain,EGF-like domain,interleukin-1 beta converting enzyme homologues and ankyrin repeats are the mutational hotspots domains which were caused by mutant TP53,NOTCH1,CASP8 and CDKN2 A respectively.The amino acid residue-alterings in these domains make a significant impact on the function of proteins.3.Patients with missense GDF15 mutations have significantly poorer outcomes than those with wild-type GDF15.Missense GDF15 mutations could be used as an independent increased risk factor of poor prognosis in OSCC patients.