Genotype-phenotype Correlations In Familial Adenomatous Polyposis And The Study Of The Gut Microbiota With Familial Adenomatous Polyposis Patients

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Genotype-phenotype correlations in familial adenomatouspolyposisBackground:Familial adenomatous polyposis is a colorectal cancer predisposition syndrome.Patients with adenomatous polyposis syndromes are screened for germline mutations in two genes,APC and MUTYH.The spectrums of mutation as well as the genotype-phenotype correlations in familial adenomatous polyposis present clinical impact.Identification of these patients and fanilies who are at extremely high risk of developing cancer is crucial to reduce cancer occurrence and mortality.However,limited data exists on the clinical characterization and genotypic spectrum of familial adenomatous polyposis among Chinese.AIM:To characterize the genotype and phenotype of familial adenomatous polyposis patients in China.Methods:Mutation screening of 46 unrelated probands from Chinese familial adenomatous polyposis patients were performed using next-generation sequencing?NGS?.Clinical data of the index was used to assess genotype-phenotype correlations.Results:Fourty two patients were detected mutations,including 35 APC mutations,3 MUTYH mutaitions and 4 both APC and MUTYH mutaitons.Ten?28.57%?mutations were novel.Two unrelated probands were identified germline mutations of APC at Codon 609?c.1827₁831del?.Patients with that were associated with serious disease and an earlier onset of CRC.MUTYH mutations were identified in 1 proband with biallelic mutation and 2 probands with monoallelic mutations.Both c.55C>T homozygotes carrier and heterozygous carrier showed more than 100 colorectal adenomatous polyps,and the c.55C>T heterozygous carrier was diagnosed as early CRC at the age of 50.Both APC and MUTYH mutations were detected in 4 probands We investigated a Chinese family with the both APC and MUTYH mutations.The identical germline mutation c.4055 T>C of APC and IVS10-2A>G of MUTYH were identified in the proband and among all the affected members in a four generation family.The hereditary pattern of the family was autosomal dominant inheritance.The age of onset with both APC and MUTYH-positive carriers was earlier than the MUTYH-positive carriers and similar to APC-positive carriers.But the age of carcinogenesis was later than that of the APC gene mutation.Extracolonic manifestations were identifieded in 29 cases?56.52%?.Polyp of gastric fundus gland was the most common extracolonic manifestations.Patients with MUTYH mutations showed a mean age of 44.67?range 30-65 years?at disease onset,which significantly differed?p=0.015?from that of the APC mutation cases?mean 29.11,ranging from 9 to 47 years?,and those with both APC and MUTYH mutation?mean 28.5 years ranging from 24 to 36 years,p=0.04?.Both APC and MUTYH mutation carriers showed no difference compared to APC mutation cases?p=0.91?.Of the 35 APC mutation carriers,12 had developed CRC at a mean age of 34 years?range 12-47?.In 23 APC positive carriers without CRC,polyposis was diagnosed at a mean age of 29?range 12-43?.Conclusion:The study revealed the existence of novel mutations in FAP patients.Notably,a particular severe phenotype,involving a higher number of polyps and an earlier onset of colorectal cancer,had been observed in patient carrying mutation at codon 609?c.1827₁831del?of the APC gene.Both heterozygosity and homozygous mutations can be pathogenetic,and the heterozygous mutants also have the risk of CRC.We found both APC and MUTYH mutations in patients.Both APC and MUTYH mutations carriers had a dominant inheritance pattern.Therefore,we suggest that genetic testing of patients with suspected FAP patients should include both APC and MUTYH gene mutation analysis simultaneously.Part ? The study of the gut microbiota with familial adenomatouspolyposis patientsBackground:Colorectal cancer is a multifactorial disease involving genetic,environmental and lifestyle risk factors.Increased evidence has established a role for the gut microbiota in the development of colorectal cancer.However,the microbiota associated with precancerous lesions in hereditary CRC remains largely unknown.FAP is the second most common inherited CRC.Except genetic factors,whether the environmental factors,especially gut microbiota have involved in the development of FAP?AIM:To investigate the features of mucosal associated gut microbita in patients with FAP and to find out the key bacteria that may play an important role in the pathogesis of FAP.Methods:Mucosal biopsies were collected from healthy,colorectal adenoma patients,FAP patients and CRC patients.Global DNA was isolated from every sample,and the V4 region of 16S bacterial r RNA was sequenced on the illumina MiSeq platform.Then,bioinformatics analysis of sequencing data was conducted.Results:Our results revealed that the microbial structures of the healthy,colorectal adenoma patients,FAP patients,and CRC patients differed significantly.At the phylum level,Firmicutes,Bacteroidetes and Proteobacteria were the dominant bacteria in FAP patients,which were basically the same as those in healty,colorectal adenoma patients and CRC patients.Compared with healthy,the Bacteroidetes?29.11%vs 14.88%,P<0.05?and Verrucomicrobia?1.11%0.18%,P<0.05?were statistically significantly more abudandt in FAP patients.Compared with CRC patients,Proteobacteria?31.02%vs 18.71%,P<0.05?was statistically significantly more abudandt and Fusobacteriurn?14.52%vs 2.87%,P<0.05?was statistically significantly less abundant in FAP patients.Compared with colorectal adenoma patients,the Bacteroidetes?29.11%15.87%,P<0.05?was statistically significantly more abudandt in FAP patients.At the genus level,compared with healthy,Helicobacter?1.27%vs 0.25%,P<0.05?was statistically significantly more abudandt in FAP patients.Compared with CRC patients,Helicobacter?1.27%vs 0.02%,P<0.05?and Lactobacillus?1.09%0.49%,P<0.05?,P>0.05)were statistically significantly more abudandt,while Fusobacterium?2.61%vs 14.48%,P<0.05?and rrevotella?0.84%vs 7.65%,P<0.05?were statistically significantly less abundant in FAP patients.Compared with colorectal adenoma patients,Escherichia/Shigella?8.82%22.56%,P<0.05?was statistically significantly less abundant and Helicobacter?1.27%vs 0.06%,P<0.05?were statistically significantly more abudandt in FAP patients.To analyze the significant difference between the different groups,at the genus level,Helicobacter pylori and Lactobacillus were enriched in FAP patients,while Rhodococcus was reduced in FAP patients.Fusobacterium,Peptostreptococcus,Prevotella and streptococci were enriched in CRC patients.Escherichia/Shigella and Ruminococcus 2 were enriched in colorectal adenomas patients.Rothia was enriched in healthy.Helicobacter was more abudandt in FAP patients the healthy,colorectal adenomas patients and CRC patients.The Helicobacter may play an important role in the occurrence and development of FAP.We indentified the Escherichia/Shigella as potential driver bacteria and Fusobacterium,Prevotella,Streptococcus and Peptostreptococcus as potential passenger bacterias.Conclusion:In addition to genetic factors,the occurrence of FAP may be also associated with gut microbiota.Our studies found the microbial composition differed significantly among healthy,colorectal adenomas patients,FAP patients and CRC patients.Helicobacter may play a role in the occurrence and development of FAP.