Colorectal Adenomatous Polyposis: Heterogeneity of Susceptibility Gene Mutations and Phenotypes in a Cohort of Italian Patients

Aims: Colorectal adenomatous polyposis entailing cancer predisposition is caused by constitutional mutations in different genes. APC is associated with the familial adenomatous polyposis (FAP/AFAP) and MUTYH with the MUTYH-associated polyposis (MAP), while POLE and POLD1 mutations cause the polymerase proofreading-associated polyposis (PPAP). Methods: We screened for mutations in patients with multiple adenomas/FAP: 121 patients were analyzed for APC and MUTYH mutations, and 36 patients were also evaluated for POLE and POLD1 gene mutations. Results: We found 20 FAP/AFAP, 15MAP, and no PPAP subjects: pathogenic mutations proved to be heterogeneous, and included 5 APC and 1 MUTYH novel mutations. The mutation detection rate was significantly different between patients with 5-100 polyps and those with >100 polyps (p = 8.154 x 10(-7)), with APC mutations being associated with an aggressive phenotype (p = 1.279 x 10(-9)). Mean age at diagnosis was lower in FAP/AFAP compared to MAP (p = 3.055 x 10(-4)). Mutation-negative probands showed a mean age at diagnosis that was significantly higher than FAP/AFAP (p = 3.46986 x 10(-7)) and included 45.3% of patientswith <30 polyps and 70.9% of patients with no family history. Conclusions: This study enlarges the APC and MUTYH mutational spectra, and also evaluated variants of uncertain significance, including the MUTYH p.Gln338His mutation. Moreover this study underscores the phenotypic heterogeneity and genotype-phenotype correlations in a cohort of Italian patients

Colorectal Adenomatous Polyposis: Heterogeneity of Susceptibility Gene Mutations and Phenotypes in a Cohort of Italian Patients

Aims: Colorectal adenomatous polyposis entailing cancer predisposition is caused by constitutional mutations in different genes. APC is associated with the familial adenomatous polyposis (FAP/AFAP) and MUTYH with the MUTYH-associated polyposis (MAP), while POLE and POLD1 mutations cause the polymerase proofreading-associated polyposis (PPAP). Methods: We screened for mutations in patients with multiple adenomas/FAP: 121 patients were analyzed for APC and MUTYH mutations, and 36 patients were also evaluated for POLE and POLD1 gene mutations. Results: We found 20 FAP/AFAP, 15MAP, and no PPAP subjects: pathogenic mutations proved to be heterogeneous, and included 5 APC and 1 MUTYH novel mutations. The mutation detection rate was significantly different between patients with 5-100 polyps and those with >100 polyps (p = 8.154 x 10(-7)), with APC mutations being associated with an aggressive phenotype (p = 1.279 x 10(-9)). Mean age at diagnosis was lower in FAP/AFAP compared to MAP (p = 3.055 x 10(-4)). Mutation-negative probands showed a mean age at diagnosis that was significantly higher than FAP/AFAP (p = 3.46986 x 10(-7)) and included 45.3% of patientswith <30 polyps and 70.9% of patients with no family history. Conclusions: This study enlarges the APC and MUTYH mutational spectra, and also evaluated variants of uncertain significance, including the MUTYH p.Gln338His mutation. Moreover this study underscores the phenotypic heterogeneity and genotype-phenotype correlations in a cohort of Italian patients

Acid-free glyoxal as a substitute of formalin for structural and molecular preservation in tissue samples

<div><p>Tissue fixation in phosphate buffered formalin (PBF) remains the standard procedure in histopathology, since it results in an optimal structural, antigenic and molecular preservation that justifies the pivotal role presently played by diagnoses on PBF-fixed tissues in precision medicine. However, toxicity of formaldehyde causes an environmental concern and may demand substitution of this reagent. Having observed that the reported drawbacks of commercially available glyoxal substitutes of PBF (Prefer, Glyo-fix, Histo-Fix, Histo-CHOICE, and Safe-Fix II) are likely related to their acidity, we have devised a neutral fixative, obtained by removing acids from the dialdehyde glyoxal with an ion-exchange resin. The resulting glyoxal acid-free (GAF) fixative has been tested in a cohort of 30 specimens including colon (N = 25) and stomach (N = 5) cancers. Our results show that GAF fixation produces a tissue and cellular preservation similar to that produced by PBF. Comparable immuno-histochemical and molecular (DNA and RNA) analytical data were obtained. We observed a significant enrichment of longer DNA fragment size in GAF-fixed compared to PBF-fixed samples. Adoption of GAF as a non-toxic histological fixative of choice would require a process of validation, but the present data suggest that it represents a reliable candidate.</p></div

Representative sample pair showing a better DNA preservation in GAF-fixed <i>versus</i> PBF-fixed tissues.

<p>Representative fragmentation analysis and sequencing results from different methods of two DNA specimens, GAF- and PBF- fixed, respectively (sample pair 4–12). At Bioanalyzer analysis a higher degree of DNA fragmentation was observed in the specimen fixed in PBF (B) compared to the corresponding parallel GAF-fixed sample (A). In addition, the allele frequency of the <i>KRAS</i> p.G12D mutation was considerably higher in GAF fixed specimen with all the employed molecular techniques: panel C shows results of the GAF-fixed sample (Direct sequencing, Pyrosequencing, Mass Spectrometry, from left to right), whereas panel D shows corresponding results in the PBF fixed sample (Direct sequencing, Pyrosequencing, Mass Spectrometry, from left to right). Of note, by NGS this mutation showed a mutant allele frequency of 32% in the GAF-fixed sample <i>versus</i> 7% in the PBF-fixed sample.</p