Abstract for presentation at 11th International Congress of Human Genetics

Familial, clinical and immunophenotypical characterization of HNPCC-suspected patients. Improved family selection for genetic testing analyzing Cdk2 and ß-catenin expression

  • Laura Valle, Spanish National Cancer Centre (CNIO), Madrid, Spain
  • Ana Mª Dotor, Spanish National Cancer Centre (CNIO), Madrid, Spain
  • Pablo Carbonell, Genetics Unit, Hospital Virgen de la Arrixaca, Murcia, Spain
  • Victoria Fernández, Spanish National Cancer Centre (CNIO), Madrid, Spain
  • Roger Milne, Spanish National Cancer Centre (CNIO), Madrid, Spain
  • Javier Benítez, Spanish National Cancer Centre (CNIO), Madrid, Spain

    • Hereditary Non-Polyposis Colorectal Cancer (HNPCC) is defined by the Amsterdam and Bethesda criteria and colorectal tumors belonging to these families are characterized by microsatellite instability (MSI) due to aberrant mismatch repair (MMR). The genetic cause of HNPCC consists of MMR germline mutations, mainly in MLH1 and MSH2 genes, and to lesser extent in MSH6 and PMS2. Given that genetic testing for germline mutations is technically challenging and costly, different criteria have been developed to help identify HNPCC families carrying a germline MMR mutation. At present, this selection is based on: a strong family history of colorectal or other HNPCC-associated tumors (Amsterdam and Bethesda guidelines); tumor MSI; and tumor loss of MMR protein expression.
    To characterize non-polyposis colorectal tumors with a familial component, we defined different tumor groups based on MSI and on the presence of germline MMR mutations and established familial, clinicopathological and immunohistochemical differences among the groups defined, in order to get differential features that could help us to better select candidate families for genetic testing, defining new prescreening criteria or improving the already existing ones.
    271 tumors belonging to different HNPCC-suspected patient were included in four tissue-microarrays: 126 MSI and 145 MSS (microsatellite stable), collecting familial and clinical information from each patient. Immunohistochemical staining with a wide panel of antibodies, including MLH1; MSH2; MSH6; Bcl-2; ß-catenin; Cdk2; Chk2; cyclins A, B1, D1 and E; Cytokeratin 20, E-cadherin; Ki-67; p16; p21, p27; p53, RAD50; Rb-P; Skp2; and SMAD4, was performed.
    When comparing MSI and MSS cases, we observed that MSI tumors better fulfill HNPCC criteria; show an earlier age of onset, more frequently proximal location, longer disease free survival, lack or reduced expression of MMR proteins, higher expression of cyclins A, D1 and E, of p16, Skp2, SMAD4 and Ki-67, overexpression of p53 and RAD50, and aberrant nuclear expression of ß-catenin. Within the MSI group, those cases with germline MMR mutation differ from those in with no alteration in the germline has been identified, in better fulfilling the HNPCC guidelines, in showing an earlier age of onset, lack of MMR protein expression, and nuclear expression of Cdk2. When comparing MLH1 and MSH2 mutated cases, main differences were observed in ß-catenin and MMR proteins' expression.
    Based on the results obtained, we propose a modified HNPCC screening strategy including the already existing tools, as well as Cdk2 an ß-catenin expression, obtaining high sensitivity and specificity, and notably reducing time and money costs.

    Conference Organiser - ICMS Pty Ltd