Molecular analysis of hereditary colorectal cancer: Familial adenomatous polyposis and Turcots sindrome

M. De Rosa Ph.D. a, M. I. Scarano Ph.D., M.D. b, L. Panariello Ph.D., M.D. a, G. Romano M.D. c, G. Riegler Ph.D., M.D. d, G. B. Rossi M.D. e, G. Pettinato Ph.D., M.D. b, P. Izzo Ph.D. a

a Dipto Biochimica e Biotecnologie Mediche, CEINGE-Biotecnologie Avanzate, and b Dipto Scienze Biomorfologiche e Funzionali; Università di Napoli, Federico II, Napoli; c Chirurgia Generale, Ospedale Moscato, Avellino; d Cattedra di Gastroenterologia, Seconda Università di Napoli, and e Endoscopia Digestiva, Ist. Nazionale Tumori, Fondazione G. Pascale, Napoli; Italia.

Aim: In this study, 36 unrelated FAP (Familial Adenomatous Polyposis) families and one Turcot family from the Neapolitan area have been analyzed in order to identify the underlying molecular defects and to clarify the mode of transmission of the Turcot family showing an apparently recessive inheritance. Methods: Single strand conformation polymorphism (SSCP), protein truncation test (PTT) and sequencing analyses were utilized to investigate for mutation in mismatch repair (MMR), adenomatous polyposis coli (APC) and TGF&beta-RII genes. Genomic DNA from normal and tumor mucosa of the Turcot proband was analyzed for instability at markers BAT40, BAT26, D17S250 and D18S69. These markers were also analyzed in diluted genomic DNA from normal mucosa of Turcot and HNPCC patients. Results: We were able to identify 26/36 FAP mutant alleles, comprising 20 different APC mutations. Among these, six are novel frameshift mutations: 2800-2804delACTT, R875X, C599X, Q1542X, 893-894del AC and 591-592delAC. Results on the Turcot family indicate that the proband was carrier of two truncating germline mutations, inherited from her unaffected parents, within the PMS2 gene and showed a severe positive replication errors phenotype. Furthermore, high DNA instability was found also in normal colon mucosa. Conclusions: The identification of the molecular alterations responsible for the onset of these diseases, the clarification of the mode of inheritance in the Turcot family and the mechanism involved in cancer development are essential for cancer prevention and therapy. Moreover, our data on the Turcot family represent the first evidence for autosomal recessive transmission of this syndrome.

Paper presented at the International Symposium on Predictive Oncology and Intervention Strategies; Paris, France; February 9 - 12, 2002; in the section on Familial and Hereditary Cancer.