© 2006 European Society for Medical Oncology
symposium article |
Patterns of K-ras mutation in colorectal carcinomas from Iran and Italy (a Gruppo Oncologico dell'Italia Meridionale study): influence of microsatellite instability status and country of origin
1 Department of Oncology and Neurosciences, University G. d'Annunzio, and Center of Excellence on Aging (CeSI), G. d'Annunzio University Foundation, Chieti, Italy; 2 Digestive Disease Research Center (DDRC), 4 Department of Pathology, Shariati Hospital, Tehran University of Medical Sciences, Tehran, Iran; 3 Department of Experimental Pathology and Microbiology, University of Messina, Messina; 5 Department of Oncology, Universita' di Palermo, Palermo; 6 Division of Medical Oncology, National Institute of Oncology, Bari, Italy; 7 Department of Pathology, Mehr Hospital, Tehran, Iran
* Correspondence to: Prof. R. Mariani-Costantini, Department of Oncology and Neurosciences, University G. d'Annunzio and Unit of Molecular Pathology and Genomics, Center of Excellence on Aging (CeSI), ‘Gabriele d'Annunzio’ University Foundation, 66013 Chieti, Italy. Tel: +39-0871-541496; E-mail: rmc{at}unich.it
Background: K-ras mutations are a key step in colorectal cancer progression. Such mutations have been widely studied in case series from Western countries but there are few data on the rate and spectrum of mutations in tumors from countries where the epidemiological features of the disease are different.
Patients and methods: Tumor samples from 182 Iranian colorectal cancer patients (170 sporadic cases and 12 HNPCC cases) were screened for K-ras mutations at codons 12, 13 and 61 by sequencing analysis. The cases were also characterized for microsatellite instability at mononucleotide repeats by PCR and fragment analysis, and classified according to microsatellite instability status. The frequency and the spectrum of K-ras mutations were compared with those observed in a series of colorectal cancer patients from Italy.
Results: K-ras mutations were observed in 68/182 (37.4%) cases. Mutation frequencies were similar in HNPCC-associated, sporadic MSI-H and sporadic microsatellite-stable (MSS) tumors. However, the G13D substitution was more frequent in HNPCC (3/4, 75%) and sporadic MSI-H (7/11, 63.6%) tumors compared to sporadic MSS tumors (11/53, 20.4%) (P <0.01). Comparison of mutations in the two series from Iran and Italy showed a significantly higher frequency of G13D among Italian patients.
Conclusions: While the frequency of K-ras mutations could be similar, the mutational spectrum could be differentially influenced by genetic and environmental factors.
Key words: K-ras mutations, colorectal carcinoma, HNPCC, MSI, Iran, Italy, gene-environment interaction