Aim Little is known about the molecular pathogenesis of sporadic insulinoma which is a type of rare endocrine tumors, and there is a lack of reliable biomarkers to differentiate benign from malignant tumors. Thus we analysed the CpG island methylator phenotype (CIMP) of multiple genes in sporadic insulinamas, as well as the expression of p27 and the relationship between p27 and CIMP.

Materials and Methods Using methylation specific PCR, we examined the methylation status of p16, MLH1, RAR-β, O6-MGMT, THBS1 in 33 sporadic insulinomas and 20 paired pancreatic tissues. The expression of p27 was detected by immunohistochemistry staining. The experimental data were correlated with clinical-pathological characteristics, and were analysed by t-test, chi-square test or Fisher's exact test.

Results The incidence of CIMP-High was found in 33% of insulinomas, higher than its rate in the paired pancreatic tissues, but the difference was not significant (P=0.209). The methylation status of O6-MGMT and p16 were inversely correlated (P=0.003). Compared with the paired pancreaticl tissues, the expression of p27 was reduced in tumors (85% vs. 39%, P=0.008). Moreover, the reduced expression of p27 was significantly related to the methylation of O6-MGMT (P=0.016). The reduced expression of p27 might be related with higher rate of CIMP, but the difference did not reach significance due to the limited number of tumors. The experimental data were not significantly associated with clinical-pathological characteristics in this study.

Conclusion CIMP-High and reduced expression of p27 were observed in a subtype of insulinomas, and these molecular alterations might play a role in tumorigenesis of insulinoma.

Note: This abstract was not presented at the AACR 101st Annual Meeting 2010 because the presenter was unable to attend.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 3670.