CD80 and TLR4/MYD88 down regulation in non inflammatory colonic carcinogenesis is associated to CDH13 methylation

P1488 CD80 AND TLR4/MYD88 DOWN REGULATION IN NON INFLAMMATORY COLONIC CARCINOGENESIS IS ASSOCIATED TO CDH13 METHYLATION M. Scarpa1, M. Scarpa1, F. Erroi2, D. Lucia2, S. Basato2, P. Brun3, L. Norberto2, R. De Caro3, I. Castagliuolo3, C. Castoro1. 1Oncological Surgery Unit, VENETO INSTITUTE OF ONCOLOGY, 2Dept of Surgical, Oncological andGastroenterological Sciences, 3Dept of Molecular Medicine, University of Padova, Padova, Italy E-mail Address: marcoscarpa73@yahoo.it INTRODUCTION: Cancer immunosurveillance is a fundamental process that protects the host from unrestrained neoplastic cell growth. The lack of positive costimulatory molecules has been suggested as a mechanism of tumor evasion from immunosurveillance. We recently demonstrated a significant down regulation of the expression of CD80 costimulatory molecule in non inflammatory colon carcinogenesis. Moreover, the innate immunity TLR4/MyD88 signalling pathway has been involved in the modulation of anti-tumor responses as well as cancer growth and progression. However, the mechanisms underlying these events are still largely unknown. Altered genomic methylation is a well established characteristic of tumor cells and specific aberrant methylation events are known to act in the early steps of colon carcinogenesis leading to profound gene expression changes. AIMS & METHODS: The aim of our study was to examine the expression of CD80, TLR4 and MyD88 and to analyse their relationship with genomic methylation in the early steps of the non inflammatory colonic carcinogenesis. A prospective cohort of 63 patients who underwent colonoscopy for screening or postoperative follow up or colonic resection for colorectal cancer was enrolled. Colonic biopsies of healthy mucosa, colonic polyps or colonic adenocarcinoma were taken. CD80, TLR4 and MyD88 mRNA expression was quantified by real time qRT-PCR. The methylation status of CDH13, APC and RUNX gene promoters was assessed by methylation specific PCR. Non parametric statistics was used. RESULTS: In dysplastic colonic mucosa, CD80 and MyD88 mRNA levels resulted significantly lower in patients with methylated CDH13 (p<0.05) than in those with unmethylated CDH13. In patients with methylated CDH13, CD80 mRNA levels were reduced in dysplasia and adenocarcinoma compared to healthy mucosa (p = 0.02). In the healthy mucosa of patients with methylated CDH13, MyD88 mRNA levels resulted lower in cancer (p = 0.07) than in dysplasia and healthy colon. On the contrary, inthe diseased mucosa of patients with unmethylated CDH13 MyD88 appeared to be upregulated (p = 0.02). TLR4 mRNA level showed similar trends but it did not reach the statistical significance. TLR4 mRNA levels inversely correlated with methylation score (tau=-0.47, p<0.01) CONCLUSION: In our series, CDH13 gene methylation seem to be associated to CD80 and MyD88 down regulation in dysplasia in non inflammatory colonic carcinogenesis. Thus, the failure of the immunosurveillance mechanism in non inflammatory carcinogenesis may involve genomic methylation.