Abstract 5321: Molecular analysis of melanoma-induced sentinel lymph node immune dysfunction

Abstract

Abstract Introduction Sentinel lymph nodes (SLNs) of melanoma patients show evidence of tumor-induced immune dysfunction. Our previous works have shown that IL10 and IFNγ co-regulate indoleamine-2,3-dioxygenase (IDO)-expressing immunosuppressive dendritic cells (DCs) in melanoma SLNs. The goal of this study is to examine the relationship between melanoma SLN tumor burden and the degree of SLN immune dysfunction as a model to study tumor-induced immune dysfunction. We hypothesize that SLN tumor burden correlates with the degree of SLN immune dysfunction. Methods Patients undergoing SLN biopsy for clinical stages I and II melanomas were enrolled in the study under an IRB-approved protocol. During the SLN biopsy, non-hot and non-blue portion of the SLN was harvested, flash-frozen in liquid nitrogen, and mRNA was extracted. By using quantitative real-time PCR, gene-expressions of cytokines (IL4, IL10, IFNγ, TGFβ, GM-CSF), and the surrogates of immunosuppressive regulatory and effector cells (IDO-expressing DCs and Foxp3-expressing Tregs, respectively) were measured and correlated against the SLN tumor burden (MART1) and against each other. The data were log-transformed for normalization. Statistical test used Students’ t-test and stepwise multivariate regression analysis. Statistical significance was determined at p<0.05. Results Of 200 patients enrolled, SLNs of 74 patients were analyzed in this preliminary analysis. Ten of 74 patients (13.5%) had tumor-positive SLNs. MART1 gene-expression showed a significant difference between the SLN(+) and SLN(−) groups (p=0.04). Among the various cytokines, multivariate analysis showed that only IFNγ gene-expression correlated independently with MART1 gene-expression (p<0.0001, r=0.91). Similar multivariate analyses show that IFNγ (p<0.0001, r=0.78), IL10 (p=0.0037, r=0.60), and TGFβ (p<0.0001, r=0.95) gene-expressions correlated independently with IDO gene-expression. IFNγ (p<0.0001, r=0.87) and GM-CSF (p=0.042, r=0.76) gene-expressions correlated independently with Foxp3 gene-expression. MART1 gene-expression showed independent correlation with IDO (p=0.0002, r=0.75) and Foxp3 (p=0.0002, r=0.75) gene-expressions. Conclusion SLN tumor burden correlates with immunosuppressive IDO and Foxp3 expressions within the SLNs of melanoma patients. Our data are consistent with our theory that melanoma induces expressions of specific cytokines, which in turn, stimulate immune-suppressors within the SLN. This study also supports our previous finding that IL10 and IFNγ co-regulate IDO within the SLN. In our data, IFNγ is the sole cytokine that correlates with the SLN tumor burden and seems to play a central role in tumor-induced immunological changes in the SLN immune microenvironment. 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 5321.