Exploratory analysis on crosstalk between intra-tumor immunity and FGF/FGFR pathway in clear cell renal cell carcinoma.

e16525 Background: Clear cell renal cell carcinoma (ccRCC) patients classically show good response to VEGFR inhibitors; however, the biological basis by which FGFR inhibition provides tumor response was not well understood. Here, we performed an exploratory analysis of the relationship between the FGF/FGFR pathway and intra-tumor immunity to support the effectiveness of FGFR inhibitors for ccRCC. Methods: We used whole transcriptome data and immunohistochemistry with metastatic clear cell RCC specimens from patients who were treated at the Yamagata University Hospital (n = 57). FFPE samples were prepared from the primary lesions of treatment-naive metastatic ccRCC patients. FFPE was sliced by a pathologist to evaluate the immunological microenvironment. RNA extraction and immunostaining were performed at the same site. Immuno-histological quantification was performed by automatically analysis system HALO in digital whole slide imaging. Hierarchical clustering was performed, and the cohort was divided based on the profile of the FGF and immune cells. We analyzed the cancer-specific survival based on the FGF cluster classification and investigated the relationship between FGF-FGFR expression and immune cell infiltration that were evaluated histologically. Results: RNA transcriptome data showed that FGF2 and FGF7 were widely expressed in ccRCC. Hierarchical cluster analysis based on the FGF expression profile (intrinsic FGFs were excluded) revealed that metastatic ccRCC had three distinct patterns. Cluster1 showed low FGFs expression, except for FGF2 and 7, while Cluster2 and 3 expressed multiple FGFs. Survival analysis showed Cluster2and 3 had a poor cancer-specific survival rate than Cluster1 (Logrank test, p = 0.05). However, no association was detected between the FGF cluster classification and the infiltration of immune cell count in immunohistological analysis. In comparison of the expression of each FGF subfamily and the positive cells of CD4, CD8, CD68 and CD31 (Mann–Whitney U test, p < 0.05), CD4 and CD8 were higher in the cases expressing FGF20. While most FGF subfamilies have been suggested to be less associated with immune cell infiltration (excluding FGF20), further analysis among FGF receptor expression and immune signatures are ongoing. Conclusions: Our study demonstrates the possibility of intra-tumor interaction between FGF/FGFR axis and immune infiltration in ccRCC.