Tumor-infiltrating neutrophils predict therapeutic benefit of tyrosine kinase inhibitors in metastatic renal cell carcinoma

Tumor-infiltrating neutrophils (TINs) show diverse predictive effects in the context of different cancer types and therapeutic regimens. In this study we investigated their relevance with therapeutic effect of tyrosine kinase inhibitors (TKIs) in metastatic renal cell carcinoma (mRCC). Two independent datasets including 271 mRCC patients treated by TKIs or IL-2/IFN-alpha based immunotherapy were retrospective included, and TINs were detected by immunohistochemistry. The presence of TINs was observed in 50 (45.0%) samples of the TKI cohort and in 73 (45.6%) samples of the immunotherapy cohort. TINs were associated with shorter overall survival (HR, 1.776; 95%CI, 1.191-2.650; p = 0.004) in the TKI cohort, but not in the immunotherapy cohort (HR, 1.074; 95%CI, 0.767-1.505; p = 0.672). Multivariate Cox analysis confirmed the independent prognostic value of TINs for TKI-treated patients (HR, 2.078, 95%CI, 1.352-3.195; p = 0.001), apart from other parameters. Moreover, survival benefit of TKI therapy was superior to IL-2/IFN-alpha immunotherapy only among TINs-absent patients (HR, 1.561; 95%CI, 0.927-2.629; p = 0.094). Data mining in the TCGA cohort of renal cell carcinoma revealed the predominant immunosuppressive function of TINs in renal cell carcinoma. The negative correlation between TINs and intratumoral CD8(+) T cells was further confirmed in the TKI cohort (p = 0.019), the immunotherapy cohort (p = 0.001) and the TCGA cohort (p < 0.001). In conclusion, the presence of TINs was an independent, unfavorable prognostic factor in TKI-treated mRCC patients. TINs could also predict therapeutic benefit of TKIs over IL-2/IFN-alpha immunotherapy. These findings should be further confirmed within datasets of clinical trials or prospective observational studies.