Non-Clear Cell Renal Cell Carcinoma Has an Immune-Cold Phenotype That Affects Response to Immune Checkpoint Inhibitors.

UNLABELLED: Data on the clinical outcomes of immune checkpoint inhibitor (ICI) therapy and tumor immune microenvironment (TIME) profiles in non-clear cell renal cell carcinoma (nccRCC) remain limited. In this study, we retrospectively compared the effectiveness profile of first-line ICI combination therapy between clear-cell renal cell carcinoma (ccRCC) and nccRCC. Additionally, genome-wide gene expression and tumor-infiltrating immune cell (TIIC) profiling were performed using RNA sequencing and flow cytometry, respectively. Of 266 patients, 56 (21%) were histopathologically diagnosed with nccRCC. Progression-free survival [PFS; hazard ratio (HR), 0.59, P = 0.0059] and overall survival (OS; HR, 0.42, P = 0.0006) were shorter in patients with nccRCC than in patients with ccRCC. Gene expression analysis of 140 RCC samples revealed the downregulation of immune-related and angiogenesis-related pathways in nccRCC. The survival difference between ccRCC and nccRCC was more significant with the combination of ICIs and vascular endothelial growth factor receptor tyrosine kinase inhibitors (VEGFR-TKI; PFS: HR, 0.45, P = 0.0026; OS: HR, 0.26, P < 0.0001) than with dual ICI combinations (PFS: HR, 0.64, P = 0.0761; OS: HR, 0.59, P = 0.131). TIIC profiling of 116 samples showed that nccRCC exhibited an "immune-cold" TIME phenotype characterized by a decrease in TIICs, including CD8+ T cells. In conclusion, the downregulation of immune-related pathways, caused by an "immune-cold" TIME phenotype, is potentially involved in the pathogenesis underlying the decrease in the therapeutic efficacy of ICI combination therapy for nccRCC.

IMPLICATIONS: nccRCC harbors an "immune-cold" TIME phenotype characterized by reduced TIICs, which in turn drive the downregulation of immune-related pathways and may contribute to decreased responsiveness to ICI therapy.