Abstract
BACKGROUND: Immune checkpoint inhibition with ipilimumab and nivolumab prolongs survival in renal cell carcinoma (RCC). Tumors with sarcomatoid and/or rhabdoid features are considered responsive to immune checkpoint inhibitors (ICIs), despite their aggressive nature. Although sarcomatoid/rhabdoid dedifferentiation is not considered a distinct subtype of RCC, these tumors differ clinically and molecularly from nonsarcomatoid/rhabdoid RCC tumors. We sought to identify biomarkers underlying responsiveness to ICIs and compare the immune microenvironments of tumors with or without sarcomatoid/rhabdoid components. PATIENTS AND METHODS: We constructed a tissue microarray from archived RCC tumors collected from patients treated with first-line ipilimumab and nivolumab. Digital spatial profiling was carried out using NanoString's GeoMx platform with a panel of 58 proteins. Regions of interest were segmented into immune [cluster of differentiation (CD)68+ and CD45+] and tumor [positive for both cytokeratin and carbonic anhydrase 9 (CAIX+ CK+)] compartments. To investigate marker expression in tumors with and without sarcomatoid/rhabdoid dedifferentiation, two additional tissue microarrays were analyzed, comprising cohorts of patients treated with heterogeneous first-line therapies. Key findings were validated by immunohistochemistry. RESULTS: After quality control, 44 pretreatment tumors from 44 patients were analyzed. Tumor programmed death-ligand 1 (PD-L1) expression was higher in responders (P = 0.03) and associated with improved progression-free survival [PFS; hazard ratio (HR) 0.4, 95% confidence interval (CI) 0.2-0.8, P = 0.01] and overall survival (OS; HR 0.2, 95% CI 0.06-0.5, P < 0.005) on multivariable analysis. This finding was confirmed by immunohistochemistry. In the CD45+ compartment of sarcomatoid/rhabdoid tumors, CD25 expression was associated with worse PFS (HR 58.8, 95% CI 2.8-1250, P = 0.01). Differential expression analysis showed higher CD66b in sarcomatoid/rhabdoid tumors (log(2) fold change = 2.2, P < 0.001), validated by immunohistochemistry with significantly higher myeloperoxidase (MPO) staining (χ(2) = 15.7, df = 3, P < 0.001). CONCLUSIONS: Tumor PD-L1 is associated with better PFS and OS after ipilimumab + nivolumab. In the sarcomatoid/rhabdoid subset, lower CD25 (a marker of regulatory T cells) was associated with improved PFS, while increased neutrophil infiltration (CD66b+/MPO+) emerged as a novel feature of sarcomatoid/rhabdoid tumors, which may be harnessed for therapeutic benefit in this population.