Multiplexed P21/MCM-2 Detection Predicts Relapse and May Identify Tyrosine Kinase Inhibitor-Resistant Patients in Clear Cell Renal Cell Carcinoma.

UNLABELLED: Current clinical tools for predicting relapse and guiding adjuvant therapy in clear cell renal cell carcinoma (ccRCC) lack precision, especially in intermediate-risk disease. This study evaluated whether a nonproliferative tumor cell phenotype, P21 (CDKN1A inhibitor)-positive and MCM2 (DNA replication protein)-negative (P21+/MCM2-), could serve as a robust biomarker to improve prognostic stratification and guide postnephrectomy treatment decisions. We used multiplex immunofluorescence and Artificial Intelligence-based image analysis on nephrectomy specimens from three independent ccRCC cohorts: UK arm of the SORCE trial (n = 382), Korean (n = 71), and Scottish (n = 88). An optimal 2% cutoff for P21+/MCM2- cells was determined using X-tile software. Additional analyses assessed endoglin/CD105 coexpression, paired primary-metastatic samples (n = 41), and associations with adjuvant sorafenib therapy. In two intermediate-risk ccRCC cohorts (SORCE, n = 63; Korean, n = 71), patients with >2% P21+/MCM2- cells had significantly longer time to relapse [HR = 0.17; 95% confidence interval (CI), 0.06-0.54; HR = 0.27; 95% CI, 0.10-0.72]. Prognostic value was confirmed in high-risk (SORCE, HR = 0.43; 95% CI, 0.19-0.99) and all-risk (Scottish, HR = 0.37; 95% CI, 0.14-0.98) cohorts. Notably, patients with high P21+/MCM2- levels on placebo fared better than those receiving adjuvant TKI therapy (HR = 0.29; 95% CI, 0.16-0.50). In 41 paired samples, 85% showed higher P21+/MCM2- abundance in metastases than in primary tumors. As a conclusion, P21+/MCM2- cell count is a robust biomarker that refines relapse risk stratification in ccRCC and identifies patients who may not benefit from adjuvant tyrosine kinase inhibitor (TKI) therapy. High levels of these nonproliferative, senescent-like cells suggest tumor dormancy and a more favorable outcome without treatment.

SIGNIFICANCE: After surgery for clear cell renal cell carcinoma, relapse risk and benefit from adjuvant therapy remain uncertain. We identify a distinct P21+/MCM2- tumor phenotype, nonproliferative and senescent-like, linked to favorable outcomes. Across three cohorts, >2% of these cells reduced relapse risk, but benefit was lost with adjuvant TKIs.