Bim Expression in Peritumoral Lymphocytes is Associated with Survival in Patients with Metastatic Clear Cell Renal Cell Carcinoma

BACKGROUND: Bim (BCL-2-interacting mediator of cell death) is a downstream pro-apoptotic signaling molecule activated by the PD-1 pathway. OBJECTIVE: We sought to determine if Bim expression in peritumoral T-lymphocytes (PTLs) is associated with survival in patients with metastatic clear cell renal cell carcinoma (ccRCC). METHODS: Immunohistochemistry staining for Bim was performed on paraffin-embedded tumor tissue blocks from patients with metastatic ccRCC who underwent nephrectomy between 1990-2004. Associations of Bim expression with cancer-specific survival (CSS) and overall survival (OS) from date of metastasis were evaluated using multivariable Cox regression models, adjusting for age, sex, and metastases-score. RESULTS: 525 patients with metastatic ccRCC, of whom 169 (32%) had metastases at time of nephrectomy were studied. After multivariable adjustment, high Bim expression remained associated with worse CSS (HR=1.31; 95% CI 1.07-1.59; p=0.008) and OS (HR=1.28; 95% CI 1.06-1.55; p=0.01). The interaction between Bim and PD-L1 was not statistically significant for CSS (p=0.68) or OS (p=0.57), suggesting that the associations between Bim and survival outcomes were not significantly different based on tumor PD-L1 expression. CONCLUSION: High Bim expression in PTLs at nephrectomy is prognostic of worse CSS and OS in patients with metastatic ccRCC, irrespective of tumor PD-L1 expression. The role of earlier PD-1/PD-L1-directed therapy warrants evaluation in these patients.