Song, Jiaxi

424 Background: Programmed death-1 (PD-1) receptor negatively regulates T cell-mediated responses.PD-1 ligand (PD-L1) is aberrantly expressed in clear cell renal cell carcinoma (ccRCC) and is associated with worse prognosis. Levels of PD-L1 expressions in non-ccRCC and its association with clinicopathological features and survival are unknown. Methods: Formalin-fixed paraffin-embedded (FFPE) specimens were obtained from 97 patients with chromophobe (CHR), papillary (PAP), translocation Xp11.2 (TrL) RCC and oncoytoma (ONC) and were included in the analysis. PD-L1 expression was evaluated by immunohistochemistry using a mouse monoclonal anti-PD-L1 antibody (405.9A11). The assay was validated using FFPE cell line controls known to be positive or negative for PD-L1 expression by flow cytometry. PD-L1 tumor positivity (PD-L1+) was defined as ≥5% tumor cell membrane staining. For PD-L1 expression in immune cells, a combined score based on the intensity of infiltrate and percentage of positive cells was used. Baseline characteristics including stage/grade, and survival data were collected. Comparisons between PD-L1 expression and clinicopathological features were evaluated using chisq or wilcoxon rank sum tests. Cox model tests for association of PD-L1 expression with OS in univariate and multivariable analysis. Results: Among 97 patients, 12 (12.4%) were considered PD-L1+ in tumor cells: 2/36 (5%) of CHR RCC, 5/50 (10%) of PAP RCC, 3/7 (43%) of TrL RCC, and 2/4 (50%) of ONC. PD-L1 positivity in tumor cells was significantly associated with higher stage (p=0.026) and grade (p=0.046), as well as lower OS on univariate (p=0.02) but not multivariate analysis (p=0.29). On the other hand, PD-L1 positivity by immune cells was observed in 50 (51.5%) patients: 13/36 (36%) of CHR RCC, 30/50 (60%) of PAP RCC, 6/7 (86%) of TrL RCC, and 1/4 (25%) of ONC. PD-L1 positivity in immune cells did not correlate with stage (p=0.7), grade (p=0.1) or OS (p=0.8). Conclusions: PD-L1 expression is variable in non-ccRCC and depends on histology and tumor vs. immune cells scoring. Only PD-L1 positivity in tumors cells was associated with aggressive features. Patients with non-ccRCC should not be automatically excluded from trials of agents that target the PD-1/PD-L1 pathway.

616 Background: Polybromo-1 (PBRM1) and BRCA1 associated protein-1 (BAP1) are genes commonly mutated in clear cell RCC (ccRCC) and have been associated with clinical outcome. This work aims to evaluate the impact of PBRM1 and BAP1 expression by IHC in mRCC patients treated with VEGF-TT. Methods: PBRM1 and BAP1 expression was evaluated by IHC in a TMA including 146 mRCC patients. PBRM1 and BAP1 IHC scores were dichotomized as a binary variable: negative (-) or positive (+) (weak positivity was excluded). The associations of PBRM1 or BAP1 expression with baseline clinico-pathological characteristics were evaluated, as well as with overall survival (OS) and time to treatment failure (TTF) usingCox proportional hazards models. Results: Out of 146 patients, 116 and 109 samples had available results for PBRM1 and BAP1 staining, respectively. Overall, 90% (n = 131) patients had ccRCC. 70/116 samples (60%) were PBRM1- and 26/109 patients (24%) were BAP1-. Only 12% (n = 13) of patients had simultaneous negative PBRM1 and BAP1. While there was no association between PBRM1 expression status and clinical factors, BAP1- samples were associated with poor IMDC prognostic risk score (p = 0.004) and higher Fuhrman grade (p = 0.012). PBRM1+ patients showed a trend towards an increased risk of death and a shorter TTF compared to PBRM1- patients (OS: HR = 1.38, 95%CI: 0.92-2.07, p = 0.1; TTF: HR = 1.39, 95%CI: 0.94-2.06, p = 0.1). BAP1 expression was not independently associated with OS or TTF. Conclusions: Loss of PBRM1, but not BAP1 expression showed a trend towards longer TTF and OS in mRCC patients treated with VEGF-TT.

Abstract Purpose: We examined the hypothesis that mutations in mTOR pathway genes are associated with response to rapalogs in metastatic renal cell carcinoma (mRCC). Experimental Design: We studied a cohort of mRCC patients who were treated with mTOR inhibitors with distinct clinical outcomes. Tumor DNA from 79 subjects was successfully analyzed for mutations using targeted next-generation sequencing of 560 cancer genes. Responders were defined as those with partial response (PR) by RECIST v1.0 or stable disease with any tumor shrinkage for 6 months or longer. Nonresponders were defined as those with disease progression during the first 3 months of therapy. Fisher exact test assessed the association between mutation status in mTOR pathway genes and treatment response. Results: Mutations in MTOR, TSC1, or TSC2 were more common in responders, 12 (28%) of 43, than nonresponders, 4 (11%) of 36 (P = 0.06). Mutations in TSC1 or TSC2 alone were also more common in responders, 9 (21%), than nonresponders, 2(6%), (P = 0.05). Furthermore, 5 (42%) of 12 subjects with PR had mutations in MTOR, TSC1, or TSC2 compared with 4 (11%) of 36 nonresponders (P = 0.03). Eight additional non-mTOR pathway genes were found to be mutated in at least 4 of 79 tumors (5%); none were associated positively with response. Conclusions: In this cohort of mRCC patients, mutations in MTOR, TSC1, or TSC2 were more common in patients who experienced clinical benefit from rapalogs than in those who progressed. However, a substantial fraction of responders (24 of 43, 56%) had no mTOR pathway mutation identified. Clin Cancer Res; 22(10); 2445–52. ©2016 AACR. See related commentary by Voss and Hsieh, p. 2320