Antibodies targeting the programmed cell death protein 1/programmed death-ligand 1 (PD-L1) interaction have shown clinical activity in multiple cancer types. PD-L1 protein expression is a clinically validated predictive biomarker of response for such therapies. Prior studies evaluating the expression of PD-L1 in primary prostate cancers have reported highly variable rates of PD-L1 positivity. In addition, limited data exist on PD-L1 expression in metastatic castrate-resistant prostate cancer (mCRPC). Here, we determined PD-L1 protein expression by immunohistochemistry using a validated PD-L1-specific antibody (SP263) in a large and representative cohort of primary prostate cancers and prostate cancer metastases. The study included 539 primary prostate cancers comprising 508 acinar adenocarcinomas, 24 prostatic duct adenocarcinomas, 7 small-cell carcinomas, and a total of 57 cases of mCRPC. PD-L1 positivity was low in primary acinar adenocarcinoma, with only 7.7% of cases showing detectable PD-L1 staining. Increased levels of PD-L1 expression were noted in 42.9% of small-cell carcinomas. In mCRPC, 31.6% of cases showed PD-L1-specific immunoreactivity. In conclusion, in this comprehensive evaluation of PD-L1 expression in prostate cancer, PD-L1 expression is rare in primary prostate cancers, but increased rates of PD-L1 positivity were observed in mCRPC. These results will be important for the future clinical development of programmed cell death protein 1/PD-L1-targeting therapies in prostate cancer.

We previously demonstrated the ability to detect metastatic prostate cancer using N-[N-[(S)-1,3-dicarboxypropyl]carbamoyl]-4-18F-fluorobenzyl-l-cysteine (18F-DCFBC), a low-molecular-weight radiotracer that targets the prostate-specific membrane antigen (PSMA). PSMA has been shown to be associated with higher Gleason grade and more aggressive disease. An imaging biomarker able to detect clinically significant high-grade primary prostate cancer reliably would address an unmet clinical need by allowing for risk-adapted patient management. Methods We enrolled 13 patients with primary prostate cancer who were imaged with 18F-DCFBC PET before scheduled prostatectomy, with 12 of these patients also undergoing pelvic prostate MR imaging. Prostate 18F-DCFBC PET was correlated with MR imaging and histologic and immunohistochemical analysis on a prostate-segment (12 regions) and dominant-lesion basis. There were no incidental extraprostatic findings on PET suggestive of metastatic disease. Results MR imaging was more sensitive than 18F-DCFBC PET for detection of primary prostate cancer on a per-segment (sensitivities of up to 0.17 and 0.39 for PET and MR imaging, respectively) and per-dominant-lesion analysis (sensitivities of 0.46 and 0.92 for PET and MR imaging, respectively). However, 18F-DCFBC PET was more specific than MR imaging by per-segment analysis (specificities of 0.96 and 0.89 for PET and MR imaging for corresponding sensitivity, respectively) and specific for detection of high-grade lesions (Gleason 8 and 9) greater than 1.0 mL in size (4/4 of these patients positive by PET). 18F-DCFBC uptake in tumors was positively correlated with Gleason score (ρ = 0.64; PSMA expression, ρ = 0.47; and prostate-specific antigen, ρ = 0.52). There was significantly lower 18F-DCFBC uptake in benign prostatic hypertrophy than primary tumors (median maximum standardized uptake value, 2.2 vs. 3.5; P = 0.004). Conclusion Although the sensitivity of 18F-DCFBC for primary prostate cancer was less than MR imaging, 18F-DCFBC PET was able to detect the more clinically significant high-grade and larger-volume tumors (Gleason score 8 and 9) with higher specificity than MR imaging. In particular, there was relatively low 18F-DCFBC PET uptake in benign prostatic hypertrophy lesions, compared with cancer in the prostate, which may allow for more specific detection of primary prostate cancer by 18F-DCFBC PET. This study demonstrates the utility of PSMA-based PET, which may be used in conjunction with MR imaging to identify clinically significant prostate cancer.

OBJECTIVE To evaluate programmed death ligand 1 (PD-L1) expression in urothelial carcinoma of the bladder in relationship with tumor-infiltrating CD8+ T cells. MATERIALS AND METHODS Tissue microarrays were prepared from 56 cystectomy specimens performed at our hospital (1994–2002). PD-L1 immunoexpression was assessed using the murine antihuman PD-L1 monoclonal antibody 5H1. Extent of membranous PD-L1 expression was assigned in each spot. Spots showing ≥5% expression were considered positive. Average PD-L1 expression per tumor was also calculated (5% positivity cutoff). “High CD8 density” was defined as the presence of ≥60 CD8+ intraepithelial lymphocytes per high power field in a given spot. A tumor was considered high density if ≥50% of its spots were of high density. RESULTS PD-L1 expression was positive in approximately 20% of tumors. None of the benign urothelium spots expressed PD-L1. High CD8 density was observed in approximately 20% of cases. CD8 density did not correlate with PD-L1 expression. Overall survival (OS) and disease-specific survival (DSS) rates were 14% and 28%, respectively (median follow-up, 31.5 months). PD-L1 expression was associated with age at cystectomy (P = .01). Remaining clinicopathologic parameters were not associated with PD-L1 expression or CD8 density. High CD8 density was associated with favorable OS (P = .02) and DSS (P = .02). The same was true when CD8 density was adjusted for demographic and clinicopathologic parameters. There was no correlation between PD-L1 expression and outcome. CONCLUSION High intratumoral CD8+ T cell density is associated with better OS and DSS in invasive urothelial carcinoma of the bladder. We found no correlation between PD-L1 expression and outcome.

Purpose Reports of cytomegalovirus (CMV) detection in high-grade gliomas (HGG)/glioblastoma (GBM) have been conflicting. We undertook a comprehensive approach to determine presence or absence of CMV in tissue, plasma and serum of HGG patients. Experimental Design In a retrospective arm, 25 fresh frozen tissues from GBM patients were tested for CMV by real-time PCR. Tissue microarrays from 70 HGG patients were tested by immunohistochemistry (IHC) and 20 formalin-fixed paraffin-embedded (FFPE) GBM tissues by IHC and chromogenic in situ hybridization (CISH), targeting CMV-encoded IE1/2 and pp65. In a prospective arm, 18 patients with newly-diagnosed HGG provided tissue and blood samples. Results All retrospectively collected tissues were negative for CMV by all methods. In the prospective cohort, 18 patients with newly-diagnosed HGG provided blood samples at the time of diagnosis and during follow-up. Of 38 plasma specimens, CMV DNA was detected in 3 of 18 samples at baseline and 1 of 20 follow-up samples. Serum CMV IgG was positive in 8 of 15 (53%) of patients. Among the FFPE samples tested in the prospective arm, all were negative for CMV by IHC, CISH and PCR. Conclusions Utilizing 6 highly-sensitive assays with 3 orthogonal technologies on multiple specimens and specimen types, no evidence for CMV in GBM tissues was found. Our findings call for multicenter blinded analyses of samples collected from different geographical areas with agreed upon study designs and determination of causality or lack thereof of CMV in HGG/GBM for future guidance on the necessity anti-viral and/or CMV-based therapies.