[963] Prostate Specific Membrane Antigen (PSMA) Expression in Bladder Cancer Neovasculature and Tumor Subtypes

MK Samplaski, W Heston, C Magi-Galluzzi, DE Hansel. The Cleveland Clinic, Cleveland, OH

Background: PSMA is a transmembrane receptor expressed on prostate cancer cells that correlates with a more aggressive phenotype. Recent studies have demonstrated PSMA expression in numerous other tissue types, as well as tumor neovasculature. We sought to determine the extent of PSMA expression in both bladder cancer vasculature and bladder cancer cells of various subtypes.
Design: Immunohistochemical analysis (IHC) of PSMA was performed using tissue microarrays constructed from 97 urothelial carcinomas (UCCs), 37 squamous cell carcinomas, 17 adenocarcinomas and 17 small cell carcinomas of the bladder. We used a PSMA monoclonal antibody obtained from Dako (clone 3E6, dilution 1:100), which recognizes the epitope present in the 57-134 amino acid region of the extracellular portion of the PSMA molecule. Intensity of IHC staining was scored as 0 (no expression) to 3+ (strong expression), with 2-3+ IHC considered a positive result.
Results: All bladder cancers examined demonstrated robust expression of PSMA in the tumor vasculature, suggesting a potential role for PSMA in mediating new vessel ingrowth and providing a valuable internal control. Most commonly, PSMA expression was identified in small cell carcinoma (3/17; 18%), with co-expression of PSMA in admixed forms of bladder cancer, including glandular elements (1/3) and urothelial elements (1/3). PSMA expression was rare in instances of pure UCC (3/97; 3%) and pure adenocarcinoma (2/17; 12%). No case of pure squamous cell carcinoma of the bladder was positive for PSMA within the tumor cells.
Conclusions: PSMA is commonly expressed in bladder cancer neovasculature and may play a potential active role in new vessel ingrowth. Additionally, PSMA may be occasionally expressed in bladder cancer subtypes, including small cell carcinoma of the bladder. These findings warrant caution in the diagnostic use of PSMA to determine potential prostate origin of invasive carcinoma in this anatomic site.
Category: Genitourinary (including renal tumors)

Wednesday, March 24, 2010 1:00 PM

Poster Session VI # 145, Wednesday Afternoon

 

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