[973] Application of ERG/TFF3/HMWCK Triple Immunostain: A Novel Diagnostic Biomarker in Prostate Needle Biopsies

Kyung Park, Francesca Demichelis, Ya-Lin Chiu, Mark A Rubin, Juan Miguel Mosquera. Weill Medical College of Cornell University, New York; University of Trento, Trento, Italy

Background: Trefoil factor 3 (TFF3) expression is associated with various cancers and found to be over-expressed in a subset of prostate cancer (PCa). Functional studies suggest that TMPRSS2-ERG fusion down-regulates TFF3 expression in hormone-naïve prostate cancer. Through these cis interactions on chromosome 21, we posit a mutually exclusive expression of ERG and TFF3. Given this inverse relationship in expression, we developed a triple immunohistochemistry (IHC) assay for ERG, TFF3, and high-molecular weight cytokeratin (HMWCK), and evaluated its utility as a PCa specific biomarker.
Design: ERG, TFF3, and HMWCK antibodies were sequentially applied on three tissue microarrays (TMAs), composed of 103 localized PCa and 50 benign prostate samples. Intensity scores for both nuclear ERG and cytoplasmic TFF3 expression were assigned. Statistical analysis was performed on TMA results. In addition, 21 prostate biopsy samples containing small atypical glands and minute foci of carcinoma were stained using the same IHC protocol.
Results: ERG and TFF3 were expressed in 43% (44/103) and 73% (75/103) of PCa, respectively; co-expression was observed in 21% (22/103) of PCa samples, and 6% of PCa samples (6/103) failed to express ERG or TFF3. The mutually exclusive expression of ERG (nuclear) or TFF3 (cytoplasmic) was statistically significant (p-value < 0.0001 from Chi-Square test) with 90% of ERG-negative tumors (53/59) demonstrating TFF3 expression. 5 benign cases demonstrated TFF3 expression and none were positive for ERG. Sensitivity and specificity of ERG and TFF3 in detecting PCa was 94% and 90%, respectively. In addition to morphology, HMWCK expression in basal cells distinguished TFF3-positive benign glands from cancerous glands. TFF3 and ERG expression was not associated with Gleason grade, tumor stage, or rate of biochemical recurrence. IHC protocol was successful in prostate biopsies, demonstrating its application in clinical practice.
Conclusions: We observed that TFF3 is over-expressed in 73% of primary PCa, significantly more in ERG-negative tumors than ERG-positive ones, and 94% of tumor cases in this study cohort had over-expression of either ERG or TFF3. Combined with HMWCK, we have developed a highly sensitive and specific in situ PCa diagnostic biomarker. The feasibility of this triple stain for molecular characterization of PCa, and as a supplemental diagnostic tool for prostate needle biopsies should be further expanded.
Category: Genitourinary (including renal tumors)

Wednesday, March 21, 2012 1:00 PM

Poster Session VI # 169, Wednesday Afternoon


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