Chromosomal translocations involving the ETS transcription factors, such as ERG and ETV1, are frequent events in human prostate cancer pathogenesis. In particular, the TMPRSS2-ERG fusion gene has recently been found to be the most frequent gene rearrangement in prostate cancers, occurring in 45-65% of North American patients. Recent reports have demonstrated a strong correlation between the presence of the TMPRSS2-ERG rearrangement and expression of the ERG protein. Other studies have shown a strong concordance of ERG positive prostatic intraepithelial neoplasm (PIN) in ERG positive carcinoma in prostatectomies (with 99.9% specificity). Therefore, as a hallmark of the TMPRSS2-ERG chromosomal translocation, ERG expression offers a rare, but definitive marker of adenocarcinoma of prostatic origin, and a unique opportunity to identify a potentially clinically significant subset of prostate cancer patients by IHC. Given the ease of performing IHC vs. FISH, ERG protein expression in formalin-fixed paraffin-embedded tissue may be an extremely useful tool for the routine identification of the ERG gene rearrangement and diagnosis of prostate adenocarcinoma.
Note: ERG [9FY] was developed by the Center for Prostate Disease Research in association with the Henry M. Jackson Foundation, Rockville, Maryland. U.S. Patent 8,765,916 and patents pending
CK5 is a type II intermediate filament protein that is expressed in active basal layers of most epithelia including normal prostate and normal breast tissues. CK5 stains normal basal cell layers in normal glands, benign glands (Benign Prostatic Hyperplasia, (BPH) and prostatic intraepithelial neoplasia (PIN).
The combination of ERG and CK5 provides a unique stain that identifies the TMPRSS2-ERG chromosomal translocation in prostate cancer (DAB), but also highlights PIN in red; thus helping to visualize ERG positive PINs.