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Prostate cancer (PC) rarely expresses aberrant immunohistochemical markers such as CK7, CK20, CDX2, GATA3 and TTF1. This study evaluates whether expression of CK7, CK20, CDX2, GATA3 and TTF1 is increased in hormone-resistant (HR) PC compared to hormone-sensitive (HS) disease. 64 patients undergoing transurethral resection of the prostate (TURP) for PC were included: 34 with HS disease, 22 with HR disease, and 8 whose status changed from HS to HR on a subsequent TURP (HS-HR). Overall, CK20 was the most frequently expressed aberrant marker (33.3 % of HS, 60.0 % of HR), followed by CK7 (16.7 % of HS, 13.3 % of HR) and CDX2 (11.9 % of HS, 16.7 % of HR). Compared to HS cases, HR tumors significantly overexpressed CK20 (p = 0.02). Positivity for aberrant markers was usually sparse and heterogeneous within ≤20 % of tumor cells. HR PC was significantly more likely to express aberrant markers among >20 % neoplastic cells than HS tumors (2.4 % and 20.0 % respectively, p = 0.008). The expression of an aberrant marker at >20 % positivity was also associated with loss of expression of ≥1 marker of prostatic origin (PSA, PSMA, P501S or NKX3), p = 0.01. For 21 patients with ≥2 TURPs separated in time, ≥1 aberrant marker was gained over time in 1/7 HS, 2/6 HR and 3/8 HS-HR patients. These results suggest that HR PC has increased likelihood of CK20 positivity and aberrant marker positivity in >20 % of tumor cells compared to HS cases, and that the aberrant immunohistochemical expression in a given PC patient may increase over time.
Wang et al. (Thu,) studied this question.