PURPOSE: Small cell neuroendocrine carcinoma of the prostate is likely to become increasingly common with recent advances in pharmacologic androgen suppression.
Thus, developing molecular markers of small cell differentiation in prostate cancer will be important to guide the diagnosis and therapy of this aggressive tumor.
EXPERIMENTAL DESIGN: We examined the status of RB1, TP53, and PTEN in prostatic small cell and acinar carcinomas via immunohistochemistry (IHC), copy-number alteration analysis, and sequencing of formalin-fixed paraffin-embedded specimens.
RESULTS: We found retinoblastoma (Rb) protein loss in 90% of small cell carcinoma cases (26 of 29) with RB1 allelic loss in 85% of cases (11 of 13). Of acinar tumors occurring concurrently with prostatic small cell carcinoma, 43% (3 of 7) showed Rb protein loss. In contrast, only 7% of primary high-grade acinar carcinomas (10 of 150), 11% of primary acinar carcinomas with neuroendocrine differentiation (4 of 35), and 15% of metastatic castrate-resistant acinar carcinomas (2 of 13) showed Rb protein loss. Loss of PTEN protein was seen in 63% of small cell carcinomas (17 of 27), with 38% (5 of 13) showing allelic loss. By IHC, accumulation of p53 was observed in 56% of small cell carcinomas (14 of 25), with 60% of cases (6 of 10) showing TP53 mutation.
CONCLUSIONS: Loss of RB1 by deletion is a common event in prostatic small cell carcinoma and can be detected by a validated IHC assay. As Rb protein loss rarely occurs in high-grade acinar tumors, these data suggest that Rb loss is a critical event in the development of small cell carcinomas and may be a useful diagnostic and potential therapeutic target.
Tan HL, Sood A, Rahimi HA, Wang W, Gupta N, Hicks J, Mosier S, Gocke CD, Epstein JI, Netto GJ, Liu W, Isaacs WB, De Marzo AM, Lotan TL. Are you the author?
Pathology, Department of Pathology, Henry Ford Health System, Detroit, Michigan; Oncology, and Urology, Johns Hopkins University School of Medicine, Baltimore, Maryland; and Center for Genomics and Personalized Medicine Research, Wake Forest School of Medicine, Winston-Salem, North Carolina.
Reference: Clin Cancer Res. 2014 Jan 27. Epub ahead of print.