Antiproliferative B Cell Translocation Gene 2 (BTG2) Protein Is Down-Regulated in Prostate Adenocarcinoma (PAC)
S Lu, K Linos, JS Ross, TA Jennings, B Mian, CE Sheehan, T Nazeer. Albany Medical College, Albany, NY
Background: BTG2 is a p53 inducible antiproliferative gene that, in response to DNA damage or other cell stresses, regulates the G1/S transition of the cell cycle. Expression of BTG2 has been found in benign prostate glands, and increased in atrophic glands. Its role in PAC has not been extensively studied.
Design: Formalin-fixed paraffin-embedded whole-mount radical prostatectomy specimens from 225 patients with PAC were evaluated for BTG2 expression in tumorous, atrophic, and normal benign glands by immunohistochemistry. Slides were stained by automated methods (Ventana Medical Systems, Tucson, AZ) using rabbit anti-human BTG2 polyclonal antibody (sc-33775; Santa Cruz Biotechnology, Santa Cruz, CA). Staining intensity and percentage of positive cells were evaluated in benign, atrophic, and carcinomatous elements. Tumors were scored semi quantitatively based on staining intensity (weak, moderate, and strong) and distribution (focal <25%, regional 25-50%, and diffuse>50%). These results were correlated with Gleason grade and tumor stage.
Results: Most of 225 prostatectomy specimens showed patchy moderate cytoplasmic staining of BTG2 in the benign basal cell layer as well as luminal glandular epithelium. Of the 225 cases, 145 (64.4%) PAC expressed less BTG2 when comparing with adjacent benign prostate acini, 59 (26.2%) with similar expression, while 21 (9.3%) cases had elevated expression in PAC. There was no statistically significant correlation of BTG2 down-regulation among Gleason grade (65.2% in Gleason score 6 or less, vs. 64.8% in Gleason score 7 or more, p = 0.82) or tumor stage (64.8% in T1/T2 vs. 61.1% in T3/T4, p=0.58). Of the atrophic glands, 20 of 49 cases (40.8%) had elevated expression comparing to normal benign glands, 18 (36.7%) with similar intensity, while 11 (22.4%) had decreased expression. PACs expressed significantly less BTG2 when compared with atrophic glands (p<0.0001).
Conclusions: BTG2 expression is significantly less in PAC when compared with atrophic and benign prostate acini. BTG2 down-regulation appears to be an important step in PAC pathogenesis.
Category: Genitourinary (including renal tumors)
Wednesday, March 11, 2009 1:00 PM
Poster Session VI # 119, Wednesday Afternoon