Methods and Findings in Experimental and Clinical Pharmacology 1997-05-01

Bropirimine as neoadjuvant therapy decreases residual disease and expression of markers PCNA and TGF-beta 1 in a rat orthotopic prostate adenocarcinoma.

G Lievano, D Di Domenico, J Brown, P Bridges, M Rubenstein, M Shaw, P Guinan

Index: Methods Find. Exp. Clin. Pharmacol. 19(4) , 261-7, (1997)

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Abstract

The role of bropirimine in prostate cancer remains unexplored. To address the efficacy of this immune modulator as neoadjuvant therapy we utilized the orthotopic placement of the Dunning AT-3 tumor. 2.4-2.6 x 10(6) Dunning AT-3 cells were injected into the ventral prostates of 50 Copenhagen X Fischer rats. Animals were then divided into 5 groups consisting of: 1) untreated controls; 2) those treated with ventral prostatectomy alone (performed 10-12 days following tumor cell inoculation); 3) those treated with ventral prostatectomy plus bropirimine (10 mg/kg) on postimplantation days 1, 3, 5, 10 and 11; 4) those treated with ventral prostatectomy plus bropirimine (100 mg/kg), at the same schedule; and 5) those treated with ventral prostatectomy plus bropirimine (500 mg/kg), at the same schedule. Animals were sacrificed 10 days after prostatectomy, autopsied, and residual disease was weighed. Prostate weights upon removal following neoadjuvant treatment and residual disease remaining after 20-22 days were expressed in grams (g). Following prostatectomy, mean prostate weights were: Group 2, 0.67 +/- 0.11; Group 3, 0.53 +/- 0.11; Group 4, 0.54 +/- 0.12; Group 5, 0.44 +/- 0.09. The effect of bropirimine was significant (p = 0.0001) by multiple regression analysis. In addition, mean residual tumor weights (expressed in grams) after 20-22 days were: Group 1, 12.7 +/- 1.9; Group 2, 6.7 +/- 4.8; Group 3, 5.2 +/- 5.9; Group 4, 3.8 +/- 3.5; and Group 5, 2.8 +/- 3.5. The effect of bropirimine was not significant (p = 0.07) by multiple regression analysis. However, prostatectomy alone, by Student's test, significantly (p = 0.04) reduced residual mean tumor weights by 47% and the additional effect of bropirimine upon residual disease was significant (p = 0.038) if a Chi-square analysis is applied. Finally, a multivariate analysis of the overall effect of bropirimine in rats treated with prostatectomy was significant (p = 0.002). The effect of bropirimine on expression of proliferating cell nuclear antigen (PCNA) and transforming growth factor beta 1 (TGF-beta 1) was also evaluated immunohistochemically and expression of both tumor markers was significantly reduced (p < 0.05). We conclude that bropirimine may have a role as a neoadjuvant therapy when combined with prostatectomy.