C. Tremblay et al., Induction of prostaglandin G/H synthase-2 in a canine model of spontaneousprostatic adenocarcinoma, J NAT CANC, 91(16), 1999, pp. 1398-1403
Background: Prostate cancer is the most frequently occurring cancer in men
in the United States, with an estimated 179300 new cases in 1999, The induc
tion of prostaglandin G/H synthase (PGHS), a key rate-limiting enzyme in pr
ostaglandin biosynthesis, has been implicated in various cancers, most nota
bly in colorectal cancers; however, the induction of PGHS expression in pro
state cancer in vivo has not been reported for any species. The dog is the
only nonhuman species that frequently develops spontaneous cancer of the pr
ostate with increasing age, and the objective of this study was to determin
e whether PGHS isoenzymes were expressed in canine prostatic adenocarcinoma
s. Methods: Four normal canine prostatic tissues and 24 canine prostatic ad
enocarcinomas were studied by means of immunohistochemistry and immunoblot
analysis, using polyclonal antibodies specific for each of the two PGHS iso
enzymes, PGHS-1 and PGHS-2,. All P values were obtained by use of two-sided
Fisher's exact tests. Results: PGHS-1 immunostaining was localized to stro
mal fibroblasts and vascular endothelium in normal and cancerous prostates,
PGHS-2 was not detected in normal prostates, but it was expressed by epith
elial tumor cells in 18 (75%) of the 24 adenocarcinomas (P = .01). Immunobl
ot analysis confirmed the presence of PGHS-1 (69000 molecular weight) in no
rmal and cancerous tissues and the expression of PGHS-2 (72000- to 74000-mo
lecular-weight doublet) only in prostatic adenocarcinomas. Conclusion: To o
ur knowledge, these results demonstrate for the first time that PGHS-2 is i
nduced in the majority of canine spontaneous prostatic adenocarcinomas and
suggest that its expression may be involved in prostate cancer.