The mechanisms of antitumor effects of luteinizing hormone-releasing hormone agonist (buserelin) in 7,12-dimethylbenz(a)anthracene-induced rat mammary cancer
Y. Koibuchi et al., The mechanisms of antitumor effects of luteinizing hormone-releasing hormone agonist (buserelin) in 7,12-dimethylbenz(a)anthracene-induced rat mammary cancer, INT J MOL M, 4(2), 1999, pp. 145-148
We evaluated the mechanism of antitumor effects of buserelin, which is one
of LH-RH agonists, on a hormone dependent breast cancer model, using 7,12-d
imethylbenz(a)anthracene (DMBA)-induced rat mammary cancer. Rats developing
solid mammary tumors within 5-7 weeks following the DMBA administration we
re divided into groups weekly, and treated without delay. The tumor bearing
rats were randomized into five groups with regard to tumor size or average
weight (15 rats per group). Each group received one of the following treat
ments during 4 weeks: a) no treatment (NT); b) ovariectomy (Ovx); c) busere
lin; d) Ovx and 17 beta-estradiol (E-2) (Ovx + E-2); e) Ovx + E-2 + buserel
in. Tumor regression immediately began at one week after both buserelin tre
atment and ovariectomy. A significant reduction of tumor size was observed
in both buserelin-treated rats and Ovx rats compared with NT rats (p < 0.01
). No significant difference of tumor size was observed between buserelin-t
reated rats and ovariectomized rats. No reduction of tumor size was observe
d in Ovx + E-2 rats and Ovx + E-2 + buserelin rats. Although the mean uteri
ne wet weight of the buserelin group was significantly higher than that of
the Ovx group, it was significantly lower than that of the NT group. The me
an uterine wet weight of the NT group, the Ovx + E-2 group and the Ovx + E-
2 + buserelin group was similar and was significantly higher than that of ;
the Ovx group. Buserelin did not inhibit exogenous estrogen-dependent tumor
growth in DMBA-induced rat mammary cancers. These results suggest that bus
erelin has no direct effects on DMBA-induced rat mammary cancers, and the m
ain mechanism of action of buserelin for tumor-reduction is due to ovarian
estrogen deficiency.