Rapid CommunicationDecreased Bladder Cancer Growth in Parous Mice
Section snippets
Transgenic Mice
UPII-SV40T transgenic mice, which express SV40T antigen specifically in the urothelium and reliably develop noninvasive BC, were a gift from Drs. Tung-Tien Sun and Xue-Ru Wu of New York University.10 Animals were humanely handled in accordance to institutional and federal guidelines. Male UPII-SV40T transgenic mice were either sham-operated (n = 9) or castrated (n = 8) at 24 weeks of age as previously described.11 Sham operations included all physical manipulations of castration, except the
Results
We analyzed BC volume in mice at 32 weeks of age by noninvasive, contrast-enhanced CT scanning. Contrast dye in the bladder is visible as a positive image in a negative field. Filling defects in the bladder indicate the lumenal protrusion of exophytic BC (arrow, Fig. 1). The filling defects were confirmed as BC via histologic analysis after death: sham-operated males and nulliparous females had large urothelial carcinomas; castrated males had papillary BC; and in multiparous females, urothelial
Comment
As BC incidence in men outnumbers that of women, it would be remiss not to address the hormonal/sex differences involved in BC. Although the transgenic strategy used in the UPII-SV40T transgenic mice does not have sexual bias in BC incidence (all animals—male and female—had BC develop), intact male mice had larger BC volumes develop than did female mice. Castration and pregnancy dramatically alter the hormonal milieu, and castration and parity both appear to have an inhibitory role on the
Conclusions
The results of this study are the first to show that parity affects the growth of BC in rodents, lending itself to becoming a model for studying the effects of pregnancy, parity (age at first litter, number of litters), and nursing (length of time allowed). Future work is necessary to elucidate the role of pregnancy as a protective factor in BC. This could lead to the identification of risk factors, new treatments, or preventive agents for BC.
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Cited by (0)
This study was supported by National Institute of Health grant DK 063126.