Effects of testosterone in mouse urinary bladder carcinogenesis

Fig. 3. A Grade-3 invasive bladder carcinoma in Group I. d: Hematoxylin and eosin staining. e: Proliferating cell nuclear antigenpositive cells shown by immunohistochemical staining. f: Some
apoptotic cells shown by terminal-deoxynucleotidyl-transferase(TdT)-mediated dUTP-biotin nick end labeling, × 200.

127

coagulation, but its prognosis isgood. The latter frequently shows
metastasis and has a very poor
prognosis and many problems.
Most of the previous studies reported the sex hormone influenceon urinary bladder carcinogenesis
in the rat model. In all BBN-treated
rat strains, bladder carcinomas areusually papillary, multiple andsuperficial. Thus bladder carcinomas in rats are a satisfactorymodel for studying papillary superficial bladder carcinomas inhumans (Ito et al., 1975). On theother hand, mice whose bladderepithelium has changed to dysplasia, carcinoma in situ and invasive tumor by BBN are goodmodels for human invasive bladder carcinomas (Hirose et al.,1976). Thus, mice were selectedin the present investigation asmodels for invasive bladder carcinomas in humans.
In Experiment I, the occurrence of carcinomas was significantly higher in Group III and significantly lower in Group I than in
the other groups. In ExperimentII, the tumor induction time wassignificantly shorter in Group III
and significantly longer in GroupI than in the other groups. A
previous report showed that both
surgical castration and luteinizing
hormone-releasing hormone agonist treatment significantly
reduced the occurrence of carcinomas as compared with controls;
thus, surgery and ether anesthesia
had little influence on carcinomaoccurrences (Imada et al., 1997).
Similarly, intramuscular injection
was not found to affect inductionof carcinogenesis (Kono et al.,1975). Our findings also showedthat an overdose of testosterone
promotes the occurrence of blad-H. Ohno

der carcinomas in BBN-induced
mice and that suppression of testosterone decreases it.
Previously, the effects of testosterone on bladder carcinogenesis in animal models were considered to suppress the detoxication of BBN, induce a stimulation
pathway for BBN-proximate carcinogen in the liver (Bertram andCraig, 1972) or increase cell
growth in premalignant lesions of
the bladder epithelium (Okajimaet al., 1975). Recently, Imada etal. (1997) demonstrated the existence of androgen receptors on
the bladder epithelium of miceand rats using an immunohistochemical staining. Noronha andRao (1986) also reported that sex
hormone receptors were identified in human advanced transitional cell carcinomas, and dihydrotestosterone and testosterone receptors were found more
frequently than estrogen receptors. Although there is no clear
evidence, testosterone may act on
bladder mucosa and promote
bladder carcinogenesis as it doesin prostate cancer.
Previous studies have shown
significant correlations between
PCNA and histological stages orgrades in human bladder cancer(Waldman et al., 1993; Skopeliouet al., 1997). PCNA expression inrats was also found to gradually
increase as histological stages andgrades advance (Yamashi, 1996).
The present study yielded similar
results, and our findings agreed
significantly with those of theprevious reports. In Group III,Fig. 4. A Grade-3 invasive bladder carcinoma in Group III. g: Hematoxylin and eosin staining. h: Proliferating cell nuclear antigen-positive cells shown by immunohistochemical staining are significantly more
stained than in Group I (Fig. 3e). i: Apoptotic cells are almost equal in quantity to in Group I, shown byterminal-deoxynucleotidyl-transferase (TdT)-mediated dUTP-biotin nick end labeling (Fig. 3f), × 200.

128

Effects of testosterone in mouse urinary bladder carcinogenesis

including bcl-2, c-myc, p53, etc.
among the various models.
This is the first study that indi60
cates a correlation between the effects of testosterone in BBN-induced
40
mouse bladder carcinogenesis andcell proliferation and apoptosis.
20
Among the 3 groups, the proliferationindex of invasive carcinomas wassignificantly higher in Group III and0lower in Group I than in other groups;
020406080(%)
on the other hand, no significant
Proliferation index
difference was observed in apoptoticindex. These results suggest that one
Fig. 5. Correlation between the proliferation index and theof the effects of testosterone in BBNapoptotic index. A significant negative correlation is found (r= – 0.7, P < 0.001, Pearson’s test).
induced mouse bladder carcinogenesis increases cell proliferation rather
than decreasing apoptosis, and that
PCNA showed the highest expression, and in this effect promotes mouse bladder carcinoGroup I, the lowest expression among the 3 genesis.
groups. These findings support that testosHowever, the exact mechanisms by whichterone promotes increased cell proliferation in testosterone promotes bladder carcinogenesis
BBN-induced mouse bladder carcinogenesis.
are not known. Thus, it is necessary to investiApoptosis is one of the most important gate the relationship between testosterone andmolecular mechanisms in the process of car- growth factor production in the process ofcinogenesis. Originally, apoptosis is character- bladder carcinogenesis. In the future, it mightized by a marked reduction in cell volume and be possible to perform a chemoprevention trial
increase in density. Apoptotic bodies are histo- on bladder cancer with hormonal therapy,
logically characterized by their small size, nu- provided that further investigations clarify theclear chromatin condensation, DNA fragmen- mechanisms related to the effects of testostation and compactness of cytoplasmic organel- terone on human bladder carcinogenesis.
les (Kerr et al., 1972, 1994). TUNEL wasintroduced by Gavriel et al. (1992), and shown
to be able to detect apoptosis cells in routine Acknowledgments: The author thanks Prof. Miyagawa
formalin-fixed, paraffin-embedded sections. I, M.D., D.M.Sc., Dept. of Urology, Faculty ofThe extent of apoptosis has been examined in Medicine, Tottori University, for his numerous
several experimental tumor types (Aihara et al., valuable comments and suggestions.
1994; Tatebe et al., 1996). The previous studies
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Received August 20, 2000; accepted September 21, 2000
Corresponding author: Dr. Hirofumi Ohno