Sex-Associated Difference in Estrogen Receptor β Expression in N-Methyl-N′-Nitro-N-Nitrosoguanidine-Induced Gastric Cancers in Rats
2011
Wakui, Shin | Motohashi, Masaya | Muto, Tomoko | Takahashi, Hiroyuki | Hano, Hiroshi | Jutabha, Promsuk | Anzai, Naohiko | Wempe, Michael F. | Endou, Hitoshi
Epidemiologic studies indicate that the incidence of gastric cancer is higher in males than in females. Although the mechanisms mediating this difference are unclear, a role for estrogens has been proposed. We used Western blotting to evaluate the role of estrogen receptor (ER) subtypes ERalpha and ERbeta and proliferating cell nuclear antigen (PCNA) in N-methyl-N'-nitro-N-nitrosoguanidine (MNNG)-induced gastric carcinogenesis in Wistar rats; ERalpha and ERbeta mRNA levels also were analyzed by quantitative real-time RT-PCR analysis. The incidence of gastric cancer was significantly higher in male than female rats. In both sexes, ERalpha expression was similar in MNNG-treated cancerous and noncancerous tissues and normal gastric tissue. However, ERbeta expression in MNNG-treated cancerous and noncancerous tissues was significantly lower in male rats and higher in female rats than that in normal gastric tissue; MNNG-induced cancerous tissue showed the highest ERβ expression. PCNA expression in MNNG-treated cancerous tissues was higher than that in noncancerous tissues, and was higher in male rats than female rats. Western blotting results were consistent with the mRNA changes determined by quantitative real-time RT-PCR. The present study provides evidence of a sex-associated difference in ERβ and PCNA expression in MNNG-induced gastric cancers in Wistar rats.
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