title: Sex-associated difference in estrogen receptor β expression in N-methyl-N'-nitro-N-nitrosoguanidine-induced gastric cancers in rats.
abstract: 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  ERα and ERβ and proliferating cell nuclear antigen (PCNA) in N-methyl-N'-nitro-N-nitrosoguanidine (MNNG)-induced gastric carcinogenesis in Wistar rats; ERα and ERβ 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, ERα expression was similar in MNNG-treated cancerous and noncancerous tissues and normal gastric tissue. However, ERβ 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.
authors.affiliation: Department of Toxicology and Biochemistry, Azabu University School of Veterinary Medicine, Kanagawa, Japan; Department of Pathology, The Jikei University School of Medicine, Tokyo, Japan. wakui@azabu-u.ac.jp
authors.forename: Shin
authors.initials: S
authors.lastname: Wakui
authors.forename: Masaya
authors.initials: M
authors.lastname: Motohashi
authors.forename: Tomoko
authors.initials: T
authors.lastname: Muto
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Takahashi
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Hano
authors.forename: Promsuk
authors.initials: P
authors.lastname: Jutabha
authors.forename: Naohiko
authors.initials: N
authors.lastname: Anzai
authors.forename: Michael F
authors.initials: MF
authors.lastname: Wempe
authors.forename: Hitoshi
authors.initials: H
authors.lastname: Endou
mesh_terms: D000818:Animals; D015153:Blotting, Western; D047629:Estrogen Receptor beta / Q000378:metabolism*; D005260:Female; D008297:Male; D008769:Methylnitronitrosoguanidine / Q000633:toxicity*; D018809:Proliferating Cell Nuclear Antigen / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D060888:Real-Time Polymerase Chain Reaction; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012737:Sex Factors; D013274:Stomach Neoplasms / Q000139:chemically induced* / Q000378:metabolism*
chemical_list: D047629:Estrogen Receptor beta; D018809:Proliferating Cell Nuclear Antigen; D008769:Methylnitronitrosoguanidine