title: P21 and CEA expression and AgNOR counts in dimethylhydrazine-induced colon carcinoma in rats.
abstract: OBJECTIVE
  To study P21 and carcinoembryonic antigen (CEA) expression and to measure argyrophilic nucleolar organizer region (AgNOR) counts in various lesions of colonic mucosa and the mechanism of carcinogenesis.
  
  
  METHODS
  Thirty-eight male Wistar rats were injected with dimethylhydrazine (DMH) once a week for 25 wk. P21 and CEA expression was detected by immunohistochemical methods, and AgNOR was counted by silver staining paraffin sections from various colonic lesions.
  
  
  RESULTS
  The incidence of colonic carcinoma in DMH-treated rats was 71.05% (27/38), and lymph node metastasis occurred in six rats. Immunohistochemical studies showed that P21 was primarily expressed in dysplasia and carcinomas, while CEA was expressed in carcinomas and metastatic tumors. AgNOR counts were higher in dysplasia and carcinomas. There were significant differences in P21 and CEA expression between benign and malignant lesions (P < 0.05). The difference in AgNOR counts was also significant between normal and dysplastic tissues, and between dysplasia and malignant lesions (P < 0.05).
  
  
  CONCLUSIONS
  Dysplasia is a premalignant change of colonic carcinoma. The detection of P21 via immunohistochemistry and AgNOR counting may be an important clinical screening technique for colon carcinoma and premalignant lesions.
authors.affiliation: Zhi-Gang Zhang, Da-Kun Gu, Fang-Fang, Department of Pathology, Shanghai Medical College for Health Staff.
authors.forename: Z G
authors.initials: ZG
authors.lastname: Zhang
authors.affiliation: Zhi-Gang Zhang, Da-Kun Gu, Fang-Fang, Department of Pathology, Shanghai Medical College for Health Staff.
authors.forename: J Y
authors.initials: JY
authors.lastname: Wu
authors.affiliation: Zhi-Gang Zhang, Da-Kun Gu, Fang-Fang, Department of Pathology, Shanghai Medical College for Health Staff.
authors.forename: X D
authors.initials: XD
authors.lastname: Fu
authors.affiliation: Zhi-Gang Zhang, Da-Kun Gu, Fang-Fang, Department of Pathology, Shanghai Medical College for Health Staff.
authors.forename: D K
authors.initials: DK
authors.lastname: Gu
authors.affiliation: Zhi-Gang Zhang, Da-Kun Gu, Fang-Fang, Department of Pathology, Shanghai Medical College for Health Staff.
authors.forename: F
authors.initials: F
authors.lastname: Fang
keywords: Carcinoembryonic antigen; Colonic neoplasms; Nucleolus organizer region; P21 oncogene; Ras oncogene