Expression of cell cycle proteins in 4-(methylnitrosamino)-1-(3- pyridyl)-1-butanone-induced mouse lung tumors

Carol L.K. Sabourin, Qian Shu Wang, Sherry L. Ralston, Jason Evans, Jennifer Coate, Christopher R. Herzog, Sandra L. Jones, Christopher M. Weghorst, Gary J. Kelloff, Ronald A. Lubet, Ming You, Gary D. Stoner

Research output: Contribution to journalArticlepeer-review

22 Scopus citations

Abstract

Cyclin D1 dysregulation and differential inactivation of p16(INK4a) and Rb have been observed in human lung cancer. In chemically induced mouse lung tumors, the p16(INK4a) gene is a target of inactivation, and Rb is reduced at the mRNA level (Northern blot) although similar at the protein level (Western blot) when compared to normal lung tissues. The expression of cyclin D1, cdk4, p16(INK4a), and Rb protein was examined by immunohistochemistry in 4- (methytnitrosamino)-1-(3-pyridyl)-1-butanone (NNK)-induced mouse lung tumors. Immunohistochemical staining revealed exclusive nuclear staining of both cyclin D1 and cdk4 that was light to moderate in normal mouse lung tissues, but intense in lung adenomas and adenocarcinomas. Western blot analysis confirmed the increased expression of cyclin D1 and cdk4 in lung tumors compared to normal lung. Immunohistochemical analyses of lung tumors showed focal areas which lacked p16(INK4a) staining. Expression of p16(INK4a), as determined by RT-PCR, was variable in lung tumors. Mutations in p16(INK4a) were not found by SSCP analysis. Immunohistochemical analyses of normal lung tissues showed intense staining for Rb protein in alveolar epithelial cells and in other lung cell types; however, in the lung tumors the staining intensity was reduced and the distribution was altered. Expression of Rb was detected in normal lung tissues but was barely detectable by Northern blot hybridization in lung tumors. Western blot analysis indicated the presence of both hypophosphorylated and hyperphosphorylated Rb protein in lung tumors and in normal lung tissues. These results suggest that alterations in the cell cycle proteins, cyclin D1, cdk4, p16(INK4a), and Rb, may play a role in the acquisition of autonomous growth by adenomas. Furthermore, they demonstrate the importance of immunohistochemical studies to examine expression in tissues that contain multiple cell types, such as the lung, and in tumors that by nature are heterogeneous.

Original languageEnglish (US)
Pages (from-to)499-521
Number of pages23
JournalExperimental Lung Research
Volume24
Issue number4
DOIs
StatePublished - 1998

Keywords

  • Cdk4
  • Cyclin D1
  • Lung
  • Mouse
  • P16(INK4a)
  • Rb
  • Tumor

ASJC Scopus subject areas

  • Molecular Biology
  • Pulmonary and Respiratory Medicine
  • Clinical Biochemistry

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