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

Abstract：

:Cyclin D1 dysregulation and differential inactivation of p16INK4a and Rb have been observed in human lung cancer. In chemically induced mouse lung tumors, the p16INK4a 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, p16INK4a, and Rb protein was examined by immunohistochemistry in 4-(methylnitrosamino)-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 p16INK4a staining. Expression of p16INK4a, as determined by RT-PCR, was variable in lung tumors. Mutations in p16INK4a 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, p16INK4a, 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.

journal_name

Exp Lung Res

journal_title

Experimental lung research

authors

Sabourin CL,Wang QS,Ralston SL,Evans J,Coate J,Herzog CR,Jones SL,Weghorst CM,Kelloff GJ,Lubet RA,You M,Stoner GD

doi

10.3109/01902149809087383

subject

Has Abstract

pub_date

1998-07-01 00:00:00

pages

499-521

issue

eissn

0190-2148

issn

1521-0499

journal_volume

pub_type

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