Lung cancer develops through a multistage process involving the accumulation of diverse genetic alterations. To gain an understanding of the roles played by tumor suppressor gene proteins and proliferating cell nuclear antigen (PCNA) in chemical carcinogen-induced mouse lung tumorigenesis, we examined the expression of retinoblastoma protein (Rb), p53, and PCNA in normal lung tissues and urethane-induced mouse lung tumors. MATERIALS AND METHODS: ICR mice were given urethane by intra-peritoneal injection, and sacrificed at 5, 13, 21, 31, and 37 weeks following treatment. Sequential morphological changes and the immunohistochemical expression of Rb protein, p53, and (PCNA), during mouse lung tumorigenesis, were examined. RESULTS: During the carcinogenesis, sequential histological changes from hyperplasia of type II pneumocytes, to adenomas, and ultimately to overt adenocarcinomas were noted. Intense nuclear staining of the Rb protein was observed in normal and hyperplastic alveolar epithelial cells and adenomas. In adenocarcinomas, the Rb protein expression was significantly diminished. The p53 mutant protein was not detected in any lesion. The PCNA labeling index increased along with the advance in the histological grade. CONCLUSION: The above results indicate that mouse pulmonary adenocarcinomas develop through premalignant lesions, and down-regulation of the Rb protein expression may be implicated in the urethane-induced mouse lung tumorigenesis. In addition, the PCNA labeling index may reflect the malignant potential during the tumor progression.
Adenocarcinoma ; Adenoma ; Animals ; Carcinogenesis* ; Down-Regulation ; Epithelial Cells ; Genes, Tumor Suppressor ; Hyperplasia ; Lung Neoplasms ; Lung* ; Mice* ; Mice, Inbred ICR ; Mutant Proteins ; Pneumocytes ; Proliferating Cell Nuclear Antigen ; Retinoblastoma Protein* ; Retinoblastoma* ; Urethane*

Histopathology of pulmonary lymphangioleiomyomatosis(LAM) is studied using four new cases and six previously reported cases, which include two cases without definite evidence of LAM. The important diagnostic features of this lesion were nodular proliferation of immature smooth muscle and cleft or cyst formation within the nodules of smooth muscle cells. The nuclei of the smooth muscle cells were bigger than those of blood vessels or fibrotic lung, and the direction of nuclei was irregular. The lung parenchyma showed little inflammatory change but there were multiple air cysts with smooth muscle nodules at their margin. There were two cases with exuberant proliferation of smooth muscle nodules and two cases with papilliferous projections of the cells into lymphatic lumen. Whereas, three cases had only a few small slender nodules of smooth muscle cells at the margin of air cyst. The lymphatic lumen with smooth muscle nodules is dilated in four cases but other four cases show collapsed lumen. Pulmonary hemorrhage and hemosiderosis were prominent in three cases. There were variety of histology in terms of the cellularity of smooth muscle nodules, the size of the lymphatic lumen and the degree of pulmonary destruction, which may have significance on the clinical presentation and prognostication.
Cysts