BACKGROUNDTo study the correlation of cyclin D₁ oncoprotein with a mutated p53 in pulmonary tumors progression.

METHODSThirty-one male A/J strain mice were treated intraperitoneally with a single injection of 20-methylcholanthrene and sacirificed at various ages. A total of 292 lesions in various histological type were obtained. Immunohistochemical methods were employed to detect the expression of cyclin D₁ and p53 in paraffin-embeded tissues.

RESULTSExpression of cyclin D₁ oncoprotein was seen in 6 out of 7 (86%) in hyperplasias, 89 out of 102 (87%) in alveolar adenomas, 41 out of 56 (73%) in papillary adenomas, and 17 of 25 (68%) in papillary carcinomas. Cyclin D₁ expression did not correlate with the progression of the lung neoplasms, and tended to decrease in papillary carcinomas than in papillary adenomas, in alveolar adenomas and hyperplasias (Chi-square=5.531, P=0.033). Expressions of p53 gene were obviously stronger in malignant lesions than in benign lesions (Chi-square=41.77, P=0.000). The p53 showed positive staining in carcinoma and severe atypical cell population. Expression of p53 was seen in 16 out of 40 (40%) in papillary carcinomas, 6 out of 69 (9%) in papillary adenomas, and 4 out of 121 (3%) in alveolar adenoma. No positive p53 stain was observed in hyperplasias. Co-expressive rate of cyclin D₁ and p53 was highest in papillary carcinomas (26%), but did not show in alveolar adenomas and hyperplasias.

CONCLUSIONSCyclin D₁ oncoprotein may play an important role in the oncogenesis of lung neoplasms, especially in the early stage. p53 expression increases significantly as the histological grade advances, and may correlate with the progression of pulmonary tumors and the malignant potential of tumor.