Objective    To investigate dynamic expressions and correlation of cell cycle regulation related proteins

P16

P27 and P53 during the carcinogenesis of chemical-induced lung squamous cell carcinoma in Wistar rats.     Methods    Squamous cell carcinoma of lung was induced by left intra-bronchial instillating with 3-methylcholanthrene (MCA) and diethyinitrosamine (DEN) in iodized oil to 80 Wistar rats. Another 10 Wistar rats receiving intrabronchial instillation of iodized oil served as control. In 15

35

55

65 and 75 d after the instillation

16 rats from experimental group and 2 from the control were sacrificed for HE and SP staining

and Western blotting analysis. SP method was used to examine the expressions of P16

P27 and P53 proteins. Normal tissue

tumor tissue and corresponding adjacent noncancerous tissues were examined by Western blot analysis for the protein expressions of P16

P27 and P53.     Results    A total of 154 specimens at various pathological phases during carcinogenesis were obtained

including 25 hyperplasia

27 squamous metaplasia

37 dysplasia

30 carcinoma in situ and 25 infiltrating carcinoma. The positive rates of P16 and P27 proteins were decreased and the positive rate of P53 protein was increased obviously when the carcinoma developed. The expression of P16 was positively correlated with P27 (P0.01). The expression of P53 was negatively correlated with P16 and P27 (P0.05). The downregulated P16 and P27 expressions

and P53 overexpression were frequently found in lung carcinoma. There was very significant statistical difference between carcinoma and corresponding adjacent noncancerous tissue or normal tissue (P0.01).     Conclusion    The decreased expressions of P16

P27 and increased expression of P53 in the process of carcinogenesis may be associated with the incidence and development of lung squamous cell carcinoma in rats.