BACKGROUNDTo analyse the relationship between caspase-3 expression and cell proliferation, and to find molecular-biology markers to adjust canceration during rat lung squamous cell carcinogenesis.

METHODSThe 3-methylcholanthrene(MCA) and diethyinitrosamine (DEN) were used to induce lung squamous cell carcinoma by intra-left lobar-bronchial instillation in 50 Wistar rats, and 10 normal rats as controls. Expression of caspase-3 and PCNA were evaluated by immunohistochemistry (IHC).

RESULTSCaspase-3 protein positive rate was 44.12% in 34 rat lung squamous cell carcinomas, and positive coefficient value was 1.38±0.95, which were significantly lower than that of normal bronchial epithelium (P=0.007, P < 0.01) and premalignant lesions (P < 0.05, P < 0.05). The mean PCNA-labeling indexes (PCNA-LI) of normal rat bronchial epithelium, premalignant lesions and lung cancer were 14.10±5.02, 28.13±8.72 and 41.88±14.24 (P < 0.05), respectively. There was a negative correlation between caspase 3 and PCNA LI (r=-0.730 6, P < 0.01).

CONCLUSIONSLoss expression of caspase-3 may promote tumor cell growth, and it may be important in rat lung squamous cell carcinogenesis. Detection of caspase-3 and PCNA proteins can be regarded as major markers in the diagnosis of lung canceration.