OBJECTIVETo investigate the expression of two inflammation related enzymes - cyclooxygenase-2 (COX-2) and inducible nitric oxide synthase (iNOS) during the experimental rat lung carcinogenesis.

METHODSEighty Wistar rats were instilled with 3-methylcholanthrene (MCA) and diethylinitrosamine (DEN) into the left lobar branchus to induce lung squamous cell carcinoma. To obtain specimen in every pathological phase during the carcinogenesis, these rats were sacrificed at different intervals. The expression of COX-2 and iNOS in every pathological phase during the carcinogenesis were examined by immunohistochemical method. The immunohistochemical scores (IHS) were calculated by combining an estimate of the percentage of immunoreactive cells with that of the stain intensity.

RESULTS155 specimens of every pathological phase during the carcinogenesis showed: hyperplasia 14, squamous metaplasia 25, dysplasia 33, carcinoma in situ 12, infiltrating carcinoma 54 and metastasis 17. Inflammation and elevated expressions of COX-2 and iNOS were shown in the precancerous lesions. The COX-2 IHS was significantly increased in dysplasia, carcinoma in situ and metastasis (P < 0.01, P < 0.05, P < 0.01 respectively). The iNOS IHS significantly increased in hyperplasia and metastasis (P < 0.05, P < 0.01 respectively). There was a positive correlation between the expression of COX-2 and iNOS (gamma = 0.601 6, P < 0.001).

CONCLUSIONCOX-2 and iNOS, two inflammation related enzymes, playing important roles in the carcinogenesis of MCA and DEN, induce rat lung squamous cell carcinoma as well as its metastasis. The relation between inflammation and carcinogenesis may partly be explained by the elevated expression of these two enzymes. Nonsteroidal antiinflammatory drug (COX-2 inhibitors) and iNOS inhibitors may possess antitumor activities because of their prevention of bronchial dysplasia, carcinogenesis and metastasis.

Animals ; Carcinogens ; adverse effects ; Carcinoma, Squamous Cell ; chemically induced ; enzymology ; pathology ; Cyclooxygenase 2 ; Female ; Immunohistochemistry ; methods ; Isoenzymes ; biosynthesis ; Lung Neoplasms ; chemically induced ; enzymology ; pathology ; Male ; Methylcholanthrene ; adverse effects ; Neoplasms, Experimental ; chemically induced ; enzymology ; pathology ; Nitric Oxide Synthase ; biosynthesis ; Nitric Oxide Synthase Type II ; Prostaglandin-Endoperoxide Synthases ; biosynthesis ; Rats ; Rats, Wistar

OBJECTIVETo investigate the roles of p53 and K-ras gene in carcinogenesis and development of the lung carcinoma induced by 3-methylcholanthrene (MCA) and diethylinitrosamine (DEN) in Wistar rats, and to elucidate the relationships between the protein expression and gene mutation of p53 and K-ras.

METHODSMicrodissection was used to obtain pure cell populations of each phase in the carcinogenesis and development of lung carcinoma induced by MCA and DEN. DNA of the microdissected cell populations was extracted and used to analyze the mutations of p53 exons 5 approximately 8 and K-ras exons 1 approximately 2 by PCR-SSCP. The expressions of p53 and K-ras protein in each phase were detected by immunohistochemistry.

RESULTSNo mutation and protein expression of p53 and K-ras was found in the 30 cases with normal bronchial epithelium. Mutation of p53 was detected in 3.1% of 18 hyperplasia and 14 squamous metaplasia cases, 28.6% of 21 dysplasia, 30.0% of 12 carcinomas in situ, 51.2% of 43 infiltration carcinomas, 52.9% of 17 metastases. The positive immunostaining rate of p53 protein was 0, 42.9%, 50.0%, 60.5% and 64.7% respectively. K-ras mutation rate was 0, 4.8%, 8.3%, 9.3%, 11.8% respectively, while the overexpression rate of K-ras protein was 15.6%, 19.0%, 25.0%, 41.9%, 52.9% respectively. p53 protein expression was closely related with p53 mutation (P < 0.005, Pearson's R = 0.599 6). There was no relationship between the protein expression and gene mutation of K-ras (P > 0.500).

CONCLUSIONSp53 gene mutation and K-ras overexpression were early events in the carcinogenesis and development of rat lung carcinoma induced by MCA and DEN, while K-ras mutation does not play any important role.

Animals ; Genes, p53 ; Genes, ras ; Humans ; Immunohistochemistry ; Lung Neoplasms ; chemically induced ; chemistry ; genetics ; Mice ; Mutation ; Polymerase Chain Reaction ; Polymorphism, Single-Stranded Conformational ; Rats ; Tumor Suppressor Protein p53 ; analysis ; ras Proteins ; analysis