Effect of a Cyclooxygenase-2 Inhibitor in Combination with (-)-Epigallocatechin Gallate or Polyphenon E on Cisplatin-Induced Lung Tumorigenesis in A/J Mice.

We investigated the effects of celecoxib combined with (-)-epigallocatechin-3-gallate (EGCG) or polyphenon E in a cisplatin-induced lung tumorigenesis model. Four-week-old female A/J mice were divided into seven groups: (i) Control, (ii) 150 mg/kg celecoxib (150Cel), (iii) 1,500 mg/kg celecoxib (1500Cel), (iv) EGCG+150 mg/kg celecoxib (EGCG+150Cel), (v) EGCG+1,500 mg/kg celecoxib (EGCG+1500Cel), (vi) polyphenon E+150 mg/kg celecoxib (PolyE+150Cel), and (vii) polyphenon E+1,500 mg/kg celecoxib (PolyE+1500Cel). All mice were administered cisplatin (1.62 mg/kg of body weight, i.p.) 1×/week for 10 weeks and sacrificed at week 30; the numbers of tumors on the lung surface were then determined. The tumor incidence and multiplicity (no. of tumors/mouse, mean±SD) were respectively 95% and 2.15±1.50 in Control, 95% and 2.10±1.29 in 150Cel, 86% and 1.67±1.20 in 1500Cel, 71% and 1.38±1.24 in EGCG+150Cel, 67% and 1.29±1.38 in EGCG+1500Cel, 80% and 1.95±1.36 in PolyE+150Cel, and 65% and 1.05±0.10 in PolyE+1500Cel. The combination of high-dose celecoxib with EGCG or polyphenon E significantly reduced multiplicity in cisplatin-induced lung tumors.

Selective cyclooxygenase-2 inhibitor prevents cisplatin-induced tumorigenesis in A/J mice.

Cisplatin is used to treat lung cancer; however, it is also a known carcinogen. Cyclooxygenase-2 (COX-2) inhibitors have been shown to prevent carcinogen-induced experimental tumors. We investigated the effect of a COX-2 inhibitor, celecoxib, on cisplatin-induced lung tumors. One hundred twenty 4-week-old A/J mice were divided into 6 groups: group 1, no treatment; group 2, low-dose celecoxib (150 mg/kg); group 3, high-dose celecoxib (1,500 mg/kg); group 4, cisplatin alone; group 5, cisplatin plus low-dose celecoxib;and group 6, cisplatin plus high-dose celecoxib. Mice in groups 4-6 were administered cisplatin (1.62 mg/kg, i.p.) once a week for 10 weeks between 7 and 16 weeks of age. All mice were sacrificed at week 30. Tumor incidence was 15.8% in group 1, 25% in group 2, 26.3% in group 3, 60% in group 4, 50% in group 5, and 50% in group 6. Tumor multiplicity was 0.2, 0.3, 0.3, 1.3, 1.0, and 0.6 in groups 1-6, respectively. Tumor multiplicity in the cisplatin-treated mice was reduced by celecoxib treatment in a dose-dependent manner (p < 0.05, group 4 vs. group 6). Celecoxib significantly reduced COX-2 expression in cisplatin-induced tumors (p < 0.01, group 4 vs. group 6).

Point mutation of K-ras gene in cisplatin-induced lung tumours in A/J mice.

The risks of secondary lung cancer in patients with early stage non-small and small cell lung cancers are estimated to be 1-2% and 2-10% per patient per year, respectively. Surprisingly, the incidence of second primary cancer in locally advanced non-small cell lung cancer at 10 years, following cisplatin-based chemotherapy with concurrent radiotherapy, increases to 61%. Those patients, on the road to being cured, cannot overlook the possibility of developing a second primary cancer. We developed a second primary lung cancer model using cisplatin as a carcinogen in A/J mice to screen for chemopreventive agents for a second malignancy. In the primary lung tumour model, 4-(methyl-nitrosamino)-1-(3-pyridyl)-1-butanone (NNK), benzo(a)pyrene (BaP), urethane induces specific K-ras mutations in codon 12, codon 12, and codon 61, respectively, in the A/J mice. In this study, we investigated the mechanisms of carcinogenicity by cisplatin in the A/J mice. In the cisplatin-induced tumours, we found no K-ras codon 12 mutation, which is the major mutation induced by NNK or BaP. K-ras gene mutations in codon 13 and codon 61 were found in one tumour (4%) and five tumours (17.8%), respectively. These findings suggest that cisplatin is partially related to K-ras codon 61 mutations, and that the mechanism of carcinogenicity by cisplatin is different from that by NNK or BaP.