Prediction of poor survival by cyclooxygenase-2 in patients with T4 nasopharyngeal cancer treated by radiation therapy: clinical and in vitro studies.
BACKGROUND
This study was undertaken to determine the status of cyclooxygenase-2 (COX-2) in nasopharyngeal cancer (NPC) in Taiwanese patients and its relationship to survival after radiotherapy (RT). In addition, the effect of NS-398, a potent selective COX-2 inhibitor, was tested in vitro alone and in combination with radiation on NPC-BM1 human NPC cells as a prelude to using this drug along with RT in the treatment of patients with NPC.


METHODS
Thirty-seven patients diagnosed with T4N0-3M0 NPC were enrolled into this study. COX-2 expression was determined by immunohistochemical staining of formalin-fixed, paraffin-embedded tumor tissue. Patient survival was the clinical end point. The effects of COX-2 expression on cell survival and radioresistance was tested in vitro using the selective COX-2 inhibitor NS-398 in conjunction with 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazonium bromide (MTT) and clonogenic assays.


RESULTS
COX-2 immunoreactivity was detected in 62% of NPC tumors, and expression levels were high in 43%. Survival analysis showed the 5-year overall survival rates for patients who had high COX-2 expression was 27% compared with 60% for those with low/absent expression (p = .047). Pattern of failure analysis showed no significant difference between high and low COX-2 expression in locoregional failure (27% vs 25%, p = .91). However, patients with N0 to N1 disease and high COX-2 expression had a significantly higher incidence of distant metastasis compared with patients with stage N0 to N1 disease and low COX-2 expression (83% vs 15%, p = .004). This difference was not observed in patients with N2 to N3 disease. This difference contributed to worse survival of patients whose tumors had high COX-2 expression levels. The selective COX-2 inhibitor NS-398 was directly cytotoxic to NPC-BM1 cells in vitro, as judged in an MTT assay (viable cells decreased from 92% to 76%, 52%, and 22%, with increases of NS-398 from 20 to 40, 60, and 80 microM, respectively). Radiation-induced cell death was also increased by treatment with NS-398. At a 10% survival level, 40 microM NS-398 increased radiation cytotoxicity by a factor of 1.37, whereas 60 microM increased it by a factor of 4.9.


CONCLUSIONS
COX-2 overexpression is a predictor for poor survival for advanced stage NPC. In vitro, NS-398 radiosensitizes the NPC-BM1 cell line, providing a basis for testing the combination of COX-2 inhibitors with radiation in the treatment of patients with NPC.
Chen
Wen-Cheng
WC
Department of Radiation Oncology, Chang Gung Memorial Hospital, Chia-Yi. #6. Chia-Pu Rd., Putz City, Chia-Yi, Hsien, Taiwan.
McBride
William H
WH
Chen
Shih-Ming
SM
Lee
Kam-Fai
KF
Hwang
Tzer-Zen
TZ
Jung
Shih-Ming
SM
Shau
Hungyi
H
Liao
Shuen-Kuei
SK
Hong
Ji-Hong
JH
Chen
Miao-Fen
MF
D000328:Adult; D000368:Aged; D015153:Blotting, Western; D002277:Carcinoma / Q000201:enzymology / Q000473:pathology / Q000532:radiotherapy*; D003131:Combined Modality Therapy; D051546:Cyclooxygenase 2; D052246:Cyclooxygenase 2 Inhibitors; D016861:Cyclooxygenase Inhibitors / Q000494:pharmacology / Q000627:therapeutic use*; D005260:Female; D005562:Formazans / Q000494:pharmacology; D006801:Humans; D007150:Immunohistochemistry; D066298:In Vitro Techniques; D008297:Male; D008565:Membrane Proteins; D008875:Middle Aged; D009303:Nasopharyngeal Neoplasms / Q000201:enzymology / Q000473:pathology / Q000532:radiotherapy*; D009578:Nitrobenzenes / Q000494:pharmacology / Q000627:therapeutic use*; D011379:Prognosis; D011451:Prostaglandin-Endoperoxide Synthases / Q000032:analysis; D011836:Radiation Tolerance; D013449:Sulfonamides / Q000494:pharmacology / Q000627:therapeutic use*; D015996:Survival Rate; D013624:Taiwan; D013778:Tetrazolium Salts / Q000494:pharmacology; D014407:Tumor Cells, Cultured / Q000187:drug effects / Q000528:radiation effects
D052246:Cyclooxygenase 2 Inhibitors; D016861:Cyclooxygenase Inhibitors; D005562:Formazans; D008565:Membrane Proteins; D009578:Nitrobenzenes; D013449:Sulfonamides; D013778:Tetrazolium Salts; C080955:N-(2-cyclohexyloxy-4-nitrophenyl)methanesulfonamide; C079782:MTT formazan; D051546:Cyclooxygenase 2; C496540:PTGS2 protein, human; D011451:Prostaglandin-Endoperoxide Synthases