Head and neck tumors show poor response to chemotherapy. One well-known mechanism ofantiwneoplastic drug resistance in human tumor cell is the Multidrug Resistance(MDR) pheonomenon.P-glycoprotein (P-gp) encoded by the MDRI gene is the active effluxpump and plays important roles in MDRphenotype.In this paper

P-gp expression was detected with immunohistochemical assays in 82 untreatedpatients with nasopharyngeal carcinoma and laryngeal cancer. The correlations of P-gp expression to theresponses of chemotherapy and radiotherapy and to the clinical stages of tumor were investigated. Among 82untreated patients with nasopharyngeal carcinoma and larynegal cancer

53.7%(44/82) were P- gp positive50%(23/46) of nasopllaryngeal carcinoma and 55.6%(20/26)of laryngeal cancer had detectable P-gp.The P-gpexpression of 14 patients who received chemotherapy was correlated significantly to the responses ofchemotherapy(P＜0.05)

but no correlations existed between P-gp expression and the response of radiotherapy in26 patients underwent radiotherapy(P＜0.05). There were no correlations of P-gp expression to clinical stages oftumor(P＞0.05). Detection of P-gp expression may be useful in planning chemotherapy regimens for patientswith nasopharyngeal carcinoma or laryngeal cancer.