Preliminary Study Of P-Glycoprotein Expression, A Multi-Drug Resistance Gene-1 Product, In Patients With Nasopharyngeal Carcinoma Pre-and Post-Radiotherapy

Objective:To investigate preliminarily the expression of p-glycoprotein(pgp),a multi-drug resistance gene 1 product,in the patients with nasopharyngeal carcinoma(NPC) pre- and post-radiotherapy.And to observe the expression of bcl-2 gene and p53 gene proteins and their impact on the patients with NPC.Methods: Between March 2001 and August 2002,64 patients with NPC and 10 controls with chronic nasopharyngeal inflammation were enrolled in the study group.All patients had been histologically proven squamous cell carcinomas and none had received neoadjuvant chemotherapy or radiotherapy. pgp,bcl-2 and p53 were detected by immunohistochemistry pre- radiotherapy.Among them, pgp of 48 patiens with NPC was detected by immunohistochemistry post- radiotherapy .Results: The positive rate of pgp ,bcl-2 and p53 proteins expression in untreated NPC was17.19%(11/64),89.06%(57/64),76.56%(49/64),respectively. Bcl-2 and p53 gene proteins expression were significantly higher in the patients with NPC than those in the controls with chronic nasopharyngeal inflammation.The positive rate of pgp expression post-radiotherapy was 75.00%(36/48),which was significantly higher than that of pgp expression pre-radiotherapy(P<0.001).There was no significantly correlation among the pgp,bcl-2 and p53 proteins expression and age,gender,TNMstaging,but bcl-2 and p53 proteins expression were significantly correlation to cervical lymphonodes metastasis and histologic grade(P=0.01, P=0.01). pgp expression was significantly induced after radiation compared with expression before treatment(P<0.001).Conclusions: pgp expression was significantly induced by radiation in the patients with NPC. This induction of　pgp expression likely confers multidrug resistance to the carcinoma cells and may affect the efficacy of subsequent or concurrent chemotherapy. It may partly explain the lower response to chemotherapy among patients who had previously received radiotherapy. The results of this study support the hypothesis that bcl-2 and p53 genes may be correlations to NPC and they may play an important roles in pathogenesis of NPC.