Objective:To investigate the expression of Multiple resistance-associated protein-1(MRP1) and P-glycoprotein(P-pg) in oral squamous cell carcinoma(OSCC) before and after neoadjuvant chemotherapy(NACT) and its relation with tumor chemosensitivity and related clinical pathological factors.Methods:The specimens of 106 patients with OSCC before and after NACT were examined by SP immunohistochemistry.The correlation between P-pg and MRP1 expression and therapeutic effect was analyzed.Results:(1)P-pg positive expression rate in OSCC after NACT was 74.53%

which was significantly higher than thatbefore NACT(41.51%)(P﹤0.05);the effective rate of patient with P-pg negative expression before chemotherapy was 56.45%

which was significantly higher than that of patient with P-pg positive expression(34.09%)(P﹤0.05);P-pg expression levels were positively relative to the differentiation of the tumor(P﹤0.05)

but not relative to clinical stages and cervical lymph node metastasis(P﹥0.05);(2)MRP1 positive expression rates in OSCC before and after NACT were 49.06%、and 57.55% respectively and the difference was not significant(P﹥0.05);the effective rates of patient with MRP1 negative expression in OSCC before chemotherapy were 50.00% and 44.23% respectively and the difference was not significant(P﹥0.05);MRP1 expression levels were not relative to clinical stages

differentiation of the tumor or cervical lymph node metastasis(P﹥0.05);Conclusion:P-pg and MRP1 have high expression in primary oral squamous cell carcinoma

but only P-pg expression levels are significantly associated with response to chemotherapy and it can be used as a predictive marker of the sensitivity to chemotherapy in patients with OSCC.