Osteopontin expression in nasopharyngeal carcinoma: Its relevance to the clinical stage of the disease

Purpose: To investigate osteopontin (OPN) expression in human nasopharyngeal carcinoma (NPC) and evaluate its clinical significance in the disease.
Materials and Methods: The expression of OPN mRNA in 44 frozen NPC tissue and 15 normal nasopharyngeal epithelium tissue (NNET) samples was examined by semi-quantitative reverse transcriptase polymerase chain reaction (qRT-PCR). OPN protein expression in 67 paraffin-embedded NPC tissue and 21 NNET samples was detected by immunohistochemistry (IHC). In addition, OPN expression was investigated in 12 paired NPC and para-carcinoma tissue (PCT) samples by western blotting (WB). The association between the expression of OPN and the clinicopathologic parameters of NPC was evaluated.
Results: Three different methods all showed that the expression of OPN mRNA or protein in NPC was significantly higher than in NNET or PCT (P = 0.000, 0.001, 0.000, respectively). After an examination by IHC, 88.1% (59/67) of NPC samples showed strong or moderate positive OPN staining and 28.6% (6/21) of NNET samples displayed a weak positive OPN staining. The staining of OPN in tumor cells was mainly localized to the cytoplasm. OPN expression in NPC was not related to patient age or sex (P > 0.05), but was significantly related to tumor size, regional lymph nodal metastasis, and NPC clinical stages (P < 0.05).
Conclusions: Our study demonstrated that OPN mRNA and protein overexpression in NPC may be important in the pathogenesis of the disease. It was strongly related to T stage, N stage and clinical stages of NPC, suggesting that OPN may be involved in NPC metastasis and progression.

Keywords
Metastasis, nasopharyngeal carcinoma, osteopontin, pathogenesis, progression