The effect of a selective COX-2 inhibitor, celecoxib, on the proliferation, apoptosis and differential protein expression in nasopharyngeal carcinoma cell lines

Nasopharyngeal carcinoma (NPC) is prevalent in southern China. Although early stage patients have a high rate of cure with radiotherapy alone, the prognosis for those with stage III or IV disease remains poor due to subsequent development of distant metastases. Therefore there is an urgent need to develop novel biologic agents to improve treatment outcomes.;COX-2 over-expression has been found in various cancers such as colorectal cancer, liver cancer and lung cancer. In vivo studies have shown that mice overexpressing COX-2 developed breast cancer whereas COX-2 knockout mice had reduced rates of cancer formation in the intestines and skin. In the present study, COX-2 expression in NPC patient biopsies was examined and correlated with the clinicopathological data of the patients. Immunocytochemical staining showed that COX-2 protein was over-expressed in 84.6% (66/78) of non-metastatic NPC patients and was associated with an advanced nodal stage (P<0.05). All these data support an important role for COX-2 in NPC pathogenesis.;Celecoxib is a COX-2 selective non-steroidal anti-inflammatory drug which has been shown to inhibit growth and induce apoptosis in various cancer cell lines. Using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay and an apoptosis detection kit, we demonstrated that celecoxib was able to induce growth inhibition and apoptosis in a dose-dependent manner in 3 NPC cell lines: HK-1, Hone-1, and C666-1. Afterwards, a proteomic approach was used to study the underlying mechanisms involved in celecoxib-mediated effects on two COX-2 positive NPC cell lines (HK-1 and C666-1). Results showed that a total of 18 protein spots were differentially expressed in the HK-1 and C666-1 cells. On the other hand, we also compared the proteomic expression profile between an NPC cell line (C666-1) and a normal nasopharynx cell line (NP69) in order to study whether those differentially expressed proteins after celecoxib treatment were also involved in NPC carcinogenesis. Proteomics results with confirmation using Western blotting discovered that HSP27 phosphorylated of serine 82 (HSP27-pSer82) protein was up-regulated in C666-1 cells when compared with that in NP69 cells. After treatment with celecoxib, expression of HSP27-pSer82 protein was down-regulated in both HK-1 and C666-1 cells. These findings suggest that down-regulation of HSP27-pSer82 protein expression may have mediated the growth-inhibitory effects of celecoxib in HK-1 and C666-1 cells. Finally, other differential expressed proteins identified from proteomics with confirmation by immunocytochemical staining in the 2 NPC cell lines and 40 NPC patient specimens showed that down-regulation of annexin 2 and beta2-tubulin may be important in NPC formation.;In summary, this study is the first to identify HSP27-pSer82 protein as a potential target of celecoxib in NPC cells. Detailed investigations of the functional role of molecular targets identified in this study would improve our understanding of the chemotherapeutic effects of celecoxib and, in the long run, may lead to a more effective chemotherapeutic treatment to this common cancer.