Cyclooxygenase-2 Expression In Salivary Adenoid Cystic Carcinoma And Celecoxib Against Salivary Adenoid Cystic Carcinoma Cells In Vitro

INTRODUCTIONSalivary adenoid cystic carcinoma (SACC) is one of the most common malignant tumour of salivary gland origin, representing 10% to 15% of salivary gland malignancies. The clinical behavior of salivary adenoid cystic carcinoma is typical aggressive, such as local recurrence, early distant metastasize after operation. The treatments of choice for salivary adenoid cystic carcinoma were combined therapy including surgical excision, postoperative radiation therapy and chemical therapy. Even though the multidisciplinary treatments, SACC remains an extremely difficult disease to cure.Epidemiological studies suggest that the use of aspirin and other nonsteroid anti-inflammatory drugs (NSAIDs) is associated with a reduced risk of gastrointestinal cancer. In addition, NSAIDs can induce regression of premalignant colorectal polyps in patients with familial adenomatous polyposis, and inhibit carcinogenesis in several rodent models including those of oral cavity cancer. The best known target of NSAIDs is cyclooxygenase (COX), the rate-limiting enzyme in the conversion of arachidonic acid (AA) to prostanoids (PGs), including Cox-1 and Cox-2. Expression of Cox-2 is low or undetectable in most healthy tissues, but can be highly induced in response to cell activation by hormones, proinflammatory cytokines, growth factors, and tumor promoters. Thus, the pathophysiological role of COX-2 has been connected to inflammation and carcinogenesis.MATERIALS AND METHODSImmunohistochemical study. Samples were collected from PLA hospital. SACC specimens were 39. Adjacent normal salivary specimens were 21. COX-2, VEGF and S-100 in samples were detected by immunohistochemical staining method.Cell growth inhibition assay. In SACC-LM and SACC-83, cells were treated with various concentrations of Celecoxib or NS-398 for 24, 48 and 72h. Cell growth inhibition of Celecoxib or NS-398 was determined by MTT (3,4,5-dimethythiazol-2, 5-diphenyltetrazolium bromide) assay to mesure viable cells.Cell Cycle Analysis. In SACC-LM and SACC-83, cells were treated with various concentrations of Celecoxib. Cell cycle was analyzed on a FACS- Calibur flow cytometer.Reverse-transcriptase PCR. In SACC-LM and SACC-83, cells were treated with various concentrations of Celecoxib for different periods. The mRNA expression of COX-2, Bcl-2, bax, VEGF and MMP-2 were measured by RT-PCR.RESULTSCOX-2 Protein was expressed in Human SACC. 11 of 39 SACC specimens expressed positive COX-2 (71.8%) . Only 3 of 21 adjacent normal salivary specimens were COX-2 positive expression( 14.3%). COX-2 expression in SACC tissue was higher than in adjacent normal salivary tissue. At different TNM stage COX-2 positive expression in SACC specimens was different, stage I =90% (9/10) , stageII =71.4% (10/14) , stage III= 71.4% (5/12) , stage IV=50% (5/10) . There was no relationship between the COX-2 results and age, sex, pathological type, the location of the primary tumor, recurrence or distantmetastases. There was no relationship between the COX-2 results and VEGF or S-100 in SACC specimens.The COX-2 selective inhibitor Celecoxib and NS398 inhibited cell growth of SACC lines. As increasing concentrations of Celecoxib, both cell growth of SACC-LM and SACC-83 decreased. For cell growth inhibition of Celecoxib, it was no difference between SACC-LM and SACC-83 with same concentration Celecoxib treatment. As Celecoxib cell growth inhibition, there was no difference at different period. Cell growth of SACC-LM and SACC-83 were more inhibited by Celecoxib than by NS-398.Cell Cycle Analysis. There were no changes in cell cycle progression, in SACC-LM and SACC-83 treated with various concentrations of Celecoxib and for different periods, except that there was cell accumulation before Go/G₁ in SACC-LM line treated with 100μM Celecoxib for 8h.RT-PCR. SACC-LM and SACC-83 treated with Celcecoxib for 72h, as Celcecoxib concentration increasing, level of COX-2 and Bcl-2 mRNA became lower, level of Bax mRNA in both cell lines became higher. There was no change of VEGF and MMP-2 mRNA in both cell lines .CONCLUSIONSSince COX-2 positive expression could be detected in most SACC specimens studied, it may suggest an involvement of COX-2 in SACC carcinogenesis and progression. Since celcecoxib can inhibit cell growth of SACC-LM and SACC-83, COX-2 may serve as a new therapeutic target in SACC. Celecoxib may become a new path to treat SACC.