Kwang-Hyun Kim

The effect of nitric oxide on cyclooxygenase-2 (COX-2) overexpression in head and neck cancer cell lines.

The overexpression of cyclooxygenase‐2 (COX‐2) and inducible nitric oxide synthase (iNOS) has been previously reported in head and neck squamous cell carcinoma (HNSCC), as well as in many cancers. We hypothesized that endogenous nitric oxide (NO) might increase the expression of COX‐2 in cancer cells. Therefore, we investigated the cross‐talk between NO and the prostaglandin (PG) pathways in HNSCC cell lines. We found that COX‐2 and iNOS expressions were elevated simultaneously. On adding the NO donor, SNAP, the PGE2 level was increased 2–20 times due to increased COX‐2 expression. This increase of COX‐2 expression by SNAP or PMA (potent inducer of both iNOS and COX‐2) was blocked to various degrees by NO scavengers and NOS inhibitors (L‐NAME and 1400W). Also, the expression of COX‐2 in resting cells was inhibited by NOS inhibitors. Moreover, COX‐2 expression, induced by SNAP, was inhibited by ODQ, a soluble guanylate cyclase (sGC) inhibitor. The effect of dibutyryl‐cGMP on COX‐2 expression was similar to that of SNAP. These results imply that endogenous or exogenous NO activates sGC and that the resulting increase of cGMP induces a signaling that upregulates the expression of COX‐2 in HNSCC cell lines. We also observed that NO increased COX‐2 expression in different cancer cell lines, including cervic and gastric cancer cell lines. These findings further support the notion that NO can be associated with carcinogenesis through the upregulation of COX‐2, and that NOS inhibitor may be also useful for cancer prevention.

Nitric oxide upregulates the cyclooxygenase-2 expression through the cAMP-response element in its promoter in several cancer cell lines

We previously showed that nitric oxide (NO) induces overexpression of cyclooxygenase-2 (COX-2) and production of prostaglandin E2 in cancer cells. Here, we investigated the mechanisms by which NO induces COX-2 expression in cancer cells. We found that the cAMP-response element (CRE) is a critical factor in NO-induced COX-2 expression in all cells tested. We found that in cancer cells, three transcription factors (TFs) – cAMP response element-binding protein (CREB), activating transcription factor-2 (ATF-2) and c-jun, bound the CRE in the COX-2 promoter, and their activities were increased by addition of the NO donor, S-nitroso-N-acetyl-D,L-penicillamine (SNAP). NO-induced activation of soluble guanylate cyclase (sGC), p38 and c-Jun NH2-terminal kinase (JNK) upregulated the three TFs, leading to COX-2 overexpression. Addition of dibutyryl-cGMP (db-cGMP) induced COX-2 expression in a manner similar to SNAP; this induction was blocked by a p38 inhibitor (SB202190), but not by a JNK inhibitor (SP600125). NO-induced cGMP was found to activate CREB and ATF-2 in a p38, but not c-jun-dependent manner, while NO induced JNK in a cGMP-independent manner, leading to subsequent activation of c-jun and ATF-2. These results suggest that the low concentrations of endogenous NO present in cancer cell may induce the expression of many genes, including COX-2, which promotes the growth and survival of tumor cells.

The Effects of the Stromal Cell-Derived Cyclooxygenase-2 Metabolite Prostaglandin E2 on the Proliferation of Colon Cancer Cells

It is well known that tumor-surrounding stromal tissues support tumor development through secreting soluble factors such as various cytokines, chemokines, and growth factors. It has also been suggested that tumor-associated fibroblast and immune cells have a high expression of cyclooxygenase-2 (COX-2) and produce and secrete several prostaglandins (PGs) to adjacent cancer tissues. From these findings, we assumed that COX-2 inhibition might have an anticancer effect on cancer cells even without COX-2 expression in COX-2-dependent mechanisms through blocking the effect of stroma-derived PGs. Here, because of the complex involvement of various factors in vivo, we investigated this possibility with an in vivo-mimicking model using a Transwell system. To test our hypothesis, we used COX-2-transfected cell lines as stromal cells in our model. When we cocultured cancer cells (LS174T cells without COX-2 expression) with COX-2-high stromal cells in the Transwell membrane system, we observed that the proliferation of cancer cells was promoted and vascular endothelial growth factor synthesis was up-regulated significantly. These effects were blocked completely by COX-2 inhibitors and phosphoinositide-3-kinase inhibitors and partially by the PG E2 receptor 4 antagonist. Even if some cancer cells did not express COX-2, they were found to have expression of PG receptors and PG-related downstream signaling molecules associated with cell viability. Our observation suggests that these cells can be influenced by PGs derived from stromal tissues. These findings also suggest that COX-2 inhibitors can be used to control the interaction between cancer and surrounding stromal tissues and suppress the proliferation of cancer cells regardless of the expression of COX-2 in cancer cells.

DIFFERENTIAL EFFECTS BETWEEN CYCLOOXYGENASE-2 INHIBITORS AND siRNA ON VASCULAR ENDOTHELIAL GROWTH FACTOR PRODUCTION IN HEAD AND NECK SQUAMOUS CELL CARCINOMA CELL LINES

Several researchers have observed that cyclooxygenase‐2 (COX‐2) inhibitors display anticancer effects only at higher concentrations than doses that block COX‐2 activity in head and neck squamous cell carcinoma (HNSCC) cells.

Celecoxib inhibits cell proliferation through the activation of ERK and p38 MAPK in head and neck squamous cell carcinoma cell lines.

It has been observed that several cyclooxygenase-2 (COX-2) inhibitory chemicals might inhibit proliferation of various cancer cells through COX-2-independent action. We also identified that celecoxib more selectively kills cell lines derived from head and neck squamous cell carcinoma (HNSCC) than its non-cancerous counterparts, irrespective of COX-2 expression. Herein, we investigated whether the regulation of mitogen-activated protein kinases activity might be one of the main mechanisms related to a conspicuous COX-2-independent tumor-killing effect of celecoxib in HNSCC cell lines. We assessed the effect of celecoxib on extracellular signal-regulated kinase (ERK), p38, and c-Jun NH2-terminal kinase activity by a transcription factor activation assay then evaluated, if these factors might be involved in the COX-2-independent tumor-killing effect of celecoxib by blocking their activity. We found that the blocking activation of ERK and/or p38 could reverse the celecoxib-induced cell growth inhibition by 50–80% in HNSCC cell lines, but it was not tested in cancer cells of other types. In conclusion, our study suggests that most COX-2-independent tumor-killing action of celecoxib is mediated by the upregulation of ERK and/or p38 activity in HNSCC cells. These results encourage investigation on the underlying mechanisms and detailed outcomes of mitogen-activated protein kinases activation by celecoxib more concisely, for using its excellent tumor-killing effect more safely in the clinical field of cancer treatment.

Inhibitory effect of p27KIP1 gene transfer on head and neck squamous cell carcinoma cell lines

Although p27 gene mutations are rarely found in cancer, the level of p27 protein expression decreases during tumor development. In several tumors, including laryngeal cancer, decreased expression of p27 is associated with a poor prognosis.

Retrospective Analysis of the Treatment Results for Patients with Squamous Cell Carcinoma of Tonsil

PURPOSEnThere has been no definitive randomized study to identify the optimal therapeutic regimen for treating squamous cell carcinoma of tonsil. The purpose of this study was to retrospectively evaluate the treatment outcome according to various combinations of surgery, radiation therapy and chemotherapy.nnnMATERIALS AND METHODSnFifty-six patients with tonsillar carcinoma, who were treated at Seoul National University Hospital from March 1985 to August 2001, were the subjects of this study. Twenty-one patients received surgery followed by radiation therapy (SRT), 16 patients underwent radiation therapy alone (RT), and 19 patients received neoadjuvant chemotherapy and radiation therapy (CRT). The median radiation dose was 66.6 Gy for the SRT group and 70.2 Gy for the RT and CRT groups. Surgery comprised extended tonsillectomy and modified radical neck dissection of the involved neck. Cisplatin and 5-fluorouracil were used every three weeks for 3 cycles in the SRT group. The median follow-up was 73.2 months.nnnRESULTSnThe distribution of T-stage was 4 cases of T1, 14 cases of T2, 1 case of T3 and 2 cases of T4 staging in the SRT group, 2 cases of T1, 6 cases of T2, 5 cases of T3 and 3 cases of T4 staging in the RT group and 0 cases of T1, 7 cases of T2, 9 cases of T3 and 3 cases of T4 staging in the CRT group. The distribution of N-stage was 5 cases of N0, 2 cases of N1, 13 cases of N2 and 1 case of N3 staging in the SRT group, 6 cases of N0, 5 cases of N1, 5 cases of N2 and 0 cases of N3 staging in the RT group, and 2 cases of N0, and 7 cases of N1, 9 cases of N2 and 1 case of N3 staging in the CRT group. The five-year overall survival rate (OSR) for all patients was 78%. The five-year OSR was 80% for the SRT group, 71% for the RT group, and 80% for the CRT group (p=ns). The five-year disease-free survival rate was 93% for the CRT group and 71% for the RT group (p=0.017). Four patients developed local failure and one patient failed at a regional site in the RT group, and one patient failed at a primary site in the CRT group. The five-year DFS was 84% for patients who had undergone neck dissection and 76% for patients who had not undergone neck dissection (p=ns). Treatment-related complications of grade 3 or 4 occurred in 15 patients, and the incidence of complication was not different between each of the treatment methods.nnnCONCLUSIONnAlthough the patients with more advanced T stage were included in the RT and CRT groups, the OSR was not statistically different according to the treatment methods. In the radical radiation therapy group, the addition of neoadjuvant chemotherapy showed an improvement in the disease-free survival. Because of the retrospective nature of our study and the small number of patients, this study cannot draw any definite conclusions, but it suggests that radiation therapy with chemotherapy can be a good alternative option for squamous cell carcinoma of tonsil. Controlled randomized study is necessary to confirm this hypothesis.