Seok-Woo Park

Human papillomavirus 16 E5 up-regulates the expression of vascular endothelial growth factor through the activation of epidermal growth factor receptor, MEK/ ERK1,2 and PI3K/Akt

Abstract.The E5 oncoprotein of human papillomavirus (HPV) 16 plays an important role in early cervical carcinogenesis. Vascular endothelial growth factor (VEGF) plays a central role in switching on the angiogenic phenotype during early cervical carcinogenesis. However, the relationship between E5 and VEGF has not previously been examined. To clarify the regulatory role of E5 in VEGF expression, we transferred the E5 gene into various cell types. E5 increased VEGF expression. The addition of epidermal growth factor receptor (EGFR) inhibitor significantly suppressed VEGF expression, demonstrating that E5 stimulates VEGF expression through the activation of EGFR. E5-mediated EGFR activation was accompanied by phosphorylation of Akt and ERK1/2, which are also involved in VEGF expression. Furthermore, the mRNA stability of VEGF was not affected by E5, but VEGF promoter activity could be modulated by inhibitors of the EGFR, MEK-ERK1/2 and PI3K/Akt pathways in E5-expressing cells. Collectively, these novel results suggest that HPV 16 E5 increases VEGF expression by activating EGFR, MEK/ERK1/2 and PI3K/Akt.

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.

Association of CD47 with Natural Killer Cell-Mediated Cytotoxicity of Head-and-Neck Squamous Cell Carcinoma Lines

Objective: Integrin-associated protein (CD47) binds specifically to the inhibitory receptor signal-regulatory protein. This study was designed to evaluate the role of CD47 in natural killer (NK) cell-mediated cytotoxicity against cancer cells. Methods: Head-and-neck squamous cell carcinoma (HNSCC) cell lines were analyzed for the expression of CD47 and susceptibility to NK cell-mediated killing. Cytolytic activity was assessed by 51Cr-specific release assays and by measuring cytokine production. Results: HNSCC cell lines that had high CD47 expression showed lower levels of NK cytotoxicity than those with low CD47 expression. After pre-treating cells with neutralizing major histocompatibility complex (MHC) class I or anti-CD47 antibodies, NK cell-mediated cytotoxicity against HNSCC cell lines increased. In addition, when CD47 cDNA was transfected into Caco-2 cells, NK cell-mediated cytotoxicity decreased. Conclusion: These findings suggest that CD47 may play an inhibitory role in NK cell-mediated cytotoxicity against cancer cells, implying a possible mechanism of immune escape in human cancer.

Celecoxib Can Prevent Tumor Growth and Distant Metastasis in Postoperative Setting

Much evidence suggests that an inflammatory condition provides a microenvironment favorable for tumor growth. One of the main components in the healing wound is the induction of cyclooxygenase-2 (COX-2) and prostaglandins, and many solid tumors have been known to overexpress COX-2. The present study investigated the relationship between surgical wounds and tumor growth and the roles of COX-2 and inflammatory reaction in this microenvironment. We created surgical wounds in syngeneic mice for the implantation of SCC VII murine cancer cell line. Accelerated tumor growth and increased angiogenesis by surgical wounds were clearly observed in C3H/HeJ mice with SCC VII tumor. The COX-2 expression of peritumoral tissues and leukocyte infiltration partly explained the accelerated tumor growth, especially in the early phase after surgical wounding. Celecoxib had a significantly suppressive effect on tumor growth, angiogenesis, and metastasis in tumor-implanted mice with surgical wounds. This tumor-suppressive action of celecoxib did not show any noticeable side effects on the late wound healing and on the gastrointestinal tracts. Prophylactic use of the drug can be advocated in many clinical situations, such as residual tumors or contamination of surgical fields by tumor cells.

Presence of HPV type 6 in dysplasia and carcinoma arising from recurrent respiratory papillomatosis

We collected rare cases of recurrent respiratory papillomatosis (RRP) undergoing malignant transformation. We sought to identify human papillomavirus (HPV) subtypes in areas of papilloma, dysplasia, and carcinoma and investigate thve pattern of protein overexpression.

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.

The shunting of arachidonic acid metabolism to 5-lipoxygenase and cytochrome p450 epoxygenase antagonizes the anti-cancer effect of cyclooxygenase-2 inhibition in head and neck cancer cells.

BackgroundIt has recently been found that 5-lipoxygenase (5-LO) and cytochrome P450-2J2 (CYP2J2), molecules capable of arachidonic acid (AA) metabolism, might promote cancer cell viability through several mechanisms similar to those of cyclooxygenase-2 (COX-2). We found that not only COX-2 expression, but also the expression of 5-LO and CYP2J2 is up-regulated in head and neck squamous cell carcinoma (HNSCC) cell lines. From these observations, we hypothesized that AA metabolism by 5-LO and/or CYP2J2 may lower the efficacy of anti-cancer effect by COX-2 inhibition.Methods and ResultsAlthough COX-2 was highly expressed in all cell lines tested, COX-2-specific inhibition showed little growth-inhibitory effect in some cell lines. Inhibition of COX-2 resulted in increased production of LTB4 and 14-15-DHET/EET, metabolites of 5-LO and CYP2J2, respectively. Combined knock-down of COX-2 and 5-LO or CYP2J2 by siRNA results in a decrease in cell proliferation and VEGF production. Furthermore, these results are dependent on 5-LO and CYP2J2 expression in cells.ConclusionTherefore, combined inhibition of COX-2 and 5-LO or CYP2J2 may be one way to overcome low efficacy of single inhibition of COX-2 in cancer cells. In addition, combined therapies should be chosen based on the expression of members of other AA metabolism pathways.