Cyclooxygenase-2 Expression in Murine and Human Nonmelanoma Skin Cancers: Implications for Therapeutic Approaches¶ (original) (raw)
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Cox-2 gene expression in chemically induced skin papillomas cannot predict subsequent tumor fate
Molecular Oncology, 2010
Elevated cyclooxygenase-2 (COX-2) expression is observed in a variety of premalignant neoplastic tissues, suggesting COX-2 expression might serve as a potential indicator of subsequent tumor development. However, it has not been possible to compare the relationship between Cox-2 gene expression in premalignant lesions and their subsequent fate, because conventional studies require tissue destruction for analysis of gene expression. To monitor COX-2 expression noninvasively during tumor development, we created a Cox-2 luciferase knock-in mouse, Cox-2 luc , in which the firefly luciferase coding region replaces the Cox-2 coding region. Luciferase activity was non-invasively, quantitatively and repeatedly monitored in Cox-2 luc/+ mice subjected to DMBA/TPA multistage skin tumor induction. Luciferase activity is significantly higher in all papillomas than in surrounding skin. However, the magnitude of Cox-2 promoter-driven luciferase activity in small papillomas cannot predict subsequent papilloma regression or growth. Elevated Cox-2 promoter-driven luciferase signal can be detected when papillomas first become visible, but not before this time.
Journal of Cutaneous Pathology
Increased cyclooxygenase-2 (COX-2) expression is thought to support tumorigenesis through various mechanisms and is analyzed as a potential cancer marker. In 18 studies, COX-2 expression in melanocytic lesions of human skin was examined immunohistochemically. However, results obtained by individual research groups differ in terms of detection frequency and level of this protein, as well as localization of stained cells within tumor. Possible reasons for the discrepancies are analyzed in this review: the application of different antibodies, the use of standard histopathological sections or tissue microarrays and the analyzes of staining results based on different algorithms. COX-2 level is significantly lower in nevi than in melanomas, increases gradually with progression of these malignant cancers and reaches the highest values in metastases. These gradual changes in COX-2 expression appear to be difficult to analyze based only on subjective assessment of staining intensity. The most convergent data were obtained using antibodies for N-terminal fragments of COX-2 protein and analyzing results based on calculation of percentage fraction of positive cells. The extent of stained area in specimen thus appears to be more important than the intensity of staining in terms of evaluation of COX-2 performance as a diagnostic and prognostic marker of cutaneous melanoma. K E Y W O R D S cyclooxygenase-2 (COX-2), immunohistochemistry, marker, melanoma, nevus 1 | CYCLOOXYGENASE-2 IN CANCER The cyclooxygenase-2 (COX-2) enzyme converts the arachidonic acid released from membrane phospholipids into prostaglandins in the consecutive reactions of cyclo-oxygenation and peroxidation occurring in two catalytic sites. First, the arachidonic acid is processed to unstable prostaglandin G 2 (PGG 2), which then undergoes reduction to prostaglandin H (PGH 2) that is modified by specific isomerases to other prostanoids. Human COX-2 inducible gene, located in 1q25.2-q25.3 locus, with length of 8.3 kb and 10 exons, encodes a protein containing 604 aa. The COX-2 protein near the N-terminus comprises the epidermal growth factor (EGF-like) domain and the membrane-binding domain, while the central and C-terminal fragments constitute a catalytic domain. 1-4 High COX-2 expression is thought to play an important role in tumorigenesis through various mechanisms modulated by increased production of prostaglandins: stimulation of cell proliferation, inhibition of apoptosis, maintenance of cancer stem cell features, increasing of cell invasiveness, enhancement of angiogenesis and affect on immune system. In turn, the COX-2 peroxidase activity may contribute to production of mutagens (Figure 1). 5-8
Immunohistochemical study of cyclooxygenase-2 and p53 expression in skin tumors
The Journal of dermatology, 2006
Overexpression of cyclooxygenase-2 (COX-2) has been demonstrated in various cancers, including experimentally promoted tumors, gastrointestinal cancers, breast tumors and skin tumors. The mechanism that controls COX-2 expression is not yet clear. Currently, it is reported that COX-2 expression is frequently associated with mutated p53 genes. The goal of this study was to evaluate the expression patterns of COX-2 and p53 in several skin tumors and their correlation. An immunohistochemical method was used to investigate the expression of COX-2 and p53 proteins on formalin-fixed, paraffin-embedded tissue specimens of squamous cell carcinomas (SCC), basal cell carcinomas (BCC), Bowen's disease (BD), actinic keratosis (AK) and porokeratosis. The expression of COX-2 increased in 50% (5/10) of SCC, 80% (8/10) of BCC, 40% (4/10) of BD, 50% (5/10) of AK, and 20% (2/10) of porokeratosis cases. The expression of p53 increased in 90% (9/10) of SCC, 70% (7/10) of BCC, 70% (7/10) of BD, 50% (...
Ultraviolet B (UVB)-Induced COX-2 Expression in Murine Skin: An Immunohistochemical Study
Biochemical and Biophysical Research Communications, 2001
Cyclooxygenase (COX) is the rate-limiting enzyme in the production of prostaglandins from arachidonic acid. This enzyme exists in at least two isoforms, COX-1 and COX-2. COX-1 is constitutively expressed in most tissues and plays various physiological roles. However, COX-2 expression is induced by a variety of agents, which include pro-inflammatory agents and mitogens. Evidence exists to indicate that increased expression of COX-2 occurs in several types of epithelial neoplasms. In this study, we show the effect of chronic exposure of murine skin to carcinogenic UVB on cutaneous COX-2 expression. SKH-1 mice were irradiated with 180 mJ/cm 2 UVB daily for five days a week for periods ranging from 1 to 20 weeks. Nontumor bearing skin areas of irradiated mice, skin of agematched controls and benign papillomas and malignant tumors were assessed immunohistochemically for COX-2 expression in these mice. No epidermal staining occurred in any of the non-UVB-treated controls throughout the experiment. Epidermal COX-2 expression only occurred in UVB-irradiated mice. After 1 and 5 weeks of irradiation, patchy epidermal staining mostly confined to the granular layer and stratum corneum was observed. At week 9, staining intensity had increased, particularly in the granular layer. At week 13, staining was uniformly seen in all epidermal layers with particular prominence in the basal cell layer underlying areas of visible epidermal hyperplasia. It is of interest that the most intense staining was seen in the perinuclear region of keratinocytes and at the plasma membrane. At week 20, COX-2 staining was predominant in the granular layer, although in some tissue sections, the entire epidermis was positive. In benign papillomas, staining was confined to the superficial layers of the epidermis and in squamous cell carcinomas (SCCs), patchy staining in the granular and spinous layers predominated. In general, COX-2 expres-sion was more intense in well-differentiated SCCs than in papillomas. In summary, our results indicate that COX-2 serves as an early marker of epidermal UVB exposure and its expression increases in benign papillomas and in SCCs. These results suggest that pharmacological intervention using specific COX-2 inhibitors could have anticarcinogenic effects in UVBinduced human skin cancer.
Cancer research, 2002
Nonsteroidal anti-inflammatory drugs are widely reported to inhibit carcinogenesis in humans and in rodents. These drugs are believed to act by inhibiting one or both of the known isoforms of cyclooxygenase (COX). However, COX-2, and not COX-1, is the isoform most frequently reported to have a key role in tumor development. Here we report that homozygous deficiency of either COX-1 or COX-2 reduces skin tumorigenesis by 75% in a multistage mouse skin model. Reduced tumorigenesis was observed even though the levels of stable 7,12-dimethylbenz(a)anthracene-DNA adducts were increased about 2-fold in the COX-deficient mice compared with wild-type mice. The premature onset of keratinocyte terminal differentiation appeared to be the cellular event leading to the reduced tumorigenesis because keratin 1 and keratin 10, two keratins that indicate the commitment of keratinocytes to differentiate, were expressed 8-13-fold and 10-20-fold more frequently in epidermal basal cells of the COX-1-defi...
Prostaglandins, Leukotrienes and Essential Fatty Acids, 2002
Increased prostaglandins (PGs) are associated with many inflammatory pathophysiological conditions; and are synthesized from arachidonic acid by either of 2 enzymes, cyclooxygenase-1 (COX-1) or -2 (COX-2). Recent epidemiologic, expression, and pharmacologic studies suggest COX-2 derived metabolites also playa functionalrole in the maintenance of tumor viability, growth and metastasis. Archival and/or prospectively collected human tissues were prepared for immunohistochemistry, and representative cases assayed viaWestern blot, RT-PCR, orTAQman analysis. Consistent overexpression of COX-2 was observed in a broad range of premalignant, malignant, and metastatic human epithelial cancers. COX-2 was detected in ca. 85% of the hyperproliferating, dysplastic, and neoplastic epithelial cells, and in the existing and angiogenic vasculature within and adjacent to hyperplastic/neoplastic lesions.These data collectively imply COX-2 may play an important role during premalignant hyperproliferation, as well as the later stages of invasive carcinoma and metastasis in various human epithelial cancers. &
Carcinogenesis, 1998
Extensive documentation has validated the role of UV irradiation as a tumor initiator and promoter, inducing both squamous and basal cell carcinomas. Human epidermis is a tissue which undergoes active metabolism of arachidonic acid to prostaglandins which is regulated by the action of prostaglandin H synthase (also known as cyclooxygenase). One mechanism for the promotional activity of UV light may involve its ability to induce prostaglandin formation. Work in our laboratory has demonstrated that acute exposure of human keratinocytes to UVB irradiation results in increased production of prostaglandin E 2 (PGE 2 ). When cultured human keratinocytes were examined after irradiation with 30 mJ/cm 2 UVB in vitro, Western blot analysis showed a 6-fold increase in COX-2 protein which was evident at 6 h and peaked 24 h after irradiation. Furthermore, when human subjects were irradiated on sun-protected skin with up to four times their minimal erythema dosage (MED) and biopsied 24 h later, upregulation of COX-2 protein expression was observed via immunofluorescence microscopy. RNAase protection assays supported this observation, showing induction of COX-2 message which peaked at~12 h following irradiation in vitro. Furthermore, human squamous cell carcinoma biopsies exhibited strongly enhanced staining for COX-2 protein via immunohistochemistry and Western analysis when compared to normal non-sun-exposed control skin. Together, these data demonstrate acute upregulation of COX-2 via UVB irradiation and suggest the need for further studies of COX-2 expression as a potential pharmacological target mediating human skin tumor development.
Expression and regulation of cyclooxygenase-2 in normal and neoplastic canine keratinocytes
Veterinary and Comparative Oncology, 2004
Squamous cell carcinoma (SCC) is one of the most common cancers in dogs, yet relatively little is known about the molecular events involved in its development. Increasing evidence implicates cyclooxygenase-2 (COX-2) in the pathogenesis of various cancers in humans and animals. COX-2 overexpression has recently been demonstrated in canine SCCs. The objective of our study was to characterize the expression and regulation of COX-2 in normal and neoplastic canine keratinocytes (CKs) to provide an in vitro system to investigate the implication of COX-2 in SCC oncogenesis in dogs. Cell lines derived from normal CKs and neoplastic CKs (SCCs) were cultured in the absence or presence of agonists, and immunoblots, immunocytochemistry, radioimmunoassays and a cell proliferation assay were used to characterize COX-2 expression and action. Results showed that neoplastic keratinocytes had a higher basal COX-2 expression than normal keratinocytes. In both cell lines, stimulation with the tumour promoter phorbol 12-myristate 13-acetate induced a time-dependent increase in COX-2 protein, with COX-2 induction being stronger in cancerous SCC than in normal CK cells. Moreover, SCC cells produced significantly more PGE 2 than CK cells, under both baseline and stimulated conditions (P < 0.05). NS-398, a selective COX-2 inhibitor, inhibited prostaglandin (PG)E 2 synthesis and decreased proliferation of CK and SCC cells (P < 0.05). Collectively, our results indicate that the canine neoplastic keratinocyte SCC cell line expresses more COX-2 and produces more PGE 2 than the normal keratinocyte CK cell line, thus providing an in vitro system to study the molecular basis of elevated COX-2 expression in SCCs in dogs.
Carcinogenesis
Using a mouse skin tumor model, we reported previously that cyclooxygenase-2 (COX-2) deficiency reduced papilloma formation. However, this model did not differentiate between the effects of systemic COX-2-deficiency and keratinocyte-specific COX-2 deficiency on tumor formation. To determine whether keratinocyte-specific COX-2 deficiency reduced papilloma formation, v-H-ras-transformed COX-2+/+ and COX-2-/- keratinocytes were grafted onto nude mice and tumor development was compared. Transformed COX-2+/+ and COX-2-/- keratinocytes expressed similar levels of H-ras, epidermal growth factor receptor and phospho-extracellular signal-regulated kinase1/2 in vitro; and COX-2-deficiency did not reduce uninfected or v-H-ras infected keratinocyte replication. In contrast, tumors arising from grafted transformed COX-2+/+ and COX-2-/- keratinocytes expressed similar levels of H-ras, but COX-2 deficiency reduced phospho-extracellular signal-regulated kinase 1/2 and epidermal growth factor recept...