Molecular characterization of canine prostaglandin G/H synthase-2 and regulation in prostatic adenocarcinoma cells in vitro

An Overview of Current Alternative Models for Use in the Context of Prostate Cancer Research

Prostate cancer is one of the most commonly diagnosed cancers worldwide, particularly in elderly populations. To mitigate the expected increase in prostate cancer-related morbidity and mortality as a result of an expanding aged population, safer and more effective therapeutics are required. To this end, plenty of research is focusing on the mechanisms underlying cancer initiation and development, the metastatic process and on the discovery of new therapies. While animal models are used (mainly rats and mice) for the study of prostate cancer, alternative models and methods are increasingly being considered to replace, or at least reduce, the number of animals used in this particular field of research. In this review, we cover some of the alternative models that are currently available for use in the study of prostate cancer, including: mathematical models; 2-D and 3-D cell cultures; microfluidic devices; the chicken egg chorioallantoic membrane-based model; and zebrafish embryo-based models. The main advantages and limitations, as well as some examples of applications, are given for each type of model. According to our analysis, immortalised cell lines are still the most commonly used models in the field of prostate cancer research. However, the use of alternative models for prostate cancer research will likely become more prevalent in the coming years partly because of the increasing societal pressure to reduce the numbers of laboratory animals. In this context, the development and dissemination of effective non-animal alternative models assumes particular relevance and will be instrumental in leveraging their success. Taking these perspectives into account, we believe that technological advances will lead to more effective cell culture systems, namely 3-D cultures or organ-on-a-chip devices, which can be used to replace animal-based models in prostate cancer research.

CD147 and Cyclooxygenase Expression in Feline Oral Squamous Cell Carcinoma

Feline oral squamous cell carcinoma (OSCC) is a highly invasive form of cancer in cats. In human OSCC, cluster of differentiation 147 (CD147) contributes to inflammation and tumor invasiveness. CD147 is a potential therapeutic target, but the expression of CD147 in feline OSCC has not been examined. Immunohistochemistry was used to determine if cyclooxygenase 2 (COX-2) and CD147 expression in feline OSCC biopsies was coordinated. Tumor cells were more likely to express COX-2 (22/43 cases or 51%) compared to stroma (8/43 or 19%) and adjacent oral epithelium (9/31 cases or 29%) (p < 0.05). CD147 was also more likely to occur in tumor cells compared to stroma and adjacent mucosa, with 21/43 (49%) of cases having >50% tumor cells with mild or moderate CD147 expression, compared to 9/28 (32%) in adjacent epithelium and only 5/43 (12%) in adjacent stroma (p < 0.05). In feline OSCC cell lines (SCCF1, SCCF2, and SCCF3), CD147 gene expression was more consistently expressed compared to COX-2, which was 60-fold higher in SCCF2 cells compared to SCCF1 cells (p < 0.05). CD147 expression did not correlate with COX-2 expression and prostaglandin E2 (PGE2) secretion, indicating that they may be independently regulated. CD147 potentially represents a novel therapeutic target for the treatment of feline OSCC and further study of CD147 is warranted.

Cyclooxygenase-2 Expression in Normal and Neoplastic Canine Mammary Cell Lines

Mammary cancer is the most common cancer in female dogs. Induction of cyclooxygenase-2 (COX-2), a key enzyme in prostaglandins (PGs) biosynthesis, has been demonstrated in various cancers in humans and dogs, including mammary cancer. The objective of this study was to investigate the expression and regulation of COX-2 in canine mammary epithelial cells. Cell lines derived from normal and neoplastic canine mammary glands were cultured in the absence or presence of phorbol 12-myristate 13-acetate (PMA), and immunoblots, immunocytochemistry, radioimmunoassays, and a cell proliferation assay were used to study COX-2 expression and PGs production. Results showed that the neoplastic cell line CMT12 constitutively overexpressed COX-2 protein whereas other mammary cell lines expressed low to undetectable basal levels of COX-2 protein. Basal PGE2 production was significantly higher ( P < .05) in CMT12 compared to other cell lines. Levels of COX-2 protein in CMT12 decreased in a time-dependent manner with serum starvation, and PMA stimulation induced a strong time-dependent increase in COX-2 protein. Treatment of CMT12 cells with NS-398 (a specific COX-2 inhibitor) significantly blocked PGE2 synthesis and reduced cell proliferation ( P < .05). These results indicate that some neoplastic canine mammary cell lines constitutively overexpress COX-2, and that COX-2 inhibition decreases PGE2 production and cell proliferation, supporting a role for COX-2 and PGs in canine mammary oncogenesis.

Cyclooxygenase 1 mRNA expression is undetectable in Madin Darby Canine Kidney cells

Background

Madin Darby Canine Kidney (MDCK) cells form polarized epithelium in vitro and are routinely used in research fields ranging from protein trafficking to influenza. However, the canine origin of these cells also means that compared to man or mouse, genomic resources are more limited and performance of commercially available antibodies often untested. The synthesis of pro-inflammatory prostaglandins in the kidney is mediated by the constitutively expressed cyclooxygenase 1 and the inducible cyclooxygenase 2 (COX-1 and COX-2, respectively). There are conflicting reports on the expression of COX-1 and COX-2 in MDCK cells and this lingering uncertainty about such important pharmacological targets may affect the interpretation of results obtained from this cell line.

Results

In order to definitively settle the issue of cyclooxygenase expression in MDCK cells, we designed PCR primers based on dog genomic sequences to probe COX-1 and COX-2 mRNA expression in MDCK cells and dog kidney. We report that while COX-1 and COX-2 genes are both expressed in dog kidney, COX-1 expression is undetectable in MDCK cells.

Conclusions

By improving the characterization of cyclooxygenase expression in MDCK cells, this study will contribute to a better understanding of the properties of this cell line and lead to improved experimental designs and data interpretations.

Molecular Characterization of Feline COX-2 and Expression in Feline Mammary Carcinomas

Cyclooxygenase-2 (COX-2), the rate-limiting enzyme in the biosynthesis of prostaglandins, plays an important role in inflammation and tumorigenesis. COX-2 primary structure has been characterized in many species and its expression demonstrated in a variety of cancers in humans and dogs, including mammary cancer. In contrast, there is currently little information on the structure of feline COX-2. Also, information on COX-2 expression in feline mammary cancer is limited and conflicting. The objectives of this study were therefore to characterize the molecular structure of feline COX-2 and to evaluate by immunohistochemistry its expression in mammary carcinomas. Our results show that the predicted coding region of feline COX-2 encodes a 604-amino acid protein, which is identical in length to several COX-2 homologs. Feline COX-2 amino acid sequence is highly similar to other mammalian COX-2 homologs. Immunohistochemical analysis of 40 mammary carcinomas showed that the majority of tumors studied (35/40; 87%) expressed COX-2 at a level varying from low (20/40; 50%) to intermediate (13/40; 32%) and high (2/40; 5%). These results provide the first molecular characterization of feline COX-2 and demonstrate that COX-2 is expressed in the majority of feline mammary carcinomas.

An immunohistochemical study of cyclooxygenase-2 expression in various feline neoplasms

Cyclooxygenase (COX) enzymes catalyze the synthesis of prostaglandins and exist as two isoforms, COX-1 and COX-2. COX-2 is a potent inducible mediator of inflammation. COX-2 is also upregulated in several human tumors and in canine squamous cell, renal cell, and transitional cell carcinomas, prostatic adenocarcinoma, and intestinal neoplasia. The purpose of this study was to determine whether COX-2 is expressed in various feline tumors. Results of this study may help determine whether COX-2 is a potential target for therapeutic and preventive strategies in cats. Immunohistochemical studies were performed on paraffin-embedded tissues using the amplified streptavidin-biotin-horseradish peroxidase system. COX-2 was found in 7 of 19 (37%) feline transitional cell carcinomas and in 2 of 21 (9%) feline oral squamous cell carcinomas. No COX-2 immunoreactivity was detected in cutaneous squamous cell carcinomas (6), adenocarcinomas (nine mammary, eight pulmonary, seven intestinal), lymphomas (six nasal, six intestinal), or 10 vaccine-associated sarcomas. The widespread absence of COX-2 expression in most feline neoplasms might suggest that COX-2 inhibitors would have a low potential as anticancer agents.

Lipids and FA analysis of canine prostate tissue

It is widely reported that an association exists between dietary fat intake and the incidence of prostate cancer in humans. To study this association, there is a need for an animal model where prostate carcinogenesis occurs spontaneously. The canine prostate is considered a suitable experimental model for prostate cancer in humans since it is morphologically similar to the human prostate and both humans and dogs have a predisposition to benign and malignant prostate disease. In this study, the FA and lipids profiles of the normal canine prostate tissue from nine dogs were examined. The total lipid content of the canine prostate tissue was 1.7 +/- 0.5% (wet weight). The lipid composition analysis using TLC-FID showed that the two major lipid classes were phospholipids and TAG. Total FA, phospholipid, and TAG FA analysis showed that the major FA were palmitic acid (16:0), stearic acid (18:0), oleic acid (18:1), linoleic acid (18:2n-6), and arachidonic acid (20:4n-6). The n-3 FA were present at <3% of total FA and included alpha-linolenic acid (18:3n-3) (in total and TAG tissue FA), EPA (20:5n-3) (not in TAG), and DHA (22:6n-3) (not in TAG). The n-3/n-6 ratio was 1:11, 1:13, and 1:8 in total, phospholipid, and TAG FA, respectively. This study shows the canine prostate has a low level of n-3 FA and a low n-3/n-6 ratio. This is perhaps due to low n-3 content of the diet of the dogs. FA analysis of dogfoods available in Australia showed that the n-3 content in both supermarket and premium brand dogfoods was <3% (wet weight), and the n-3/n-6 ratio was low.