ABSTRACT. Retinoids are well recognized as promising antitumor agents in humans. However, there have only been a few reports about the effect of retinoids in canine cancers. To investigate the antitumor effect of retinoids on mast cell tumors (MCT), inhibitory effect on cell growth and induction of apoptosis were examined in vitro. Although sensitivity of these cells differed among the cells, the growth of three MCT cell lines (CoMS, CM-MC and VI-MC) were inhibited dose dependently when they were treated with retinoids. FACS analysis of PI-stained nuclei revealed an apoptotic fraction in CM-MC cells about 30% when treated with retinoids, while those of control cells were less than 5%. Caspase-3 activation was observed after retinoid treatment in CM-MC cells. This was confirmed by inhibiting the retinoid-induced apoptosis using the pan-caspase inhibitor, ZVAD-FMK. Both retinoid receptors, RARs and RXRs, were detected by immunoprecipitation followed by western blot analysis in all the three MCT cells. These data suggests that retinoids inhibit the growth of MCTs partly through apoptosis, and this growth inhibition by retinoids may be mediated by RARs and RXRs. We conclude that retinoid may be a potential adjunctive chemotherapeutic agent for the treatment of canine MCT. KEY WORDS: canine, mast cell tumor, retinoid.J. Vet. Med. Sci. 68(8): 797-802, 2006 Mast cell tumors (MCTs) represent the most common cutaneous tumor in the dog, accounting for between 16 to 21% of all cutaneous tumors [28]. Histologic grading, determined by the morphologic characteristics of the neoplastic cells, has been established as the most consistent prognostic factor highly predictive of biological behavior and clinical outcome [19]. The majority of dogs that suffer undifferentiated MCTs carry a poor prognosis [19]. Surgical excision and radiation therapy have been the most successful treatment modality for MCTs described to date, and the use of adjuvant chemotherapy is indicated after the excision of grade 3, metastatic and nonresectable MCTs [23]. However, chemotherapy for canine MCT has been unrewarding, and long-term responses have not been demonstrated in well-controlled clinical trials. Therefore, there is a need for chemotherapy to be improved in order to obtain a better prognosis in undifferentiated MCTs.Retinoids are active metabolites of vitamin A and modulate various biological functions such as cell differentiation, proliferation and embryonic development in vertebrates [11]. It has been well established that retinoidal activities result mainly from the transcriptional regulation of specific gene programs. Retinoids bind to and activate two classes of receptors, retinoic acid receptors (RARs) and retinoid X receptors (RXRs), both of which belong to the steroid/thyroid hormone receptor superfamily [4,13,16,20]. Preclinical and clinical studies suggest that retinoids induce the growth inhibition of various kinds of cancers in human through differentiation and apoptosis. All-trans retinoic acid (ATRA) and 9-cis retinoic acid (9c...

-The present study was conducted to assess involvement of oxidative stress in lung ade-8-hydroxyguanine DNA glycosylase 1 (Ogg1) gene encoding an enzyme that repairs an oxidative DNA injury 8-oxoguanine (8-oxoG). Furthermore, for comparison with the human case, mutations of mouse epidermal growth factor receptor (Egfr) and K-ras genes were examined. The homo-and heterozygously Ogg1 -N-tert-butyl nitrone 0.13% in drinking water, resveratrol 20 ppm in diet, lactoferrin 2% in diet and bilberry powder 2% in diet) or no supplement for 33 weeks.homo-and heterozygous Ogg1 oxoG. All antioxidants tended to inhibit enhanced adeno-carcinogenesis. The Egfr and K-ras gene mutations were detected at sites also found in human lung cancers with low incidences, while the Egfr gene the Ogg1 stress. The presently utilized Ogg1 strategies to control human lung adenocarcinomas, especially in women. Ogg1 Egfr N-Hydroxymethylnitrosamino)-1-(3-pyridyl)-1-butanoneDai Nakae agalennde.dai@nifty.com)

ABSTRACT. Protein expression and subcellular localization of E-cadherin, α-catenin, and β-catenin in 8 feline mammary tumor cell lines were examined by western blot analysis and fluorescence immunocytochemistry. A low E-cadherin expression was observed in FNNm cells. Furthermore, compared to other cell lines, two E-cadherin bands existed in FMC-p1 cells and were localized in the perinuclear region; distinct radial lines were observed in the cytoplasm. A low α-catenin expression was observed in FON-m cells, but there were no apparent abnormalities in its localization. In contrast, similar levels of β-catenin expression and cytoplasmic localization were observed in all cell lines.KEY WORDS: α-and β-catenin, E-cadherin, feline mammary tumor.J. Vet. Med. Sci. 69(8): 831-834, 2007 Cellular adhesion molecules are important for maintaining tissue structure and cell polarity, and are involved in cell movement and proliferation [13]. E-cadherin associates with a group of intracellular proteins termed catenins. α-Catenin serves as a bridge between E-cadherin and β-catenin, both of which connect with the microfilament cytoskeleton [20]. Disruption of normal cell-cell adhesion by alterations in cadherin-catenin molecules may contribute to enhanced migration and proliferation of tumor cells, thereby leading to invasion and metastasis [13].In human and experimental animal models, loss of E-cadherin expression was reported to cause cell migration or metastasis of tumor cells in breast cancers [11], gastric cancers [2], colorectal cancers [9], and prostate cancers [4]. Along with abnormalities of E-cadherin, the relationship between the disruption of the cell adhesion system and α-and β-catenin expressions was also reported in these cancers [7,8,17]. In addition to cell adhesion, β-catenin plays a role in the Wnt signaling cascade that regulates many cellular processes, including cell fate decisions and cell proliferation In cats, mammary tumors are the third common neoplasms, following skin tumors and lymphomas, and account for 12% of all tumors and 17% of the tumors in queens [15]. More than 80% of feline mammary tumors showed considerable malignancy along with rapid progression and metastasis at an early stage [12]. Since feline mammary tumors have malignant properties, investigating their carcinogenesis, tumor progression mechanisms, and the expressions of tumor related molecules is extremely essential. The purpose of this study was to investigate the expression and subcellular localization of E-cadherin, α-catenin, and β-catenin in 8 feline mammary tumor cell lines in order to evaluate the abnormalities of these cell adhesion molecules.In the present study, we used 8 feline mammary tumor cell lines, FKN-p, FMC-p1, FMC-p2, FMC-m, . Of these, 5 were established from a primary lesion, and 3 were established from a metastatic lesion in feline patients bearing spontaneous mammary tumors. Capital letters such as "FKN" indicate identical patients, and small letters such as "p" and "m", indicate primary and metastatic lesions, ...

Retinoids show antitumor effects on human acute promyelocytic leukemia and other tumors via retinoid receptors. In dogs, the role of retinoid receptors in inhibiting tumor development remains unclear. To evaluate the correlation between the degree of expression of retinoic acid receptor alpha (RARalpha) mRNA and the antiproliferative effects of all-trans retinoic acid (ATRA) treatments, expression analysis of RARalpha mRNA and cell growth inhibition assay were performed on 17 established canine tumor cell lines, including 6 mammary gland tumor (MGT) cell lines, 3 osteosarcoma cell lines, 5 melanoma cell lines, and 3 mast cell tumor (MCT) cell lines. Among the cell lines investigated, all 3 MCT cell lines showed high expression of RARalpha, and the most effective cell growth inhibition was observed in ATRA-treated MCT cell lines. However, remarkable antiproliferative effects of ATRA treatments were not observed on other tumor cell lines with moderate or low RARalpha mRNA expression. As a result of the relationship between RARalpha mRNA expression and ATRA treatment with regression analysis, statistically significant correlation was suggested. Furthermore, real-time quantitative polymerase chain reaction analysis of RARalpha was performed on MCT tissue samples of dogs with spontaneous disease, and 5 of 9 tissues showed high expression. These results suggest that ATRA may be an effective antitumor agent for MCT in dogs, and that prior measurement of expression of RARalpha mRNA may be a good indicator of the effectiveness of ATRA treatment.

An aromatic fatty acid, phenylacetate (PA), has been shown to have cytostatic, antitumor and cell differentiation-inducing effects on various kinds of tumors. Previously, we have demonstrated cell growth inhibition, malignant phenotype reduction and cell differentiation effects of sodium phenylacetate (NaPA) treatment in a canine mammary tumor cell line. To clarify the molecular mechanism of these effects, we examined the expression of Ras/MAPK signaling pathway-related molecules in human and canine breast cancer cell lines, and found that the level of c-Raf-1 protein was reduced by 5, 10 and 20 mM of NaPA treatments, though Ras activation was maintained. Dephosphorylation of c-Raf-1 at Serine (Ser) 259, Ser 338, and Ser 621 were also seen in NaPA-treated cells. Downstream factors in the pathway, such as mitogen-activated protein kinase/ERK kinase (MEK)1/2 and ERK1/2, showed decreased activity, and accordingly, expressions of cyclinD1, c-myc, and inactivation of p90 ribosomal S6 kinase (RSK), which are MAPK targets, were reduced. We also observed the reduction of cell-cycle-promoted molecules, such as cdc1/cdk2, cdk4, PCNA cyclin A, and cyclin B, and the increased expression of p27kip1. Furthermore, expression of an epithelial marker, E-cadherin, was increased by NaPA treatment. These results suggest that one of the molecular targets of NaPA treatment was the reduction of c-Raf-1 protein, and that its reduction results in the decrease of malignant characteristics of tumor cells through blockage of the Ras/MAPK signaling pathway.