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- Author or Editor: Hajime Tsujimoto x
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Abstract
Objective—To evaluate aberrations of the p53 tumor suppressor gene in naturally developing tumors in dogs.
Sample Population—Tumor specimens from 15 dogs with various tumors, including malignant lymphoma (7 dogs), monocytic leukemia (1), mammary gland adenoma (1), mammary gland benign mixed tumor (1), rhabdomyosarcoma (1), colon cancer (1), and osteosarcoma (3).
Procedure—Aberrations of the p53 gene in these tumor tissues were examined by reverse transcriptase- polymerase chain reaction and single-strand conformation polymorphism analysis, using 3 fragments that covered the entire open reading frame of the canine p53 gene, followed by nucleotide sequencing of the abnormal bands.
Results—Point mutations, deletions, and insertions resulting in a number of amino acid substitutions of wild-type p53 were detected in 7 of the 15 tumor specimens from dogs with malignant lymphoma, monocytic leukemia, rhabdomyosarcoma, colon cancer, and osteosarcoma. Of these 7 dogs, 2 had aberrations of the p53 gene on both alleles, whereas 5 had aberrations of the p53 gene on 1 allele and concurrently lacked the wild-type p53 transcript. Many of the aberrations of the p53 gene detected in these tumors were located in the transactivation, DNA binding, and oligomerization domains.
Conclusions and Clinical Relevance—Various naturally developing tumors in dogs often have inactivation of the p53 tumor suppressor gene, which may be 1 of the multiple step-wise genetic changes during tumorigenesis. This study indicates that p53 gene can be a target for gene therapy for tumors in dogs. (Am J Vet Res 2001;62:433–439)
Abstract
OBJECTIVE To examine bile acid composition of gallbladder contents in dogs with gallbladder mucocele and biliary sludge.
ANIMALS 18 dogs with gallbladder mucocele (GBM group), 8 dogs with immobile biliary sludge (i-BS group), 17 dogs with mobile biliary sludge (m-BS group), and 14 healthy dogs (control group).
PROCEDURES Samples of gallbladder contents were obtained by use of percutaneous ultrasound-guided cholecystocentesis or during cholecystectomy or necropsy. Concentrations of 15 bile acids were determined by use of highperformance liquid chromatography, and a bile acid compositional ratio was calculated for each group.
RESULTS Concentrations of most bile acids in the GBM group were significantly lower than those in the control and m-BS groups. Compositional ratio of taurodeoxycholic acid, which is 1 of 3 major bile acids in dogs, was significantly lower in the GBM and i-BS groups, compared with ratios for the control and m-BS groups. The compositional ratio of taurocholic acid was significantly higher and that of taurochenodeoxycholic acid significantly lower in the i-BS group than in the control group.
CONCLUSIONS AND CLINICAL RELEVANCE In this study, concentrations and fractions of bile acids in gallbladder contents were significantly different in dogs with gallbladder mucocele or immobile biliary sludge, compared with results for healthy control dogs. Studies are needed to determine whether changes in bile acid composition are primary or secondary events of gallbladder abnormalities.
Abstract
OBJCTIVE To investigate the effects of dietary lipid overload on bile acid metabolism and gallbladder motility in healthy dogs.
ANIMALS 7 healthy Beagles.
PROCEDURES In a crossover study, dogs were fed a high-fat–high-cholesterol diet (HFCD) or a low-fat diet (LFD) for a period of 2 weeks. After a 4-month washout period, dogs were fed the other diet for 2 weeks. Before and at the end of each feeding period, the concentrations of each of the gallbladder bile acids, cholecystokinin (CCK)-induced gallbladder motility, and bile acid metabolism–related hepatic gene expression were examined in all dogs.
RESULTS The HFCD significantly increased plasma total cholesterol concentrations. The HFCD also increased the concentration of taurochenodeoxycholic acid and decreased the concentration of taurocholic acid in bile and reduced gallbladder contractility, whereas the LFD significantly decreased the concentration of taurodeoxycholic acid in bile. Gene expression analysis revealed significant elevation of cholesterol 7α-hydroxylase mRNA expression after feeding the HFCD for 2 weeks, but the expression of other genes was unchanged.
CONCLUSIONS AND CLINICAL RELEVANCE Feeding the HFCD and LFD for 2 weeks induced changes in gallbladder bile acid composition and gallbladder motility in dogs. In particular, feeding the HFCD caused an increase in plasma total cholesterol concentration, an increase of hydrophobic bile acid concentration in bile, and a decrease in gallbladder sensitivity to CCK. These results suggested that similar bile acid compositional changes and gallbladder hypomotility might be evident in dogs with hyperlipidemia.
Abstract
OBJECTIVE
To examine effects of a common mutation (2-base insertion in exon 5) of the TP53 gene on biological function of p53 protein in canine histiocytic sarcoma cells.
SAMPLE
Canine histiocytic tumor cell lines DH82 with deletion of TP53 and CHS-3 with the wild-type TP53 and canine wild-type and mutant TP53 fragments.
PROCEDURES
Wild-type or mutant TP53 with a polyprotein peptide tag at the N-terminus was transduced into DH82 and CHS-3 cells. Expression of p53 protein, changes in function as a transcription factor, and susceptibility to doxorubicin and nimustine were compared.
RESULTS
Transduced p53 protein was detected in wild-type TP53–transduced DH82 and CHS-3 cells, whereas expression was not detected in mutant TP53–transduced cells. There were significant increases in expression of target genes of p53 protein, including p21 and MDM2, in wild-type TP53–transduced cells, compared with results for native and mock-transfected cells, but not in mutant TP53–transduced cells. There was no significant difference in drug susceptibilities among native and derivative cells of CHS-3. However, cell viabilities of wild-type TP53–transduced DH82 cells incubated with doxorubicin were significantly lower than viabilities of native, mock-transfected, and AT insertion mutation–TP53–transduced DH82 cells; susceptibility to nimustine did not differ significantly among cells.
CONCLUSIONS AND CLINICAL RELEVANCE
Expression of p53 protein and its function as a transcription factor were lost after addition of a 2-base insertion in the TP53 gene in canine histiocytic tumor cells. Additional studies are needed to investigate the clinical relevance of this mutation in histiocytic sarcomas of dogs.
Abstract
Objective—To generate an adenoviral vector that expressed the canine p53 gene and investigate its growth-inhibiting effect on canine osteosarcoma and mammary adenocarcinoma cell lines.
Sample Population—2 canine osteosarcoma cell lines (HOS, OOS) and 3 canine mammary adenocarcinoma cell lines (CHMp, CIPm, and CNMm).
Procedure—An adenoviral vector that expressed the canine p53 gene (AxCA-cp53) was generated. p53 gene expression was examined by use of reverse transcription (RT)-polymerase chain reaction (PCR) assay and immunohistochemistry. Susceptibility of cell lines to the adenoviral vector was determined by infection with an adenoviral vector that expresses β-galactosidase (AxCA-LacZ) and 3-indolyl-β-D-galactopyranoside staining. Growth inhibitory effects were examined by monitoring the numbers of cells after infection with mock (PBS) solution, AxCA-LacZ, or AxCA-cp53. The DNA contents per cell were measured by flow cytometry analysis. Apoptotic DNA fragmentation was detected by use of a terminal deoxynucleotidyl transferase-mediated dUTP nick end-labeling assay.
Results—AxCA-cp53-derived p53 gene mRNA and P53 protein were detected by RT-PCR analysis and immunohistochemistry, respectively. Multiplicity of infection at which 50% of cells had positive 3-indolyl- β-D-galactopyranoside staining results ranged from 10 to 50. AxCA-cp53 induced growth inhibition in a dosedependent manner. Arrest of the G1-phase population and apoptotic DNA fragmentation were observed in cells infected with AxCA-cp53.
Conclusions and Clinical Relevance—AxCA-cp53 inhibits cell growth via induction of cell cycle arrest and apoptosis in canine osteosarcoma and mammary adenocarcinoma cell lines that lack a functional p53 gene. AxCA-cp53 may be useful to target the p53 gene in the treatment of dogs with tumors. (Am J Vet Res 2003;64:880–888)
Abstract
OBJECTIVE To investigate effects of prednisolone administration on gallbladder emptying rate and gallbladder bile composition in dogs.
ANIMALS 6 healthy Beagles.
PROCEDURES Prednisolone was administered (2 mg/kg, SC, once daily for 2 weeks) to each dog and tapered over 2 weeks. Gallbladder emptying rate and bile composition were evaluated before and after administration of prednisolone for 2 weeks as well as 1 week after cessation of prednisolone administration.
RESULTS Gallbladder emptying rate decreased significantly after prednisolone administration (median, 27%; range, 0% to 38%), compared with rate before administration (median, 59%; range, 29% to 68%), but then increased 1 week after cessation of administration (median, 45%; range, 23% to 48%). Gallbladder bile mucin concentration decreased significantly after prednisolone administration (median, 8.8 mg/dL; range, 6.2 to 11.3 mg/dL), compared with concentration before administration (median, 13.1 mg/dL; range, 10.7 to 21.7 mg/dL), but then increased 1 week after cessation of administration (median, 14.3 mg/dL; range, 9.6 to 26.7 mg/dL). Gallbladder taurochenodeoxycholic acid concentration decreased significantly after prednisolone administration (8.1 mmol/L; range, 6.8 to 15.2 mmol/L), compared with concentration before administration (median, 27.2 mmol/L; range, 22.0 to 31.9 mmol/L), but then increased 1 week after cessation of administration (median, 26.4 mmol/L; range, 15.1 to 31.5 mmol/L).
CONCLUSIONS AND CLINICAL RELEVANCE A lower gallbladder emptying rate caused by prednisolone administration may be involved in the pathogenesis of gallbladder disease in dogs. Further studies are required to determine the clinical importance of lower gallbladder bile mucin concentrations caused by glucocorticoid administration in the pathogenesis of gallbladder disease in dogs.
Abstract
Objective—To examine the DNA methylation status of the ABCB1 gene in tumor cells of dogs with lymphoma.
Animals—27 dogs with multicentric B-cell high-grade lymphoma (19 chemotherapy-sensitive dogs and 8 chemotherapy-resistant dogs).
Procedures—The DNA methylation profile of the CpG island of the ABCB1 gene was analyzed by use of bisulphite sequencing and real-time methylation-specific PCR assay in lymphoma cells. Quantitative reverse transcriptase PCR assay of the ABCB1 gene was conducted to measure the amount of mRNA. Correlation between the amount of ABCB1 mRNA and the methylation rate was examined.
Results—The CpG island of the ABCB1 gene was hypomethylated in most dogs in both the chemotherapy-sensitive and -resistant groups. No significant difference was detected in the methylation rate between the 2 groups, and no significant correlation was detected between the methylation rate and the mRNA expression level.
Conclusions and Clinical Relevance—Expression of the ABCB1 gene was not suppressed by hypermethylation of its CpG island in most dogs with lymphoma regardless of their chemotherapy sensitivity status.
Abstract
Objective—To induce chemoresistance in a normal canine cell line through the transduction of the canine multidrug resistance 1 gene (mdr1).
Sample Population—Madin-Darby canine kidney (MDCK) epithelial cell line.
Procedures—The full-length canine mdr1 cDNA clone isolated in our laboratory was inserted into a Moloney murine leukemia virus–based vector to construct the retroviral vector, pLNC-cMDR1. After retroviral transduction of pLNC-cMDR1 into MDCK cells, the expression and function of the P-glycoprotein, a product of mdr1, were assessed by immunoblotting, measurement of rhodamine123 (Rh123) retention, and drug sensitivity assays.
Results—P-glycoprotein was strongly expressed in cells transduced with pLNC-cMDR1. This P-glycoprotein was fully functional, as demonstrated by the decreased Rh123 retention and the increased resistance to chemotherapeutic drugs. Measured as 50% inhibitory concentrations, resistance increased 59 times to vincristine and 25 times to doxorubicin in MDCK cells after transduction of pLNC-cMDR1.
Conclusions and Clinical Relevance—Transduction of canine mdr1 is an effective method for inducing chemoresistance in normal canine cells. This system may be applicable to the induction of drug resistance in hematopoietic cells.
Abstract
Objective—To evaluate the mechanism of multidrug resistance in feline lymphoma cell lines.
Sample Population—A feline lymphoma cell line (FT-1) and its adriamycin (ADM)-resistant subline (FT-1/ADM).
Procedures—The FT-1 cell line was cultivated in the presence of a gradually increasing concentration of ADM to generate its ADM-resistant subline (FT-1/ADM). Susceptibility of cells from the parental FT-1 cell line and the FT-1/ADM subline to antineoplastic drugs was determined. From the complementary DNA (cDNA) template of FT-1/ADM cells, feline MDR1 cDNA was amplified by use of polymerase chain reaction (PCR) and sequenced. Reverse transcription (RT)-PCR and Western blot analyses were performed to assess expression of the MDR1 gene and P-glycoprotein (P-gp) in FT-1/ADM cells, compared with that in FT-1 cells.
Results—A drug sensitivity assay revealed that FT-1/ADM cells were much more resistant to ADM and vincristine than the parental FT-1 cells. The feline MDR1 cDNA amplified by use of PCR was 3,489 base pairs long, corresponding to approximately 90% of the whole open reading frame of human MDR1 cDNA; its amino acid sequence was 91.5, 87.0, and 79.4% identical to that of human MDR1, mouse mdr1a, and mdr1b cDNA, respectively. By RT-PCR analysis, expression of MDR1 messenger RNA was clearly detected in FT-1/ADM cells but not in the parental FT-1 cells. Western blot analysis also revealed the expression of P-gp encoded by the MDR1 gene in FT-1/ADM cells but not in FT-1 cells.
Conclusions—The basic structure of the feline MDR1 gene was essentially the same as that of multidrug- resistance genes of other species. Expression of P-gp appeared to be one of the mechanisms responsible for the development of multidrug resistance in feline lymphoma cell lines in vitro. (Am J Vet Res 2000;61:1122–1127)
Abstract
Objective—To perform molecular cloning of the canine telomerase reverse transcriptase (TERT) gene and determine its expression in neoplastic and nonneoplastic cells.
Sample Population—9 canine tumor cell lines derived from various neoplasms, 16 primary canine tumors, and tissues from 15 normal canine organs.
Procedure—Tumor cell lines were derived from canine tumors that included osteosarcoma, mammary gland adenocarcinoma, melanoma, acute lymphoblastic leukemia, lymphoma, and mastocytoma and a canine primary fibroblast culture. Canine TERT complementary DNA (cDNA) was amplified by use of polymerase chain reaction (PCR) and sequenced. Expression of TERT mRNA was examined by reverse transcription (RT)-PCR assay. Telomerase activity was measured by use of the telomeric repeat amplification protocol assay.
Results—The canine TERT cDNA clone was 237 base pairs in length and contained a central region encoding the reverse transcriptase motif 2. Expression of TERT mRNA was detected in canine tumor cell lines that had telomerase activity but not in telomerasenegative canine primary fibroblasts. The TERT mRNA was detected in 13 of 16 canine tumor tissues and several normal tissues such as liver, ovary, lymph node, and thymus. A significant correlation between TERT expression level and telomerase activity was noted.
Conclusions and Clinical Relevance—Expression of TERT mRNA was closely associated with telomerase activity in neoplastic cells as well as some non-neoplastic cells from dogs. In addition to telomerase activity, expression of TERT mRNA can be used as a marker of tumor cells. (Am J Vet Res 2003;64:1395–1400)