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H Tsuda

Publications and source records attributed to H Tsuda.

At least 91 records · Page 5Linked to original sources
PubMed2000

A quantitative model using mean and standard deviation for evaluation of interobserver agreement in nuclear atypia scoring of breast carcinomas in a protocol study.

A quantitative model was devised for the purpose of evaluating interobserver agreement in the judgment of the nuclear atypia score of cancer cells in protocol studies. In this model, the mean nuclear atypia score (mu) among observers was considered to approximate the 'true' nuclear atypia score of the tumor, and with an identical mu the strength of interobserver agreement was evaluated by the difference between the ideal standard deviation (sigma) and the observed sigma in the slide conference session. This model was applied to the data of a total of 216 invasive ductal carcinomas acquired at eight slide conference sessions held for the standardization of nuclear atypia scoring and monitoring of interobserver agreement level for enrolled cases in a surgical adjuvant protocol on breast cancer. Compared with conventional percentage interobserver agreement and kappa statistics, the present model, named the lambda model, was more sensitive in detecting the improvement of interobserver agreement in nuclear atypia scoring with repetition of slide conference sessions. The lambda model was particularly effective for evaluating the session which included many intermediate cases with a score between 1 and 2 or between 2 and 3. Percentage interobserver agreement and kappa statistics could estimate the agreement irrespective of the number of observers, but the agreement tended to be underestimated when these intermediate cases were in the majority. The present method was considered to be complementary to conventional methods for evaluating interobserver agreement of cancer histology in protocol studies.

Breast Neoplasms↗
PubMed2000

New prognostic histological parameter of invasive ductal carcinoma of the breast: clinicopathological significance of fibrotic focus.

Immunohistochemistry, DNA ploidy analysis and molecular genetics have made it possible to predict the outcome of breast cancer more precisely than routine histological examination alone. However, in routine practice, it is difficult to incorporate these methodologies in all cases. If certain histological parameters can accurately predict the outcome of patients with breast cancer, they would be more practical for routine use. We showed that the presence of fibrotic focus (FF) in invasive ductal carcinoma (IDC) is closely associated with c-erbB-2 or p53 protein expression, high proliferative activity, and high angiogenesis of the tumors. Furthermore, multivariate analyses with well-known prognostic parameters for IDC demonstrated that the presence of FF is the most useful independent parameter to predict IDC patient outcome. In addition, our data suggested that the interaction between tumor cells and stromal fibroblasts may play an important role in the formation of FF in IDC based on growth factor and growth factor receptor protein expression in the tumor cells and fibroblasts forming FF. Based on the results of our clinicopathological studies, we propose a new prognostic classification scheme for the prediction of IDC patient outcome, which consists of FF, nuclear atypia, and fat invasion. This classification has superior predicting power to existing prognostic classifications.

Breast Neoplasms↗
PubMed2000

The role of p16-cyclin d/CDK-pRb pathway in the tumorigenesis of endometrioid-type endometrial carcinoma.

We analysed p16 gene alteration and p16, cyclin-dependent kinase 4 (CDK4), CDK6, cyclin D1, cyclin D2, cyclin D3 and retinoblastoma protein (pRb) expression in ten normal endometriums (PE), 18 endometrial hyperplasias (EH) and 35 endometrial cancers (EC). Two of ten PE (20%), nine of 18 EH (50.0%) and 29 of 35 EC (82.9%) exhibited p16 nuclear staining. p16 expression was significantly higher in EC than EH (P = 0.0119). In the six p16 (-) EC, one was considered to have reduced gene dosage consistent with possible homozygous deletion of the CDKN2 gene and three had methylation in 5'CpG island in the promoter region of the p16 gene, whereas none showed such reduced gene dosage and four had methylation in the nine p16 (-) EH. Strong CDK4 staining was observed in 12 of 35 EC (34.3%) and one of 18 EH (5.6%). The strong expression of CDK4 was higher in EC than in EH (P = 0.0399). The expression of CDK4 was higher in EH than PE (P = 0.0054). The abnormalities of p16-cyclin D/CDK-pRb pathway were detected in 18 of 35 EC (51.4%). In conclusion, the expression of p16 and CDK4 may be an early event in the neoplastic transformation of endometrial cancer.

Base Sequence↗
PubMed2000

Transgenic rats carrying human c-Ha-ras proto-oncogenes are highly susceptible to N-methyl-N-nitrosourea mammary carcinogenesis.

A rat line carrying three copies of the human c-Ha-ras proto-oncogene, including its own promoter region, was established and designated Hras128. Expression of the transgene was detected in all organs examined from Hras128 rats by northern blot analysis. To examine its influence on susceptibility to N-methyl-N-nitrosourea (MNU)-induced mammary carcinogenesis, female rats were treated with 50 mg/kg MNU i.v. at 50 days of age. All 22 Hras128 transgenic rats rapidly developed multiple and large mammary carcinomas within as little as 8 weeks after MNU treatment (14.1 tumors/rat, average diameter 16.4 mm). In contrast, 24 non-transgenic littermates developed no or only small tumors (0.46 tumors/rat, average diameter 7.4 mm) within this period. PCR-restriction fragment length polymorphism (RFLP) analysis and direct sequencing for the transduced human c-Ha-ras proto-oncogene indicated that 38 out of 44 tumors (86.4%) contained cells with mutations at codon 12 in exon 1. However, the signal densities of the mutated bands observed in the RFLP analyses revealed the presence of mixed populations of mutated and non-mutated cells in the tumors, the latter being in the majority. PCR-single strand conformation polymorphism analysis detected no mutations in codons 12 or 61 of the endogenous rat c-Ha-ras gene of Hras128 rat tumors. The results thus indicate that rats carrying the transduced human c-Ha-ras proto-oncogene are highly susceptible to MNU-induced mammary carcinogenesis and that this is not primarily due to mutations of the transgene or endogenous c-Ha-ras gene.

Animals↗
PubMed2000

Atypical medullary carcinoma of the breast with cartilaginous metaplasia in a patient with a BRCA1 germline mutation.

We examined a 34-year-old premenopausal woman who had noticed a left-breast lump a month previously. She had no past history of malignancies but had a family history of breast and ovarian cancers. Her mother had suffered from ovarian cancer when aged 47 years and had died of the disease at age 52. The younger two of the patient's four aunts had developed breast cancer when they were 37 and 48 years old. A physical examination showed an ill-defined mass, 1.5 cm in diameter, located in the upper outer quadrant of the patient's left breast. Mammography revealed diffuse microcalcification in both breasts but ultrasonography revealed an irregular tumorous lesion only in the left breast. Aspiration breast cytology revealed adenocarcinoma of the left breast. Modified radical mastectomy of the left breast and excision of a biopsy specimen from the right breast were carried out simultaneously. Histopathologically the left-breast tumor was an atypical medullary carcinoma with cartilaginous metaplasia, of histological grade 3, and the right-breast specimen showed fibrocystic changes with atypical ductal hyperplasia. Estrogen receptors were positive, but progesterone receptor was not detected on the tumor cells, which were immunopositive for nuclear p53 although c-erbB-2 overexpression was not observed. A nonsense germline mutation of the BRCA1 gene (exon5) was detected. The patient has been well since the operation (10 months). These findings may provide useful information about the carcinogenesis and biological behavior of BRCA1-associated breast cancers.

Adenocarcinoma↗
PubMed2000

Changes in findings of mammography, ultrasonography and contrast-enhanced computed tomography of three histological complete responders with primary breast cancer before and after neoadjuvant chemotherapy: case reports.

We report the changes in the findings of imaging examinations (mammography, ultrasonography and contrast-enhanced computed tomography) of three patients with primary breast cancer before and after neoadjuvant chemotherapy, who obtained histologically complete responses after the chemotherapy. The neoadjuvant chemotherapy consisted of four cycles of doxorubicin and docetaxel. All patients were clinically judged as partial responders, because of the remaining tumorous lesions in the imaging examinations. However, these tumorous lesions could be related to the chemotherapy-induced fibrosis and tumor necrosis or the remaining fibrocystic changes. In this study, it was considered very difficult to estimate the extent of residual tumors accurately in patients with primary breast cancer after neoadjuvant chemotherapy by any type of imaging examination.

Aged↗
PubMed2000

Large, central acellular zones indicating myoepithelial tumor differentiation in high-grade invasive ductal carcinomas as markers of predisposition to lung and brain metastases.

High-grade invasive ductal carcinomas (IDCs) of the breast with large, central acellular zones on their cut surfaces are usually associated with the myoepithelial immunophenotype of carcinoma cells, which includes the expression of S-100 protein, alpha-smooth muscle actin, and keratin 14. To clarify the clinical significance of these features of IDCs, the authors compared the incidence of the myoepithelial immunophenotype immunohistochemically, patient prognosis, and metastatic sites of the tumor between 20 high-grade IDCs with large, central acellular zones and 40 control high-grade IDCs without these zones. The myoepithelial immunophenotype was detected in 16 IDCs (80%) with large, central acellular zones but in only seven IDCs (18%) without. The risk ratio of metastasis, especially in the brain and lung, and death from cancer were significantly higher (p = 0.0096 and p = 0.030) for the 20 IDCs with large, central acellular zones than for those without by Cox's univariate analysis. Using Cox's multivariate analysis, large, central acellular zones in IDCs were an indicator of high risk of brain and lung metastases and of death by cancer independent of nodal status and tumor size. Examination of large, central acellular zones and myoepithelial immunophenotype in high-grade IDCs appears helpful in predicting patient prognosis and preferential metastatic sites of the tumors.

Actins↗
PubMed2000

Reappraisal of orthodox histochemistry for the diagnosis of minimal deviation adenocarcinoma of the cervix.

Minimal deviation adenocarcinoma (MDA), or adenoma malignum, of the uterine cervix is a diagnostically problematic disease because of the difficulty in differentiating it histologically from normal cervical glands. To evaluate the use of mucin phenotyping for differentiating MDA from other conditions, we performed alcian blue pH 2.5/periodic acid-Schiff (AB-PAS) staining and high iron diamine (HID)-AB staining on routinely processed sections of 11 MDAs, 20 unremarkable cervical glands, 9 cervical glandular hyperplasias occurring in association with mucinous ovarian tumors, and 41 conventional cervical adenocarcinomas. In all 11 MDAs and 11 conventional cervical adenocarcinomas, the tumor cell cytoplasm was stained diffusely red by PAS, indicating that MDA cells produce neutral mucin almost exclusively. The amount of acid mucins, both sulfomucin and sialomucin, was decreased markedly by HID-AB. For four MDAs, preoperative biopsy specimens also showed diffuse cytoplasmic neutral mucin. In contrast, the cytoplasm of constituent cells was stained purple to violet by AB-PAS in all unremarkable cervical glands and glandular hyperplasias, indicating that both acid and neutral mucins were produced in equal amounts, sulfomucin being stained predominantly by HID-AB. Of the 30 conventional cervical adenocarcinomas, 28 showed both acid and neutral mucins and two showed acid mucin only in goblet cells, or in part of the cytoplasm or cell surface of constituent cells, where acid mucin consisted predominantly of sulfomucin in 14 and sialomucin in 16. AB-PAS and HID-AB are simple and orthodox histochemical methods which are effective for differential diagnosis of MDA and can contribute to its early detection and treatment.

Adenocarcinoma↗
PubMed2000

Chemopreventive effect of bovine lactoferrin on 4-nitroquinoline 1-oxide-induced tongue carcinogenesis in male F344 rats.

The modifying effects of dietary feeding of bovine lactoferrin (bLF) on tongue carcinogenesis initiated with 4-nitroquinoline 1-oxide (4-NQO) were investigated in male F344 rats. The activities of phase II detoxifying enzymes, glutathione S-transferase (GST) and quinone reductase (QR), polyamine content and ornithine decarboxylase (ODC) activity in the tongue were also examined for mechanistic analysis of possible modifying effects of bLF on carcinogenesis. At 7 weeks of age, all animals except those treated with bLF alone and untreated rats were given 20 ppm 4-NQO in drinking water for 8 weeks to induce tongue neoplasms. Starting 7 days before 4-NQO exposure, experimental groups were fed experimental diets containing bLF (0.2% and 2%) for 10 weeks ("initiation feeding"). Starting 1 week after the cessation of exposure to 4-NQO, the other experimental groups given 4-NQO and a basal diet were fed the experimental diets for 22 weeks ("postinitiation feeding"). At week 32, the incidence and multiplicity of tongue neoplasms in the "initiation feeding" groups of 0.2% and 2% bLF and the "post-initiation feeding" group of 0.2% bLF were lower than those of the 4-NQO alone group, but without statistical significance. However, "post-initiation feeding" of 2% bLF caused a significant reduction in the incidence (20% vs. 55%, P=0.02418) and multiplicity (0.25+/-0.54 vs. 0.70+/-0.71, P<0.05) of tongue squamous cell carcinoma (by 64%, P=0.02418). bLF treatment elevated liver and tongue GST activities and liver QR activity. The "post-initiation feeding" with 2% bLF significantly decreased QR activity, proliferating cell nulcear antigen-positive index and ODC activity in the tongue. In addition, feeding with bLF decreased tongue polyamine content. These results suggest that bLF, when given at the 2% dose level during the post-initiation phase, exerts chemopreventive action against tongue tumorigenesis through modification of cell proliferation activity and/or the activities of detoxifying enzymes.

4-Nitroquinoline-1-oxide↗
PubMed2000

Activation of intestinal mucosal immunity in tumor-bearing mice by lactoferrin.

We have previously demonstrated that oral administration of bovine lactoferrin (bLF) markedly increases CD4(+) and CD8(+) T cells and NK (asialoGM1(+) ) cells in the blood of tumor-bearing mice and enhances anti-metastatic activity. In this paper, we document that oral administration of bLF and bLF-hydrolysate (bLFH) is associated with strong increases in CD4(+) and CD8(+) T, as well as asialoGM1(+) cells in lymphoid tissues and lamina propria of the small intestine in mice, especially in tumor-bearing animals in which Co26Lu cells were implanted subcutaneously. Moreover, IgM(+) and IgA(+) B cells in lamina propria of the small intestine were also significantly increased by bLF and bLFH. Bovine apo-transferrin (bTF) did not exhibit such activity. In the colon, only CD8(+) cells were significantly increased by treatment with bLF, while asialoGM1(+) cells were significantly decreased. bLF and bLFH induced cytokines to activate T, B and asialoGM1(+) cells. Administration of bLF and bLFH, but not bTF, increased production of interleukin-18 (IL-18), interferon-gamma (IFN-gamma) and caspase-1 in the mucosa of the small intestine. Particularly high levels of IL-18 were found in the epithelial cells of the small intestine. Moreover, administration of bLF and bLFH, but not bTF, induced IFN-gamma presenting cells in the small intestine. Caspase-1, which processes proIL-18 to mature IL-18, was also induced in the epithelial cells of the small intestine following treatment with bLF and bLFH, but not with bTF. These results suggest that enhanced production of IL-18 and IFN-gamma and caspase-1 induction by treatment with bLF may be important for elevation of intestinal mucosal immunity.

Administration, Oral↗
PubMed2000

Evaluation of the interobserver agreement in the number of mitotic figures of breast carcinoma as simulation of quality monitoring in the Japan National Surgical Adjuvant Study of Breast Cancer (NSAS-BC) protocol.

In the National Surgical Adjuvant Study for Breast Cancer (NSAS-BC), node-negative breast cancers were divided into higher- and lower-risk groups according to the histopathological nuclear grade given at individual collaborating hospitals, and the higher-risk group was entered into a randomized protocol of adjuvant therapy. Because the nuclear grade was the composite of nuclear atypia and mitotic counts, maintenance of interobserver agreement in mitotic counts was indispensable for the success of the protocol study. Fourteen pathologists participating in the protocol judged whether or not 20 photomicrographs suspected of showing mitotic cancer-cell figures truly showed mitoses. After standardizing the counting method, these pathologists counted the number of mitotic figures per 10 high-power fields of hematoxylin-eosin-stained main-tissue sections of 20 tumors. Areas where mitotic counts were considered to be the most frequent by each pathologist were compared for these tumors. For the judgment of whether the photomicrograph indicated mitosis, the level of interobserver agreement was moderate (kappa = 0.569). In the observations of 20 tumors, interobserver agreement level of mitotic counts was moderate (kappa = 0.506), that of nuclear atypia scoring was fair (kappa = 0.265), and that of nuclear grading was substantial (kappa = 0.633). The counted area was almost the same among the observers in 9 tumors, split into two areas in 6, and dispersed in 5. Concordance in judgment was achieved in 7 of the first 9 and in all of the third 5, but only in one of the second 6. The cause of discordance was mostly derived from tumor heterogeneity and the difference in the site where mitoses were counted. Interobserver agreement level was considered to be satisfactory, and it was expected that the case entry would be performed appropriately in the protocol study. The selection of the counting area was confirmed to be important for the acquisition of high-level agreement level in mitotic counts.

Breast Neoplasms↗
PubMed2000

Chemopreventive effects of bovine lactoferrin on N-butyl-N-(4-hydroxybutyl)nitrosamine-induced rat bladder carcinogenesis.

Chemopreventive effects of bovine lactoferrin (bLF), which is found at high concentrations in colostrum, on rat bladder carcinogenesis were investigated using a rat bladder medium-term bioassay. In experiment 1, a total of 80 F344 male rats, 6 weeks old, were divided into 5 groups. Groups 1 and 2 were treated with 0.05% N-butyl-N-(4-hydroxybutyl)nitrosamine (BBN) in the drinking water for 8 weeks and after a 1-week interval, received dietary supplementation with 2% and 0.2% bLF, respectively. Group 3 received 0.05% BBN for 8 weeks and then no treatment. Group 4 was administered 2% bLF alone from week 9, without prior carcinogen exposure. Group 5 was maintained without any treatment throughout the experiment. All rats were killed at the end of week 36. Group 1 demonstrated a significantly decreased multiplicity of the bladder tumors (carcinomas and papillomas) as compared with group 3. Maximum cut surface areas of bladder tumors were also significantly decreased in groups 1 and 2 compared with group 3. No bladder tumors were observed in groups 4 or 5. In experiment 2, a total of 60 rats were divided into two groups (30 rats each); both were treated with 0.05% BBN for 4 weeks and after a 1-week interval, one received 2% bLF (group 1) and the other, basal diet (group 2) for 4 weeks. Group 1 demonstrated a tendency for decrease of the 5-bromo-2'-deoxyuridine (BrdU) labeling index. bLF was detected in the urine of rats fed bLF by ELISA as well as western blot analysis. The findings indicate that 2% bLF can inhibit BBN-induced rat bladder carcinogenesis, and that this may be due to bLF in the urine.

Acetyltransferases↗
PubMed2000

Preferential occurrence of breast carcinomas with loss of chromosome 16q and der (16) t (1;16) / der (1;16) in middle-aged patients with hyperplasia of mammary glands.

Structural and numerical alterations of chromosome 16 are considered to be commonly involved in the genesis of breast cancer. To reveal etiological factors that predispose cells to these alterations, we examined the frequencies of chromosome 16 aneusomy, 16q loss and 1;16 fusion indicating der (16) t (1;16) / der (1;16) by multi-color fluorescence in situ hybridization in 46 tumors resected mostly from young ( </= 34 years old) or elderly ( >/= 75 years old) women, and compared the results with those in a patient group representing a common age distribution of Japanese patients in whom chromosome 16 status in the tumor had already been studied. The correlation of these chromosome 16 alterations with age, hyperplasia in adjacent mammary glands, cancer history, and obesity indices was investigated in a total of 244 patients. In the present 46 tumors, the frequency of 16q loss and der (16) t (1;16) did not differ between 20 younger patients (30% and 15%) and 23 elderly patients (43% and 13%). However, the incidences of 16q loss and der (16) t (1;16) were low in comparison with the values of 64% and 38% in the 198 Japanese patients representing the common age distribution (P < 0.001). In addition, 16q loss and der (16) t (1;16) were more frequent in tumors arising in hyperplastic mammary glands (68%, 44%) than in those without (52%, 24%) (P < 0.01). Such correlations were not evident for 16cen aneusomy. Other etiological factors examined were not correlated with these chromosome 16 alterations. The 16q loss and der (16) t (1;16) formation were more frequently involved in the development of breast cancer in middle-aged patients than in young and elderly patients. High-level estrogens and / or sensitivity of mammary glandular cells to estrogens might induce breast cancers with structural changes of chromosome 16.

Adult↗
PubMed2000

Role of serotype-specific polysaccharide in the resistance of Streptococcus mutans to phagocytosis by human polymorphonuclear leukocytes.

To clarify the role of cell surface components of Streptococcus mutans in resistance to phagocytosis by human polymorphonuclear leukocytes (PMNs), several isogenic mutants of S. mutans defective in cell surface components were studied with a luminol-enhanced chemiluminescence (CL) assay, a killing assay, and a transmission electron microscope. The CL responses of human PMNs to mutant Xc11 defective in a major cell surface antigen, PAc, and mutant Xc16 defective in two surface glucosyltransferases (GTF-I and GTF-SI) were the same as the response to the wild-type strain, Xc. In contrast, mutant Xc24R, which was defective in serotype c-specific polysaccharide, induced a markedly higher CL response than the other strains. The killing assay showed that human PMNs killed more Xc24R than the parent strain and the other mutants. The transmission electron microscopic observation indicated that Xc24R cells were more internalized by human PMNs than the parental strain Xc. These results may be reflected by the fact that strain Xc24R was more phagocytosed than strain Xc. The CL response of human PMNs to a mutant defective in polysaccharide serotype e or f was similar to the response to Xc24R. Furthermore, mutants defective in serotype-specific polysaccharide were markedly more hydrophobic than the wild-type strains and the other mutants, suggesting that the hydrophilic nature of polysaccharides may protect the bacterium from phagocytosis. We conclude that the serotype-specific polysaccharide, but not the cell surface proteins on the cell surface of S. mutans, may play an important role in the resistance to phagocytosis.

Antigens, Bacterial↗
PubMed2000

Type I and type II T cell profiles in chronic myelogenous leukemia.

T cell immunity is considered to play an important role in the control of cell growth in chronic myelogenous leukemia (CML) although information regarding the characteristics of T lymphocytes in CML patients is limited. Using flow cytometric analysis of intracellular cytokine expression at the single-cell level, we analyzed helper T and cytotoxic T subsets in 8 CML patients. The percentage of interferon-gamma (IFN-gamma) single-positive CD4 cells (Th1) and that of interleukin-4 (IL-4) single-positive CD4 cells (Th2) was markedly decreased in pretreated CML patients compared to normal controls. In addition, the percentage of IFN-gamma/IL-4 double-positive CD4 cells (Th0) was also reduced. Consequently, the percentage of IFN-gamma/IL-4 double-negative CD4 cells was markedly increased. Similarly, a reduction in IFN-gamma single-positive CD8 cells (Tc1) and IFN-gamma/IL-4 double-positive CD8 cells (Tc0) and an increase in IFN-gamma/IL-4 double-negative CD8 cells were observed in pretreated CML patients. Imbalance of these parameters was markedly improved following cytoreduction therapy. Our findings directly indicate anergic states in CML patients. Determination of the factors that affect Th and Tc profiles may lead to further understanding of immunological states and the development of effective immunotherapy.

Adult↗
PubMed2000

Orally administered lactoferrin exerts an antimetastatic effect and enhances production of IL-18 in the intestinal epithelium.

The effects of oral administration of bovine lactoferrin (bLF) and its hydrolysate on the lung colonization by colon 26 carcinoma were investigated. At doses of 100 or 300 mg/kg/day for seven successive days, bLFs demonstrated a significant inhibitory effect on experimental metastasis, which indicated effectiveness before and after tumor implantation. Oral administration of bLFs augmented CD4+, CD8+, and asialoGM1+ cells in the spleen and peripheral blood. Their cytotoxic activities against Yac-1 and colon 26 carcinoma were enhanced by bLF. In the small intestinal epithelium, CD4+ and CD8+ cells were markedly increased, and, simultaneously, enhanced production of interleukin-18 (IL-18) was confirmed in the intestinal epithelial cells. In this model, intravenous injection of murine IL-18 showed significant inhibition of the lung colonization by colon 26 carcinoma. These results suggested that inhibition of experimental metastasis by oral administration of bLF and pepsin hydrolysate of bLF might be due to enhanced cellular immunity, presumably mediated by enhanced IL-18 production in the intestinal epithelium.

Administration, Oral↗
PubMed2000

Transgenic rats carrying copies of the human c-Ha-ras proto-oncogene exhibit enhanced susceptibility to N-butyl-N-(4-hydroxybutyl)nitrosamine bladder carcinogenesis.

We have established a transgenic rat line carrying three copies of the human c-Ha-ras proto-oncogene with its own original promoter region, Jcl/SD-TgN(HrasGen)128Ncc (Hras128) rat. c-Ha-ras protein from expression of transduced and endogenous c-Ha-ras genes could be detected in the bladder epithelium of untreated transgenic rats. To examine their susceptibility to N-butyl-N-(4-hydroxybutyl)nitrosamine (BBN)-induced urinary bladder carcinogenesis, male transgenic and wild-type littermates were treated with 0.05% BBN in their drinking water for 10 weeks and then killed at week 20. The numbers and volumes of total macroscopic bladder tumors including both transitional cell papillomas and carcinomas (TCC) per rat were much greater in Hras128 rats than in their wild-type counterparts. The numbers of carcinomas per rat were also significantly greater in Hras128 rats. Two cases of TCC exhibiting invasion of the bladder muscle layer, which is extremely rare in the wild-type animals under the experimental conditions used, were also observed in Hras128 rats. The GGC-->GAC mutations at codon 12 of the transgene were observed in only two TCC out of 21 bladder tumors (9.5%), assessed by RFLP analysis and direct sequencing. SSCP analysis did not show any endogenous c-Ha-ras gene mutations. One of 25 tumors (4.0%) in wild-type rats had an endogenous c-Ha-ras gene mutation at codon 12 that was detected (GGA-->GAA) by single-strand conformation polymorphism and direct sequencing. These results indicate that the Hras128 rat is highly susceptible to BBN carcinogenesis and may be utilized as a rat model for analysis of bladder tumor development. The mutation findings indicate that the enhanced tumor development is not primarily due to mutations occurring in the transgene.

Animals↗