A Mouse Model of Cholangiocarcinoma Uncovers a Role for Tensin-4 in Tumor Progression.

BACKGROUND AND AIMS: Earlier diagnosis and treatment of intrahepatic cholangiocarcinoma (iCCA) are necessary to improve therapy, yet limited information is available about initiation and evolution of iCCA precursor lesions. Therefore, there is a need to identify mechanisms driving formation of precancerous lesions and their progression toward invasive tumors using experimental models that faithfully recapitulate human tumorigenesis. APPROACH AND RESULTS: To this end, we generated a mouse model which combines cholangiocyte-specific expression of KrasG12D with 3,5-diethoxycarbonyl-1,4-dihydrocollidine (DDC) diet-induced inflammation to mimic iCCA development in patients with cholangitis. Histological and transcriptomic analyses of the mouse precursor lesions and iCCA were performed and compared with human analyses. The function of genes overexpressed during tumorigenesis was investigated in human cell lines. We found that mice expressing KrasG12D in cholangiocytes and fed a DDC diet developed cholangitis, ductular proliferations, intraductal papillary neoplasms of bile ducts (IPNBs), and, eventually, iCCAs. The histology of mouse and human IPNBs was similar, and mouse iCCAs displayed histological characteristics of human mucin-producing, large-duct-type iCCA. Signaling pathways activated in human iCCA were also activated in mice. The identification of transition zones between IPNB and iCCA on tissue sections, combined with RNA-sequencing analyses of the lesions supported that iCCAs derive from IPNBs. We further provide evidence that tensin-4 (TNS4), which is stimulated by KRASG12D and SRY-related HMG box transcription factor 17, promotes tumor progression. CONCLUSIONS: We developed a mouse model that faithfully recapitulates human iCCA tumorigenesis and identified a gene cascade which involves TNS4 and promotes tumor progression.

Association between Repeated Praziquantel treatment and Papillary, and Intrahepatic Cholangiocarcinoma.

INTRODUCTION AND AIM: The carcinogenesis of tubular and papillary cholangiocarcinoma (CCA) differ. The available epidemiologic studies about risk factors for CCA do not differentiate between the tubular and papillary type. The current study investigated the relationship between the number of repeated use of Praziquantel (PZQ) treatments and each type of CCA. MATERIAL AND METHODS: This was a hospital-based, matched, case-control study of patients admitted to Srinagarind Hospital, Khon Kaen University. The patients were 210 pathologically-confirmed cases of CCA, while the controls were 840 subjects diagnosed with other diseases. The 4 controls were individually matched with each case by sex, age, and date of admission. The cases were classified according to location (intrahepatic vs. extrahepatic) and cell type (papillary vs. tubular). Multivariable conditional logistic regression was used for the analysis. RESULTS: After adjusting for confounders, there were statistically significant associations between intrahepatic and papillary CCA and repeated use of PZQ treatment. The respective odds of developing intrahepatic CCA for those who used PZQ once, twice, or more was 1.54 (95%CI:0.92-2.55 ), 2.28 (95%CI:0.91-5.73), and 4.21 (95%CI:1.61-11.05). The respective odds of developing papillary CCA for those who used PZQ once, twice, or more was 1.45 (95%CI:0.80-2.63), 2.96 (95%CI:1.06-8.24), and 3.24 (95%CI:1.09-9.66). There was no association between number of uses of PZQ treatment and developing extrahepatic or tubular CCA. CONCLUSION: The current study found an association between papillary and intrahepatic CCA and repeated use of PZQ treatment. We suggest further study on the risk factors for papillary and tubular CCA should be performed separately.

Correlation between serum lead and thyroid diseases: papillary thyroid carcinoma, nodular goiter, and thyroid adenoma.

Studies have showed that lead was associated with human health. However, the effects of lead on thyroid functions are inconsistent, and studies based on Chinese population are fragmentary. To evaluate the correlation between lead and thyroid functions of Chinese with different thyroid diseases, we conducted a hospital-based study. Ninety-six papillary thyroid carcinoma (PTC), 10 nodular goiter (NG), and 7 thyroid adenoma (TA) patients were recruited from the First Affiliated Hospital of Wenzhou Medical University, China. Serum triiodothyronine (T3), free triiodothyronine (FT3), free thyroxin (FT4), and thyroid stimulating hormone (TSH) were evaluated with chemiluminescent microparticle immunoassay. Serum lead was assessed with ICP-MASS. Partial correlation was used to explore the correlations of serum lead and thyroid diseases. Compared to PTC, the level of lead was significantly higher in TA, and lower in NG (p < 0.05). This difference remained significant in females when stratified by sex. Serum lead was negatively correlated with TSH (rs =  - 0.27, p < 0.05) in PTC group. T3 was positively related to lead at quartile4 (rs = 0.61, p < 0.05) in PTC group. No significant correlations were observed between lead and FT3 or FT4 in any group. The results suggested that lead might have different etiological roles in these three thyroid diseases.

Immunohistochemical Expression of Cyclin D1, Cytokeratin 20, and Uroplakin III in Proliferative Urinary Bladder Lesions Induced by o-Nitroanisole in Fischer 344/N Rats.

o-Nitroanisole is an intermediate in the manufacture of azo dyes. In a National Toxicology Program stop-exposure study,o-nitroanisole induced hyperplasia, papillomas, and papillary carcinomas in the urinary bladder of Fischer 344/N rats.o-Nitroanisole was investigated since occupational or environmental exposure to aniline and azo dyes is a risk factor for urinary bladder cancer in humans. The current study describes the morphology of urinary bladder neoplasms seen in rats with respect to those observed in humans. This study also evaluated immunohistochemical expression of the cell cycle-related proteins cyclin D1 and p53 and the differentiation markers cytokeratin 20 and uroplakin III in hyperplastic (n= 11) and neoplastic (n= 6 papillomas,n= 11 carcinomas) lesions of the urinary bladder epithelium from rats treated with o-nitroanisole and in normal (n= 6) urinary bladders from untreated rats. The tumors observed were more similar to the papillary type rather than the muscle-invasive type of urinary bladder cancer in humans. The preneoplastic and neoplastic lesions observed suggest progression from hyperplasia to papilloma to papillary carcinoma. With neoplastic progression (hyperplasia to papilloma to carcinoma), cyclin D1 immunoreactivity progressively increased in intensity, percentage of cells staining, and distribution. Overexpression of p53 was not found. Cytokeratin 20 staining decreased in superficial cells, while uroplakin III staining increased in intermediate and basal cells with progression from hyperplasia to carcinoma. The results are consistent with increased cell cycle dysregulation or proliferation (cyclin D1), decreased differentiation (cytokeratin 20), and abnormal differentiation (uroplakin III) as lesions progress toward malignancy.

Melatonin potentiates the anti-tumour effect of pravastatin in rat mammary gland carcinoma model.

Previous studies in the field of cancer research have suggested a possible role for statins in the reduction of risk in certain malignancies. The purpose of these studies was to examine the chemopreventive effects of pravastatin alone and in combination with pineal hormone melatonin in the N-methyl-N-nitrosourea-induced mammary carcinogenesis model. Pravastatin was given orally (1 00 mg/kg) and melatonin was added to the water (20 µg/ml). Chemoprevention began seven days prior to carcinogen administration and subsequently continued for 15 weeks until autopsy. At autopsy, mammary tumours were removed and prepared for histopathological and immunohistochemical analysis. Parameters of experimental carcinogenesis, mechanism of action (biomarkers of apoptosis, angiogenesis and proliferation) and side effects after long-term treatment in animals were assessed. Pravastatin alone suppressed tumour frequency by 20.5% and average tumour volume by 15% compared with controls. Combined administration of the drugs decreased tumour frequency by 69% and lengthened tumour latency by nine days compared with control animals. The ration between high and low grade carcinomas was apparently reduced in both treated groups. The analysis of carcinoma cells showed significant expression increase in caspase-3 and caspase-7 after pravastatin treatment; however, combined treatment even more pronounced increase in the expression of both caspases. Regarding VEGFR-2 expression, a small effect in carcinomas of both treated groups was found. In plasma metabolism evaluation, pravastatin alone significantly decreased levels of glucose and triacylglycerols. Our results suggest a mild anti-neoplastic effect of pravastatin in this rat mammary gland carcinoma model. Statins co-administered with other suitable drug (e.g. melatonin) should be further evaluated for tumour-preventive properties.

Bladder cancers arise from distinct urothelial sub-populations.

Bladder cancer is the sixth most common cancer in humans. This heterogeneous set of lesions including urothelial carcinoma (Uca) and squamous cell carcinoma (SCC) arise from the urothelium, a stratified epithelium composed of K5-expressing basal cells, intermediate cells and umbrella cells. Superficial Uca lesions are morphologically distinct and exhibit different clinical behaviours: carcinoma in situ (CIS) is a flat aggressive lesion, whereas papillary carcinomas are generally low-grade and non-invasive. Whether these distinct characteristics reflect different cell types of origin is unknown. Here we show using lineage tracing in a murine model of carcinogenesis that intermediate cells give rise primarily to papillary lesions, whereas K5-basal cells are likely progenitors of CIS, muscle-invasive lesions and SCC depending on the genetic background. Our results provide a cellular and genetic basis for the diversity in bladder cancer lesions and provide a possible explanation for their clinical and morphological differences.

Anticancer benefits of early versus late use of rapamycin in a rat model of urothelial carcinoma.

BACKGROUND: We previously reported both in vivo and in vitro effects of rapamycin on urothelial carcinoma. Clinically, the use of rapamycin could not completely prevent the recurrence of urothelial carcinoma. Therefore, we designed this study to compare the difference of efficacy between early and late use of rapamycin in a rat model of urothelial carcinoma. METHODS: The rat model of urothelial carcinoma was induced by adding 0.05% N-butyl-N-(4-hydroxybutyl) nitrosamine (BBN) to the drinking water for up to 20 weeks in male Fisher-344 rats. Rapamycin was fed orally from the 1st day, 5th week, 9th week, 13th week, and 17th week. The antitumor effects of different periods of rapamycin treatment were assessed grossly and microscopically. RESULTS: Papillary tumors of urinary bladder were successfully induced in the BBN group. Simultaneous use of rapamycin and BBN from the 1st day of treatment significantly reduced the tumor growth in urinary bladder: 80% of the rats had no tumor and 20% had low-grade tumors. Adding rapamycin from the 5th week was associated with more tumor growth: 20% of the rats had no tumors, 20% had low-grade tumors, and 60% had high-grade tumors. Moreover, in the groups with rapamycin treatment from the 9th week, 13th week, and 17th week, all rats developed high-grade papillary tumors in urinary bladder, as did the control group that received no rapamycin. CONCLUSIONS: The study results suggest that the anticancer effect of rapamycin on urothelial carcinoma is stage dependent. Early use of rapamycin provides better anticancer effect, whereas late use of rapamycin fails to inhibit the cancer growth.

Cytogenetic characterization of an N-butyl-N-(4-hydroxybutyl) nitrosamine-induced mouse papillary urothelial carcinoma.

Chemically-induced urinary bladder cancer in rodents has long been used as a reliable model to study the biopathology of urinary bladder neoplasia and to develop therapeutic strategies against human tumors. Knowledge of the genetic basis underlying carcinogenesis would greatly enhance usability and usefulness of this model for the purposes of comparative pathology. However, little is known about the cytogenetic characteristics of rodent urinary bladder tumors. Accordingly, pathological and negative control specimens were collected for cytogenetic evaluation, from an ongoing mouse urinary bladder N-butyl-N-(4-hydroxybutyl) nitrosamine-induced carcinogenesis study. Histopathological analysis characterized the pathological sample as a papillary urothelial carcinoma. Conventional cytogenetic analysis revealed the presence of 66.3 % tetraploid cells. Fluorescent in situ hybridization using chromosome paint probes allowed the detection of a reciprocal translocation involving chromosomes 4 and 14 (containing the murine homologues to human p16 and retinoblastoma tumor-suppressor genes) in 42 % of tetraploid cells. The control sample showed no histological or cytogenetic changes. CDKN2A and RB1 loss of heterozygosity is associated with human early and advanced urinary bladder cancer, respectively. Thus, the present data paves the way for further studies concerning the molecular mechanisms of urinary bladder carcinogenesis.

The effects of sirolimus on urothelial lesions chemically induced in ICR mice by BBN.

BACKGROUND: Sirolimus was originally used as an immunosuppressant drug but recent reports have indicated that it may have other potential biological effects as an anticancer drug. The chemopreventive efficacy of sirolimus was evaluated in an experimental model of invasive urinary bladder cancer. MATERIALS AND METHODS: ICR mice received N-butyl-N-(4-hydroxybutyl) nitrosamine (BBN) in drinking water for a period of twelve weeks. Sirolimus was administered 5 days a week. Animals were sacrificed either one or four weeks after their final treatment. Ki-67 was immunohistochemically analysed in paraffin-embedded tissue. RESULTS: No evidence of host toxicity was found. The incidence of BBN-induced invasive urothelial carcinoma was significantly reduced in mice treated with sirolimus. Preneoplastic and neoplastic lesions exhibited a significant decrease in cellular proliferation. CONCLUSION: Histopathological and immunohistochemical studies showed that sirolimus reduced tumour incidence and proliferation. Sirolimus should be considered for further in vitro and in vivo studies in order to provide evidence of effectiveness.

Papillary thyroid carcinoma in a patient with sarcoidosis treated with minocycline.

Long-term treatment with minocycline is occasionally associated with the development of black thyroid syndrome in which thyroid cancer is frequently found. Here, we report a patient with cutaneous, pulmonary and thyroid sarcoidosis who developed papillary thyroid carcinoma in the presence of a black thyroid syndrome after being treated with minocycline for 2.5 years.

DNA study of bladder papillary tumours chemically induced by N-butyl-N-(4-hydroxybutyl) nitrosamine in Fisher rats.

To examine DNA abnormalities in bladder papillary tumours induced by N-butyl-N-(4-hydroxybutyl) nitrosamine (BBN) in female rats, using image cytometric DNA analysis and cytogenetics. Thirty female rats were exposed to BBN in their drinking water for 20 weeks. One group of 10 animals served as controls. The animals exposed to BBN were killed at a rate of two per week, with the bladder being collected under aseptic conditions and those tumours with exophytic growth removed. The nuclear DNA content of the tumours was evaluated using image cytometric analysis. In two rats part of the tumour pieces was stipulated for culturing. Cytogenetic analysis was performed on at least 30 cells from each cell population and on both tumours. Papillary carcinomas were classified as low grade and high grade. DNA ploidy studies were carried out on 28 low-grade and 21 high-grade papillary carcinomas. Histograms obtained by image analysis showed that a normal urothelium was diploid; 28.6% and 100% of low-and high-grade papillary carcinomas were aneuploid respectively. Both tumours used for cell culture showed multiple numerical and structural chromosome alterations and several marker chromosomes. Image cytometric DNA analysis proved to be a good and reliable method for examining DNA alterations in papillary bladder carcinomas. The present findings establish that the DNA content is statistically different between low-grade and high-grade papillary carcinomas and that deviation from the diploid number is markedly higher in the high-grade ones. In addition, the occurrence of marker chromosomes seems to be related to the aggressiveness of the tumour.

E-cadherin expression during urothelial carcinogenesis induced by N-butyl-N-(4-hydroxybutyl) nitrosamine in rats.

An alteration in the expression of E-cadherin has been observed in many epithelial neoplasms. No data exist, however, for the expression of this protein in an animal model for urinary bladder cancer. The present study investigated the expression of E-cadherin in rat urothelial preneoplastic lesions and tumours induced by oral administration of N-butyl-N-(4-hydroxybutyl) nitrosamine, during 10, 15 and 20 weeks. Simple hyperplasia and squamous metaplasia showed a similar E-cadherin pattern when compared with normal urothelium, with its expression confined to cell membrane. Thirty eight percent of the nodular hyperplasia, 41.4% of the dysplasia and 100% of the papillomas showed a weak E-cadherin expression. All papillary neoplasm of low malignant potential, low-and high-grade papillary carcinoma, and invasive carcinoma revealed an abnormal staining pattern with an increase in cytoplasm reactivity and discontinuous cell membrane positivity. The loss of expression for low-grade papillary carcinoma versus simple hyperplasia, nodular hyperplasia and dysplasia was statistically significant (p = 0.0001, p = 0.007 and p=0.008, respectively). There was a similar decrease in E-cadherin expression for papillary neoplasm of low malignant potential versus simple hyperplasia, nodular hyperplasia and dysplasia (p = 0.0001; p = 0.001 and p=0.0001, respectively). These results suggest that alteration in the expression of this adhesion molecule in rat may be indicative of tumour progression in N-butyl-N-(4-hydroxybutyl) nitrosamine-induced bladder cancer.

Bile-reflux into the pancreatic ducts is associated with the development of intraductal papillary carcinoma in hamsters.

BACKGROUND: Reflux of pancreatic juice into the biliary tract is a well-known risk factor for the development of biliary carcinoma. In this study, we investigated the significance of bile-reflux into the pancreatic ducts in pancreatic carcinogenesis, especially in the development of carcinoma in the main pancreatic duct in hamsters. MATERIALS AND METHODS: Syrian hamsters were subjected to three different surgical procedures: cholecystoduodenostomy with dissection of the extrahepatic bile duct on the distal end of the common duct (Model A); cholecystoduodenostomy along with a dissection of the common bile duct (Model B); or simple laparotomy (Model C). The animals then received weekly subcutaneous injections of N-nitrosobis(2-oxopropyl)amine (BOP), for 9 weeks, and were killed for pathological investigation at 16 weeks after the initial BOP administration. RESULTS: Pancreas carcinomas developed in 95, 88, and 90% of the Model A hamsters (n = 22), B (n = 24), and C (n = 21), respectively. The induced pancreatic tumors were histologically classified into four types: papillary; tubular; cystic adenocarcinoma; or intraductal carcinoma of the main pancreatic duct consisting of intraductal papillary carcinoma (IPC) and intraductal tubular carcinoma (ITC). The number and the incidence of IPCs induced in Model A hamsters were 24 lesions and 77% and were statistically higher than those in Model B (7 lesions and 29%) and C hamsters (7 lesions and 33%) (P < 0.01). Bile-reflux into the pancreatic ducts was clearly demonstrated in only hamsters of Model A by means of Indocyanine green injection via the portal vein. Proliferative cell nuclear antigen labeling indices of the epithelial cells in the main pancreatic duct in hamsters, with no BOP treatment, were 3.8, 0.8, and 1.1% in Models A (n = 10), B (n = 10), and C (n = 10), respectively, and the difference was statistically significant (P < 0.01). CONCLUSIONS: Our findings suggest that bile-reflux into the pancreatic ducts is a significant factor predisposing to the development of IPC of the pancreas through an acceleration of epithelial cell kinetics of the main pancreatic duct.

Lithium-associated hypothyroidism and thyroid papillary carcinoma: a case report.

Ionizing radiation, some hereditary factors, and chronic thyroid-stimulating hormone elevation increases the risk of differentiated thyroid carcinoma. Lithium salts are used in the treatment of affective (mood) disorders as well as a variety of other psychiatric conditions. There have been occasional reports of hematologic and solid neoplasms associated with lithium use. We report a patient who developed hypothyroidism and subsequently, thyroid papillary carcinoma while on lithium treatment for bipolar affective disorder.

Papillary thyroid carcinoma after recombinant GH therapy for Turner syndrome.

Turner syndrome (TS) has been included for several years among the indications for GH treatment, generally with satisfactory outcomes. Nevertheless, the long-term effects of this treatment in non-GH deficient patients are not fully known. The incidence of thyroid carcinoma is rare in patients during childhood, it is unusual to find this neoplasia in children under sixteen years old. This article reports the cases of two Spanish patients with papillary thyroid carcinoma after GH treatment for TS. Recent studies have indicated a possible relationship between the GH-IGF axis and the pathogenesis of neoplasias, questioning the chance association of these two pathologies. In line with this, we detected GH receptor expression in the papillary carcinoma cells. Long-term prospective studies are required to clarify the possible effects of GH treatment on the risk of neoplasia.

Insulin-like growth factor (IGF)-I obliterates the pregnancy-associated protection against mammary carcinogenesis in rats: evidence that IGF-I enhances cancer progression through estrogen receptor-alpha activation via the mitogen-activated protein kinase pathway.

INTRODUCTION: Pregnancy protects against breast cancer development in humans and rats. Parous rats have persistently reduced circulating levels of growth hormone, which may affect the activity of the growth hormone/insulin-like growth factor (IGF)-I axis. We investigated the effects of IGF-I on parity-associated protection against mammary cancer. METHODS: Three groups of rats were evaluated in the present study: IGF-I-treated parous rats; parous rats that did not receive IGF-I treatment; and age-matched virgin animals, which also did not receive IGF-I treatment. Approximately 60 days after N-methyl-N-nitrosourea injection, IGF-I treatment was discontinued and all of the animal groups were implanted with a silastic capsule containing 17beta-estradiol and progesterone. The 17beta-estradiol plus progesterone treatment continued for 135 days, after which the animals were killed. RESULTS: IGF-I treatment of parous rats increased mammary tumor incidence to 83%, as compared with 16% in parous rats treated with 17beta-estradiol plus progesterone only. Tumor incidence and average number of tumors per animal did not differ between IGF-I-treated parous rats and age-matched virgin rats. At the time of N-methyl-N-nitrosourea exposure, DNA content was lowest but the alpha-lactalbumin concentration highest in the mammary glands of untreated parous rats in comparison with age-matched virgin and IGF-I-treated parous rats. The protein levels of estrogen receptor-alpha in the mammary gland was significantly higher in the age-matched virgin animals than in untreated parous and IGF-I-treated parous rats. Phosphorylation (activation) of the extracellular signal-regulated kinase-1/2 (ERK1/2) and expression of the progesterone receptor were both increased in IGF-I-treated parous rats, as compared with those in untreated parous and age-matched virgin rats. Expressions of cyclin D1 and transforming growth factor-beta3 in the mammary gland were lower in the age-matched virgin rats than in the untreated parous and IGF-I-treated parous rats. CONCLUSION: We argue that tumor initiation (transformation and fixation of mutations) may be similar in parous and age-matched virgin animals, suggesting that the main differences in tumor formation lie in differences in tumor progression caused by the altered hormonal environment associated with parity. Furthermore, we provide evidence supporting the notion that tumor growth promotion seen in IGF-I-treated parous rats is caused by activation of estrogen receptor-alpha via the Raf/Ras/mitogen-activated protein kinase cascade.

Oral cavity and esophageal carcinogenesis modeled in carcinogen-treated mice.

PURPOSE: Squamous cell carcinoma of the oral cavity is one of the most common human neoplasms, and prevention of these carcinomas requires a better understanding of the carcinogenesis process and a model system in which cancer chemoprevention agents can be tested. We have developed a mouse model using the carcinogen 4-nitroquinoline 1-oxide (4-NQO) in the drinking water to induce tumorigenesis in the mouse oral cavity. EXPERIMENTAL DESIGN: 4-NQO was delivered by tongue painting or drinking water to two mouse strains, CBA and C57Bl/6. The incidences of oral cavity carcinogenesis were then compared. In addition, we examined the expression of some of the molecular markers associated with the process of human oral cavity and esophageal carcinogenesis, such as keratin (K) 1, K14, p16, and epidermal growth factor receptor, by immunohistochemistry. RESULTS: After treatment with 4-NQO in the drinking water, massive tumors were observed on the tongues of both CBA and C57Bl/6 female mice. Pathological analyses indicated that flat squamous dysplasias, exophytic papillary squamous tumors (papillomas), and invasive squamous cell carcinomas were present. Immunohistochemistry analyses showed that 4-NQO changed the expression patterns of the intermediate filament proteins K14 and K1. K14 was expressed in the epithelial suprabasal layers, in addition to the basal layer, in tongues from carcinogen-treated animals. In contrast, control animals expressed K14 only in the basal layer. Moreover, we observed more bromodeoxyuridine staining in the tongue epithelia of 4-NQO-treated mice. Reduced expression of the cell cycle inhibitor, p16, was observed, whereas 4-NQO treatment caused an increase in epidermal growth factor receptor expression in the mouse tongues. Interestingly, similar features of carcinogenesis, including multiple, large (up to 0.5 cm) exophytic papillary squamous tumors and invasive squamous cell carcinomas, increased bromodeoxyuridine staining, and increased K14 expression, were also observed in the esophagi of 4-NQO-treated mice. However, no tumors were observed in the remainder of digestive tract (including the forestomach, intestine, and colon) or in the lungs or livers of 4-NQO-treated mice. These results indicate that this murine 4-NQO-induced oral and esophageal carcinogenesis model simulates many aspects of human oral cavity and esophageal carcinogenesis. CONCLUSIONS: The availability of this mouse model should permit analysis of oral cavity and esophageal cancer development in various mutant and transgenic mouse strains. This model will also allow testing of cancer chemopreventive drugs in various transgenic mouse strains.

Enhancement of urinary bladder carcinogenesis by combined treatment with benzyl isothiocyanate and N-butyl-N-(4-hydroxybutyl)nitrosamine in rats after initiation.

Previously we reported that benzyl isothiocyanate (BITC) strongly enhanced rat urinary bladder carcinogenesis after initiation with N-butyl-N-(4-hydroxybutyl)nitrosamine (BBN), while potently inhibiting BBN-induction of lesions when given simultaneously with the carcinogen. In the present experiment, the effects of simultaneous treatment with BITC and low-dose BBN on the post-initiation period of rat urinary bladder carcinogenesis were examined. After treatment with 500 ppm BBN for 4 weeks for initiation, groups of 20, 6-week-old, F344 male rats were given 25 ppm BBN alone, basal diet alone, or 100 or 1000 ppm BITC in the diet together with or without 25 ppm BBN in their drinking water for 36 weeks and then killed for autopsy. Further groups consisting of 10 rats each were similarly given BITC or the basal diet together with or without 25 ppm BBN, without initiation treatment. In the initiated groups receiving subsequent BBN exposure, papillary and nodular hyperplasia, dysplasia and carcinoma incidences were significantly increased, and they were further increased by the combined treatment with 100 and 1000 ppm BITC in a dose-dependent manner. In the non-initiation groups, carcinomas were only observed in a single rat in each of the BBN-treated control and BBN/BITC 100 ppm treatment groups. The results indicate that simultaneous treatment with BITC and a low dose of BBN does not inhibit, but rather enhances rat urinary bladder carcinogenesis after appropriate initiation, and further suggest that BITC may be a human risk factor, at least in high-risk populations.