Rapid Emergence of Mammary Preneoplastic and Malignant Lesions in Human c-Ha-ras Proto-Oncogene Transgenic Rats: Possible Application for Screening of Chemopreventive Agents

Matsuoka, Yoichiro; Fukamachi, Katsumi; Hamaguchi, Tetsuya; Toriyama‐Baba, Hiroyasu; Kawaguchi, Hiroaki; Kusunoki, Masato; Yoshida, Haruhiko; Tsuda, Hitoshi

doi:10.1080/714044696

Cited by 7 publications

(10 citation statements)

References 0 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…[29][30][31] Recently our laboratory found increased numbers of TEB in Hras128 rats as compared to wild-type littermates, this presumably contributing to their enhanced susceptibility to carcinogens. 32) Since TEB are also targeted by PhIP, as evidenced by DNA adduct formation, 33) and post-initiation mammary tumor development is influenced by estrogenic hormones, 34) the present finding of mixed epithelial-mesenchymal neoplasms in males may be due to delayed TEB differentiation, along with increased proliferation potential due to the transgene. 32) This is in line with a report that sarcomas were observed in ovariectomized female rats treated with DMBA.…”

Section: Discussionmentioning

confidence: 71%

“…32) Since TEB are also targeted by PhIP, as evidenced by DNA adduct formation, 33) and post-initiation mammary tumor development is influenced by estrogenic hormones, 34) the present finding of mixed epithelial-mesenchymal neoplasms in males may be due to delayed TEB differentiation, along with increased proliferation potential due to the transgene. 32) This is in line with a report that sarcomas were observed in ovariectomized female rats treated with DMBA. 35) The lack of sarcomas in Hras128 rats undergoing ovariectomy after MNU administration 27) may be due to the drastic decrease in tumor yield caused by the reduction in TEB number and also the short duration of the experiment.…”

Section: Discussionmentioning

confidence: 71%

See 1 more Smart Citation

Preferential mammary carcinogenic effects of 2‐amino‐1‐methyl‐6‐phenylimidazo[4,5‐b]pyridine (PhIP) in human c‐Ha‐ras proto‐oncogene transgenic rats

et al. 2004

Self Cite

View full text Add to dashboard Cite

he Ras family is composed of three members, Harvey Ras, Kirsten Ras and N-Ras, which exhibit mutations at variable frequencies in various human and animal tumors, 1) with involvement appearing to be tissue-specific. 2, 3) For example, with N-methyl-N-nitrosourea (MNU) in experimental animals, Haras mutations are found primarily in mammary tumors, [4][5][6] while colon tumors generally have Ki-ras mutations. 7) In humans, Ki-ras mutations are preferentially found in colon, 8,9) pancreatic duct 10) and bile duct carcinomas, 11) and N-ras mutations are typically seen in myeloid leukemia. 12) We have generated a transgenic rat line, harboring copies of a human c-Ha-ras proto-oncogene (Hras128 rat), and have shown that these animals are highly susceptible to mammary, 13,14) bladder 15) and esophageal 16) carcinogens.Heterocyclic amines found in overcooked foods are both mutagenic and carcinogenic to animals, 17) and 2-amino-1-methyl-6-phenylimidazo [4,5-b]pyridine (PhIP), the most abundant in our daily diet, 18) has been shown to induce primarily colon, mammary and prostate tumors in rats. [19][20][21] PhIP intake in food has also been implicated as an important risk factor in humans 22,23) although further analysis of the interactions between PhIP and relevant macromolecules is required for a full understanding of the carcinogenic processes.Although mutational analyses of tumors induced by PhIP have been conducted, 24) specific molecular targets have yet to be elucidated. One problem is that the relatively weak carcinogenic potential requires the use of long experimental periods for lesion induction. This study was conducted to analyze the susceptibility of Hras128 rats to PhIP, in the hope of overcoming the above problem. We show here that Hras128 rats are in fact highly susceptible to PhIP mammary carcinogenesis, and multiple tumors of various morphological types develop in a short period. Furthermore, they feature mutations of the transgene along with down-regulation of BRCA1. Materials and MethodsAnimals and experimental protocol. Seven-week-old Hras128 rats of both sexes were maintained on basal diet (Oriental MF, Oriental Yeast Co., Ltd. Tokyo) with tap water ad libitum under standard conditions. 13) Seven females and 18 males were treated with PhIP HCl salt (NARD Institute, Osaka), at doses of 100 mg and 80 mg/kg body weight, respectively, by gastric intubation, from 3 to 4 times a week over a 9-week period (total, 8 times in females and 10 times in males). Five female and 20 male Hras128 rats were similarly treated with vehicle (saline). Sacrifice was at week 12 for females and week 30 for males. Seven female and 20 male wild-type littermates were also treated with PhIP, and 8 female and 20 male wild-type littermates received the vehicle (saline).The experiments were conducted according to the "Guidelines for Animal Experiments in the National Cancer Center Japan" promulgated by the Committee for Ethics of Animal Experimentation.Tissue preparation. Immediately after killing of the animals, mammary tumors wer...

show abstract

Section: Discussionmentioning

confidence: 71%

Section: Discussionmentioning

confidence: 71%

Preferential mammary carcinogenic effects of 2‐amino‐1‐methyl‐6‐phenylimidazo[4,5‐b]pyridine (PhIP) in human c‐Ha‐ras proto‐oncogene transgenic rats

et al. 2004

Self Cite

View full text Add to dashboard Cite

show abstract

“…12,13) They offer a clear contrast to the decreased susceptibility to MNU-induced mammary carcinogenesis in transgenic rats carrying multiple copies of a rat ras gene driven by the rat Harvey ras promoter. 32) In fact, investigation of the very early stages with neoplastic lesions, atypical hyperplasias and early carcinomas, as the endpoint in paraffin sections of abdominal-inguinal mammary glands, whereby suppressive effects of soy isoflavones could be clearly shown within as little as 20 days after carcinogen exposure, 33) indicate that it has great potential for short-term screening of chemopreventive agents active against mammary carcinogenesis. …”

Section: Discussionmentioning

confidence: 99%

Rapid induction of skin and mammary tumors in human c‐Ha‐ras proto‐oncogene transgenic rats by treatment with 7,12‐dimethylbenz[a]anthracene followed by 12‐O‐tetradecanoylphorbol 13‐acetate

et al. 2004

Self Cite

View full text Add to dashboard Cite

We have established a transgenic rat line carrying 3 copies of the human c-Ha-ras proto-oncogene with its own promoter region (Jcl/SD-TgN(HrasGen)128Ncc) (Hras128 rat), expression being detectable in almost all organs. We have already demonstrated that the rat is highly sensitive to mammary, esophagus and bladder carcinogenesis. In the present study, male and female transgenic and wild-type littermates were topically treated with 2.5 mg of 7,12-dimethylbenz[a]anthracene (DMBA) dissolved in 1.0 ml of acetone on the back skin at 50 days after birth. Starting 1 week thereafter, they were again topically treated with 100 nmol of 12-O-tetradecanoylphorbol 13-acetate (TPA) dissolved in 0.5 ml of acetone 3 times weekly for the following 31 weeks. In males treated with DMBA and/or TPA, skin tumors, including both squamous cell papillomas (SCP) and carcinomas (SCC), were preferentially induced at the DMBA-TPA painting sites: DMBA-TPA, 15/15 (100%); DMBA, 6/8 (75%); TPA, 1/6 (16.7%). They were also, unexpectedly, induced on remote scrotal skin: DMBA-TPA, 13/15 (86.7%); DMBA, 5/8 (62.5%); TPA, 0/6 (0%). Lesions were thus more frequent in the DMBA-TPA group than with DMBA or TPA alone. In females, adenomas and adenocarcinomas of the mammary glands were preferentially induced: DMBA-TPA, 12/14 (85.7%); DMBA, 6/8 (75%); TPA, 3/6 (50%), with only a few small skin papillomas at painting sites. Incidences and numbers of the mammary and skin tumors were much greater in Hras128 rats than in their wild-type counterparts. PCR-RFLP analysis of the transgene indicated that the percentage of the cell populations harboring a mutation in codons 12 and/or 61 ranged from 2% to 60% in individual tumors; skin tumors showed more mutations in codon 61 in the DMBA-treated groups. In contrast, no mutations were detected in the endogenous rat c-Ha-ras gene. These results indicate that the Hras128 rat is highly susceptible to DMBA-TPA skin and mammary carcinogenesis, thus providing a unique painting model for skin as well as mammary gland carcinogenesis, that would be suitable for investigating the role of transgene mutations. (Cancer Sci 2004; 95: 205-210) arious transgenic and knockout mice have proven to be good animal models for analysis of gene functions. In the chemical carcinogenesis field, transgenic mice carrying human c-Ha-ras proto-oncogenes (rasH2 mice) have been shown to be highly susceptible to induction of skin, lung and lymphatic cell tumors by various carcinogens.1-6) However, rats are more frequently used for analysis of events occurring during tumor development. There are thus many more basic experimental data available for rats than mice regarding chemical carcinogenesis, and a variety of preneoplastic lesions, including hepatocellular enzyme-altered foci, for example, are available in rats as surrogate markers for cancer development. 7,8) Furthermore, mammary cancers in rats can be induced without the complication of a viral etiology irrelevant to the disease in man. So far, only limited types of transgenic rats have been de...

show abstract

“…(12) Human c-Ha-ras protooncogene Tg rats have an increased susceptibility to chemical carcinogens that target the mammary gland. (37,38) All of the rats developed preneoplastic mammary lesions within 20 days of the injection of MNU (39) and mammary carcinomas appeared within 8 weeks of treatment with a variety of chemical carcinogens. (29,40) Interestingly, activating mutations in the human transgene are readily detectable in preneoplastic lesions that developed after carcinogen treatment or spontaneously.…”

Section: Discussionmentioning

confidence: 99%

Induction of a novel histone deacetylase 1/c‐Myc/Mnt/Max complex formation is implicated in parity‐induced refractoriness to mammary carcinogenesis

et al. 2008

Self Cite

View full text Add to dashboard Cite

Refractoriness to carcinogen-induced increases in epithelial cell proliferation is a very important characteristic of parous mammary glands. We found that N-methyl-N-nitrosourea (MNU)-induced proliferative burst in the mammary ductal epithelium was blocked in parous glands but not in age-matched virgin (AMV) glands. The inhibition of the proliferative burst in MNU-treated parous mammary glands coincided with the upregulation of Mnt, a Myc-suppressor, and the formation of histone deacetylase 1/Mnt/Max complexes that unexpectedly contained c-Myc. These complexes formed on the promoters of Myc targets, such as ornithine decarboxylase, cyclin D2, and transforming growth factor β β β β1 genes, in quiescent fibroblasts, and were disassembled in serum-stimulated cells. These results suggest that the complexes also function as transcription repressors of the growth-related Myc targets in MNU-treated parous mammary glands. Using the chemical mammary carcinogenesis model of human c-Ha-ras transgenic (Tg) rats, we confirmed that parity protected the mammary glands at the postinitiation phase of tumorigenesis. Although the incidence of 7,12-dimethylbenz[α α α α]anthracene-induced palpable tumors was reduced from 61.5% in the AMV Tg rats to 28.5% in the parous animals, the incidence of early neoplastic lesions in the parous rats was the same as that in the AMV rats. In both rat and mouse models, full-term pregnancy confers resistance to chemical carcinogen-induced mammary tumorigenesis (3,4) and this effect can be mimicked by treatment with estrogen, (5) estrogen and progesterone, (4) or human chorionic gonadotropin.However, the actual mechanism involved in parity protection or hormone-induced protection against breast cancer has not yet been clearly defined. The most widely accepted explanation for pregnancy protection against mammary cancer is that the pregnancy-induced differentiation of terminal end buds and terminal ducts reduces the number of target cells for carcinogenesis.It has also been reported that parous rats have decreased levels of mammogenic hormones, and this decrease has been attributed to the decreased incidence of mammary cancers in these animals. (8,9) However, complete differentiation of the mammary gland does not appear to be an obligatory prerequisite for protection against mammary carcinogenesis. (4,10,11) We have shown that pregnancy following carcinogen exposure as well as pregnancy prior to carcinogen exposure reduces mammary carcinogenesis in rats.This result indicates that pregnancy has the potential to affect the carcinogen-initiated cells that are static at the promotion phase, thus providing further support to the conclusion mentioned above.The proto-oncogene myc has long been known to stimulate cellular proliferation. Aberrant expression of Myc in the mammary glands of transgenic mice results in the development of invasive mammary adenocarcinomas. (13,14) Myc proteins are basic helix-loop-helix leucine-zipper (bHLH-Zip) transcription factors whose function relies on heterodimerization with M...

show abstract

Rapid Emergence of Mammary Preneoplastic and Malignant Lesions in Human c-Ha-ras Proto-Oncogene Transgenic Rats: Possible Application for Screening of Chemopreventive Agents

Cited by 7 publications

References 0 publications

Preferential mammary carcinogenic effects of 2‐amino‐1‐methyl‐6‐phenylimidazo[4,5‐b]pyridine (PhIP) in human c‐Ha‐ras proto‐oncogene transgenic rats

Preferential mammary carcinogenic effects of 2‐amino‐1‐methyl‐6‐phenylimidazo[4,5‐b]pyridine (PhIP) in human c‐Ha‐ras proto‐oncogene transgenic rats

Rapid induction of skin and mammary tumors in human c‐Ha‐ras proto‐oncogene transgenic rats by treatment with 7,12‐dimethylbenz[a]anthracene followed by 12‐O‐tetradecanoylphorbol 13‐acetate

Induction of a novel histone deacetylase 1/c‐Myc/Mnt/Max complex formation is implicated in parity‐induced refractoriness to mammary carcinogenesis

Contact Info

Product

Resources

About