High incidence of rat mammary carcinoma by oral administration of ethyl methanesulphonate.

Ethyl methanesulphonate (EMS), one of the alkylating agents, is known to be a potent mutagen. We tested EMS for its carcinogenicity in female rats by oral administration. EMS was dissolved in drinking tap water at a concentration of 10(-3) M and was given for the first 12 weeks. The subcutaneous tumors were noticed as early as 16 weeks after initiating the experiment. At the 32nd week, all the surviving rats produced tumors; the majority were multiple tumors in the neck, axillar and inguinal areas corresponding to bilateral mammary glands. Histologically, the prevailing feature of the tumors was infiltrating medullary adenocarcinoma consistent with carcinoma of mammary duct origin. Neither regional lymph node involvement nor distant metastases were shown, but intraductal spread of carcinoma was a marked finding during the 32-week period.     

The induction of urothelial hyperplasia by methyl methanesulphonate and ethyl methanesulphonate.

The early and late morphological changes induced in rat bladder urothelium by intravesicular administration of the alkylating agents methyl methanesulphonate (MMS) and ethyl methanesulphonate (EMS) are described. In the short-term, both compounds produced dose-related toxic damage followed by a regenerative hyperplasia of the urothelium. At any given dose-level, the effects of MMS were more severe than those of EMS. Two years after administration of multiple doses of 2.5 mg MMS or 7.5 mg EMS the majority of animals had dose-related simple urothelial hyperplasias with occasional mild dysplasia. However, in three MMS-treated animals the hyperplasias had progressed to well-differentiated transitional-cell carcinomas. No bladder neoplasms were seen in EMS-treated animals. The urothelial response of the rat to MMS and EMS is discussed with reference to the known chemical reactivity of these compounds. It is concluded that EMS is a mitogen for the urothelium and that the few carcinomas which develop following topical exposure of the bladder to MMS do not necessarily reflect any initiating potential in this compound. Rather it is argued that the results are consistent with MMS acting as a promoter in cells which have either been previously initiated or which carry a latent oncogene.     

Mammary tumor induction by N-methyl-N-nitrosourea in genetically resistant Copenhagen rats.

The Copenhagen rat is completely resistant to mammary cancer induction by N-methyl-N-nitrosourea (MNU) when the carcinogen is administered during sexual development, a period when other strains of rats are normally susceptible to mammary gland carcinogenesis. Here we administered 30 mg/kg MNU i.p. to two groups of neonatal (2-3-day-old) Copenhagen rats. One group (group B, 18 animals) received no further treatment, while the other group (group C, 17 animals) received a second dose of 30 mg/kg MNU via the tail vein at 50 days of age. About 30% of the rats in group B and about 70% of those in group C developed mammary carcinomas before they were 1 year of age. About one-half of the tumors in both groups were cribriform adenocarcinomas and one-half were adenosquamous carcinomas. The latter tumor type has not been observed previously in susceptible rat strains. The ability to induce these mammary tumors in the Copenhagen rat suggests that the putative mammary carcinoma suppressor gene is functionally inactive in neonatal animals or is inactivated when these animals are treated with MNU.     

Inhibitory effects of prostaglandin F2 alpha on mammary carcinogenesis induced by ethyl methanesulphonate in rats

The effect of prostaglandin F2 alpha (PGF2 alpha) on mammary carcinogens was examined for a new system in female rats, using ethyl methanesulphonate (EMS). The rats were given EMS orally for a period of 12 weeks starting at age 4 weeks. Mammary carcinomas were first detected at the 16th week and were found in all surviving rats at the 32nd week. The concomitant administration of PGF2 alpha for 8 weeks made the development of tumor retarded; i.e., the carcinomas were first detected at the 30th week and final tumor incidence at the 44th week was 61.1%. The incidence of developing mammary carcinomas and multiplicity (number of mammary carcinomas per rat) were significantly lower in PGF2 alpha treated rats than in those given EMS alone. The inhibitory effect of PGF2 alpha on tumor development was apparent when PGF2 alpha was concomitantly given to the rats with EMS at age 4 weeks, while PGF2 alpha injections after oral administration of EMS at age 16 weeks did not significantly retard tumor development. Histologically, no significant difference in morphology was observed between PGF2 alpha-treated and PGF2 alpha-non-treated rats in either the cancerous or noncancerous mammary tissues. The finding demonstrates that PGF2 alpha inhibits the development of EMS-induced mammary carcinomas when given to younger rats, presumably by affecting the hormonal status rather than by direct action on the mammary glands.     

Mammary and renal tumor induction by low doses of adriamycin in Sprague-Dawley rats

The oncogenic potential of adriamycin was studied in both sexesof Spragu-Dawley rats. Single i.v. injection of 10 or 2 mg andrepeated injections of 2 mg of adriamycin/kg body wt within2 weeks were performed on rats, 50 days old at the commencement.All surviving animals were killed at 52 weeks of the experiment.Multiple mammary tumors, mostly flbroadenomas, were observedin 30 and 41% of the females given single low (2 mg/kg) or repeateddoses (5x2 mg/kg) respectively. These incidences were significantlyhigher than those for the corresponding control group (8%).Two male rats in the low dose group also developed mammary tumors.Both sexes receiving the single high dose (10 mg/kg) injectiondemonstrated early mortality due to marked toxkaty. The mortalityof five repeated-treatment group was lower than a single high-dosegroup. Renal cell tumors were evident in five rats of the single,low dose groups and dysplastic foci of renal tubular epitheliumoccurred in the groups given a single low or repeated dosesof adriamycin. Thus the present experiment provides preliminaryindication of carcinogenic potential of this chemotherapeuticagent for both kidney and mammary gland of Sprague-Dawley ratsand further investigations are necessary to evaluate the carcinogenicrisk of adriamycin treatment.     

Impact of tumor cell kinetics on the outcome of induction chemotherapy in oral carcinoma patients

Pretherapeutic S-phase fractions of 68 carcinomas of the tongue and the floor of mouth were analysed by DNA flow cytometry immediately before intra-arterial induction chemotherapy with cisplatin and epirubicin or 5-fluorouracil. Patients with diploid tumors had an excellent 5-year survival rate of 89% in contrast to only 31% in the aneuploid group. Cell proliferation had no impact on the outcome of diploid cases. Node-positive patients with aneuploid tumors had a poor 18% 5-year survival rate, independent of S-phase fractions. Survival was significantly worse in nodenegative patients with high proliferating aneuploid tumors (45%) compared to the low-proliferative N-0 group (83%).     

High susceptibility of analbuminemic rats to neurogenic tumor induction by transplacental administration of N-ethyl-N-nitrosourea.

The susceptibilities of Nagase analbuminemic rats (NAR) and control Sprague-Dawley rats (SDR) to N-ethyl-N-nitrosourea (ENU) were compared. In Experiment I, the rats were given daily subcutaneous injections of 10 mg/kg of ENU for a week from 4 weeks of age. In Experiment II, mother rats were given a single subcutaneous injection of 60 mg/kg of ENU on day 17 of pregnancy and tumor development in their offspring was examined. In Experiment I, the incidence of neurogenic tumors was slightly, but not significantly, higher in NAR than in control rats. In Experiment II, the incidence of total tumors including neurogenic tumors was significantly higher in NAR (40/43, 93.0%) than in SDR (13/61, 21.3%). NAR showed particularly high susceptibility to induction of neurogenic tumors (34/43, 79.1%) and renal tumors (15/43, 34.9%). In an attempt to elucidate the underlying mechanisms of the increased susceptibility of NAR to ENU, O6-ethylguanine, a major premutagenic ethylated DNA adduct, was quantitated in fetal brain DNA of NAR and SDR after a pulse exposure to 60 mg/kg ENU. No significant difference in the initial formation or subsequent repair of O6-ethylguanine was observed in the two strains, indicating that abnormality at some later stage(s) of chemical carcinogenesis may lead to the increased susceptibility of NAR to induction of neurogenic tumors.     

Rat and mouse forestomach tumors induced by chronic oral administration of styrene oxide

Styrene oxide (CAS: 96-09-3) was administered in corn oil by gavage three times a week at two dose levels to groups of 52 male and 52 female F344 rats and 52 male and 52 female B6C3F1 mice for 2 years, after which the surviving animals were killed and examined histopathologically. The doses given to rats were 550 and 275 mg/kg (body wt) per treatment; in mice the two doses were 750 and 375 mg/kg (body wt) per treatment. The main pathologic findings were high incidences of squamous cell carcinomas or papillomas of the forestomach in both sexes of both rats and mice. These neoplasms were virtually absent from the 52 controls of either sex of both species given parallel treatment with corn oil alone. There was a statistically significant increase in the incidence of hepatocellular neoplasms in male mice receiving 375 mg styrene oxide/kg. Styrene oxide is carcinogenic to both sexes of F344 rats and B6C3F1 mice when administered orally in corn oil.     

The induction of bladder tumors in F344 rats by intravesicular administration of some nitrosamines

Three nitrosamines, metabolically related and formed in vivo from the bladder carcinogen nitrosomethyl-n-octylamine, were administered to groups of 12 female F344 rats by intraurethral instillation twice a week for 30 weeks. All three compounds induced tumors in the urinary bladder. Nitrosomethyl-2-oxopropylamine at 10 mg/ml was the most potent, causing death of half of the animals with tumors at 43 weeks, following a total dose of 1.0 mmol; most of the rats also had tumors of the nasal mucosa, and there were some tumors of the kidney and kidney pelvis. Nitrosomethyl-2-hydroxypropylamine at 10 mg/ml (total dose 1.0 mmol) was much less effective, the median week of death being 83 weeks. In addition to bladder tumors, this group had tumors of the nasal mucosa, esophagus, and kidney. Nitrosomethyl-3-carboxypropylamine at 75 mg/ml and a total dose of 6.2 mmol per rat induced a high incidence of bladder tumors and tumors of the kidney pelvis, but not tumors of the nasal mucosa; the median week of death for this group was 55 weeks. It is concluded that nitrosomethyl-n-alkylamines that induce bladder tumors by oral administration to rats are metabolized to nitrosomethyl-3-carboxypropylamine, which is excreted in the urine and further metabolized to nitrosomethyl-2-oxopropylamine, the proximate bladder carcinogen.     

Potential improvement of tumor control probability by induction chemotherapy for advanced nasopharyngeal carcinoma

PURPOSE: To assess the reduction of tumor bulk and improvement of tumor control probability (TCP) by using induction chemotherapy for advanced nasopharyngeal carcinoma (NPC). MATERIALS AND METHODS: From February to December 2005, 20 patients with Stage III-IVB NPC were treated with induction-concurrent chemotherapy and intensity-modulated radiotherapy with accelerated fractionation. Combination of cisplatin and 5-fluorouracil was used in the induction phase and single agent Cisplatin in the concurrent phase. All patients were irradiated at 2Gy per fraction, 6 daily fractions per week, to a total dose of 70Gy. RESULTS: Nineteen (95%) patients completed all 3 cycles of induction chemotherapy and 90% had 2 cycles of concurrent chemotherapy. Induction chemotherapy achieved significant down-staging of T-category in 35% of patients (p=0.016) and reduction of gross tumor volume (GTV_P) from 55.6 to 22.9cc (mean 61.4%, p<0.001). Although the mean radiation dose did not show any substantial change, the volume within GTV_P that failed to reach 70Gy was reduced from 10.2% to 3.8% (p=0.017). The estimated local TCP increased from 0.83 to 0.89 (p=0.002). CONCLUSIONS: Induction chemotherapy using cisplatin-5-fluorouracil could significantly reduce tumor bulk leading to potential improvement in tumor control.     

Preoperative induction chemotherapy followed by concurrent chemoradiotherapy in advanced carcinoma of the oral cavity and oropharynx

BACKGROUND: Combined modality therapy plays a central role in the management of advanced head and neck tumors. The objective of our Phase II study was to determine the feasibility, toxicity, and clinical and pathologic response of preoperative induction chemotherapy, followed by concurrent chemoradiotherapy in patients with Stage III or IV squamous cell carcinoma according to the American Joint Committee on Cancer Staging of the oral cavity and oropharynx with no distant metastases. METHODS: After staging, 62 patients with locally advanced carcinoma of the oral cavity and oropharynx were treated preoperatively with chemotherapy (1 cycle of cisplatin and 5-fluorouracil [P-5FU]) followed by concurrent chemoradiotherapy (3 cycles of P-5FU combined with radiotherapy, 60 grays [Gy] given in 33 fractions of 1.8 Gy). After evaluation, patients underwent surgery either as a diagnostic (biopsy) or therapeutic procedure (resection of the primary tumor and/or the neck). Surgery was performed with the intent to spare organ function. RESULTS: Grade 3-4 mucositis was observed in 37 patients (59%). Overall clinical response was obtained in 87%, and the complete clinical response rate was 50%. Surgery was performed in 53 patients, 50 at the primary tumor site (11 biopsies, 14 marginal excisions, and 25 wide excision) and 46 patients had neck dissection. Pathologic complete remission was observed in 29 patients (46%). After a median follow-up of 39 months, locoregional control rate was 76%, estimated 3-year disease free survival rate was 73% (+/- 4%), and estimated 3-year overall survival rate was 76% (+/- 4%). CONCLUSIONS: This intensive multimodality treatment is feasible, and toxicity is significant but tolerable. The treatment results appear promising and durable. Organ-preserving surgery can be performed in many patients.     

Endometrial carcinogenesis induced by concurrent oral administration of ethylenethiourea and sodium nitrite in mice

Endometrial carcinogenesis induced by concurrent oral administrationof ethylenethiourea (ETU) and sodium nitrite (NaNO₂ was investigatedin ICR (Crj:CD-l) femalemice. A mixed solution of ETU (100 mg/kg)and NaNO₂ (70 mg/kg) was given to animals orally once a weekfor up to 6 months and all surviving animals were killed at12 months of study. During the study, estrous cycle was monitoredby vaginal smear and five or 10 selected animals were subjectedto interim killing at 3 month interval to observe time-relatedcarcinogenic responses of the uterus. Treatment with ETU andNaNO2 resulted in development of endometrial adenocarcinomasin the uterine horn and the incidence reached 42% in the survivinganimals at 12 months. Prior to the development of the tumor,atypical hyperplasia of endometrial glands was frequently observedand regarded as the precancerous lesion. Immunohistochemistryfor bromodeoxyuridine (BrdU) incorporation revealed higher labelingindices in both hyperplastic and neoplastic endometrial glandularcells, and the index in the adenocarcinoma was more than 20%on average at any stage of the estrous cycle. Overexpressionof p53 protein, which is frequently demonstrated in virulentphenotypes of human corpus cancers, was seen in three out ofeight (38%) adenocarcinomas, but not in the atypical hyperplasiaor normal endometrial glands. There were no treatment-relatedchanges in the estrous cycle on vaginal smears at any intervalof the study. The analyses for plasma ovarian hormones at 12months disclosed a marked depression of progesterone in thetreated animals, while the 17ß-estradiol (Ex) levelwas comparable to the controls. These results suggest that endometrialcarcinogenesis by ETU and NaNO₂ could be initiated with atypicalhyperplasia of the endometrial gland and a decrease in plasmaprogesterone level may play an important role in the developmentof endometrial carcinogenesis. In addition, inactivation ofthe p53 gene may play a significant role in the malignant transformationof endometrial epithelial cells in mice.     

The enhancement of tumor radioresponse by combined treatment with cepharanthine is accompanied by the inhibition of DNA damage repair and the induction of apoptosis in oral squamous cell carcinoma

In the present study, we investigated whether treatment with cepharanthine, a biscoclaurine alkaloid extracted from Stephania?cepharantha improves the response to radiotherapy in the oral squamous cell carcinoma (OSCC) cell lines, HSC2, HSC3 and HSC4. We examined the potential mechanisms that may contribute to the enhanced radiation response induced by cepharanthine. Growth inhibition was observed in?vitro with radiation or cepharanthine. A co-operative anti-proliferative effect was obtained when cancer cells were treated with cepharanthine followed by radiation. Cepharanthine also promoted the mitotic death of 3?cell lines by radiation. The results from DNA damage repair analysis in the cultured OSCC cells demonstrated that cepharanthine had a strong inhibitory effect on DNA double-strand break (DSB) repair after radiation. The combined treatment of cepharanthine and radiation led to an increase in the sub-G1 peak as shown by flow cytometry, and markedly induced apoptosis through the activation of caspase-3. Tumor xenograft studies demonstrated that the combination of cepharanthine and radiation caused growth inhibition and tumor regression of OSCC tumors in athymic mice; tumor volume was reduced from 765.7 to 226.3?mm3 in HSC2 cells (p<0.01), 391.6 to 43.7?mm3 in HSC3?(p<0.01), and from 572.6 to 174.2?mm3 in HSC4 cells?(p<0.01). In addition, combined therapy markedly increased tumor cell apoptosis. Overall, we conclude that cepharanthine enhances tumor radioresponse by multiple mechanisms that may involve the induction of apoptosis and the inhibition of DNA DSB repair after exposure to radiation.