Phenozan, a Synthetic Phenolic Antioxidant, Inhibits the Development of Spontaneous Tumors in Rats and Mice.

Synthetic phenolic antioxidant ß-(4-hydroxy-3,5-di-tert-butylphenyl) propionic acid, named phenozan, is a potential antiepileptic drug. In pre-clinical trials this substance did not manifest any toxicity, and also inhibited the development of some spontaneous tumors in animals. The purpose of this study was to evaluate inhibiting effect of phenozan on spontaneous carcinogenesis in rats and mice. In experiments with rats LIO and mice SHR of local breeding, with high spontaneous tumor incidence, phenozan was dissolved in sunflower oil and administered by gavage in therapeutic dose 5 mg/kg 3 times per week for 18 months. There were no any signs of toxicity and differences in weight of animals during the phenozan treatment compared with the control (sunflower oil). Phenozan significantly reduced the overall incidence and multiplicity of all tumors but only multiplicity of malignant tumors, compared with the control. Moreover a significant decrease of overall incidence and multiplicity was observed in pituitary and breast tumors in females and only overall multiplicity of tumors of pituitary and lymphoid tissue in males. In mice phenozan reduced overall incidence and multiplicity of lung tumors (in females) and also overall multiplicity of all tumors (in females) and only malignant tumors (in males). These findings allow us to classify phenozan as anticarcinogenic agent. Anticarcinogenic activity of phenozan is important because clinical study of this drug as the possible antiepileptic drug goes along and it is known that such drugs are designed for long-term use.

[Relationship between benign prostatic hyperplasia and prostate cancer: new opportunities for prostate cancer chemoprevention].

In a review article the relationship between benign prostatic hyperplasia (BPH) and prostate cancer (PC) has been conducted. Epidemiological data on increasing the risk of PC in patients with BPH are presented. There are discussed common for BPH and PC constitutional, food, and life style etiologic factors and also common for the both diseases pathogenetic factors such as androgens, inflammation, metabolic syndrome. Pharmaceutical drugs and natural agents that have unidirectional therapeutic and preventive effect on BPH and PC are presented. Results of experimental studies of the authors to prove the link between BPH and PC are presented. It is concluded that BPH is a risk factor for PC and, ideally, drugs for the treatment of BPH should have a chemo preventive effect on PC.

[Intraperitoneal chemotherapy--a method of improving treatment effectiveness in ovarian cancer].

The study or antitumor effects of dioxadet, cisplatin, melphalan, paclitaxel, mitomycin C, cyclophosphamide and gemcitabine at intraperitoneal (i.p.) and intravenous (i.v.) administration as monochemotherapy and polychemotherapy in a rat model of ascitic ovarian cancer was carried out in 244 female Wistar rats. Ovarian cancer was transplanted i.p. at a number of 1 x 10(7) tumor cells. The drugs were administered once in 48 hours after ovarian cancer transplantation i.p. or i.v. for monotherapy--in maximum tolerated doses, for i.p. polychemotherapy--in half doses from maximum tolerated doses. Antitumor effects of the treatment were estimated in increase in median survival time (MST) compared to control rats who were administered saline i.p. At i.p. administration dioxadet, cisplatin and melphalan increased MST by 79%, 88% and 144%, respectively, while at i.v. administration these drugs didn't affect MST. Mitomycin C and paclitaxel had stronger antitumor action at i.v. administration increasing MST by 152% and 81%, respectively, while at i.p. administration these drugs increased MST by 35 and 45%, respectively. Combinations dioxadet + cisplatin, dioxadet + cyclophosphamide and dioxadet + paclitaxel at i.p. administration increased MST by 305%, 277% and 133%, respectively, and had additive antitumor action compared to mono-effects of these drugs. Gemcitabine and combination dioxadet + gemcitabine at i.p. administration didn't significantly affect survival of rats with ovarian cancer. Intraperitoneal monochemotherapy and polychemotherapy could be more effective in the treatment of peritoneal carcinomatosis from ovarian cancer compared to systemic administration of the drugs.

[Therapeutic activity of gemcitabine in intracranial tumors].

Gemcitabine is known to exert a therapeutic effect on brain tumors despite the limited permeability of the blood-brain barrier (BBB). In our experimental research single intraperitoneal (i.p.) injection of gemcitabine 25 mg/kg provided increase in median survival of mice with intracranially transplanted Ehrlich carcinoma by 41-89% (p < 0.001). In this experimental model i.p. administration of gemcitabine (permeability of the BBB of less than 10%), carmustine (good permeability of the BBB), cyclophosphamide (poor permeability of the BBB) and cisplatin (doesn't penetrate through the BBB) increased median survival of mice by 88% (p < 0.001), 59% (p = 0.001), 35% (p = 0.005) and 18% (p = 0.302) respectively. Considering strong correlation between antitumor activity of the drugs (carmustine, cyclophosphamide and cisplatin) and their permeability of the BBB, efficacy of gemcitabine in intracranial tumors could be due to its wide range of therapeutic doses.

Chemoprevention of mammary, cervix and nervous system carcinogenesis in animals using cultured Panax ginseng drugs and preliminary clinical trials in patients with precancerous lesions of the esophagus and endometrium.

The anticarcinogenic effects and mechanisms of the biotechnological drugs of Panax ginseng C.A. Meyer cultivated in Russia, bioginseng, panaxel and panaxel- 5, were studied. Bioginseng was produced from a tissue culture of ginseng root cultured on standard medium, whereas panaxel and panaxel-5 were produced from ginseng tissue root cultures using standard mediums enriched with 2-carboxyethylgermanium sesquioxide and 1-hydroxygermatran-monohydrate respectively. All three ginseng drugs inhibited the development of mammary tumors induced by intramammary injections of N-methyl-N-nitrosourea (MNU) in rats, the development of the brain and spinal cord tumors induced by transplacental administration of N-ethyl-N-nitrosourea (ENU) in rats, and the development of uterine, cervical and vaginal tumors induced by intravaginal applications of 7,12-dimethylbenz(a)anthracene (DMBA) in mice. The ginseng drugs induced the cytotoxic activity of macrophages in mice, enhanced T-lymphocyte rosette formation in guinea pigs exposed to cyclophosphamide, and stimulated the production of thyroid hormones in rats. These mechanisms may contribute to the anticarcinogenic action of the ginseng drugs. The organic germanium compounds present in panaxel and panaxel-5 did not potentiate the anticarcinogenic or immuno- stimulatory effects as much as biogeinseng. Preliminary clinical trials with panaxel and bioginseng were carried out in patients with precancerous lesions of the esophagus and endometrium. Panaxel was found to have a strong therapeutic effect in patients suffering from chronic erosive esophagitis. Bioginseng induced the regression of adenomatous-cystic hyperplasia of the endometrium in some patients. Thus, we conclude that the drugs of ginseng appear to hold considerable promise for future cancer chemoprevention.

Study of the post-natal effects of chemopreventive agents on ethylnitrosourea-induced transplacental carcinogenesis in rats. II. Influence of low-molecular-weight polypeptide factors from the thymus, pineal gland, bone marrow, anterior hypothalamus, brain cortex and brain white substance.

The influence of the polypeptide factors extracted from thymus, pineal gland, bone marrow, anterior hypothalamus, brain cortex or brain white substance on N-ethyl-N-nitrosourea (ENU)-induced transplacental carcinogenesis was studied in rats. ENU was given to pregnant rats as a single i.v. exposure at a dose of 75 mg/kg body weight on the 21st day of gestation. The polypeptide factors were given to the offspring as a series of s.c. injections, at a dose of 0.5 mg/rat/day, starting at one or 2.5 months of age and continuing throughout the whole of post-natal life. ENU induced tumors of the brain, spinal cord, peripheral nerves and kidneys in 94-98% of the offspring exposed to the carcinogen, with an average number of 2.3-2.6 tumors per rat, and an average survival time of 294 days. Post-natal thymus factor or pineal gland factor administration was followed by an increase in mean lifespan of approximately 2 months and a significant decrease (P < 0.05) in the total tumor number per tumor-bearing rat, as well as the incidence and multiplicity of spinal cord tumors. Pineal gland factor also decreased the incidence of peripheral nerve and kidney tumors and their number per tumor-bearing rat. Brain cortex factor and brain white substance factor treatment was followed by a decrease in total tumor multiplicity of 1.2- to 3.3-fold, and a decrease in incidence of brain tumors of 10 to 33% per rat in comparison to the controls. Brain cortex factor also decreased the total tumor incidence. At the same time, brain white substance factor administration increased the incidence of peripheral nerve tumors and decreased the mean lifespan. Both bone marrow factor and anterior hypothalamus factor did not have any modifying effects on any of the ENU-induced tumors and mean lifespan. Thus, our results show the possibility of attenuation of transplacental ENU-induced carcinogenesis with post-natal administration of some polypeptide substances.

Study of post-natal effect of chemopreventive agents on ethylnitrosourea-induced transplacental carcinogenesis in rats. III. Inhibitory action of indomethacin, voltaren, theophylline and epsilon-aminocaproic acid.

The influence of the arachidonic acid metabolism inhibitors, indomethacin and voltaren; an inhibitor of phosphodiesterase activity, theophylline and the protease inhibitor epsilonaminocaproic acid (EACA) on N-ethyl-N-nitrosourea (ENU)-induced transplacental carcinogenesis was studied in rats. ENU was given to pregnant rats as a single i.v. exposure at a dose of 75 mg/kg body weight on the 21st day after conception. Indomethacin and voltaren (20 p.p.m. in drinking water), theophylline (0.01% in diet) and EACA (1000 p.p.m. in drinking water) were given to the offspring throughout their post-natal life until all survivors were killed at 12 months. In the ENU-only control groups, 100% of the offspring developed tumors of brain, spinal cord, peripheral nervous system or kidneys, with a total average number of 3.1 tumors per rat. The most marked inhibitory effect was exerted by theophylline, which significantly decreased the incidence and multiplicity of total tumors, and at all main sites selectively (brain, spinal cord, peripheral nerves and kidneys). It also prolonged average survival time of the offspring. Indomethacin and voltaren significantly decreased total tumor incidence and multiplicity and brain tumor incidence and multiplicity. Indomethacin also decreased kidney tumor multiplicity and voltaren diminished spinal cord tumor multiplicity. EACA decreased multiplicities of total, brain, peripheral nerve and kidney tumors, and diminished the incidence of brain tumors. These chemopreventive agents decreased tumor incidences 20-33% and tumor multiplicities 1.4-2.7 times, compared with the ENU-only controls.

Study of postnatal effects of chemopreventive agents on offspring of ethylnitrosourea-induced transplacental carcinogenesis in rats. I. Influence of retinol acetate, alpha-tocopherol acetate, thiamine chloride, sodium selenite, and alpha-difluoromethylornithine.

We studied the influence of the vitamins retinol acetate, alpha-tocopherol acetate and thiamine chloride; the antioxidant sodium selenite and an inhibitor of polyamine biosynthesis, alpha-difluoromethylornithine, on the offspring of transplacental carcinogenesis by ethylnitrosourea in rats. Ethylnitrosourea was given to pregnant rats as a single i.v. injection, at a dose of 75 mg/kg body wt. or 5.5 mg/kg body wt., on the 21st day after conception. Retinol, tocopherol or thiamine was added to the diet, and selenite and alpha-difluoromethylornithine to drinking water of the offspring throughout their postnatal life at moderate doses. In control groups, ethylnitrosourea induced tumors of brain, spinal cord, peripheral nervous system and kidneys in the offspring. alpha-Difluoromethylornithine exerted a slight inhibitory effect; this agent decreased the total tumor multiplicity and the multiplicity of peripheral nervous system tumors and also prolonged survival time. Retinol, tocopherol, thiamine and selenite did not influence the development of the transplacentally-induced tumors.

The stimulating effect of acetic acid, alcohol and thermal burn injury on esophagus and forestomach carcinogenesis induced by N-nitrososarcosin ethyl ester in rats.

Five groups of outbred white male rats were given N-nitrososarcosin ethyl ester (NSEE) i.g. for 4 or 6 months at a daily dose of 50 mg/kg of body wt. 5 days/week. Some groups of animals were given a 3% water solution of acetic acid or a 40% solution of ethanol i.g. for 8 months from the beginning of the experiment. The remaining groups of these rats received controlled local thermal burn injury of the esophageal mucosa 15 days before the beginning of the experiment. Acetic acid solution increased the multiplicity of benign and malignant tumors as well as carcinoma incidence in the esophagus. Ethanol in combination with NSEE did not influence carcinogenesis in the esophagus but increased the incidence of leukokeratosis and the multiplicity of forestomach papillomas. In rats treated with NSEE after thermal burn injury, a significant increase in the frequency and multiplicity of papillomas was found in the burn zone.

Influence of hormonal disturbances on transplacental and multigeneration carcinogenesis in rats.

Thyroid dysfunction (induced by thyroidectomy or administration of thyroxin and methylthiouracil) during the postnatal period was tested as a modifying factor on carcinogenesis induced transplacentally by N-methyl-N-nitrosourea (MNU). It resulted mainly in inhibition of tumours of the nervous system and kidney in rats of two subsequent generations, but thyroid carcinogenesis was increased. Postnatal disturbance of oestrous function (induction of persistent oestrus syndrome) in female rats increased the incidence of tumours of the central nervous system induced transplacentally by MNU or 7,12-dimethylbenz[a]anthracene. No such effect was seen in animals of the F2 generation.

Fetal macrosomia and sex differences in the influence of modifying factors on transplacental carcinogenesis.

Differences in cancer frequency between men and women are well known. Sexual dimorphism is also observed in the development of some experimental tumours, including those induced transplacentally. Differences in the production and binding of sex hormones by target tissues are evidently not the only cause of sexual dichotomy in the action of modifying factors on transplacental carcinogenesis. In our experiments, the average weight of newborn rats treated with glucose during intrauterine life from day 7 to 20 of gestation exceeded that of control animals, and rats exposed transplacentally to N-methyl-N-nitrosourea (MNU) on day 21 of gestation in combination with glucose (beginning from day 7 of prenatal life to 1.5 months after delivery) had a significantly increased tumour frequency. In males, there was an increased frequency of neoplasms of the nervous system and kidneys, which are typical transplacental carcinogenic effects of MNU; however, in females, neoplasms were induced in other organs and tissues, mainly the mammary gland and pituitary body. Thus, fetal macrosomia acts as a modifying factor in transplacental carcinogenesis also by determining the tumour spectrum in females and males and not only in increasing tumour frequency. The possible causes of these differences and perspectives for further research are discussed.

Carcinogenic effect of N-nitrosotriethylurea in single administration to female rats.

N-Nitrosotriethylurea (NTEU) was administered once into the stomach or intravenously to outbred female rats. The rats given NTEU by oral administration developed malignant tumours of the mammary gland, uterus and liver. The rats exposed to NTEU by i.v. administration developed tumours of the mammary gland and ovaries. NTEU accelerated the appearance of tumours which are normally characteristic of the rat stock used (tumours of the pituitary, thyroid, adrenal cortex, fibroadenoma of the mammary gland, endometrial polyps.

Glucose consumption, newborn weight and nitrosomethylurea transplacental carcinogenesis in rats.

This study used rats bred at the Petrov Research Institute of Oncology. On the 21st day of pregnancy N-nitrosomethylurea (NMU) (20 mg/kg) was administered to the animals intraperitoneally. From the 7th day of pregnancy experimental rats were treated with 10% glucose solution instead of drinking water, and during 1.5 months after delivery the rats of this group and their progeny received 5% glucose solution. The present work has revealed an increase of fetal weight in pregnant rats treated with glucose. A significant increase of tumor frequency was detected in the progeny of these rats. In the male progeny, tumors of the nervous system and kidneys, typical for NMU, predominated and in females, tumors of other organs and tissues, particularly the mammary gland, pituitary body and hemopoietic system, predominated. This paper discusses a possible mechanism of the modifying effect of glucose on transplacental carcinogenic action of NMU.

Role of the maternal organism in transplacental carcinogenesis.

The maternal organism plays a highly important role in transplacental carcinogenesis, since for carcinogens in the bloodstream of the mother to reach the fetus, they must cross several barriers, the first of which is the placenta. Some types of compounds require metabolic activation in the maternal organism, in the fetus and even sometimes in the placenta. Thus, four main pathways can be hypothesized by which substances exert a carcinogenic effect on the fetus. Most carcinogens can cross the placenta; data confirm that this process consists of simple diffusion or - in the case of high doses - facilitated diffusion. That carcinogens may be detoxified in the maternal organism is confirmed by experiments on activation of enzyme systems and on caesarean deliveries. Species and strain specificities are characteristic of transplacental carcinogenesis and are manifested in organotropism. Organotropism in transplacental carcinogenesis is determined by genetic predisposition, cell differentiation and proliferative activity in the target tissues. For indirect carcinogens, the level of metabolizing enzymes is also important.

Transplacental carcinogenic effect of n-nitrosoethylurea in dogs.

During the late period of pregnancy (on the 50th and 53rd days post coitum) 2 dogs were injected intraperitoneally with 100 mg/kg (a single administration) of nitrosoethylurea. Nine puppies were born. During the 9 year period of observation no tumours were detected in mother-dogs. Three of 9 offspring developed the following tumours: brain haemangioblastoma (on the 526th day after administration), nephroblastoma and spleen angioleiomyoma (on the 845th day after administration) and adenoma of thyroid gland (after 7 years). Among other lesions 3 offspring-dogs developed polycystic kidneys. The revealed tumours of brain, kidney and spleen could be connected with transplacental carcinogenic effect of N-nitrosoethylurea (NEU), while neoplasms of these localizations and types rarely occur in dogs spontaneously.

Nephroblastoma and renal mesenchymal tumor induced in rats by N-nitrosoethyl- and N-nitrosomethylurea.

Rats treated prenatally with N-nitrosoethylurea or with N-nitrosomethylurea developed nephroblastomas, renal mesenchymal tumors and epithelial tumors (adenomas and carcinomas) of the kidneys. 15 nephroblastomas and 59 mesenchymal tumors were examined histologically. Nephroblastomas were encapsulated growths composed of dark cells, forming primitive tubules similar to those seen in the rat embryonal kidney and in human Wilms' tumor. Mesenchymal renal tumors showed an infiltrative growth and consisted of fibroblast-like cells, smooth muscles and angiomatous areas with the engulfed pre-existing tubules. These growths are similar to the mesenchymal renal tumors induced in the rat by N-nitrosodimethylamine. Nephroblastoma and mesenchymal renal tumor are considered to be separated entities, the first corresponsing to the epithelial variant of human Wilms' tumor and the second to congenital mesoblastic nephroma.

The inhibition of the transplacental blastomogenic effect of nitrosomethylurea by postnatal administration of buformin to rats.

N-Nitrosomethylurea (NMU) (20 mg/kg) was i.p. administered to rats on the 21st day of pregnancy. A decrease of glucose utilisation in the oral glucose tolerance test was found in 3 month old female progeny of NMU-treated rats. The serum insulin level did not differ from control, but serum cholesterol level was higher in offspring of NMU-treated rats. The ability of diethylstilboestrol to inhibit compensatory ovarian hypertrophy was decreased in female hemicastrated 3 month old rats whose mothers were treated with NMU. Postnatal administration of the antidiabetic drug buformin decreased the malignant neurogenic tumor incidence 3.5 times (to rats transplacentally treated with NMU).

Inhibition of DMBA-induced carcinogenesis by phenformin in the mammary gland of rats.

It is shown that daily oral administration of 5--10 mg of an antidiabetic biguanide-phenformin (phenethyl-biguanide) for 2.5--5 months suppressed DMBA-induced mammary tumour development in rats considerably. Phenformin-treated rats revealed-a tendency towards a decrease in blood insulin level (radioimmunoassay). The obtained data are regarded as additional evidence for the proposed existence of the same metabolic background of diseases of compensation, i.e. adult-onset diabetes, artherosclerosis and cancer, and suggest studies on possible antitumour effect of phenformin in man.

Some results and prospects of transplacental carcinogenesis studies.

Analysis of literary data and the author's findings have shown that the transplacental action of most of the compounds tested in experiments on rats manifested itself by a neurotropic carcinogenic effect. A marked neurotropism in transplacental carcinogenesis in rats is characteristic even for such drugs (e.g. dimethylbenzathracene) that have never induced neurogenic neoplasms in adult animals. To elucidate the relationship between teratogenesis and carcinogenesis the peculiarities of tumor development in brain against the background of malformations induced by combined transplacental treatment by methylnitrosourea (MNU) and ethylnitrosourea (ENU) in rats have been studied. Tumorigenesis was sharply inhibited by administration of ENU (on the 13th day) prior to MNU treatment (on the 15th day). There is reason to believe that the cytotoxic effect of MNU for microephaly results in the death of a considerable part of the cell population already transformed by ENU. In a special series of experiments characteristics of the permeability of polycyclic aromatic hydrocarbons through the placenta in rats have been specified.