[Metformin effect on urethane-induced tumorigenesis in mice].

Sixty one male 129/Sv mice were exposed to a single intraperitoneal injection of 1 g per kilo of urethane dissolved in 0.9% normal saline. Starting the next day from the injection the study group mice were given 1200 mg metformin per liter of drinking water 5 days a week for 26 weeks. The control group mice received pure drinking water. Six months after the urethane treatment the mice were killed and the morphology samples were taken. Twenty five of 31 (96.7%) control group mice developed tumors (lung adenomas and thymic lymphomas), while tumor development was observed in 25 of 31 (80.7%; p<0.05) mice exposed to metformin. Solid or trabecular lung adenomas developed in 90% of the control group mice and in 77% of the metformin group mice (p=0.119). Therefore, it is a first evidence of tumor-inhibitory effect of metformin in mice.

Expression of circadian Per1 and Per2 genes in the liver and breast tumor tissues of HER2/neu transgenic mice of different age.

The expression of Per1, Per2, and Cry1 circadian genes in the liver and breast tumors were studied by real-time PCR in FVB/N mice of different age transfected with HER-2/neu gene. The expression of Per1 and Per2 genes in breast tumor tissue decreased in comparison with their expression in the lever. The expression of these genes decreased with age in both the liver and tumor tissue.

[The effect of mithochondria targeted antioxidant SkQ1 on aging, life span and spontaneous carcinogenesis in three mice strains].

Female outbred SHR mice, inbred 129/Sv mice and transgenic HER-2/neu mice were given mitochondria targeted antioxidant SkQ1 with drinking water in the various doses (0,5-2500 nmol/kg day) since the age of 2 months, whereas control animals received tap water. Age-related dynamics of the body weight and temperature, the amount of drinking water and consumed food, estrous function, as well as parameters of the life span and spontaneous carcinogenesis were estimated. As compared with controls, no difference in the parameters of body weight and temperature or amount of consumed food and water in the treated mice of all studied mice strains was revealed. In SkQ1-treated SHR mice, the tendencies of inhibition of the age-dependent disturbances of estrous function and aging appearance were observed. No effect of SkQ1 on estrous function and external view in inbred and transgenic mice was shown. SkQ1 treatment significantly decreased locomotor activity (in 12-15 months old SHR and 129/Sv mice) and exercise tolerance in old (20 months) SHR mice. The treatment with SkQ1 (0,5-50 nmol/kg day) increased parameters of the life span in SHR mice (mean life span, mean life span of the last 10% of survival, median and maximum life span) without significant effect on the life span in 129/Sv and HER-2/neu mice. There was no reliable difference in tumor development in all SkQ1-treated mice strains as compared with the control. The drug considerably inhibited the incidence of age-associated non-tumor pathology in SHR mice. Our data suggest geroprotective activity of SkQ1, and a lack of toxic or carcinogenic activities during long term use.

[Features of carcinogenesis and aging in knockout male mice PARP-1].

Poly(ADP-ribosyl)ation polymerase-1 (PARP-1) is a major factor of DNA repair. Age-related parameters such as body weight and blood cholesterol in knockout male mice PARP-1 were more pronounced as compared with controls. Mean life span was shorter (486 +/- 31.7 and 723 +/- 22.6 days, respectively, (p = 0.000005) while initial risk of death (beta) was 8 times as high as in mice PARP-1(+/+). Mean latency of all tumors in knockout and control mice was 656 +/- 43.5 and 782 +/- 33.8 days, respectively, (p < 0.05). Among the most frequent neoplasms were tumors of the liver (experimental--22% and control--8%, respectively) (p = 0.03) and lungs (8% and 12%, respectively). Hence, mice PARP-1(-/-) revealed certain typical charhacteristics of accelerated aging, shorter life span, earlier carcinogenesis and higher rates of liver tumor incidence as compared with mice PARP-1(+/+). Our evidence highlights the role of DNA repair in carcinogenesis and aging.

[Diethylnitrosamine-induced carcinogenesis in PARP-1(-/-) and PARP-1(+/+) mice].

Our study is concerned with comparative analysis of diethylnitrosamine (DENA)-induced carcinogenesis in PARP-1 knock-out female mice PARP-1(-/-) and wild type animals PARP-1(+/+). No difference was recorded in relation to total tumor incidence (88 and 95%, respectively): cardia (87 and 84%, respectively), liver (80 and 66%, respectively). However, experimental animals PARP-1(-/-) tended to reveal incidence of cardia tumors with invasion as deep as the serosa higher than in PARP-1(+/+) mice (100 and 81%, respectively) and metastases to the liver and lung--27 and 7%, respectively. Relative incidence of angiosarcoma and holangiocarcinoma among liver tumors from PARP-1(-/-) mice was higher than that in wild type mice. Hence DENA induced the most aggressive tumors in PARP-1(-/-) knockout mice more often than in PARP-1(+/+) ones. Our results confirm the significance of the role of DNA repair in carcinogenesis.

[The effects of Celebrex on mammary tumorigenesis and aging in HER2/neu transgenic mice].

It is well known that cyclooxygenase-2 (COX2) plays an important role in the development of many tumors including breast cancer. Our study was concerned with evaluating the effects of the selective COX2 inhibitor, celecoxib, on mammary tumorigenesis and aging in HER2/neu transgenic mice (24). Celecoxib (celebrex) 25 mg/kg was administered 5 times a week from the age of 2 months. Twenty-four intact females were in control. Monitoring kept track of tumor detection time, size, presence of lung metastases, food and water consumption, estral function, body weight and temperature. No significant differences between the two groups were reported as far as life-span, tumor growth rate, size and number of metastases to the lung is concerned. To sum up, celecoxib treatment failed to produce any significant effect on carcinogenesis in HER2/neu transgenic mice.

Mitochondria-targeted plastoquinone derivatives as tools to interrupt execution of the aging program. 5. SkQ1 prolongs lifespan and prevents development of traits of senescence.

Very low (nano- and subnanomolar) concentrations of 10-(6'-plastoquinonyl) decyltriphenylphosphonium (SkQ1) were found to prolong lifespan of a fungus (Podospora anserina), a crustacean (Ceriodaphnia affinis), an insect (Drosophila melanogaster), and a mammal (mouse). In the latter case, median lifespan is doubled if animals live in a non-sterile vivarium. The lifespan increase is accompanied by rectangularization of the survival curves (an increase in survival is much larger at early than at late ages) and disappearance of typical traits of senescence or retardation of their development. Data summarized here and in the preceding papers of this series suggest that mitochondria-targeted antioxidant SkQ1 is competent in slowing down execution of an aging program responsible for development of age-related senescence.

[Specific features of spontaneous carcinogenesis and survival in female mice 129/Sv PARP-1+].

Spontaneous carcinogenesis and survival were compared in female mice 129/Sv PARP-1+ and PARP-1++ controls. Survival of all animals, including that of the last 10% of mice PARP-1+ (p<0.0002), was relatively lower. It was matched by a significant rise in aging rate. Spontaneous tumor incidence was identical in both groups, although experimental animals revealed tumors at an earlier stage (612+19.2 and 706+17.6 days, respectively, (p<0.0002). The death rate of mice PARP-1+ was 67% as compared with controls (47%) (p<0.05). Tumors of uterus, ovary, liver, lung, mammary gland and soft tissues as well as malignant lymphoma were detected. Malignant tumors contributed 72% among experimental animals versus 49% in control (p<0.05). Those differences were mostly observed among uterine malignancies, adenocarcinomas of the lung and hepatocellular carcinomas. Hence, the switching-off of PARP-1+ involved accelerated aging, shorter survival and earlier and more aggressive tumor development which is in agreement with the existing views on the role played by DNA reparation in mechanisms of carcinogenesis and aging.

[Poly(ADP-ribosa)polymerase--the relationships with life span and carcinogenesis].

Poly(ADP-ribose) polymerases (PARP) is enzyme family repairing single or double DNA strand breaks induced by different alkylating agents, ionizing- or UV-irradiation as well as by oxidative stress. Poly(ADP-ribose) polymerase-1 (PARP-1) is the most studied enzyme involved in a number of pathways including DNA replication and repair, recombination, gene transcription, cell proliferation and death. A positive correlation between the PARP-activity and the life span of different mammalians has been detected. PARP inhibition in vitro with inhibitors of PARP activity (3-aminobenzamide, nicotinamide, picolinamide e.t.c.) in cells from wild type or PARP-1(-/-) mice was followed by high genomic instability (i.e. aneuploidy, gene amplifications and deletions, micronuclei formation, sister chromatic exchange, cell ploidy and centrosome number increase) and increased sensitivity to mutagens. Life span reduction, latency period of spontaneous tumors development shortening and the increase in susceptibility to carcinogens have been observed in PARP-knockout mice. Treatment with PARP inhibitors stimulated chemical and radiation carcinogenesis in animals. The PARP-1(-/-) mice being additionally disrupted in WRN, p53, DNA-PKcs or Ku80 genes the promotion of spontaneous carcinogenesis was observed as compared with a single gene-disrupted mice. Available data suggest a significant role of PARP in maintenance of genomic stability, preventing of aging and carcinogenesis.

Metformin decelerates aging and development of mammary tumors in HER-2/neu transgenic mice.

Transgenic FVB/N female mice carrying HER-2/neu mammary cancer gene received metformin (1200 mg/liter) with drinking water 5 days a week starting from the age of 2 months until natural death. Metformin slightly reduced food consumption, but did not change water consumption and dynamics of weight gain. Mean life span of mice increased by 8% (p<0.05), in 10% long-living mice it was prolonged by 13.1%, and the maximum life span was prolonged by 1 month under the effect of metformin in comparison with the control. The rate of populational aging decreased by 2.26 times. The total incidence of mammary adenocarcinoma and their multiplicity did not change under the effect of metformin, while the latency of tumor development increased and the mean diameter of tumors decreased. Hence, we first demonstrated a geroprotective effect of metformin and its suppressive effect towards the development of mammary tumors.