Increase In Median Lifespan Research Articles

CMS121 Partially Attenuates Disease Progression in Mouse Models of Huntington's Disease.

There are currently no drugs that meaningfully slow down the progression of Huntington's disease (HD). Moreover, drug candidates against a single molecular target have not had significant success. Therefore, a different approach to HD drug discovery is needed. Previously we showed that the flavonol fisetin is efficacious in mouse and fly models of HD (Hum. Mol. Gen. 20:261, 2011). It is also effective in animal models of Alzheimer's disease (AD), ischemic stroke, and the CNS complications of diabetes, all of which share some pathological features with HD. Potent derivatives of fisetin with improved pharmacology were made that maintain its multiple biological activities (J. Med. Chem. 55:378, 2012). From 160 synthetic fisetin derivatives, one, CMS121, was selected for further study in the context of HD based on pharmacological parameters and its efficacy in animal models of AD. Both R6/2 and YAC128 mouse models of HD were used in these studies. We examined motor function using multiple assays as well as survival. In the R6/2 mice, we also looked at the effects of CMS121 on striatal gene expression. In both models, we found a slowing of motor dysfunction and an increase in median life span. Interestingly, in the YAC128 mice, the effects on the slowing in motor function loss became increasingly more pronounced as the mice aged. CMS121 also reduced HD-driven changes in the expression of genes associated with the proteasome and oxidative phosphorylation. Overall, these results suggest that CMS121 could provide some benefits for HD patients, particularly with regard to increasing health span.

Selective Breeding for High Intrinsic Exercise Capacity Slows Pan-Tissue Epigenetic Aging in Rats

Aerobic exercise capacity is strongly associated with longevity and reduction in all-cause mortality. Rats selectively bred for high intrinsic running capacity (HCR) compared with low (LCR), have between a 28-45% increase in median lifespan. It is not known whether the greater HCR survival is associated with slowed epigenetic aging. We hypothesized that HCR rats would express altered rates of pan-tissue DNA methylation corresponding to a slowed epigenetic clock (DNAmAge). Male and female LCR and HCR rats from generation 15-17 (n=22; chronological age=2.34±0.45 yrs (mean±SD)), generation 28 (n=20; 1.09±0.05 yrs) and generation 37 (n=20; 1.04±0.08 yrs) were included. DNA was extracted from skeletal muscle (n=61), cardiac muscle (n=60), adipose (n=61) and liver (n=61). DNAmAge was quantitated using the mammalian methylation array platform (~106k CpGs specific to brown rat). Three epigenetic clocks were used, previously trained on separate rat tissues, including dual species clocks that apply to rats and humans (pan-tissue rat clock; human-rat clocks for relative and chronologic age). Slowing of epigenetic age relative to chronologic age was assessed by multivariable regression adjusted for chronologic age, generation, sex and phenotype (treadmill running distance at 3 months of age). Epigenome wide association with phenotype was performed in Limma, with Benjamini-Hochberg p-value correction and significance set at FDR q<0.05. Gene set enrichment analysis was performed with Gene Ontology Biological Processes. Maximum treadmill running distance was ~8 times greater in HCR than LCR (2,137±500 vs. 246±63 m; p=1.97✕10-20). Across all samples and clocks, epigenetic age was associated with chronological age (r=0.461-0.500; p<3.60✕10-14). Compared with LCR, HCR epigenetic aging was slowed by a mean of -0.18 to -0.24 yrs, which represents 9-42% lower DNAmAge in HCR rats than LCR (p<0.024). Tissue-specific analyses revealed a lower DNAmAge in HCR for adipose, skeletal muscle and cardiac muscle (pan-tissue rat clock; p<0.04), and liver (human-rat clock for relative and chronologic age; p<0.01); effects were strongest at younger chronologic age. Significantly differentially methylated CpGs were found in skeletal muscle (n=11,341), cardiac muscle (n=2,480), adipose (n=3,036) and liver (n=12,595). Of the top 10 differentially methylated pathways, ~58% related to tissue development and ~20% related to cardiac or skeletal muscle. These data show differences in the rate of epigenetic aging manifest in tissues that directly (skeletal and cardiac muscle) and indirectly (adipose, liver) contribute to the energy transfer of aerobic exercise capacity upon which the selective breeding of LCR and HCR rat models were based. These data suggest that a large fraction of the survival benefit associated with high intrinsic exercise capacity is reflected in slowed epigenetic aging across multiple tissues. The Lundquist Institute. Epigenetic Clock Development Foundation. The University of Toledo Department of Physiology & Pharmacology. NIH (R01HL151452, R01HL153460, P50HD098593, P40OD021331). Open Philanthropy (SH). This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

INTERMITTENT KETOGENIC DIETS EXTEND LIFESPAN AND ATTENUATE INFLAMMAGING IN MALE MICE

Abstract A ketogenic diet (KD) has been shown to increase functional lifespan in male mice when fed isocalorically to a control diet (CD). However, it is not clear if intermittent ketogenic diets (IKD) that induce brief and recurring periods of ketosis would be as effective at prolonging lifespan. In the present study, 12-month-old C57BL/6JN male mice were fed an intermittent single day KD (KD fed on Mon, Wed and Fri each week, IK1) or 2-day KD (KD fed on 2 consecutive days each week, IK2). These two IKD regimes were selected to mimic the widely used alternate-day or 5:2 intermittent fasting approaches, without the caloric deficit. Our results showed that lifespan was significantly increased in both IK1 and IK2 groups, with IK1 showing a 13.6% and IK2 showing a 7.9% increase in median lifespan compared to the CD (p < 0.01). At 27 months of age, levels of circulating proinflammatory cytokines were significantly decreased in IK1 and IK2 mice compared to control mice. Also, levels of proinflammatory cytokines were significantly elevated in 27-month-old control mice compared to 12-month-old mice, while levels in IK1 and IK2 mice were not significantly altered with aging, and these effects were still persistent during days the animals were fed the CD. Unlike the continuous KD, health span measures were not altered in IK1 or IK2 mice at 26 months of age. In summary, IKDs that produce shorts episodes of ketosis can be effective at extending longevity in mice, possibly by attenuating systemic inflammation with aging.

The use of non-model Drosophila species to study natural variation in TOR pathway signaling.

Nutrition and growth are strongly linked, but not much is known about how nutrition leads to growth. To understand the connection between nutrition through the diet, growth, and proliferation, we need to study the phenotypes resulting from the activation and inhibition of central metabolic pathways. One of the most highly conserved metabolic pathways across eukaryotes is the Target of Rapamycin (TOR) pathway, whose primary role is to detect the availability of nutrients and to either induce or halt cellular growth. Here we used the model organism Drosophila melanogaster (D. mel.) and three non-model Drosophila species with different dietary needs, Drosophila guttifera (D. gut.), Drosophila deflecta (D. def.), and Drosophila tripunctata (D. tri.), to study the effects of dietary amino acid availability on fecundity and longevity. In addition, we inhibited the Target of Rapamycin (TOR) pathway, using rapamycin, to test how the inhibition interplays with the nutritional stimuli in these four fruit fly species. We hypothesized that the inhibition of the TOR pathway would reverse the phenotypes observed under conditions of overfeeding. Our results show that female fecundity increased with higher yeast availability in all four species but decreased in response to TOR inhibition. The longevity data were more varied: most species experienced an increase in median lifespan in both genders with an increase in yeast availability, while the lifespan of D. mel. females decreased. When exposed to the TOR inhibitor rapamycin, the life spans of most species decreased, except for D. tri, while we observed a major reduction in fecundity across all species. The obtained data can benefit future studies on the evolution of metabolism by showing the potential of using non-model species to track changes in metabolism. Particularly, our data show the possibility to use relatively closely related Drosophila species to gain insight on the evolution of TOR signaling.

Oroxylum indicum stem bark extract exerts antitumor potential against Ehrlich’s ascites carcinoma in Swiss albino mice

Introduction and Aim: Constant efforts are exerted to explore unique bioactive principles from natural sources that possess more effective and specific antineoplastic activities. In the present study, we aimed to evaluate the antitumor activity of stem bark extract of Oroxylum indicum in mice bearing Ehrlich ascites carcinoma (EAC). Materials and Methods: Ninety female Swiss albino mice were categorized into fifteen groups (n=6). The animals were inoculated with 1x106 EAC cells. Tumor control animals received sterile water once daily for 10 consecutive days. Positive control group was injected with Cisplatin (CP) (one dose – 3.5 mg/kg body weight). The treatment groups were administered with O. indicum (OI) stem bark ethanol extract once daily with 50mg/kg, 200mg/kg and 400mg/kg body weight for eleven consecutive days. The blood parameters and serum hepatic enzymes activity was determined. The percentage increase in weight, the median survival time, the increase in median life span was calculated. The cytotoxic effect of CP and OI extract was determined. Results: There was significant reduction in the white blood cells count in OI and CP treatment group compared to increased level in EAC control group. The RBC count and Hemoglobin level which was significantly decreased (p<0.05) in the tumour mice, was enhanced in the drug treatment groups. The EAC control group showed significant increase in tumour cell count (p<0.05) whereas, treatment of EAC tumor bearing mice with OI and CP significantly increased the non-viable tumor cell count (p<0.05). Conclusion: OI stem bark ethanol extract reduced the toxic implications of Ehrlich ascites carcinoma, reverted the haematological and biochemical changes induced by tumour. These results call for additional research on isolating and identifying the responsible bioactive elements in order to clarify the underlying processes of the anticancer impact.

Canagliflozin retards age-related lesions in heart, kidney, liver, and adrenal gland in genetically heterogenous male mice

Canagliflozin (Cana), a clinically important anti-diabetes drug, leads to a 14% increase in median lifespan and a 9% increase in the 90th percentile age when given to genetically heterogeneous male mice from 7 months of age, but does not increase lifespan in female mice. A histopathological study was conducted on 22-month-old mice to see if Cana retarded diverse forms of age-dependent pathology. This agent was found to diminish incidence or severity, in male mice only, of cardiomyopathy, glomerulonephropathy, arteriosclerosis, hepatic microvesicular cytoplasmic vacuolation (lipidosis), and adrenal cortical neoplasms. Protection against atrophy of the exocrine pancreas was seen in both males and females. Thus, the extension of lifespan in Cana-treated male mice, which is likely to reflect host- or tumor-mediated delay in lethal neoplasms, is accompanied by parallel retardation of lesions, in multiple tissues, that seldom if ever lead to death in these mice. Canagliflozin thus can be considered a drug that acts to slow the aging process and should be evaluated for potential protective effects against many other late-life conditions.

Mobilization-based transplantation of young-donor hematopoietic stem cells extends lifespan in mice.

Mammalian aging is associated with reduced tissue regeneration and loss of physiological integrity. With age, stem cells diminish in their ability to regenerate adult tissues, likely contributing to age‐related morbidity. Thus, we replaced aged hematopoietic stem cells (HSCs) with young‐donor HSCs using a novel mobilization‐enabled hematopoietic stem cell transplantation (HSCT) technology as an alternative to the highly toxic conditioning regimens used in conventional HSCT. Using this approach, we are the first to report an increase in median lifespan (12%) and a decrease in overall mortality hazard (HR: 0.42, CI: 0.273–0.638) in aged mice following transplantation of young‐donor HSCs. The increase in longevity was accompanied by reductions of frailty measures and increases in food intake and body weight of aged recipients. Young‐donor HSCs not only preserved youthful function within the aged bone marrow stroma, but also at least partially ameliorated dysfunctional hematopoietic phenotypes of aged recipients. This compelling evidence that mammalian health and lifespan can be extended through stem cell therapy adds a new category to the very limited list of successful anti‐aging/life‐extending interventions. Our findings have implications for further development of stem cell therapies for increasing health and lifespan.

High-glucose diets have sex-specific effects on aging in C. elegans: toxic to hermaphrodites but beneficial to males.

Diet and sex are important determinants of lifespan. In humans, high sugar diets, obesity, and type 2 diabetes correlate with decreased lifespan, and females generally live longer than males. The nematode Caenorhabditis elegans is a classical model for aging studies, and has also proven useful for characterizing the response to high-glucose diets. However, studies on male animals are lacking. We found a surprising dichotomy: glucose regulates lifespan and aging in a sex-specific manner, with beneficial effects on males compared to toxic effects on hermaphrodites. High-glucose diet resulted in greater mobility with age for males, along with a modest increase in median lifespan. In contrast, high-glucose diets decrease both lifespan and mobility for hermaphrodites. Understanding sex-specific responses to high-glucose diets will be important for determining which evolutionarily conserved glucose-responsive pathways that regulate aging are "universal" and which are likely to be cell-type or sex-specific.

PAI-1-regulated extracellular proteolysis governs senescence and survival in Klotho mice.

Cellular senescence restricts the proliferative capacity of cells and is accompanied by the production of several proteins, collectively termed the "senescence-messaging secretome" (SMS). As senescent cells accumulate in tissue, local effects of the SMS have been hypothesized to disrupt tissue regenerative capacity. Klotho functions as an aging-suppressor gene, and Klotho-deficient (kl/kl) mice exhibit an accelerated aging-like phenotype that includes a truncated lifespan, arteriosclerosis, and emphysema. Because plasminogen activator inhibitor-1 (PAI-1), a serine protease inhibitor (SERPIN), is elevated in kl/kl mice and is a critical determinant of replicative senescence in vitro, we hypothesized that a reduction in extracellular proteolytic activity contributes to the accelerated aging-like phenotype of kl/kl mice. Here we show that PAI-1 deficiency retards the development of senescence and protects organ structure and function while prolonging the lifespan of kl/kl mice. These findings indicate that a SERPIN-regulated cell-nonautonomous proteolytic cascade is a critical determinant of senescence in vivo.

Abstract 2681: Combined Dynamic 18F-FDG PET Imaging and DCE MRI prediction of treatment response in an orthotopic model of glioblastoma multiforme.

Abstract BACKGROUND: Gliobastomas (GBM) are highly aggressive tumors. When patients are treated with the standard of care of combined radiation therapy and temozolomide (TMZ), median survival is less than 15 months. An earlier prediction of treatment response could allow alternative salvage therapies to be applied sooner if efficacy is not evident. Non-invasive medical imaging provides the opportunity to link imaging-based biomarkers to treatment response. It was hypothesized that a multimodality imaging protocol (heretofore lacking) could allow more accurate prediction of treatment response than conventional means. MATERIALS & METHODS: 1x106 U87MG-luc cells were intracranially injected into 6-8 week old female Nude mice using a stereotactic surgical apparatus. Animals were staged for treatment using a T2-weighted MRI sequence and treatment groups were populated with a tumor volume of 10-20mm3. Treatment was delivered for 5 days as follows 1) Control and 2) TMZ. DCE MRI images were acquired with a gadolinium (Gd) contrast agent and dynamic 18F-FDG PET imaging was acquired at baseline and days 7 and 14 post-treatment. Initial AUC (at 30, 60 and 90s) and Ktrans were determined by fitting the Gd time course data to a generalized 2 compartment kinetic model (Tofts-Kermode approach) and calculated on a voxel-by-voxel basis. PET data was analyzed with traditional kinetic modeling (Ki) using Patlak analysis from 12-70 min and for the SUVmean and SUVmax. Unified metrics that combined Ktrans, Ki and/or SUV were evaluated for predictive power, as compared to each parameter alone. RESULTS: Animals treated with TMZ had a significant increase in median lifespan of 87 days, as compared to controls (59 days; p=0.002). Comparisons of the influx constant, Ki, showed no significant differences between control and treated groups, regardless of whether mean or maximum values were used. Similarly, there were no significant differences between groups in the SUV mean and SUVmax. DCE MRI data is currently undergoing analysis. CONCLUSIONS: Control and TMZ-treated groups produced expected median lifespan results as compared to historical data. Static and dynamic analysis of 18F-FDG PET data did not demonstrate differences between treated and untreated groups. It is possible that the time interval to differentiate the two groups was too proximate to extrapolate response from the derived parameters or that 18F-FDG is not the optimal tracer for this type analysis. It is therefore proposed that future studies utilize later time points in evaluating 18F-FDG-derived biomarkers and/or evaluate the utility of alternate radiotracers (e.g. 18F-FLT). Additionally, it is expected that combining radiation therapy with TMZ will produce more measurable differences in these biomarkers at early time points. A hybrid metric that combines PET and DCE MRI outputs is under development as an enhanced predictor of response. Citation Format: Erin Trachet, John Chunta, Chris Bull, Jeni Baranski, Tracey Woolliscroft, Deanne Lister, Patrick McConville, Dick Leopold. Combined Dynamic 18F-FDG PET Imaging and DCE MRI prediction of treatment response in an orthotopic model of glioblastoma multiforme. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 2681. doi:10.1158/1538-7445.AM2013-2681

Telomerase gene therapy in adult and old mice delays aging and increases longevity without increasing cancer

A major goal in aging research is to improve health during aging. In the case of mice, genetic manipulations that shorten or lengthen telomeres result, respectively, in decreased or increased longevity. Based on this, we have tested the effects of a telomerase gene therapy in adult (1 year of age) and old (2 years of age) mice. Treatment of 1- and 2-year old mice with an adeno associated virus (AAV) of wide tropism expressing mouse TERT had remarkable beneficial effects on health and fitness, including insulin sensitivity, osteoporosis, neuromuscular coordination and several molecular biomarkers of aging. Importantly, telomerase-treated mice did not develop more cancer than their control littermates, suggesting that the known tumorigenic activity of telomerase is severely decreased when expressed in adult or old organisms using AAV vectors. Finally, telomerase-treated mice, both at 1-year and at 2-year of age, had an increase in median lifespan of 24 and 13%, respectively. These beneficial effects were not observed with a catalytically inactive TERT, demonstrating that they require telomerase activity. Together, these results constitute a proof-of-principle of a role of TERT in delaying physiological aging and extending longevity in normal mice through a telomerase-based treatment, and demonstrate the feasibility of anti-aging gene therapy.

Comment on "Brain IRS2 Signaling Coordinates Life Span and Nutrient Homeostasis"

Taguchi et al. (Reports, 20 July 2007, p. 369) reported that mice heterozygous for a null mutation in insulin receptor substrate-2 (Irs2) display a 17% increase in median life span. However, using the same mouse model, we find no evidence for life-span extension and suggest that the findings of Taguchi et al. were due to atypical life-span profiles in their study animals.

Extension of mouse lifespan by overexpression of catalase

The free radical theory of aging was originally proposed 50 years ago, and is arguably the most popular mechanism explaining the aging process. According to this theory, aging results from the progressive decline in organ function due to the damage generated by reactive oxygen species (ROS). These chemical species are a normal part of metabolism, and a group of enzymes exists to protect cells against their toxic effects. One of these species is hydrogen peroxide (H(2)O(2)), which can be degraded by catalase. To determine the role of hydrogen peroxide in aging and its importance in different subcellular compartments, transgenic mice were developed with increased catalase activities localized to the peroxisome (PCAT), nucleus (NCAT), or mitochondrion (MCAT). The largest effect on lifespan was found in MCAT animals, with a 20% increase in median lifespan and a 10% increase in the maximum lifespan. A more modest effect was seen in PCAT animals, and no significant change was found in NCAT animals. Upon further examination of the MCAT mice, it was found that H(2)O(2) production and H(2)O(2)-induced aconitase inactivation were attenuated, oxidative damage and the development of mitochondrial deletions were reduced, and cardiac pathology and cataract development were delayed. These results are consistent with a role of H(2)O(2) in the development of pathology and in the limitation of mouse lifespan. They also demonstrate the importance of mitochondria as a source, and possible target, of ROS.

Preclinical studies on NSC290205 aza‐steroid alkylator activity in combination with adriamycin against lymphoid leukaemia

Summary NSC290205 (A) is an hybrid synthetic antineoplastic ester that is a combination of a d-lactam derivative of androsterone and an alkylating derivative of N,N-bis(2-chloroethyl)aniline. We tested NSC290205 for synergistic antileukaemic activity with adriamycin (ADR), (i) in vitro against the human lymphoid leukaemia cell lines: CCRF-CEM, MOLT-4, and RPMI-8226, (ii) in vivo against P388 lymphocytic and L1210 lymphoid murine leukaemias (at incipient and advanced phase). Our results indicated significant cytostatic and cytotoxic synergy of NSC290205 and ADR in vitro. We further examined these results in vivo by replacing cyclophosphamide in the standard CHOP (cyclophosphamide, hydroxydaunomycin, Oncovin, prednisone) regimen with NSC290205 (AHOP) and comparing the efficiency of these two regimens in vivo. Although treatment of P388 and L1210 with cyclophosphamide or NSC290205 alone yielded equivalent results, AHOP produced a clear benefit for survival compared with CHOP against advanced leukaemias, confirming the in vitro observations [higher percentage increase in median lifespan of treated animals over the untreated (control): 188% and 239% in L1210, 308% and 353% in P388, P < 0.01, for CHOP and AHOP respectively]. AHOP also proved to be more genotoxic and cytostatic than CHOP, inducing higher sister chromatid exchange levels and cell division delays on P388 cells in vivo. NSC290205 showed superior antineoplastic potential against lymphoid leukaemia and significant synergy with ADR, producing an excellent therapeutic outcome.

Dietary antioxidants modulation of aging and immune-endothelial cell interaction

Oxidative damage by free radicals, which is the basis for the free radical theory of aging, has been well investigated within the context of oxidant/antioxidant balance. Age-associated disorders are believed to be associated with the time-dependent shift in the antioxidant/prooxidant balance in favor of oxidative stress. In this brief review, the importance of dietary antioxidant intervention on longevity and age-associated changes in bodily functions and diseases are discussed. Evidence has indicated that increasing the endogenous antioxidants defense system and modulation of free radical production by dietary restrictions contribute to increased longevity in animal models. Thus, increasing dietary intake of antioxidants is believed to increase longevity. Earlier studies have shown some increase in median life span in animal models. It was found that supplementing middle-aged (18 months) C57/BL mice with various antioxidants (vitamin E, glutathione, melatonin, and strawberry extract) had no effect on longevity as measured by the average age of death. Therefore, dietary antioxidant supplementation seems unlikely to increase longevity when begun in middle age; supplementation started in early life might be more effective. However, in middle-aged mice, vitamin E was effective in reducing lung viral titer when animals were exposed to influenza virus. Vitamin E supplementation improves cell-mediated immunity in mice and in humans. In addition to modulating the oxidation of low-density lipoproteins, vitamin E can modulate immune/endothelial cells interactions, thus reducing the risk of cardiovascular disease (CVD), a major cause of morbidity and mortality in elderly. Thus, antioxidants such as vitamin E from food sources or supplements appear to be promising for successful aging by improving immune function, and reducing the risk of several age-associated chronic diseases, such as CVD.

Effects of dietary restriction and exercise on the age-related pathology of the rat

Intervention of the aging process is an effective, experimental means of uncovering the bases of aging. The most efficacious and commonly used intervention used to retard the aging processes is dietary restriction (DR). It increases mean and maximum life spans, delays the appearance, frequency, and severity of many age-related diseases, and more importantly, attenuates much of the physiological decline associated with age. Although the subject of intense research, the mechanism by which DR alters the aging processes is still unknown. Physical exercise is another effective intervention shown to affect aging phenomena, especially when applied in combination with DR. Mild exercise in concert with DR is beneficial, but vigorous exercise coupled with DR could be deleterious. With regard to pathology, exercise generally exerts a salutary influence on age-related diseases, both neoplastic and non-neoplastic, and this effect may contribute to the increase in median life span seen with exercised rats. Exercise coupled with 40% DR was found to suppress the incidence of fatal neoplastic disease compared to the sedentary DR group. Exercise with mild DR suppressed the incidence of multiple fatal disease and chronic nephropathy, and also delayed the occurrence of many age-related lesions compared to the ad libitum (AL) control group. However, these effects may have little bearing on the aging process per se, as maximum life span is only minimally affected. Although not as intensively studied as DR, results from studies that utilize exercise as a research probe, either alone or in combination with DR, have helped to assess the validity of proposed mechanisms for DR and aging itself. Neither the retardation of growth rate nor the increase in physical activity, observed with either exercise or DR, appear to contribute to the anti-aging action of DR. Moreover, results from lifelong exercise studies indicate that the effects of DR do not depend upon changes in energy availability or metabolic rate. The mechanisms involving effects on adiposity or immune function are also inadequate explanations for the action of DR on aging. Of the proposed mechanisms, only one, as postulated by the Oxidative Stress Hypothesis of Aging, tenably accounts for the known effects of DR and exercise on aging.

In vivo inhibition of etoposide-mediated apoptosis, toxicity, and antitumor effect by the topoisomerase II-uncoupling anthracycline aclarubicin.

A number of clinically important drugs such as the epipodophyllotoxins etoposide (VP-16) and teniposide (VM-26), the anthracycline daunorubicin and doxorubicin (Adriamycin), and the aminoacridine amsacrine exert their cytotoxic action by stabilizing the cleavable complex formed between DNA and the nuclear enzyme topoisomerase II. We have previously demonstrated in several in vitro assays that the anthracycline aclarubicin (aclacinomycin A) inhibits cleavable-complex formation and thus antagonizes the action of drugs such as VP-16 and daunorubicin. The present study was performed to validate these in vitro data in an in vivo model. At nontoxic doses of 6 and 9 mg/kg, aclarubicin yielded a marked increase in the survival of non-tumor-bearing mice given high doses of VP-16 (80-90 mg/kg) in six separate experiments. In therapy experiments on mice inoculated with Ehrlich ascites tumor cells, aclarubicin given at 6 mg/kg roughly halved the increase in median life span induced by VP-16 at doses ranging from 22 to 33 mg/kg. An attempt to determine a more favorable combination of VP-16 and aclarubicin by increasing VP-16 doses failed, as the two drugs were always less effective than VP-16 alone. The way in which VP-16-induced DNA strand breaks lead to cell death remains unknown. However, VP-16 has been reported to cause apoptosis (programmed cell death) in several cell lines. To ascertain whether the protection given by aclarubicin could have a disruptive effect on the apoptotic process, we used the small intestine as an in vivo model. Whereas VP-16-induced apoptosis in crypt stem cells was detectable at a dose as low as 1.25 mg/kg, aclarubicin given at up to 20 mg/kg did not cause apoptosis. Indeed, aclarubicin caused a statistically significant reduction in the number of cells rendered apoptotic by VP-16. The present study thus confirms the previous in vitro experiments and indicates the value of including an in vivo model in a preclinical evaluation of drug combinations.

Combined oral administration of etoposide and arabinofuranosylcytosine-5?-stearylphosphate enhances the antitumor effect against P388 ascites tumors

We investigated the antitumor effect of oral administration of etoposide and arabinofuranosylcytosine-5'-stearylphosphate (C18PCA) against P388 ascites tumors in B6D2F1 mice. Etoposide (25 mg/kg) and C18PCA (5 mg/kg) were given orally on days 1-5 after tumor inoculation. The median life span of the mice treated with etoposide or C18PCA alone was 19.5 and 18 days, respectively. The combination of both drugs significantly extended the median life span to 33 days. To clarify this enhancement of the increase in median life span, we examined intracellular deoxyribonucleoside triphosphate (dNTP) pools, cell-cycle distribution, DNA fragmentation, and the time course of the plasma drug concentration. Etoposide had no effect on intracellular dNTP pools in this experimental system, whereas treatment of cells with C18PCA or with the combination of both drugs resulted in a significant increase in dTTP pools to values ranging from 1.8- to 2.0-fold higher than the control levels. There was a significant increase in cells in the S + G2/M phase when cells had been treated with both etoposide and C18PCA. Agarose-gel electrophoresis of the extracted DNA revealed that C18PCA enhanced the fragmentation of DNA, with a length of about 180 bp being induced by etoposide. The plasma peak levels of etoposide (1000 nM) and ara-C (50 nM) were observed at 20 and 30 min after the simultaneous administration of both drugs, respectively. The plasma etoposide level gradually decreased to 10% of the peak level at 240 min after administration. On the other hand, the plasma concentration of ara-C was maintained at above 20 nM at 240 min. These observations suggest that C18PCA and etoposide act on P388 murine leukemic cells by accumulating cells in the S + G2/M phase. Even if the plasma concentration of ara-C is low, the repair of DNA damage by etoposide may be hindered in the presence of ara-C following an increase in DNA fragmentation.

Antileukemic activity against L1210 leukemia, pharmacokinetics and hematological side effects of 5-hydroxymethyl-2′-deoxyuridine

The chemotherapeutic potential of 5-hydroxymethyl-2′-deoxyuridine (5HmdUrd) was examined in vitro and in vivo. The compound was toxic in 2-day cultures; 7, 66 and 88% inhibition in the growth of L1210 cells was achieved with 1, 10 and 100 μM 5HmdUrd, respectively. The maximal plasma concentration of 5HmdUrd at 15 min after a single i.p. injection (100 mg/kg) in DBA/2 mice was 193–244 μmol./l and the compound had a logarithmic disappearance curve with a half-life of 20 min. Chemotherapy given as two daily i.p. injections of 5HmdUrd (100 mg/kg) for five successive days resulted in a 239% increase in median lifespan and 2/6 long-term survivals among DBA/2 mice bearing leukemia L1210. This treatment resulted in temporary neutropenia and thrombocytopenia, which were followed by rebound thrombocytosis and neutrophilia of short duration. Our data indicate that 5HmdUrd can successfully be used in experimental cancer chemotherapy in vivo.

Methotrexate analogues. 18. Enhancement of the antitumor effect of methotrexate and 3',5'-dichloromethotrexate by the use of lipid-soluble diesters.

Lipophilic methotrexate (MTX) and 3',5'-dichloromethotrexate (DCM) diesters were prepared by HCl-catalyzed esterification or by neutral esterification using cesium carbonate and an alkyl or aralkyl halide in Me2SO. The products were tested for in vivo antitumor activity against L1210 leukemia in mice to test whether all MTX and DCM diesters are therapeutically equivalent in this species. Contrary to what has been found with simple primary dialkyl esters, ortho-substituted dibenzyl esters of MTX produce longer survival on a q3dX3 schedule than does MTX itself and show a dose-sparing effect comparable to that of MTX at shorter treatment intervals. Thus, MTX bis(6-chloropiperonyl) ester at an MTX-equivalent dose of 5.5 mg/kg gave a +88% increase in median life span (ILS), whereas for MTX a +88% ILS required 30 mg/kg. When the MTX-equivalent dose of MTX bis(6-chloropiperonyl) ester was increased to 40 mg/kg, a +167% ILS was observed, as compared with a +100% ILS with 60 mg/kg of the parent drug. High activity (greater than 100% ILS) was likewise shown by the bis(2,5-dimethylbenzyl), bis(2,6-dichlorobenzyl), and di-3-picolyl esters of MTX and by the bis(1-methylbutyl) ester of DCM. The results of this study indicate that MTX and DCM esters are not therapeutically equivalent in mice, despite the high serum esterase activity in this species, and that an up to 10-fold reduction in total administered dose on the q3dX3 schedule is feasible by this approach.