Dietary energy restriction does not inhibit pancreatic carcinogenesis by N-nitrosobis-2-(oxopropyl)amine in the Syrian hamster

Healthful aging mediated by inhibition of oxidative stress

The progressive increase in lifespan over the past century carries with it some adversity related to the accompanying burden of debilitating diseases prevalent in the older population. This review focuses on oxidative stress as a major mechanism limiting longevity in general, and healthful aging, in particular. Accordingly, the first goal of this review is to discuss the role of oxidative stress in limiting longevity, and compare healthful aging and its mechanisms in different longevity models. Secondly, we discuss common signaling pathways involved in protection against oxidative stress in aging and in the associated diseases of aging, e.g., neurological, cardiovascular and metabolic diseases, and cancer. Much of the literature has focused on murine models of longevity, which will be discussed first, followed by a comparison with human models of longevity and their relationship to oxidative stress protection. Finally, we discuss the extent to which the different longevity models exhibit the healthful aging features through physiological protective mechanisms related to exercise tolerance and increased β-adrenergic signaling and also protection against diabetes and other metabolic diseases, obesity, cancer, neurological diseases, aging-induced cardiomyopathy, cardiac stress and osteoporosis.

The Role of Diet in Cancer Prevention and Chemotherapy Efficacy

Despite great advances in treatment, cancer remains a leading cause of death worldwide. Diet can greatly impact health, while caloric restriction and fasting have putative benefits for disease prevention and longevity. Strong epidemiological associations exist between obesity and cancer, whereas healthy diets can reduce cancer risk. However, less is known about how diet might impact cancer once it has been diagnosed and particularly how diet can impact cancer treatment. In the present review, we discuss the links between obesity, diet, and cancer. We explore potential mechanisms by which diet can improve cancer outcomes, including through hormonal, metabolic, and immune/inflammatory effects, and present the limited clinical research that has been published in this arena. Though data are sparse, diet intervention may reduce toxicity, improve chemotherapy efficacy, and lower the risk of long-term complications in cancer patients. Thus, it is important that we understand and expand the science of this important but complex adjunctive cancer treatment strategy.

Roles of caloric restriction, ketogenic diet and intermittent fasting during initiation, progression and metastasis of cancer in animal models: a systematic review and meta-analysis

BACKGROUND

The role of dietary restriction regimens such as caloric restriction, ketogenic diet and intermittent fasting in development of cancers has been detected via abundant preclinical experiments. However, the conclusions are controversial. We aim to review the relevant animal studies systematically and provide assistance for further clinical studies.

METHODS

Literatures on associations between dietary restriction and cancer published in PubMed in recent twenty years were comprehensively searched. Animal model, tumor type, feeding regimen, study length, sample size, major outcome, conclusion, quality assessment score and the interferential step of cancer were extracted from each eligible study. We analyzed the tumor incidence rates from 21 studies about caloric restriction.

RESULTS

Fifty-nine studies were involved in our system review. The involved studies explored roles of dietary restriction during initiation, progression and metastasis of cancer. About 90.9% of the relevant studies showed that caloric restriction plays an anti-cancer role, with the pooled OR (95%CI) of 0.20 (0.12, 0.34) relative to controls. Ketogenic diet was also positively associated with cancer, which was indicated by eight of the nine studies. However, 37.5% of the related studies obtained a negative conclusion that intermittent fasting was not significantly preventive against cancer.

CONCLUSIONS

Caloric restriction and ketogenic diet are effective against cancer in animal experiments while the role of intermittent fasting is doubtful and still needs exploration. More clinical experiments are needed and more suitable patterns for humans should be investigated.

A novel combinatorial nanotechnology-based oral chemopreventive regimen demonstrates significant suppression of pancreatic cancer neoplastic lesions

Pancreatic cancer is a deadly disease killing 37,000 Americans each year. Despite two decades of research on treatment options, the chances of survival are still less than 5% upon diagnosis. Recently, chemopreventive strategies have gained considerable attention as an alternative to treatment. We have previously shown significant in vitro chemopreventive effects with low-dose combinations of aspirin, curcumin, and sulforaphane (ACS) on pancreatic cancer cell lines. Here, we report the results of 24-week chemopreventive study with the oral administration of ACS combinations on the N-nitrosobis (2-oxopropyl) amine (BOP)-treated Syrian golden hamster model to suppress the progression of pancreatic intraepithelial neoplasms (PanIN) using unmodified (free drug) combinations of ACS, and nanoencapsulated (solid lipid nanoparticles; SLN) combinations of aspirin, curcumin, and free sulforaphane. The use of three different doses (low, medium, and high) of unmodified ACS combinations exhibited reduction in tumor incidence by 18%, 50%, and 68.7% respectively; whereas the modified nanoencapsulated ACS regimens reduced tumor incidence by 33%, 67%, and 75%, respectively, at 10 times lower dose compared with the free drug combinations. Similarly, although the unmodified free ACS showed a notable reduction in cell proliferation, the SLN encapsulated ACS regimens showed significant reduction in cell proliferation at 6.3%, 58.6%, and 72.8% as evidenced by proliferating cell nuclear antigen expression. Cell apoptotic indices were also upregulated by 1.5, 2.8, and 3.2 times, respectively, compared with BOP control. These studies provide a proof-of-concept for the use of an oral, low-dose, nanotechnology-based combinatorial regimen for the long-term chemoprevention of pancreatic cancer.

Calorie restriction delays the progression of lesions to pancreatic cancer in the LSL-KrasG12D; Pdx-1/Cre mouse model of pancreatic cancer

Since pancreatic cancer is a lethal disease, developing prevention strategies is an important goal. We determined whether calorie restriction would prevent the development and delay progression of pancreatic intraepithelial neoplasms to pancreatic ductal adenocarcinoma (PDA) in LSL-KrasG12D/+; Pdx-1/Cre mice that develop all the precursor lesions that progress to PDA. Eight-week-old LSL-KrasG12D; Pdx-1/Cre mice were assigned to three groups: (1) ad libitum (AL) fed the AIN93M diet or (2) intermittently calorie restricted (ICR) a modified AIN93M at 50% of AL intake followed by one week intervals at 100% of AL intake, or (3) chronically calorie restricted (CCR) an AIN93M diet at 75% of AL intake. AL fed mice had a greater percentage of pancreatic ducts with PanIN-2 (13.6%) than did the ICR (1.0%) and CCR groups (1.6%), P < 0.0001. Calorie restriction (ICR [0%] and CCR [0.7%]) reduced the percentage of ducts with PanIN-3 lesions compared to the AL group (7.0%), P < 0.0001. The incidence of PanIN-2 or more lesions was significantly reduced in both ICR (27%; n = 16) and CCR (40%) mice (n = 15; P < 0.001) compared to AL (70%) fed mice (n = 11). The delayed progression of lesions in ICR and CCR mice was associated with reduced proliferation measured by proliferating cell nuclear antigen staining, reduced protein expression of Glut1, increased protein expression of Sirt1, increased serum adiponectin, and decreased serum leptin. CCR resulted in decreased phosphorylated mammalian target of rapamycin and decreased serum insulin-like growth factor-1. In summary, this is the first study to show in LSL-KrasG12D; Pdx-1/Cre mice that ICR and CCR delay the progression of lesions to PDA.

Genetic reduction of insulin-like growth factor-1 mimics the anticancer effects of calorie restriction on cyclooxygenase-2-driven pancreatic neoplasia

Risk of pancreatic cancer, the fourth deadliest cancer in the United States, is increased by obesity. Calorie restriction (CR) prevents obesity, suppresses carcinogenesis in many models, and reduces serum levels of IGF-1. In the present study, we examined the impact of CR on a model of inflammation-associated pancreatitis and pancreatic dysplasia, with a focus on the mechanistic contribution of systemic IGF-1. Administration of a 30% CR diet for 14 weeks decreased serum IGF-1 levels and hindered pancreatic ductal lesion formation and dysplastic severity, relative to a higher calorie control diet, in transgenic mice overexpressing COX-2 [bovine keratin-5 promoter (BK5.COX-2)]. These findings in CR mice correlated with reductions in Ki-67-positive cells, vascular luminal size, VEGF expression, and phosphorylation and total expression of downstream mediators of the IGF-1 pathway. Cell lines derived from BK5.COX-2 ductal lesions (JC101 cells) formed pancreatic tumors in wild-type FVB mice that were significantly reduced in size by a 14-week CR regimen, relative to the control diet. To further understand the impact of circulating levels of IGF-1 on tumor growth in this model, we orthotopically injected JC101 cells into liver-specific IGF-1-deficient (LID) mice. The approximate 65% reduction of serum IGF-1 levels in LID mice resulted in significantly decreased burden of JC101 tumors, despite modestly elevated levels of circulating insulin and leptin. These data show that CR prevents development of dysplasia and growth of pancreatic cancer through alterations in IGF-1, suggesting that modulation of this pathway with dietary and/or pharmacologic interventions is a promising pancreatic cancer prevention strategy.

Null effect of dietary restriction on prostate carcinogenesis in the Wistar-Unilever rat

Chronic dietary restriction inhibits carcinogenesis in several sites in laboratory animals. To determine the effects of dietary restriction on prostate carcinogenesis, prostate cancers were induced in male Wistar-Unilever rats by a sequential regimen of cyproterone acetate (50 mg/day; 21 days); testosterone propionate (100 mg/kg/day; 3 days); N-methyl-N-nitrosourea [MNU; 30 mg/kg; single dose]; and testosterone (subcutaneous implants of 2 pellets containing 40 mg each). Dietary restriction (0% [ad libitum control], 15%, or 30%) was initiated 2 wk post-MNU, and continued until study termination at 12 mo. Dietary restriction induced a rapid suppression of body weight gain but conferred no protection against prostate carcinogenesis. 74% of carcinogen-treated ad libitum controls developed accessory sex gland cancers, versus cancer incidences of 64% and 72% in groups restricted by 15% and 30%, respectively. Similarly, 44% of dietary controls developed cancers limited to the dorsolateral/prostate, versus incidences of 45% and 53% in groups restricted by 15% and 30%. The results of the present study do not support the hypothesis that prostate carcinogenesis can be prevented by reducing caloric intake. Reducing mean body weight by up to 25% through chronic dietary restriction has no effect on the induction of prostate cancers in the Wistar-Unilever rat model.

Nitric Oxide–Donating Aspirin Prevents Pancreatic Cancer in a Hamster Tumor Model

To evaluate the chemopreventive effect of nitric oxide-donating aspirin (NO-ASA), an ASA bearing a NO-releasing moiety, against pancreatic cancer, we studied six groups of female Syrian golden hamsters: groups 1 to 3 (n = 12 each) were given saline and groups 4 to 6 (n = 17) the carcinogen N-nitrosobis(2-oxopropyl)amine (BOP) s.c. in five weekly injections (the first, 70 mg/kg, and the remaining, 20 mg/kg each). Control and BOP-treated hamsters were fed a NO-ASA 3,000 ppm or conventional ASA 3,000 ppm or control diet for 19 weeks. Groups 1 to 3 had no tumors. Compared with the BOP/vehicle group, NO-ASA reduced the incidence (88.9%, P < 0.003) and multiplicity (94%, P < 0.05) of pancreatic cancer; ASA had no statistically significant effect. NO-ASA arrested the transition from PanIN2 to PanIN3 and carcinoma. The proliferation (proliferating cell nuclear antigen) / apoptosis (terminal deoxyribonucleotide transferase-mediated nick-end labeling) ratio of ductal cells increased with the histologic severity of the ductal lesion; NO-ASA suppressed it significantly during all stages except PanIN1A. p21(WAF1/CIP1), undetectable in normal cells, was progressively induced in neoplastic cells and suppressed by NO-ASA up to PanIN3. Nuclear factor-kappaB activation, absent in normal tissue, increased progressively (17-fold in cancer); NO-ASA suppressed it throughout and significantly in PanIN1B and PanIN2. Cyclooxygenase-2 expression, absent during early stages, was induced 6-fold in carcinoma and suppressed by NO-ASA in PanIN3 and carcinoma. Conventional ASA had no effect on these molecular markers. Thus, NO-ASA profoundly prevented pancreatic cancer and modulated multiple molecular targets in this model system; conventional ASA had no such effects. NO-ASA merits further evaluation as a chemopreventive agent against pancreatic cancer.

Prevention of pancreatic cancer induction in hamsters by metformin

BACKGROUND AND AIMS

Our previous study suggested that the known promotional effect of a high fat diet, which in hamsters induces peripheral insulin resistance, is related to a compensatory proliferation of islet cells. The present study was to examine whether the prevention of islet cell proliferation can inhibit the promotional effect of a high-fat diet in pancreatic carcinogenesis.

METHODS

Two groups of high fat-fed hamsters were used. One group received Metformin in drinking water for life (HF+Met group), and the other group served as a control (HF group). At the time when the normalization of the plasma insulin level was expected, all hamsters were treated with the pancreatic carcinogen, N-nitrosobis-(2-oxopropyl)amine, and the experiment was terminated 42 weeks later.

RESULTS

Although 50% of the hamsters in the high-fat group developed malignant lesions, none was found in the HF+Met group (P < 0.05). Also, significantly more hyperplastic and premalignant lesions, most of which were found within the islets, were detected in the high-fat group (8.6 lesions/hamster) than in the HF+Met group (1.8 lesions/hamster).

CONCLUSIONS

The results lend further support on the significant role of islet cells in pancreatic carcinogenesis and may explain the association between pancreatic cancer and obesity, which is usually associated with peripheral insulin resistance.

Risk factors for pancreatic cancer: a case-control study based on direct interviews

The etiology of pancreatic cancer is poorly understood, partly because of the inconsistency of findings among case-control studies of pancreatic cancer. Because of the unfavorable prognosis for pancreatic cancer, many case-control studies have been based largely on interviews with next of kin, who are known to report less reliable information on potential risk factors than original respondents. The purpose of this study was to estimate the effects of speculative risk factors such as dietary/nutritional factors and alcohol drinking, as well as those of established risk factors such as cigarette smoking, diabetes mellitus, and family history of pancreatic cancer, on pancreatic cancer risk based solely on direct interviews. This investigation was a population-based case-control study of pancreatic cancer diagnosed in Atlanta (GA), Detroit (MI), and ten New Jersey counties from August 1986 through April 1989. Direct interviews were conducted with 526 incident cases and 2,153 population controls. This study revealed a significant interaction between body mass index and caloric intake that was consistent by both race and gender. Subjects with elevated body mass index and caloric intake had increased risk, whereas those with elevated values for one of these factors but not the other experienced no increased risk. This finding suggests that energy balance may play a major role in pancreatic carcinogenesis. Diabetes mellitus was also a risk factor for pancreatic cancer, as well as a possible complication of the tumor. Our data are consistent with a key role for hyperinsulinemia in pancreatic carcinogenesis, particularly among non-diabetics with an elevated body mass index. A three-fold risk of pancreatic cancer among first-degree relatives of affected individuals was apparent. An increased risk also was associated with a family history of colon, endometrial, ovary, and breast cancer, suggesting a possible link to hereditary non-polyposis colon cancer. Our findings support a causal role for cigarette smoking in pancreatic carcinogenesis. Alcohol drinking at levels typically consumed by the general population of the United States did not appear to be a risk factor for pancreatic cancer, although heavy drinking may be related to risk, particularly in blacks.

Dietary and nutritional factors and pancreatic cancer: a case-control study based on direct interviews

BACKGROUND

The relationship between diet and pancreatic cancer remains unclear. In this study, we assessed the role of diet and nutrition as risk factors for pancreatic cancer, using data obtained from direct interviews only, rather than data from less reliable interviews with next of kin. We evaluated whether dietary factors could explain the higher incidence of pancreatic cancer experienced by black Americans compared with white Americans.

METHODS

We conducted a population-based case-control study of pancreatic cancer diagnosed in Atlanta (GA), Detroit (MI), and 10 New Jersey counties from August 1986 through April 1989. Reliable dietary histories were obtained for 436 patients and 2003 general-population control subjects aged 30-79 years.

RESULTS

Obesity was associated with a statistically significant 50%-60% increased risk of pancreatic cancer that was consistent by sex and race. Although the magnitude of risk associated with obesity was identical in blacks and whites, a higher percentage of blacks were obese than were whites (women: 38% versus 16%; men: 27% versus 22%). A statistically significant positive trend in risk was observed with increasing caloric intake, with subjects in the highest quartile of caloric intake experiencing a 70% higher risk than those in the lowest quartile. A statistically significant interaction between body mass index (weight in kg/height in m2 for men and weight in kg/height in m1.5 for women) and total caloric intake was observed that was consistent by sex and race. Subjects in the highest quartile of both body mass index and caloric intake had a statistically significant 180% higher risk than those in the lowest quartile.

CONCLUSIONS

Obesity is a risk factor for pancreatic cancer and appears to contribute to the higher risk of this disease among blacks than among whites in the United States, particularly among women. Furthermore, the interaction between body mass index and caloric intake suggests the importance of energy balance in pancreatic carcinogenesis.