Primary prevention: phytoprevention and chemoprevention of colorectal cancer

Conjugation, Prodrug, and Co-Administration Strategies in Support of Nanotechnologies to Improve the Therapeutic Efficacy of Phytochemicals in the Central Nervous System

Phytochemicals, produced as secondary plant metabolites, have shown interesting potential therapeutic activities against neurodegenerative diseases and cancer. Unfortunately, poor bioavailability and rapid metabolic processes compromise their therapeutic use, and several strategies are currently proposed for overcoming these issues. The present review summarises strategies for enhancing the central nervous system's phytochemical efficacy. Particular attention has been paid to the use of phytochemicals in combination with other drugs (co-administrations) or administration of phytochemicals as prodrugs or conjugates, particularly when these approaches are supported by nanotechnologies exploiting conjugation strategies with appropriate targeting molecules. These aspects are described for polyphenols and essential oil components, which can improve their loading as prodrugs in nanocarriers, or be part of nanocarriers designed for targeted co-delivery to achieve synergistic anti-glioma or anti-neurodegenerative effects. The use of in vitro models, able to simulate the blood-brain barrier, neurodegeneration or glioma, and useful for optimizing innovative formulations before their in vivo administration via intravenous, oral, or nasal routes, is also summarised. Among the described compounds, quercetin, curcumin, resveratrol, ferulic acid, geraniol, and cinnamaldehyde can be efficaciously formulated to attain brain-targeting characteristics, and may therefore be therapeutically useful against glioma or neurodegenerative diseases.

Molecular approaches to lung cancer prevention

Lung cancer is generally diagnosed at advanced stages when surgical resection is not possible. Late diagnosis, along with development of chemoresistance, results in high mortality. Preventive approaches, including smoking cessation, chemoprevention and early detection are needed to improve survival. Smoking cessation combined with low-dose computed tomography screening has modestly improved survival. Chemoprevention has also shown some promise. Despite these successes, most lung cancer cases remain undetected until advanced stages. Additional early detection strategies may further improve survival and treatment outcome. Molecular alterations taking place during lung carcinogenesis have the potential to be used in early detection via noninvasive methods and may also serve as biomarkers for success of chemopreventive approaches. This review focuses on the utilization of molecular biomarkers to increase the efficacy of various preventive approaches.

The inhibitory effect of Filipendula ulmaria (L.) Maxim. on colorectal carcinogenesis induced in rats by methylnitrosourea

ETHNOPHARMACOLOGICAL RELEVANCE

Meadowsweet (Filipendula ulmaria (L.) Maxim.) is a medicinal plant with a variety of therapeutic properties, traditionally used in various diseases including treatment and prevention of tumors. The aim of this study was to present an ethnomedicinal justification that a meadowsweet decoction is able to inhibit colorectal carcinogenesis induced by the methylnitrosourea (MNU) in rats.

MATERIALS AND METHODS

The chemical composition of meadowsweet extracts was studied by traditional methods. In animal experiments adult outbred female rats received four intrarectal instillations of MNU, one per week, at dose 4 mg in 0.5 ml saline (the total dose of MNU during the 4-week exposure was 16 mg/rat). After carcinogenic exposure one group (MNU) of rats continued to receive standard feed and tap water throughout life. In another group (MNU+meadowsweet), rats were given daily a decoction of the meadowsweet instead of drinking water and standard feed.

RESULTS

Meadowsweet extracts showed a sufficiently high content of flavonoids and tannins and also some individual phenolic compounds and salicylic acid. In rats after administration of MNU the overall incidence of tumors was 91% with tumor multiplicity of 3.5. The majority of rats (86%) developed multiple tumors of large intestine (most often adenocarcinomas:88 from 107; index of multiplicity - 2.0). In rats from the group MNU+meadowsweet there was a statistically significant decrease of the overall tumor incidence and multiplicity-by 1.4 and 2.9 times, respectively, and the incidence and multiplicity of colon tumors - by 2.0 and 2.8 times, respectively; the incidence and multiplicity of malignant tumors of other localizations was also reduced-by 2.2 and 3.0 times, respectively.

CONCLUSIONS

Meadowsweet extract is an effective inhibitor of colorectal carcinogenesis in experiment, that provides support for the traditional use of this plant in the oncology.

Effects of Walnut Consumption on Colon Carcinogenesis and Microbial Community Structure

Walnuts are composed of a complex array of biologically active constituents with individual cancer-protective properties. Here, we assessed the potential benefit of whole walnut consumption in a mouse tumor bioassay using azoxymethane. In study 1, a modest reduction (1.3-fold) in tumor numbers was observed in mice fed a standard diet (AIN-76A) containing 9.4% walnuts (15% of total fat). In study 2, the effects of walnut supplementation was tested in the Total Western Diet (TWD). There was a significant reduction (2.3-fold; P < 0.02) in tumor numbers in male mice fed TWD containing 7% walnuts (10.5% of total fat). Higher concentrations of walnuts lacked inhibitory effects, particularly in female mice, indicating there may be optimal levels of dietary walnut intake for cancer prevention. Since components of the Mediterranean diet have been shown to affect the gut microbiome, the effects of walnuts were therefore tested in fecal samples using 16S rRNA gene sequencing. Carcinogen treatment reduced the diversity and richness of the gut microbiome, especially in male mice, which exhibited lower variability and greater sensitivity to environmental changes. Analysis of individual operational taxonomic units (OTU) identified specific groups of bacteria associated with carcinogen exposure, walnut consumption, and/or both variables. Correlation analysis also identified specific OTU clades that were strongly associated with the presence and number of tumors. Taken together, our results indicate that walnuts afford partial protection to the colon against a potent carcinogenic insult, and this may be due, in part, to walnut-induced changes to the gut microbiome. Cancer Prev Res; 9(8); 692-703. ©2016 AACR.

Chemoprevention in gastrointestinal physiology and disease. Targeting the progression of cancer with natural products: a focus on gastrointestinal cancer

The last decade has witnessed remarkable progress in the utilization of natural products for the prevention and treatment of human cancer. Many agents now in the pipeline for clinical trial testing have evolved from our understanding of how human nutritional patterns account for widespread differences in cancer risk. In this review, we have focused on many of these promising agents arguing that they may provide a new strategy for cancer control: natural products once thought to be only preventive in their mode of action now are being explored for efficacy in tandem with cancer therapeutics. Natural products may reduce off-target toxicity of therapeutics while making cancers more amenable to therapy. On the horizon is the use of certain natural products, in their own right, as mitigants of late-stage cancer, a new frontier for small-molecule natural product drug discovery.

Nuclear factor-erythroid 2-related factor 2 as a chemopreventive target in colorectal cancer

INTRODUCTION

Numerous epidemiological studies have linked consumption of cruciferous vegetables to a reduced risk of colorectal cancer (CRC) in individuals. It is currently well accepted that chronic inflammation is a contributing factor in 15 - 20% malignancies including CRC. Many chemopreventive compounds are effective in preclinical systems and many ongoing clinical trials are showing promising findings. Many of these compounds could activate the antioxidant responsive element (ARE), a critical regulatory element for Phase II protective/detoxification and antioxidative stress enzymes mediated by nuclear factor-erythroid 2-related factor 2 (Nrf2). Recently, Nrf2 has emerged as a novel target for the prevention of CRC.

AREAS COVERED

A full literature search was performed using PubMed with the key words 'ARE, Nrf2, colon, colorectal cancer, chemoprevention, cancer prevention', and all relevant publications are included.

EXPERT OPINION

The use of Nrf2 knockout mice has provided key insights into the toxicological and chemopreventive importance of this pathway. Mounting evidence has revealed that Nrf2 is a critical regulator of inflammation as well, a major driving force for CRC progression and formation. Targeting the Nrf2/ARE pathway may present a novel therapeutic approach for the treatment of not only colorectal inflammatory diseases but the frequent subsequent development of CRC as well.

Meta-analysis: antioxidant supplements for primary and secondary prevention of colorectal adenoma

BACKGROUND

Colorectal cancer may be prevented by reducing the development of adenomatous polyps.

AIM

To assess the benefits and harms of antioxidant supplements in preventing colorectal adenoma.

METHODS

Using the Cochrane Collaboration methodology we reviewed all randomized clinical trials comparing antioxidant supplements with placebo or no intervention. We searched electronic databases and the reference lists until October 2005. Outcome measures were development of colorectal adenoma adverse events. We analysed dichotomous outcomes with fixed- and random-effects model meta-analyses and calculated the relative risk with 95% confidence interval.

RESULTS

We identified eight randomized trials (17 620 participants). Neither fixed-effect (relative risk: 0.93, 95% CI: 0.81-1.1) nor random-effect model meta-analyses (0.82, 0.60-1.1) showed statistically significant effects of supplementation with beta-carotene, vitamins A, C, E and selenium alone or in combination. Antioxidant supplements seemed to increase the development of colorectal adenoma in three low-bias risk trials (1.2, 0.99-1.4) and significantly decrease its development in five high-bias risk trials (0.59, 0.47-0.74). The estimates difference is significant (P < 0.0001). There was no significant difference between the intervention groups regarding adverse events, including mortality (0.82, 0.47-1.4).

CONCLUSION

We found no convincing evidence that antioxidant supplements have significant beneficial effect on primary or secondary prevention of colorectal adenoma.

From Colonic Polyps to Colon Cancer: Pathophysiology, Clinical Presentation, and Diagnosis

Epidemiologists, basic researchers, clinicians, and public health administrators unite! Develop and implement a simple, safe, and effective preventive and screening test for colon cancer. The public will willingly and enthusiastically accept such a test. Many thousands of lives are at stake every year.

The pathophysiology, clinical presentation, and diagnosis of colon cancer and adenomatous polyps

A review of the pathophysiology, clinical presentation, and diagnosis of colon cancer and colonic polyps is important and timely. This field is rapidly changing because of breakthroughs in the molecular basis of carcinogenesis and in the technology for colon cancer detection and treatment. This article reviews colon cancer and colonic polyps, with a focus on recent dramatic advances, to help the pri-mary care physician and internist appropriately refer patients for screening colonoscopy and intelligently evaluate colonoscopic findings to reduce the mortality from this cancer.

Growth inhibitory effects of celecoxib in human umbilical vein endothelial cells are mediated through G1 arrest via multiple signaling mechanisms

Evidence suggests that the angiogenic endothelium represents an important target through which celecoxib mediates in vivo antitumor effects. Nevertheless, the pharmacologic basis for celecoxib-caused growth inhibition in endothelial cells in vitro remains to be defined. Previously, we showed that celecoxib-induced apoptosis in PC-3 prostate cancer cells was mediated in part through the inhibition of 3-phosphoinositide-dependent kinase-1/Akt signaling. Our present findings show that celecoxib inhibits the growth of human umbilical vein endothelial cells (HUVEC) with pharmacologic profiles reminiscent of those of PC-3 cells. The underlying antiproliferative mechanism, however, may differ between these two cell types considering differences in the functional status of many tumor suppressors, including PTEN, p53, and retinoblastoma, all of which play integral roles in regulating cell cycle progression and survival. From a mechanistic perspective, the genomic integrity of the HUVEC system presents a vastly different intracellular context to examine how celecoxib acts to induce growth inhibition. Here, we obtain evidence that the antiproliferative effects of celecoxib and its close, cyclooxygenase-2-inactive analogue 4-[5-(2,5-dimethylphenyl)-3(trifluoromethyl)-1H-pyrazol-1-yl]benzenesulfonamide (DMC) in HUVECs at pharmacologically attainable concentrations (10–20 μmol/L) are attributable to the inhibition of phosphoinositide-dependent kinase-1/Akt signaling and cyclin-dependent kinase. Especially, celecoxib- and DMC-mediated G1 arrest is associated with attenuated retinoblastoma phosphorylation through the inhibition of multiple cyclin-dependent kinases (IC50, 10–35 μmol/L). Moreover, both celecoxib and DMC reduce neovascularization in the chicken chorioallantoic membrane assay, suggesting the involvement of a cyclooxygenase-2-independent mechanism in the in vivo antiangiogenic effects of celecoxib.