Assessment of the role of diet in cancer prevention

Halophilic Carotenoids and Breast Cancer: From Salt Marshes to Biomedicine

Breast cancer is the leading cause of death among women worldwide. Over the years, oxidative stress has been linked to the onset and progression of cancer. In addition to the classical histological classification, breast carcinomas are classified into phenotypes according to hormone receptors (estrogen receptor-RE-/progesterone receptor-PR) and growth factor receptor (human epidermal growth factor receptor-HER2) expression. Luminal tumors (ER/PR-positive/HER2-negative) are present in older patients with a better outcome. However, patients with HER2-positive or triple-negative breast cancer (TNBC) (ER/PR/HER2-negative) subtypes still represent highly aggressive behavior, metastasis, poor prognosis, and drug resistance. Therefore, new alternative therapies have become an urgent clinical need. In recent years, anticancer agents based on natural products have been receiving huge interest. In particular, carotenoids are natural compounds present in fruits and vegetables, but algae, bacteria, and archaea also produce them. The antioxidant properties of carotenoids have been studied during the last years due to their potential in preventing and treating multiple diseases, including cancer. Although the effect of carotenoids on breast cancer during in vitro and in vivo studies is promising, clinical trials are still inconclusive. The haloarchaeal carotenoid bacterioruberin holds great promise to the future of biomedicine due to its particular structure, and antioxidant activity. However, much work remains to be performed to draw firm conclusions. This review summarizes the current knowledge on pre-clinical and clinical analysis on the use of carotenoids as chemopreventive and chemotherapeutic agents in breast cancer, highlighting the most recent results regarding the use of bacterioruberin from haloarchaea.

Thymoquinone attenuates phosphorylation of AKT to inhibit kidney cancer cell proliferation

Thymoquinone (Tq) is an active compound from Nigella sativa which is used in traditional medicine. The effect of Tq on kidney cancer and the pathway of action remain unproven. Herein, we report the anticancer properties of Tq on kidney cancer cells. Tq demonstrated anti-proliferative effects in A498 cells with a GI₅₀ value of 40.07 µM and Caki-1 cells with a GI50 of 51.04 µM by the MTT assay. Tq exhibited nuclear fragmentation and inhibited trans-endothelial migration of A498 and Caki-1 cells in a dose-responsive manner. Time-dependent increase in Annexin V-positive cells and sub-G₀ /G₁ cell population was observed post-Tq treatment. The compound increased Bax protein levels and reduced Bcl-2 protein levels dose dependently in cells, thereby favoring apoptosis. Tq decreased the phosphorylation of Akt in both kidney cell types. The results suggest effective anticancer activity of Tq on kidney cancer cells which may be mediated by the Akt pathway. PRACTICAL APPLICATIONS: Results from the current investigation will through more light on the mechanistic pathway of Tq activity on the inhibition of kidney cancer cell proliferation. The output of this preclinical in vitro study may be translated into better chemotherapeutics of Tq and its analogs to treat kidney cancer. However, a detailed investigation on in vivo models is recommended.

Umbelliferone β-d-galactopyranoside inhibits chemically induced renal carcinogenesis via alteration of oxidative stress, hyperproliferation and inflammation: possible role of NF-κB

Umbelliferone (7-hydroxycoumarin) compound possesses strong anti-inflammatory and free radical scavenging activity.

Anticancer Activity of Tabernaemontana coronaria against Carcinogen Induced Clear Cell Renal Cell Carcinoma

Medicinal plants have been used for treatment of various ailments since time immemorial. Tabernaemontana coronaria is a flowering plant belonging to Apocynaceae family. Considering the very good antioxidant properties of Tabernaemontana coronaria, the anticancer property of the ethanolic extract was evaluated against DEN and Fe-NTA induced clear cell renal cell carcinoma. A group of male rats were induced with single intraperitoneal injection of DEN (200 mg/kg bw) and followed by Fe-NTA (9 mg Fe/kg bw) twice a week for 24 weeks. Another set of two groups were induced with carcinogens and treated with plant extracts (200 and 400 mg/kg bw), respectively. Further two sets of rats were treated with only the plant extracts. The therapeutic efficacy of the ethanolic extract of Tabernaemontana coronaria was observed in terms of normalization of altered renal oxidative stress parameters like LPO and enzymic and nonenzymic antioxidants in kidney of rats. These results suggested that the plant extract could act against DEN and Fe-NTA induced clear cell renal cell carcinoma in male rats by a mechanism related to its antioxidant properties which was confirmed by histopathological studies.

Cancer chemoprevention by carotenoids

Carotenoids are natural fat-soluble pigments that provide bright coloration to plants and animals. Dietary intake of carotenoids is inversely associated with the risk of a variety of cancers in different tissues. Preclinical studies have shown that some carotenoids have potent antitumor effects both in vitro and in vivo, suggesting potential preventive and/or therapeutic roles for the compounds. Since chemoprevention is one of the most important strategies in the control of cancer development, molecular mechanism-based cancer chemoprevention using carotenoids seems to be an attractive approach. Various carotenoids, such as β-carotene, a-carotene, lycopene, lutein, zeaxanthin, β-cryptoxanthin, fucoxanthin, canthaxanthin and astaxanthin, have been proven to have anti-carcinogenic activity in several tissues, although high doses of β-carotene failed to exhibit chemopreventive activity in clinical trials. In this review, cancer prevention using carotenoids are reviewed and the possible mechanisms of action are described.

Anticancer Activity of an Indian Medicinal Plant, Alstonia scholaris, on Skin Carcinogenesis in Mice

Alstonia scholaris, commonly known as sapthaparna, has been used for centuries in Ayurvedic medicine for treatment of various disorders. The objective of this study was to investigate the possible chemopreventive and anti-oxidative properties of this medicinal plant on two-stage process of skin carcinogenesis induced by a single application of 7, 12-dimethyabenz(a)anthrecene (100 lg/100 ll acetone), and two weeks later, promoted by repeated application of croton oil (1% in acetone/thrice a week) till the end of the experiment (16 weeks) in Swiss albino mice.The tumor incidence, tumor yield, tumor burden and cumulative number of papillomas were found to be higher in the carcinogen treated control (without ASE treatment) as compared to experimental animals (ASE treated). Furthermore, a significant increase in reduced glutathione, superoxide dismutase and catalase but decrease in lipid peroxidation was measured in ASE administered experimental groups than the carcinogen treated control. The present study demonstrates the chemopreventive potential of Alstonia scholaris bark extract in DMBA-induced skin tumorigenesis in Swiss albino mice.

Effects of calorie restriction on chromosomal stability in rhesus monkeys (Macaca mulatta)

The basic tenet of several theories on aging is increasing genomic instability resulting from interactions with the environment. Chromosomal aberrations have been used as classic examples of increasing genomic instability since they demonstrate an increase in numerical and structural abnormalities with age in many species including humans. This accumulating damage may augment many aging processes and initiate age-related diseases, such as neoplasias. Calorie restriction (CR) is one of the most robust interventions for reducing the frequency of age-related diseases and for extending life span in many short-lived organisms. However, the mechanisms for the anti-aging effects of CR are not yet well understood. A study of rhesus monkeys was begun in 1987 to determine if CR is also effective in reducing the frequency of age-related diseases and retarding aging in a long-lived mammal. Male monkeys were begun on the diet in 1987, and females were added in 1992 to examine a possible difference in response to CR by sex. The CR monkeys have been maintained for over 10 years on a low-fat nutritional diet that provides a 30% calorie reduction compared to a control (CON) group. Because of the greater similarity of nonhuman primates to humans in life span and environmental responses to diet compared with those of rodents, the rhesus monkey provides an excellent model for the effects of CR in humans. This study examined the effects of CR on chromosomal instability with aging. Significant age effects were found in both CR and CON groups for the number of cells with aneuploidy: old animals had a higher loss and a higher gain than young animals. However, there was no effect of age on chromosomal breakage or structural aberrations in either diet group. Diet had only one significant effect: the CR group had a higher frequency of chromatid gaps than did the CON group. CR, implemented in adult rhesus monkeys, does not have a major effect on the reduction of numerical or structural aberrations related to aging.

Anticarcinogenic effect of Nymphaea alba against oxidative damage, hyperproliferative response and renal carcinogenesis in Wistar rats

The present study investigates the prophylactic effect of Nymphaea alba against ferric nitrilotriacetate (Fe-NTA)-induced renal oxidative stress, hyperproliferative response and renal carcinogenesis in Wistar rats. Treatment with Fe-NTA (9 mg Fe/kg body weight, intraperitoneally) enhanced iron-ascorbate-induced renal lipid peroxidation, xanthine oxidase, gamma-glutamyl transpeptidase and hydrogen peroxide (H2O2) generation with reduction in renal glutathione content, antioxidant enzymes, viz., glutathione peroxidase, glutathione reductase, catalase, glucose-6-phosphate dehydrogenase and phase-II metabolising enzymes such as glutathione-S-transferase and quinone reductase. It also elevated the levels of blood urea nitrogen, serum creatinine, ornithine decarboxylase (ODC) activity and thymidine [3H] incorporation into renal DNA. It also enhanced DEN-initiated renal carcinogenesis by increasing the percentage incidence of renal tumors. Treatment of rats orally with N. alba (100 and 200 mg/kg body weight) resulted in significant decrease in gamma-glutamyl transpeptidase, lipid peroxidation, xanthine oxidase, H2O2 generation, blood urea nitrogen, serum creatinine, renal ODC activity, DNA synthesis (p < 0.001) and incidence of tumors. Renal glutathione content (p < 0.01), glutathione metabolizing enzymes (p < 0.001) and antioxidant enzymes were also recovered to significant level (p < 0.001). Thus, our results show that N. alba is a potent chemopreventive agent and suppresses Fe-NTA-induced oxidative stress, hyperproliferative response and renal carcinogenesis in Wistar rats.

Inhibition of B(a)P induced strand breaks in presence of curcumin

Incidence of cancer at different sites may be related to oxidative damage to host genome by genotoxicants. These oxidative actions may be modified by phytochemicals present in foods. The non-nutritive dietary constituents which possess antimutagenic property appear to be promising chemopreventive agents. This study reports the protective effect of curcumin on B(a)P induced DNA damage in human peripheral blood lymphocyte cells. The study group consisted of 10 male smokers, 10 non-smokers and 10 non-smoking females aged between 25 and 45. The DNA damage was assessed using comet assay. In all the groups curcumin showed a dose-dependent inhibitory effect. The effect appeared to be sex dependent. There was no correlation between DNA damage and GST-Mu levels and levels of micronutrients namely Vitamins A, E and beta carotene. The results of this study are in line with our earlier observations on turmeric/curcumin as a potential chemopreventer.

Assessment of pro-oxidant activity of foods by kinetic analysis of crocin bleaching

The pro-oxidant activity of potent oxidants and foods was determined using the kinetic analysis of crocin bleaching. In its reduced form, crocin has an absorption band at 443 nm, which disappears upon oxidation by a generic radical species. Hydroxyl radicals generated by hydrogen peroxide, peroxyl radicals from ABAP, and the stable free radical DPPH(*) were allowed to react with crocin in an aqueous solution at 40 degrees C. Pro-oxidant activity was taken as the ratio between the decrease in crocin absorbance at 5 min and the relevant oxidant concentration. The test proposed was used to evaluate the pro-oxidant activity of widely consumed foods such as pasteurized skim milk and bread. They both exerted significant pro-oxidant activities, which were attributed to the early nonenzymatic browning products formed upon heat treatment.

Anti-tumor promoting activity of Asteracantha longifolia against experimental hepatocarcinogenesis in rats

Vegetables, natural products of plant origin and numerous non-nutritive dietary constituents have been shown to play a salutary role in cancer chemoprevention. The present study aims to evaluate the chemopreventive efficacy of the methanol fraction of Asteracantha longifolia seed extract against development of 2-acetylaminofluorene (2-AAF)-selected gamma-glutamyl transpeptidase (gamma-GT)-positive foci following diethylnitrosamine (DEN) initiation. Treatment of rats with doses 200 and 400 mg/kg body weight of methanol extract of A. longifolia seeds on alternate days, subsequent to carcinogen treatment, for 6 weeks significantly reduced the incidence and size distribution of gamma-GT-positive foci and tumor formation. Administration of A. longifolia seeds significantly (P<0.001) ameliorated the activities of antioxidant enzymes, glutathione peroxidase (GPx) and catalase (CAT), in a dose-dependent manner. Prophylactic administration of seed extract simultaneous to 2-AAF in the diet, at same doses, significantly suppressed 2-AAF and partial hepatectomy (PH)-induced ornithine decarboxylase (ODC) activity and [(3)H]thymidine incorporation into hepatic DNA, in a dose-dependent manner. Assimilation of the quantitative foci data together with the findings of the modulation of tumor promoting markers give ample evidence to the anti-tumor promoting potential of A. longifolia seeds against chemically-induced hepatocarcinogenesis in Wistar rats.