Cancer chemoprevention. A new way to treat cancer before it happens

Antitumor efficacy of tangeretin by targeting the oxidative stress mediated on 7,12-dimethylbenz(a) anthracene-induced proliferative breast cancer in Sprague-Dawley rats

PURPOSE

The aim of the present study was to assess the chemopreventive and chemotherapeutic efficacy of tangeretin on DMBA-induced oxidative stress in breast cancer-bearing Sprague-Dawley rats.

METHODS

In this study, the experimental animals were divided into five groups of six animals each. Group I was control, Group II was DMBA-induced breast cancer-bearing rats, Group III was tangeretin pre-treated (50 mg/kg body weight for 30 days orally) breast cancer-bearing animals, Group IV was tangeretin post-treated (50 mg/kg body weight for 30 days orally) and Group V was tangeretin (50 mg/kg body weight) alone treated animals.

RESULTS

We have observed the general characteristics of cancer, oxidative stress markers, breast cancer marker, antioxidants and histopathological changes in the experimental animals. We have recorded the body weight, tumor weights, tumor volume and antitumor activity of tangeretin in the experimental animals. Oxidative stress markers, like NO and LPO, and breast cancer marker CEA levels were significantly (p < 0.001, p < 0.05) increased as well as the antioxidants like SOD, CAT, GPx, GST, GSH, ascorbic acid and α-tocopherol were found to be significantly (p < 0.05) decreased in cancer-bearing Group II animals. Whereas, the enzymic and non-enzymic antioxidant levels were found to be significantly decreased in cancer-bearing animals. However, in tangeretin pre-treated and post- treated animals, the levels of antioxidants and breast cancer marker were found to be significantly (p < 0.05) reduced with a concomitant increase in the activities of the antioxidants (p < 0.05). In tangeretin alone treated Group V animals, no significant changes were observed in the levels of antioxidants and breast cancer marker. These results were adequately supported by the histopathological studies in the mammary tissues of the experimental animals.

CONCLUSION

From this study, we conclude that the administration of tangeretin was found to be beneficial against DMBA-induced oxidative stress in breast cancer-bearing animals. Hence, we strongly suggest that tangeretin is effective and efficient candidate for the treatment of experimental breast cancer.

Chemopreventive potential of an ethyl acetate fraction from Curcuma longa is associated with upregulation of p57(kip2) and Rad9 in the PC-3M prostate cancer cell line

BACKGROUND

Turmeric (Curcuma longa) has been shown to possess anti-inflammatory, antioxidant and antitumor properties. However, despite the progress in research with C. longa, there is still a big lacuna in the information on the active principles and their molecular targets. More particularly very little is known about the role of cell cycle genes p57(kip2) and Rad9 during chemoprevention by turmeric and its derivatives especially in prostate cancer cell lines.

METHODS

Accordingly, in this study, we have examined the antitumor effect of several extracts of C. longa rhizomes by successive fractionation in clonogenic assays using highly metastatic PC-3M prostate cancer cell line.

RESULTS

A mixture of isopropyl alcohol: acetone: water: chloroform: and methanol extract of C. longa showed significant bioactivity. Further partition of this extract showed that bioactivity resides in the dichloromethane soluble fraction. Column chromatography of this fraction showed presence of biological activity only in ethyl acetate eluted fraction. HPLC, UV-Vis and Mass spectra studies showed presence three curcuminoids in this fraction besides few unidentified components.

CONCLUSIONS

From these observations it was concluded that the ethyl acetate fraction showed not only inhibition of colony forming ability of PC-3M cells but also up-regulated cell cycle genes p57(kip2) and Rad9 and further reduced the migration and invasive ability of prostate cancer cells.

Combinatorial cytotoxic effects of Curcuma longa and Zingiber officinale on the PC-3M prostate cancer cell line

BACKGROUND

Many plant-derived products exhibit potent chemopreventive activity against animal tumor models as well as rodent and human cancer cell lines. They have low side effects and toxicity and presumably modulate the factors that are critical for cell proliferation, differentiation, senescence and apoptosis. The present study investigates the effects of some medicinal plant extracts from generally recognized as safe plants that may be useful in the prevention and treatment of cancer.

METHODS

Clonogenic assays using logarithmically-growing cells were performed to test the effect. The cytotoxic effects of Curcuma longa and Zingiber officinale were studied using sulforhodamine B assay, tetrazolium dye assay, colony morphology and microscopic analysis.

RESULTS

Out of the 13 lyophilized plant-derived extracts evaluated for growth-inhibitory effects on the PC-3M prostate cancer cell line, two extracts derived from C. longa and Z. officinale showed significant inhibitory effects on colony-forming ability. The individual and augmentative effects of these two extracts were tested for their narrow range effective lower concentration on PC-3M in clonogenic assays. At relatively lower concentrations, C. longa showed significant inhibition of colony formation in clonogenic assays; whereas at same concentrations Z. officinale showed only moderate inhibitory effects. However, when both the agents were tested together at the same concentrations, the combined effects were much more significant than their individual ones. On normal prostate epithelial cells both C. longa and Z. officinale had similar effects but at a lower magnitude. These observations were confirmed by several cytotoxicity assays involving the morphological appearance of the colonies, microscopic observations, per cent inhibition in comparison to control by sulforhodamine B and tetrazolium dye assay.

CONCLUSIONS

From these observations, it was concluded that the combined effects of C. longa and Z. officinale are much greater than their individual effects, suggesting the role of multiple components and their synergistic mode of actions to elicit stronger beneficial effects.

Molecular mechanisms involved in chemoprevention of black raspberry extracts: from transcription factors to their target genes

Berries have attracted attention for their chemopreventive activities in last a few years. Dietary freeze-dried blackberries have been shown to reduce esophagus and colon cancer development induced by chemical carcinogen in rodents. To elucidate molecular mechanisms involved in chemoprevention by berry extracts, we employed mouse epidermal Cl 41 cell line, a well-characterized in vitro model in tumor promotion studies. Pretreatment of Cl 41 cells with methanol-extracted blackberry fraction RO-ME resulted in a dramatical inhibition of B(a)PDE-induced activation of AP-1 and NFkB, and expression of VEGF and COX-2. The inhibitory effects of RO-ME on B(a)PDE-induced activation of AP-1 and NFkappaB appear to be mediated via inhibition of MAPKs and IkappaBalpha phosphorylation, respectively. In view of the important roles of AP-1, NFkappaB, VEGF and COX-2 in tumor promotion/progression, and VEGF and COX-2 are target of AP-1 and NFkappaB, we anticipate that the ability of black raspberries to inhibit tumor development may be mediated by impairing signal transduction pathways leading to activation of AP-1 and NFkappaB, subsequently resulting in down-regulation of VEGF and COX-2 expression. The RO-ME fraction appears to be the major fraction responsible for the inhibitory activity of black raspberries.

Phase IIa chemoprevention trial of green tea polyphenols in high-risk individuals of liver cancer: modulation of urinary excretion of green tea polyphenols and 8-hydroxydeoxyguanosine

Modulation of urinary excretion of green tea polyphenols (GTPs) and oxidative DNA damage biomarker, 8-hydroxydeoxyguanosine (8-OHdG), were assessed in urine samples collected from a randomized, double-blinded and placebo-controlled phase IIa chemoprevention trial with GTP in 124 individuals. These individuals were sero-positive for both HBsAg and aflatoxin-albumin adducts, and took GTP capsules daily at doses of 500 mg, 1000 mg or a placebo for 3 months. Twenty-four hour urine samples were collected before the intervention and at the first and third month of the study. Urinary excretion of 8-OHdG and GTP components was measured by HPLC-CoulArray electrochemical detection. The baseline levels of 8-OHdG and GTP components among the three groups showed homogeneity (P > 0.70), and a non-significant fluctuation was observed in the placebo group over the 3 months (P > 0.30). In GTP-treated groups, epigallocatechin (EGC) and epicatechin (EC) levels displayed significant and dose-dependent increases in both the 500 mg group and 1000 mg group (P < 0.05). The 8-OHdG levels did not differ between the three groups at the 1 month collection, with medians of 1.83, 2.08 and 1.86 ng/mg-creatinine for placebo, 500 and 1000 mg group, respectively (P = 0.999). At the end of the 3 months' intervention, 8-OHdG levels decreased significantly in both GTP-treated groups, with medians of 2.02, 1.03 and 1.15 ng/mg-creatinine for placebo, 500 mg and 1000 mg group, respectively (P = 0.007). These results suggest that urinary excretions of EGC and EC can serve as practical biomarkers for green tea consumption in human populations. The results also suggest that chemoprevention with GTP is effective in diminishing oxidative DNA damage.

Inhibition of AP-1 and Neoplastic Transformation by Fresh Apple Peel Extract

Consumption of fruits and vegetables has been associated with a low incidence of cancers and other chronic diseases. Previous studies suggested that fresh apples inhibit tumor cell proliferation. Here we report that oral administration of apple peel extracts decreased the number of nonmalignant and malignant skin tumors per mouse induced by 12-O-tetradecanolyphorbol-13-acetate (TPA) in 7,12-dimethylbenz(a)anthracene-initiated mouse skin. ESR analysis indicated that apple extract strongly scavenged hydroxyl (OH) and superoxide (O(2)(-)) radicals. Mechanistic studies showed that pretreatment with apple peel extract inhibited AP-1 transactivation induced by ultraviolet B irradiation or TPA in JB6 cells and AP-1-luciferase reporter transgenic mice. This inhibitory effect appears to be mediated by the inhibition of ERKs and JNK activity. The results provide the first evidence that an extract from fresh apple peel extract may inhibit tumor promoter-induced carcinogenesis and associated cell signaling, and suggest that the chemopreventive effects of fresh apple may be through its antioxidant properties by blocking reactive oxygen species-mediated AP-1-MAPK activation.

Inhibition of cellular transformation by berry extracts

Recent studies have examined and demonstrated the potential cancer chemopreventive activity of freeze-dried berries including strawberries and black raspberries. Although ellagic acid, an abundant component in these berries, has been shown to inhibit carcinogenesis both in vivo and in vitro, several studies have reported that other compounds in the berries may also contribute to the observed inhibitory effect. In the present study, freeze-dried strawberries (Fragara ananassa, FA) or black raspberries (Rubus ursinus, RU) were extracted, partitioned and chromatographed into several fractions (FA-F001, FA-F003, FA-F004, FA-F005, FA-DM, FA-ME from strawberries and RU-F001, RU-F003, RU-F004, RU-F005, RU-DM, RU-ME from black raspberries). These extracts, along with ellagic acid, were analyzed for anti-transformation activity in the Syrian hamster embryo (SHE) cell transformation model. None of the extracts nor ellagic acid by themselves produced an increase in morphological transformation. For assessment of chemopreventive activity, SHE cells were treated with each agent and benzo[a]pyrene (B[a]P) for 7 days. Ellagic acid, FA-ME and RU-ME fractions produced a dose-dependent decrease in transformation compared with B[a]P treatment only, while other fractions failed to induce a significant decrease. Ellagic acid, FA-ME and RU-ME were further examined using a 24 h co-treatment with B[a]P or a 6 day treatment following 24 h with B[a]P. Ellagic acid showed inhibitory ability in both protocols. FA-ME and RU-ME significantly reduced B[a]P-induced transformation only when co-treated with B[a]P for 24 h. These results suggest that a methanol extract from strawberries and black raspberries may display chemopreventive activity. The possible mechanism by which these methanol fractions (FA-ME, RU-ME) inhibited cell transformation appear to involve interference of uptake, activation, detoxification of B[a]P and/or intervention of DNA binding and DNA repair.

Diet and lung cancer: a new approach

Lung cancer is one of major public health problems facing the world today, owing to the high incidence of the disease and its poor prognosis. Although the principal cause of lung cancer is tobacco use, smokers find it extremely difficult to quit the habit. Hence, there is a need to take action targeted at other risk factors for this disease. One such factor is diet, which is known to be able to raise or lower the risk of lung cancer. This paper seeks to complement other reviews in the field and to shed more light both on the influence that dietary factors may have upon the occurrence of this neoplasm and on the causes of this possible effect.

Communication skills for preventive interventions

Effective communication relevant to preventive services and practices has at its basis the physician's skills in not only basic history taking and data collection but also relationship building, facilitation, negotiation, and partnership. These skills, fundamental to doctor-patient communication, are now routinely and systematically taught in many U.S. medical schools. This article defines and examines a communication model for enhancing the provision and adoption of preventive practices in the primary care setting and discusses teaching that model in the medical school context. Within the office visit, broad areas for communication tasks important to providing preventive services are defined as: (1) the medical interview and preventive counseling; (2) working with patients to change unhealthy behaviors, promote healthy behaviors, and enhance adherence; and (3) communication related to office procedures for screening and prevention. Within each of these areas, communication and counseling skills and approaches are defined, and examples of associated prevention activities are provided. Methods for integrating communication skills for prevention into the medical school curriculum are discussed, and examples at Dartmouth, Brown, and MCP Hahnemann medical schools are presented.

Effects of beta-carotene on antioxidant enzyme activity, intracellular reactive oxygen and membrane integrity within post confluent Caco-2 intestinal cells

As encountered with a plethora of other natural products, the antioxidant activity of beta-carotene has been proposed as one of the mechanisms by which diets rich in this pro-vitamin A active carotenoid apparently afford chemoprevention. Here, we report the ability of beta-carotene to alter endogenous reactive oxygen levels and antioxidant defences within non-stressed 'differentiated' monolayers of an intestinal epithelial cell line (Caco-2) and to subsequently effect resistance to general oxidative insult. The differentiated monolayers efficiently absorbed beta-carotene. Between 3 and 8 days post confluence, cultures exhibited a progressive increase in antioxidant enzyme activity and a corresponding reduction to intracellular ROS levels. The profile for antioxidant enzyme activity was unaffected by sustained daily supplementation with beta-carotene. However, after two daily treatments with 50 microM beta-carotene intracellular ROS levels were significantly reduced and there was a trend towards reduced intracellular ROS within monolayers subject to five daily treatments with 0.5 and 5 microM beta-carotene. Prolonged supplementation with 0.1 and 0.5 microM beta-carotene or short supplementation periods with 5 and 50 microM beta-carotene did not alter susceptibility to H(2)O(2). However, cultures treated daily between 3 and 8 days post confluence with 5 or 50 microM beta-carotene exhibited enhanced LDH release, increased non-adherence and enhanced Trypan blue staining when challenged with 10 mM H(2)O(2). In the absence of H(2)O(2), the beta-carotene treatments were not overtly toxic to the monolayers. These results indicate that beta-carotene does not enhance antioxidant defences within Caco-2 monolayers. The enhancement of H(2)O(2) toxicity by persistent, high doses of beta-carotene may contribute to the failure of this carotenoid to protect high risk individuals from certain degenerative conditions.