Chemopreventive Agents
David E. Thurston, Ilona Pysz in Chemistry and Pharmacology of Anticancer Drugs, 2021
A major challenge that has faced the investigation of chemopreventive agents is the difficulty in developing suitable in vitro laboratory screens. For example, while it is possible to use assays based on enzymes or whole cells to screen for compounds that enhance a specific type of metabolism or cell signaling pathway, there is no guarantee that up- or down-regulation of that particular pathway in vivo will result in the suppression of carcinogenesis. A further complication is that some precarcinogens may not be activated by the same metabolic pathway in animal models or humans. Moreover, even well-developed in vitro assays cannot imitate the complexities of the tumor microenvironment, making it impossible to accurately determine how particular compounds might exert their anticarcinogenic effects in a human subject. There is also the potential problem of synergy with mixtures of compounds from plant extracts, with one compound in a mixture enhancing the activity (and sometimes reducing) the activity of another, all of which increases the difficulties of identifying and isolating single compounds with clearly identifiable chemopreventive activity.
Tin, Tumors, and the Thymus Gland*
Nate F. Cardarelli in Tin as a Vital Nutrient:, 2019
A large number of organotin compounds have been screened by the National Cancer Institute.21 A number have shown encouraging anticarcinogenic properties, the majority are neutral, and a few have shown adverse effects. The NCI tests indicate that the dialkyl tin compounds offer the best chance of success,22 but oral administration of organotin compounds has favored using the trialkyltins as antitumoral agents.13,19 It is possible that the trialkyltins are better assimilated by the animals, dealkylated, and converted in a more biologically active species.15 Many OTC move preferentially to the tumor membrane but do not penetrate it.23,24 Analyses of tumors have shown that the tin content is considerably less than that of nontumoral tissue.5,25,26
Food Interactions, Sirtuins, Genes, Homeostasis, and General Discussion
Chuong Pham-Huy, Bruno Pham Huy in Food and Lifestyle in Health and Disease, 2022
Although high doses of single phytochemicals may show potent anticarcinogenic effects, the chemo-preventive properties of interactions among various dietary ingredients that potentiate the activities of any single constituent may better explain the observed preventive effect of whole foods and diets in many epidemiological studies (4). Natural remedy advocates are constantly recommending multiple supplements from various plant or herb extractions. For example, curcumin, a strong antioxidant of turmeric spice, is a potent anticarcinogen in vitro. But in humans, this property becomes weak because curcumin is poorly absorbed by the small intestine, thereby decreasing its efficacy in the prevention or treatment of cancer, inflammatory diseases, and CVDs. However, when turmeric is eaten in the same time with black pepper or galangal spice, the bioavailability of curcumin is now multiplied by 100 to 1,000 times (see Chapter 5, monograph Turmeric). Other examples of synergy between different foods are abundant. For example, resveratrol, a polyphenol present in red grape and red wine, can protect cancer and cardiovascular diseases by activating sirtuins. In contrast, resveratrol supplement alone does not give this same healthy effect as red grapes because in red grapes, there are the coenzyme NAD+ and other phytonutrients that might help resveratrol to activate sirtuins.
Saikosaponin D: review on the antitumour effects, toxicity and pharmacokinetics
Published in Pharmaceutical Biology, 2021
Piao Zhou, Wei Shi, Xiao-Yan He, Quan-Yu Du, Fei Wang, Jing Guo
Although SSD is a natural substance with great antitumour potential, we should use it on the premise of certain understanding of its toxicity to ensure the safety of medication. Currently, the toxicological effects of SSD found in studies include hepatotoxicity, neurotoxicity, haemolysis and cardiotoxicity, and according to the related research results, these toxic effects are mainly mediated by cytotoxic mechanisms. It is not difficult to see that the mechanisms of the toxic and adverse effects of SSD discovered are basically the same as those of its antitumour activities. As is known to all, the use of anticarcinogen to kill cancer cells will inevitably cause damage to some normal cells. Moreover, natural chemicals derived from plants are thought to be less toxic to normal cells in organisms than chemosynthetic drugs and have greater potential safety as anticarcinogens (Li et al. 2015; Gezici and Şekeroğlu 2019).
The Association of Dietary Approaches to Stop Hypertension (DASH) Diet with the Risk of Colorectal Cancer: A Meta-Analysis of Observational Studies
Published in Nutrition and Cancer, 2020
Reza Mohseni, Fatemeh Mohseni, Shahab Alizadeh, Soheil Abbasi
Vegetables and fruits consumption is proposed in DASH diet due to their antioxidants, fiber, vitamins, and minerals content. In a meta-analysis study, high intake of vegetables, fruits, and vegetables and fruits combined were associated with reductions in colorectal cancer risk (42). There are several potential mechanisms to explain the observed inverse association between vegetables and fruits consumption and colorectal cancer risk. First, vegetables and fruits are good sources of fiber that can prevent colorectal cancer. Secondly, vegetables and fruits are rich sources of folate, which has been associated with lower risk of colorectal cancer (43,44). Folate is necessary for synthesis of thymine and plays a key role in DNA methylation. Folate deficiency can cause misincorporation of uracil instead of thymine during DNA replication which results in increasing the number of chromosomal breaks and improper DNA methylation leads to abnormal gene expression that are known to occur in multiple types of cancer (45–48). Thirdly, fruits and vegetables are good sources anticarcinogenic agents including various vitamins, minerals, antioxidants and other bioactive compounds which may prevent cancer by the induction of detoxification enzymes and reduction of oxidative stress and inflammation (49). Finally, high intake of vegetables and fruits can also decrease the risk of obesity (50,51) which is an important risk factor for colorectal cancer (52).
Effects of Coffee, Black Tea and Green Tea Consumption on the Risk of Non-Hodgkin’s Lymphoma: A Systematic Review and Dose–Response Meta-Analysis of Observational Studies
Published in Nutrition and Cancer, 2019
Hanifeh Mirtavoos-Mahyari, Pouya Salehipour, Mohammad Parohan, Alireza Sadeghi
In the present meta-analysis, a slightly increased risk of NHL was observed among heavy coffee drinkers (above ∼4 cups/day). The impact of coffee intake on the risk of NHL might be due to a balance between the potential oncogenic effect of chemicals and the protective effects of anticarcinogenic compounds (37,38). Moreover, the increased risk of NHL observed among heavy coffee consumers suggest that coffee drinking may be associated with one or several lifestyle factors that are the true risk factors for NHL such as tobacco smoking, unhealthy dietary habits, low physical activity, obesity, and sleep disorders (40–42). The possibility that tobacco smoking, unhealthy dietary habits and other risk factors could reduce the anticarcinogenic effect, thus enhancing the potential effect of the oncogenic compounds cannot be completely excluded.
Related Knowledge Centers
- Clinical Trial
- Curative Care
- DNA
- In Vitro
- In Vivo
- Carcinogen
- Cancer
- Chemotherapy
- Preventive Healthcare
- Radical