Anti-Cancer Agents in Medicinal Chemistry (v.12, #10)

Cancer Prevention with Promising Natural Products: Mechanisms of Action and Molecular Targets by Poyil Pratheeshkumar, Chakkenchath Sreekala, Zhuo Zhang, Amit Budhraja, Songze Ding, Young-Ok Son, Xin Wang, Andrew Hitron, Kim Hyun-Jung, Lei Wang, Jeong-Chae Lee, Xianglin Shi (1159-1184).
Cancer is the second leading cause of death worldwide. There is greater need for more effective and less toxic therapeutic and preventive strategies. Natural products are becoming an important research area for novel and bioactive molecules for drug discovery. Phytochemicals and dietary compounds have been used for the treatment of cancer throughout history due to their safety, low toxicity, and general availability. Many active phytochemicals are in human clinical trials. Studies have indicated that daily consumption of dietary phytochemicals have cancer protective effects against carcinogens. They can inhibit, delay, or reverse carcinogenesis by inducing detoxifying and antioxidant enzymes systems, regulating inflammatory and proliferative signaling pathways, and inducing cell cycle arrest and apoptosis. Epidemiological studies have also revealed that high dietary intakes of fruits and vegetables reduce the risk of cancer. This review discusses potential natural cancer preventive compounds, their molecular targets, and their mechanisms of actions.

Chemoprevention of Breast Cancer by Dietary Compounds by Aditi S. Vadodkar, Suman Suman, Rajkumar Lakshmanaswamy, Chendil Damodaran (1185-1202).
Breast cancer is the leading cause of cancer-related deaths in women in the United States and many other countries. There is an immediate need for more effective and less toxic therapeutic and preventive strategies for many cancers, especially for breast cancer. Natural products are being tested with a hope of identifying novel potent molecules as anticancer agents. Phytochemicals and dietary compounds have been used for the treatment of various illnesses throughout history due to their safety, low toxicity, and general availability. Currently, many active phytochemicals are in clinical trials. Preclinical and clinical studies have indicated that daily consumption of dietary phytochemicals reduces the risk of several cancers. Phytochemicals can inhibit, delay, or reverse carcinogenesis by inducing detoxifying and antioxidant enzymes, by regulating inflammatory/proliferative signaling pathways, and by inducing apoptosis. This review article describes some of the potential natural cancer preventive compounds, along with a mechanistic discussion of their interactions with key cellular signal transduction pathways as well as their contribution to the suppression of breast cancer cell growth.

Epigenetic Mechanisms Underlying Diet-Sourced Compounds in the Prevention and Treatment of Gastrointestinal Cancer by Rebecca W. Knackstedt, Vondina R. Moseley, Michael J. Wargovich (1203-1210).
The development of colon cancer, the third most diagnosed cancer and third leading cause of cancer deaths in the United States, can be influenced by genetic predispositions and environmental exposures. As 80% of colon cancer cases are sporadic in nature, much interest lies in determining risk factors that may foster its development, as well as identifying compounds that could inhibit colon cancer development or halt progression. A major risk factor for sporadic colon cancer is a high fat, Western diet which has been linked to a cancer-prone, pro-inflammatory state. Cultures which place an emphasis on fresh fruits and vegetables demonstrate lower colon cancer incidences. Diet not only has the potential to encourage colon cancer development, but recent evidence demonstrates that certain dietary natural products can halt colon cancer development and progression via epigenetic regulation. Epigenetic dysregulation may contribute to inflammation-driven diseases, such as cancer, and can lead to the inappropriate silencing of genes necessary to inhibit cancer development. Natural compounds have shown the ability to reverse epigenetic dysregulation in in vitro and in vivo models. As current allopathic medicines aimed at reversing epigenetic silencing are accompanied with the risk of toxicity and side effects, much interest lies in being able to harness the disease preventing properties in natural products. Here, we discuss the epidemiology of colon cancer, describe the need for natural approaches to inhibit disease development and highlight natural products which have been shown to inhibit gastrointestinal cancer initiation and progression in vitro or in vivo through epigenetic modulation.

Unifying Mechanisms of Action of the Anticancer Activities of Triterpenoids and Synthetic Analogs by Stephen H. Safe, Paul L. Prather, Lisa K. Brents, Gayathri Chadalapaka, Indira Jutooru (1211-1220).
Triterpenoids such as betulinic acid (BA) and synthetic analogs of oleanolic acid [2-cyano-3,12-dioxooleana-1,9-dien-28-oic acid (CDDO)] and glycyrrhetinic acid [2-cyano-3,11-dioxo-18β-oleana-1,12-dien-30-oc acid (CDODA)] are potent anticancer agents that exhibit antiproliferative, antiangiogenic, anti-inflammatory and pro-apoptotic activities. Although their effects on multiple pathways have been reported, unifying mechanisms of action have not been reported. Studies in this laboratory have now demonstrated that several triterpenoids including BA and some derivatives, celastrol, methyl ursolate, β-boswellic acid derivatives, and the synthetic analogs CDDO, CDODA and their esters decreased expression of specificity protein (Sp) transcription factors and several pro-oncogenic Spregulated genes in multiple cancer cell lines. The mechanisms of this response are both compound- and cell context-dependent and include activation of both proteasome-dependent and -independent pathways. Triterpenoid-mediated induction of reactive oxygen species (ROS) has now been characterized as an important proteasome-independent pathway for downregulation of Sp transcription factors. ROS decreases expression of microRNA-27a (miR-27a) and miR-20a/miR-17-5p and this results in the induction of the transcriptional “Sprepressors” ZBTB10 and ZBTB4, respectively, which in turn downregulate Sp and Sp-regulated genes. Triterpenoids also activate or deactive nuclear receptors and G-protein coupled receptors, and these pathways contribute to their antitumorigenic activity and may also play a role in targeting Sp1, Sp3 and Sp4 which are highly overexpressed in multiple cancers and appear to be important for maintaining the cancer phenotype.

Prevention of Colitis-associated Cancer: Natural Compounds that Target the IL-6 Soluble Receptor by Cate Moriasi, Dharmalingam Subramaniam, Shanjana Awasthi, Satish Ramalingam, Shrikant Anant (1221-1238).
The risk of developing colorectal cancer increases in patients with inflammatory bowel disease (IBD) and a growing body of evidence shows the critical role of interleukin (IL-6) in this process. IL-6 is both a pro- and anti-inflammatory cytokine whose effects are mediated through activation of STAT3. Recent studies have also demonstrated that IL-6 trans-signaling through its soluble receptor occurs in IBD and cancer. IL-6 trans-signaling therefore is emerging as an attractive approach to diminish the inflammatory signals in conditions of chronic inflammation. The purpose of cancer chemoprevention is to either delay the onset or progression from precancerous lesions. Natural compounds because of their low toxicity render themselves excellent candidates that can be administered over the lifetime of an individual. With the focus of managing IBD over a long time and preventing onset of colitis-associated cancer, we believe that there should be increased research focus on identifying chemopreventive compounds that can render themselves to long term use possibly for the lifetime of predisposed individuals. Here, we review the role of IL-6 signaling in IBD and colitis-associated cancer and underscore the importance of searching for natural compounds that would target the IL-6 trans-signaling pathway as a way to diminish chronic inflammatory conditions in the gastrointestinal tract and possibly hamper the progression to colon cancer. We propose that effective screening and identification of natural chemopreventive compounds that target IL-6 trans-signaling has important implications for the development of optimal strategies against cancer development triggered by inflammation.

Anti-cancer and Other Bioactivities of Korean Angelica gigas Nakai (AGN) and Its Major Pyranocoumarin Compounds by Jinhui Zhang, Li Li, Cheng Jiang, Chengguo Xing, Sung-Hoon Kim, Junxuan Lu (1239-1254).
Korean Angelica gigas Nakai (AGN) is a major medicinal herb used in Asian countries such as Korea and China. Traditionally, its dried root has been used to treat anemia, pain, infection and articular rheumatism in Korea, most often through boiling in water to prepare the dosage forms. The pyranocoumarin compound decursin and its isomer decursinol angelate (DA) are the major chemical components in the alcoholic extracts of the root of AGN. The in vitro anti-tumor activities of decursin and/or DA against prostate cancer, lung cancer, breast cancer, colon cancer, bladder cancer, sarcoma, myeloma and leukemia have been increasingly reported in the past decade whereas the in vivo efficacy in mouse models was established only for a few organ sites. Preliminary pharmacokinetic studies by us and others in rodent models indicated that decursinol (DOH), which has much less in vitro direct anticancer activities by itself, is the major and rapid in vivo hydrolysis metabolite of both decursin and DA. Besides decursin, DA and DOH, other chemical components in AGN such as polysaccharides and polyacetylenes have been reported to exert anti-cancer and antiinflammation activities as well. We systematically reviewed the published literature on the anti-cancer and other bio-activities effects of AGN extract and decursin, DA and DOH, as well as other chemicals identified from AGN. Although a number of areas are identified that merit further investigation, one critical need is first-in-human studies of the pharmacokinetics of decursin/DA to determine whether humans differ from rodents in absorption and metabolism of these compounds.

The Cancer Preventive Effects of Edible Mushrooms by Tongtong Xu, Robert B. Beelman, Joshua D. Lambert (1255-1263).
An increasing body of scientific literature suggests that dietary components may exert cancer preventive effects. Tea, soy, cruciferous vegetables and other foods have been investigated for their cancer preventive potential. Some non-edible mushrooms like Reishi (Ganoderma lucidum) have a history use, both alone and in conjunction with standard therapies, for the treatment of various diseases including cancer in some cultures. They have shown efficacy in a number of scientific studies. By comparison, the potential cancer preventive effects of edible mushrooms have been less well-studied. With similar content of putative effective anticancer compounds such as polysaccharides, proteoglycans, steroids, etc., one might predict that edible mushrooms would also demonstrate anticancer and cancer preventive activity. In this review, available data for five commonly-consumed edible mushrooms: button mushrooms (Agaricus bisporus), A. blazei, oyster mushrooms (Pleurotus ostreatus), shiitake mushrooms (Lentinus edodes), and maitake (Grifola frondosa) mushrooms is discussed. The results of animal model and human intervention studies, as well as supporting in vitro mechanistic studies are critically evaluated. Weaknesses in the current data and topics for future work are highlighted.

Bioavailability and Pharmacokinetics of Genistein: Mechanistic Studies on its ADME by Zhen Yang, Kaustubh Kulkarni, Wei Zhu, Ming Hu (1264-1280).
Genistein, one of the most active natural flavonoids, exerts various biological effects including chemoprevention, antioxidation, antiproliferation and anticancer. More than 30 clinical trials of genistein with various disease indications have been conducted to evaluate its clinical efficacy. Based on many animals and human pharmacokinetic studies, it is well known that the most challenge issue for developing genistein as a chemoprevention agent is the low oral bioavailability, which may be the major reason relating to its ambiguous therapeutic effects and large interindividual variations in clinical trials. In order to better correlate pharmacokinetic to pharmacodynamics results in animals and clinical studies, an in-depth understanding of pharmacokinetic behavior of genistein and its ADME properties are needed. Numerous in vitro/in vivo ADME studies had been conducted to reveal the main factors contributing to the low oral bioavailability of genistein. Therefore, this review focuses on summarizing the most recent progress on mechanistic studies of genistein ADME and provides a systemic view of these processes to explain genistein pharmacokinetic behaviors in vivo. The better understanding of genistein ADME property may lead to development of proper strategy to improve genistein oral bioavailability via mechanism-based approaches.

Plants vs. Cancer: A Review on Natural Phytochemicals in Preventing and Treating Cancers and Their Druggability by Hu Wang, Tin Oo Khor, Limin Shu, Zheng-Yuan Su, Francisco Fuentes, Jong-Hun Lee, Ah-Ng Tony Kong (1281-1305).
Cancer remains to be one of the leading causes of death in the United States and around the world. The advent of modern drug-targeted therapies has undeniably improved cancer patients' cares. However, advanced metastasized cancer remains untreatable. Hence, continued searching for a safer and more effective chemoprevention and treatment is clearly needed for the improvement of the efficiency and to lower the treatment cost for cancer care. Cancer chemoprevention with natural phytochemical compounds is an emerging strategy to prevent, impede, delay, or cure cancer. This review summarizes the latest research in cancer chemoprevention and treatment using the bioactive components from natural plants. Relevant molecular mechanisms involved in the pharmacological effects of these phytochemicals are discussed. Pharmaceutical developmental challenges and opportunities in bringing the phytochemicals into the market are also explored. The authors wish to expand this research area not only for their scientific soundness, but also for their potential druggability.

Developing Phytoestrogens for Breast Cancer Prevention by Mandy M. Liu, Ying Huang, Jeffrey Wang (1306-1313).
Breast cancer is one of the most common types of cancer in women, and is the second leading cause of cancer-related deaths in the United States. Chemoprevention using phytoestrogens (PEs) for breast cancer may be a valid strategy. PEs are phytochemicals with estrogen-like structures and can be classified into four types: isoflavones, lignans, stilbenes and coumestans. They are widely distributed in diet and herbs and have shown anti-cancer activity via mechanisms including estrogen receptor modulation, aromatase inhibition, and anti-angiogenesis. Genistein, daidzein and resveratrol are some of the most studied PE examples. Quality control in product manufacturing and clinical study design is a critical issue in developing them as clinically effective chemopreventive agents for breast cancer.