Current Medicinal Chemistry - Volume 25, Issue 36, 2018

Background: The Mediterranean basin is one of the richest biodiversity areas in the world, and the use of medicinal plants for treating cancer in this area has been documented for generations in different cultures. Objective: To present and discuss the findings related to medicinal plants with confirmed data on active compounds and/or clear mode of action. Methods: We undertook a structured search of bibliography of peer-reviewed research literature using key words and a focused review question. Papers with sufficient quality were reviewed, their findings presented and integrated into a coherent, state of the art document on wild plants of the Middle East with anti-cancer activity. Results: 121 papers were included in the review, among them 10 define herbal medicine, 3 describe the status of cancer worldwide, 18 discuss biodiversity, chemodiversity, ethnopharmacological survey and conservation of medicinal plants, 12 describe well known natural products from plants used to treat cancer and 78 papers describe specific compounds and mode of action in different wild plants from the middle east, traditionally used to treat cancer. Conclusions: Confirmed data on active compounds and/or clear mode of action exist for several wild plants traditionally used in herbal medicine to treat cancer. Yet, medicinal plants were mainly gathered from the wild, resulting in some of the commonly used herbs becoming endangered species. Also, in many cases, the activity and biochemical profile of plants harvested over different time spans and ecosystems may vary. Rational cultivation may ensure optimized yield with a uniform high quality of products.

Background: For many years, anticancer polyphenols have attracted significant attention as substances that prevent tumor growth and progression. These compounds are simple phenolic acids, complex phenolic acids, such as caffeoylquinic acids, rosmarinic acid and its derivatives, stilbenes, flavones, isoflavones, and anthocyanins. Some compounds, such as tea and coffee polyphenols, can be produced in large quantities by traditional methods, while many others cannot. Methods: We reviewed the available literature regarding the biotechnological aspects of polyphenol production by cultured plant cells and described approaches that have been used to obtain high levels of anticancer polyphenols (resveratrol, podophyllotoxin, genistein, lithospermic acid B, and others). Additionally, we provide our view on bioengineering strategies that could be important for the further improvement of cell biosynthetic characteristics. Results: The main trend in the field is the activation of entire biosynthetic pathways based on a comprehensive knowledge of protein-protein interaction networks involved in the regulation of polyphenol biosynthesis. As an example, we consider the jasmonate subnetwork, which will be increasingly used by plant biotechnologists. The next-generation technologies to sustained polyphenol production involve manipulations with microRNAs and reproduction of rol-gene effects. Conclusion: Plant polyphenols play an important role in maintaining human health, and their role in the prevention of cancer will continue to grow. Targeting mechanisms involved in uncontrolled cancer cell proliferation will increasingly become the standard for cancer patients. Plant biotechnological studies aiming at producing anticancer compounds will be developed in parallel with these studies to provide a wider range of metabolites for each particular case.

Secondary metabolites from numerous plant sources have been developed as anti- cancer reagents and compounds such as resveratrol, podophyllotoxin and zerumbone are of particular importance in this regard. Since their de novo chemical synthesis is both arduous and commercially expensive, there has been an impetus to develop viable, biotechnological methods of production. Accordingly, this review focuses on the recent developments in the field, highlighting the use of micropropagation, cell suspension cultures, callus cultures, hairy root cultures, recombinant microbes and genetically modified higher plants. Optimization of media and culture conditions, precursor feeding, immobilization and the use of chemical or physical elicitation in various protocols has led to an increase in resveratrol and podophyllotoxin production. Heterologous gene transformation of higher plants with stilbene synthase derived from Arachis hypogaea or Vitis vinifera lead to resveratrol production with the concomitant increase in resistance to plant pathogens. Interestingly, genetic transformation of Podophyllum hexandrum and Linum flavum with Agrobacterium rhizogenes resulted in Ri-T-DNA gene(s)-mediated enhancement of podophyllotoxin production. Zerumbone yields from tissue cultured plantlets or from suspension cultures are generally low and these methods require further optimization. In microbes lacking the native resveratrol or zerumbone biosynthesis pathway, metabolic engineering required not only the introduction of several genes of the pathway, but also precursor feeding and optimization of gene expression to increase their production. Data pertaining to safety and toxicity testing are needed prior to use of these sources of anti-cancer compounds in therapy.

Background: Recent years have brought the dynamic development in studies of naphthoquinones obtained from plants, in vitro cultures and semi- or total synthesis. This review presents the hairy root cultures approach for producing naphthoquinones and summarizes their most recent anti-cancer investigations. Objective: This review aimed to define biotechnological strategies impacted on naphthoquinones production in hairy root cultures. Up to now the major source of shikonin/alkannin derivatives, rhinacanthins and ramentaceone is isolation from plant material, also derived via biotechnological methods. Moreover, the most recent anti-cancer activity studies on naphthoquinones which could be produced in hairy root cultures were outlined. Methods: For databases survey two selection criteria were used: (i) naphthoquinone could be produced in hairy roots, and (ii) it exhibits anti-cancer properties. Results: Ninety two papers were included in the review, thirty described biotechnological approaches enhancing naphthoquinones production, among them twenty seven were dedicated to hairy root cultures. Forty papers outlined the anti-cancer activity of targeted naphthoquinones including the type of cancer and bioassays description. The synergistic effect of natural naphthoquinones and other anti-cancer therapies was reviewed and toxicity of natural naphthoquinones and plant extracts was discussed. The review highlights tendencies in hairy root investigations and indicates the possible future research directions for improving biotechnological production efficacy. Conclusion: This review demonstrates a great potential of hairy root cultures for naphthoquinones production, which could be furtherly developed for future medical purposes, especially as anti-cancer agents. This area of plant biotechnology will be surely still developed with traditional and new strategies.

Polyphenols are a group of water-soluble organic compounds, mainly of natural origin. The compounds having about 5-7 aromatic rings and more than 12 phenolic hydroxyl groups are classified as polyphenols. These are the antioxidants which protect the body from oxidative damage. In plants, they are the secondary metabolites produced as a defense mechanism against stress factors. Antioxidant property of polyphenols is suggested to provide protection against many diseases associated with reactive oxygen species (ROS), including cancer. Various studies carried out across the world have suggested that polyphenols can inhibit the tumor generation, induce apoptosis in cancer cells and interfere in progression of tumors. This group of wonder compounds is present in surplus in natural plants and food products. Intake of polyphenols through diet can scavenge ROS and thus can help in cancer prevention. The plant derived products can also be used along with conventional chemotherapy to enhance the chemopreventive effects. The present review focuses on various in vitro and in vivo studies carried out to assess the anti-carcinogenic potential of polyphenols present in our food. Also, the pathways involved in cancer chemopreventive effects of various subclasses (flavonoids, lignans, stilbenes and phenolic acids) of polyphenols are discussed.

Cancer is one of the leading causes of death worldwide, and current research has focused on the discovery of novel approaches to effectively treat this disease. Recently, a considerable number of clinical trials have demonstrated the success of immunomodulatory therapies for the treatment of cancer. Monoclonal antibodies can target components of the immune system to either i) agonise co-stimulatory molecules, such as CD137, OX40 and CD40; or ii) inhibit immune checkpoints, such as cytotoxic T-lymphocyte-associated antigen 4 (CTLA-4), programmed cell death-1 (PD-1) and its corresponding ligand PD-L1. Although tumour regression is the outcome for some patients following immunotherapy, many patients still do not respond. Furthermore, chemotherapy has been the standard of care for most cancers, but the immunomodulatory capacity of these drugs has only recently been uncovered. The ability of chemotherapy to modulate the immune system through a variety of mechanisms, including immunogenic cell death (ICD), increased antigen presentation and depletion of regulatory immune cells, highlights the potential for synergism between conventional chemotherapy and novel immunotherapy. In addition, recent pre-clinical trials indicate dipeptidyl peptidase (DPP) enzyme inhibition, an enzyme that can regulate immune cell trafficking to the tumour microenvironment, as a novel cancer therapy. The present review focuses on the current immunological approaches for the treatment of cancer, and summarizes clinical trials in the field of immunotherapy as a single treatment and in combination with chemotherapy.

Interleukin 6 (IL-6), a well-known pro-inflammatory cytokine with pleiotropic activity is a central player in chronic inflammatory diseases including cancers. Therefore, blockade of the IL-6 signalling pathway has become a target for the therapy of diverse cancers such as multicentric Castleman's disease (CD), multiple myeloma and solid tumours including renal, prostate, lung, colorectal and ovarian cancers. Monoclonal antibodies against IL-6 (Siltuximab) and the IL-6 receptor (IL-6R) (Tocilizumab) have emerged as potential immunotherapies, alone or in combination with conventional chemotherapy. Human trials have demonstrated the ability to block IL-6 activity and in multicentric CD lead to durable clinical response and longer disease stabilisation. However, the efficacy of these treatments is still debatable for other cancers. New generation therapeutics in development such as Clazakizumab, Sarilumab, and soluble gp130-Fc have the additional features of improved binding affinity, better specificity with reduced adverse effects. A deeper understanding of the immunological basis of these agents, as well as of the challenges that are faced by immunotherapy-based products in clinical trials, will help select the most promising anti-IL-6/IL-6R therapies for large scale use. Concurrently, current research efforts to personalize treatments may help in the treatment of patients that would greatly benefit from IL-6 blocking therapies.