Special Issue: Natural Products: Anticancer and Beyond

A review of tanshinone compounds in prostate cancer treatment

Prostate cancer (PCa) is one of the most common malignant epithelial tumors in men worldwide. PCa patients are initially sensitive to chemotherapy, but patients in the advanced stages of PCa eventually develop resistance, leaving them with limited therapeutic options. Therefore, it is very important to screen new drugs for treating PCa. Salvia miltiorrhiza is a common Chinese herbal medicine used in some Asian countries. It has many functions and is widely used to treat a variety of diseases, including heart diseases and cancers. For the past few years, research has shown that liposoluble constituents of tanshinones (TANs), including cryptotanshinone, TAN IIA, dihydrotanshinone I, and TAN I, exhibit good anticancer activity in PCa. In this study, we review the progress of TAN compounds (cryptotanshinone, TAN IIA, dihydrotanshinone I, and TAN I) in treating PCa over the past decade. These compounds can act on the same molecular mechanisms, as they have a very similar structure; they are also found to work slightly differently in PCa. According to current studies, compared with other TAN compounds, TAN IIA appears to hold more potential for treating PCa. The toxicity, side effects or biodistribution of Salvia miltiorrhiza and these four TANs need to be confirmed with further research. Findings obtained in this study may provide important information for the potential clinical application of cryptotanshinone, TAN IIA, dihydrotanshinone I, and TAN I in the treatment of PCa.

Exploring the potential of Ziziphus nummularia and luteolin-7-O-glucoside as tubulin inhibitors in cancer therapy and survival

Cancer is responsible for approximately 10 million deaths worldwide, with 70% of the deaths occurring in low- and middle-income countries; as such safer and more effective anti-cancer drugs are required. Therefore, the potential benefits of Ziziphus nummularia and Ziziphus spina-christi as sources of anti-cancer agents were investigated. Z. nummularia and Z. spina-christi extracts were prepared using chloroform, ethanol, ethyl acetate, and water. The extracts' anti-cancer properties were determined using the MTT Cell Viability Assay in four cancer cell lines: breast (KAIMRC2 and MDA-MB-231), colorectal (HCT8), and liver (HepG2). The ApoTox-Glo Triplex Assay and high-content imaging (HCI)-Apoptosis Assay were used to assess KAIMRC2 and HCT8 cells further. In addition, KAIMRC2 cells were tested for microtubule staining, and AKT/mTOR protein expression was determined by western blot analysis. Liquid chromatography-mass spectrometry (LC-MS) was performed to identify the secondary metabolites in the ethanol and ethyl acetate extracts, followed by in silico techniques to predict molecular targets and interactions, safety, and pharmacokinetic profile for identified metabolites. Out of the eight extracts, the ethanolic extract of Z. nummularia, exhibited the most potent activity against KAIMRC2 cells with an IC50 value of 29.2 μg/ml. Cancer cell treatment with the ethanolic extract of Z. nummularia resulted in a dose-dependent decrease in cell viability with increased apoptosis and cytotoxic effects. Microtubule staining showed a disrupted microtubular network. The ethanolic extract treatment of KAIMRC2 cells led to upregulated expression of pAKT and pmTOR. In silico studies predicted luteolin-7-O-glucoside to be a ligand for tubulin with the highest docking score (- 7.686) and similar binding interactions relative to the native ligand. Further computational analysis of the metabolites showed acceptable pharmacokinetic and safety profiles, although ethanolic extract metabolites were predicted to have cardiotoxic effects. Ethanolic extraction is optimal for solubilizing active anticancer metabolites from Z. nummularia, which may act by causing M-phase arrest via inhibition of tubulin polymerization. Luteolin-7-O-glucoside is the lead candidate for further research and development as an anti-cancer agent. In addition, this study suggests that herbal treatment could switch on mechanisms of adaptation and survival in cancer cells.

Engineering natural molecule-triggered genetic control systems for tunable gene- and cell-based therapies

The ability to precisely control activities of engineered designer cells provides a novel strategy for modern precision medicine. Dynamically adjustable gene- and cell-based precision therapies are recognized as next generation medicines. However, the translation of these controllable therapeutics into clinical practice is severely hampered by the lack of safe and highly specific genetic switches controlled by triggers that are nontoxic and side-effect free. Recently, natural products derived from plants have been extensively explored as trigger molecules to control genetic switches and synthetic gene networks for multiple applications. These controlled genetic switches could be further introduced into mammalian cells to obtain synthetic designer cells for adjustable and fine tunable cell-based precision therapy. In this review, we introduce various available natural molecules that were engineered to control genetic switches for controllable transgene expression, complex logic computation, and therapeutic drug delivery to achieve precision therapy. We also discuss current challenges and prospects in translating these natural molecule-controlled genetic switches developed for biomedical applications from the laboratory to the clinic.

Research Status of Mouse Models for Non-Small-Cell Lung Cancer (NSCLC) and Antitumor Therapy of Traditional Chinese Medicine (TCM) in Mouse Models

Non-small-cell lung cancer (NSCLC) is known as one of the most lethal cancers, causing more than 1 million deaths annually worldwide. Therefore, the development of novel therapeutic drugs for NSCLC has become an urgent need. Herein, various mouse models provide great convenience not only for researchers but also for the development of antitumor drug. Meanwhile, TCM, as a valuable and largely untapped resource pool for modern medicine, provides research resources for the treatment of various diseases. Until now, cell-derived xenograft (CDX) model, patient-derived xenograft (PDX) model, syngeneic model, orthotopic model, humanized mouse model (HIS), and genetically engineered mouse models (GEMMs) have been reported in TCM evaluation. This review shows the role and current status of kinds of mouse models in antitumor research and summarizes the application progress of TCM including extracts, formulas, and isolated single molecules for NSCLC therapy in various mouse models; more importantly, it provides a theoretical exploration of what kind of mouse models is ideal for TCM efficacy evaluation in future. However, there are still huge challenges and limitations in the development of mouse models specifically for the TCM research, and none of the available models are perfectly matching the characteristics of TCM, which suppress the tumor growth through various mechanisms, especially by regulating immune function. Nevertheless, with fully functional immune system existing in syngeneic model and humanized mouse model (HIS), it is still suggested that these two models are more suitable for development of TCM especially for TCM extracts or formulas. Moreover, continued efforts are needed to generate more reliable mouse models to test TCM formulas in future research.

A Mini-Review of Flavone Isomers Apigenin and Genistein in Prostate Cancer Treatment

The initial responses to standard chemotherapies among prostate cancer (PCa) patients are usually significant, while most of them will finally develop drug resistance, rendering them with limited therapies. To discover new regimens for the treatment of PCa including resistant PCa, natural products, the richest source of bioactive compounds, can serve as a library for screening and identifying promising candidates, and flavones such as apigenin and genistein have been used in lab and clinical trials for treating PCa over decades. In this mini-review, we take a look into the progress of apigenin and genistein, which are isomers, in treating PCa in the past decade. While possessing very similar structure, these two isomers can both target the same signaling pathways; they also are found to work differently in PCa cells. Given that more combinations are being developed and tested, genistein appears to be the more promising option to be approved. The anticancer efficacies of these two flavones can be confirmed by in-vitro and in-vivo studies, and their applications remain to be validated in clinical trials. Information gained in this work may provide important information for new drug development and the potential application of apigenin and genistein in treating PCa.

Construction and Screening of Fractional Library of Salviae Miltiorrhizae Radix et Rhizoma for the Rapid Identification of Active Compounds against Prostate Cancer

Efficient screening of anticancer agents is in urgent need to develop new drugs that combat malignant tumors and drug resistance. In this study, a combined strategy composed by solvent partition and HPLC fractionation was developed to generate an herbal fraction library of Salviae Miltiorrhizae Radix et Rhizoma to quickly and efficiently screen anticancer agents. All library entries are directed into 96 well plates which are well mapped with HPLC chromatograms. The cell proliferation assay revealed seven active subfractions. Then, the major active ten peaks in these subfractions were prepared and isolated by semipreparative HPLC, and their inhibitory activities against prostate cancer cells were then tested at the same concentration level, leading to the identification of several active compounds. In addition, the structures of compounds arucadiol (2), 15,16-dihydrotanshinone I (4), methyl tanshinonate (5), cryptanshinone (7), 1,2-dihydrotanshinquinone I (9), and tanshinone IIA (10) were characterized by mass spectrometry and X-ray crystallographic analysis, and they were confirmed to be active in suppressing prostate cancer cell proliferation at 7.5 or 15 μg/mL, among which, the minor compounds 2, 4, and 5 showed higher activities than 9 and 10. This study provided a rapid strategy of identifying new anticancer agents in Salviae Miltiorrhizae Radix et Rhizoma, which can be applied in other herbal medicines.

Local Anesthetic Ropivacaine Exhibits Therapeutic Effects in Cancers

Despite the significant progress in cancer treatment, new anticancer therapeutics drugs with new structures and/or mechanisms are still in urgent need to tackle many key challenges. Drug repurposing is a feasible strategy in discovering new drugs among the approved drugs by defining new indications. Recently, ropivacaine, a local anesthetic that has been applied in clinical practice for several decades, has been found to possess inhibitory activity and sensitizing effects when combined with conventional chemotherapeutics toward cancer cells. While its full applications and the exact targets remain to be revealed, it has been indicated that its anticancer potency was mediated by multiple mechanisms, such as modulating sodium channel, inducing mitochondria-associated apoptosis, cell cycle arrest, inhibiting autophagy, and/or regulating other key players in cancer cells, which can be termed as multi-targets/functions that require more in-depth studies. In this review, we attempted to summarize the research past decade of using ropivacaine in suppressing cancer growth and sensitizing anticancer drugs both in-vitro and in-vivo, and tried to interpret the underlying action modes. The information gained in these findings may inspire multidisciplinary efforts to develop/discover more novel anticancer agents via drug repurposing.

Navigating Calcium and Reactive Oxygen Species by Natural Flavones for the Treatment of Heart Failure

Heart failure (HF), the leading cause of death among men and women world-wide, causes great health and economic burdens. HF can be triggered by many factors, such as coronary artery disease, heart attack, cardiomyopathy, hypertension, obesity, etc., all of which have close relations with calcium signal and the level of reactive oxygen species (ROS). Calcium is an essential second messenger in signaling pathways, playing a pivotal role in regulating the life and death of cardiomyocytes via the calcium-apoptosis link mediated by the cellular level of calcium. Meanwhile, calcium can also control the rate of energy production in mitochondria that are the major resources of ROS whose overproduction can lead to cell death. More importantly, there are bidirectional interactions between calcium and ROS, and such interactions may have therapeutic implications in treating HF through finely tuning the balance between these two by certain drugs. Many naturally derived products, e.g., flavones and isoflavones, have been shown to possess activities in regulating calcium and ROS simultaneously, thereby leading to a balanced microenvironment in heart tissues to exert therapeutic efficacies in HF. In this mini review, we aimed to provide an updated knowledge of the interplay between calcium and ROS in the development of HF. In addition, we summarized the recent studies (in vitro, in vivo and in clinical trials) using natural isolated flavones and isoflavones in treating HF. Critical challenges are also discussed. The information collected may help to evoke multidisciplinary efforts in developing novel agents for the potential prevention and treatment of HF.

Calunduloside E inhibits HepG2 cell proliferation and migration via p38/JNK-HMGB1 signalling axis

High-mobility group box 1 (HMGB1), a highly conserved chromosome protein, is considered as a potential therapeutic target and novel biomarker because of its regulation in the proliferation and metastasis of Hepatocellular carcinoma (HCC). Calenduloside E (CE), a natural active product, has been reported to anti-cancer effect. However, the role and underlying molecular mechanism of CE in HCC is still unclear. The purpose of this study is to investigate the effects of CE on the proliferation and migration of HCC, and then explore the possible underlying molecular mechanism. HepG2 cells were treated with CE or transfected with HMGB1 shRNA plasmids, EdU and colony formation assays were used to detect cell proliferation ability. Wound healing and transwell assays were used to determine the role of CE in cell migration. The expression of Cyclins, PCNA, MMPs, HMGB1, N-cadherin, E-cadherin and phosphorylation of p38, ERK and JNK were all detected using Western blotting. Our results showed that CE inhibited HepG2 cells proliferation and migration in a dose dependent manner; reduced the expression levels of Cycins, PCNA, HMGB1, MMPs and N-cadherin; up-regulated E-cadherin expression; enhanced the phosphorylation of p38 and JNK signalling pathways. Blocking the activation of p38 and JNK obviously reversed CE-mediated inhibitory effects on HepG2 cell proliferation and migration; reversed CE-induced down-regulation of Cyclins, PCNA, MMPs, N-cadherin and HMGB1, as well as E-cadherin up-regulation. In conclusion, our study suggested that CE reduces the expression levels of Cyclins, MMPs and epithelial-mesenchymal transformation (EMT) through p38/JNK-HMGB1 signaling axis and then inhibits HepG2 cells proliferation and migration in HepG2 cells. This study provides a new perspective for the anti-tumour molecular mechanism of CE in HCC.

A comprehensive review of anticancer mechanisms of action of Alantolactone

Cancer is considered as the main challenge of human communities, and it annually imposes a significant economic burden on society. Natural products have been used for treatment of many diseases including inflammation, infections, neurological disorders, atherosclerosis, asthma and cancer for many years. Sesquiterpene lactones (STLs) refers to a group of natural products with different biological activities. A type of STL that has recently attracted much attention is Alantolactone (ALT). In recent years, many studies have investigated the molecular mechanism of this compound affecting cancer cells and results suggest that this compound exerts its anticancer effects by providing free radicals and inhibiting some of the signaling pathways that are effective in progression of cancer cells. The present study is aimed to introduce the latest molecular mechanisms of ALT proposed by researchers in recent years.

Effect of naringenin and its combination with cisplatin in cell death, proliferation and invasion of cervical cancer spheroids

The main treatment alternative for cervical cancer is cisplatin chemotherapy. However, the resistance of tumor cells to cisplatin, in addition to side effects, limits its use. The flavonoid naringenin has shown cytotoxic effects on tumor cells and may be considered as a coadjuvant in the treatment of cervical cancer. In the present study, the effect of naringenin on cell viability, cytotoxicity, proliferation, apoptosis and invasion was evaluated in HeLa spheroid cultures. Naringenin impaired the cell viability as indicated by low ATP levels and caused concentration- and time-dependent cytotoxicity via the loss of cell membrane integrity. Furthermore, it did not activate caspases 3, 7, 8, and 9, suggesting that the cytotoxic effect was by necrotic cell death instead of apoptosis. Additionally, proliferation in the G0/G1 phase of the cell cycle was inhibited. Cell invasion also decreased as time progressed. Later, we determined if naringenin could improve the anti-tumor effect of cisplatin. The combination of naringenin with low concentrations of cisplatin improved the effect of the drug by significantly decreasing cell viability, potentiating the induction of cytotoxicity and decreasing the invasive capacity of the spheroids. Since these effects are regulated by some key proteins, molecular docking results indicated the interaction of naringenin with RIP3 and MLKL, cyclin B and with matrix metalloproteases 2 and 9. The results showed the anti-tumor effect of naringenin on the HeLa spheroids and improved effect of the cisplatin at low concentrations in combination with naringenin, placing flavonoids as a potential adjuvant in the therapy against cervical cancer.

Terpenes with Antitumor Activity: A Patent Review

BACKGROUND

Cancer is a major public health concern, and is one of the leading causes of death globally. Surgical removal, chemotherapy or hormonal therapy, radiation therapy, or a combination of them are treatment for cancer, many of which are ineffective or have serious side effects. In view of this, there is a search for new, more effective alternatives for cancer prevention and treatment. One possible source of compounds are natural products; among them, terpenes, a large class of organic compounds, have shown promise due to their anti-inflammatory, anti-tumorigenic, and hypolipidemic properties, among others recorded in the literature.

OBJECTIVE

The study aims to use a patent review to evaluate the development and use of terpenes, or formulations containing terpenes, in new therapeutic options for the treatment of various types of cancer.

METHODS

This patent review was carried out using the specialized patent databases of WIPO and Espacenet. The selection of patents was based on the following inclusion criteria which included pre-clinical and/or clinical trials, and demonstrated anti-tumor effects.

RESULTS

Eight patents were identified, six from China, and two from Japan. In this review, all patents confirmed having good antitumor activity for many types of cancer cells. In addition, the inventors indicate more studies pre-clinical and clinical trials giving greater clarity and accurate reflection of the activity of the products studied.

CONCLUSION

Natural products are an important source of compounds for use in the fight against cancer that can act synergistically, and help in the treatment of cancer.

Repositioning Lidocaine as an Anticancer Drug: The Role Beyond Anesthesia

While cancer treatment has improved dramatically, it has also encountered many critical challenges, such as disease recurrence, metastasis, and drug resistance, making new drugs with novel mechanisms an urgent clinical need. The term “drug repositioning,” also known as old drugs for new uses, has emerged as one practical strategy to develop new anticancer drugs. Anesthetics have been widely used in surgical procedures to reduce the excruciating pain. Lidocaine, one of the most-used local anesthetics in clinical settings, has been found to show multi-activities, including potential in cancer treatment. Growing evidence shows that lidocaine may not only work as a chemosensitizer that sensitizes other conventional chemotherapeutics to certain resistant cancer cells, but also could suppress cancer cells growth by single use at different doses or concentrations. Lidocaine could suppress cancer cell growth in vitro and in vivo via multiple mechanisms, such as regulating epigenetic changes and promoting pro-apoptosis pathways, as well as regulating ABC transporters, metastasis, and angiogenesis, etc., providing valuable information for its further application in cancer treatment and for new drug discovery. In addition, lidocaine is now under clinical trials to treat certain types of cancer. In the current review, we summarize the research and analyze the underlying mechanisms, and address key issues in this area.

Inhibitory Effects of Ginsenoside Ro on the Growth of B16F10 Melanoma via Its Metabolites

Ginsenoside Ro (Ro), a major saponin derived and isolated from Panax ginseng C.A. Meyer, exerts multiple biological activities. However, the anti-tumour efficacy of Ro remains unclear because of its poor in vitro effects. In this study, we confirmed that Ro has no anti-tumour activity in vitro. We explored the anti-tumour activity of Ro in vivo in B16F10 tumour-bearing mice. The results revealed that Ro considerably suppressed tumour growth with no significant side effects on immune organs and body weight. Zingibroside R1, chikusetsusaponin IVa, and calenduloside E, three metabolites of Ro, were detected in the plasma of Ro-treated tumour-bearing mice and showed excellent anti-tumour effects as well as anti-angiogenic activity. The results suggest that the metabolites play important roles in the anti-tumour efficacy of Ro in vivo. Additionally, the haemolysis test demonstrated that Ro has good biocompatibility. Taken together, the findings of this study demonstrate that Ro markedly suppresses the tumour growth of B16F10-transplanted tumours in vivo, and its anti-tumour effects are based on the biological activity of its metabolites. The anti-tumour efficacy of these metabolites is due, at least in part, to its anti-angiogenic activity.

Reversal of Multidrug Resistance in Cancer by Multi-Functional Flavonoids

Multidrug resistance (MDR) resulting from different defensive mechanisms in cancer is one of the major obstacles of clinical treatment. To circumvent MDR many reversal agents have been developed, but most of them fail in clinical trials due to severely adverse effects. Recently, certain natural products have been reported to overcome MDR, including flavonoids which are abundant in plants, foods, and herbs. The structure of flavonoids can be abbreviated as C6-C3-C6 (C for carbon), and further categorized into flavonoids, iso-flavonoids and neo-flavonoids, according to their structural backbones. Flavonoids possess multiple bioactivities, and a growing body of research has indicated that both flavonoids and iso-flavonoids can either kill or re-sensitize conventional chemotherapeutics to resistant cancer cells. Here, we summarize the research and discuss the underlying mechanisms, concluding that these flavonoids do not function as specific regulators of target proteins, but rather as multi-functional agents that negatively regulate the key factors contributing to MDR.

Stimulatory effects of platycodin D on osteoblast differentiation

Previous studies have suggested that platycodin D is implicated in bone biology and ameliorates osteoporosis development. Platycodin D repressed the osteoclast activity and enhanced bone mineral density in the mouse model. However, the effects of platycodin D on osteoblast differentiation have not been elucidated yet. In C3H10T1/2 cells, platycodin D upregulated osteogenic markers including alkaline phosphatase (ALP), bone sialoprotein, and collagen type 1 alpha 1, and transcription factors, such as Runx2 and osterix, subsequently enhancing the bone mineralization. In a molecular mechanism study, platycodin D induced β-catenin nuclear accumulation by upregulating GSK3β phosphorylation. Furthermore, platycodin D upregulated the ALP activity and enhanced the mineralization process in osteoblast cells via the sirtuin 1/β-catenin pathways. Taken together, these results suggested that platycodin D could be an effective therapeutic compound against osteoporosis because of its regulatory effects during the osteoblast differentiation.