Mechanism of inhibition of tumor angiogenesis by beta-hydroxyisovalerylshikonin

Updated progression of honokiol in lung cancer treatment

OBJECTIVES

Despite significant advancements in innovative therapy, lung cancer continues to have an unexpectedly low 5-year survival rate. This necessitates the urgent development of novel and effective therapies. One such potential therapy is Honokiol (HNK, C18H18O2), a biphenolic natural compound isolated from the leaves and bark of Magnolia plant species. The objective of this review is to examine the various studies supporting the anti-lung cancer effects of HNK and its potential use in the treatment of lung cancer.

KEY FINDINGS

Emerging research has shown that HNK possesses a range of pharmacological characteristics that make it a promising agent in the fight against lung cancer. Specifically, HNK has been found to regulate various molecular targets, including the activation of pro-apoptotic factors and the suppression of anti-apoptotic proteins and different transcription factors. It also downregulates various enzymes, chemokines, cell surface adhesion molecules, and cell cycle proteins. Additionally, HNK inhibits the activity of protein tyrosine kinases and serine/threonine kinases. These effects contribute to its ability to efficiently prevent the progression of lung cancer, either solely or in combination with other therapeutic strategies. Furthermore, several nanotechnologies have been employed to modify HNK for the treatment of lung cancer, enhancing its potential efficacy.

SUMMARY

In summary, Honokiol (HNK) is a biphenolic natural compound with significant anti-lung cancer properties. Its pharmacological characteristics, including the regulation of various molecular targets and the inhibition of key enzymes and kinases, make it a promising agent for the treatment of lung cancer. Emerging research supports its ability to prevent the progression of lung cancer, either alone or in combination with other therapies. Additionally, nanotechnologies have been used to modify HNK, potentially enhancing its efficacy in the treatment of lung cancer. This review highlights the various studies documenting the anti-lung cancer effects of HNK, underscoring its potential as a novel and effective therapy for this deadly disease.

Beta-Hydroxyisovaleryl-Shikonin Eradicates Epithelial Cell Adhesion Molecule-Positive Liver Cancer Stem Cells by Suppressing dUTP Pyrophosphatase Expression

Cancer stem cells (CSCs) play an essential role in tumorigenesis, chemoresistance, and metastasis. Previously, we demonstrated that the development of hepatocellular carcinoma (HCC) is dictated by a subset of epithelial cell adhesion molecule-positive (EpCAM+) liver CSCs with the activation of Wnt signaling. In this study, we evaluated the expression of dUTP pyrophosphatase (dUTPase), which plays a central role in the development of chemoresistance to 5-fluorouracil, in EpCAM+ HCC cells. We further evaluated the effect of beta-hydroxyisovaleryl-shikonin (β-HIVS), an ATP-noncompetitive inhibitor of protein tyrosine kinases, on HCC CSCs. EpCAM and dUTPase were expressed in hepatoblasts in human fetal liver, hepatic progenitors in adult cirrhotic liver, and a subset of HCC cells. Sorted EpCAM+ CSCs from HCC cell lines showed abundant nuclear accumulation of dUTPase compared with EpCAM-negative cells. Furthermore, treatment with the Wnt signaling activator BIO increased EpCAM and dUTPase expression. In contrast, β-HIVS treatment decreased dUTPase expression. β-HIVS treatment decreased the population of EpCAM+ liver CSCs in a dose-dependent manner in vitro and suppressed tumor growth in vivo compared with the control vehicle. Taken together, our data suggest that dUTPase could be a good target to eradicate liver CSCs resistant to 5-fluorouracil. β-HIVS is a small molecule that could decrease dUTPase expression and target EpCAM+ liver CSCs.

β-Hydroxyisovaleryl-Shikonin Exerts an Antitumor Effect on Pancreatic Cancer Through the PI3K/AKT Signaling Pathway

Pancreatic cancer (PC) is marked with a low survival rate and lack of recognized effective treatment strategy. We investigated the antitumor effect of β-hydroxyisovaleryl-shikonin (β-HIVS) on PC and the associated working mechanism. Cell toxicity was determined using Cell Counting Kit-8 (CCK-8) assay. Acridine Orange/Ethidium Bromide (AO/EB) double-fluorescent staining assay accompanied by flow cytometry was utilized to estimate cell apoptosis. Cell cycle, reactive oxygen species (ROS), and mitochondrial membrane potential were all evaluated using flow cytometry. Transwell and wound healing assays were performed to evaluate cell migration and invasion. Protein expression was analyzed by Western blots. A xenograft mouse model was employed to determine the antitumor effect of β-HIVS in vivo. PC cell viability gradually decreased with increasing β-HIVS while apoptosis was enhanced together with cell-cycle blockage in the G0–G1 phases. β-HIVS induced mitochondrial dysfunction, ROS production, and DNA damage and inhibited the invasive and migratory ability of PC cells. We further confirmed the suppression of EMT and PI3K/AKT pathways as underlying mechanisms. The mouse model treated with the increasing dose of β-HIVS displayed decreased tumor growth rate, along with increased apoptosis. Thus, β-HIVS exerts antitumor effects on PC through inducing apoptosis, ROS production, decreasing mitochondrial membrane potential, and suppressing signal pathways, such as PI3K/AKT. In summary, β-HIVS might be a promising strategy for PC treatment.

Molecular mechanism of shikonin inhibiting tumor growth and potential application in cancer treatment

Shikonin is one of the major bioactive components of Lithospermum erythrorhizon. It has a good killing effect in a variety of tumor cells. Its antitumor effect involves multiple targets and pathways and has received extensive attention and study in recent years. In this review, we systematically review recent progress in determining the antitumor mechanism of shikonin and its derivatives, specifically their induction of reactive oxygen species production, inhibition of EGFR and PI3K/AKT signaling pathway activation, inhibition of angiogenesis and induction of apoptosis and necroptosis. We also discuss the application of nanoparticles loaded with shikonin in the targeted therapy of various cancers. Finally, we suggest new strategies for the clinical application of shikonin and its derivatives.

Shikonin alleviates choroidal neovascularization by inhibiting proangiogenic factor production from infiltrating macrophages

Choroidal neovascularization (CNV), a feature of neovasular age-related macular degeneration (AMD), acts as a leading cause of vision loss in the elderly. Shikonin (SHI), a natural bioactive compound extracted from Chinese herb radix arnebiae, exerts anti-inflammatory and anti-angiogenic roles and also acts as a potential pyruvate kinase M2 (PKM2) inhibitor in macrophages. The major immune cells macrophages infiltrate the CNV lesions, where the production of pro-angiognic cytokines from macrophage facilitates the development of CNV. PKM2 contributes to the neovascular diseases. In this study, we found that SHI oral gavage alleviated the leakage, area and volume of mouse laser-induced CNV lesion and inhibited macrophage infiltration without ocular cytotoxicity. Moreover, SHI inhibited the secretion of pro-angiogenic cytokine, including basic fibroblast growth factor (FGF2), insulin-like growth factor-1 (IGF1), chemokine (C-C motif) ligand 2 (CCL2), placental growth factor and vascular endothelial growth factor (VEGF), from primary human macrophages by down-regulating PKM2/STAT3/CD163 pathway, indicating a novel potential therapy strategy for CNV.

Shikonin induces odontoblastic differentiation of dental pulp stem cells via AKT-mTOR signaling in the presence of CD44

Purpose: In our previous study, we demonstrated that hyaluronan induces odontoblastic differentiation of dental pulp stem cells via interactions with CD44. However, it remains unclear whether CD44 expression by dental pulp stem cells is required for odontoblastic differentiation.Methods: We searched for a compound other than hyaluronan that induces odontoblastic differentiation of dental pulp stem cells and used western blotting to determine whether CD44 is involved in the induction of odontoblastic differentiation by the compound. We further validated the cell signaling details of the compound-induced expression of dentin sialophosphoprotein (DSPP), which is known as a marker of odontoblastic differentiation.Results: We investigated shikonin, which is one of the derivatives of naphthoquinone, the skeleton of vitamin K. Shikonin-induced expression of DSPP was inhibited by PI3K, AKT, and mTOR inhibitors. Additionally, shikonin-induced expression of DSPP was inhibited in dental pulp stem cells transfected with siRNA against CD44.Conclusions: Shikonin can stimulate dental pulp stem cells to undergo odontoblastic differentiation through a mechanism involving the AKT-mTOR signaling pathway and CD44. Although expression of CD44 is important for inducing odontoblastic differentiation of dental pulp stem cells, the relationship between the AKT-mTOR signaling pathway and CD44 expression, in the context of shikonin stimulation, has not yet been elucidated. This study suggests that shikonin may be useful for inducing odontoblastic differentiation of dental pulp stem cells, and that it may have clinical applications, including protection of the dental pulp.

Natural Products with Activity against Lung Cancer: A Review Focusing on the Tumor Microenvironment

Lung cancer is one of the most prevalent malignancies worldwide. Despite the undeniable progress in lung cancer research made over the past decade, it is still the leading cause of cancer-related deaths and continues to challenge scientists and researchers engaged in searching for therapeutics and drugs. The tumor microenvironment (TME) is recognized as one of the major hallmarks of epithelial cancers, including the majority of lung cancers, and is associated with tumorigenesis, progression, invasion, and metastasis. Targeting of the TME has received increasing attention in recent years. Natural products have historically made substantial contributions to pharmacotherapy, especially for cancer. In this review, we emphasize the role of the TME and summarize the experimental proof demonstrating the antitumor effects and underlying mechanisms of natural products that target the TME. We also review the effects of natural products used in combination with anticancer agents. Moreover, we highlight nanotechnology and other materials used to enhance the effects of natural products. Overall, our hope is that this review of these natural products will encourage more thoughts and ideas on therapeutic development to benefit lung cancer patients.

β-Hydroxyisovalerylshikonin inhibits IL-1β-induced chondrocyte inflammation via Nrf2 and retards osteoarthritis in mice

Osteoarthritis is a chronic degenerative disease characterized by cartilage destruction. It is the fourth most disabling disease worldwide and is currently incurable. Inflammation and extracellular matrix (ECM) degradation are considered to be substantial reasons for accelerating the progression of OA. β-Hydroxyisoamylshikonin (β-HIVS) is a natural naphthoquinone compound with anti-inflammatory and antioxidant activity. However, the effect of β-HIVS on OA is still unclear. In this study, we found that β-HIVS can down-regulate the expression of NO, PEG2, IL-6, TNF-α, COX-2, and iNOS, suggesting its anti-inflammatory effects in chondrocytes; we also found that β-HIVS may down-regulate the expression of ADAMTS5 and MMP13 and up-regulate the expression of aggrecan and collagen II to inhibit the degradation of ECM. Mechanistically, β-HIVS inhibited the NFκB pathway by activating the Nrf2/HO-1 axis, thereby exerting its anti-inflammatory and inhibitory effects on ECM degradation. In vivo experiments also proved the therapeutic effects of β-HIVS on OA in mice, and Nrf2 is the target of β-HIVS. These findings indicate that β-HIVS may become a new drug for the treatment of OA.

Endothelial Cell Glucose Metabolism and Angiogenesis

Angiogenesis, a process of new blood vessel formation from the pre-existing vascular bed, is a critical event in various physiological and pathological settings. Over the last few years, the role of endothelial cell (EC) metabolism in angiogenesis has received considerable attention. Accumulating studies suggest that ECs rely on aerobic glycolysis, rather than the oxidative phosphorylation pathway, to produce ATP during angiogenesis. To date, numerous critical regulators of glucose metabolism, fatty acid oxidation, and glutamine metabolism have been identified to modulate the EC angiogenic switch and pathological angiogenesis. The unique glycolytic feature of ECs is critical for cell proliferation, migration, and responses to environmental changes. In this review, we provide an overview of recent EC glucose metabolism studies, particularly glycolysis, in quiescent and angiogenic ECs. We also summarize and discuss potential therapeutic strategies that take advantage of EC metabolism. The elucidation of metabolic regulation and the precise underlying mechanisms could facilitate drug development targeting EC metabolism to treat angiogenesis-related diseases.

Molecular simulation studies to reveal the binding mechanisms of shikonin derivatives inhibiting VEGFR-2 kinase

Traditional vascular endothelial growth factor receptor 2 (VEGFR-2) inhibitors can manage angiogenesis; however, severe toxicity and resistance limit their long-term applications in clinical therapy. Shikonin (SHK) and its derivatives could be promising to inhibit the VEGFR-2 mediated angiogenesis, as they are reported to bind in the catalytic kinase domain with low affinity. However, the detailed molecular insights and binding dynamics of these natural inhibitors are unknown, which is crucial for potential SHK based lead design. Therefore, the present study employed molecular modeling and simulations techniques to get insight into the binding behaviors of SHK and its two derivates, β-hydroxyisovalerylshikonin (β-HIVS) and acetylshikonin (ACS). Here the intermolecular interactions between protein and ligands were studied by induced fit docking approach, which were further evaluated by treating QM/MM (quantum mechanics/molecular mechanics) and molecular dynamics (MD) simulation. The result showed that the naphthazarin ring of the SHK derivates is vital for strong binding to the catalytic domain; however, the binding stability can be modulated by the side chain modification. Because of having electrostatic potential, this ring makes essential interactions with the DFG (Asp1046 and Phe1047) motif and also allows interacting with the allosteric binding site. Taken together, the studies will advance our knowledge and scope for the development of new selective VEGFR-2 inhibitors based on SHK and its analogs.

Anti-angiogenic effect of Shikonin in rheumatoid arthritis by downregulating PI3K/AKT and MAPKs signaling pathways

ETHNOPHARMACOLOGICAL RELEVANCE

Zicao is the dried root of Lithospermum erythrorhizon Sieb, et Zucc, Arnebia euchroma (Royle) Johnst, or Arnebia guttata Bunge and commonly used to treat viral infection, inflammation, arthritis and cancer in China.Shikonin (SKN) is a major active chemical component isolated from zicao. Previous research showed that SKN has anti-inflammatory, immunomodulatory and analgesic effects, and inhibits the development of arthritis and the condition of collagen arthritis (CIA) mice; nevertheless, its role in the angiogenesis of rheumatoid arthritis (RA) has not been elucidated.

AIM OF THE STUDY

The purpose of this study was to investigate the antiangiogenic activity of SKN in CIA rats and various angiogenesis models.

MATERIAL AND METHODS

The anti-arthritic effect of SKN on CIA rats was tested by arthritis score, arthritis incidence, radiological observation and histopathology evaluation of inflamed joints. Vessel density evaluated with CD31 immunohistochemistry/immunofluorescence in joint synovial membrane tissues of CIA rats, chick chorioallantoic membrane assay, rat aortic ring assay, and the migration, invasion, adhesion and tube formation of human umbilical vein endothelial (HUVEC) cells induced by tumor necrosis factor (TNF)-α were used to measured the antiangiogenenic activity of SKN. Moreover, the effect of SKN on the expression of angiogenic mediators, such as vascular endothelial growth factor (VEGF), VEGFR2, TNF-α, interleukin (IL)-1β, platelet derived growth factor (PDGF) and transforming growth factor (TGF)-β in sera and joint synovia of rats, and in TNF-α-induced MH7A/HUVEC cells were measured by immunohistochemistry, enzyme linked immunosorbent assay, Western blot and/or real-time polymerase chain reaction (PCR). Through the analysis of protein and mRNA levels of phosphoinositide 3-kinase (PI3K), Akt and PTEN, and the autophosphorylation of ERK1/2, JNK and p38 in joint synovia of rats and in TNF-α-induced HUVEC cells, the molecular mechanism of its inhibition was elucidated by using Western blot and/or real-time PCR.

RESULTS

SKN significantly reduced the arthritis score and arthritis incidence, and inhibited inflammation, pannus formation, cartilage and bone destruction of inflamed joints in CIA rats. Partially, SKN remarkably decreased the immature blood vessels in synovial membrane tissues of inflamed joints from CIA rats. It also suppressed in vivo angiogenesis in chick embryo and VEGF₁₆₅-induced microvessel sprout formation ex vivo. Meanwhile, SKN inhibited TNF-α-induced migration, invasion, adhesion and tube formation of HUVEC cells. Moreover, SKN significantly decreased the expression of angiogenic activators including VEGF, VEGFR2, TNF-α, IL-1β, PDGF and TGF-β in synovia of CIA rats and/or in MH7A/HUVEC cells. More interestingly, SKN downregulated PI3K and Akt, and simultaneously upregulated PTEN both at protein and mRNA levels in synovia tissues and/or in TNF-α-induced HUVEC cells. It also suppressed the phosphorylation and gene level of TNF-α-induced signaling molecules, as ERK1/2, JNK, and p38 in synovium and/or in TNF-α-induced HUVEC cells.

CONCLUSION

These findings indicate for the first time that SKN has the anti-angiogenic effect in RA in vivo, ex vivo and in vitro by interrupting the PI3K/AKT and MAPKs signaling pathways.

Activation of CaMKKβ-AMPK-mTOR pathway is required for autophagy induction by β,β-dimethylacrylshikonin against lung adenocarcinoma cells

β,β-Dimethylacrylshikonin (DMAS), an active ingredient of Lithospermum erythrorhizon and Arnebia euchroma, possess anti-neoplasm properties. Recently, DMAS was reported to stimulate autophagy in lung adenocarcinoma cells. However, the mechanisms by which DMAS modulates autophagy. have not yet been clearly elucidated. In this study, we found that DMAS significantly elevated intracellular free calcium accumulation. This activated the CaMKKβ-AMPK-mTOR pathway, subsequently inhibited mTOR and its substrate p70s6k and 4E-BP1, eventually leading to autophagy. In addition, we demonstrated that inhibition of autophagy by BAPTA-AM or STO-609 or compound C potently enhanced DMAS-induced lung adenocarcinoma cells apoptosis and growth inhibition. Overall, our results suggested that cytoprotective autophagy was triggered by DMAS via CaMKKβ-AMPK-mTOR signaling cascade in human lung adenocarcinoma cells, meaning that combining use of DMAS and autophagy inhibitors as a novel therapeutic option for lung adenocarcinoma will be very promising.

Shikonin derivatives for cancer prevention and therapy

Phytochemicals gained considerable interest during the past years as source to develop new treatment options for chemoprevention and cancer therapy. Motivated by the fact that a majority of established anticancer drugs are derived in one way or another from natural resources, we focused on shikonin, a naphthoquinone with high potentials to be further developed as preventive or therapeutic drug to fight cancer. Shikonin is the major chemical component of Lithospermum erythrorhizon (Purple Cromwell) roots. Traditionally, the root extract has been applied to cure dermatitis, burns, and wounds. Over the past three decades, the anti-inflammatory and anticancer effects of root extracts, isolated shikonin as well as semi-synthetic and synthetic derivatives and nanoformulations have been described. In vitro and in vivo experiments were conducted to understand the effect of shikonin at cellular and molecular levels. Preliminary clinical trials indicate the potential of shikonin for translation into clinical oncology. Shikonin exerts additive and synergistic interactions in combination with established chemotherapeutics, immunotherapeutic approaches, radiotherapy and other treatment modalities, which further underscores the potential of this phytochemical to be integrated into standard treatment regimens.

Beneficial Effects of Deoxyshikonin on Delayed Wound Healing in Diabetic Mice

Shiunko ointment is composed of five ingredients including Lithospermi Radix (LR), Angelicae Gigantis Radix, sesame seed oil, beeswax, and swine oil. It is externally applied as a treatment for a wide range of skin conditions such as eczema, psoriasis, hair loss, burns, topical wounds, and atopic dermatitis. Deoxyshikonin is the major angiogenic compound extracted from LR. In this study, we investigated the efficacy of LR extract and deoxyshikonin on impaired wound healing in streptozotocin (STZ)-induced diabetic mice. Treatment with LR extract elevated tube formation in human umbilical vein endothelial cells (HUVECs) and exerted antioxidant activity. An open skin wound was produced on the backs of diabetic mice and was then topically treated with deoxyshikonin or vehicle. In addition, deoxyshikonin promoted tube formation in high glucose conditions exposed to HUVECs, and which may be regulated by increased VEGFR2 expression and phosphorylation of Akt and p38. Our results demonstrate that deoxyshikonin application promoted wound repair in STZ-induced diabetic mice. Collectively, these data suggest that deoxyshikonin is an active ingredient of LR, thereby contributing to wound healing in patients with diabetes.

Shikonin sensitizes wild‑type EGFR NSCLC cells to erlotinib and gefitinib therapy

As patients with non-small cell lung cancer (NSCLC) and wild-type epidermal growth factor receptor (EGFR) are resistant to treatment with erlotinib or gefitinib, potential chemosensitizers are required to potentiate wild-type EGFR NSCLC cells to erlotinib/gefitinib treatment. The present study reported that shikonin could sensitize the anticancer activity of erlotinib/gefitinib in wild-type EGFR NSCLC cells. Furthermore, shikonin could potentiate mitochondrial-mediated apoptosis induced by erlotinib/gefitinib in wild-type EGFR NSCLC cells. In addition, the present study demonstrated that shikonin could induce apoptosis by activating reactive oxygen species (ROS)-mediated endoplasmic reticulum (ER) stress, and that erlotinib/gefitinib may also induce ER stress in wild-type EGFR NSCLC cells; however, shikonin plus erlotinib/gefitinib was more effective in activating ER stress than either agent alone. This indicated that ROS-mediated ER stress may be associated with enhanced mitochondrial apoptosis induced by shikonin plus erlotinib/gefitinib. In addition, shikonin may promote the transition of cytoprotective ER stress-inducing EGFR-tyrosine kinase inhibitor tolerance to apoptosis-promoting ER stress. Furthermore, shikonin may enhance the anti-NSCLC activity of erlotinib/gefitinib in vivo. The data of the present study indicated that shikonin may be a potential sensitizer to enhance the anti-cancer efficacy of erlotinib/gefitinib in wild-type EGFR NSCLC cells resistant to erlotinib/gefitinib treatment.

Metabolic profiling study of shikonin's cytotoxic activity in the Huh7 human hepatoma cell line

Shikonin and its enantiomer alkannin, which are natural products, have been extensively studied in vitro and in vivo for, among others, their antitumor activity. The investigation of the molecular pathways involved in their action is of interest, since they are not yet clearly defined. Metabolic profiling in cells can provide a picture of a cell's phenotype upon intervention, assisting in the elucidation of the mechanism of action. In this study, the cytotoxic effect of shikonin on a human hepatocarcinoma cell line was studied. Huh7 cells were treated with shikonin at 5 μM, and it was found that shikonin markedly inhibited cell growth. Metabolic profiling indicated alterations in the metabolic content of the cells and the culture media upon treatment, detecting the metabolic response of the cells. This study demonstrates the potential of metabolomics to improve knowledge on the mechanisms involved in shikonin's antitumor action.

Shikonin induces apoptosis of lung cancer cells via activation of FOXO3a/EGR1/SIRT1 signaling antagonized by p300

Shikonin derivatives exert powerful cytotoxic effects including induction of apoptosis. Here, we demonstrate the cytotoxic efficacy of shikonin in vivo in xenograft models, which did not affect body weight as well as its reduction of cell viability in vitro using several non-small cell lung cancer (NSCLC) cell lines. We found that inhibition of AKT by shikonin activated the forkhead box (FOX)O3a/early growth response protein (EGR)1 signaling cascade and enhanced the expression of the target gene Bim, leading to apoptosis in lung cancer cells. Overexpression of wild-type or a constitutively active mutant of FOXO3a enhanced shikonin-induced Bim expression. The NAD⁺-dependent histone deacetylase sirtuin (SIRT)1 amplified the pro-apoptotic effect by deacetylating FOXO3a, which induced EGR1 binding to the Bim promoter and activated Bim expression. Meanwhile, PI3K/AKT activity was enhanced, whereas that of FOXO3a was reduced and p300 was upregulated by treatment with a sublethal dose of shikonin. FOXO3a acetylation was enhanced by p300 overexpression, while shikonin-induced Bim expression was suppressed by p300 overexpression, which promoted cell survival. FOXO3a acetylation was increased by p300 overexpression and treatment with SIRT1 inhibitor, improving cell survival. In addition, shikonin-induced FOXO3a nuclear localization was blocked by AKT activation and SIRT1 inhibition, which blocked Bim expression and conferred resistance to the cytotoxic effects of shikonin. The EGR1 increase induced by shikonin was restored by pretreatment with SIRT1 inhibitor. These results suggest that shikonin induces apoptosis in some lung cancer cells via activation of FOXO3a/EGR1/SIRT1 signaling, and that AKT and p300 negatively regulate this process via Bim upregulation.

Pleiotropic effects of herbs characterized with blood-activating and stasis-resolving functions on angiogenesis

Accumulative evidences have underpinned the nature candidates from Chinese medicine (CM), particularly CM served as blood activating and stasis resolving (BASR, Huoxue Huayu in Chinese) by targeting tumor-associated angiogenesis. However, recent experiment research on the therapeutic angiogenesis by BASR-CM attracts wide attention and discussion. This opinion review focused on the underlying link between two indications and anticipated that (1) BASR-CM might emphasize on a balanced multi-cytokines network interaction; (2) BASR-CM might address on the nature of diseases prior to differently affecting physiological and pathological angiogenesis; (3) BASR-CM might mainly act on perivascular cells, either promotes arteriogenesis by increasing arteriogenic factors in ischemic diseases, or simultaneously keep a quiescent vasculature to impede angiogenesis in tumor context.

Biosynthesis and molecular actions of specialized 1,4-naphthoquinone natural products produced by horticultural plants

The 1,4-naphthoquinones (1,4-NQs) are a diverse group of natural products found in every kingdom of life. Plants, including many horticultural species, collectively synthesize hundreds of specialized 1,4-NQs with ecological roles in plant-plant (allelopathy), plant-insect and plant-microbe interactions. Numerous horticultural plants producing 1,4-NQs have also served as sources of traditional medicines for hundreds of years. As a result, horticultural species have been at the forefront of many basic studies conducted to understand the metabolism and function of specialized plant 1,4-NQs. Several 1,4-NQ natural products derived from horticultural plants have also emerged as promising scaffolds for developing new drugs. In this review, the current understanding of the core metabolic pathways leading to plant 1,4-NQs is provided with additional emphasis on downstream natural products originating from horticultural species. An overview on the biochemical mechanisms of action, both from an ecological and pharmacological perspective, of 1,4-NQs derived from horticultural plants is also provided. In addition, future directions for improving basic knowledge about plant 1,4-NQ metabolism are discussed.

β-hydroxyisovaleryl-shikonin induces human cervical cancer cell apoptosis via PI3K/AKT/mTOR signaling

The present study aimed to investigate the inhibitory ability of β-hydroxyisovaleryl-shikonin (β-HIVS) on the proliferation of human cervical cancer HeLa cells and to identify the mechanism of this effect. The HeLa cells were treated with β-HIVS and the inhibition of cell growth was detected by an MTT assay. Flow cytometry was performed to analyze the apoptosis rate and cell cycle distribution of HeLa cells. Reverse transcription-polymerase chain reaction and western blot analysis were used to examine the expression of the phosphatidylinositol 3-kinase (PI3K)/protein kinase B (AKT)/mammalian target of rapamycin (mTOR) signaling pathway proteins. The results revealed that β-HIVS inhibited HeLa cell proliferation in a dose- and time-dependent manner. With the administration of increasing concentrations of β-HIVS, the apoptotic rate of HeLa cells was also increased. The cell cycle was slightly arrested at the S phase, with ~6% of cells in this phase, subsequent to treatment with 10 µM β-HIVS. In addition, β-HIVS markedly reduced the expression levels of PI3K, AKT, mTOR and 70-kDa ribosomal protein S6 kinase in HeLa cells. β-HIVS promoted cervical cancer cell apoptosis by inhibiting the PI3K/AKT/mTOR signaling pathway and suppressing downstream gene expression. The present study is expected to lead to the development of molecular targeted therapy for this signaling pathway as a novel method of cervical cancer treatment.

Shikonin Suppresses Skin Carcinogenesis via Inhibiting Cell Proliferation

The M2 isoform of pyruvate kinase M2 (PKM2) has been shown to be up-regulated in human skin cancers. To test whether PKM2 may be a target for chemoprevention, shikonin, a natural product from the root of Lithospermum erythrorhizon and a specific inhibitor of PKM2, was used in a chemically-induced mouse skin carcinogenesis study. The results revealed that shikonin treatment suppressed skin tumor formation. Morphological examinations and immunohistochemical staining of the skin epidermal tissues suggested that shikonin inhibited cell proliferation without inducing apoptosis. Although shikonin alone suppressed PKM2 activity, it did not suppress tumor promoter-induced PKM2 activation in the skin epidermal tissues at the end of the skin carcinogenesis study. To reveal the potential chemopreventive mechanism of shikonin, an antibody microarray analysis was performed, and the results showed that the transcription factor ATF2 and its downstream target Cdk4 were up-regulated by chemical carcinogen treatment; whereas these up-regulations were suppressed by shikonin. In a promotable skin cell model, the nuclear levels of ATF2 were increased during tumor promotion, whereas this increase was inhibited by shikonin. Furthermore, knockdown of ATF2 decreased the expression levels of Cdk4 and Fra-1 (a key subunit of the activator protein 1. In summary, these results suggest that shikonin, rather than inhibiting PKM2 in vivo, suppresses the ATF2 pathway in skin carcinogenesis.

Design, synthesis and mechanism of novel shikonin derivatives as potent anticancer agents

Novel shikonin derivatives were synthesised and probed as anticancer agents. Compound 40 showed the best anticancer activity with an IC₅₀ of 1.26 μM, could induce apoptosis and cause cell cycle arrest at the G2/M phase via the P21 p-CDC2 (Tyr15) pathway independent of P53.

Synthesis and biological evaluation of heterocyclic carboxylic acyl shikonin derivatives

A series of shikonin derivatives (1-13) that were acylated selectively by various thiophene or indol carboxylic acids at the side chain of shikonin were synthesized, and their biological activities were also evaluated as potential tubulin inhibitors. Among them, compound 3 ((R)-1-(5,8-dihydroxy-1,4-dioxo-1,4-dihydronaphthalen-2-yl)-4-methylpent-3-enyl 3-(1H-indol-3-yl)propanoate) and compound 8 ((R)-1-(5,8-dihydroxy-1,4-dioxo-1,4-dihydronaphthalen-2-yl)-4-methylpent-3-enyl 2-(thiophen-3-yl)acetate) exhibited good antiproliferative activity of A875 (IC50  = 0.005 ± 0.001 μm, 0.009  ± 0.002 μm) and HeLa (IC50  = 11.84 ± 0.64 μm, 4.62  ± 0.31 μm) cancer cell lines in vitro, respectively. Shikonin (IC50  = 0.46 ± 0.002 μm, 4.80 ± 0.48 μm) and colchicine (IC50  = 0.75 ± 0.05 μm, 17.79 ± 0.76 μm) were used as references. Meanwhile, they also showed the most potent growth inhibitory activity against tubulin (IC50 of 3.96  ± 0.13 μm and 3.05 ± 0.30 μm, respectively), which were compared with shikonin (IC50  =  15.20 ± 0.25 μm) and colchicine (IC50  = 3.50 ± 0.35 μm). Furthermore, from the results of flow cytometer, we found compound 3 can really inhibit HeLa cell proliferation and has low cell toxicity. Based on the preliminary results, compound 3 with potent inhibitory activity in tumor growth may be a potential anticancer agent.

Anti-inflammatory effects of β-hydroxyisovalerylshikonin in BV2 microglia are mediated through suppression of the PI3K/Akt/NF-kB pathway and activation of the Nrf2/HO-1 pathway

In the present study, we investigated whether β-hydroxyisovalerylshikonin (β-HIVS) affects the production of proinflammatory mediators such as nitric oxide (NO) and prostaglandin E2 (PGE2) in BV2 microglial cells. Our data showed that β-HIVS inhibited secretion of NO and PGE2 and downregulated expression of their main regulatory genes, inducible NO synthesis (iNOS) and cyclooxygenase-2 (COX-2). β-HIVS also reduced the LPS-induced DNA-binding activity of nuclear factor-κB (NF-κB) by suppressing nuclear translocation of the NF-κB subunits and inhibiting the degradation and phosphorylation of IκBα. Furthermore, an NF-κB inhibitor, pyrrolidine dithiocarbamate (PDTC), attenuated LPS-stimulated iNOS and COX-2 expression, suggesting that NF-κB inhibition is a main effector in the expression of iNOS and COX-2. We also found that LPS-induced NF-κB activation is regulated through inhibition of PI3K/Akt phosphorylation in response to β-HIVS. Additionally, β-HIVS caused the induction of heme oxygenase-1 (HO-1) via upregulation of nuclear factor-erythroid 2-related factor 2 (Nrf2), both of which are involved in the secretion of proinflammatory mediators such as NO and PGE2. Taken together, our data indicate that β-HIVS diminishes the proinflammatory mediators NO and PGE2 and the expression of their regulatory genes, iNOS and COX-2, in LPS-stimulated BV2 microglial cells by inhibiting PI3K/Akt-dependent NF-κB activation and inducing Nrf2-mediated HO-1 expression.

Enhancement of Lymphangiogenesis In Vitro via the Regulations of HIF-1α Expression and Nuclear Translocation by Deoxyshikonin

The objectives of this study were to determine the effects of deoxyshikonin on lymphangiogenesis. Deoxyshikonin enhanced the ability of human dermal lymphatic microvascular endothelial cells (HMVEC-dLy) to undergo time-dependent in vitro cord formation. Interestingly, an opposite result was observed in cells treated with shikonin. The increased cord formation ability following deoxyshikonin treatment correlated with increased VEGF-C mRNA expression to higher levels than seen for VEGF-A and VEGF-D mRNA expression. We also found that deoxyshikonin regulated cord formation of HMVEC-dLy by increasing the HIF-1α mRNA level, HIF-1α protein level, and the accumulation of HIF-1α in the nucleus. Knockdown of the HIF-1α gene by transfection with siHIF-1α decreased VEGF-C mRNA expression and cord formation ability in HMVEC-dLy. Deoxyshikonin treatment could not recover VEGF-C mRNA expression and cord formation ability in HIF-1α knockdown cells. This indicated that deoxyshikonin induction of VEGF-C mRNA expression and cord formation in HMVEC-dLy on Matrigel occurred mainly via HIF-1α regulation. We also found that deoxyshikonin promoted wound healing in vitro by the induction of HMVEC-dLy migration into the wound gap. This study describes a new effect of deoxyshikonin, namely, the promotion of cord formation by human endothelial cells via the regulation of HIF-1α. The findings suggest that deoxyshikonin may be a new drug candidate for wound healing and treatment of lymphatic diseases.

Shikonin, a natural product from the root of Lithospermum erythrorhizon, is a cytotoxic DNA-binding agent

To search for compounds that disrupt binding of the EWS-FLI1 fusion protein to its cognate targets, we developed a homogeneous high-throughput proximity assay and screened 5200 small molecule compounds. Many well-known DNA-binding chemotherapeutic agents, such as actinomycin D, cisplatin, doxorubicin, daunorubicin, and epirubicin scored in the assay and not surprising also disrupted the binding of other transcription factors. Unexpectedly, we found that Shikonin, a natural product from the root of Lithospermum erythrorhizon, similarly disrupted protein-DNA interactions. Mechanistic studies demonstrated that Shikonin displaces SYBR green from binding to the minor groove of DNA and is able to inhibit topoisomerase mediated DNA relaxation. In cells, Shikonin blocked the binding of EWS-FLI1 to the NR0B1 promoter, and attenuated gene expression. Shikonin rapidly induced G2/M arrest and apoptosis in Ewing sarcoma cells. These results demonstrate that contrary to other purported mechanisms of action, Shikonin is a DNA-binding cytotoxic agent.

Preparation, cellular uptake and angiogenic suppression of shikonin-containing liposomes in vitro and in vivo

Shikonin has anticancer activity, but it has not yet been applied into clinical use. In the present study, shikonin was prepared using liposomes. We aimed to examine several aspects of sh-L (shikonin-containing liposomes): preparation, angiogenic suppression and cellular uptake through self-fluorescence. Sh-L were prepared using soybean phospholipid and cholesterol to form the membrane and shikonin was encapsulated into the phospholipid membrane. Three liposomes were prepared with shikonin. They had red fluorescence and were analysed using a flow cytometer. Angiogenic suppression of sh-L was determined using MTT [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-2H-tetrazolium bromide], Transwell tests, chick CAM (chorioallantoic membrane) and Matrigel™ plug assay. MTT assay showed the median IC₅₀ (inhibitory concentrations) as follows: shikonin, sh-L₁ and sh-L₂ were 4.99±0.23, 5.81±0.57 and 7.17±0.69 μM, respectively. The inhibition rates of migration were 53.58±7.05, 46.56±4.36 and 41.19±3.59% for 3.15 μM shikonin, sh-L₁ and sh-L₂, respectively. The results of CAM and Matrigel plug assay demonstrated that shikonin and sh-L can decrease neovascularization. Effect of shikonin was more obvious than sh-L at the same concentration. The results showed that sh-L decreased the toxicity, the rate of inhibition of migration and angiogenic suppression. The cellular uptake of the sh-L could be pictured because of the self-fluorescence. The self-fluorescence will be useful for conducting further research. Sh-L might be an excellent preparation for future clinical application to cancer patients.

Phytochemicals: cancer chemoprevention and suppression of tumor onset and metastasis

Carcinogenesis is a multi-step process which could be prevented by phytochemicals. Phytochemicals from dietary plants and other plant sources such as herbs are becoming increasingly important sources of anticancer drugs or compounds for cancer chemoprevention or adjuvant chemotherapy. Phytochemicals can prevent cancer initiation, promotion, and progression by exerting anti-inflammatory and anti-oxidative stress effects which are mediated by integrated Nrf2, NF-kappaB, and AP-1 signaling pathways. In addition, phytochemicals from herbal medicinal plants and/or some dietary plants developed in recent years have been shown to induce apoptosis in cancer cells and inhibition of tumor growth in vivo. In advanced tumors, a series of changes involving critical signaling molecules that would drive tumor cells undergoing epithelial-mesenchymal transition and becoming invasive. In this review, we will discuss the potential molecular targets and signaling pathways that mediate tumor onset and metastasis. In addition, we will shed light on some of the phytochemicals that are capable of targeting these signaling pathways which would make them potentially applicable to cancer chemoprevention, treatment and control of cancer progression.

Spliceostatin A blocks angiogenesis by inhibiting global gene expression including VEGF

Spliceostatin A (SSA) is a methylated derivative of an antitumor natural product FR901464, which specifically binds and inhibits the SF3b spliceosome sub-complex. To investigate the selective antitumor activity of SSA, we focused on the regulation of vascular endothelial growth factor (VEGF) mRNA, since VEGF is a key regulatory component in tumor angiogenesis and known for the intricate regulation of mRNA processing, such as alternative splicing. We found that in HeLa cells SSA reduced the amount of both mRNA and protein of VEGF. Spliceostatin A not only inhibited the splicing reaction of VEGF pre-mRNA but also reduced the total amount of VEGF's transcripts, while SSA affected GAPDH mRNA to a lesser extent. Given a significant reduction in VEGF gene expression, SSA was expected to possess anti-angiogenic activity in vivo. Indeed, SSA inhibited cancer cell-derived angiogenesis in vivo in a chicken chorioallantoic membrane (CAM) assay. The inhibition of angiogenesis with SSA was abolished by addition of exogenous VEGF. We also performed global gene expression analyses of HeLa cells and found that the expression levels of 38% of total genes including VEGF decreased to <50% of the basal levels following 16 h of SSA treatment. These results suggest that the global interference of gene expression including VEGF in tumor cells is at least one of the mechanisms by which SSA (or FR901464) exhibits its strong antitumor activity.

The Chick Embryo Chorioallantoic Membrane as an In Vivo Assay to Study Antiangiogenesis

Antiangiogenesis, e.g., inhibition of blood vessel growth, is being investigated as a way to prevent the growth of tumors and other angiogenesis-dependent diseases. Pharmacological inhibition interferes with the angiogenic cascade or the immature neovasculature with synthetic or semi-synthetic substances, endogenous inhibitors or biological antagonists.The chick embryo chorioallantoic membrane (CAM) is an extraembryonic membrane, which serves as a gas exchange surface and its function is supported by a dense capillary network. Because its extensive vascularization and easy accessibility, CAM has been used to study morphofunctional aspects of the angiogenesis process in vivo and to study the efficacy and mechanism of action of pro- and anti-angiogenic molecules. The fields of application of CAM in the study of antiangiogenesis, including our personal experience, are illustrated in this review article.

Acyclic retinoid inhibits angiogenesis by suppressing the MAPK pathway

Acyclic retinoid (ACR) is currently under clinical trial as an agent to suppress the recurrence of hepatocellular carcinoma (HCC) through its ability to induce apoptosis in premature HCC cells. ACR has an anticancer effect in vivo as well, although it shows weak apoptosis-inducing activity against mature HCC cells, suggesting the existence of an additional action mechanism. In this study, we investigated the antiangiogenic activity of ACR. ACR inhibited angiogenesis within chicken chorioallantoic membrane (CAM) in as similar a manner as all-trans retinoic acid (atRA). Although suppression of angiogenesis by atRA was partially rescued by the simultaneous addition of angiopoietin-1, suppression of angiogenesis by ACR was not rescued under the same condition at all. Conversely, although suppression of angiogenesis by ACR was partially inverted by the simultaneous addition of vascular endothelial growth factor (VEGF), suppression of angiogenesis by atRA was not affected under the same condition. These results suggested that mechanisms underlying the suppression of angiogenesis by ACR and atRA were different. ACR selectively inhibited the phosphorylation of VEGF receptor 2 (VEGFR2) and of extracellular signal-regulated kinase (ERK) without changing their protein expression levels, and inhibited endothelial cell growth, migration, and tube formation. The inhibition of the phosphorylation of ERK, endothelial growth, migration, tube formation, and angiogenesis by ACR was rescued by the overexpression of constitutively active mitogen-activated protein kinase (MAPK). Finally, ACR, but not atRA, inhibited HCC-induced angiogenesis in a xenografted CAM model. These results delineate the novel activity of ACR as an antiangiogenic through a strong inhibition of the VEGFR2 MAPK pathway.