Involvement of RECK in gambogic acid induced anti-invasive effect in A549 human lung carcinoma cells

Gambogic acid suppresses nasopharyngeal carcinoma via rewiring molecular network of cancer malignancy and immunosurveillance

Nasopharyngeal carcinoma (NPC) is a malignant tumor highly prevalent in Southeast Asia. The distant metastasis and disease recurrence are still unsolved clinical problems. In recent years, traditional Chinese medicine (TCM) monomers have become significantly attractive due to their advantages. Using high throughput drug sensitivity screening, we identified gambogic acid (GA) as a common TCM monomer displaying multiple anti-NPC effects. GA could effectively inhibit the proliferation of low differentiated cells and highly metastatic cells in NPC via inducing apoptosis and G2/M cell cycle arrest. In addition, GA obviously repressed the abilities of cell clone, migration, invasion, angiogenesis and represented satisfied synergistic effects combined with chemotherapy. Importantly, we found the elevated immune checkpoint CD47 stimulated after chemotherapy was dramatically impaired by GA treatment. Mechanically, the network pharmacology analyses unraveled that the oncogenic signaling pathways including STATs were rewired by GA treatment. Taken together, our study reveals a molecular basis and provides a rationale for GA application as the treatment regime in NPC therapy in future.

Targeting the ILK/YAP axis by LFG-500 blocks epithelial-mesenchymal transition and metastasis

Metastasis is the main cause of mortality in patients with cancer. Epithelial-mesenchymal transition (EMT), a crucial process in cancer metastasis, is an established target for antimetastatic drug development. LFG-500, a novel synthetic flavonoid, has been revealed as a potential antitumor agent owing to its various activities, including modulation of EMT in the inflammatory microenvironment. Here, using a transforming growth factor beta (TGF-β)-induced EMT models, we found that LFG-500 inhibited EMT-associated migration and invasion in human breast cancer, MCF-7, and lung adenocarcinoma, A549, cell lines, consistent with the observed downregulation of YAP activity. Further studies demonstrated that LGF-500-induced suppression of YAP activation was mediated by integrin-linked kinase (ILK), suggesting that the ILK/YAP axis might be feasible target for anti-EMT and antimetastatic treatments, which was verified by a correlation analysis with clinical data and tumor specimens. Hence, our data support the use of LGF-500 as an antimetastatic drug in cancer therapy and provide evidence that the ILK/YAP axis is a feasible biomarker of cancer progression and a promising target for repression of EMT and metastasis in cancer therapy.

Combined effects of low-dose gambogic acid and NaI131 in drug-resistant non-small cell lung cancer cells

Radioactive seed brachytherapy is a method for treating drug-resistant, late-stage non-small cell lung cancer (NSCLC). To elucidate the mechanism of low-dose gambogic acid (GA) and NaI¹³¹ in drug-resistant NSCLC cells, the human NSCLC A549 cell line and the drug-resistant A549/cisplatin (DDP) and A549/Taxol cell lines were treated with NaI¹³¹, low-dose GA or a combination of both in the present study; the control group of each cell line was treated with phosphate-buffered saline (PBS). Following treatment, cell proliferation, apoptosis and cell cycle analysis was performed. Apoptosis-related proteins, namely CDK1, cyclin B, mutant p53 (mtp53), heat shock protein 90 (HSP90), Bax and Bcl-2, and P-glycoprotein 1 (P-gp), which is known to confer resistance to chemotherapy, were detected using western blotting and immunofluorescence analysis. mRNA levels of p53 and HSP90 were measured using reverse transcription-quantitative PCR. Compared with the PBS control group, the A549, A549/DDP and A549/Taxol cells treated with NaI¹³¹, GA or a combination of the drugs exhibited G₂/M arrest and increased percentages of total apoptotic cells, as well as significantly decreased protein levels of CDK1, cyclin B, mtp53, HSP90, Bcl-2 and P-gp, increased protein levels of Bax and decreased mRNA levels of p53 and HSP90. The changes in the combination group were the most evident and were significantly different from the other groups (P<0.001). In conclusion, low-dose GA may be a potential radionuclide sensitizer.

Perspectives and controversies regarding the use of natural products for the treatment of lung cancer

Lung cancer is the leading cause of cancer‐related mortality both in men and women and accounts for 18.4% of all cancer‐related deaths. Although advanced therapy methods have been developed, the prognosis of lung cancer patients remains extremely poor. Over the past few decades, clinicians and researchers have found that chemical compounds extracted from natural products may be useful for treating lung cancer. Drug formulations derived from natural compounds, such as paclitaxel, doxorubicin, and camptothecin, have been successfully used as chemotherapeutics for lung cancer. In recent years, hundreds of new natural compounds that can be used to treat lung cancer have been found through basic and sub‐clinical research. However, there has not been a corresponding increase in the number of drugs that have been used in a clinical setting. The probable reasons may include low solubility, limited absorption, unfavorable metabolism, and severe side effects. In this review, we present a summary of the natural compounds that have been proven to be effective for the treatment of lung cancer, as well as an understanding of the mechanisms underlying their pharmacological effects. We have also highlighted current controversies and have attempted to provide solutions for the clinical translation of these compounds.

Gambogic Acid as a Candidate for Cancer Therapy: A Review

Gambogic acid (GA), a kind of dry resin secreted by the Garcinia hanburyi tree, is a natural active ingredient with various biological activities, such as anti-cancer, anti-inflammatory, antioxidant, anti-bacterial effects, etc. An increasing amount of evidence indicates that GA has obvious anti-cancer effects via various molecular mechanisms, including the induction of apoptosis, autophagy, cell cycle arrest and the inhibition of invasion, metastasis, angiogenesis. In order to improve the efficacy in cancer treatment, nanometer drug delivery systems have been employed to load GA and form micelles, nanoparticles, nanofibers, and so on. In this review, we aim to offer a summary of chemical structure and properties, anti-cancer activities, drug delivery systems and combination therapy of GA, which might provide a reference to promote the development and clinical application of GA.

Cell-penetrating peptides in oncologic pharmacotherapy: A review

Cancer is the second leading cause of death in the world and its treatment is extremely challenging, mainly due to its complexity. Cell-Penetrating Peptides (CPPs) are peptides that can transport into the cell a wide variety of biologically active conjugates (or cargoes), and are, therefore, promising in the treatment and in the diagnosis of several types of cancer. Some notable examples are TAT and Penetratin, capable of penetrating the central nervous system (CNS) and, therefore, acting in cancers of this system, such as Glioblastoma Multiforme (GBM). These above-mentioned peptides, conjugated with traditional chemotherapeutic such as Doxorubicin (DOX) and Paclitaxel (PTX), have also been shown to induce apoptosis of breast and liver cancer cells, as well as in lung cancer cells, respectively. In other cancers, such as esophageal cancer, the attachment of Magainin 2 (MG2) to Bombesin (MG2B), another CPP, led to pronounced anticancer effects. Other examples are CopA3, that selectively decreased the viability of gastric cancer cells, and the CPP p28. Furthermore, in preclinical tests, the anti-tumor efficacy of this peptide was evaluated on human breast cancer, prostate cancer, ovarian cancer, and melanoma cells in vitro, leading to high expression of p53 and promoting cell cycle arrest. Despite the numerous in vitro and in vivo studies with promising results, and the increasing number of clinical trials using CPPs, few treatments reach the expected clinical efficacy. Usually, their clinical application is limited by its poor aqueous solubility, immunogenicity issues and dose-limiting toxicity. This review describes the most recent advances and innovations in the use of CPPs in several types of cancer, highlighting their crucial importance for various purposes, from therapeutic to diagnosis. Further clinical trials with these peptides are warranted to examine its effects on various types of cancer.

Gambogic acid affects ESCC progression through regulation of PI3K/AKT/mTOR signal pathway

Esophageal squamous cell carcinoma (ESCC) is an invasive gastrointestinal malignancy and in urgent need of new effective therapies. Gambogic acid (GA) exhibits anti-cancer effects in many cancer cells, but it remains to be determined whether GA has the same effect on ESCC. Here, we reported that GA treatment caused an inhibition in ESCC cell proliferation, migration and invasion. Meanwhile, GA induced dose-dependent apoptosis of ESCC cells, repressed the expression of Bcl2 and up-regulated the levels of Bax protein, cleaved-PARP1 and cleaved-caspase 3/9. Further investigation showed that GA down-regulated the levels of PI3K, p-AKT and p-mTOR, while promoted PTEN expression in ESCC cells. Taken together, we provided the first demonstration that GA exerts anti-tumor effects on ESCC cells presumably through regulating PTEN-PI3K-AKT-mTORpathway, suggestive of a therapeutic potential for ESCC.

Dual drug-loaded nano-platform for targeted cancer therapy: toward clinical therapeutic efficacy of multifunctionality

Background

Poor targeting and penetration of chemotherapy drugs in solid tumors, and the development of resistance to chemotherapeutic agents are currently hindering the therapy of breast cancer; meanwhile, breast cancer metastasis is one of the leading causes of death in breast cancer patients. With the development of nanotechnology, nanomaterials have been widely used in tumor therapy.

Results

A multi-functional nano-platform containing gambogic acid (GA) and paclitaxel (PTX) was characterized by a small size, high encapsulation efficiency, slow release, long systemic circulation time in vivo, showed good targeting and penetrability to tumor tissues and tumor cells, and exhibited higher anti-tumor effect and lower systemic toxicity in BALB/c mice bearing 4T1 tumor. GA not only overcame the multidrug resistance of PTX by inhibiting P-glycoprotein (P-gp) activity in MCF-7/ADR cells, but also inhibited MDA-MB-231 cells migration and invasion, playing a crucial role in preventing and treating the lung metastasis of breast cancer caused by PTX; meanwhile, the synergistic anti-tumor effect of GA and PTX has also been verified in vitro and in vivo experiments.

Conclusion

Our data described the better recognition and penetration of tumor cells of R9dGR-modified versatile nanosystems containing GA and PTX, which exerted one stone three birds clinical therapeutic efficacy of multifunctionality.

Gambogic acid: A shining natural compound to nanomedicine for cancer therapeutics

The United States Food and Drug Administration has permitted number of therapeutic agents for cancer treatment. Most of them are expensive and have some degree of systemic toxicity which makes overbearing in clinical settings. Although advanced research continuously applied in cancer therapeutics, but drug resistance, metastasis, and recurrence remain unanswerable. These accounts to an urgent clinical need to discover natural compounds with precisely safe and highly efficient for the cancer prevention and cancer therapy. Gambogic acid (GA) is the principle bioactive and caged xanthone component, a brownish gamboge resin secreted from the of Garcinia hanburyi tree. This molecule showed a spectrum of biological and clinical benefits against various cancers. In this review, we document distinct biological characteristics of GA as a novel anti-cancer agent. This review also delineates specific molecular mechanism(s) of GA that are involved in anti-cancer, anti-metastasis, anti-angiogenesis, and chemo-/radiation sensitizer activities. Furthermore, recent evidence, development, and implementation of various nanoformulations of gambogic acid (nanomedicine) have been described.

Anti-angiogenic and anti-proliferative effects of Benja-ummarit extract in rats with hepatocellular carcinoma

The herbal extract Benja-ummarit (BU) is a traditional Thai medicine with a putative cancer-suppressing effect. However, this effect has only been tested in vitro in human hepatocarcinoma cell lines. The present study determined the efficacy of a BU extract to treat hepatocellular carcinoma (HCC) in rats in vivo and established its anti-angiogenic and anti-proliferative properties. The BU extract was prepared in 95% ethanol and its composition determined using liquid chromatography-mass spectrometry. HCC was induced in Wistar rats by an injection of diethylnitrosamine (DEN), followed 2 weeks later by injections of thioacetamide (TAA) thrice weekly for 4 weeks. Following 2 months, the DEN-TAA-treated rats were divided into 6 groups that were treated orally for another 2 months with: i) No treatment; ii) vehicle; iii) 30 mg/kg sorafenib (SF); iv) 1 mg/kg BU; v) 10 mg/kg BU; or vi) 50 mg/kg BU. Liver samples were collected for gross morphological, histological, reverse transcription-quantitative PCR and western blot analyses, and serum samples were collected for liver function tests. The size and number of the cancer nodules were reduced ~10-fold in BU-treated HCC groups and ~14-fold in the SF-treated group compared with the HCC group. Furthermore, the serum parameters of liver damage were lower in BU-compared with SF-treated rats. These results indicate that while each of these formulations strongly reduce HCC expansion, BU extract results in less liver damage. Vascular endothelial growth factor expression was reduced significantly in the BU-and SF-treated HCC groups compared with the HCC group (P<0.05). BU extract antagonizes HCC growth in vivo potently through inhibiting tumor angiogenesis. BU, therefore, qualifies as a promising medical herb requiring further evaluation as a treatment of HCC.

Gambogic acid exhibits anti-metastatic activity on malignant melanoma mainly through inhibition of PI3K/Akt and ERK signaling pathways

Gambogic acid (GA) is a potential anti-cancer compound that is extracted from the resin of Garciania hanburyi. The present study was designed to evaluate the anti-metastatic effect of GA on melanoma cell lines in vitro and to explore the underlying mechanism. The anti-proliferative activity of GA on melanoma cells was assessed by CCK-8 assay. The Wound-healing, transwell, adhesion, and tube formation assays were performed to examine the inhibition of GA on the cell's migration, invasion, adhesion, and angiogenesis capacities, respectively. Enzymatic activity of MMP-2 and MMP-9 were detected by gelatin zymography assay. Protein expressions regulated by GA treatment were tested by Western blot assay. The present results showed that GA significantly inhibited the proliferation of highly metastatic melanoma A375, B16-F10 cells and human umbilical vein endothelial cells (HUVECs) in time- and doses-dependent manners. Furthermore, GA significantly inhibited the migratory, invasive and adhesive properties of A375 and B16-F10 cells, and tube-forming potential of HUVECs at sub-IC50 concentrations, where no significant cytotoxicity was observed. Mechanistically, GA treatment suppressed the EMT and angiogenesis processes and reduced the enzymatic activity of MMP-2 and MMP-9. Moreover, abnormal PI3K/Akt and ERK signaling pathways in A375 and B16-F10 cells and HUVECs were notably suppressed by GA treatment. Collectively, our results suggest that GA exerts anti-metastasis activity in melanoma cells by suppressing the EMT and angiogenesis through the PI3K/Akt and ERK signaling pathways, and might be used as a phytomedicine against metastatic melanoma.

Naturally occurring anti-cancer compounds: shining from Chinese herbal medicine

Numerous natural products originated from Chinese herbal medicine exhibit anti-cancer activities, including anti-proliferative, pro-apoptotic, anti-metastatic, anti-angiogenic effects, as well as regulate autophagy, reverse multidrug resistance, balance immunity, and enhance chemotherapy in vitro and in vivo. To provide new insights into the critical path ahead, we systemically reviewed the most recent advances (reported since 2011) on the key compounds with anti-cancer effects derived from Chinese herbal medicine (curcumin, epigallocatechin gallate, berberine, artemisinin, ginsenoside Rg3, ursolic acid, silibinin, emodin, triptolide, cucurbitacin B, tanshinone I, oridonin, shikonin, gambogic acid, artesunate, wogonin, β-elemene, and cepharanthine) in scientific databases (PubMed, Web of Science, Medline, Scopus, and Clinical Trials). With a broader perspective, we focused on their recently discovered and/or investigated pharmacological effects, novel mechanism of action, relevant clinical studies, and their innovative applications in combined therapy and immunomodulation. In addition, the present review has extended to describe other promising compounds including dihydroartemisinin, ginsenoside Rh2, compound K, cucurbitacins D, E, I, tanshinone IIA and cryptotanshinone in view of their potentials in cancer therapy. Up to now, the evidence about the immunomodulatory effects and clinical trials of natural anti-cancer compounds from Chinese herbal medicine is very limited, and further research is needed to monitor their immunoregulatory effects and explore their mechanisms of action as modulators of immune checkpoints.

Involvement of E-cadherin/AMPK/mTOR axis in LKB1-induced sensitivity of non-small cell lung cancer to gambogic acid

Liver kinase B1 (LKB1) is a tumor suppressor that functions as master regulator of cell growth, metabolism, survival, and polarity. Patients with NSCLC possessing mutated LKB1 respond to chemotherapy differently from those with wild-type LKB1. Gambogic acid (GA), a small molecule from natural product, has been established as an anti-tumor agent due to its potent activity and low toxicity. Here, we find out that NSCLC cells with wild-type LKB1 are more sensitive to GA in vitro and in vivo. Mechanistic studies pinpoint that the selective inhibition of mTOR signaling confers the stronger suppression of NSCLC in presence of wild-type LKB1, which is involved in the enhancement of p-AMPK. Further studies reveal that GA increases p-AMPK levels through up-regulation of E-cadherin associated with LKB1. In addition, induction of E-cadherin by GA may be through down-regulation of ZEB1, which is independent with LKB1 status. Hence, our findings support that enhanced E-cadherin by GA cooperates LKB1, leading to up-regulation of p-AMPK, and thus blocking of mTOR signaling pathway, which provide theoretical foundation for utilization of GA as a potential targeted drug against NSCLC harboring wild-type LKB1.

Dimeric c(RGD) peptide conjugated nanostructured lipid carriers for efficient delivery of Gambogic acid to breast cancer

Background and purpose: Gambogic acid (GA) is a natural compound that exhibited a promising multi-target antitumor activity against several types of cancer. However, the clinical application of this drug is limited due to its poor solubility and low tumor cell-specific delivery. In this study, the monomeric and dimeric Cyclo (Arg-Gly-Asp) c(RGD) tumor targeting peptides (c(RGDfK) and E-[c(RGDfK)2]) were used to modify GA loaded nanostructured lipid carriers (NLC) to reduce the limitations associated with GA and improve its antitumor activity. Methods: GA-NLC was prepared by emulsification and solvent evaporation methods and the surface of the NLC was conjugated with the c(RGD) peptides via an amide bond. The formulations were characterized for particle size, morphology and zeta potential, encapsulation efficiency and drug loading. The in-vitro cytotoxicity and cell uptake studies were conducted using 4T1 cell. Furthermore, the in-vivo antitumor activity and bio-distribution study were performed on female BALB/c nude mice. Results: The c(RGD) peptides modified GA-NLC was successfully prepared with the particles size about 20 nm. The HPLC analysis, FT-IR and 1H-NMR spectra confirmed the successful conjugation of the peptides with the NLC. The in-vitro cytotoxicity study on 4T1 cells revealed that c(RGD) peptides modified GA-NLCs showed significantly higher cytotoxicity at 0.25 and 0.5 µg/mL as compared to unmodified GA-NLC. Furthermore, the cell uptake study demonstrated that better accumulation of E-[c(RGDfK)2] peptides modified NLC in 4T1 cell after 12 h incubation. Moreover, the in-vivo study showed that c(RGD)s functionalized GA-NLC exhibited better accumulation in tumor tissue and tumor growth inhibition. In contrast to the monomeric c(RGD) peptide, the dimeric c(RGD) peptide (E-[c(RGDfK)2]) conjugated GA-NLC showed the improved antitumor activity and tumor targeting ability of GA-NLC. Conclusion: These data provide further support for the potential clinical applications of E-[c(RGDfK)2]-GA-NLC in breast cancer therapy.

Gambogic acid reverses oxaliplatin resistance in colorectal cancer by increasing intracellular platinum levels

Resistance to oxaliplatin (L-OHP) is a major obstacle to successful chemotherapy in colorectal cancer (CRC). In the present study, the ability of gambogic acid (GA) to reverse L-OHP resistance in CRC LoVo cells was investigated. L-OHP-resistant LoVo/L-OHP cells were established by exposing them to increasing concentrations of L-OHP. GA-reversed L-OHP-sensitive LoVo/L-OHP/GA cells were established by exposure to 0.5 µmol/l GA for 2 weeks. A Cell Counting Kit-8 assay was used to assess levels of proliferation. Flow cytometry was applied to detect apoptosis rates. Transwell assays were used to analyse invasion. Inductively coupled plasma mass spectrometry was used to determine intracellular platinum (Pt) content. Western blot analysis was used to reveal the protein levels of Human copper transporter 1 (hCTR1), Copper-transporting p-type adenosine triphosphatases 1 (ATP7A) and Copper-transporting p-type adenosine triphosphatases 2 (ATP7B). LoVo/L-OHP and LoVo/L-OHP/GA cell lines were successfully established, and it was identified that L-OHP inhibited the proliferation of LoVo, LoVo/L-OHP and LoVo/L-OHP/GA cells in a dose-dependent manner. Compared with the parent LoVo cells, the anti-apoptosis and invasion properties of LoVo/L-OHP cells were enhanced, and were reversed by GA treatment. Intracellular Pt content was highest in the LoVo cells, followed by LoVo/L-OHP/GA cells, and then lowest in the LoVo/L-OHP cells. Downregulated hCTP1 and upregulated ATP7A and ATP7B were associated with L-OHP resistance, and GA reversed the resistance by increasing levels of hCTR1 and decreasing levels of ATP7A and ATP7B. In conclusion, GA has the potential ability to reverse L-OHP resistance in CRC cells by increasing intracellular Pt content, which it achieves by increasing hCTR1 levels and decreasing ATP7A and ATP7B levels. GA may represent a promising treatment agent for L-OHP resistance.

Cell-penetrating peptide conjugates of gambogic acid enhance the antitumor effect on human bladder cancer EJ cells through ROS-mediated apoptosis

Background

Gambogic acid (GA) is the main active ingredient of resin gamboges and possesses anti-cancer activity toward various human cancer cells. However, clinical application of GA has been limited by its poor aqueous solubility and dose-limiting toxicities. Cell-penetrating peptides (CPPs) are widely used to deliver anti-cancer drugs into cancer cells and to enhance the water solubility of drugs.

Purpose

The object of this study was to synthesize peptide-drug conjugates in which the cell-penetrating peptide TAT (trans-activator of transcription) was conjugated to GA and evaluated the anti-cancer activity of this GA-CPP conjugate (GA-TAT) in EJ bladder cancer cells.

Methods

GA is built onto the TAT, and the GA-TAT conjugates are cleaved from the solid support and purified via HPLC. The equilibrium solubility of GA-TAT was measured using the shake-flask method. The effects of GA-TAT on EJ cell viability and proliferation were determined by MTT assay, Edu assay and colony formation assay, respectively. After treated with 1.0 μM GA-TAT for 24 h, the apoptosis rate of EJ cells were detected by Acridine orange/ethidium bromide (AO/EB) assay and flow cytometry assay. The proteins of caspase-3 (processing), caspase-9 (processing), Bcl-2 and Bax were analyzed by Western blotting, and the intracellular reactive oxygen species (ROS) production was evaluated by a reactive oxygen species assay.

Results

In contrast to free GA, the solubility of GA-TAT in water was significantly improved. Meanwhile, GA-TAT significantly increased EJ cellular uptake, toxicity and apoptosis. Mechanistic analysis revealed that GA-TAT enhanced the anti-cancer effect of GA against EJ cells through ROS-mediated apoptosis. The results were demonstrated that GA-TAT increased the ROS level in EJ cells, and N-acetyl-L-cysteine (NAC; a well-known ROS scavenger) inhibited GA-TAT-induced ROS generation and apoptosis. Additionally, GA-TAT activated caspase-3 and caspase-9 and down-regulated the Bcl-2/Bax ratio, but these effects were largely rescued by NAC.

Conclusion

GA-TAT has outstanding potential for promoting tumor apoptosis and exhibits promise for use in bladder cancer therapy.

The growth inhibitory effect of gambogic acid on pancreatic cancer cells

Pancreatic cancer, the fourth most common cause of cancer-related deaths, is one of the most aggressive and devastating human malignancies with increasing incidence worldwide. To date, surgical resection is the only potentially curative therapy available for pancreatic cancer patients. Early diagnosis of pancreatic tumors is difficult, and hence, nearly 80% of patients cannot receive surgical resection. Natural products have always been a vital source for novel compounds for cancer treatment. The naturally occurring prenylated xanthone, gambogic acid, has been previously shown to exert potent anticancer, anti-inflammatory, apoptotic, antiangiogenic, and antioxidant activities. However, to our knowledge, there have been no specific studies showing its effect on the whole-genome expression in pancreatic cancer cells. Here, the anticancer activity of gambogic acid toward a panel of pancreatic cancer cells with different differentiation stages has been evaluated. Additionally, a whole-genome transcription profiling study was performed in order to identify possible candidate players modulating the antitumor effect of gambogic acid on pancreatic cancer cells. Expression analysis results showed that the pancreatic adenocarcinoma signaling pathway was specifically affected upon gambogic acid treatment. Moreover, the growth inhibitory effect of gambogic acid on pancreatic cancer cells was modulated through up-regulation of DDIT3, DUSP1, and DUSP5 and down-regulation of ALDOA, TOP2A, and ATG4B. The present work is a starting point for the generation of hypotheses on significantly regulated candidate key player genes and for a detailed dissection of the potential role of each individual gene for the activity of gambogic acid on pancreatic cancer.

Gambogic acid suppresses cancer invasion and migration by inhibiting TGFβ1-induced epithelial-to-mesenchymal transition

The epithelial-to-mesenchymal transition (EMT) contributes to the disruption of cell–cell junctions and imbues cancer cells with invasive and migratory properties. In this study, we investigated the effect of gambogic acid, a xanthone extracted from the resin of Garciania hanburyi, on transforming growth factor β1 (TGFβ1)-induced EMT. Gambogic acid inhibited the invasion and migration of TGFβ1-induced A549 cells in vitro. Gambogic acid also increased the mRNA and protein expression of E-cadherin, but repressed the mRNA and protein expression of N-cadherin, vimentin, and transcription factor TWIST1. Further examination of the mechanism revealed that the nuclear factor κB (NF-κB) pathway is involved in this regulation of EMT-related biomarkers. Gambogic acid inhibited NF-κB p65 nuclear translocation and the phosphorylation of the inhibitor of NF-κB (IκBα) and IκBα kinase (IKKα). Gambogic acid also suppressed the EMT induced by TGFβ1 and tumor necrosis factor α by inhibiting the NF-κB pathway. Our data also indicate that gambogic acid inhibited the primary lesion and lung metastasis of orthotopic model of A549 cells in vivo. We propose that gambogic acid might be developed as a candidate drug with therapeutic potential for the treatment of cancer invasion and migration.

Therapeutic potential of gambogic acid, a caged xanthone, to target cancer

Natural compounds have enormous biological and clinical activity against dreadful diseases such as cancer, as well as cardiovascular and neurodegenerative disorders. In spite of the widespread research carried out in the field of cancer therapeutics, cancer is one of the most prevalent diseases with no perfect treatment till date. Adverse side effects and the development of chemoresistance are the imperative limiting factors associated with conventional chemotherapeutics. For this reason, there is an urgent need to find compounds that are highly safe and efficacious for the prevention and treatment of cancer. Gambogic acid (GA) is a xanthone structure extracted from the dry, brownish gamboge resin secreted from the Garcinia hanburyi tree in Southeast Asia and has inherent anti-cancer properties. In this review, the molecular mechanisms underlying the targets of GA that are liable for its effective anti-cancer activity are discussed that reveal the potential of GA as a pertinent candidate that can be appropriately developed and designed into a capable anti-cancer drug.

An overview of anticancer activity of Garcinia and Hypericum

Cancer is one of the leading causes of death worldwide (approximately 8.2 million cases/year) and, over the next two decades, a 70% increase in new cancer cases is expected. Through analysis of the available drugs between the years of 1930 and 2014, it was found that 48% were either natural products or their derivatives. This proportion increased to 66% when semi-synthetic products were included. The family Clusiaceae Juss. (Malpighiales) includes approximately 1000 species distributed throughout all tropical and temperate regions. The phytochemical profile of this family includes many chemicals with interesting pharmacological activities, including anticancer activities. This study includes an overview of the in vitro and in vivo anticancer activity of secondary metabolites from Garcinia and Hypericum and the mechanisms involved in this activity. Hypericum no longer belong to Clusiaceae family, but was considered in the past by taxonomists, due to similarities with this family. Research in the area has shown that several compounds belonging to different chemical classes exhibit activity in several tumor cell lines in different experimental models. This review shows the significant antineoplasic activity of these compounds, in particular of these two genera and validates the importance of natural products in the search for anticancer drugs.

Gambogic acid potentiates the chemosensitivity of colorectal cancer cells to 5-fluorouracil by inhibiting proliferation and inducing apoptosis

Chemotherapy using 5-fluorouracil (5-FU) for colorectal cancer (CRC) has low specificity and response rates, leading to severe side effects. Gambogic acid (GA), a traditional Chinese medicine, has multi-targeted anticancer effects, including growth inhibition and apoptosis induction. However, it is unclear whether a combination of 5-FU and GA has synergistic anticancer effects in CRC cells. In this study, SW480 and HCT116 human CRC cells and human intestinal epithelial cells (IECs) were treated with different concentrations of 5-FU, GA or 5-FU+GA. A Cell Counting kit-8 assay was conducted to quantify cell proliferation. The combination index (CI) was calculated and the median-effect principle was applied to analyze the interaction between 5-FU and GA. Flow cytometry was used to determine the percentage of cells undergoing apoptosis. Reverse transcription-quantitative polymerase chain reaction and western blotting were applied to measure P53, survivin and thymidylate synthase (TS) mRNA and protein levels. It was found that 5-FU+GA more pronouncedly inhibited cell growth and induced apoptosis, compared with either monotherapy. CI values <1 indicated the synergistic effects of the drugs. 5-FU+GA further decreased P53, survivin and TS mRNA and protein levels in the two CRC cell lines compared with single drugs, whereas increased P53 protein levels were observed in HCT116 cells. Moreover, 5-FU+GA did not increase cytotoxicity to IECs. These results demonstrate that GA enhances the anticancer effects of 5-FU on CRC cells. Combined treatment with 5-FU and GA is effective and safe for CRC cells, and may become a promising chemotherapy treatment.

Role of gambogic acid and NaI131 in A549/DDP cells

Resistance to platinum in tumor tissue is a considerable barrier against effective lung cancer treatment. Radionuclide therapy is the primary adjuvant treatment, however, the toxic side effects limit its dosage in the clinical setting. Therefore, the present study aimed to determine whether an NaI¹³¹ radiosensitizer could help reduce the toxic side effects of radionuclide therapy. In vitro experiments were conducted to determine whether NaI¹³¹ can inhibit platinum resistance in A549/DDP cells, which are cisplatin-resistant non-small cell lung cancer cells, and whether gambogic acid (GA) is an effective NaI¹³¹ radiosensitizer. Cell proliferation following drug intervention was analyzed using MTT and isobolographic analysis. Apoptosis was assessed by flow cytometry. In addition, the mechanisms of drug intervention were analyzed by measuring the expression of P-glycoprotein (P-gP), B cell lymphoma 2 (Bcl-2), Bcl2-associated X protein (Bax) and P53 using western blot analysis and immunocytochemistry. According to isobolographic analysis, a low concentration of NaI¹³¹ combined with GA had a synergistic effect on the inhibition of A549/DDP cell proliferation, which was consistent with an increased rate of apoptosis. Furthermore, the overexpression of Bax, and the downregulation of P-gP, P53 and Bcl-2 observed demonstrated the potential mechanism(s) of NaI¹³¹ and GA intervention. NaI¹³¹ may induce apoptosis in A549/DDP cells by regulating apoptosis-related proteins. A low concentration combination of NaI¹³¹ and GA was able to significantly inhibit A549/DDP cell proliferation and induce cell apoptosis. Thus, the two drugs appear to have a synergistic effect on apoptosis of A549/DDP cells.

Steroid receptor coactivator-3 is a pivotal target of gambogic acid in B-cell Non-Hodgkin lymphoma and an inducer of histone H3 deacetylation

Gambogic acid (GA), the active ingredient from gamboges, has been verified as a potent anti-tumor agent in many cancer cells. Nevertheless, its function in lymphoma, especially in B-cell Non-Hodgkin lymphoma (NHL), remains unclear. Amplification and/or overexpression of steroid receptor coactivator-3 (SRC-3) have been detected in multiple tumors and have confirmed its critical roles in carcinogenesis, progression, metastasis and therapy resistance in these cancers. However, no clinical data have revealed the overexpression of SRC-3 and its role in B-cell NHL. In this study, we demonstrated the anti-tumor effects of GA, which included cell growth inhibition, G1/S phase cell cycle arrest and apoptosis in B-cell NHL. We also verified that SRC-3 was overexpressed in B-cell NHL in both cell lines and lymph node samples from patients. The overexpressed SRC-3 was a central drug target of GA, and its down-regulation subsequently modulated down-stream gene expression, ultimately contributing to apoptosis. Silencing SRC-3 decreased the expression of Bcl-2, Bcl-6 and cyclin D3, but not of NF-κB and IκB-α. GA treatment did not inhibit the activation of AKT signaling pathway, but induced the deacetylation of histone H3 at lysine 9 and lysine 27. Down-regulated SRC-3 was observed to interact with more HDAC1 to mediate the deacetylation of H3. As the component of E3 ligase, Cullin3 was up-regulated and mediated the degradation of SRC-3. Our results demonstrate that GA is a potent anti-tumor agent that can be used for therapy against B-cell NHL, especially against those with an abundance of SRC-3.

Xanthones from the Leaves of Garcinia cowa Induce Cell Cycle Arrest, Apoptosis, and Autophagy in Cancer Cells

Two new xanthones, cowaxanthones G (1) and H (2), and 23 known analogues were isolated from an acetone extract of the leaves of Garcinia cowa. The isolated compounds were evaluated for cytotoxicity against three cancer cell lines and immortalized HL7702 normal liver cells, whereby compounds 1, 5, 8, and 15-17 exhibited significant cytotoxicity. Cell cycle analysis using flow cytometry showed that 5 induced cell cycle arrest at the S phase in a dose-dependent manner, 1 and 16 at the G2/M phase, and 17 at the G1 phase, while 16 and 17 induced apoptosis. Moreover, autophagy analysis by GFP-LC3 puncta formation and western blotting suggested that 17 induced autophagy. Taken together, our results suggest that these xanthones possess anticancer activities targeting cell cycle, apoptosis, and autophagy signaling pathways.

Gambogic acid induces apoptosis and inhibits colorectal tumor growth via mitochondrial pathways

AIM: To investigate the effect of gambogic acid (GA) on apoptosis in the HT-29 human colon cancer cell line.

METHODS: H-29 cells were used for in vitro experiments in this study. Relative cell viability was assessed using MTT assays. Cell apoptosis was detected by terminal deoxynucleotidyl transferase dUTP nick end labeling and Hoechst 33342 staining, and quantified by flow cytometry. Cellular ultrastructure was observed by transmission electron microscopy. Real-time PCR and Western blot analyses were used to evaluate gene and protein expression levels. For in vivo experiments, BALB/c nude mice received subcutaneous injections of HT-29 cells in the right armpit. When well-established xenografts were palpable with a tumor size of 75 mm³, mice were randomly assigned to a vehicle (negative) control, positive control or GA treatment group (n = 6 each). The animals in the treatment group received one of three dosages of GA (in saline; 5, 10 or 20 mg/kg) via the caudal vein twice weekly, whereas animals in the negative and positive control groups were given equal volumes of 0.9% saline or 10 mg/kg docetaxel, respectively, via the caudal vein once weekly.

RESULTS: The cell viability assay showed that GA inhibited proliferation of HT-29 cells in a dose- and time-dependent manner after treatment with GA (0.00, 0.31, 0.62, 1.25, 2.50, 5.00 or 10.00 μmol/L) for 24, 48 or 72 h. After 48 h, the percentage of apoptotic cells in cells treated with 0.00, 1.25, 2.50 and 5.00 μmol/L GA was 1.4% ± 0.3%, 9.8% ± 1.2%, 25.7% ± 3.3% and 49.3% ± 5.8%, respectively. Ultrastructural analysis of HT-29 cells treated for 48 h with 2.5μmol/L GA revealed apoptotic bodies and condensed and fragmented nuclei. Levels of caspase-8, -9 and -3 mRNAs were significantly increased after treatment with GA (1.25, 2.50 or 5.00 μmol/L) for 48 h (P < 0.05 for all). Protein levels of apoptosis-related factors Fas, FasL, FADD, cytochrome c, and Apaf-1 were increased in GA-treated cells, whereas levels of pro-caspase-8, -9 and -3 were significantly decreased (P < 0.05 for all). Furthermore, GA significantly and dose-dependently inhibited the growth of HT-29 tumors in a mouse xenograft model (P < 0.05).

CONCLUSION: GA inhibits HT-29 proliferation via induction of apoptosis. The anti-cancer effects are likely mediated by death receptor (extrinsic) and mitochondrial (intrinsic) pathways.

Gambogic Acid lysinate induces apoptosis in breast cancer mcf-7 cells by increasing reactive oxygen species

Gambogic acid (GA) inhibits the proliferation of various human cancer cells. However, because of its water insolubility, the antitumor efficacy of GA is limited. Objectives. To investigate the antitumor activity of gambogic acid lysinate (GAL) and its mechanism. Methods. Inhibition of cell proliferation was determined by MTT assay; intracellular ROS level was detected by staining cells with DCFH-DA; cell apoptosis was determined by flow cytometer and the mechanism of GAL was investigated by Western blot. Results. GAL inhibited the proliferation of MCF-7 cells with IC₅₀ values 1.46 μmol/L comparable with GA (IC₅₀, 1.16 μmol/L). GAL promoted the production of ROS; however NAC could remove ROS and block the effect of GAL. GAL inhibited the expression of SIRT1 but increased the phosphorylation of FOXO3a and the expression of p27Kip1. At knockdown of FOXO3a, cell apoptosis induced by GAL can be partly blocked. In addition it also enhanced the cleavage of caspase-3. Conclusions. GAL inhibited MCF-7 cell proliferation and induced MCF-7 cell apoptosis by increasing ROS level which could induce cell apoptosis by both SIRT1/FOXO3a/p27Kip1 and caspase-3 signal pathway. These results suggested that GAL might be useful as a modulation agent in cancer chemotherapy.

Four new cytotoxic xanthones from Garcinia nujiangensis

Bioassay-guided fractionation of the acetone extract of the twigs of Garcinia nujiangensis resulted in the isolation of four new prenylated xanthones, nujiangexanthones C-F (1-4), and ten known related analogues. The structures of compounds 1-4 were elucidated by interpretation of their spectroscopic data. The compounds isolated were evaluated for their cytotoxic effects against three cancer cell lines, the test substances demonstrated selectivity toward the cancer cells.

Gambogic acid suppresses cytochrome P450 3A4 by downregulating pregnane X receptor and up-regulating DEC1 in human hepatoma HepG2 cells

Gambogic acid suppresses cytochrome P450 3A4 by downregulating pregnane X receptor and up-regulating DEC1 in human hepatoma HepG2 cells.