Gambogic acid synergistically potentiates cisplatin-induced apoptosis in non-small-cell lung cancer through suppressing NF-κB and MAPK/HO-1 signalling

Anti-cancer potential of zerumbone in cancer and glioma: current trends and future perspectives

Plant-derived immunomodulators and antitumor factors have appealed lots of attention from natural product scientists for their efficiency and safety and their important contribution to well-designed targeted drug action and delivery mechanisms. Zerumbone (ZER), the chief component of Zingiber zerumbet rhizomes, has been examined for its wide-spectrum in the treatment of multi-targeted diseases. The rhizomes have been used as food flavoring agents in numerous cuisines and in flora medication. Numerous in vivo and in vitro experiments have prepared confirmation of ZER as a potent immunomodulator as well as a potential anti-tumor agent. This review is an interesting compilation of all the important results of the research carried out to date to investigate the immunomodulatory and anticancer properties of ZER. The ultimate goal of this comprehensive review is to supply updated information and a crucial evaluation on ZER, including its chemistry and immunomodulating and antitumour properties, which may be of principal importance to supply a novel pathway for subsequent investigation to discover new agents to treat cancers and immune-related sickness. In addition, updated information on the toxicology of ZER has been summarized to support its safety profile.

Emerging tendencies for the nano-delivery of gambogic acid: a promising approach in oncotherapy

Despite the advancements in cancer therapies during the past few years, chemo/photo resistance, severe toxic effects, recurrence of metastatic tumors, and non-selective targeting remain incomprehensible. Thus, much effort has been spent exploring natural anticancer compounds endowed with biosafety and high effectiveness in cancer prevention and therapy. Gambogic acid (GA) is a promising natural compound in cancer therapy. It is the major xanthone component of the dry resin extracted from the Garcinia hanburyi Hook. f. tree. GA has significant antiproliferative effects on different types of cancer, and it exerts its anticancer activities through various pathways. Nonetheless, the clinical translation of GA has been hampered, partly due to its water insolubility, low bioavailability, poor pharmacokinetics, rapid plasma clearance, early degradation in blood circulation, and detrimental vascular irritation. Lately, procedures have been invented demonstrating the ability of nanoparticles to overcome the challenges associated with the clinical use of natural compounds both in vitro and in vivo. This review sheds light on the recent emerging trends for the nanodelivery of GA to cancer cells. To the best of our knowledge, no similar recent review described the different nanoformulations designed to improve the anticancer therapeutic activity and targeting ability of GA.

Novel oxicam nonsteroidal compound XK01 attenuates inflammation by suppressing the NF-κB and MAPK pathway in RAW264.7 macrophages

Traditional non-steroidal anti-inflammatory drugs (NSAIDs) show serious adverse effects during clinical use, which limits their usage. Oxicams (e.g., piroxicam, meloxicam) are widely used as NSAIDs. However, selectivity to cyclooxygenase (COX) 2 may cause cardiovascular problems considering the long-term use of the drugs. Therefore, it is important to develop new non-steroidal compounds as anti-inflammatory drugs. In the present study, we evaluated the anti-inflammatory activity of a newly developed nonsteroidal drug XK01. Our data showed that XK01 reduced the contents of nitric oxide (NO) and reactive oxygen species (ROS)and inhibited the transcription levels of tumor necrosis factor-α (TNF-α), interleukin (IL)-6, and IL-1β in a dose-dependent manner in lipopolysaccharide (LPS)-stimulated mouse RAW264.7 macrophages. XK01 showed no significant inhibitory effect on COX-1, but inhibited the expression of COX-2. At molecular level, XK01 prevented the translocation of p65 protein from the cytoplasm to the nucleus and inhibited the phosphorylation of p65, IκB, and MAPKs proteins. And high concentration of XK01 also inhibited the phosphorylation of JNK, p38 and ERK, showing stronger effect than that of meloxicam. In addition, the anti-inflammatory activity of XK01 was further validated in Xylene-induced mouse ear swelling model. Thus, this study verified that XK01 inhibits the expression of inflammatory mediators and COX-2, and exhibits potential anti-inflammatory effects via suppressing the NF-κB and MAPK pathway.

Design, Synthesis and Anti-cancer Evaluation of Nitrogen-containing Derivatives of 30-Carboxyl of Gambogic Acid

BACKGROUND

Gambogic acid (GA) is a natural product from the resin of the Garcinia species, which showed significant activity in the induction of apoptosis. .t can be one promising lead compound for the design and synthesis of new anticancer drugs.

OBJECTIVE

The objective of the current study is to design novel nitrogen-contained GA derivatives with better anti-cancer activities and study the effect of the introduction of different nitrogen-contained groups on the activity of GA.

METHODS

The designed 15 derivatives were synthesized via esterification or amidation of 30-carboxylate. The synthetic compounds were characterized via different spectroscopic techniques, including X-ray single crystal diffraction, MS and NMR. The cytotoxic activity of the designed derivatives was evaluated in vitro against A549, HepG-2, and MCF-7 cell lines using methyl thiazolyl tetrazolium (MTT) test.

RESULTS

15 nitrogen-contained GA derivatives were successfully synthesized and established. Based on the IC50 values, compounds 9, 10, 11 and 13 showed stronger inhibitory effects on A549, HepG-2, MCF-7 cell lines than GA, while 9 is the most active compound with IC50 value of 0.64-1.49 μM. Most derivatives of GA with esterification of C-30 including cyano-benzene ring were generally weaker than those of pyrimidinyl-substituted derivatives. In addition, length of alkyl linkers between C-30 of GA and nitrogen-contained group produced different effects on A549, HepG-2 and MCF-7 cell lines.

CONCLUSION

The structure-activity relationship results show that aromatic substituent and linker length play important roles to improve the anticancer activities, while compound 9 with pyrimidine substituent and C-C-C linkers is the most active derivative against tested cell lines, and is a promising anti-cancer agent for further development.

Long-circulating gambogic acid-loaded nanodiamond composite nanosystem with inhibition of cell migration for tumor therapy

Herein, ultra dispersed and stably suspended nanodiamonds (NDs) were demonstrated to have a high load capacity, sustained release, and ability to serve as a biocompatible vehicle for delivery anticancer drugs. NDs with size of 50-100 nm exhibited good biocompatibility in normal human liver (L-02) cells. In particular, 50 nm ND not only promoted the noticeable proliferation of the L-02 cells but also can effectively inhibited the migration of human liver carcinoma (HepG2) cells. The gambogic acid-loaded nanodiamond (ND/GA) complex assembled by π-π stacking exhibits ultrasensitive and apparent suppression efficiency on the proliferation of HepG2 cells through high internalization and less efflux compared to free GA. More importantly, the ND/GA system can significantly increase the intracellular reactive oxygen species (ROS) levels in HepG2 cells and thus induce the cell apoptosis. The increase in intracellular ROS levels causes damage to the mitochondrial membrane potential (MMP) and activates cysteinyl aspartate specific proteinase 3 (Caspase-3) and cysteinyl aspartate specific proteinase 9 (Caspase-9), which leads to the occurrence of apoptosis. In vivo experiments also confirmed that the ND/GA complex has a much higher anti-tumor capability than free GA. Thus, the current ND/GA system is promising for cancer therapy.

Modulation of Nrf2/HO-1 by Natural Compounds in Lung Cancer

Oxidative stresses (OSs) are considered a pivotal factor in creating various pathophysiological conditions. Cells have been able to move forward by modulating numerous signaling pathways to moderate the defects of these stresses during their evolution. The company of Kelch-like ECH-associated protein 1 (Keap1) as a molecular sensing element of the oxidative and electrophilic stress and nuclear factor erythroid 2 (NF-E2)-related factor 2 (Nrf2) as a master transcriptional regulator of the antioxidant response makes a master cytoprotective antioxidant pathway known as the Keap1/Nrf2 pathway. This pathway is considered a dual-edged sword with beneficial features for both normal and cancer cells by regulating the gene expression of the array of endogenous antioxidant enzymes. Heme oxygenase-1 (HO-1), a critical enzyme in toxic heme removal, is one of the clear state indicators for the duality of this pathway. Therefore, Nrf2/HO-1 axis targeting is known as a novel strategy for cancer treatment. In this review, the molecular mechanism of action of natural antioxidants on lung cancer cells has been investigated by relying on the Nrf2/HO-1 axis.

Postsurgical wound management and prevention of triple-negative breast cancer recurrence with a pryoptosis-inducing, photopolymerizable hydrogel

Surgical removal remains the predominant treatment strategy for triple-negative breast cancer (TNBC). However, risks that include high locoregional recurrence and remote metastasis threaten patient survival and quality of life after surgery. In this study, a hydrogel based on poly (ethylene glycol) dimethacrylate and sericin methacryloyl was fabricated by photopolymerization to fill the resection cavity and prevent recurrence. The obtained hydrogel exhibited mechanical properties compatible with breast tissue and facilitated postsurgical wound management by promoting tissue regeneration. The DNA methylation inhibitor decitabine (DEC) and poly (lactic-co-glycolic acid)-encapsulated phytochemical gambogic acid (GA) were loaded into the hydrogel. The as-prepared hydrogel promoted fast release of DEC and sustained release of GA, leading to gasdermin E-mediated tumor cell pyroptosis and activating antitumor immune responses. Inducing postsurgical tumor cell pyroptosis inhibited local tumor recurrence and lung metastasis. While the dual-drug-loaded hydrogel system cured less than half of tumor-bearing mice, the cured mice survived for over half a year. These findings indicate that our hydrogel system is an excellent biocompatible platform for postsurgical TNBC therapy.

Exploration of the Use of Natural Compounds in Combination with Chemotherapy Drugs for Tumor Treatment

Currently, chemotherapy is the main treatment for tumors, but there are still problems such as unsatisfactory chemotherapy results, susceptibility to drug resistance, and serious adverse effects. Natural compounds have numerous pharmacological activities which are important sources of drug discovery for tumor treatment. The combination of chemotherapeutic drugs and natural compounds is gradually becoming an important strategy and development direction for tumor treatment. In this paper, we described the role of natural compounds in combination with chemotherapeutic drugs in synergizing, reducing drug resistance, mitigating adverse effects and related mechanisms, and providing new insights for future oncology research.

Gambogic acid and juglone inhibit RNase P through distinct mechanisms

The first step in transfer RNA (tRNA) maturation is the cleavage of the 5' end of precursor tRNA (pre-tRNA) catalyzed by ribonuclease P (RNase P). RNase P is either a ribonucleoprotein complex with a catalytic RNA subunit or a protein-only RNase P (PRORP). In most land plants, algae, and Euglenozoa, PRORP is a single-subunit enzyme. There are currently no inhibitors of PRORP for use as tools to study the biological function of this enzyme. Therefore, we screened for compounds that inhibit the activity of a model PRORP from A. thaliana organelles (PRORP1) using a high throughput fluorescence polarization cleavage assay. Two compounds, gambogic acid and juglone (5-hydroxy-1,4-naphthalenedione) that inhibit PRORP1 in the 1 μM range were identified and analyzed. We found these compounds similarly inhibit human mtRNase P, a multisubunit protein enzyme and are 50-fold less potent against bacterial RNA-dependent RNase P. Our biochemical measurements indicate that gambogic acid is a rapid-binding, uncompetitive inhibitor targeting the PRORP1-substrate complex, while juglone acts as a time-dependent PRORP1 inhibitor. Additionally, X-ray crystal structures of PRORP1 in complex with juglone demonstrate the formation of a covalent complex with cysteine side chains on the surface of the protein. Finally, we propose a model consistent with the kinetic data that involves juglone binding to PRORP1 rapidly to form an inactive enzyme-inhibitor complex and then undergoing a slow step to form an inactive covalent adduct with PRORP1. These inhibitors have the potential to be developed into tools to probe PRORP structure and function relationships.

Cisplatin Resistance: Genetic and Epigenetic Factors Involved

Cisplatin (CDDP) is the drug of choice against different types of cancer. However, tumor cells can acquire resistance to the damage caused by cisplatin, generating genetic and epigenetic changes that lead to the generation of resistance and the activation of intrinsic resistance mechanisms in cancer cells. Among them, we can find mutations, alternative splicing, epigenetic-driven expression changes, and even post-translational modifications of proteins. However, the molecular mechanisms by which CDDP resistance develops are not clear but are believed to be multi-factorial. This article highlights a description of cisplatin, which includes action mechanism, resistance, and epigenetic factors involved in cisplatin resistance.

Opportunities and challenges for co-delivery nanomedicines based on combination of phytochemicals with chemotherapeutic drugs in cancer treatment

The therapeutic limitations such as insufficient efficacy, drug resistance, metastasis, and undesirable side effects are frequently caused by the long duration monotherapy based on chemotherapeutic drugs. multiple combinational anticancer strategies such as nucleic acids combined with chemotherapeutic agents, chemotherapeutic combinations, chemotherapy and tumor immunotherapy combinations have been embraced, holding great promise to counter these limitations, while still taking including some potential risks. Nowadays, an increasing number of research has manifested the anticancer effects of phytochemicals mediated by modulating cancer cellular events directly as well as the tumor microenvironment. Specifically, these natural compounds exhibited suppression of cancer cell proliferation, apoptosis, migration and invasion of cancer cells, P-glycoprotein inhibition, decreasing vascularization and activation of tumor immunosuppression. Due to the low toxicity and multiple modulation pathways of these phytochemicals, the combination of chemotherapeutic agents with natural compounds acts as a novel approach to cancer therapy to increase the efficiency of cancer treatments as well as reduce the adverse consequences. In order to achieve the maximized combination advantages of small-molecule chemotherapeutic drugs and natural compounds, a variety of functional nano-scaled drug delivery systems, such as liposomes, host-guest supramolecules, supramolecules, dendrimers, micelles and inorganic systems have been developed for dual/multiple drug co-delivery. These co-delivery nanomedicines can improve pharmacokinetic behavior, tumor accumulation capacity, and achieve tumor site-targeting delivery. In that way, the improved antitumor effects through multiple-target therapy and reduced side effects by decreasing dose can be implemented. Here, we present the synergistic anticancer outcomes and the related mechanisms of the combination of phytochemicals with small-molecule anticancer drugs. We also focus on illustrating the design concept, and action mechanisms of nanosystems with co-delivery of drugs to synergistically improve anticancer efficacy. In addition, the challenges and prospects of how these insights can be translated into clinical benefits are discussed.

Gambogic Acid Induces HO-1 Expression and Cell Apoptosis through p38 Signaling in Oral Squamous Cell Carcinoma

Gambogic acid (GA), a natural and bioactive compound from the gamboge resin, has been reported to exhibit many oncostatic activities against several types of malignancies. However, its effects on the progression of oral squamous cell carcinoma (OSCC) remain largely unexplored. To fill this gap, we investigated the anticancer role of GA and molecular mechanisms underlying GA's actions in combating oral cancer. We found that GA negatively regulated the viability of OSCC cells, involving induction of the sub-G1 phase and cell apoptosis. In addition, a specific signature of apoptotic proteome, such as upregulation of heme oxygenase-1 (HO-1) and activation of caspase cascades, was identified in GA-treated OSCC. Moreover, such induction of HO-1 expression and caspase cleavage by GA was significantly diminished through the pharmacological inhibition of p38 kinase. In conclusion, these results demonstrate that GA promotes cell apoptosis in OSCC, accompanied with the activation of a p38-dependent apoptotic pathway. Our findings provide potential avenues for the use of GA with high safety and therapeutic implications in restraining oral cancer.

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.

Sustained delivery of gambogic acid from mesoporous rod-structure hydroxyapatite for efficient in vitro cancer therapy

Inspired by the critical role of nanocarrier in biomaterials modification, we synthesized a mesoporous rod-structure hydroxyapatite (MR-HAp) nanoparticles for boosting gambogic acid (GA) bioavailability in cells and improving the tumor therapy. As expected, the GA loading ratio of MR-HAp was up to about 96.97% and GA-loaded MR-HAp (MR-HAp/GA) demonstrates a sustained release performance. Furthermore, a substantial improvement was observed in inhibiting the cell proliferation and inducing the apoptosis of HeLa cells, as the cell viability was decreased to 89.6% and the apoptosis was increased to 49.2% when the cells treated with MR-HAp/GA at a GA concentration of 1 μg/mL for 72 h. The remarkable inhibition effect of cell proliferation and the enhanced inducing apoptosis are attributed to the increasing intracellular reactive oxygen species level and reduced mitochondrial membrane potential. This result provides a promising and facile approach for highly efficient tumor treatment.

In Situ Nanoparticle Self-Assembly for Combination Delivery of Therapeutics to Non-Small Cell Lung Cancer

Chemotherapy often experiences several challenges including severe systemic toxicity and adverse effects. The combination chemotherapy arose as an effective clinical practice aimed at reducing doses of drugs to achieve synergistic actions with low toxicity. Our recent efforts demonstrated a synergistic therapeutic benefit of gambogic acid (GA) and gemcitabine (Gem) against lung cancer. However, simultaneous delivery of these two drugs at the tumor site is highly challenging. Therefore, the development of an injectable formulation that can effectively deliver both hydrophobic (GA) and hydrophilic (Gem) drugs in one formulation is a clinically unmet need. Herein, this study reports an in situ human serum albumin (HSA)- and tannic acid (TA)-mediated complexed GA and Gem nanoparticles (G-G@HTA NPs). G-G@HTA NP formation was confirmed by the particle size, Fourier transform infrared spectroscopy, and ¹H NMR spectroscopy. The superior therapeutic activity of G-G@HTA NPs was demonstrated by multiple in vitro functional assays. Additionally, G-G@HTA NPs revealed an obvious and precise targeting of tumors in vivo. The promoted and more synergistic anti-tumor efficacy of G-G@HTA NPs was attained than that of combined treatments and single drug treatments. These events have resulted in no apparent systemic and organ toxicities. Together, this study suggests that in situ HSA-TA-based combinatorial treatment strategy is a suitable approach for application in lung cancer treatment.

Localized disruption of redox homeostasis boosting ferroptosis of tumor by hydrogel delivery system

Ferroptosis has received ever-increasing attention due to its unparalleled mechanism in eliminating resistant tumor cells. Nevertheless, the accumulation of toxic lipid peroxides (LPOs) at the tumor site is limited by the level of lipid oxidation. Herein, by leveraging versatile sodium alginate (ALG) hydrogel, a localized ferroptosis trigger consisting of gambogic acid (GA), 2,2'-azobis [2-(2-imidazolin-2-yl) propane] dihydrochloride (AIPH), and Ink (a photothermal agent), was constructed via simple intratumor injection. Upon 1064 ​nm laser irradiation, the stored AIPH rapidly decomposed into alkyl radicals (R•), which aggravated LPOs in tumor cells. Meanwhile, GA could inhibit heat shock protein 90 (HSP90) to reduce the heat resistance of tumor cells, and forcefully consume glutathione (GSH) to weaken the antioxidant capacity of cells. Systematic in vitro and in vivo experiments have demonstrated that synchronous consumption of GSH and increased reactive oxygen species (ROS) facilitated reduced expression of glutathione peroxidase 4 (GPX4), which further contributed to disruption of intracellular redox homeostasis and ultimately boosted ferroptosis. This all-in-one strategy has a highly effective tumor suppression effect by depleting and generating fatal active compounds at tumor sites, which would pave a new route for the controllable, accurate, and coordinated tumor treatments.

Pathogenesis and therapeutic strategy in platinum resistance lung cancer

Platinum compounds (cisplatin and carboplatin) represent the most active anticancer agents in clinical use both of lung cancer in mono-and combination therapies. However, platinum resistance limits its clinical application. It is necessary to understand the molecular mechanism of platinum resistance, identify predictive markers, and develop newer, more effective and less toxic agents to treat platinum resistance in lung cancer. Here, it summarizes the main molecular mechanisms associated with platinum resistance in lung cancer and the development of new approaches to tackle this clinically relevant problem. Moreover, it could lead to the development of more effective treatment for refractory lung cancer in future.

Targeting Bcl-2 for cancer therapy

Apoptosis deficiency is one of the most important features observed in neoplastic diseases. The Bcl-2 family is composed of a subset of proteins that act as decisive apoptosis regulators. Research and clinical studies have both demonstrated that the hyperactivation of Bcl-2-related anti-apoptotic effects correlates with cancer occurrence, progression and prognosis, also having a role in facilitating the radio- and chemoresistance of various malignancies. Therefore, targeting Bcl-2 inactivation has provided some compelling therapeutic advantages by enhancing apoptotic sensitivity or reversing drug resistance. Therefore, this pharmacological route turned into one of the most promising routes for cancer treatment. This review discusses some of the well-defined and emerging roles of Bcl-2 as well as its potential clinical value in cancer therapeutics.

Dihydroartemisinin Sensitizes Esophageal Squamous Cell Carcinoma to Cisplatin by Inhibiting Sonic Hedgehog Signaling

Platinum-based regimens have been routinely used in the clinical treatment of patients with esophageal squamous cell carcinoma (ESCC). However, administration of these drugs is frequently accompanied by drug resistance. Revealing the underlying mechanisms of the drug resistance and developing agents that enhance the sensitivity to platinum may provide new therapeutic strategies for the patients. In the present study, we found that the poor outcome of ESCC patients receiving platinum-based regimens was associated with co-expression of Shh and Sox2. The sensitivity of ESCC cell lines to cisplatin was related to their activity of Shh signaling. Manipulating of Shh expression markedly changed the sensitivity of ESCC cells to platinum. Continuous treatment with cisplatin resulted in the activation of Shh signaling and enhanced cancer stem cell-like phenotypes in ESCC cells. Dihydroartemisinin (DHA), a classic antimalarial drug, was identified as a novel inhibitor of Shh pathway. Treatment with DHA attenuated the cisplatin-induced activation of the Shh pathway in ESCC cells and synergized the inhibitory effect of cisplatin on proliferation, sphere and colony formation of ALDH-positive ESCC cells in vitro and growth of ESCC cell-derived xenograft tumors in vivo. Taken together, these results demonstrate that the Shh pathway is an important player in cisplatin-resistant ESCC and DHA acts as a promising therapeutic agent to sensitize ESCC to cisplatin treatment.

Gambogic acid potentiates gemcitabine induced anticancer activity in non-small cell lung cancer

Non-small cell lung cancer (NSCLC) is the most frequent type of lung cancer accounting up to 80-85% of all lung cancer (LC) cases. Gemcitabine (Gem), a pyrimidine nucleoside antimetabolite, is widely used chemotherapy offering several months survival benefit in patients with NSCLC. The emergence of Gem resistance is a main clinical concern in cancer treatment and thus a continuous demand for development of new therapeutic strategies to improve its antitumor activity. Hence, we report an adjuvant therapeutic regimen based on natural compound, gambogic acid (GA) which has been shown to enhanced Gem induced inhibition of cancer cell growth, arrest cell cycle, and induce apoptosis by enhanced accumulation of Gem. The in vitro cell viability, clonogenicity, invasion, and migration assays demonstrated a significant higher therapeutic effect of Gem when it was combined with GA in A549 and H1299 cells. A better access of internalization of drug molecules achieved in rhodamine 123 assay when GA was used as adjuvant treatment. Further, GA and Gem combination significantly reduced tubular formation of HUVEC cells indicates lowering angiogenesis potential. Microarray and Western blot studies confirm that GA + Gem co-treatment strategy promotes cancer cell death by downregulating anti-apoptotic proteins, chemoresistance-associated proteins, and upregulation of apoptosis proteins. More importantly, a significant higher therapeutic benefit was noticed for GA and Gem combination in A549 xenograft mice model. Together, these results offer a rationale to evaluate the clinical translational possibility of GA as adjuvant therapy to overcome Gem resistance. This combination regimen can be a new therapeutic concept to eradicate this devastating disease.

NF-κB inhibitors in treatment and prevention of lung cancer

Intracellular signalling pathways have provided excellent resource for drug development particularly in the development of cancer therapeutics. A wide variety of malignancies common in human exhibit aberrant NF-κB constitutive expression which results in tumorigenic processes and cancer survival in a variety of solid tumour, including pancreatic cancer, lung, cervical, prostate, breast and gastric carcinoma. Numerous evidences indicate that NF-κB signalling mechanism is mainly involved in the progression of several cancers which may intensify an enhanced knowledge on its role in disease particularly lung tumorigenesis. This has led to tremendous research in designing a variety of NF-κB antagonists with enhanced clinical applications through different approaches the most common being suppression of IκB kinase (IKK) beta activity. Many NF-κB inhibitors for lung cancer are now under clinical trials. Preliminary results of clinical trials for several of these agents include small-molecule inhibitors and monoclonal antibodies. A few combinatorial treatment therapies are currently under investigation in the clinics and have shown promise, particularly NF-κB inhibition associated with lung cancer.

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.

Penetratin-modified lutein nanoemulsion in-situ gel for the treatment of age-related macular degeneration

Background: Lutein is the primary macular pigment with an favorable effect on the treatment of age-related macular degeneration (AMD). However, the poor water solubility of lutein hinders its absorption and delivery. In this study, a penetratin-modified lutein nanoemulsion in-situ gel (GEL) was prepared for the treatment of AMD.Methods: A nanoemulsion (NE) was prepared and modified with penetratin (P-NE) to improve the penetration. The effect of penetratin was evaluated by cell uptake and intraocular distribution assays. A dry AMD model was induced using NaIO₃, and the therapeutic effect was evaluated by electroretinography, the number of apoptosis cells and the reactive oxygen species (ROS) level.Results: Lutein showed a good ability to protect ARPE-19 from the damage of H₂O₂ and the uptake rate of P-NE was significantly higher than NE. In the efficacy experiments, the structure of retina was significantly improved after treatment, the apoptosis rate decreased from 31.98% to 2.05%, and the level of ROS was significantly decreased (p < 0.0001).Conclusions: With the aid of penetratin, lutein could be delivered to the retina effectively. The P-NE GEL could evidently inhibit the apoptosis and ROS, demonstrating that the P-NE GEL has a good application prospect in the treatment of AMD.

Loss of Tumor Suppressor CYLD Expression Triggers Cisplatin Resistance in Oral Squamous Cell Carcinoma

Cisplatin is one of the most effective chemotherapeutic agents commonly used for several malignancies including oral squamous cell carcinoma (OSCC). Although cisplatin resistance is a major obstacle to effective treatment and is associated with poor prognosis of OSCC patients, the molecular mechanisms by which it develops are largely unknown. Cylindromatosis (CYLD), a deubiquitinating enzyme, acts as a tumor suppressor in several malignancies. Our previous studies have shown that loss of CYLD expression in OSCC tissues is significantly associated with poor prognosis of OSCC patients. Here, we focused on CYLD expression in OSCC cells and determined whether loss of CYLD expression is involved in cisplatin resistance in OSCC and elucidated its molecular mechanism. In this study, to assess the effect of CYLD down-regulation on cisplatin resistance in human OSCC cell lines (SAS), we knocked-down the CYLD expression by using CYLD-specific siRNA. In cisplatin treatment, cell survival rates in CYLD knockdown SAS cells were significantly increased, indicating that CYLD down-regulation caused cisplatin resistance to SAS cells. Our results suggested that cisplatin resistance caused by CYLD down-regulation was associated with the mechanism through which both the reduction of intracellular cisplatin accumulation and the suppression of cisplatin-induced apoptosis via the NF-κB hyperactivation. Moreover, the combination of cisplatin and bortezomib treatment exhibited significant anti-tumor effects on cisplatin resistance caused by CYLD down-regulation in SAS cells. These findings suggest the possibility that loss of CYLD expression may cause cisplatin resistance in OSCC patients through NF-κB hyperactivation and may be associated with poor prognosis in OSCC patients.

Targeting Reactive Oxygen Species in Cancer via Chinese Herbal Medicine

Recently, reactive oxygen species (ROS), a class of highly bioactive molecules, have been extensively studied in cancers. Cancer cells typically exhibit higher levels of basal ROS than normal cells, primarily due to their increased metabolism, oncogene activation, and mitochondrial dysfunction. This moderate increase in ROS levels facilitates cancer initiation, development, and progression; however, excessive ROS concentrations can lead to various types of cell death. Therefore, therapeutic strategies that either increase intracellular ROS to toxic levels or, conversely, decrease the levels of ROS may be effective in treating cancers via ROS regulation. Chinese herbal medicine (CHM) is a major type of natural medicine and has greatly contributed to human health. CHMs have been increasingly used for adjuvant clinical treatment of tumors. Although their mechanism of action is unclear, CHMs can execute a variety of anticancer effects by regulating intracellular ROS. In this review, we summarize the dual roles of ROS in cancers, present a comprehensive analysis of and update the role of CHM—especially its active compounds and ingredients—in the prevention and treatment of cancers via ROS regulation and emphasize precautions and strategies for the use of CHM in future research and clinical trials.

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.

Lobaplatin-Induced Apoptosis Requires p53-Mediated p38MAPK Activation Through ROS Generation in Non-Small-Cell Lung Cancer

Platinum-based chemotherapy is recommended as the first-line treatment regimen for patients with advanced non-small-cell lung cancer (NSCLC). Lobaplatin (LBP), a third-generation platinum anti-neoplastic agent, has shown an improved efficacy. This study is aimed to investigate the mechanisms of LBP-induced apoptosis in the A549 p53 wild-type cell line. The Cell Counting Kit-8 assay (CCK-8), flow cytometry (FCM), Western blot, xenograft tumor models, terminal deoxynucleotide transferase dUTP nick end labeling (TUNEL), and RNA interference were used in this study. Our results showed that the proliferation of A549 cells could be inhibited by LBP. At lower concentrations, LBP triggered cell cycle arrest at the G1 phase in A549 cells. LBP could also induce apoptosis of A549 cells. LBP also increased the expression of PARP and Bax and the cleavage of caspase-3, caspase-8, and caspase-9 and reduced Bcl-2 expression. In vivo experiment confirmed that LBP could inhibit tumor growth in the A549 xenograft models and induce apoptosis. Apoptosis of A549 cells was decreased after transfected with p53 shRNA or treated with reactive oxygen species inhibitor NAC and p38MAPK inhibitor SB203580, suggesting that the p53/ROS/p38MAPK pathway appeared to mediate the LBP-induced apoptosis of A549 cells. Our data demonstrate that LBP could be a promising candidate for the treatment of NSCLC with wild-type p53.

Traditional Chinese medicine-combination therapies utilizing nanotechnology-based targeted delivery systems: a new strategy for antitumor treatment

Cancer is a major public health problem, and is now the world’s leading cause of death. Traditional Chinese medicine (TCM)-combination therapy is a new treatment approach and a vital therapeutic strategy for cancer, as it exhibits promising antitumor potential. Nano-targeted drug-delivery systems have remarkable advantages and allow the development of TCM-combination therapies by systematically controlling drug release and delivering drugs to solid tumors. In this review, the anticancer activity of TCM compounds is introduced. The combined use of TCM for antitumor treatment is analyzed and summarized. These combination therapies, using a single nanocarrier system, namely codelivery, are analyzed, issues that require attention are determined, and future perspectives are identified. We carried out a systematic review of >280 studies published in PubMed since 1985 (no patents involved), in order to provide a few basic considerations in terms of the design principles and management of targeted nanotechnology-based TCM-combination therapies.

Gambogic acid triggers vacuolization-associated cell death in cancer cells via disruption of thiol proteostasis

Gambogic acid (GA), a xanthonoid extracted from the resin of the tree, Garcinia hanburyi, was recently shown to exert anticancer activity in multiple studies, but the underlying action mechanism remains unclear. Here, we show that GA induces cancer cell death accompanied by vacuolation in vitro and in vivo. This GA-induced vacuolation in various cancer cells was derived from dilation of the endoplasmic reticulum (ER) and mitochondria, and was blocked by cycloheximide. These findings suggest that GA kills cancer cells by inducing paraptosis, a vacuolization-associated cell death. We found that megamitochondria formation, which arose from the fusion of swollen mitochondria, preceded the fusion of ER-derived vacuoles. GA-induced proteasomal inhibition was found to contribute to the ER dilation and ER stress seen in treated cancer cells, and megamitochondria formation was followed by mitochondrial membrane depolarization. Interestingly, GA-induced paraptosis was effectively blocked by various thiol-containing antioxidants, and this effect was independent of ROS generation. We observed that GA can react with cysteinyl thiol to form Michael adducts, suggesting that the ability of GA to covalently modify the nucleophilic cysteinyl groups of proteins may cause protein misfolding and subsequent accumulation of misfolded proteins within the ER and mitochondria. Collectively, our findings show that disruption of thiol proteostasis and subsequent paraptosis may critically contribute to the anti-cancer effects of GA.

Phytochemicals: Current strategy to sensitize cancer cells to cisplatin

Cisplatin-based chemotherapeutic regimens are the most frequently used adjuvant treatments for many types of cancer. However, the development of chemoresistance to cisplatin results in treatment failure. Despite the significant developments in understanding the mechanisms of cisplatin resistance, effective strategies to enhance the chemosensitivity of cisplatin are lacking. Phytochemicals are naturally occurring plant-based compounds that can augment the anti-cancer activity of cisplatin, with minimal side effects. Notably, some novel phytochemicals, such as curcumin, not only increase the efficacy of cisplatin but also decrease toxicity induced by cisplatin. However, the exact mechanisms underlying this process remain unclear. In this review, we discussed the progress made in utilizing phytochemicals to enhance the anti-cancer efficacy of cisplatin. We also presented some ideal phytochemicals as novel agents for counteracting cisplatin-induced organ damage.

Gambogic Acid Induces Apoptosis of Non-Small Cell Lung Cancer (NSCLC) Cells by Suppressing Notch Signaling

BACKGROUND Activation of Notch signaling was found to be associated with cancer. Gambogic acid (GA) was reported to be an anti-cancer agent. This study investigated the anti-cancer effect of GA on human non-small cell lung cancer (NSCLC) cells. Involvement of the Notch pathway was also studied. MATERIAL AND METHODS GA at 0, 0.5, 0.75, and 1.0 μmol/l was used to incubate A549 and SPC-A1 cells. MTT assay was used to determine the cell viability. TUNEL assay was used to detect the apoptosis. Western blotting was used to evaluate protein expression levels, protein phosphorylation levels, and nuclear translocation levels. RESULTS Notch signaling pathway was activated in NSCLC cells. GA treatment significantly inhibited NSCLC cell viability and increased cell apoptosis. GA treatment significantly decreased the expression levels of DLL1, DLL3, DLL4, Jagged1, Jagged2, Bcl2, and PK3K, inhibited NICD nuclear translocation and Akt phosphorylation, and increased expression level of active caspase3. CONCLUSIONS GA inhibited NSCLC cell viability by inducing apoptosis. Inhibition of the Notch signaling pathway was the mechanism involved in the anti-proliferation effect of GA on NSCLC.

Anti-EGFR-iRGD recombinant protein modified biomimetic nanoparticles loaded with gambogic acid to enhance targeting and antitumor ability in colorectal cancer treatment

Background

Red blood cell membrane-coated nanoparticle (RBCm-NP) platform, which consist of natural RBCm and synthetic polymeric core, can extend circulation time in vivo with an improved biocompatibility and stability of this biomimetic nanocarrier. To achieve better bioavailability of antitumor drugs that were loaded in RBCm-NPs, the functionalization of coated RBCm with specific targeting ability is essential. Bispecific recombinant protein anti-EGFR-iRGD, containing both tumor penetrating peptide (internalizing RGD peptide) and EGFR single-domain antibody (sdAb), seems to be an optimal targeting ligand for RBCm-NPs in the treatment of multiple tumors, especially colorectal cancer with high EGFR expression.

Materials and methods

We modified the anti-EGFR-iRGD recombinant protein on the surface of RBCm-NPs by lipid insertion method to construct iE-RBCm-PLGA NPs and confirmed the presentation of active tumor-targeting ability in colorectal cancer models with high EGFR expression when compared with RBCm-PLGA NPs. In addition, potential anti-tumor drug gambogic acid (GA) was loaded into the NPs to endow the antitumor efficiency of iE-RBCm-GA/PLGA NPs. It was simultaneously evaluated whether GA can reach better biocompatibility benefiting from the improved antitumor efficiency of iE-RBCm-GA/PLGA NPs in colorectal cancer models.

Results

We successfully modified anti-EGFR-iRGD proteins on the surface of biomimetic NPs with integrated and stable "shell-core" structure. iE-RBCm-PLGA NPs showed its improved targeting ability in vitro (multicellular spheroids [MCS]) and in vivo (nude mice bearing tumors). Besides, no matter on short-term cell apoptosis at tumor site (terminal deoxyribonucleotidyl transferase-mediated dUTP nick end labeling [TUNEL]) and long-term tumor inhibition, iE-RBCm-GA/PLGA NPs achieved better antitumor efficacy than free GA in spite of the similar effects of cytotoxicity and apoptosis to GA in vitro.

Conclusion

We expect that the bispecific biomimetic nanocarrier can extend the clinical application of many other potential antitumor drugs similar to GA and become a novel drug carrier in the colorectal cancer treatment.

Gambogic acid regulates the migration and invasion of colorectal cancer via microRNA-21-mediated activation of phosphatase and tensin homolog

Gambogic acid (GA) has been reported to inhibit cancer cell proliferation and migration and enhance apoptosis. Several signaling pathways were identified to be involved in GA function, including PI3K/Akt, caspase-3 apoptosis and TNF-α/NF-κB. However, to the best of our knowledge, the association between miRNA and GA has not been explored. The present study initially demonstrated that GA could inhibit HT-29 cancer cell proliferation using an MTT assay. In addition, a Transwell assay and a wound-healing assay respectively indicated that GA inhibited HT-29 cancer cell invasion and migration, which was also confirmed by the increased MMP-9 protein expression. Furthermore, GA induced the apoptosis of HT-29 cancer cells in an Annexin V and PI double staining assay. Moreover, treatment with GA significantly decreased miR-21 expression in these cells. Additionally, western blot analysis demonstrated that GA treatment enhanced the activation of phosphatase and tensin homolog (PTEN) along with the suppression of PI3K and p-Akt. Furthermore, miR-21 mimics reversed all the aforementioned activities of GA, which indicated that miR-21 was the effector of GA and blocked PI3K/Akt signaling pathway via enhancing PTEN activity. In summary, GA induced HT-29 cancer cell apoptosis via decreasing miR-21 expression and blocking PI3K/Akt, which may be a useful novel insight for future CRC treatment.

Artocarpin, an isoprenyl flavonoid, induces p53-dependent or independent apoptosis via ROS-mediated MAPKs and Akt activation in non-small cell lung cancer cells

Artocarpin has been shown to exhibit cytotoxic effects on different cancer cells, including non-small cell lung carcinoma (NSCLC, A549). However, the underlying mechanisms remain unclear. Here, we explore both p53-dependent and independent apoptosis pathways in artocarpin-treated NSCLC cells. Our results showed that artocarpin rapidly induced activation of cellular protein kinases including Erk1/2, p38 and AktS473. Inhibition of these protein kinases prevented artocarpin-induced cell death. Moreover, artocarpin-induced phosphorylation of these protein kinases and apoptosis were mediated by induction of reactive oxygen species (ROS), as pretreatment with NAC (a ROS scavenger) and Apocynin (a Nox-2 inhibitor) blocked these events. Similarly, transient transfection of p47Phox or p91Phox siRNA attenuated artocarpin-induced NADPH oxidase activity and cell death. In addition, p53 dependent apoptotic proteins including PUMA, cytochrome c, Apaf-1 and caspase 3 were activated by artocarpin, and these effects can be abolished by antioxidants, MAPK inhibitors (U0126 and SB202190), but not by PI3K inhibitor (LY294002). Furthermore, we found that artocarpin-induced Akt phosphorylation led to increased NF-κB activity, which may act as an upstream regulator in the c-Myc and Noxa pathway. Therefore, we propose that enhancement of both ERK/ p38/ p53-dependent or independent AktS473/NF-κB/c-Myc/Noxa cascade by Nox-derived ROS generation plays an important role in artocarpin-induced apoptosis in NSCLC cells.

Gambogenic acid inhibits fibroblast growth factor receptor signaling pathway in erlotinib-resistant non-small-cell lung cancer and suppresses patient-derived xenograft growth

Erlotinib resistance causes a high degree of lethality in non-small-cell lung cancer (NSCLC) patients. The high expression and activation of several receptor tyrosine kinases, such as JAK/STAT3, c-Met, and EGFR, play important roles in drug resistance. The development of tyrosine kinase inhibitors is urgently required in the clinic. Our previous study found that Gambogenic acid (GNA), a small molecule derived from the traditional Chinese medicine herb gamboge, induced cell death in several NSCLC cell lines through JAK/STAT3 inhibition. In this study, we investigated the mechanism of action of GNA in erlotinib-resistant NSCLC and patient-derived cells. The inhibition of GNA on FGFR signaling pathway was examined using biochemical kinase assays. NSCLC cell lines (HCC827, HCC827-Erlotinib-resistant, and H1650) and primary cells from patients with NSCLC with clinical resistance to erlotinib were treated with GNA, erlotinib, or their combination. Both kinase assays and cell- based assays showed that GNA inhibits the phosphorylation of multiple kinases in FGFR signaling pathway in NSCLC. The combination of GNA and erlotinib significantly attenuates the tumor growth of HCC827 and erlotinib-resistant HCC827 xenografts with low toxicity. Importantly, GNA significantly suppresses tumor growth in a lung patient-derived xenograft (PDX) model with FGFR fusion and low EGFR expression. Our findings provide preclinical evidence for using GNA as an FGFR signaling pathway inhibitor to overcome erlotinib resistance in NSCLC treatment or to enhance erlotinib efficacy when used as a combined administration.

Co-delivery of gambogic acid and TRAIL plasmid by hyaluronic acid grafted PEI-PLGA nanoparticles for the treatment of triple negative breast cancer

Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL)-based combination therapy and gene therapy are new strategies to potentially overcome the limitations of TRAIL, however, the lack of efficient and low toxic vectors remains the major obstacle. In this study, we developed a hyaluronic acid (HA)-decorated polyethylenimine-poly(d,l-lactide-co-glycolide) (PEI-PLGA) nanoparticle (NP) system for targeted co-delivery of TRAIL plasmid (pTRAIL) and gambogic acid (GA) in triple-negative breast cancer (TNBC) therapy. GA was encapsulated into the core of the PEI-PLGA NPs while pTRAIL was adsorbed onto the positive NP surface via charge adsorption. The coating of HA on PEI-PLGA NPs functions as a targeting ligand by binding to CD44 receptor of TNBC cells and a shell to neutralize the excess positive charge of inner NPs. The resultant pTRAIL and GA co-loaded HA-coated PEI-PLGA NPs exhibited spherical shape (121.5 nm) and could promote the internalization of loaded cargoes into TNBC cells through the CD44-dependent endocytic pathway. The dual drug-loaded NPs significantly augmented apoptotic cell death in vitro and inhibited TNBC tumor growth in vivo. This multifunctional NP system efficiently co-delivered GA and pTRAIL, thus representing a promising strategy to treat TNBC and bringing forth a platform strategy for co-delivery of therapeutic DNA and chemotherapeutic agents in combinatorial TNBC therapy.

Targeting EHMT2 reverses EGFR-TKI resistance in NSCLC by epigenetically regulating the PTEN/AKT signaling pathway

Epidermal growth factor receptor tyrosine kinase inhibitor (EGFR-TKI) resistance is a major obstacle in the treatment of non-small cell lung cancer (NSCLC). Epigenetic alterations have been shown to be involved in NSCLC oncogenesis; however, their function in EGFR-TKI resistance remains uncharacterized. Here, we found that an EHMT2 inhibitor, UNC0638, can significantly inhibit cell growth and induce apoptosis in EGFR-TKI-resistant NSCLC cells. Additionally, we also found that EHMT2 expression and enzymatic activity levels were elevated in EGFR-TKI-resistant NSCLC cells. Moreover, we determined that genetic or pharmacological inhibition of EHMT2 expression enhanced TKI sensitivity and suppressed migration and tumor sphere formation in EGFR-TKI-resistant NSCLC cells. Further investigation revealed that EHMT2 contributed to PTEN transcriptional repression and thus facilitated AKT pathway activation. The negative relationship between EHMT2 and PTEN was confirmed by our clinical study. Furthermore, we determined that combination treatment with the EHMT2 inhibitor and Erlotinib resulted in enhanced antitumor effects in a preclinical EGFR-TKI-resistance model. We also found that high EHMT2 expression along with low PTEN expression can predict poor overall survival in patients with NSCLC. In summary, our findings showed that EHMT2 facilitated EGFR-TKI resistance by regulating the PTEN/AKT pathway in NSCLC cells, suggesting that EHMT2 may be a target in the clinical treatment of EGFR-TKI-resistant NSCLC.

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.

Melatonin increases the effect of 5-fluorouracil-based chemotherapy in human colorectal adenocarcinoma cells in vitro

Melatonin has antitumor activity via several mechanisms including its anti-proliferative and pro-apoptotic effects. Moreover, it has been proven that melatonin in combination with chemotherapeutic agents enhances chemotherapy-triggered apoptosis in several types of cancer. Therefore, this study was intended to evaluate whether melatonin is able to strengthen the anti-cancer potential of different chemotherapeutic drugs in human colorectal adenocarcinoma HT-29 cells. We found that treatment with 20 µM cisplatin (CIS) or 1 mM 5-fluorouracil (5-FU) for 72 h induced a decrease in HT-29 cell viability. Furthermore, 1 mM melatonin significantly (P < 0.05) increased the cytotoxic effects of 5-FU. Likewise, simultaneous stimulation with 1 mM melatonin and 1 mM 5-FU significantly (P < 0.05) enhanced the ratio of cells with an overproduction of intracellular reactive oxygen species and substantially augmented the population of apoptotic cells compared to the treatment with 5-FU alone. Nonetheless, melatonin only displayed moderate chemosensitizing effects in CIS-treated HT-29 cells, as suggested by a slight increment in the fraction of early apoptotic cells that was observed only after 48 h. Consistently, co-stimulation of HT-29 cells with 20 µM CIS or 1 mM 5-FU in the presence of 1 mM melatonin further increased caspase-3 activation. Apart from this, the cytostatic activity displayed by CIS due to S phase arrest was not affected by concomitant stimulation with melatonin. Overall, our results indicate that melatonin increases the sensitivity of HT-29 cells to 5-FU treatment and, consequently, the indolamine could be potentially applied to colorectal adenocarcinoma treatment as a potent chemosensitizing agent.

Gambogic acid sensitizes gemcitabine efficacy in pancreatic cancer by reducing the expression of ribonucleotide reductase subunit-M2 (RRM2)

Background

Pancreatic cancer is susceptible to gemcitabine resistance, and patients receive less benefit from gemcitabine chemotherapy. Previous studies report that gambogic acid possesses antineoplastic properties; however, to our knowledge, there have been no specific studies on its effects in pancreatic cancer. Therefore, the purpose of this study was to explore whether increases the sensitivity of pancreatic cancer to gemcitabine, and determine the synergistic effects of gambogic acid and gemcitabine against pancreatic cancer.

Methods

The effects of gambogic acid on cell viability, the cell cycle, and apoptosis were assessed using 4,5-dimethylthiazol-2-yl)-3,5-diphenylformazan (MTT) and flow cytometry in pancreatic cancer cell lines. Protein expression was detected by western blot analysis and mRNA expression was detected using q-PCR. A xenograft tumor model of pancreatic cancer was used to investigate the synergistic effects of gambogic acid and gemcitabine.

Results

Gambogic acid effectively inhibited the growth of pancreatic cancer cell lines by inducing S-phase cell cycle arrest and apoptosis. Synergistic activity of gambogic acid combined with gemcitabine was observed in PANC-1 and BxPC-3 cells based on the results of MTT, colony formation, and apoptosis assays. Western blot results demonstrated that gambogic acid sensitized gemcitabine-induced apoptosis by enhancing the expression of cleaved caspase-3, cleaved caspase-9, cleaved-PARP, and Bax, and reducing the expression of Bcl-2. In particular, gambogic acid reduced the expression of the ribonucleotide reductase subunit-M2 (RRM2) protein and mRNA, a trend that correlated with resistance to gemcitabine through inhibition of the extracellular signal-regulated kinase (ERK)/E2F1 signaling pathway. Treatment with gambogic acid and gemcitabine significantly repressed tumor growth in the xenograft pancreatic cancer model. Immunohistochemistry results demonstrated a downregulation of p-ERK, E2F1, and RRM2 in mice receiving gambogic acid treatment and combination treatment.

Conclusions

These results demonstrate that gambogic acid sensitizes pancreatic cancer cells to gemcitabine in vitro and in vivo by inhibiting the activation of the ERK/E2F1/RRM2 signaling pathway. The results also indicate that gambogic acid treatment combined with gemcitabine might be a promising chemotherapy strategy for pancreatic cancer.

Electronic supplementary material

The online version of this article (doi:10.1186/s13046-017-0579-0) contains supplementary material, which is available to authorized users.