Reversal effect of bufalin on multidrug resistance in human hepatocellular carcinoma BEL-7402/5-FU cells

Combinational Antitumor Strategies Based on the Active Ingredients of Toad Skin and Toad Venom

A multidrug combination strategy is an important mean to improve the treatment of cancer and is the mainstream scheme of clinical cancer treatment. The active ingredients of traditional Chinese medicine, represented by toad skin and toad venom, have the advantages of high efficiency, low toxicity, wide action and multiple targets and have become ideal targets in combined treatment strategies for tumors in recent years. Toad skin and toad venom are traditional Chinese animal medicines derived from Bufo bufo gargarizans Cantor or Bufo melanostictus Schneider that have shown excellent therapeutic effects on the treatment of various cancers and cancer pain as adjuvant antitumor drugs in clinical practice. The involved mechanisms include inducing apoptosis, arresting the cell cycle, inhibiting cell proliferation, migration and invasion, inhibiting tumor angiogenesis, reversing the multidrug resistance of tumor cells, and regulating multiple signaling pathways and targets. Moreover, a multidrug combination strategy based on a nanodelivery system can realize the precise loading of the active ingredients of toad skin or toad venom and other antitumor drugs and carry drugs to overcome physiological and pathological barriers, complete efficient enrichment in tumor tissues, and achieve targeted delivery to tumor cells and the controlled release of drugs, thus enhancing antitumor efficacy and reducing toxicity and side effects. This article reviewed the clinical efficacy and safety of the combination of toad skin and toad venom with chemotherapeutic drugs, targeted drugs, analgesics and other drugs; evaluated the effects and mechanisms of the combination of toad skin and toad venom with chemotherapy, targeted therapy, radiotherapy or hyperthermia, traditional Chinese medicine, signaling pathway inhibitors and other therapies in cell and animal models; and summarized the codelivery strategies for the active ingredients of toad skin and toad venom with chemotherapeutic drugs, small-molecule targeted drugs, monoclonal antibodies, active ingredients of traditional Chinese medicine, and photodynamic and photothermal therapeutic drugs to provide a basis for the rational drug use of toad skin and toad venom in the clinic and the development of novel drug delivery systems.

An overview of the past decade of bufalin in the treatment of refractory and drug-resistant cancers: current status, challenges, and future perspectives

Profound progress has been made in cancer treatment in the past three decades. However, drug resistance remains prevalent and a critical challenge. Drug resistance can be attributed to oncogenes mutations, activated defensive mechanisms, ATP-bind cassette transporters overexpression, cancer stem cells, etc. Chinese traditional medicine toad venom has been used for centuries for different diseases, including resistant cancers. Bufalin is one of the bufadienolides in toad venom that has been extensively studied for its potential in refractory and drug-resistant cancer treatments in vitro and in vivo. In this work, we would like to critically review the progress made in the past decade (2013-2022) of bufalin in overcoming drug resistance in cancers. Generally, bufalin shows high potential in killing certain refractory and resistant cancer cells via multiple mechanisms. More importantly, bufalin can work as a chemo-sensitizer that enhances the sensitivity of certain conventional and targeted therapies at low concentrations. In addition, the development of bufalin derivatives was also briefly summarized and discussed. We also analyzed the obstacles and challenges and provided possible solutions for future perspectives. We hope that the collective information may help evoke more effort for more in-depth studies and evaluation of bufalin in both lab and possible clinical trials.

Bufalin serves as a pharmaceutic that mitigates drug resistance

Intrinsic or acquired drug resistance of tumor cells is the main cause of tumor chemotherapy failure and tumor-related death. Bufalin (BF) is the main active monomer component extracted from the Traditional Chinese Medicine Toad venom (secretions of glands behind the ears and epidermis of bufo gargarizans and Bufo Melanostictus Schneider). It is a cardiotonic steroid with broad-spectrum anti-cancer effects and has been widely used against various malignant tumors in clinical practice. Pharmacological studies also found that BF has the effect of reversing drug resistance, which provides a new perspective for the application of Traditional Chinese Medicine as a chemosensitizer in cancer therapy. This article provides an extensive search and summary of published research on mitigating drug resistance to BF and reviews its potential mechanisms.

Bufalin reverses ABCB1-mediated resistance to docetaxel in breast cancer

Background

Docetaxel (DCT) is widely used in clinical practice, but the drug resistance of breast cancer patients has become an important reason to limit its clinical efficacy. Chan'su is a commonly used traditional Chinese medicine for the treatment of breast cancer. Bufalin (BUF) is a bioactive polyhydroxy steroid extracted from chan'su and has strong antitumor activity, but there are few studies on reversing drug resistance in breast cancer. The aim of this study is to determine whether BUF can reverse the drug resistance to DCT and restore efficacy in breast cancer.

Methodology

The reversal index of BUF was detected by Cell Counting Kit-8 (CCK-8) assays. The effects of BUF on enhancing the apoptosis of DCT were detected by flow cytometry and Western Blot (WB), and the main differential expression levels of sensitive and resistant strains were detected by high-throughput sequencing. Rhodamine 123 assay, WB and ATP Binding Cassette Subfamily B Member 1 (ABCB1) ATPase activity experiments were used to detect the effect of BUF on ABCB1. The nude mouse orthotopic model was constructed to investigate the reversal effect of BUF on DCT resistance in vivo.

Results

With BUF intervention, the sensitivity of drug-resistant cell lines to DCT was increased. BUF can inhibit the expression of ABCB1 protein, increase the drug accumulation of DCT in drug-resistant strains, and reduce the ATPase activity of ABCB1. Animal experiments show that BUF can inhibit the growth of drug-resistant tumors in an orthotopic model of breast cancer and decrease the expression of ABCB1.

Conclusion

BUF can reverse ABCB1-mediated docetaxel resistance in breast cancer.

Roles of conventional and complementary therapies in recurrent hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is the fifth most common type of cancer and the fourth leading cause of cancer-related deaths in the world. HCC has a reported recurrence rate of 70%-80% after 5 years of follow-up. Controlling tumor recurrence is the most critical factor associated with HCC mortality. Conventional salvage therapies for recurrent HCC include re-hepatectomy or liver transplantation, transcatheter arterial chemoembolization, Y-90, target therapy, and immunotherapy; however, these conventional treatment modalities have yet to achieve consistently favorable outcomes. Meanwhile, previous studies have demonstrated that conventional therapies in combination with traditional Chinese medicine (TCM), acupuncture, moxibustion or dietary supplements could notably benefit patients with HCC recurrence by strengthening and augmenting the overall management strategy. However, systemic reviews related to the interactions between complementary therapies and conventional therapy in recurrent HCC are limited. In this review, we discuss the molecular mechanisms underlying the functions of complementary therapies for recurrent HCC, which include augmenting the local control to improve the congestion status of primary tumors and reducing multicentric tumor occurrence via inducing autophagy, apoptosis or cell cycle arrest. TCM and its derivatives may play important roles in helping to control HCC recurrence by inhibiting epithelial-mesenchymal transition, migration, invasion, and metastasis, inhibiting cancer stem cells, and ameliorating drug resistance.

Exploring the potential targets of Sanshimao formula for hepatocellular carcinoma treatment by a method of network pharmacology combined with molecular biology

ETHNOPHARMACOLOGICAL RELEVANCE

The Sanshimao (SSM) formula is an effective prescription for hepatocellular carcinoma (HCC) therapy in the clinical setting. This prescription is made up of four herbals, Maorenshen, Shijianchuan, Shishangbai and Shidachuan, which are used for detoxification and removing blood stasis. However, its mechanism in the treatment of HCC remains ambiguous.

AIM OF THE STUDY

To explore the potential targets of SSM against HCC by network pharmacology analysis and verify the data using molecular biological methods.

MATERIALS AND METHODS

We screened active components and potential targets by data mining, constructed a network, and performed functional analysis and pathway enrichment to explore the therapeutic targets of SSM for HCC treatment. Then, the effects of SSM on HCC cells were studied to validate the data from network pharmacology analysis.

RESULTS

Eighty-eight common targets were obtained by mapping 932 HCC-related genes, and 325 targets corresponded to 11 active components of SSM. They were enriched in various biological processes, such as the response to inorganic substances, response to toxic substances and apoptotic signalling pathway, and multi-pathways involved pathways in cancer, EGFR tyrosine kinase inhibitor resistance, and AGE-RAGE signalling pathway in diabetic complications, as evaluated by the analysis of advanced functions and pathways. TP53, JUN, HSP90AA1, EGFR, AR and MAPK1 might be the core targets closely related to the effects of SSM on HCC according to PPI analysis. Treatment with SSM decreased cell viability and migration, promoted apoptosis and inhibited the EGFR/FAK/AKT signalling pathway.

CONCLUSION

This research preliminarily indicates that SSM treats HCC via multiple components and pathways. EGFR/FAK/AKT are promising therapeutic targets of SSM for HCC treatment. This provides objective evidence for further mechanistic research and the future development and clinical application of SSM in HCC patients.

Enhanced Cytotoxic Effects of Arenite in Combination with Active Bufadienolide Compounds against Human Glioblastoma Cell Line U-87

The cytotoxicity of a trivalent arsenic derivative (arsenite, As^III) combined with arenobufagin or gamabufotalin was evaluated in human U-87 glioblastoma cells. Synergistic cytotoxicity with upregulated intracellular arsenic levels was observed, when treated with As^III combined with arenobufagin instead of gamabufotalin. Apoptosis and the activation of caspase-9/-8/-3 were induced by As^III and further strengthened by arenobufagin. The magnitude of increase in the activities of caspase-9/-3 was much greater than that of caspase-8, suggesting that the intrinsic pathway played a much more important role in the apoptosis. An increase in the number of necrotic cells, enhanced LDH leakage, and intensified G₂/M phase arrest were observed. A remarkable increase in the expression level of γH2AX, a DNA damage marker, was induced by As^III+arenobufagin. Concomitantly, the activation of autophagy was observed, suggesting that autophagic cell death associated with DNA damage was partially attributed to the cytotoxicity of As^III+arenobufagin. Suppression of Notch signaling was confirmed in the combined regimen-treated cells, suggesting that inactivation of Jagged1/Notch signaling would probably contribute to the synergistic cytotoxic effect of As^III+arenobufagin. Given that both As^III and arenobufagin are capable of penetrating into the blood-brain barrier, our findings may provide fundamental insight into the clinical application of the combined regimen for glioblastoma.

Bufalin for an innovative therapeutic approach against cancer

Bufalin is an endogenous cardiotonic steroid, first discovered in toad venom but also found in the plasma of healthy humans, with anti-tumour activities in different cancer types. The current review is focused on its mechanisms of action and highlights its very large spectrum of effects both in vitro and in vivo. All leads to the conclusion that bufalin mediates its effects by affecting all the hallmarks of cancer and seems restricted to cancer cells avoiding side effects. Bufalin decreases cancer cell proliferation by acting on the cell cycle and inducing different mechanisms of cell death including apoptosis, necroptosis, autophagy and senescence. Bufalin also moderates metastasis formation by blocking migration and invasion as well as angiogenesis and by inducing a phenotype switch towards differentiation and decreasing cancer cell stemness. Regarding its various mechanisms of action in cancer cells, bufalin blocks overactivated signalling pathways and modifies cell metabolism. Moreover, bufalin gained lately a huge interest in the field of drug resistance by both reversing various drug resistance mechanisms and affecting the immune microenvironment. Together, these data support bufalin as a quite promising new anti-cancer drug candidate.

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.

Flower-like Composite Material Delivery of Co-Packaged Lenvatinib and Bufalin Prevents the Migration and Invasion of Cholangiocarcinoma

The co-delivery of multiple drugs using nanocarriers has been recognized as a promising strategy for cancer treatment to enhance therapeutic efficacy. In this study, a monodisperse mesoporous silica nanoparticle (mSiO₂) is prepared and functionalized into high-efficiency loaded Lenvatinib and Bufalin for targeted delivery to Cholangiocarcinoma (CCA). mSiO₂ was synthesized on solid silica nanoparticles by oil–water interface method, and highly monodisperse mSiO₂ with uniform morphology was obtained. mSiO₂ was then sequentially modified by polyethylene glycol (PEG) and the targeting molecule folic acid (FA). mSiO₂-FA was designed as co-delivery system for Lenvatinib (Le) and Bufalin (Bu) to increase drug availability and highly target tumor cells. Compared with unfunctionalized mSiO₂, mSiO₂-FA can more efficiently enter human CCA cell lines (9810 cells) and enhance intracellular drug delivery. Moreover, drug-loaded mSiO₂-FA (Le/Bu@mSiO₂-FA) significantly inhibited the viability, migration and invasion of 9810 cells. In vivo, the nanocomplex significantly reduced the tumor load in CCA tumor-bearing mouse models compared to Le or Bu alone. The current work provides a useful strategy for highly targeted and multidrug-resistance reversal therapy for CCA.

Bufalin enhances the killing efficacy of NK cells against hepatocellular carcinoma by inhibiting MICA shedding

Bufalin, as a Chinese traditional anti-tumor agent, has been studied about inhibiting proliferation and promoting apoptosis of liver cancer, however, there are few reports on immune modulating function. We used the human liver cancer cell lines along with 91 pathologically-verified postoperative hepatocellular carcinoma (HCC) specimens to assess immune modulating function of bufalin. We found that bufalin directly balances stimulatory and inhibitory receptors on the surface of NK cells and indirectly activates natural killer (NK) cells by inhibiting MICA shedding, which prevented immune escape and indirectly enhanced NKG2D-dependent immune surveillance. This study showed that bufalin can directly or indirectly regulate the immune response, which provides a new theoretical basis for the clinical application of "Huachansu injection".

Bufalin inhibits hepatitis B virus-associated hepatocellular carcinoma development through androgen receptor dephosphorylation and cell cycle-related kinase degradation

PURPOSE

Hepatitis B virus (HBV)-associated hepatocellular carcinoma (HCC), which has a male predominance, lacks effective therapeutic options. Previously, the cardiac glycoside analogue bufalin has been found to inhibit HBV infection and HCC development. As yet, however, its molecular role in HBV-associated HCC has remained obscure.

METHODS

Colony formation and soft agar assays, xenograft and orthotopic mouse models and HBV X protein (HBx) transgenic mice with exposure to diethylnitrosamine were used to evaluate the effect of bufalin on HBV-associated HCC growth and tumorigenicity. HBx-induced oncogenic signaling regulated by bufalin was assessed using PCR array, chromatin immunoprecipitation, site-directed mutagenesis, luciferase reporter, transcription and protein expression assays. Synergistic HCC therapeutic effects were examined using combinations of bufalin and sorafenib.

RESULTS

We found that bufalin exerted a more profound effect on inhibiting the proliferation of HBV-associated HCC cells than of non HBV-associated HCC cells. Bufalin significantly inhibited HBx-induced malignant transfromation in vitro and tumorigenicity in vivo. Androgen receptor (AR) signaling was found to be a target of bufalin resistance to HBV-associated hepatocarcinogenesis. We also found that bufalin induced both AR dephosphorylation and cell cycle-related kinase (CCRK) degradation to inhibit β-catenin/TCF signaling, which subsequently led to cell cycle arrest via cyclin D1 down-regulation and p21 up-regulation, resulting in HCC regression. Furthermore, we found that bufalin reduced > 60% diethylnitrosamine-induced hepatocarcinogenesis in HBx transgenic mice, and improved the sensitivity of refractory HBV-associated HCC cells to sorafenib treatment.

CONCLUSION

Our results indicate that bufalin acts as a potential anti-HCC therapeutic candidate to block HBx-induced AR/CCRK/β-catenin signaling by targeting AR and CCRK, which may provide a novel strategy for the treatment of HBV-associated HCC.

Molecular mechanisms of bufadienolides and their novel strategies for cancer treatment

Bufadienolides are cardioactive C24 steroids with an α-pyrone ring at position C17. In the last ten years, accumulating studies have revealed the anticancer activities of bufadienolides and their underlying mechanisms, such as induction of autophagy and apoptosis, cell cycle disruption, inhibition of angiogenesis, epithelial-mesenchymal transition (EMT) and stemness, and multidrug resistance reversal. As Na⁺/K⁺-ATPase inhibitors, bufadienolides have inevitable cardiotoxicity. Short half-lives, poor stability, low plasma concentration and oral bioavailability in vivo are obstacles for their applications as drugs. To improve the drug potency of bufadienolides and reduce their side effects, prodrug strategies and drug delivery systems such as liposomes and nanoparticles have been applied. Therefore, systematic and recapitulated information about the antitumor activity of bufadienolides, with special emphasis on the molecular or cellular mechanisms, prodrug strategies and drug delivery systems, is of high interest. Here, we systematically review the anticancer effects of bufadienolides and the molecular or cellular mechanisms of action. Research advancements regarding bufadienolide prodrugs and their tumor-targeting delivery strategies are critically summarized. This work highlights recent scientific advances regarding bufadienolides as effective anticancer agents from 2011 to 2019, which will help researchers to understand the molecular pathways involving bufadienolides, resulting in a selective and safe new lead compound or therapeutic strategy with improved therapeutic applications of bufadienolides for cancer therapy.

Bufalin reverses multidrug resistance by regulating stemness through the CD133/nuclear factor-κB/MDR1 pathway in colorectal cancer

Recent studies have shown that MDR could be induced by the high stemness of cancer cells. In a previous study, we found bufalin could reverse MDR and inhibit cancer cell stemness in colorectal cancer, but the relationship between them was unclear. Here we identified overexpressing CD133 increases levels of Akt/nuclear factor‐κB signaling mediators and MDR1, while increasing cell chemoresistance. Furthermore, bufalin reverses colorectal cancer MDR by regulating cancer cell stemness through the CD133/nuclear factor‐κB/MDR1 pathway in vitro and in vivo. Taken together, our results suggest that bufalin could be developed as a novel 2‐pronged drug that targets CD133 and MDR1 to eradicate MDR cells and could ultimately be combined with conventional chemotherapeutic agents to improve treatment outcomes for patients with colorectal cancer.

Spica Prunellae Extract Enhances Fluorouracil Sensitivity of 5-Fluorouracil-Resistant Human Colon Carcinoma HCT-8/5-FU Cells via TOP2α and miR-494

The use of 5-fluorouracil (5-FU) has been proven benefits, but it also has adverse events in colorectal cancer (CRC) chemotherapy. In this study, we explored the mechanism of 5-FU resistance by bioinformatics analysis of the NCBI public dataset series GSE81005. Fifteen hub genes were screened out of 582 different expressed genes. Modules of the hub genes in protein-protein interaction networks gathered to TOP2α showed a decrease in HCT-8 cells but an increase in 5-FU-resistant HCT-8/5-FU cells with 5-FU exposure. Downregulation of TOP2α with siRNA or miR-494 transfection resulted in an increase of cytotoxicity and decrease of cell colonies to 5-FU for HCT-8/5-FU cells. Moreover, we found that an ethanol extract of Spica Prunellae (EESP), which is a traditional Chinese medicine with clinically beneficial effects in various cancers, was able to enhance the sensitivity of 5-FU in HCT-8/5-FU cells and partly reverse the 5-FU resistance effect. It significantly helped suppress cell growth and induced cell apoptosis in HCT-8/5-FU cells with the expression of TOP2α being significantly suppressed, which increased by 5-FU. Consistently, miR-494, which reportedly regulates TOP2α, exhibited reverse trends in EESP/5-FU combination treatment. These results suggested that Spica Prunellae may be beneficial in the treatment of 5-FU-resistant CRC patients.

ABC Transporters: Regulation and Association with Multidrug Resistance in Hepatocellular Carcinoma and Colorectal Carcinoma

For most cancers, the treatment of choice is still chemotherapy despite its severe adverse effects, systemic toxicity and limited efficacy due to the development of multidrug resistance (MDR). MDR leads to chemotherapy failure generally associated with a decrease in drug concentration inside cancer cells, frequently due to the overexpression of ABC transporters such as P-glycoprotein (P-gp/MDR1/ABCB1), multidrug resistance-associated proteins (MRPs/ABCCs), and breast cancer resistance protein (BCRP/ABCG2), which limits the efficacy of chemotherapeutic drugs. The aim of this review is to compile information about transcriptional and post-transcriptional regulation of ABC transporters and discuss their role in mediating MDR in cancer cells. This review also focuses on drug resistance by ABC efflux transporters in cancer cells, particularly hepatocellular carcinoma (HCC) and colorectal carcinoma (CRC) cells. Some aspects of the chemotherapy failure and future directions to overcome this problem are also discussed.

New therapeutic aspects of steroidal cardiac glycosides: the anticancer properties of Huachansu and its main active constituent Bufalin

Aim of the review

In the past decade, increasing research attention investigated the novel therapeutic potential of steroidal cardiac glycosides in cancer treatment. Huachansu and its main active constituent Bufalin have been studied in vitro, in vivo and clinical studies. This review aims to summarize the multi-target and multi-pathway pharmacological effects of Bufalin and Huachansu in the last decade, with the aim of providing a more comprehensive view and highlighting the recently discovered molecular mechanisms.

Results

Huachansu and its major derivative, Bufalin, had been found to possess anti-cancer effects in a variety of cancer cell lines both in vitro and in vivo. The underlying anti-cancer molecular mechanisms mainly involved anti-proliferation, apoptosis induction, anti-metastasis, anti-angiogenesis, epithelial-mesenchymal transition inhibition, anti-inflammation, Na⁺/K⁺-ATPase activity targeting, the steroid receptor coactivator family inhibitions, etc. Moreover, the potential side-effects and toxicities of the toad extract, Huachansu, and Bufalin, including hematological, gastrointestinal, mucocutaneous and cardiovascular adverse reactions, were reported in animal studies and clinic trails.

Conclusions

Further research is needed to elucidate the potential drug-drug interactions and multi-target interaction of Bufalin and Huachansu. Large-scale clinical trials are warranted to translate the knowledge of the anticancer actions of Bufalin and Huachansu into clinical applications as effective and safe treatment options for cancer patients in the future.

Role of traditional Chinese medicine in the management of patients with hepatocellular carcinoma

Traditional Chinese Medicines (TCMs) have been employed for centuries in the treatment of patients with hepatocellular carcinoma (HCC). Previous reviews of this topic have focused on certain aspects of TCM treatment rather than an overall assessment of their value and mechanisms of action. Both the Chinese and English medical literatures were reviewed to identify where TCM might be of value in the treatment of HCC and the justification for such treatment. TCM treatment corrects the "internal disequilibriums" thought to be responsible for the development, growth, and spread of the tumor. It has also been used to manage symptoms associated with HCC and the adverse effects of chemo- and radiation-therapies. Recent research has documented the precise effects of TCM on tumor biology. There are also increasing efforts to identify which of the many components of TCM herbal remedies are primarily responsible for these beneficial effects. This review outlines the benefits of TCM treatment of HCC and the laboratory data describing their anti-tumor properties.

Modulatory effects of bufalin, an active ingredient from toad venom on voltage-gated sodium channels

Chan-su (toad venom) has been used as an analgesic agent in China from ancient to modern times. Bufalin, a non-peptide toxin extracted from toad venom, is considered as one of the analgesic components. The molecular mechanism underlying the anti-nociceptive effects of bufalin remains unclear so far. In this study, we investigated the pharmacological effects of bufalin on pain-related ion channels as well as animal models through patch clamping, calcium imaging and animal behavior observation. Using the whole-cell recording, bufalin caused remarkable suppressive effect on the peak currents of Nav channels (voltage gated sodium channels, VGSCs) of dorsal root ganglion neuroblastomas (ND7-23 cell) in a dose-dependent manner. Bufalin facilitated the voltage-dependent activation and induced a negative shift on the fast inactivation of VGSCs. The recovery kinetics of VGSCs were significantly slowed and the recovery proportion were reduced after administering bufalin. However, bufalin prompted no significant effect not only on Kv4.2, Kv4.3 and BK channels heterologously expressed in HEK293T cells, but also on the capsaicin and allyl isothiocyanate induced Ca²⁺ influx. What's more, bufalin could observably relieve formalin-induced spontaneous flinching and licking response as well as carrageenan-induced thermal and mechanical hyperalgesia in dose-dependent manner in agreement with the results of in vitro experiments. The present results imply that the remarkable anti-nociceptive effects produced by bufalin are probably ascribed to its specific regulation on Nav channels. Bufalin inhibits the Nav channels in a dose-dependent manner, which will provide references for the optimal dose selection of analgesia drugs.

Molecular bases of the poor response of liver cancer to chemotherapy

A characteristic shared by most frequent types of primary liver cancer, i.e., hepatocellular carcinoma (HCC) and cholangiocarcinoma (CCA) in adults, and in a lesser extent hepatoblastoma (HB) mainly in children, is their high refractoriness to chemotherapy. This is the result of synergic interactions among complex and diverse mechanisms of chemoresistance (MOC) in which more than 100 genes are involved. Pharmacological treatment, although it can be initially effective, frequently stimulates the expression of MOC genes, which results in the relapse of the tumor, usually with a more aggressive and less chemosensitive phenotype. Identification of the MOC genetic signature accounting for the "resistome" present at each moment of tumor life would prevent the administration of chemotherapeutic regimens without chance of success but still with noxious side effects for the patient. Moreover, a better description of cancer cells strength is required to develop novel strategies based on pharmacological, cellular or gene therapy to overcome liver cancer chemoresistance.

Bufalin reverses ABCB1-mediated drug resistance in colorectal cancer

Multidrug resistance (MDR), mainly mediated by ABCB1 transporter, is a major cause for chemotherapy failure. Bufalin (BU), an active component of the traditional Chinese medicine chan’su, has been reported to have antitumor effects on various types of cancer cells. The purpose of this present study was to investigate the reversal effect of BU on ABCB1-mediated multidrug resistance in colorectal cancer. BU at safe concentration (5, 10, 20 nM) could reverse chemosensitivity of ABCB1-overexpression HCT8/ADR, LoVo/ADR and HCT8/ABCB1 nearly back to their parental cells level. In addition, results from the drug accumulation studies revealed that BU was able to enhance intracellular accumulation of doxorubicin (DOX) and Rhodamine 123 (Rho-123) in a dose-dependent manner. Furthermore, Western blot assays showed that BU significantly inhibited the expression level of ABCB1 protein. Meanwhile, BU stimulated the ATPase activity of ABCB1, which suggested that BU might be a substrate of ABCB1. More interestingly, docking analysis predicted that BU could be docked into the large hydrophobic drug-binding cavity of human ABCB1. Importantly, BU remarkable increased the effect of DOX against the ABCB1 resistant HCT8/ADR colorectal cell xenografts in nude mice, without inducing any obvious toxicity. Overall, we concluded that BU efficiently reversed ABCB1-mediated MDR through not only inhibited the efflux function of ABCB1, but also down-regulate its protein expression, which might represent a potential and superior ABCB1 modulator in colorectal cancer.

Bufalin-loaded bovine serum albumin nanoparticles demonstrated improved anti-tumor activity against hepatocellular carcinoma: preparation, characterization, pharmacokinetics and tissue distribution

Objective

To prepare and evaluate the liver-targeted drug delivery system of Bufalin with higher liver uptake and stronger antitumor activity against hepatocellular carcinoma.

Methods

Bufalin-loaded bovine serum albumin nanoparticle was prepared by desolvation method, to investigate the in vitro release performance and to evaluate the pharmacokinetic and tissue distribution. The antitumor activity against hepatocellular carcinoma was evaluated in vitro and in vivo, respectively.

Results

The Bufalin-loaded bovine serum albumin nanoparticle with an average particle size of 125.1 nm exhibited a sustained release behavior in vitro. The half-life, blood plasma area under the curve and apparent volume of distribution of Bufalin-loaded bovine serum albumin nanoparticle were significantly higher than that of Bufalin, whereas the clearance rate was lower than Bufalin group. The uptake of liver for Bufalin-loaded bovine serum albumin nanoparticle was 352.045 ± 35.665 ng/g while for Bufalin was 164.465 ± 48.080 ng/g (P < 0.01) at 5 min. The uptake of tumor for Bufalin-loaded bovine serum albumin nanoparticle was significantly higher than that of Bufalin both at 5 min (50.169 ± 11.708 ng/g, 93.415±13.828 ng/g, P < 0.01) and 15 min (43.683 ± 11.499 ng/g, 64.219 ± 17.684 ng/g, P > 0.05). Bufalin-loaded bovine serum albumin nanoparticle and Bufalin have similar antitumor activity in vitro. The tumor inhibition effect of Bufalin-loaded bovine serum albumin nanoparticle was stronger than that of Bufalin alone in vivo.

Conclusion

Bufalin-loaded bovine serum albumin nanoparticle is a promising liver-targeted drug delivery system with higher liver uptake and stronger antitumor activity against hepatocellular carcinoma.

Bufalin enhances antitumor effect of paclitaxel on cervical tumorigenesis via inhibiting the integrin α2/β5/FAK signaling pathway

While Bufalin restrains primary tumorigenesis, the role of Bufalin in cervical cancer remains unclear. Here, we show that Bufalin can inhibit cervical cancer cell proliferation, block cell cycle in G2/M phase, induce cellular apoptosis and reduce cell metastasis through stimulation of p21^waf/cip1, p27^cip/kip, Bax and E-cadherin, and suppression of cyclin A, cyclin B1, CDK2, Bcl-2, Bcl-xl, MMP9 and SNAIL1. Further study suggests that Bufalin has no apparent damage to human normal cervical cells at the low concentration (<20nM), but increases the chemotherapeutic efficacy of paclitaxel. Mechanistic study reveals that Bufalin suppresses the integrin α2/FAK/AKT1/ GSK3β signaling. Finally, in vivo studies show that Bufalin blocks the Siha-induced xenograft tumor growth without detectable toxicity in the animals at the therapeutic doses, and the combination treatment of Bufalin and paclitaxel more efficiently inhibits xenograft tumor growth. Thus, Bufalin may be developed as a potential therapeutic agent to treat cervical cancer.

Reversal of multidrug resistance of hepatocellular carcinoma cells by metformin through inhibiting NF-κB gene transcription

AIM: To interfere with the activation of nuclear factor-κB (NF-κB) with metformin and explore its effect in reversing multidrug resistance (MDR) of hepatocellular carcinoma (HCC) cells.

METHODS: Expression of P-glycoprotein (P-gp) and NF-κB in human HepG2 or HepG2/adriamycin (ADM) cells treated with pCMV-NF-κB-small interference RNA (siRNA) with or without metformin, was analyzed by Western blot or fluorescence quantitative PCR. Cell viability was tested by CCK-8 assay. Cell cycle and apoptosis were measured by flow cytometry and Annexin-V-PE/7-AnnexinV apoptosis detection double staining assay, respectively.

RESULTS: P-gp overexpression in HepG2 and HepG2/ADM cells was closely related to mdr1 mRNA (3.310 ± 0.154) and NF-κB mRNA (2.580 ± 0.040) expression. NF-κB gene transcription was inhibited by specific siRNA with significant down-regulation of P-gp and enhanced HCC cell chemosensitivity to doxorubicin. After pretreatment with metformin, HepG2/ADM cells were sensitized to doxorubicin and P-gp was decreased through the NF-κB signaling pathway. The synergistic effect of metformin and NF-κB siRNA were found in HepG2/ADM cells with regard to proliferation inhibition, cell cycle arrest and inducing cell apoptosis.

CONCLUSION: Metformin via silencing NF-κB signaling could effectively reverse MDR of HCC cells by down-regulating MDR1/P-gp expression.

Bufalin Induces Mitochondria-Dependent Apoptosis in Pancreatic and Oral Cancer Cells by Downregulating hTERT Expression via Activation of the JNK/p38 Pathway

Bufalin, a digoxin-like active component of the traditional Chinese medicine Chan Su, exhibits potent antitumor activities in many human cancers. Bufalin induces mitochondria-dependent apoptosis in cancer cells, but the detailed molecular mechanisms are largely unknown. hTERT, the catalytic subunit of telomerase, protects against mitochondrial damage by binding to mitochondrial DNA and reducing mitochondrial ROS production. In the present study, we investigated the effects of bufalin on the cell viability, ROS production, DNA damage, and apoptosis of CAPAN-2 human pancreatic and CAL-27 human oral cancer cells. Bufalin reduced CAPAN-2 and CAL-27 cell viability with IC₅₀ values of 159.2 nM and 122.6 nM, respectively. The reduced cell viability was accompanied by increased ROS production, DNA damage, and apoptosis and decreased expression of hTERT. hTERT silencing in CAPAN-2 and CAL-27 cells by siRNA resulted in increased caspase-9/-3 cleavage and DNA damage and decreased cell viability. Collectively, these data suggest that bufalin downregulates hTERT to induce mitochondria-dependent apoptosis in CAPAN-2 and CAL-27 cells. Moreover, bufalin increased the phosphorylation of JNK and p38-MAPK in CAPAN-2 and CAL-27 cells, and blocking the JNK/p38-MAPK pathway using the JNK inhibitor SP600125 or the p38-MAPK inhibitor SB203580 reversed bufalin-induced hTERT downregulation. Thus, the JNK/p38 pathway is involved in bufalin-induced hTERT downregulation and subsequent induction of apoptosis by the mitochondrial pathway.

Bufalin induces apoptosis in the U‑2OS human osteosarcoma cell line via triggering the mitochondrial pathway

Bufalin has been shown to induce apoptosis in osteosarcoma cells; however, the underlying mechanism has not been elucidated. The purpose of the present study was to investigate whether mitochondria‑mediated signaling pathways trigger the process of apoptosis in the U‑2OS osteosarcoma cell line. Bufalin inhibited the proliferation and induced apoptosis in U‑2OS cells in a time- and dose‑dependent manner. Bufalin‑induced apoptosis was accompanied with a significant reduction of the mitochondrial membrane potential, release of mitochondrial cytochrome c into the cytosol, activation of caspase‑3, caspase‑9 and poly(adenosine diphosphate ribose) polymerase, as well as downregulation of B-cell lymphoma 2 (Bcl-2)/Bcl-2-associated X protein. Cyclosporin A, a specific inhibitor of the mitochondrial permeability transition pore, attenuated bufalin-induced apoptosis. In conclusion, the present study revealed that bufalin induced apoptosis in the U‑2OS human osteosarcoma cell line via triggering of the mitochondrial pathway.

The effect and mechanism of bufalin on regulating hepatocellular carcinoma cell invasion and metastasis via Wnt/β-catenin signaling pathway

Hepatocellular carcinoma (HCC) is a highly malignant tumor with an extremely poor prognosis. Our preliminary study indicated that bufalin could restrain the proliferation of human hepatoma BEL-7402 cells in a time- and dose-dependent manner. In the present study, the colony formation assay, the Transwell invasion assay, the western blot analysis and the immunofluorescence method were respectively used to investigate the effect and mechanism of bufalin against HCC cell invasion and metastasis. We found that: i) bufalin had significant inhibitory effect on the cell proliferation of BEL-7402 cells; ii) bufalin markedly inhibited the migration and invasion of BEL-7402 cells; iii) bufalin could suppress the phosphorylation of GSK-3β Ser9 site in BEL-7402 cells, decrease the expression of β-catenin, cyclin D1, metalloproteinases-7 (MMP-7) and cyclooxygenase-2 (COX-2) in the cytoplasm, and increase the expression of E-cadherin and β-catenin on the cell membrane; and iv) the expression of α-fetoprotein significantly decreased and the expression of albumin increased in BEL-7402 cells after bufalin was used. Our results indicate that: i) bufalin can regulate the expression of associated factors in Wnt/β-catenin signaling pathway of BEL-7402 cells through suppressing the phosphorylation of GSK-3β Ser9 site; ii) bufalin can strengthen intercellular E-cadherin/β-catenin complex to control epithelial-mesenchymal transition; and iii) bufalin can reverse the malignant phenotype and promote the differentiation and maturation by regulating the AFP and ALB expression in BEL-7402 cells. These are very important mechanisms of bufalin on the inhibition of the invasion and metastasis of HCC cells.

Bufalin Reverses Resistance to Sorafenib by Inhibiting Akt Activation in Hepatocellular Carcinoma: The Role of Endoplasmic Reticulum Stress

Sorafenib is the standard first-line therapeutic treatment for patients with advanced hepatocellular carcinoma (HCC), but its use is hampered by the development of drug resistance. The activation of Akt by sorafenib is thought to be responsible for this resistance. Bufalin is the major active ingredient of the traditional Chinese medicine Chan su, which inhibits Akt activation; therefore, Chan su is currently used in the clinic to treat cancer. The present study aimed to investigate the ability of bufalin to reverse both inherent and acquired resistance to sorafenib. Bufalin synergized with sorafenib to inhibit tumor cell proliferation and induce apoptosis. This effect was at least partially due to the ability of bufalin to inhibit Akt activation by sorafenib. Moreover, the ability of bufalin to inactivate Akt depended on endoplasmic reticulum (ER) stress mediated by inositol-requiring enzyme 1 (IRE1). Silencing IRE1 with siRNA blocked the bufalin-induced Akt inactivation, but silencing eukaryotic initiation factor 2 (eIF2) or C/EBP-homologous protein (CHOP) did not have the same effect. Additionally, silencing Akt did not influence IRE1, CHOP or phosphorylated eIF2α expression. Two sorafenib-resistant HCC cell lines, which were established from human HCC HepG2 and Huh7 cells, were refractory to sorafenib-induced growth inhibition but were sensitive to bufalin. Thus, Bufalin reversed acquired resistance to sorafenib by downregulating phosphorylated Akt in an ER-stress-dependent manner via the IRE1 pathway. These findings warrant further studies to examine the utility of bufalin alone or in combination with sorafenib as a first- or second-line treatment after sorafenib failure for advanced HCC.

Design real-time reversal of tumor multidrug resistance cleverly with shortened carbon nanotubes

Multidrug resistance (MDR) in tumors renders many currently available chemotherapeutic drugs ineffective. Research in nanobiotechnology-based therapeutic alternatives has provided innovative and promising strategies to overcome MDR. The aim of this study was to investigate whether the new strategy of a co-loaded reversal agent and chemotherapeutic drug with shortened carbon nanotubes (CNTs) would show useful effects on the real-time reversal of tumor MDR. CNTs were cut and purified via ultrasonication and oxidative acid treatment to optimize their length for drug-delivery vehicles, then verapamil (Ver) and doxorubicin (Dox) were co-loaded on shortened CNTs (denoted as Ver/Dox/shortened CNTs), which acted as a drug delivery system. The multidrug resistant leukemia K562/A02 cells were treated with the denoted Ver/Dox/shortened CNTs. The real-time reversal of tumor MDR were evaluated by flow cytometer, 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assays, acridine orange/ethidium bromide staining, and Western blot analysis. In the same MDR tumor cells the new strategy of a co-loaded reversal agent and chemotherapeutic drug with CNTs could inhibit the function of P-glycoprotein in real-time by Ver as reversal agent, significantly increase the uptake of Dox, enhance the sensitivity of the MDR cancer cells to the chemotherapeutic agent, and induce apoptosis. It was therefore concluded that a co-loaded reversal agent and chemotherapeutic drug with shortened CNTs could have real-time reversal ability of MDR in tumors, which could represent a promising approach in cancer therapy.