Bufalin inhibits glioblastoma growth by promoting proteasomal degradation of the Na+/K+-ATPase α1 subunit

Ferroptosis and the ubiquitin-proteasome system: exploring treatment targets in cancer

Ferroptosis is an emerging mode of programmed cell death fueled by iron buildup and lipid peroxidation. Recent evidence points to the function of ferroptosis in the aetiology and development of cancer and other disorders. Consequently, harnessing iron death for disease treatment has diverted the interest of the researchers in the field of basic and clinical research. The ubiquitin-proteasome system (UPS) represents a primary protein degradation pathway in eukaryotes. It involves labelling proteins to be degraded by ubiquitin (Ub), followed by recognition and degradation by the proteasome. Dysfunction of the UPS can contribute to diverse pathological processes, emphasizing the importance of maintaining organismal homeostasis. The regulation of protein stability is a critical component of the intricate molecular mechanism underlying iron death. Moreover, the intricate involvement of the UPS in regulating iron death-related molecules and signaling pathways, providing valuable insights for targeted treatment strategies. Besides, it highlights the potential of ferroptosis as a promising target for cancer therapy, emphasizing the combination between ferroptosis and the UPS. The molecular mechanisms underlying ferroptosis, including key regulators such as glutathione peroxidase 4 (GPX4), cysteine/glutamate transporter (system XC-), and iron metabolism, are thoroughly examined, alongside the role of the UPS in modulating the abundance and activity of crucial proteins for ferroptotic cell death, such as GPX4, and nuclear factor erythroid 2-related factor 2 (NRF2). As a pivotal regulatory system for macromolecular homeostasis, the UPS substantially impacts ferroptosis by directly or indirectly modulating iron death-related molecules or associated signaling pathways. This review explores the involvement of the UPS in regulating iron death-related molecules and signaling pathways, providing valuable insights for the targeted treatment of diseases associated with ferroptosis.

ATP1A1 is a promising new target for melanoma treatment and can be inhibited by its physiological ligand bufalin to restore targeted therapy efficacy

Despite advancements in treating metastatic melanoma, many patients exhibit resistance to targeted therapies. Our study focuses on ATP1A1, a sodium pump subunit associated with cancer development. We aimed to assess ATP1A1 prognostic value in melanoma patients and examine the impact of its ligand, bufalin, on melanoma cell lines in vitro and in vivo. High ATP1A1 expression (IHC) correlated with reduced overall survival in melanoma patients. Resistance to BRAF inhibitor was linked to elevated ATP1A1 levels in patient biopsies (IHC, qPCR) and cell lines (Western blot, qPCR). Additionally, high ATP1A1 mRNA expression positively correlated with differentiation/pigmentation markers based on data from The Cancer Genome Atlas (TCGA) databases and Verfaillie proliferative gene signature analysis. Bufalin specifically targeted ATP1A1 in caveolae, (proximity ligation assay) and influenced Src phosphorylation (Western blot), thereby disrupting multiple signaling pathways (phosphokinase array). In vitro, bufalin induced apoptosis in melanoma cell lines by acting on ATP1A1 (siRNA experiments) and, in vivo, significantly impeded melanoma growth using a nude mouse xenograft model with continuous bufalin delivery via an osmotic pump. In conclusion, our study demonstrates that ATP1A1 could serve as a prognostic marker for patient survival and a predictive marker for response to BRAF inhibitor therapy. By targeting ATP1A1, bufalin inhibited cell proliferation, induced apoptosis in vitro, and effectively suppressed tumor development in mice. Thus, our findings strongly support ATP1A1 as a promising therapeutic target, with bufalin as a potential agent to disrupt its tumor-promoting activity.

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 targeting BFAR inhibits the occurrence and metastasis of gastric cancer through PI3K/AKT/mTOR signal pathway

Gastric cancer (GC) is the most common malignant tumor of digestive system. Bufalin extracted from Venenum Bufonis is one of the most effective anticancer monomers, which has been proved to play anticancer roles in a variety of cancers such as ovarian cancer, prostate cancer and neuroblastoma. However, there are few studies on bufalin in GC, and lack of clear targets. The effect of bufalin on the proliferation and migration of GC cells was detected by CCK-8, scratch wound healing assay, transwell assay and Western blotting. The potential direct interaction proteins of bufalin were screened by human proteome microarray containing 21,838 human proteins. The target protein was determined by bioinformatics, and the binding sites were predicted by molecular docking technique. Biological experiments in vitro and in vivo were conducted to verify the effect of bufalin directly interaction protein and the mechanism of bufalin targeting the protein to inhibit the development of GC. The results showed that bufalin inhibited the proliferation and migration of MKN-45 and HGC-27 GC cell lines in vitro. BFAR, a direct interaction protein of bufalin has several potential binding sites to bufalin. BFAR is highly expressed in GC and promotes the occurrence and metastasis of GC by activating PI3K/AKT/mTOR signal pathway in vitro and in vivo. Bufalin reversed the promoting effect of BFAR on the carcinogenesis and metastasis of GC by down-regulating the expression of BFAR. Our results show that bufalin targeting BFAR inhibits the occurrence and metastasis of GC through PI3K/AKT/mTOR signal pathway. These results provide a new basis for bufalin as a promising drug for the treatment of GC.

Identification of Na+/K+-ATPase Inhibitor Bufalin as a Novel Pseudorabies Virus Infection Inhibitor In Vitro and In Vivo

Pseudorabies virus (PRV), an alpha herpesvirus, induces significant economic losses to the swine industry and infects multiple kinds of animals. Therefore, it is of great importance to explore anti-PRV compounds. In this study, to explore the anti-PRV compounds, a library of natural compounds was screened through a cell-based ELISA assay, and it was discovered that bufalin, a Na+/K+-ATPase inhibitor, had a robust inhibitory effect on PRV replication. A time-of-addition experiment and temperature-shift assay showed that bufalin significantly inhibited the entry stage of PRV. NaCl- or KCl-treatment showed that NaCl could enhance the inhibitory effect of bufalin on PRV replication, whereas there was no significant effect under the treatment of KCl. Meanwhile, it was also found that bufalin possessed antiviral activity against other alpha herpesviruses, including human herpes simplex virus type 1 (HSV-1) and chicken Marek's disease virus (MDV). Finally, it was found that bufalin could decrease the viral load in multiple tissues, and reduce the morbidity and mortality in PRV-challenged BALB/c mice. Overall, our findings demonstrated that bufalin has the potential to be developed as an anti-PRV compound.

Bufalin-Mediated Regulation of Cell Signaling Pathways in Different Cancers: Spotlight on JAK/STAT, Wnt/β-Catenin, mTOR, TRAIL/TRAIL-R, and Non-Coding RNAs

The renaissance of research into natural products has unequivocally and paradigmatically shifted our knowledge about the significant role of natural products in cancer chemoprevention. Bufalin is a pharmacologically active molecule isolated from the skin of the toad Bufo gargarizans or Bufo melanostictus. Bufalin has characteristically unique properties to regulate multiple molecular targets and can be used to harness multi-targeted therapeutic regimes against different cancers. There is burgeoning evidence related to functional roles of signaling cascades in carcinogenesis and metastasis. Bufalin has been reported to regulate pleiotropically a myriad of signal transduction cascades in various cancers. Importantly, bufalin mechanistically regulated JAK/STAT, Wnt/β-Catenin, mTOR, TRAIL/TRAIL-R, EGFR, and c-MET pathways. Furthermore, bufalin-mediated modulation of non-coding RNAs in different cancers has also started to gain tremendous momentum. Similarly, bufalin-mediated targeting of tumor microenvironments and tumor macrophages is an area of exciting research and we have only started to scratch the surface of the complicated nature of molecular oncology. Cell culture studies and animal models provide proof-of-concept for the impetus role of bufalin in the inhibition of carcinogenesis and metastasis. Bufalin-related clinical studies are insufficient and interdisciplinary researchers require detailed analysis of the existing knowledge gaps.

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.

Resibufogenin Targets the ATP1A1 Signaling Cascade to Induce G2/M Phase Arrest and Inhibit Invasion in Glioma

Resibufogenin (RB) is a major active ingredient in the traditional Chinese medicine Chansu and has garnered considerable attention for its efficacy in the treatment of cancer. However, the anticancer effects and underlying mechanisms of RB on glioblastoma (GBM) remain unknown. Here, we found that RB induced G2/M phase arrest and inhibited invasion in a primary GBM cell line, P3#GBM, and two GBM cell lines, U251 and A172. Subsequently, we demonstrated that RB-induced G2/M phase arrest occurred through downregulation of CDC25C and upregulation of p21, which was caused by activation of the MAPK/ERK pathway, and that RB inhibited GBM invasion by elevating intercellular Ca²⁺ to suppress the Src/FAK/Paxillin focal adhesion pathway. Intriguingly, we confirmed that upon RB binding to ATP1A1, Na⁺-K⁺-ATPase was activated as a receptor and then triggered the intracellular MAPK/ERK pathway and Ca²⁺-mediated Src/FAK/Paxillin focal adhesion pathway, which led to G2/M phase arrest and inhibited the invasion of GBM cells. Taken together, our findings reveal the antitumor mechanism of RB by targeting the ATP1A1 signaling cascade and two key signaling pathways and highlight the potential of RB as a new class of promising anticancer agents.

Novel Strategies for Solubility and Bioavailability Enhancement of Bufadienolides

Toad venom contains a large number of bufadienolides, which have a variety of pharmacological activities, including antitumor, cardiovascular, anti-inflammatory, analgesic and immunomodulatory effects. The strong antitumor effect of bufadienolides has attracted considerable attention in recent years, but the clinical application of bufadienolides is limited due to their low solubility and poor bioavailability. In order to overcome these shortcomings, many strategies have been explored, such as structural modification, solid dispersion, cyclodextrin inclusion, microemulsion and nanodrug delivery systems, etc. In this review, we have tried to summarize the pharmacological activities and structure-activity relationship of bufadienolides. Furthermore, the strategies for solubility and bioavailability enhancement of bufadienolides also are discussed. This review can provide a basis for further study on bufadienolides.

Chansu improves the respiratory function of severe COVID-19 patients

Targeted therapeutics for SARS-CoV-2 virus caused COVID-19 are in urgent need. Chansu has been reported to have broad-spectrum antiviral effects and widely used in Southeast Asian countries. This study aims to assess the efficacy of Chansu injection in treating patients with severe COVID-19. A randomized preliminary clinical trial was conducted and eligible patients were allocated to receive general treatment plus Chansu injection or only general treatment as control for 7 days. The primary outcomes of the oxygenation index PaO₂/FiO₂ and ROX, secondary outcomes of white blood cell count, respiratory support step-down time (RSST), safety indicators, etc were monitored. After 7 days of treatment, the oxygenation index was improved in 95.2% patients in the treatment group compared with 68.4% in the control group. The PaO₂/FiO₂ and ROX indices in the treatment group (mean, 226.27±67.35 and 14.01±3.99 respectively) were significantly higher than the control group (mean, 143.23±51.29 and 9.64±5.54 respectively). The RSST was 1 day shorter in the treatment group. Multivariate regression analysis suggested that Chansu injection contributed the most to the outcome of PaO₂/FiO₂. No obvious adverse effects were observed. The preliminary data showed that Chansu injection had apparent efficacy in improving the respiratory function of patients with severe COVID-19.

Natural products are an important source for proteasome regulating agents

BACKGROUND

Natural medicines have a long history in the prevention and treatment of various diseases in East Asian region, especially in China. Modern research has proved that the pharmacological effects of numerous natural medicines involve the participation of ubiquitin proteasome system (UPS). UPS can degrade the unwanted and damaged proteins widely distributed in the nucleus and cytoplasm of various eukaryotes.

PURPOSE

The objective of the present study was to review and discuss the regulatory effects of natural products and extracts on proteasome components, which may help to find new proteasome regulators for drug development and clinical applications.

METHODS

The related information was compiled using the major scientific databases, such as CNKI, Elsevier, ScienceDirect, PubMed, SpringerLink, Wiley Online, and GeenMedical. The keywords "natural product" and "proteasome" were applied to extract the literature. Nature derived extracts, compounds and their derivatives involved in proteasome regulation were included, and the publications related to synthetic proteasome agents were excluded.

RESULTS

The pharmacological effects of more than 80 natural products and extracts derived from phytomedicines related to the proteasome regulation were reviewed. These natural products were classified according to their chemical properties. We also summarized some laws of action of natural products as proteasome regulators in the treatment of diseases, and listed the action characteristics of the typical natural products.

CONCLUSION

Natural products derived from nature can induce the degradation of damaged proteins through UPS or act as regulators to directly regulate the activity of proteasome. But few proteasome modulators are applied clinically. Summary of known rules for proteasome modulators will contribute to discover, modify and synthesize more proteasome modulators for clinical applications.

Bufalin Induces Programmed Necroptosis in Triple-Negative Breast Cancer Drug-Resistant Cell Lines through RIP1/ROS-Mediated Pathway

OBJECTIVE

To explore the effect and mechanism of action of bufalin in triple-negative breast cancer (TNBC) drug-resistant cell lines.

METHODS

The normal human mammary epithelial cell line, TNBC cell line, TNBC adriamycin-resistant cell line, and TNBC docetaxel-resistant cell line were treated with different doses of bufalin (0-1,000 nmol/L) at different time points (0-72 h). Propidium iodide staining, AV-FITC/PI double staining, Hoechst 33342/PI double staining and transmission electron microscopy (TEM) were used to evaluate the death patterns of the cell lines.

RESULTS

Bufalin killed the TNBC cell line and its drug-resistant cell lines in a dose/time-dependent manner (all P<0.01). After treatment with bufalin for 24 h, the adriamycin-resistant cell line showed a co-existing pattern of necroptosis and apoptosis. However, at 48 h, necroptosis was the main manifestation. After treatment with bufalin, the expressions of tumor necrosis factor α, phospho-tumor necrosis factor receptor 1, phospho-receptor interacting protein 1 and c-caspase 3 increased (all P<0.01), the killing effect of bufalin could be mostly inhibited by NEC-1, and by z-VAD-fmk (both P<0.01). Besides, the intracellular reactive oxygen species (ROS) levels increased considerably (P<0.01), the antioxidant N-acetyl cysteine or Nec-1 could inhibit the increase of ROS level and the killing effect of bufalin (all P<0.01). The adriamycin-resistant cell line exhibited necroptosis characteristic after 48 h of bufalin treatment under TEM.

CONCLUSIONS

Bufalin could induce necroptosis through RIP1/ROS-mediated pathway to kill the drug-resistant TNBC cell lines. This finding provides critical experimental data and theoretical basis for the clinical application of bufalin to overcome the difficulties in the treatment of TNBC.

19-Hydroxybufalin inhibits non-small cell lung cancer cell proliferation and promotes cell apoptosis via the Wnt/β-catenin pathway

Background

Bufadienolides derived from the skin of toads are often regarded as the main active components with antitumor effects. 19-Hydroxybufalin (19-HB) is a monomer of bufadienolides; however, its effects and underlying molecular mechanisms on tumor growth remain to be ascertained. In this report, we focused on the antitumor effects of 19-HB on non-small cell lung cancer to provide a scientific basis for its further development and utilization.

Methods

The antitumor effects of 19-HB on the human NSCLC cell lines NCI-H1299 and NCI-H838 were examined in vitro. The cells were treated with different concentrations of 19-HB, and the inhibition of cell growth was measured by CCK-8 and colony formation assays. Furthermore, cell apoptosis was analyzed by flow cytometry, TUNEL staining, JC-1 staining, and western blotting. The effects on migration and invasion were evaluated by wound-healing assay, transwell assay, and western blotting. Finally, the antitumor effects of 19-HB were evaluated in vivo using a xenograft mouse model.

Results

19-HB-treated NSCLC cells showed inhibited cell viability and increased apoptosis. The expression levels of cleaved caspase-3, cleaved-PARP, and Bax/Bcl-2 were upregulated, while the mitochondrial membrane potential decreased. In contrast, migration, invasion, as well as the expression of MMP2, MMP7, MMP9, the epithelial–mesenchymal transition-related proteins N-cadherin and Vimentin, and the transcription factors Snail and Slug were inhibited. Furthermore, the expression levels of the key molecules in the Wnt/β-catenin signaling pathway (CyclinD1, c-Myc, and β-catenin) were decreased. In vivo, the growth of xenograft tumors in nude mice was also significantly inhibited by 19-HB, and there were no significant changes in biochemical indicators of hepatic and renal function.

Conclusions

19-HB inhibited the proliferation, migration, and invasion, and promoted the apoptosis of NSCLC cells via the Wnt/β-catenin pathway. In addition, 19-HB inhibited the growth of xenograft tumors in nude mice with little toxicity to the liver and kidney. Thus, 19-HB may be a potential antitumor agent for treating NSCLC.

Supplementary Information

The online version contains supplementary material available at 10.1186/s40164-021-00243-0.

The Role of the Ubiquitin Proteasome System in Glioma: Analysis Emphasizing the Main Molecular Players and Therapeutic Strategies Identified in Glioblastoma Multiforme

Gliomas constitute the most frequent tumors of the brain. High-grade gliomas are characterized by a poor prognosis caused by a set of attributes making treatment difficult, such as heterogeneity and cell infiltration. Additionally, there is a subgroup of glioma cells with properties similar to those of stem cells responsible for tumor recurrence after treatment. Since proteasomal degradation regulates multiple cellular processes, any mutation causing disturbances in the function or expression of its elements can lead to various disorders such as cancer. Several studies have focused on protein degradation modulation as a mechanism of glioma control. The ubiquitin proteasome system is the main mechanism of cellular proteolysis that regulates different events, intervening in pathological processes with exacerbating or suppressive effects on diseases. This review analyzes the role of proteasomal degradation in gliomas, emphasizing the elements of this system that modulate different cellular mechanisms in tumors and discussing the potential of distinct compounds controlling brain tumorigenesis through the proteasomal pathway.

Cytotoxic Effects of Arsenite in Combination With Gamabufotalin Against Human Glioblastoma Cell Lines

Glioblastoma is a fatal primary malignant brain tumor, and the 5-year survival rate of treated glioblastoma patients still remains <5%. Considering the sustained development of metastasis, tumor recurrence, and drug resistance, there is an urgent need for the novel therapeutic approaches to combat glioblastoma. Trivalent arsenic derivative (arsenite, As^III) with remarkable clinical efficacy in leukemia has been shown to exert cytocidal effect against glioblastoma cells. Gamabufotalin, an active bufadienolide compound, also shows selective cytocidal effect against glioblastoma cells, and has been suggested to serve as a promising adjuvant therapeutic agent to potentiate therapeutic effect of conventional anticancer drugs. In order to gain novel insight into therapeutic approaches against glioblastoma, the cytotoxicity of As^III and gamabufotalin was explored in the human glioblastoma cell lines U-87 and U-251. In comparison with U-251 cells, U-87 cells were highly susceptible to the two drugs, alone or in combination. More importantly, clinically achieved concentrations of As^III combined with gamabufotalin exhibited synergistic cytotoxicity against U-87 cells, whereas showed much less cytotoxicity to human normal peripheral blood mononuclear cells. G₂/M cell cycle arrest was induced by each single drug, and further augmented by their combination in U-87 cells. Downregulation of the expression levels of cdc25C, Cyclin B1, cdc2, and survivin was observed in U-87 cells treated with the combined regimen and occurred in parallel with G₂/M arrest. Concomitantly, lactate dehydrogenase leakage was also observed. Intriguingly, SB203580, a specific inhibitor of p38 MAPK, intensified the cytotoxicity of the combined regimen in U-87 cells, whereas wortmannin, a potent autophagy inhibitor, significantly rescued the cells. Collectively, G₂/M arrest, necrosis and autophagy appeared to cooperatively contribute to the synergistic cytotoxicity of As^III and gamabufotalin. Given that p38 MAPK serves an essential role in promoting glioblastoma cell survival, developing a possible strategy composed of As^III, gamabufotalin, and a p38 MAPK inhibitor may provide novel insight into approaches designed to combat glioblastoma.

Integrated network pharmacology and molecular docking approaches to reveal the synergistic mechanism of multiple components in Venenum Bufonis for ameliorating heart failure

Venenum Bufonis (VB), also called Chan Su in China, has been extensively used as a traditional Chinese medicine (TCM) for treating heart failure (HF) since ancient time. However, the active components and the potential anti-HF mechanism of VB remain unclear. In the current study, the major absorbed components and metabolites of VB after oral administration in rats were first collected from literatures. A total of 17 prototypes and 25 metabolites were gathered. Next, a feasible network-based pharmacological approach was developed and employed to explore the therapeutic mechanism of VB on HF based on the collected constituents. In total, 158 main targets were screened out and considered as effective players in ameliorating HF. Then, the VB components-main HF putative targets-main pathways network was established, clarifying the underlying biological process of VB on HF. More importantly, the main hubs were found to be highly enriched in adrenergic signalling in cardio-myocytes. After verified by molecular docking studies, four key targets (ATP1A1, GNAS, MAPK1 and PRKCA) and three potential active leading compounds (bufotalin, cinobufaginol and 19-oxo-bufalin) were identified, which may play critical roles in cardiac muscle contraction. This study demonstrated that the integrated strategy based on network pharmacology and molecular docking was helpful to uncover the synergistic mechanism of multiple constituents in TCM.

Bufalin exerts antitumor effects in neuroblastoma via the induction of reactive oxygen species‑mediated apoptosis by targeting the electron transport chain

The prognosis of high-risk neuroblastoma remains poor. Clinical first-line drugs for treating neuroblastoma have been developed over the previous half-century; however, progress in the identification of new drugs with high efficiency is required. Bufalin, one of the major components of extracts obtained from the venom of the Chinese toad Bufo gargarizans, which is used to treat heart failure in Asian Pacific countries, has been reported to be a potential drug against multiple types of tumor; however, the detailed mechanisms underlying its antitumor activities remain unclear, largely due to lack of knowledge regarding its targets. In the present study, bufalin was revealed to exhibit potent antitumor effects against neuroblastoma, both in vitro and in vivo, using cell proliferation, colony formation, Transwell migration and flow cytometry assays, as well as a nude mouse subcutaneous xenograft model. Moreover, a chemically modified bufalin probe was designed to identify the potential targets of bufalin in neuroblastoma via chemical proteomics. With this strategy, it was revealed that the electron transport chain (ETC) on the inner membrane of mitochondria may contain potential targets for bufalin, and that bufalin-induced mitochondrial-dependent apoptosis may be caused by disruption of the ETC. Collectively, the present study suggests that bufalin may a promising drug for chemotherapy against neuroblastoma, and provides a foundation for further studies into the antitumor mechanisms of bufalin.

Bufalin-Loaded PEGylated Liposomes: Antitumor Efficacy, Acute Toxicity, and Tissue Distribution

Bufalin, derived from Venenum Bufonis, exerts antitumor effects but has low bioavailability and adverse effects when administered as a single agent. The purpose of this study was to evaluate the physical and chemical properties, antitumor efficacy, general pharmacology, acute toxicity, and tissue distribution profile of bufalin-loaded PEGylated liposomes (BF/PEG-LP), which were prepared in a previous study. To evaluate the safety of the preparation, a red blood cell hemolysis test was performed, which indicated that the hemolysis rate of BF/PEG-LP was significantly lower than that of bufalin alone. Cell viability assay revealed that the blank liposomes were nontoxic. In an in vitro experiment, BF/PEG-LP dose-dependently induced the apoptosis of HepG2, HCT116, A549, and U251 cancer cells, with half-maximal inhibitory concentration (IC₅₀) values of 21.40 ± 2.39, 21.00 ± 3.34, 43.39 ± 6.43, and 31.14 ± 2.58 ng/mL, respectively, at 24 h. Tumor xenograft experiments in nude mice showed that BF/PEG-LP significantly inhibited the growth of U251 cells. Pharmacological evaluation revealed that BF/PEG-LP impacted the general behavior, independent activities, and coordination of mice after a week of administration compared with those of mice in the control group. In an acute toxicity test, the median lethal concentration (LD₅₀) of BF and BF/PEG-LP in mice was 0.156 and 3.03 mg/kg, respectively. Tissue distribution profiles showed that the BF concentration in brain tissue was 20% higher, whereas that in heart tissue was 30% lower when BF/PEG-LP was administered to mice compared with BF. Thus, BF/PEG-LP exhibited lower hemolysis and cytotoxicity and improved pharmacokinetic and antitumor properties compared with bufalin alone, indicating its potential for future pharmacological application, particularly for glioma treatment.

ATP1A1 Integrates AKT and ERK Signaling via Potential Interaction With Src to Promote Growth and Survival in Glioma Stem Cells

Glioma stem cells (GSCs) have been considered to be responsible for treatment failure due to their self-renewal and limitless proliferative property. Recently, the Na⁺/K⁺-ATPase a1 (ATP1A1) subunit was described as a novel therapeutic target for gliomas. Interestingly, our previous proteomics study revealed that ATP1A1 is remarkably overexpressed in GSCs. In the current study, we investigated the role of ATP1A1 in regulating growth, survival, and tumorigenicity of primary human GSCs and the underlying molecular mechanism. We tested RNA and protein expression of ATP1A1 in glioma tissues and GSCs. In addition, we knocked down ATP1A1 in GSCs and assessed the effects thereof on growth, survival, and apoptosis. The role of ATP1A1 in signaling pathways was investigated in vitro. We found that the ATP1A1 expression level was associated with the grade of glioma. Knockdown of ATP1A1 in GSCs in vitro inhibited cell proliferation and survival, increased apoptosis, and halted cell-cycle progression at the G1 phase. Cell proliferation and survival were resumed upon rescue of ATP1A1 expression in ATP1A1-knockdown GSCs. The ERK1/2 and AKT pathways were inhibited through suppression of Src phosphorylation by ATP1A1 knockdown. Collectively, our findings suggest that ATP1A1 overexpression promotes GSC growth and proliferation by affecting Src phosphorylation to activate the ERK1/2 and AKT signaling pathways.

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.

A research update on the anticancer effects of bufalin and its derivatives

Bufalin (BF) is a cardiotonic steroid that has recently been found to have substantial anticancer activity; however, more efforts should be directed toward clarifying the detailed molecular mechanisms underlying this activity. BF could exert its anticancer effect by inducing apoptosis in various human cancer cells and thus triggering autophagic cancer cell death. The anti-inflammatory activities of BF are potentially important for its anticancer functions. Notably, some promising synthetic BF derivatives, including poly (ethylene glycol)-based polymeric prodrug of BF and BF211, have shown potent anticancer activity. Additionally, clinical trials regarding the use of BF-related agents in patients have supported the positive effect of BF as an anticancer treatment. Currently, large-scale randomized, double-blind, placebo or positive drug parallel controlled studies are required to confirm the anticancer potential of BF in various cancer types in the clinical setting. The present review will evaluate the potential mechanisms mediated by BF in intracellular signaling events in cancer cells and various promising BF derivatives that may have greater anticancer activity, thereby clarifying BF-mediated anticancer effects. The experimental and clinical results reviewed strongly emphasize the importance of this topic in future investigations.

Update on the effects of the sodium pump α1 subunit on human glioblastoma: from the laboratory to the clinic

INTRODUCTION

Glioblastoma is a debilitating disease that is associated with poor prognosis and a very limited response to therapies; thus, molecularly targeted therapeutics and personalized therapy are urgently needed. The Na⁺/K⁺-ATPase sodium pump is a transmembrane protein complex that has recently been recognized as an important transducer and integrator of various signals. The sodium pump α1 subunit, which is highly expressed in most glioblastomas compared with that in normal brain tissues, is an emerging cancer target that merits further investigation.

AREAS COVERED

The purpose of this narrative review is to explore the important roles of the sodium pump α1 subunit in glioblastoma and analyze its potential therapeutic applications.

EXPERT OPINION

Expression of the sodium pump α1 subunit in glioblastoma tissues is generally higher than that in normal tissues. Sodium pump α1 subunit-mediated pivotal antiglioblastoma signaling pathways have been reviewed, and their impact on the sensitivity of glioblastoma cells to anticancer drugs has recently been clarified. In addition, various pharmacologically optimized sodium pump inhibitors have recently reached early clinical trials, and explorations of sodium pump α1 subunit inhibitors may hold promise for the development of stratification strategies in which patients are treated based on their isoform expression status.