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

Bufalin-Loaded Multifunctional Photothermal Nanoparticles Inhibit the Anaerobic Glycolysis by Targeting SRC-3/HIF-1α Pathway for Improved Mild Photothermal Therapy in CRC

Purpose

Compared with traditional photothermal therapy (PTT, >50°C), mild PTT (≤45°C) is a promising strategy for tumor therapy with fewer adverse effects. Unfortunately, its anti-tumor efficacy is hampered by thermoresistance induced by overexpression of heat shock proteins (HSPs). In our previous study, we found bufalin (BU) is a glycolysis inhibitor that depletes HSPs, which is expected to overcome thermotolerance of tumor cells. In this study, BU-loaded multifunctional nanoparticles (NPs) were developed for enhancing the mild PTT of colorectal cancer (CRC).

Methods

Fe3O4 NPs coated with the polydopamine (PDA) shell modified with polyethylene glycol (PEG) and cyclic arginine-glycyl-aspartic peptide (cRGD) for loading BU (Fe3O4@PDA-PEG-cRGD/BU NPs) were developed. The thermal variations in Fe3O4@PDA-PEG-cRGD/BU NPs solution under different conditions were measured. Glycolysis inhibition was evaluated by measuring the glucose uptake, extracellular lactate, and intracellular adenosine triphosphate (ATP) levels. The cellular cytotoxicity of Fe3O4@PDA-PEG-cRGD/BU NPs was analyzed using a cell counting kit-8 assay, Calcein-AM/PI double staining, and flow cytometry in HCT116 cells. The magnetic resonance imaging (MRI) performance and anti-tumor therapeutic efficacy of Fe3O4@PDA-PEG-cRGD/BU NPs were evaluated in HCT116-tumor bearing mice.

Results

Fe3O4@PDA-PEG-cRGD/BU NPs had an average diameter of 260.4±3.5 nm, the zeta potential of -23.8±1.6 mV, the drug loading rate of 1.1%, which had good thermal stability, photothermal conversion efficiencies and MRI performance. In addition, the released BU not only killed tumor cells but also interfered with glycolysis by targeting the steroid receptor coactivator 3 (SRC-3)/HIF-1α pathway, preventing intracellular ATP synthesis, and combating HSP-dependent tumor thermoresistance, ultimately strengthening the thermal sensitivity toward mild PTT both in vitro and in vivo.

Conclusion

This study provides a highly effective strategy for enhancing the therapeutic effects of mild PTT toward tumors.

Mechanism of bufalin inhibition of colon cancer liver metastasis by regulating M2-type polarization of Kupffer cells induced by highly metastatic colon cancer cells

Patients with metastatic colorectal cancer often have poor outcomes, primarily due to hepatic metastasis. Colorectal cancer (CRC) cells have the ability to secrete cytokines and other molecules that can remodel the tumor microenvironment, facilitating the spread of cancer to the liver. Kupffer cells (KCs), which are macrophages in the liver, can be polarized to M2 type, thereby promoting the expression of adhesion molecules that aid in tumor metastasis. Our research has shown that huachanshu (with bufalin as the main active monomer) can effectively inhibit CRC metastasis. However, the underlying mechanism still needs to be thoroughly investigated. We have observed that highly metastatic CRC cells have a greater ability to induce M2-type polarization of Kupffer cells, leading to enhanced metastasis. Interestingly, we have found that inhibiting the expression of IL-6, which is highly expressed in the serum, can reverse this phenomenon. Notably, bufalin has been shown to attenuate the M2-type polarization of Kupffer cells induced by highly metastatic Colorectal cancer (mCRC) cells and down-regulate IL-6 expression, ultimately inhibiting tumor metastasis. In this project, our aim is to study how high mCRC cells induce M2-type polarization and how bufalin, via the SRC-3/IL-6 pathway, can inhibit CRC metastasis. This research will provide a theoretical foundation for understanding the anti-CRC effect of bufalin.

Consolidating Organometallic Complex Empowers Mitochondria-Directed Chemotherapy against Resistant Cancer via Stemness and Metastasis Inhibition

Cancer treatment has faced severe obstacles due to the smart biological system of cancer cells. Herein, we report a three-in-one agent Ir-CA via attenuation of cancer cell stemness with the down-regulated biomarker CD133 expression from the mitochondria-directed chemotherapy. Over 80% of Ir-CA could accumulate in mitochondria, result in severe mitochondrial dysfunctions, and subsequently initiate mitophagy and cell cycle arrest to kill cisplatin-resistant A549R cells. In vitro and in vivo antimetastatic experiments demonstrated that Ir-CA can effectively inhibit metastasis with down-regulated MMP-2/MMP-9. RNA seq analysis and Western blotting indicated that Ir-CA also suppresses the GSTP1 expression to decrease the intracellular Pt-GS adducts, resulting in the detoxification and resensitization to cisplatin of A549R cells. In vivo evaluation indicated that Ir-CA restrains the tumor growth and has minimal side effects and superior biocompatibility. This work not only provides the first three-in-one agent to attenuate cancer cell stemness and simultaneously realize anticancer, antimetastasis, and conquer metallodrug resistance but also demonstrates the effectiveness of the mitochondria-directed strategy in cancer treatment.

Functional Roles of CD133: More than Stemness Associated Factor Regulated by the Microenvironment

CD133 protein has been one of the most used surface markers to select and identify cancer cells with stem-like features. However, its expression is not restricted to tumoral cells; it is also expressed in differentiated cells and stem/progenitor cells in various normal tissues. CD133 participates in several cellular processes, in part orchestrating signal transduction of essential pathways that frequently are dysregulated in cancer, such as PI3K/Akt signaling and the Wnt/β-catenin pathway. CD133 expression correlates with enhanced cell self-renewal, migration, invasion, and survival under stress conditions in cancer. Aside from the intrinsic cell mechanisms that regulate CD133 expression in each cellular type, extrinsic factors from the surrounding niche can also impact CD33 levels. The enhanced CD133 expression in cells can confer adaptive advantages by amplifying the activation of a specific signaling pathway in a context-dependent manner. In this review, we do not only describe the CD133 physiological functions known so far, but importantly, we analyze how the microenvironment changes impact the regulation of CD133 functions emphasizing its value as a marker of cell adaptability beyond a cancer-stem cell marker.

Cell membrane-camouflaged bufalin targets NOD2 and overcomes multidrug resistance in pancreatic cancer

AIMS

Multidrug resistance in pancreatic cancer poses a significant challenge in clinical treatment. Bufalin (BA), a compound found in secretions from the glands of toads, may help overcome this problem. However, severe cardiotoxicity thus far has hindered its clinical application. Hence, the present study aimed to develop a cell membrane-camouflaged and BA-loaded polylactic-co-glycolic acid nanoparticle (CBAP) and assess its potential to counter chemoresistance in pancreatic cancer.

METHODS

The toxicity of CBAP was evaluated by electrocardiogram, body weight, distress score, and nesting behavior of mice. In addition, the anticarcinoma activity and underlying mechanism were investigated both in vitro and in vivo.

RESULTS

CBAP significantly mitigated BA-mediated acute cardiotoxicity and enhanced the sensitivity of pancreatic cancer to several clinical drugs, such as gemcitabine, 5-fluorouracil, and FOLFIRINOX. Mechanistically, CBAP directly bound to nucleotide-binding and oligomerization domain containing protein 2 (NOD2) and inhibited the expression of nuclear factor kappa-light-chain-enhancer of activated B cells. This inhibits the expression of ATP-binding cassette transporters, which are responsible for chemoresistance in cancer cells.

CONCLUSIONS

Our findings indicate that CBAP directly inhibits NOD2. Combining CBAP with standard-of-care chemotherapeutics represents a safe and efficient strategy for the treatment of pancreatic cancer.

Tumor microenvironment diversity and plasticity in cancer multidrug resistance

Multidrug resistance (MDR) poses a significant obstacle to effective cancer treatment, and the tumor microenvironment (TME) is crucial for MDR development and reversal. The TME plays an active role in promoting MDR through several pathways. However, a promising therapeutic approach for battling MDR involves targeting specific elements within the TME. Therefore, this comprehensive review elaborates on the research developments regarding the dual role of the TME in promoting and reversing MDR in cancer. Understanding the complex role of the TME in promoting and reversing MDR is essential to developing effective cancer therapies. Utilizing the adaptability of the TME by targeting novel TME-specific factors, utilizing combination therapies, and employing innovative treatment strategies can potentially combat MDR and achieve personalized treatment outcomes for patients with cancer.

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.

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.

Toad venom-derived bufadienolides and their therapeutic application in prostate cancers: Current status and future directions

Cancer is the second leading cause of death worldwide. Specially, the high incidence rate and prevalence of drug resistance have rendered prostate cancer (PCa) a great threat to men’s health. Novel modalities with different structures or mechanisms are in urgent need to overcome these two challenges. Traditional Chinese medicine toad venom-derived agents (TVAs) have shown to possess versatile bioactivities in treating certain diseases including PCa. In this work, we attempted to have an overview of bufadienolides, the major bioactive components in TVAs, in the treatment of PCa in the past decade, including their derivatives developed by medicinal chemists to antagonize certain drawbacks of bufadienolides such as innate toxic effect to normal cells. Generally, bufadienolides can effectively induce apoptosis and suppress PCa cells in-vitro and in-vivo, majorly mediated by regulating certain microRNAs/long non-coding RNAs, or by modulating key pro-survival and pro-metastasis players in PCa. Importantly, critical obstacles and challenges using TVAs will be discussed and possible solutions and future perspectives will also be presented in this review. Further in-depth studies are clearly needed to decipher the mechanisms, e.g., targets and pathways, toxic effects and fully reveal their application. The information collected in this work may help evoke more effects in developing bufadienolides as therapeutic agents in PCa.

Bufalin reverses cancer-associated fibroblast-mediated colorectal cancer metastasis by inhibiting the STAT3 signaling pathway

At present, recurrence and metastasis are still important factors that lead to a poor prognosis among colorectal cancer (CRC) patients. Cancer-associated fibroblasts (CAFs) can promote tumorigenesis and development. Bufalin is the main active monomer of the clinical drug cinobufacini, which exhibits antitumor activity in various cancers. But few research have investigated the effect of bufalin in inhibiting metastasis from the perspective of the tumor microenvironment. We first isolated CAFs from freshly resected colorectal cancer patient specimens and observed the effect of CAFs on CRC cell invasion through a series of experiments. We explored the effect of bufalin on the physiological activity of CRC mediated by CAFs through experiments. In our study, we found that CAFs could promote CRC cell activity through the STAT3 pathway. Bufalin reversed CAF-mediated CRC invasion and metastasis by inhibiting the STAT3 pathway. Overexpression of STAT3 attenuated the inhibitory function of bufalin on invasion and metastasis. Taken together, bufalin can reverse CAF-mediated colorectal cancer metastasis based on inhibiting the STAT3 signaling pathway.

α‑hederin overcomes hypoxia‑mediated drug resistance in colorectal cancer by inhibiting the AKT/Bcl2 pathway

Currently, chemoresistance is a major challenge that directly affects the prognosis of patients with colorectal cancer (CRC). In addition, hypoxia is associated with poor prognosis and therapeutic resistance in patients with cancer. Accumulating evidence has shown that α‑hederin has significant antitumour effects and that α‑hederin can inhibit hypoxia‑mediated drug resistance in CRC; however, the underlying mechanism remains unclear. In the present study, viability and proliferation assays were used to evaluate the effect of α‑hederin on the drug resistance of CRC cells under hypoxia. Sequencing analysis and apoptosis assays were used to determine the effect of α‑hederin on apoptosis under hypoxia. Western blot analysis and reverse transcription‑quantitative PCR were used to measure apoptosis‑related protein and mRNA expression levels. Furthermore, different mouse models were established to study the effect of α‑hederin on hypoxia‑mediated CRC drug resistance in vivo. In the present study, the high expression of Bcl2 in hypoxic CRC cells was revealed to be a key factor in their drug resistance, whereas α‑hederin inhibited the expression of Bcl2 by reducing AKT phosphorylation in vitro and in vivo, and promoted the apoptosis of CRC cells under hypoxia. By contrast, overexpression of AKT reversed the effect of α‑hederin on CRC cell apoptosis under hypoxia. Taken together, these results suggested that α‑hederin may overcome hypoxia‑mediated drug resistance in CRC by inhibiting the AKT/Bcl2 pathway. In the future, α‑hederin may be used as a novel adjuvant for reversing drug resistance in CRC.

Bufalin alleviates acute kidney injury by regulating NLRP3 inflammasome-mediated pyroptosis

BACKGROUND

Recently, there has been an increasing clinical incidence of acute kidney injury (AKI), which rapidly declines renal function and leads to massive tubular cell necrosis. Pyroptosis is an inflammatory process of cell death that is more rapid than apoptosis, which is accompanied by a massive release of inflammasome activation. In the study, we aim to explore whether Bufalin regulates the AKI through the pyroptosis pathway.

METHODS

We have established gentamicin (GM)-induced AKI animal and cell models to simulate the pathological conditions of kidney injury. The expression of renal injury and pyroptosis-related indicators were detected by western blot. PAS staining and IHC staining were used to analyze renal function. CCK-8 assay was performed to detect cell viability after AKI with different treatments. TUNEL staining, flow cytometry and immunofluorescence assays were performed to measure pyroptosis.

RESULTS

After intraperitoneal injection of GM in rats, renal function was significantly decreased, along with a significant increase of damaged and necrotic cells as suggested by renal tubular epithelial tissue sections. In addition, there was an increase in the pyroptosis-related markers expression and pyroptosis-induced cell death. Consistently, studies in vitro found that GM significantly induced pyroptosis and its associated protein expression in NRK52e cells. Whereas, the administration of Bufalin reversed these effects of GM in vivo and in vitro. Further, we found that Nigericin (NLRP3 agonist) could reversed the effects of bufalin on GM-induced pyroptosis.

CONCLUSION

Bufalin attenuates pyroptosis generated AKI by inhibiting NLRP3 inflammasome.

Biological impact and therapeutic perspective of targeting PI3K/Akt signaling in hepatocellular carcinoma: Promises and Challenges

Cancer progression results from activation of various signaling networks. Among these, PI3K/Akt signaling contributes to proliferation, invasion, and inhibition of apoptosis. Hepatocellular carcinoma (HCC) is a primary liver cancer with high incidence rate, especially in regions with high prevalence of viral hepatitis infection. Autoimmune disorders, diabetes mellitus, obesity, alcohol consumption, and inflammation can also lead to initiation and development of HCC. The treatment of HCC depends on the identification of oncogenic factors that lead tumor cells to develop resistance to therapy. The present review article focuses on the role of PI3K/Akt signaling in HCC progression. Activation of PI3K/Akt signaling promotes glucose uptake, favors glycolysis and increases tumor cell proliferation. It inhibits both apoptosis and autophagy while promoting HCC cell survival. PI3K/Akt stimulates epithelial-to-mesenchymal transition (EMT) and increases matrix-metalloproteinase (MMP) expression during HCC metastasis. In addition to increasing colony formation capacity and facilitating the spread of tumor cells, PI3K/Akt signaling stimulates angiogenesis. Therefore, silencing PI3K/Akt signaling prevents aggressive HCC cell behavior. Activation of PI3K/Akt signaling can confer drug resistance, particularly to sorafenib, and decreases the radio-sensitivity of HCC cells. Anti-cancer agents, like phytochemicals and small molecules can suppress PI3K/Akt signaling by limiting HCC progression. Being upregulated in tumor tissues and clinical samples, PI3K/Akt can also be used as a biomarker to predict patients' response to therapy.

Bufalin Inhibits Tumorigenesis, Stemness, and Epithelial-Mesenchymal Transition in Colorectal Cancer through a C-Kit/Slug Signaling Axis

Colorectal cancer (CRC) is a major source of morbidity and mortality, characterized by intratumoral heterogeneity and the presence of cancer stem cells (CSCs). Bufalin has potent activity against many tumors, but studies of its effect on CRC stemness are limited. We explored bufalin's function and mechanism using CRC patient-derived organoids (PDOs) and cell lines. In CRC cells, bufalin prevented nuclear translocation of β-catenin and down-regulated CSC markers (CD44, CD133, LGR5), pluripotency factors, and epithelial-mesenchymal transition (EMT) markers (N-Cadherin, Slug, ZEB1). Functionally, bufalin inhibited CRC spheroid formation, aldehyde dehydrogenase activity, migration, and invasion. Network analysis identified a C-Kit/Slug signaling axis accounting for bufalin's anti-stemness activity. Bufalin treatment significantly downregulated C-Kit, as predicted. Furthermore, overexpression of C-Kit induced Slug expression, spheroid formation, and bufalin resistance. Similarly, overexpression of Slug resulted in increased expression of C-Kit and identical functional effects, demonstrating a pro-stemness feedback loop. For further study, we established PDOs from diagnostic colonoscopy. Bufalin differentially inhibited PDO growth and proliferation, induced apoptosis, restored E-cadherin, and downregulated CSC markers CD133 and C-Myc, dependent on C-Kit/Slug. These findings suggest that the C-Kit/Slug axis plays a pivotal role in regulating CRC stemness, and reveal that targeting this axis can inhibit CRC growth and progression.

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.

Bufalin exacerbates Photodynamic therapy of colorectal cancer by targeting SRC-3/HIF-1α pathway

Photodynamic therapy (PDT) induces tumour cell death by producing reactive oxygen species (ROS), and hypoxia is one of the main factors that limits its efficiency. In our previous study, bufalin (BU) enhanced photosensitizer mTHPC-mediated PDT therapy in colorectal cancer (CRC) cells, but its mechanism was not elucidated. To explore a strategy for improving the efficacy of PDT, we designed iRGD-modified nanoparticles to co-capsuled mTHPC and BU for simultaneous delivery to the tumour site and explored the underlying mechanism of the synergistic anti-CRC effect. In our study, mTHPC&BU@VES-CSO/TPGS-RGD nanoparticles (T-B@NP) had a particle size of 148.3 ± 2.5 nm and a zeta potential of 22.8 ± 2.0 mV. Specifically, these nanoparticles passively accumulated in tumour cells, and under laser irradiation, mTHPC induced cell apoptosis and death. In addition, the sustained release of BU inhibited HIF-1α and reduced VEGF-mediated angiogenesis by targeting the SRC-3/HIF-1α pathway, which induced a strong PDT effect against CRC. In vivo studies demonstrated that codelivery of the nanoparticles under laser irradiation exhibited a superior antitumour effect (84.2%) and significantly prolonged survival time of mice, with the mechanisms of alleviating hypoxia and inhibiting angiogenesis. In summary, mTHPC and BU codelivery via nanoparticles efficiently enhances the therapeutic effects of PDT by inhibiting the SRC-3/HIF-1α pathway in CRC. This work provides an effective strategy to combat hypoxia-induced tumour resistance and overcome the barriers of PDT treatment.

mPEG-Cholic acid/TPGS mixed micelles for combined delivery of paclitaxel and bufalin to treat hepatocellular carcinoma

In this study, amphiphilic block copolymer mPEG-cholic acid was synthesized in conjunction with TPGS as stabilizer to prepare multifunctional micelles. The formed polymeric micelles (PCTm) were used for the delivery of paclitaxel (PTX) and bufalin (BF). PEG group could enhance solubility and extend circulation time, while cholic acid groups achieved the liver targeted function. Combinations of these approaches could realize a synergistic therapeutic effect in the treatment of advanced hepatocellular carcinoma. CLSM in vitro results demonstrated that drug capsulation into PCTm could enhance cellular uptake. FCM results confirmed the uptake amount of C₆/PCTm was 7.5-fold higher than that of free C₆ after incubation for 2 h. Competitive inhibition test proved the Na⁺-taurocholate co-transporting polypeptide (NTCP) involved in the uptake mechanism of PCTm. Meanwhile, in vivo imaging assays demonstrated that the fluorescence intensity of Cy5.5/PCTm was higher than that of free Cy5.5 on liver and tumor with extended circulation time to 48 h. In addition, in vivo studies confirmed that the combined therapy exhibited the strongest tumor inhibition rate of 82.29% with lower systemic toxicity. Hence, these results indicated that PCTm could provide a promising strategy for targeting hepatocellular carcinoma and achieve the goal of the synergism and attenuation.

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.

Traditional Chinese medicine reverses cancer multidrug resistance and its mechanism

Chemotherapy is one of the most commonly used clinical treatments among the currently available cancer therapies. However, the phenomenon of Multidrug resistance (MDR) has become a challenge in the treatment process, weakening the impact of chemotherapy. Extensive research on elucidating the development of cancer MDR has identified the following mechanisms that play a critical role in the development of several MDR reversal agents: abnormal expression of cell membrane transporters, adaptation of cancer cells to the microenvironment, regulation of hypoxia, repair of DNA damage and reduction of apoptosis, the enhancement of the EMT process, the existence of cancer stem cells (CSCs), and the abnormal activation of key signaling pathways. However, they failed to demonstrate significant efficacy due to severe side effects during their clinical trials. Traditional Chinese medicines (TCMs) are known to play an important anti-cancer role since they have low toxicity, high efficacy, and safety and can reverse MDR. TCMs reversal agents can be divided into Chinese medicine monomers, synthetic monomers, analogs, or derivatives. Several studies have shown that TCMs can effectively overcome cancer MDR and can be effectively used for treating cancer patients.

Bufalin suppresses tumour microenvironment-mediated angiogenesis by inhibiting the STAT3 signalling pathway

BACKGROUND

Antiangiogenic therapy has increasingly become an important strategy for the treatment of colorectal cancer. Recent studies have shown that the tumour microenvironment (TME) promotes tumour angiogenesis. Bufalin is an active antitumour compound whose efficacy has been indicated by previous studies. However, there are very few studies on the antiangiogenic effects of bufalin.

METHODS

Herein, human umbilical vein endothelial cell (HUVEC) tube formation, migration and adhesion tests were used to assess angiogenesis in vitro. Western blotting and quantitative PCR were used to detect relevant protein levels and mRNA expression levels. A subcutaneous xenograft tumour model and a hepatic metastasis model were established in mice to investigate the influence of bufalin on angiogenesis mediated by the TME in vivo.

RESULTS

We found that angiogenesis mediated by cells in the TME was significantly inhibited in the presence of bufalin. The results demonstrated that the proangiogenic genes in HUVECs, such as VEGF, PDGFA, E-selectin and P-selectin, were downregulated by bufalin and that this downregulation was mediated by inhibition of the STAT3 pathway. Overexpression of STAT3 reversed the inhibitory effects of bufalin on angiogenesis. Furthermore, there was little reduction in angiogenesis when bufalin directly acted on the cells in the tumour microenvironment.

CONCLUSION

Our findings demonstrate that bufalin suppresses tumour microenvironment-mediated angiogenesis by inhibiting the STAT3 signalling pathway in vascular endothelial cells, revealing that bufalin may be used as a new antiangiogenic adjuvant therapy medicine to treat colorectal cancer.

Bufalin targets the SRC-3/MIF pathway in chemoresistant cells to regulate M2 macrophage polarization in colorectal cancer

M2-polarized macrophages are one of critical factors in tumour chemoresistance. An increasing number of studies have shown that M2 macrophage polarization can be promoted by chemoresistance. A large number of evidences indicate that Bufalin has significant antitumour effect, previous studies have found that Bufalin can reduce the polarization of M2 macrophages to play an anti-tumour effect in vivo, but the mechanism remains unclear. In our study, we found that Bufalin reduced the polarization of M2 macrophages induced by chemoresistant cells both in vivo and in vitro; however, Bufalin had no obvious direct effect on M2 macrophage polarization. Furthermore, we demonstrated that Bufalin targeted the SRC-3 protein to reduce MIF release in chemoresistant cells in order to regulate the polarization of M2 macrophages. More interestingly, we also found that Cinobufacini, Bufalin is its main active monomer, which its could regulate the polarization of M2 macrophages to enhance the anti-tumour effect of oxaliplatin in vivo and in the clinic. Overall, this study provides a theoretical basis for the clinical application of drugs containing Bufalin as the main active ingredient in combination with established chemotherapy for the treatment of colorectal cancer.

Toad venom: A comprehensive review of chemical constituents, anticancer activities, and mechanisms

Toad venom, a traditional natural medicine, has been used for hundreds of years in China for treating different diseases. Many studies have been performed to elucidate the cardiotonic and analgesic activities of toad venom. Until the last decade, an increasing number of studies have documented that toad venom is a source of lead compound(s) for the development of potential cancer treatment drugs. Research has shown that toad venom contains 96 types of bufadienolide monomers and 23 types of indole alkaloids, such as bufalin, cinobufagin, arenobufagin, and resibufogenin, which exhibit a wide range of anticancer activities in vitro and, in particular, in vivo for a range of cancers. The main antitumor mechanisms are likely to be apoptosis or/and autophagy induction, cell cycle arrest, cell metastasis suppression, reversal of drug resistance, or growth inhibition of cancer cells. This review summarizes the chemical constituents of toad venom, analyzing their anticancer activities and molecular mechanisms for cancer treatments. We also outline the importance of further studies regarding the material basis and anticancer mechanisms of toad venom.

Control of Oxidative Stress in Cancer Chemoresistance: Spotlight on Nrf2 Role

Chemoresistance represents the main obstacle to cancer treatment with both conventional and targeted therapy. Beyond specific molecular alterations, which can lead to targeted therapy, metabolic remodeling, including the control of redox status, plays an important role in cancer cell survival following therapy. Although cancer cells generally have a high basal reactive oxygen species (ROS) level, which makes them more susceptible than normal cells to a further increase of ROS, chemoresistant cancer cells become highly adapted to intrinsic or drug-induced oxidative stress by upregulating their antioxidant systems. The antioxidant response is principally mediated by the transcription factor Nrf2, which has been considered the master regulator of antioxidant and cytoprotective genes. Nrf2 expression is often increased in several types of chemoresistant cancer cells, and its expression is mediated by diverse mechanisms. In addition to Nrf2, other transcription factors and transcriptional coactivators can participate to maintain the high antioxidant levels in chemo and radio-resistant cancer cells. The control of expression and function of these molecules has been recently deepened to identify which of these could be used as a new therapeutic target in the treatment of tumors resistant to conventional therapy. In this review, we report the more recent advances in the study of Nrf2 regulation in chemoresistant cancers and the role played by other transcription factors and transcriptional coactivators in the control of antioxidant responses in chemoresistant cancer cells.

Biomedical application of chitosan-based nanoscale delivery systems: Potential usefulness in siRNA delivery for cancer therapy

Gene therapy is an emerging and promising strategy in cancer therapy where small interfering RNA (siRNA) system has been deployed for down-regulation of targeted gene and subsequent inhibition in cancer progression; some issues with siRNA, however, linger namely, its off-targeting property and degradation by enzymes. Nanoparticles can be applied for the encapsulation of siRNA thus enhancing its efficacy in gene silencing where chitosan (CS), a linear alkaline polysaccharide derived from chitin, with superb properties such as biodegradability, biocompatibility, stability and solubility, can play a vital role. Herein, the potential of CS nanoparticles has been discussed for the delivery of siRNA in cancer therapy; proliferation, metastasis and chemoresistance are suppressed by siRNA-loaded CS nanoparticles, especially the usage of pH-sensitive CS nanoparticles. CS nanoparticles can provide a platform for the co-delivery of siRNA and anti-tumor agents with their enhanced stability via chemical modifications. As pre-clinical experiments are in agreement with potential of CS-based nanoparticles for siRNA delivery, and these carriers possess biocompatibiliy and are safe, further studies can focus on evaluating their utilization in cancer patients.

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.