Cucurbitacin B suppresses metastasis mediated by reactive oxygen species (ROS) via focal adhesion kinase (FAK) in breast cancer MDA-MB-231 cells

Investigation of apoptotic effects of Cucurbitacin D, I, and E mediated by Bax/Bcl-xL, caspase-3/9, and oxidative stress modulators in HepG2 cell line

Cucurbitacins, natural compounds highly abundant in the Cucurbitaceae plant family, are characterized by their anticancer, anti-inflammatory, and hepatoprotective properties. These compounds have potential as therapeutic agents in the treatment of liver cancer. This study investigated the association of cucurbitacin D, I, and E (CuD, CuI, and CuE) with the caspase cascade, Bcl-2 family, and oxidative stress modulators in the HepG2 cell line. We evaluated the antiproliferative effects of CuD, CuI, and CuE using the MTT assay. We analyzed Annexin V/PI double staining, cell cycle, mitochondrial membrane potential, and wound healing assays at different doses of the three compounds. To examine the modulation of the caspase cascade, we determined the protein and gene expression levels of Bax, Bcl-xL, caspase-3, and caspase-9. We evaluated the total antioxidant status (TAS), total oxidant status (TOS), superoxide dismutase (SOD), glutathione (GSH), Total, and Native Thiol levels to measure cellular redox status. CuD, CuI, and CuE suppressed the proliferation of HepG2 cells in a dose-dependent manner. The cucurbitacins induced apoptosis by increasing caspase-3, caspase-9, and Bax activity, inhibiting Bcl-xL activation, causing loss of ΔΨm, and suppressing cell migration. Furthermore, cucurbitacins modulated oxidative stress by increasing TOS levels and decreasing SOD, GSH, TAS, and total and native Thiol levels. Our findings suggest that CuD, CuI, and CuE exert apoptotic effects on the hepatocellular carcinoma cell line by regulating Bax/Bcl-xL, caspase-3/9 signaling, and causing intracellular ROS increase in HepG2 cells.

Cucurbitacin-B inhibits cancer cell migration by targeting mortalin and HDM2: computational and in vitro experimental evidence

Cancer metastasis, a highly complex process wherein cancer cells move from the primary site to other sites in the body, is a major hurdle in its therapeutics. A large array of synthetic chemotherapeutic molecules used for the treatment of metastatic cancers, besides being extremely expensive and unaffordable, are known to cause severe adverse effects leading to poor quality of life (QOL) of the patients. In this premise, natural compounds (considered safe, easily available and economic) that possess the potential to inhibit migration of cancer cells are deemed useful and hence are on demand. Cucurbitacin-B (19-(10→9β)-abeo-10-lanost-5-ene triterpene, called Cuc-B) is a steroid mostly found in plants of Cucurbitaceae family. It has been shown to possess anticancer activity although the molecular mechanism remains poorly defined. We present evidence that Cuc-B has the ability to interact with mortalin and HDM2 proteins that are enriched in cancer cells, suppress wild type p53 function and promote cancer cell migration. Computational analyses showed that Cuc-B interacts with mortalin similar to MKT077 and Withanone, both have been shown to reactivate p53 function and inhibit cell migration. Furthermore, Cuc-B interacted with HDM2 similar to Y30, a well-known inhibitor of HDM2. Experimental cell and molecular analyses demonstrated the downregulation of several proteins, critically involved in cell migration in Cuc-B (low non-toxic doses)-treated cancer cells and exhibited inhibition of cell migration. The data suggested that Cuc-B is a potential natural drug that warrants further mechanistic and clinical studies for its use in the management of metastatic cancers.Communicated by Ramaswamy H. Sarma.

Diselenium-linked dimeric prodrug nanomedicine breaking the intracellular redox balance for triple-negative breast cancer targeted therapy

Triple-negative breast cancer (TNBC) has been regarded as the strongest malignancy in cases of breast cancer with a poor prognosis. The development of effective treatment strategies for TNBC has always been an urgent and unmet need. The intracellular redox balance is essential for maintaining TNBC cell malignancy. Disrupting intracellular redox balance by enlarging reactive oxygen species (ROS) generation and facilitating glutathione (GSH) depletion to amplify intracellular oxidative stress may be an alternative strategy to eliminate TNBC cells. However, inducing ROS generation and GSH depletion concurrently may be challenging. Herein, a diselenium linked-dimeric prodrug nanomedicine FA-SeSe-NPs was developed to break the intracellular redox homeostasis for TNBC targeted therapy. The dimeric prodrug was synthesized by conjugating two cucurbitacin B (CuB) molecules via one diselenium bond, which was subsequently assembled with FA-PEG-DSPE to form the final nanomedicine FA-SeSe-NPs. Using the active targeting potential of folic acid (FA), FA-SeSe-NPs could accumulate in tumor tissue with elevated levels and then be specifically internalized by cancer cells. In the high ROS and GSH conditions of TNBC cells, the diselenium bond can specifically respond to ROS to produce selenium free radicals to increase ROS and react with GSH to generate S-Se bond to deplete GSH. The released CuB further induced ROS production in TNBC cells. The diselenium bond and CuB functioned synergistically to amplify oxidative stress to kill the TNBC cells. Here, we provide a promising strategy to disrupt the intracellular redox balance of cancer cells for effective TNBC therapy.

Apoptotic and antimetastatic effect of cucurbitacins in cancer: recent trends and advancement

The Cucurbitaceae family produces a class of secondary metabolites known as cucurbitacins. The eight cucurbitacin subunits are cucurbitacin B, D, E, I, IIa, L glucoside, Q, and R with the most significant anticancer activity. They are reported to inhibit cell proliferation, invasion, and migration; induce apoptosis; and encourage cell cycle arrest, as some of their modes of action. The JAK-STAT3, Wnt, PI3K/Akt, and MAPK signaling pathways, which are essential for the survival and apoptosis of cancer cells, have also been shown to be suppressed by cucurbitacins. The goal of the current study is to summarize potential molecular targets that cucurbitacins could inhibit in order to suppress various malignant processes. The review is noteworthy since it presents all putative molecular targets for cucurbitacins in cancer on a single podium.

Reactive Oxygen Species-Responsive Nanococktail With Self-Amplificated Drug Release for Efficient Co-Delivery of Paclitaxel/Cucurbitacin B and Synergistic Treatment of Gastric Cancer

Application of drug combinations is a powerful strategy for the therapy of advanced gastric cancer. However, the clinical use of such combinations is greatly limited by the occurrence of severe systemic toxicity. Although polymeric-prodrug-based nanococktails can significantly reduce toxicity of drugs, they have been shown to have low intracellular drug release. To balance between efficacy and safety during application of polymeric-prodrug-based nanococktails, a reactive oxygen species (ROS)-responsive nanococktail (PCM) with self-amplification drug release was developed in this study. In summary, PCM micelles were co-assembled from ROS-sensitive cucurbitacin B (CuB) and paclitaxel (PTX) polymeric prodrug, which were fabricated by covalently grafting PTX and CuB to dextran via an ROS-sensitive linkage. To minimize the side effects of the PCM micelles, a polymeric-prodrug strategy was employed to prevent premature leakage. Once it entered cancer cells, PCM released CuB and PTX in response to ROS. Moreover, the released CuB further promoted ROS generation, which in turn enhanced drug release for better therapeutic effects. In vivo antitumor experiments showed that the PCM-treated group had lower tumor burden (tumor weight was reduced by 92%), but bodyweight loss was not significant. These results indicate that the developed polymeric prodrug, with a self-amplification drug release nanococktail strategy, can be an effective and safe strategy for cancer management.

Biomimetic Cucurbitacin B-Polydopamine Nanoparticles for Synergistic Chemo-Photothermal Therapy of Breast Cancer

Breast cancer is the most common malignant tumor in women. Researchers have found that the combined use of multiple methods to treat tumors is a promising strategy. Here, we have developed a biomimetic nano-platform PDA@MB for tumor targeted photothermal therapy (PTT) combined with chemotherapy. The 4T1 cell membrane loaded with cucurbitacin B (CuB) was used to coat polydopamine (PDA) nanoparticles, which gave PDA@MB nanoparticles the ability to target tumors and escape immune cells from phagocytosis. PDA@MB showed excellent photothermal performance including high photothermal conversion efficiency and photostability, and exhibited outstanding in vitro PTT effect under NIR laser irradiation. The high temperature ruptured the PDA@MB membrane to release CuB, which changed the tumor hypoxic environment, down-regulated the FAK/MMP signaling pathway, and significantly inhibited the metastasis and proliferation of tumor cells. The results of in vivo experiments indicated that the tumor growth of the 4T1 mouse tumor model was significantly inhibited. Additionally, toxicity studies showed that PDA@MB had good biocompatibility and safety. In conclusion, this study provides a promising chemo-photothermal therapy (CPT) nano-platform for precise and effective breast cancer therapy.

Cucurbitacin B Diminishes Metastatic Behavior of Cholangiocarcinoma Cells by Suppressing Focal Adhesion Kinase

OBJECTIVE

Cholangiocarcinoma (CCA) is a malignant tumor with aggressive metastatic property resulted from dysregulation of metastasis-regulated signaling pathways. The aim of this study was to investigate the effect of cucurbitacin B on metastatic behavior of CCA cells through modulation of focal adhesion kinase (FAK) protein.

METHODS

KKU-452 cells were treated with a specific FAK inhibitor, FAK inhibitor-14, or cucurbitacin B at various concentrations for 24 h. Cell viability was assessed by sulforhodamine B assay. The migratory and invasive abilities of the cells were investigated using wound healing and transwell invasion assays, respectively. The fibronectin-coated plate was used for adhesion assay. The effects of the test compounds on FAK activation and the expression of metastasis-associated proteins were determined by Western blot analysis. The amount of MMP-9 was evaluated using a commercial ELISA Kit.

RESULTS

FAK inhibitor-14 and cucurbitacin B at concentrations which minimally affected KKU-452 cell viability could suppress FAK activation, evidently by decreased level of phospho-FAK protein after exposure to the compound. At these conditions, cucurbitacin B suppressed metastatic behavior including migration, invasion and adhesion abilities of CCA cells similar to FAK inhibitor-14. Further molecular studies demonstrated that FAK inhibitor-14 and cucurbitacin B downregulated the expression of metastasis-associated proteins including MMP-9, ICAM-1 and VEGF. Consequently, exposure to cucurbitacin B inhibited the production of MMP-9 enzyme in CCA cells similar to FAK inhibitor-14 treatment.

CONCLUSION

FAK participated in regulation of metastatic behavior of KKU-452 CCA cells. Cucurbitacin B suppressed FAK activation in the cells which was associated with inhibition of metastasis essential steps and their related metastatic proteins. The compound may be developed as a novel therapeutic agent for CCA metastasis therapy.
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Sorafenib and CuB exert synergistic antitumor effects against hepatocellular carcinoma cells via inhibition of STAT3 phosphorylation

Sorafenib, the first‐line agent for treatment of advanced hepatocellular carcinoma (HCC), improves median overall survival by approximately 3 months. In the present study, we investigated whether sorafenib combined with cucurbitacin B (CuB), a natural tetracyclic triterpenoid isolated from Cucurbitaceae, exerts enhanced antitumor effects against HCC. Cell viability and colony formation ability were detected by cell‐counting kit‐8 and colony formation assays. Cell cycle and apoptosis were analyzed by flow cytometry. Protein expression was detected by western blotting. HepG2 xenografts in nude mice were used to evaluate in vivo antitumor effects. We report that sorafenib and CuB exhibited synergistic effects on cellular proliferation inhibition and cell apoptosis induction, but not on cell cycle arrest. Furthermore, combination treatment enhanced levels of cleaved caspase 3 and cleaved caspase 9, but suppressed phosphorylation of STAT3. Epidermal growth factor, a potent stimulator of signal transducer and activator of transcription‐3 (STAT3), promoted cell viability and colony formation ability, whereas combination treatment exerted inhibitory effects on epidermal growth factor‐induced STAT3 phosphorylation. Finally, HepG2 xenograft mice cotreated with sorafenib and CuB exhibited reduced tumor progression without notable weight loss. In conclusion, sorafenib and CuB exert synergistic antitumor effects through a pathway that may involve STAT3 phosphorylation, and this may represent a promising therapeutic approach for treatment of HCC.

Targeted Modulation of FAK/PI3K/PDK1/AKT and FAK/p53 Pathways by Cucurbitacin B for the Antiproliferation Effect Against Human Cholangiocarcinoma Cells

Inadequate responses to traditional chemotherapeutic agents in cholangiocarcinoma (CCA) emphasize a requirement for new effective compounds for the treatment of this malignancy. This study aimed to investigate the antiproliferative property of cucurbitacin B on KKU-100 CCA cells. The determination of underlying molecular mechanisms was also carried out. The results revealed that cucurbitacin B suppressed growth and replicative ability to form colonies of CCA cells, suggesting the antiproliferative effect of this compound against the cells. Flow cytometry analysis demonstrated that the interfering effect of cucurbitacin B on the CCA cell cycle at the G2/M phase was accountable for its antiproliferation property. Accompanied with cell cycle disruption, cucurbitacin B altered the expression of proteins involved in the G2/M phase transition including downregulation of cyclin A, cyclin D1, and cdc25A, and upregulation of p21. Additional molecular studies demonstrated that cucurbitacin B suppressed the activation of focal adhesion kinase (FAK) which consequently resulted in inhibition of its kinase-dependent and kinase-independent downstream targets contributing to the regulation of cell proliferation including PI3K/PDK1/AKT and p53 proteins. In this study, the transient knockdown of FAK using siRNA was employed to ascertain the role of FAK in CCA cell proliferation. Finally, the effect of cucurbitacin B on upstream receptor tyrosine kinases regulating FAK activation was elucidated. The results showed that the inhibitory effect of cucurbitacin B on FAK activation in CCA cells is mediated via interference of EGFR and HER2 expression. Collectively, cucurbitacin B might be a promising drug for CCA treatment by targeting FAK protein.

Redox regulation by SOD2 modulates colorectal cancer tumorigenesis through AMPK-mediated energy metabolism

Colorectal cancer (CRC) is a common malignancy. Many reports have implicated aberrant mitochondrial activity in the progression of CRC, with particular emphasis on the dysregulation of redox signaling and oxidative stress. In this study, we focused on manganese superoxide dismutase (MnSOD/SOD2), a key antioxidant enzyme, which maintains intracellular redox homeostasis. Current literature presents conflicting mechanisms for how SOD2 influences tumorigenesis and tumor progression. Here, we explored the role of SOD2 in CRC specifically. We found high levels of SOD2 expression in CRC tissues. We carried out a series of experiments to determine whether knockdown of SOD2 expression in CRC cell lines would reverse features of tumorigenesis. We found that reduced SOD2 expression decreased cell proliferation, migration, and invasion activity in CRC cells. Results from an additional series of experiments on mitochondrial function implicated a dual role for SOD2 in promoting CRC progression. First, proper level of SOD2 helped CRC cells maintain mitochondrial function by disposal of superoxide (O₂ ^.- ). Second, over-expression of SOD2 induced H₂ O₂ -mediated tumorigenesis by upregulating AMPK and glycolysis. Our results indicate that SOD2 may promote the occurrence and development of CRC by regulating the energy metabolism mediated by AMPK signaling pathways.

[In vitro fertilization-embryo transfer affects focal adhension kinase signaling pathway in early placenta]

OBJECTIVE

To study the effects of in vitro fertilization-embryo transfer (IVF-ET) technique on gene expression of focal adhension kinase (FAK) signaling pathway in early placental trophoblast cells, and to explore the effects of IVF-ET technology on the development and function of early placenta.

METHODS

We collected 7-8 weeks of gestation placenta tissue as a study group by ultrasound guided reduction of fetal from double embryo transfer under IVF-ET technology. In the control group, placenta tissues were obtained from the spontaneous abortion of natural pregnancy twin 7-8 weeks. Microarray hybridization analysis was performed on the placenta tissue of the two groups using the Affymetrix HG-U133 Plus 2.0 gene chip. Eight differentially expressed genes were identified by real-time quantitative polymerase chain reaction (qRT-PCR), and unsupervised clustering analysis and functional bioinformatics analysis were performed for the differentially expressed genes.

RESULTS

Twenty-eight cases of IVF-ET reduced fetal villi and 8 cases of spontaneous abortion villi were collected. A total of 8 placental villi were detected by the gene chip. Compared with the natural pregnancy control group, 32 differentially expressed genes in the placental FAK signaling pathway were expressed in IVF-ET. The differential expression was greater than or equal to 2 times, of which 12 genes were up-regulated and 20 were down-regulated. The qRT-PCR showed that the expression of the 8 genes in FAK signaling pathways of IVF-ET was significantly different from that in the placenta of natural pregnancy, which was consistent with the result of the gene chip detection. The FAK signal pathway gene localization showed that the FAK gene was mainly located in the upstream of the signal pathway in the placenta of IVF-ET. The placental trophoblast cells maintained the FAK signaling pathway function through gene expression compensation.

CONCLUSION

There are gene expression differences in the FAK signaling pathway between the IVF-ET derived early placenta and the natural pregnancy placenta. The differentially expressed genes are involved in many key functions of the FAK signaling pathway and affect the early development and function of the IVF-ET placenta, while the placental trophoblast cells change gene expression for interference to compensate for IVF-ET technology itself, maintain normal function of the FAK signaling pathway, and satisfy the need for placental and fetal development.

Cucurbitacin B inhibits the migration and invasion of breast cancer cells by altering the biomechanical properties of cells

Changes in cellular biomechanical properties affect cell migration and invasion. The natural compound Cucurbitacin B (CuB) has potent anticancer activity; however, the mechanism underlying its inhibitory effect on breast cancer metastasis needs further study. Here, we showed that low-dose CuB inhibited adhesion and altered the viscoelasticity of breast cancer cells, thereby, reducing cell deformability. In vitro and in vivo experiments proved that CuB effectively inhibited the migration and invasion of breast cancer cells. Further studies have found that CuB downregulated the expression of F-actin/vimentin/FAK/vinculin in breast cancer cells, altering the distribution and reorganization of cytoskeletal proteins in the cells. CuB inhibited signaling by the Rho family GTPases RAC1/CDC42/RhoA downstream of integrin. These findings indicate that CuB has been proven to mediate the reorganization and distribution of cytoskeletal proteins of breast cancer cells through RAC1/CDC42/RhoA signaling, which improves the mechanical properties of cell adhesion and deformation and consequently inhibits cell migration and invasion.