Cantharidin, a potent and selective PP2A inhibitor, induces an oxidative stress-independent growth inhibition of pancreatic cancer cells through G2/M cell-cycle arrest and apoptosis

H2AX: A key player in DNA damage response and a promising target for cancer therapy

Cancer is caused by a complex interaction of factors that interrupt the normal growth and division of cells. At the center of this process is the intricate relationship between DNA damage and the cellular mechanisms responsible for maintaining genomic stability. When DNA damage is not repaired, it can cause genetic mutations that contribute to the initiation and progression of cancer. On the other hand, the DNA damage response system, which involves the phosphorylation of the histone variant H2AX (γH2AX), is crucial in preserving genomic integrity by signaling and facilitating the repair of DNA double-strand breaks. This review provides an explanation of the molecular dynamics of H2AX in the context of DNA damage response. It emphasizes the crucial role of H2AX in recruiting and localizing repair machinery at sites of chromatin damage. The review explains how H2AX phosphorylation, facilitated by the master kinases ATM and ATR, acts as a signal for DNA damage, triggering downstream pathways that govern cell cycle checkpoints, apoptosis, and the cellular fate decision between repair and cell death. The phosphorylation of H2AX is a critical regulatory point, ensuring cell survival by promoting repair or steering cells towards apoptosis in cases of catastrophic genomic damage. Moreover, we explore the therapeutic potential of targeting H2AX in cancer treatment, leveraging its dual function as a biomarker of DNA integrity and a therapeutic target. By delineating the pathways that lead to H2AX phosphorylation and its roles in apoptosis and cell cycle control, we highlight the significance of H2AX as both a prognostic tool and a focal point for therapeutic intervention, offering insights into its utility in enhancing the efficacy of cancer treatments.

Unveil the mechanism for EHMT -- A novel triterpenoid inhibits proliferation and induces apoptosis in colon cancer through ROS-mediated JNK signaling pathway

Colon cancer ranks among the most prevalent malignancies worldwide, trailing only lung and breast cancer in incidence. Despite the availability of numerous therapeutic strategies, the burden of new cases and fatalities remains high in countries undergoing socioeconomic transitions. Natural products offer promising avenues for developing more effective and less toxic anticancer agents, expanding the clinical arsenal. In this investigation, we isolated a triterpenoid, (21 S,23 R,24 R)-21,23-epoxy-24-hydroxy-21-methoxytirucalla-7,25-dien-3-one (EHMT), from the fruits of Melia azedarach L., which exhibited significant inhibitory activity against colon cancer cells while sparing normal cells. EHMT effectively curtailed colony formation and induced apoptosis and cell cycle arrest in the HCT116 cell line. Furthermore, EHMT prompted the generation of reactive oxygen species (ROS) and the depolarization of mitochondrial membrane potential. Notably, EHMT treatment triggered ROS-mediated cell apoptosis via activation of the JNK signaling pathway in HCT116 cells. Additionally, our findings extended to Caenorhabditis elegans, where EHMT induced ROS accumulation and apoptosis. Collectively, these findings position EHMT as a promising candidate for the development of anticancer agents in the treatment of colon cancer, offering new hope in the battle against this formidable disease.

Shuganning Injection Suppresses Apoptosis for Protecting Against Cantharidin-Induced Liver Injury by Network Pharmacology and Experiment Validation

Cantharidin (CTD) is a compound of mylabris with antitumor activity, and CTD can potentially cause toxicity, especially hepatotoxicity. The classical Traditional Chinese Medicine prescription Shuganning injection (SGNI) exerts notable anti-inflammatory and hepatoprotective effects. However, the protective property and mechanism of SGNI against CTD-induced liver injury (CTD-DILI) have not yet been elucidated. To investigate the effective compounds, potential targets, and molecular mechanism of SGNI against CTD-DILI, network pharmacology combined with experiments were performed. This study found that SGNI could act with 62 core therapeutic targets, regulate multiple biological processes such as apoptosis, and oxidative stress, and influence apoptotic and p53 signaling pathways to treat CTD-DILI. Subsequently, HepaRG cell experiments demonstrated that SGNI pretreatment significantly increased the levels of GSH-Px and SOD, inhibiting the apoptosis induced by CTD. In vivo, according to H&E staining, SGNI can reduce the degeneration of hepatocytes and cytoplasmic vacuolation in mice exposed to CTD. Western blot analysis results indicated that SGNI pretreatment significantly suppressed the expressions of Caspase-3 and Bax while increasing the expression of Bcl-2. In conclusion, SGNI acted as a protective agent against CTD-DILI by inhibiting apoptosis.

PP2A Affects Angiogenesis via Its Interaction with a Novel Phosphorylation Site of TSP1

Alterations in angiogenic properties play a pivotal role in the manifestation and onset of various pathologies, including vascular diseases and cancer. Thrombospondin-1 (TSP1) protein is one of the master regulators of angiogenesis. This study unveils a novel aspect of TSP1 regulation through reversible phosphorylation. The silencing of the B55α regulatory subunit of protein phosphatase 2A (PP2A) in endothelial cells led to a significant decrease in TSP1 expression. Direct interaction between TSP1 and PP2A-B55α was confirmed via various methods. Truncated TSP1 constructs were employed to identify the phosphorylation site and the responsible kinase, ultimately pinpointing PKC as the enzyme phosphorylating TSP1 on Ser93. The biological effects of B55α-TSP1 interaction were also analyzed. B55α silencing not only counteracted the increase in TSP1 expression during wound closure but also prolonged wound closure time. Although B55α silenced cells initiated tube-like structures earlier than control cells, their spheroid formation was disrupted, leading to disintegration. Cells transfected with phosphomimic TSP1 S93D exhibited smaller spheroids and reduced effectiveness in tube formation, revealing insights into the effects of TSP1 phosphorylation on angiogenic properties. In this paper, we introduce a new regulatory mechanism of angiogenesis by reversible phosphorylation on TSP1 S93 by PKC and PP2A B55α.

p300 nucleocytoplasmic shuttling underlies mTORC1 hyperactivation in Hutchinson-Gilford progeria syndrome

The mechanistic target of rapamycin complex 1 (mTORC1) is a master regulator of cell growth, metabolism and autophagy. Multiple pathways modulate mTORC1 in response to nutrients. Here we describe that nucleus-cytoplasmic shuttling of p300/EP300 regulates mTORC1 activity in response to amino acid or glucose levels. Depletion of these nutrients causes cytoplasm-to-nucleus relocalization of p300 that decreases acetylation of the mTORC1 component raptor, thereby reducing mTORC1 activity and activating autophagy. This is mediated by AMP-activated protein kinase-dependent phosphorylation of p300 at serine 89. Nutrient addition to starved cells results in protein phosphatase 2A-dependent dephosphorylation of nuclear p300, enabling its CRM1-dependent export to the cytoplasm to mediate mTORC1 reactivation. p300 shuttling regulates mTORC1 in most cell types and occurs in response to altered nutrients in diverse mouse tissues. Interestingly, p300 cytoplasm-nucleus shuttling is altered in cells from patients with Hutchinson-Gilford progeria syndrome. p300 mislocalization by the disease-causing protein, progerin, activates mTORC1 and inhibits autophagy, phenotypes that are normalized by modulating p300 shuttling. These results reveal how nutrients regulate mTORC1, a cytoplasmic complex, by shuttling its positive regulator p300 in and out of the nucleus, and how this pathway is misregulated in Hutchinson-Gilford progeria syndrome, causing mTORC1 hyperactivation and defective autophagy.

Altering phosphorylation in cancer through PP2A modifiers

Protein phosphatase 2A (PP2A) is a serine/threonine phosphatase integral to the regulation of many cellular processes. Due to the deregulation of PP2A in cancer, many of these processes are turned toward promoting tumor progression. Considerable research has been undertaken to discover molecules capable of modulating PP2A activity in cancer. Because PP2A is capable of immense substrate specificity across many cellular processes, the therapeutic targeting of PP2A in cancer can be completed through either enzyme inhibitors or activators. PP2A modulators likewise tend to be effective in drug-resistant cancers and work synergistically with other known cancer therapeutics. In this review, we will discuss the patterns of PP2A deregulation in cancer, and its known downstream signaling pathways important for cancer regulation, along with many activators and inhibitors of PP2A known to inhibit cancer progression.

Integrative analysis of the molecular signature of target genes involved in the antitumor effects of cantharidin on hepatocellular carcinoma

BACKGROUND

Cantharidin (CTD) is the active ingredient of Chinese medicine, which has been traditionally used in multiple cancers treatment, especially in hepatocellular carcinoma (HCC). However, a comprehensive analysis of the CTD-related molecular mechanism is still necessary to understand its functions in HCC treatment. This study aimed to reveal the novel molecular targets and regulatory networks of CTD in HCC.

METHODS

A model of H22 tumour-bearing mice was constructed, and the function of CTD in tumour growth was evaluated. An integrated approach of CTD associated transcriptional profiling and biological systems analysis was used to identify key regulators involved in antitumour pathways. The identified differential expression patterns were supported by the results of Gene Ontology (GO) term and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analyse, and by protein-protein interaction (PPI) network construction. The relationships between gene expression and tumour immunity were evaluated using Tumour Immune Estimation Resource (TIMER). Prognostic value was analyzed with Kaplan-Meier plotter.

RESULTS

In the present study, the therapeutic effect of CTD on HCC was evaluated in vivo. We obtained the CTD-related transcriptional profiles, systematically and intuitively illustrated its possible pharmacological mechanisms in HCC through multiple targets and signalling pathways. These results revealed that the CTD-related differentially expressed genes were involved in autophagy, transcription factors (TFs) related transcriptional regulation, fatty acid metabolism and immune response in HCC. We found that MAPT, TOP2A, CENPF and MEFV were hub genes of CTD targets involved in autophagy regulation. Totally, 14 TFs have been confirmed to be critical for transcriptional regulation, and 33 TF targets were identified as the hub genes in transcriptional mis-regulation pathway in cancer. These TFs were associated with the immune response and immune cell infiltration. In addition, the downregulated genes were significantly enriched in metabolic regulation pathways, especially fatty acid metabolism after CTD treatment. Furthermore, the network of CTD associated miRNAs with these fatty acid metabolism-related targets was constructed in HCC.

CONCLUSIONS

Taken together, our results comprehensively elucidated that CTD could act on multiple targets in HCC therapy, affecting autophagy, transcriptional regulation, the immune response and fatty acid metabolism. Our results provide a foundation for the study of the molecular mechanistic of CTD and its clinical application in the treatment of HCC.

Hepatotoxic mechanism of cantharidin: insights and strategies for therapeutic intervention

Cantharidin (CTD), a natural compound derived from Mylabris, is widely used in traditional Oriental medicine for its potent anticancer properties. However, its clinical application is restricted due to its high toxicity, particularly towards the liver. This review provides a concise understanding of the hepatotoxic mechanisms of CTD and highlights novel therapeutic strategies to mitigate its toxicity while enhancing its anticancer efficacy. We systematically explore the molecular mechanisms underlying CTD-induced hepatotoxicity, focusing on the involvement of apoptotic and autophagic processes in hepatocyte injury. We further discuss the endogenous and exogenous pathways implicated in CTD-induced liver damage and potential therapeutic targets. This review also summarizes the structural modifications of CTD derivatives and their impact on anticancer activity. Additionally, we delve into the advancements in nanoparticle-based drug delivery systems that hold promise in overcoming the limitations of CTD derivatives. By offering valuable insights into the hepatotoxic mechanisms of CTD and outlining potential avenues for future research, this review contributes to the ongoing efforts to develop safer and more effective CTD-based therapies.

Charge-conversional click polyprodrug nanomedicine for targeted and synergistic cancer therapy

Polyprodrug nanomedicines hold great potential for combating tumors. However, the functionalization of polyprodrug nanomedicines to improve therapeutic efficacy is restricted by conventional polymerization methods. Herein, we fabricated a charge-conversional click polyprodrug nanomedicine system by metal-free azide-alkyne cycloaddition click polymerization (AACCP) for targeted and synergistic cancer therapy. Specifically, Pt(IV) prodrug-backboned diazide monomer, DMC prodrug-pendent diazide monomer, dialkyne-terminated PEG monomer and azide-modified folate were click polymerized to obtain the target polyprodrug (P1). P1 could self-assemble into nano-micelles (1-NM), where PEG was the hydrophilic shell with folate on the surface, Pt(IV) and DMC prodrugs as the hydrophobic core. Taking advantage of PEGylation and folate-mediated tumor cell targeting, 1-NM achieved prolonged blood circulation time and high tumor accumulation efficiency. Tumor acidic microenvironment-responsive cleavage and cascade activation of pendant DMC prodrug induced surface charge conversion of 1-NM from negative to positive, which promoted tumor penetration and cellular internalization of the remaining 1-NM. After internalization into tumor cells, the reduction-responsive activation of Pt(IV) prodrug to Pt(II) further showed synergetic effect with DMC for enhanced apoptosis. This first designed charge-conversional click polyprodrug nanomedicine exhibited targeted and synergistic efficacy to suppress tumor proliferation in living mice bearing human ovarian tumor model.

Inhibition of MZF1/c-MYC Axis by Cantharidin Impairs Cell Proliferation in Glioblastoma

Myeloid zinc finger 1 (MZF1), also known as zinc finger protein 42, is a zinc finger transcription factor, belonging to the Krüppel-like family that has been implicated in several types of malignancies, including glioblastoma multiforme (GBM). MZF1 is reportedly an oncogenic gene that promotes tumor progression. Moreover, higher expression of MZF1 has been associated with a worse overall survival rate among patients with GBM. Thus, MZF1 may be a promising target for therapeutic interventions. Cantharidin (CTD) has been traditionally used in Chinese medicine to induce apoptosis and inhibit cancer cell proliferation; however, the mechanism by which CTD inhibits cell proliferation remains unclear. In this study, we found that the expression of MZF1 was higher in GBM tissues than in adjacent normal tissues and low-grade gliomas. Additionally, the patient-derived GBM cells and GBM cell lines presented higher levels of MZF1 than normal human astrocytes. We demonstrated that CTD had greater anti-proliferative effects on GBM than a derivative of CTD, norcantharidin (NCTD). MZF1 expression was strongly suppressed by CTD treatment. Furthermore, MZF1 enhanced the proliferation of GBM cells and upregulated the expression of c-MYC, whereas these effects were reversed by CTD treatment. The results of our study suggest that CTD may be a promising therapeutic agent for patients with GBM and suggest a promising direction for further investigation.

Bioactive constituents of animal-derived traditional Chinese medicinal materials for breast cancer: opportunities and challenges

Breast cancer is globally the most common invasive cancer in women and remains one of the leading causes of cancer-related deaths. Surgery, radiotherapy, chemotherapy, immunotherapy, and endocrine therapy are currently the main treatments for this cancer type. However, some breast cancer patients are prone to drug resistance related to chemotherapy or immunotherapy, resulting in limited treatment efficacy. Consequently, traditional Chinese medicinal materials (TCMMs) as natural products have become an attractive source of novel drugs. In this review, we summarized the current knowledge on the active components of animal-derived TCMMs, including Ophiocordycepssinensis-derived cordycepin, the aqueous and ethanolic extracts of O.sinensis, norcantharidin (NCTD), Chansu, bee venom, deer antlers, Ostreagigas, and scorpion venom, with reference to marked anti-breast cancer effects due to regulating cell cycle arrest, proliferation, apoptosis, metastasis, and drug resistance. In future studies, the underlying mechanisms for the antitumor effects of these components need to be further investigated by utilizing multi-omics technologies. Furthermore, large-scale clinical trials are necessary to validate the efficacy of bioactive constituents alone or in combination with chemotherapeutic drugs for breast cancer treatment.

Combination of dasatinib and okadaic acid induces apoptosis and cell cycle arrest by targeting protein phosphatase PP2A in chronic myeloid leukemia cells

Chronic myeloid leukemia (CML) is a cancer type of the white blood cells and because of BCR-ABL translocation it results in increased tyrosine kinase activity. For this purpose, dasatinib is the second-generation tyrosine kinase inhibitor that is used for inhibition of BCR-ABL. Effectively and safetly, dasatinib has been used for imatinib-intolerant/resistant CML patients. Protein phosphatase 2A (PP2A) is the major serine/threonine phosphatase ensuring cellular homeostasis in cells and is associated with many cancer types including leukemias. In this study, we aimed to investigate the effects of dasatinib and okadaic acid (OA), either alone or in combination, on apoptosis and cell cycle arrest and dasatinib effect on enzyme activity and protein-level changes of PP2A in K562 cell line. The cytotoxic effects of dasatinib were evaluated by WST-1 analysis. Apoptosis was determined by Annexin V and Apo-Direct assays by flow cytometry. Cell cycle arrest analysis was performed for the investigation of the cytostatic effect. We also used OA as a PP2A inhibitor to assess apoptosis and cell cycle arrest changes in case of reducing the level of PP2A. PP2A enyzme activity and protein levels of PP2A were examined by serine/threonine phosphatase assay and Western blot analysis, respectively. Apoptosis was increased with dasatinib and OA combination. Cell cycle arrest was determined especially after OA treatment. The enzyme activity was decreased depending on time after dasatinib application. PP2A regulatory and catalytic subunit protein levels were decreased compared to control. Targeting the PP2A by dasatinib and OA has potential for CML treatment.

Magnesium demethylcantharidate inhibits hepatocellular carcinoma cell invasion and metastasis via activation transcription factor FOXO1

Hepatocellular carcinoma (HCC) is one of the most common malignant tumors in the world, develops rapidly and has a high mortality rate. Relapsed metastasis is the most important factor affecting prognosis and is also the main cause of death for patients with HCC. Cantharidin is a kind of folk medicine for malignant tumors in China. Because of its cytotoxicity, the application of cantharidin is very limited. Magnesium demethylcantharidate (MDC) is a derivative of cantharidin independently developed by our laboratory. Our results show that MDC has anticancer activity and exhibited lower toxicity than cantharidin. However, whether MDC affects the invasion and metastasis of HCC cells and the underlying molecular mechanisms remain obscure. Transwell and Matrigel assays showed that MDC could effectively inhibit the invasion and metastasis of the HCC cell lines SMMC-7721 and SK-Hep1 in a dose-dependent manner. Moreover, MDC significantly inhibited the expression of invasion and metastasis related proteins MMP-2 and MMP-9. In addition, our study found that MDC inhibited the invasion and metastasis of HCC cell lines SMMC-7721 and SK-Hep1 by activating transcription factor FOXO1. Interestingly, the combination of MDC and sorafenib significantly inhibited the invasion and metastasis of HCC cell lines SMMC-7721 and SK-Hep1 compared with the single drug treatment via the activated transcription factor FOXO1. Our work revealed that MDC obviously inhibited the invasion and metastasis of HCC cells, and suggested that MDC could be a potential candidate molecule against the invasion and metastasis of HCC.

Oxidative Stress Induced Cell Cycle Arrest: Potential Role of PRX-2 and GSTP-1 as Therapeutic Targets in Hepatocellular Carcinoma

BACKGROUND

The increasing incidence and mortality rate of HCC is a major concern, especially for developing countries of the world. Hence, extensive research is being carried out in order to explore new approaches for developing successful therapeutic strategies for HCC. The controversial role of oxidative stress in the prognosis and treatment of various diseases such as cancer has become the area of great interest and intrigue for many scientists throughout the world.

OBJECTIVE

We aim to investigate the role of induced oxidative stress on the suppression of HCC Huh-7 cancerous cells as therapeutic approach.

METHODS

Induction of oxidative stress via H2O2 treatment produced cell cytotoxicity in a dose dependent manner and also led to the over expression of GSTP-1 and PRX-2. The expression of GSTP-1 and PRX-2 was compared in HCC Huh-7 treated, untreated cells and normal hepatocytes using immunocytochemistry. Furthermore, the effects of oxidative stress on cell cycle arrest were also studied through flow cytometry.

RESULTS

Our study demonstrated the inhibition of cancer cell proliferation as a result of H2O2 induction by arresting the cell cycle at G2 phase.

CONCLUSION

The induction of oxidative stress could be a potential therapeutic approach for treating HCC in the future. GSTP-1 and PRX-2 can serve as substantial therapeutic targets for the treatment of HCC.

Tumor-targeted hyaluronic acid-mPEG modified nanostructured lipid carriers for cantharidin delivery: An in vivo and in vitro study

AIM

Cantharidin (CTD), the major component of the anti-cancer medicine obtained from Mylabris cichorii, exerts good inhibitory effects on several cancers, such as liver and breast cancer. However, owing to its toxicity, its oral administration can cause various adverse effects, limiting its clinical applications. Therefore, the development of a novel nano-drug delivery system for CTD would be highly beneficial.

METHODS

A nanostructured lipid carrier (NLC) was designed to actively target CTD to tumor cells using a hyaluronic acid (HA)-decorated copolymer (mPEG-NH2); the NLCs were called HA-mPEG-CTD-NLC. HA-mPEG was synthesized using amidation, and HA-mPEG-CTD-NLC was generated through ultrasonic emulsification in water. The mean hydrodynamic diameter of the particles was approximately 119.3 nm.

RESULTS

Pharmacokinetic studies revealed that the half-life of HA-mPEG-CTD-NLC and its area under the curve were higher than those of a CTD solution. Further, the plasma clearance rate of HA-mPEG-CTD-NLC was 0.41 times that of the CTD solution, implying a significantly prolonged drug retention time in vivo. Fluorescence in vivo endo-microscopy and optical in vivo imaging revealed that HA-mPEG-CTD-NLC had superior cytotoxicity and targeting efficacy against SMMC-7721 cells. An evaluation of the in vivo anti-tumor activity showed that HA-mPEG-CTD-NLC significantly inhibited tumor growth and prolonged survival in tumor-bearing mice, with a tumor inhibition rate of 65.96%.

CONCLUSIONS

Our results indicate that HA-mPEG-CTD-NLC may have great potential in liver cancer-targeted therapy.

Bi-Functional Peptides as a New Therapeutic Tool for Hepatocellular Carcinoma

Background: The interfering peptides that block protein–protein interactions have been receiving increasing attention as potential therapeutic tools. Methods: We measured the internalization and biological effect of four bi-functional tumor-penetrating and interfering peptides into primary hepatocytes isolated from three non-malignant and 11 hepatocellular carcinomas. Results: These peptides are internalized in malignant hepatocytes but not in non-malignant cells. Furthermore, the degree of peptide internalization correlated with receptor expression level and tumor aggressiveness levels. Importantly, penetration of the peptides iRGD-IP, LinTT1-IP, TT1-IP, and RPARPAR-IP induced apoptosis of the malignant hepatocytes without effect on non-malignant cells. Conclusion: Receptor expression levels correlated with the level of peptide internalization and aggressiveness of the tumor. This study highlights the potential to exploit the expression of tumor-penetrating peptide receptors as a predictive marker of liver tumor aggressiveness. These bi-functional peptides could be developed for personalized tumor treatment.

Breast cancer suppression by curcumin-naringenin-magnetic-nano-particles: In vitro and in vivo studies

BACKGROUND

The limitations of surgery, radiotherapy, and chemotherapy in cancer treatment and the increase in the application of nanomaterials in the field of biomedicine have promoted the use of nanomaterials in combination with radiotherapy for cancer treatment.

OBJECTIVE

To improve the efficiency of cancer treatment, curcumin-naringenin loaded dextran-coated magnetic nanoparticles (CUR-NAR-D-MNPs) were used as chemotherapy and in combination with radiotherapy to verify their effectiveness in treating tumors.

METHODS

CUR-NAR-D-MNPs were prepared and studied by several characterization methods. Median inhibitory concentration (IC50) and cellular toxicity were evaluated by 3-(4,5-dimethylthiazolyl-2)-2,5-diphenyltetrazolium bromide (MTT) assay. The cell death and radiosensitization were studied by acridine orange/ethidium bromide dual staining of MCF-7 human breast cancer cells.

RESULTS

CUR-NAR-D-MNPs induce apoptosis and inhibited cell proliferation through reactive oxygen species (ROS) generation. CUR-NAR-D-MNPs used alone had a certain therapeutic effect on tumors. CUR-NAR-D-MNPs plus radiotherapy significantly reduced the tumor volume and led to cell cycle arrest and induction of apoptosis through modulation of P53high, P21high, TNF-αlow, CD44low, and ROShigh signalingCONCLUSIONS:CUR-NAR-D-MNPs are effective in the treatment of tumors when combined with radiotherapy, and show radiosensitization effects against cancer proliferation in vitro and in vivo.

Protein Phosphatase 2A Activation Via ApoER2 in Trophoblasts Drives Preeclampsia in a Mouse Model of the Antiphospholipid Syndrome

[Figure: see text].

HDAC1-Dependent Repression of Markers of Hepatocytes and P21 Is Involved in Development of Pediatric Liver Cancer

BACKGROUND & AIMS

Epigenetic regulation of gene expression plays a critical role in the development of liver cancer; however, the molecular mechanisms of epigenetic-driven liver cancers are not well understood. The aims of this study were to examine molecular mechanisms that cause the dedifferentiation of hepatocytes into cancer cells in aggressive hepatoblastoma and test if the inhibition of these mechanisms inhibits tumor growth.

METHODS

We have analyzed CCAAT/Enhancer Binding Protein alpha (C/EBPα), Transcription factor Sp5, and histone deacetylase (HDAC)1 pathways from a large biobank of fresh hepatoblastoma (HBL) samples using high-pressure liquid chromatography-based examination of protein-protein complexes and have examined chromatin remodeling on the promoters of markers of hepatocytes and p21. The HDAC1 activity was inhibited in patient-derived xenograft models of HBL and in cultured hepatoblastoma cells and expression of HDAC1-dependent markers of hepatocytes was examined.

RESULTS

Analyses of a biobank showed that a significant portion of HBL patients have increased levels of an oncogenic de-phosphorylated-S190-C/EBPα, Sp5, and HDAC1 compared with amounts of these proteins in adjacent regions. We found that the oncogenic de-phosphorylated-S190-C/EBPα is created in aggressive HBL by protein phosphatase 2A, which is increased within the nucleus and dephosphorylates C/EBPα at Ser190. C/EBPα-HDAC1 and Sp5-HDAC1 complexes are abundant in hepatocytes, which dedifferentiate into cancer cells. Studies in HBL cells have shown that C/EBPα-HDAC1 and Sp5-HDAC1 complexes reduce markers of hepatocytes and p21 via repression of their promoters. Pharmacologic inhibition of C/EBPα-HDAC1 and Sp5-HDAC1 complexes by Suberoylanilide hydroxamic acid (SAHA) and small interfering RNA-mediated inhibition of HDAC1 increase expression of hepatocyte markers, p21, and inhibit proliferation of cancer cells.

CONCLUSIONS

HDAC1-mediated repression of markers of hepatocytes is an essential step for the development of HBL, providing background for generation of therapies for aggressive HBL by targeting HDAC1 activities.

JNK signaling as a target for anticancer therapy

The JNKs are members of mitogen-activated protein kinases (MAPK) which regulate many physiological processes including inflammatory responses, macrophages, cell proliferation, differentiation, survival, and death. It is increasingly clear that the continuous activation of JNKs has a role in cancer development and progression. Therefore, JNKs represent attractive oncogenic targets for cancer therapy using small molecule kinase inhibitors. Studies showed that the two major JNK proteins JNK1 and JNK2 have opposite functions in different types of cancers, which need more specification in the design of JNK inhibitors. Some of ATP- competitive and ATP non-competitive inhibitors have been developed and widely used in vitro, but this type of inhibitors lack selectivity and inhibits phosphorylation of all JNK substrates and may lead to cellular toxicity. In this review, we summarized and discussed the strategies of JNK binding inhibitors and the role of JNK signaling in the pathogenesis of different solid and hematological malignancies.

A disorder-related variant (E420K) of a PP2A-regulatory subunit (PPP2R5D) causes constitutively active AKT-mTOR signaling and uncoordinated cell growth

Functional genomic approaches have facilitated the discovery of rare genetic disorders and improved efforts to decipher their underlying etiology. PPP2R5D-related disorder is an early childhood onset condition characterized by intellectual disability, hypotonia, autism-spectrum disorder, macrocephaly, and dysmorphic features. The disorder is caused by de novo single nucleotide changes in PPP2R5D, which generate heterozygous dominant missense variants. PPP2R5D is known to encode a B'-type (B'56δ) regulatory subunit of a PP2A-serine/threonine phosphatase. To help elucidate the molecular mechanisms altered in PPP2R5D-related disorder, we used a CRISPR-single-base editor to generate HEK-293 cells in which a single transition (c.1258G>A) was introduced into one allele, precisely recapitulating a clinically relevant E420K variant. Unbiased quantitative proteomic and phosphoproteomic analyses of endogenously expressed proteins revealed heterozygous-dominant changes in kinase/phosphatase signaling. These data combined with orthogonal validation studies revealed a previously unrecognized interaction of PPP2R5D with AKT in human cells, leading to constitutively active AKT-mTOR signaling, increased cell size, and uncoordinated cellular growth in E420K-variant cells. Rapamycin reduced cell size and dose-dependently reduced RPS6 phosphorylation in E420K-variant cells, suggesting that inhibition of mTOR1 can suppress both the observed RPS6 hyperphosphorylation and increased cell size. Together, our findings provide a deeper understanding of PPP2R5D and insight into how the E420K-variant alters signaling networks influenced by PPP2R5D. Our comprehensive approach, which combines precise genome editing, isobaric tandem mass tag labeling of peptides generated from endogenously expressed proteins, and concurrent liquid chromatography-mass spectrometry (LC-MS³), also provides a roadmap that can be used to rapidly explore the etiologies of additional genetic disorders.

Sodium cantharidinate, a novel anti-pancreatic cancer agent that activates functional p53

Despite the use of many types of chemotherapies for pancreatic cancer, optimal efficacy has not been obtained so far. Pancreatic cancer shows a high incidence of TP53 mutations, inactivating its tumor suppressor activity. In this study, we identified sodium cantharidinate as a novel, potential anti-pancreatic cancer agent that activates p53 function. Sodium cantharidinate reduced the viability of pancreatic cancer cells, including the human primary pancreatic cancer cells, PANC-1, AsPC-1, SW1990 and BXPC-3, in a dose-dependent manner. Sodium cantharidinate induced apoptosis and DNA damage of pancreatic cancer cells. Furthermore, proteome-wide sequencing analysis detected a marked perturbation in p53 signaling pathway on PANC-1 cells upon sodium cantharidinate. Consistent with the previous results, sodium cantharidinate treatment decreased Bcl-2 and mitochondrial cytochrome-c protein expression, as well as phosphorylation of MDM2; meanwhile, it increased the levels of cleaved-caspase-3, cleaved-caspase-9, cleaved-PARP, Bax, and phosphorylated p53, thus inducing the apoptosis of pancreatic cancer cells. The p53-activating effect of sodium cantharidinate was strongly abrogated by treatment with TP53-targeting shRNA. Moreover, sodium cantharidinate inhibited neoplasm growth via the JAK2-STAT3 pathway, which was inhibited by shRNA-TP53 and triggered by combination with gemcitabine. Combination therapy indicated that sodium cantharidinate and gemcitabine synergistically reduced ex vivo and in vivo growth of pancreatic neoplasm. Further docking studies revealed the different binding fates of sodium cantharidinate to activate wild-type p53 function. Thus, sodium cantharidinate could be a potential agent with promising anti-pancreatic cancer efficacy.

The protective effect of L-glutamine against acute Cantharidin-induced Cardiotoxicity in the mice

Background

Cantharidin (CTD) is a compound which have the potential to be exploited as an antitumor drug, and it has been demonstrated antitumor effects in a variety of cancers. However, the use is limited due to its severe toxicity. It has reported that it can induce fatal cardiac arrhythmias. Fortunately, we found that L-glutamine can alleviate cardiac toxicity caused by cantharidin in mice.

Methods

To investigate the protective effect of L-glutamine, we used a high dose of cantharidin in mice to create a model of cardiotoxicity. In the experimental mice, glutamine was given orally half an hour before they were administrated with cantharidin. The mice of control group were intraperitoneally injected with DMSO solution. The general state of all mice, cardiac mass index, electrocardiogram change and biological markers were determined. Hematoxylin-eosin staining (HE staining) of heart tissue was carried out in each group to reflect the protective effect of glutamine. To investigate the mechanisms underlying the injury and cardio-protection, multiple oxidative stress indexes were determined and succinate dehydrogenase activity was evaluated.

Result

The results showed that L-glutamine (Gln) pretreatment reduced weight loss and mortality. It also decreased the biological markers (p < 0.05), improved electrocardiogram and histological changes that CTD induced cardiotoxicity in mice. Subsequently, the group pretreated with L-glutamine before CTD treatment increases in MDA but decreases in SOD and GSH, in comparison to the group treated with CTD alone. Besides, succinate dehydrogenase activity also was improved when L-glutamine was administrated before cantharidin compared to cantharidin.

Conclusions

This study provided evidence that L-glutamine could protect cardiac cells against the acute cantharidin-induced cardiotoxicity and the protective mechanism of glutamine may be related to the myocardial cell membrane or the tricarboxylic acid cycle in the mitochondria.

Effect of sodium cantharidinate/vitamin B6 injection on survival, liver function, immune function, and quality of life in patients with hepatocellular carcinoma: Protocol for a meta-analysis

BACKGROUND

Sodium cantharidinate/vitamin B6 (SC/VB6) injection, a famous insect-derived traditional Chinese medicine preparation, has been widely applied as a promising adjunctive drug for hepatocellular carcinoma (HCC). However, its exact clinical efficacy and safety is still not well investigated. In this study, we aimed to summarize the efficacy of SC/VB6 injection on survival, liver function, immune function, and quality of life (QoL) in patients with HCC through the meta-analysis.

METHODS

All available randomized controlled trials (RCTs) and high-quality prospective cohort studies that investigated the efficacy and safety of SC/VB6 for patients with HCC were searched from ten electronic databases including PubMed, Google Scholar, Cochrane Library, Excerpt Medica Database (Embase), Medline, Web of Science (WOS), Chinese Biomedical Literature Database (CBM), China National Knowledge Infrastructure (CNKI), China Scientific Journal Database (CSJ), and Wanfang Database. Papers in Chinese or English published from January 2000 to July 2020 will be included without any restrictions.Study selection and data extraction will be performed independently by 2 researchers. The clinical outcomes including overall survival (OS), QoL, liver function, immune function, and adverse events, were systematically evaluated. Review Manager 5.3 and Stata 14.0 were used for data analysis, and the quality of the clinical trials was also evaluated.

RESULTS

The results of this study will be published in a peer-reviewed journal, and provide a helpful evidence for clinicians to formulate the best postoperative adjuvant treatment strategy for HCC patients.

CONCLUSION

Our study will draw an objective conclusion of the efficacy of SC/VB6 on survival, liver function, immune function, and QoL in patients with HCC.

INPLASY REGISTRATION NUMBER

INPLASY202070121.

DNA unchained: two assays to discover and study inhibitors of the DNA clustering function of barrier-to-autointegration factor

The protein barrier-to-autointegration factor (BAF) and its interaction partners, the LEM (LAP2B, emerin, MAN1)-domain proteins, constitute a powerful cytoplasmic DNA defense mechanism. Invading DNA molecules are quickly bound by the BAF system and trapped in membrane compartments. This decreases the nuclear uptake of DNA from the cytoplasm. Inhibition of the BAF system is therefore expected to enhance the efficacy of non-viral DNA transfection agents. In this study, we introduced a protocol for the recombinant expression of soluble BAF and developed two ELISA-type assays to discover small molecule inhibitors of BAF-dependent DNA retention by high throughput screening (HTS). The proton pump inhibitor rabeprazole as well as three compounds of the Maybridge library were identified as inhibitors of the LEM-BAF-DNA interaction chain. The inhibition was based on adduct formation with BAF cysteine residues. An enhancing effect of the compounds on cell culture transfection, however, was not observed, which may be attributed to the reducing environment of the cytoplasm that prevents the adduct formation with BAF cysteine residues. The novel assays developed here can provide new tools to further study the biological functions of the BAF system, and may lead to the identification of suitable BAF inhibitors in future HTS campaigns.

Anticancer Attributes of Cantharidin: Involved Molecular Mechanisms and Pathways

Cancer is a preeminent threat to the human race, causing millions of deaths each year on the Earth. Traditionally, natural compounds are deemed promising agents for cancer treatment. Cantharidin (CTD)-a terpenoid isolated from blister beetles-has been used extensively in traditional Chinese medicines for healing various maladies and cancer. CTD has been proven to be protein phosphatase 2A (PP2A) and heat shock transcription factor 1 (HSF-1) inhibitor, which can be potential targets for its anticancer activity. Albeit, it harbors some toxicities, its immense anticancer potential cannot be overlooked, as the cancer-specific delivery of CTD could help to rescue its lethal effects. Furthermore, several derivatives have been designed to weaken its toxicity. In light of extensive research, the antitumor activity of CTD is evident in both in vitro as well as in vivo cancer models. CTD has also proven efficacious in combination with chemotherapy and radiotherapy and it can also target some drug-resistant cancer cells. This mini-review endeavors to interpret and summarize recent information about CTD anticancer potential and underlying molecular mechanisms. The pertinent anticancer strength of CTD could be employed to develop an effective anticarcinogenic drug.

RNA-sequencing-based transcriptome analysis of cantharidin-induced myocardial injury

The cardiotoxicity of cantharidin has been well characterized, but the understanding of the underlying mechanism(s) is incomplete. To more fully understand the differentially expressed genes (DEGs) in cantharidin-induced myocardial injury, Sprague-Dawley rats were exposed to cantharidin (1.34 mg/kg or 2.67 mg/kg) for 24 h and then the heart was sampled for pathologic changes analysis and RNA-sequencing-based transcriptomic profiling. In addition, serum troponin T (TN-T) levels were also tested using the enzyme-linked immunosorbent assay method. The results showed that cantharidin could cause myocardial damage and elevated serum TN-T levels. The genes with a fold change ≥2 were considered as DEGs and we found 38 DEGs that were mainly enriched in eight pathways revealed by Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis. The cellular component of gene ontology analysis showed that the DEGs were mostly enriched in the extracellular matrix. In conclusion, our present study demonstrated that cantharidin induces myocardial injury by multiple modulatory mechanisms, which provide new insights for further study of the pathophysiologic mechanism of cantharidin-induced myocardial injury.

Cantharidic acid induces apoptosis in human nasopharyngeal carcinoma cells through p38-mediated upregulation of caspase activation

Cantharidic acid (CA) is the hydrolysis product of the acid anhydride cantharidin, which is a natural toxin secreted by several species of blister beetles. Several studies have indicated that as an inhibitor of protein phosphatase 2 (PP2A), CA induces apoptosis in various human cancer cells. However, the effect of CA on human nasopharyngeal carcinoma (NPC) cells and the underlying pathways have not been addressed. In our current study, we tested the hypothesis that CA treatment reduces the viability of human NPC cells (HONE-1, NPC-39, and NPC-BM) by inducing apoptosis. Results indicated that CA markedly reduced cell viability, which was revealed by the upregulation of caspase activation in extrinsic and intrinsic apoptosis pathways as well as the upregulation of extracellular-signal-regulated kinase 1/2 (ERK1/2), p38, and c-Jun N-terminal kinase 1/2 (JNK1/2) pathways. Coadministration of a p38 inhibitor (SB203580) with CA abolished the activation of caspase proteins. These findings indicated that CA treatment leads to apoptosis in human NPC cells through the upregulation of caspase activation, mediated particularly by the p38 pathway. Hence, CA is a promising therapeutic agent for human NPC.

Zebrafish ambra1a and ambra1b Silencing Affect Heart Development

In zebrafish, two paralogous genes, activating molecule in beclin-1 (BECN1)-regulated autophagy ambra1a and ambra1b, both required for the autophagic process and during development, encode the protein AMBRA1, a positive regulator of early steps of autophagosome formation. As transcripts for both genes are expressed during embryogenesis in the heart region, in this work, we investigated the effects of ambra1a and ambra1b knockdown on heart development by means of morpholino oligonucleotides (MOs). Silencing of the two proteins by MOs directed against the ATG translation initiation codon affects cardiac morphogenesis, resulting in a small, string-like heart with pericardial edema, whereas treatment with splice-blocking MOs does not lead to overt cardiac phenotypes, thus revealing the relevance of maternally supplied ambra1 transcripts for heart development. Co-injection of both ATG-MOs determines a more severe cardiac phenotype, with prominent pericardial edema. Whole-mount in situ hybridization (WMISH) for myosin light chain 7 (myl7), as well as ambra1 ATG-MO microinjection in zebrafish transgenic line expressing green fluorescent protein in the heart, revealed defects with the heart jogging process followed by imperfect cardiac looping. Moreover, WMISH of homeodomain transcription factor 2 isoform c (pitx2c) transcripts showed both bilateral and reversed pitx2c expression in morphants. The morphants' cardiac phenotypes were effectively rescued by co-injection of MOs with human AMBRA1 (hAMBRA1) messenger RNA (mRNA), pointing at the conservation of Ambra1 functions during evolution. Co-injections of ambra1 ATG-MOs with a hAMBRA1 mRNA mutated in the protein phosphatase 2a (PP2A) binding sites (hAMBRA1PXP) were not able to rescue the cardiac phenotypes, at the difference from wild-type hAMBRA1 mRNA, and treatment of zebrafish embryos with the specific PP2A inhibitor cantharidin resulted in similar developmental cardiac defects. These results suggest a critical role for AMBRA1 in vertebrate heart development, likely involving the binding site for the PP2A phosphatase.

Draft Genome of a Blister Beetle Mylabris aulica

Mylabris aulica is a widely distributed blister beetle of the Meloidae family. It has the ability to synthesize a potent defensive secretion that includes cantharidin, a toxic compound used to treat many major illnesses. However, owing to the lack of genetic studies on cantharidin biosynthesis in M. aulica, the commercial use of this species is less extensive than that of other blister beetle species in China. This study reports a draft assembly and possible genes and pathways related to cantharidin biosynthesis for the M. aulica blister beetle using nanopore sequencing data. The draft genome assembly size was 288.5 Mb with a 467.8 Kb N50, and a repeat content of 50.62%. An integrated gene finding pipeline performed for assembly obtained 16,500 protein coding genes. Benchmarking universal single-copy orthologs assessment showed that this gene set included 94.4% complete Insecta universal single-copy orthologs. Over 99% of these genes were assigned functional annotations in the gene ontology, Kyoto Encyclopedia of Genes and Genomes, or Genbank non-redundant databases. Comparative genomic analysis showed that the completeness and continuity of our assembly was better than those of Hycleus cichorii and Hycleus phaleratus blister beetle genomes. The analysis of homologous orthologous genes and inference from evolutionary history imply that the Mylabris and Hycleus genera are genetically close, have a similar genetic background, and have differentiated within one million years. This M. aulica genome assembly provides a valuable resource for future blister beetle studies and will contribute to cantharidin biosynthesis.

Methyl-Cantharidimide Inhibits Growth of Human Hepatocellular Carcinoma Cells by Inducing Cell Cycle Arrest and Promoting Apoptosis

Methyl-Cantharidimide (MCA) is a derivative of cantharidin which has potential anticancer activity. This study investigates the effect of MCA on the growth and metastasis of human hepatocellular carcinoma (HCC) cells. Human HCC HepG2 and Hep3B2.1-7 cells, and normal hepatocytes (L02) were treated with a series of concentrations of MCA. The inhibition ability of these cells was examined by CCK-8 assay. Cell cycle and cell apoptosis were determined using Flow Cytometry. The effect of MCA on cell migration and invasion was evaluated through scratch wound healing and transwell migration assays. Furthermore, Western blot was used to evaluate biomarkers associated with cell cycle and apoptosis. It was found that: (i) MCA inhibited cell proliferation in HCC cells in a dose- and time-dependent manner, especially in HepG2 cells; (ii) MCA arrested HCC cells in G-1 phase cell cycle; (iii) MCA induced HCC cells apoptosis; (iv) MCA inhibited the migration ability of HCC cells; and (v) MCA treatment significantly increased cleaved-caspase3 and decreased NF-κB protein in HCC cells. These results suggest that MCA has cytotoxic effect on HCC cells by inducing cell cycle arrest and promoting apoptosis. MCA could be developed as an previous anticancer drug for the treatment of human hepatocellular carcinoma.

Hypoxia Activates the PTHrP -MEF2C Pathway to Attenuate Hypertrophy in Mesenchymal Stem Cell Derived Cartilage

Articular cartilage lacks an intrinsic repair capacity and due to the ability of mesenchymal stem cells (MSCs) to differentiate into chondrocytes, MSCs have been touted as a cellular source to regenerate damaged cartilage. However, a number of prevailing concerns for such a treatment remain. Generally, administration of MSCs into a cartilage defect results in poor regeneration of the damaged cartilage with the repaired cartilage consisting primarily of fibro-cartilage rather than hyaline cartilage. Methods that improve the chondrogenic potential of transplanted MSCs in vivo may be advantageous. In addition, the proclivity of MSC-derived cartilage to undergo hypertrophic differentiation or form bone in vivo also remains a clinical concern. If MSC-derived cartilage was to undergo hypertrophic differentiation in vivo, this would be deleterious in a clinical setting. This study focuses on establishing a mechanism of action by which hypoxia or low oxygen tension can be used to both enhance chondrogenesis and attenuate hypertrophic differentiation of both MSC and ATDC5 derived chondrocytes. Having elucidated a novel mechanism of action, the subsequent goals of this study were to develop an in vitro culture regime to mimic the beneficial effects of physiological low oxygen tension in a normoxic environment.

Selective activation of tumor-suppressive MAPKP signaling pathway by triptonide effectively inhibits pancreatic cancer cell tumorigenicity and tumor growth

The mitogen-activated protein kinase (MAPK, 1K) family members ERK, JNK, and p38 play a divergent role in either promoting tumorigenesis or tumor-suppression. Activation of ERK and JNK promotes tumorigenesis; whereas, escalation of p38 inhibits carcinogenesis. As these three MAPK members are controlled by the common up-stream MAPK signaling proteins which consist of MAPK kinases (2K) and MAPK kinase kinases (3K), how to selectively actuate tumor-suppressive p38, not concurrently stimulate tumorigenic ERK and JNK, in cancer cells is a challenge for cancer researchers, and a new opportunity for novel anti-cancer drug discovery. Using human pancreatic cancer cells and xenograft mice as models, we found that a small molecule triptonide first discerningly activated the up-stream MAPK kinase kinase MEKK4, not the other two 3K members ASK1 and GADD45; and then selectively actuated the middle stream MAPK kinase MKK4, not the other two 2K members MKK3 and MKK6; and followed by activation of the MAPK member p38, not the other two members ERK and JNK. These data suggest that triptonide is a selective MEKK4-MKK4-p38 axis agonist. Consequently, selective activation of the MEKK4-MKK4-p38 signaling axis by triptonide activated tumor suppressor p21 and inhibited CDK3 expression, resulting in cancer cell cycle arrest at G2/M phase and marked inhibition of pancreatic cancer cell tumorigenic capability in vitro and tumor growth in xenograft mice. Our findings support the notion that selective activation of tumor-suppressive MEKK4-MKK4-p38-p21signaling pathway by triptonide is a new approach for pancreatic cancer therapy, providing a new drug candidate for development of novel anti-cancer therapeutics.

The Crg1 N-Terminus Is Essential for Methyltransferase Activity and Cantharidin Resistance in Saccharomyces cerevisiae

Crg1 is an S-adenosylmethionine (SAM)-dependent methyltransferase required for cantharidin resistance in yeast. Crg1 has a well-characterized methyltransferase domain that inactivates cantharidin by methylation. However, the remaining part of the Crg1 protein is yet to be functionally characterized. In this study, we identified an essential role of the N-terminus of Crg1 in methyltransferase activity and cantharidin resistance. Yeast cells lacking 41 residues of the N-terminus of Crg1 ( crg1ΔN) showed hypersensitivity to cantharidin as same as the null mutant, crg1. The mass spectrometry-based biochemical enzyme assay revealed a loss of methyltransferase activity in Crg1ΔN, which justifies the loss of cantharidin resistance, as well. The subcellular distribution of Crg1ΔN-daGFP showed cytoplasmic aggregates, whereas wild-type Crg1-daGFP was distributed normally in the cytoplasm. Interestingly, the Crg1-methyltransferase domain point mutants (D44A, D67A, and E105A/D108A) also showed the same cytoplasmic aggregates as Crg1ΔN-daGFP. In silico prediction of the tertiary structures of these mutants indicated an altered protein conformation. Altogether, these observations suggest that the N-terminal truncation, as well as the point mutations in the methyltransferase domain, alters the native folding of Crg1 methyltransferase, resulting in a loss of enzyme activity. Furthermore, the crg1ΔN mutant showed the same phenotypes as the crg1 null mutant in the presence of cantharidin, i.e., lethal cell growth, PE auxotrophy, temperature sensitivity, endoplasmic reticulum stress, GPI anchor missorting, and cell wall damage. Overall, this study identifies an essential role of the N-terminus of Crg1 in methyltransferase activity and cantharidin resistance.

Disodium Cantharidinate and Vitamin B6 Injection Adjunct with Platinum-Based Chemotherapy for the Treatment of Advanced Non-Small-Cell Lung Cancer: A Meta-Analysis

Purpose

Disodium cantharidinate and vitamin B6 (DCVB6) injection is effective and widely used for the clinical treatment of non-small-cell lung cancer (NSCLC). This meta-analysis aimed to provide evidence-based medical data for clinical treatment with DCVB6 injection.

Methods

We searched 7 medical databases up to January 2018 for all randomized controlled trials (RCTs) based on DCVB6 injection combined with chemotherapy in patients with NSCLC. A manual search in relevant journals and of relevant literature on other websites was also performed. Data extraction and quality assessment were conducted independently by two reviewers. Subsequently, a meta-analysis was conducted using RevMan 5.3 software. Pooled risk ratio (RR) with 95% confidence interval (CI) was used to evaluate dichotomous and continuous outcomes, respectively. The PROSPERO ID was CRD42018086377.

Results

A total of 19 RCTs were included. The results of the meta-analysis indicated that the DCVB6 injection combined with chemotherapy was superior to chemotherapy alone regarding objective response rate (RR=1.58, 95% CI 1.40-1.79), Karnofsky performance score (RR=1.68, 95% CI 1.42-1.99), clinical symptom (RR=1.68, 95% CI 1.44-1.96), white blood cell toxicity (RR=0.36, 95% CI 0.27-0.49), platelet toxicity (RR=0.46, 95% CI 0.33-0.63), and vomiting (RR=0.50, 95% CI 0.37-0.67).

Conclusions

The current evidence suggests that DCVB6 injection combined with chemotherapy could increase objective response rate and Karnofsky performance score, improve clinical symptoms, and reduce side effects caused by chemotherapy in patients with NSCLC. However, these results should be carefully interpreted due to the low-quality methodology and the small sample sizes of the trials, and our conclusions should be verified by high-quality, large-scale, double-blinded RCTs.

Heat Oscillations Driven by the Embryonic Cell Cycle Reveal the Energetic Costs of Signaling

All living systems function out of equilibrium and exchange energy in the form of heat with their environment. Thus, heat flow can inform on the energetic costs of cellular processes, which are largely unknown. Here, we have repurposed an isothermal calorimeter to measure heat flow between developing zebrafish embryos and the surrounding medium. Heat flow increased over time with cell number. Unexpectedly, a prominent oscillatory component of the heat flow, with periods matching the synchronous early reductive cleavage divisions, persisted even when DNA synthesis and mitosis were blocked by inhibitors. Instead, the heat flow oscillations were driven by the phosphorylation and dephosphorylation reactions catalyzed by the cell-cycle oscillator, the biochemical network controlling mitotic entry and exit. We propose that the high energetic cost of cell-cycle signaling reflects the significant thermodynamic burden of imposing accurate and robust timing on cell proliferation during development.

The natural anticancer agent cantharidin alters GPI-anchored protein sorting by targeting Cdc1-mediated remodeling in endoplasmic reticulum

Cantharidin (CTD) is a potent anticancer small molecule produced by several species of blister beetle. It has been a traditional medicine for the management of warts and tumors for many decades. CTD suppresses tumor growth by inducing apoptosis, cell cycle arrest, and DNA damage and inhibits protein phosphatase 2 phosphatase activator (PP2A) and protein phosphatase 1 (PP1). CTD also alters lipid homeostasis, cell wall integrity, endocytosis, adhesion, and invasion in yeast cells. In this study, we identified additional molecular targets of CTD using a Saccharomyces cerevisiae strain that expresses a cantharidin resistance gene (CRG1), encoding a SAM-dependent methyltransferase that methylates and inactivates CTD. We found that CTD specifically affects phosphatidylethanolamine (PE)-associated functions that can be rescued by supplementing the growth media with ethanolamine (ETA). CTD also perturbed endoplasmic reticulum (ER) homeostasis and cell wall integrity by altering the sorting of glycosylphosphatidylinositol (GPI)-anchored proteins. A CTD-dependent genetic interaction profile of CRG1 revealed that the activity of the lipid phosphatase cell division control protein 1 (Cdc1) in GPI-anchor remodeling is the key target of CTD, independently of PP2A and PP1 activities. Moreover, experiments with human cells further suggested that CTD functions through a conserved mechanism in higher eukaryotes. Altogether, we conclude that CTD induces cytotoxicity by targeting Cdc1 activity in GPI-anchor remodeling in the ER.

Redox inhibition of protein phosphatase PP2A: Potential implications in oncogenesis and its progression

Cellular processes are dictated by the active signaling of proteins relaying messages to regulate cell proliferation, apoptosis, signal transduction and cell communications. An intricate web of protein kinases and phosphatases are critical to the proper transmission of signals across such cascades. By governing 30–50% of all protein dephosphorylation in the cell, with prominent substrate proteins being key regulators of signaling cascades, the phosphatase PP2A has emerged as a celebrated player in various developmental and tumorigenic pathways, thereby posing as an attractive target for therapeutic intervention in various pathologies wherein its activity is deregulated. This review is mainly focused on refreshing our understanding of the structural and functional complexity that cocoons the PP2A phosphatase, and its expression in cancers. Additionally, we focus on its physiological regulation as well as into recent advents and strategies that have shown promise in countering the deregulation of the phosphatase through its targeted reactivation. Finally, we dwell upon one of the key regulators of PP2A in cancer cells-cellular redox status-its multifarious nature, and its integration into the reactome of PP2A, highlighting some of the significant impacts that ROS can inflict on the structural modifications and functional aspect of PP2A.

Efficacy and safety of sodium cantharidinate and vitamin B6 injection for the treatment of digestive system neoplasms: a meta-analysis of randomized controlled trials

Objective

To systematically evaluate the efficacy and safety of sodium cantharidinate and vitamin B6 (SC/B6) combined with conventional medical treatment (CMT) for the treatment of patients with advanced digestive system neoplasms (DSNs).

Methods

The Cochrane Library, Embase, PubMed, Web of Science, Chinese Scientific Journal Database (VIP), China National Knowledge Infrastructure, and Wanfang databases were searched for clinical trials using SC/B6 for DSNs. Outcome measures, including therapeutic efficacy, quality of life (QoL), and adverse events, were extracted and systematically evaluated.

Results

Data from 24 trials including 1,825 advanced DSN patients were included. Compared with CMT alone, its combination with SC/B6 significantly improved the patients’ overall response rate (OR =2.25, 95% CI =1.83–2.76, P<0.00001), disease control rate (OR =2.41, 95% CI =1.85–3.15, P<0.00001), and QoL improvement rate (OR =2.75, 95% CI =2.13–3.55, P<0.00001). Moreover, adverse events caused by chemotherapy, including leukopenia, nausea and vomiting, gastrointestinal side effects, hepatotoxicity, diarrhea, transaminase disorder, myelosuppression, anorexia, and anemia, were significantly alleviated (P<0.05) when SC/B6 was applied to DSN patients. Nephrotoxicity, thrombocytopenia, hand-foot syndrome, and oral mucositis were not significantly alleviated in patients receiving combination therapy (P>0.05).

Conclusion

The combination of SC/B6 and CMT is more effective in treating DSNs than CMT alone. This combination alleviates the adverse effects associated with chemotherapy and improves the QoL of DSN patients, and its application in the clinic is worth promoting.

γ-Tocotrienol-Inhibited Cell Proliferation of Human Gastric Cancer by Regulation of Nuclear Factor-κB Activity

γ-Tocotrienol (γ-T3) exhibits the activity of anticancer via regulating cell signaling pathways. Nuclear factor-κB (NF-κB), one of the crucial pro-inflammatory factors, is involved in the regulation of cell proliferation, apoptosis, invasion, and migration of tumor. In the present study, NF-κB activity inhibited by γ-T3 was investigated in gastric cancer cells. Cell proliferation, NF-κB activity, active protein phosphatase type 2A (PP2A), and ataxia-telangiectasia mutated (ATM) protein were explored using 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyl tetrazolium bromide (MTT), methylene blue, enzyme-linked immunosorbent assay (ELISA), malachite green, luciferase, and Western blotting assays. The effects of γ-T3 on tumor growth and the expression of NF-κB and PP2A proteins were also further examined by implanting human gastric cancer cells in a BALB/c nude mouse model. The results showed that γ-T3 significantly inhibited the cell proliferation and attenuated the NF-κB activity in vitro and in vivo. γ-T3 dramatically increased PP2A activity and protein expression, which suppressed ATM phosphorylation and its translocation to the cytoplasm in gastric cancer cells. Thus, our findings may provide mechanistic insight into effects of γ-T3 on the regulation of NF-κB activity by a PP2A-dependent mechanism and suggest that PP2A may serve as a molecular target for a potential chemopreventive agent.

The combination of cantharidin and antiangiogenic therapeutics presents additive antitumor effects against pancreatic cancer

Cantharidin, one of the active components of mylabris, is believed to have antitumor activity. Cantharidin selectively inhibits protein phosphatase 2A (PP2A), which can repress multiple oncogenic kinases (ERK, JNK, PKC, and NF-κB). Researches in vitro have shown that cantharidin suppresses cell viability and metastasis in pancreatic cancer cells. This study aims to investigate the effects of cantharidin on pancreatic cancer xenografts in vivo. Xenograft models were established using cells stably expressing luciferase. Xenograft growth was evaluated by living imaging. Gene expression was determined using a microarray, real-time PCR, a RayBiotech antibody array, and the Milliplex assay. Surprisingly, cantharidin significantly accelerated xenograft growth. Living imaging showed a rapid distribution of D-luciferin in cantharidin-treated xenografts, suggesting a rich blood supply. Immunohistochemistry confirmed increased angiogenesis. Microarray and antibody array identified upregulated proangiogenic and downregulated antiangiogenic factors. The Milliplex assay suggested elevated secretion of IL-6, IL-8, TNF-α, and VEGF. Inhibitors of ERK, JNK, PKC, and NF-κB pathway attenuated the cantharidin-induced changes to proangiogenic gene expression. PKC pathway-inhibiting tamoxifen or antiangiogenic therapeutics, including Ginsenoside Rg3, bevacizumab, Apatinib, and Endostar, antagonized the proangiogenic effect of cantharidin or its derivatives. These regimens presented remarkable additive antitumor effects in vivo. Although cantharidin presents antitumor effects in vitro and has been applied in clinical practice, we revealed an unfavorable proangiogenic side effect. We recommend that the clinical application of cantharidin should be performed on the premise of antivascularization therapy.

Inhibition of Protein Phosphatase 2A Sensitizes Mucoepidermoid Carcinoma to Chemotherapy via the PI3K-AKT Pathway in Response to Insulin Stimulus

BACKGROUND/AIMS

Protein phosphatase 2A (PP2A) is a ubiquitous serine/threonine phosphatase that mediates cell cycle regulation and metabolism. Mounting evidence has indicated that PP2A inhibition exhibits considerable anticancer potency in multiple types of human cancers. However, the efficacy of PP2A inhibition remains unexplored in mucoepidermoid carcinoma (MEC), especially in locally advanced and metastatic cases with limited systemic treatment. In this study, we demonstrated the therapeutic potency of LB100 in mucoepidermoid carcinoma.

METHODS

In this study, the expression of PP2A was evaluated using immunohistochemical (IHC) staining. The effects associated with LB100 alone and in combination with cisplatin for the treatment of mucoepidermoid carcinoma were investigated both in vitro, regarding metabolism, proliferation, and migration, and in vivo in a mucoepidermoid carcinoma xenograft model. In addition, with LB100 treatment and in response to an insulin stimulus, the expression levels and phosphorylation levels of targets in the PI3K-AKT pathway were determined using western blot analysis and immunoblotting.

RESULTS

The expression of protein phosphatase 2A was significantly upregulated in the clinical specimens of high-grade MECs compared with those of low-/medium-grade MECs and normal controls. In this article, we report that a small molecule PP2A inhibitor, LB100, decreased cellular viability and glycolytic activity and induced G2/M cell cycle arrest. Importantly, LB100 enhanced the efficacy of cisplatin in mucoepidermoid carcinoma cells both in vitro and in vivo. PP2A inhibition by LB100 increased the phosphorylation of insulin receptor substrate 1(IRS-1) on serine residues, downregulated the expression of phosphatidylinositol 3-kinase (PI3K) p110 alpha subunit and dephosphorylated AKT at Ser473 and Thr308 in mucoepidermoid carcinoma cells in response to insulin stimulus.

CONCLUSION

These results highlight the translational potential of PP2A inhibition to synergize with cisplatin in mucoepidermoid carcinoma treatment.

The radiotherapy-sensitization effect of cantharidin: Mechanisms involving cell cycle regulation, enhanced DNA damage, and inhibited DNA damage repair

BACKGROUND

Cantharidin is an inhibitor of protein phosphatase 2 A (PP2A), and has been frequently used in clinical practice. In our previous study, we proved that cantharidin could arrest cell cycle in G2/M phase. Since cells at G2/M phase are sensitive to radiotherapy, in the present study, we investigated the radiotherapy-sesitization effect of cantharidin and the potential mechanisms involved.

METHODS

Cell growth was determined by MTT assay. Cell cycle was evaluated by flow cytometry. DNA damage was visualized by phospho-Histone H2A.X staining. Expression of mRNA was tested by microarray assay and real-time PCR. Clinical information and RNA-Seq expression data were derived from The Cancer Genome Atlas (TCGA) pancreatic cancer cohort. Survival analysis was obtained by Kaplan-Meier estimates.

RESULTS

Cantharidin strengthened the growth inhibition effect of irradiation. Cantharidin drove pancreatic cancer cells out of quiescent G0/G1 phase and arrested cell cycle in G2/M phase. As a result, cantharidin strengthened DNA damage which was induced by irradiation. Moreover, cantharidin repressed expressions of several genes participating in DNA damage repair, including UBE2T, RPA1, GTF2HH5, LIG1, POLD3, RMI2, XRCC1, PRKDC, FANC1, FAAP100, RAD50, RAD51D, RAD51B and DMC1, through JNK, ERK, PKC, p38 and/or NF-κB pathway dependent manners. Among these genes, worse overall survival for pancreatic cancer patients were associated with high mRNA expressions of POLD3, RMI2, PRKDC, FANC1, RAD50 and RAD51B, all of which could be down-regulated by cantharidin.

CONCLUSION

Cantharidin can sensitize pancreatic cancer cells to radiotherapy. Multiple mechanisms, including cell cycle regulation, enhanced DNA damage, and inhibited DNA damage repair, may be involved.

Cantharidin Inhibits Anti-Apoptotic Bcl-2 Family Proteins and Induces Apoptosis in Human Osteosarcoma Cell Lines MG-63 and MNNG/HOS via Mitochondria-Dependent Pathway

Background

Cantharidin (CTD) is one of the major active ingredients of blister beetles and has significant antitumor activity in many cancer cell lines. The aim of our study was to evaluate the effect of CTD on the apoptosis of human osteosarcoma cells MG-63 and MNNG/HOS, and to explore the possible molecular mechanism.

Material/Methods

Osteosarcoma cells MG-63 and MNNG/HOS were treated with varying concentrations of CTD. The proliferation inhibition of cells was detected by MTS. Flow cytometry and Hoechst 33258 staining were used to determine cell cycle arrest and apoptosis, and apoptosis-related protein levels were analyzed by Western blotting.

Results

Our current findings suggest that CTD could inhibit the proliferation of these 2 osteosarcoma cells. The cells treated with CTD showed an obvious apoptotic morphology, and CTD promoted cells apoptosis in a dose-dependent manner. In addition, cantharidin-induced apoptosis was accompanied by increased expression of Bax and PARP and decreased expression of Bcl-2, p-Akt, and p-Cdc2.

Conclusions

CTD accelerates the apoptosis of MG-63 and MNNG/HOS cells in a concentration-dependent manner through the mitochondria-dependent pathway, suggesting that use of CTD is a novel approach for the treatment of osteosarcoma.

KIAA1199 promotes metastasis of colorectal cancer cells via microtubule destabilization regulated by a PP2A/stathmin pathway

Tumor metastasis is the main cause of death in advanced colorectal cancer. Our previous research showed that upregulation of KIAA1199 predicted poorer outcomes, and promoted cell motility and tumor metastasis in colorectal cancer, with the mechanisms not being fully elucidated. Here, we demonstrate that silencing of KIAA1199 results in reduced tumor metastasis in the orthotopic transplantation tumor model of colorectal cancer. Importantly, we find that KIAA1199 interacts with protein phosphatase 2A (PP2A) through the C-terminal domain and increases phosphatase activity of PP2A, which is essential for KIAA1199-mediated cell motility. Moreover, we identify stathmin, a microtubule-destabilizing protein, as a downstream of KIAA1199-PP2A complex. KIAA1199-induced dephosphorylation of stathmin results in microtubule destabilization and leads to enhanced cell motility. Furthermore, a microtubule-stabilizing drug paclitaxel could prevent KIAA1199-induced microtubule destabilization, and inhibit cell migration and invasion in vitro and tumor metastasis in vivo in colorectal cancer. Collectively, our study reveals that KIAA1199 promotes metastasis of colorectal cancer cells via microtubule destabilization regulated by a PP2A/stathmin pathway, and suggests that KIAA1199 may be a promising target for preventing metastasis in colorectal cancer.

Cantharidin inhibits melanoma cell proliferation via the miR‑21‑mediated PTEN pathway

Cantharidin (CTD) is an active component isolated from the blister beetle that has been demonstrated to exert antitumor effects on multiple types of cancer. The current study aimed to investigate whether the potential inhibitory effects of CTD exist in human melanoma cells and to assess the underlying antitumor mechanisms of CTD. Using the Cell Counting Kit‑8 assay, it was demonstrated that CTD treatment reduced A375 cell proliferation significantly in a dose‑dependent manner. The colony formation assay demonstrated that CTD treatment could decrease the number of A375 cell colonies. Using subcutaneous xenograft tumor models, it was also demonstrated that CTD retarded solid tumor growth significantly. Furthermore, CTD treatment could induce A375 cell apoptosis, as detected by Annexin V‑fluorescein isothiocyanate/propidium iodide staining and western blot analysis. Notably, CTD treatment reduced microRNA (miR)‑21 expression and enhanced phosphatase and tensin homolog (PTEN) protein expression levels in A375 cells. Furthermore, overexpressing miR‑21 in A375 cells with the miR‑21 agomir blocked the antitumor effect of CTD both in vitro and in vivo. Finally, it was demonstrated that the inhibitory effects of CTD on A375 cells may be regulated by attenuating miR‑21‑mediated PTEN suppression. Based on these observations, it was suggested that CTD be used as a novel anti‑proliferation agent of human melanoma via targeting the miR‑21‑PTEN signaling pathway.

Targeting PP2A in cancer: Combination therapies

The serine/threonine phosphatase PP2A regulates a vast portion of the phosphoproteome including pathways involved in apoptosis, proliferation and DNA damage response and PP2A inactivation is a vital step in malignant transformation. Many groups have explored the therapeutic venue of combining PP2A reactivation with kinase inhibition to counteract the very changes in tumor suppressors and oncogenes that lead to cancer development. Conversely, inhibition of PP2A to complement chemotherapy and radiation-induced cancer cell death is also an area of active investigation. Here we review the studies that utilize PP2A targeted agents as combination therapy in cancer. A potential role for PP2A in tumor immunity is also highlighted.