Oridonin induces NPM mutant protein translocation and apoptosis in NPM1c+ acute myeloid leukemia cells in vitro

The nuclear export protein exportin-1 in solid malignant tumours: From biology to clinical trials

BACKGROUND

Exportin-1 (XPO1), a crucial protein regulating nuclear-cytoplasmic transport, is frequently overexpressed in various cancers, driving tumor progression and drug resistance. This makes XPO1 an attractive therapeutic target. Over the past few decades, the number of available nuclear export-selective inhibitors has been increasing. Only KPT-330 (selinexor) has been successfully used for treating haematological malignancies, and KPT-8602 (eltanexor) has been used for treating haematologic tumours in clinical trials. However, the use of nuclear export-selective inhibitors for the inhibition of XPO1 expression has yet to be thoroughly investigated in clinical studies and therapeutic outcomes for solid tumours.

METHODS

We collected numerous literatures to explain the efficacy of XPO1 Inhibitors in preclinical and clinical studies of a wide range of solid tumours.

RESULTS

In this review, we focus on the nuclear export function of XPO1 and results from clinical trials of its inhibitors in solid malignant tumours. We summarized the mechanism of action and therapeutic potential of XPO1 inhibitors, as well as adverse effects and response biomarkers.

CONCLUSION

XPO1 inhibition has emerged as a promising therapeutic strategy in the fight against cancer, offering a novel approach to targeting tumorigenic processes and overcoming drug resistance. SINE compounds have demonstrated efficacy in a wide range of solid tumours, and ongoing research is focused on optimizing their use, identifying response biomarkers, and developing effective combination therapies.

KEY POINTS

Exportin-1 (XPO1) plays a critical role in mediating nucleocytoplasmic transport and cell cycle. XPO1 dysfunction promotes tumourigenesis and drug resistance within solid tumours. The therapeutic potential and ongoing researches on XPO1 inhibitors in the treatment of solid tumours. Additional researches are essential to address safety concerns and identify biomarkers for predicting patient response to XPO1 inhibitors.

Oridonin from Rabdosia rubescens: An emerging potential in cancer therapy - A comprehensive review

Cancer incidences are rising each year. In 2020, approximately 20 million new cancer cases and 10 million cancer-related deaths were recorded. The World Health Organization (WHO) predicts that by 2024 the incidence of cancer will increase to 30.2 million individuals annually. Considering the invasive characteristics of its diagnostic procedures and therapeutic methods side effects, scientists are searching for different solutions, including using plant-derived bioactive compounds, that could reduce the probability of cancer occurrence and make its treatment more comfortable. In this regard, oridonin (ORI), an ent-kaurane diterpenoid, naturally found in the leaves of Rabdosia rubescens species, has been found to have antitumor, antiangiogenesis, antiasthmatic, antiinflammatory, and apoptosis induction properties. Extensive research has been performed on ORI to find various mechanisms involved in its anticancer activities. This review article provides an overview of ORI's effectiveness on murine and human cancer populations from 1976 to 2022 and provides insight into the future application of ORI in different cancer therapies.

Oridonin inhibits DNMT3A R882 mutation-driven clonal hematopoiesis and leukemia by inducing apoptosis and necroptosis

DNA (cytosine-5)-methyltransferase 3A (DNMT3A) mutations occur in ~20% of de novo acute myeloid leukemia (AML) patients, and >50% of these mutations in AML samples are heterozygous missense alterations within the methyltransferase domain at residue R882. DNMT3A R882 mutations in AML patients promote resistance to anthracycline chemotherapy and drive relapse. In this study, we performed high-throughput screening and identified that oridonin, an ent-kaurene diterpenoid extracted from the Chinese herb Rabdosia rubescens, inhibits DNMT3A R882 mutant leukemic cells at a low-micromolar concentration (IC50 = 2.1 µM) by activating both RIPK1-Caspase-8-Caspase-3-mediated apoptosis and RIPK1-RIPK3-MLKL-mediated necroptosis. The inhibitory effect of oridonin against DNMT3A R882 mutant leukemia cells can also be observed in vivo. Furthermore, oridonin inhibits clonal hematopoiesis of hematopoietic stem cells (HSCs) with Dnmt3a R878H mutation comparing to normal HSCs by inducing apoptosis and necroptosis. Overall, oridonin is a potential and promising drug candidate or lead compound targeting DNMT3A R882 mutation-driven clonal hematopoiesis and leukemia.

Novel Mechanistic Observations and NES-Binding Groove Features Revealed by the CRM1 Inhibitors Plumbagin and Oridonin

The protein chromosome region maintenance 1 (CRM1) is an important nuclear export factor and drug target in diseases such as cancer and viral infections. Several plant-derived CRM1 inhibitors including plumbagin and oridonin possess potent antitumor activities. However, their modes of CRM1 inhibition remain unclear. Here, a multimutant CRM1 was engineered to enable crystallization of these two small molecules in its NES groove. Plumbagin and oridonin share the same three conjugation sites in CRM1. In solution, these two inhibitors targeted more CRM1 sites and inhibited its activity through promoting its aggregation, in addition to directly targeting the NES groove. While the plumbagin-bound NES groove resembles the NES-bound groove state, the oridonin complex reveals for the first time a more open NES groove. The observed greater NES groove dynamics may improve cargo loading through a "capture-and-tighten" mechanism. This work thus provides new insights on the mechanism of CRM1 inhibition by two natural products and a structural basis for further development of these or other CRM1 inhibitors.

Oridonin ameliorates inflammation-induced bone loss in mice via suppressing DC-STAMP expression

Currently, dendritic cell-specific transmembrane protein (DC-STAMP), a multipass transmembrane protein, is considered as the master regulator of cell-cell fusion, which underlies the formation of functional multinucleated osteoclasts. Thus, DC-STAMP has become a promising target for osteoclast-associated osteolytic diseases. In this study, we investigated the effects of oridonin (ORI), a natural tetracyclic diterpenoid compound isolated from the traditional Chinese herb Rabdosia  rubescens, on osteoclastogenesis in vivo and ex vivo. ICR mice were injected with LPS (5 mg/kg, ip, on day 0 and day 4) to induce inflammatory bone destruction. Administration of ORI (2, 10 mg·kg^-1·d^-1, ig, for 8 days) dose dependently ameliorated inflammatory bone destruction and dramatically decreased DC-STAMP protein expression in BMMs isolated from LPS-treated mice. Treatment of preosteoclast RAW264.7 cells with ORI (0.78-3.125 μM) dose dependently inhibited both mRNA and protein levels of DC-STAMP, and suppressed the following activation of NFATc1 during osteoclastogenesis. Knockdown of DC-STAMP in RAW264.7 cells abolished the inhibitory effects of ORI on RANKL-induced NFATc1 activity and osteoclast formation. In conclusion, we show for the first time that ORI effectively attenuates inflammation-induced bone loss by suppressing DC-STAMP expression, suggesting that ORI is a potential agent against inflammatory bone diseases.

Recent Progress of Oridonin and Its Derivatives for the Treatment of Acute Myelogenous Leukemia

First stage human clinical trial (CTR20150246) for HAO472, the L-alanine-(14-oridonin) ester trifluoroacetate, was conducted by a Chinese company, Hengrui Medicine Co. Ltd, to develop a new treatment for acute myelogenous leukemia. Two patents, WO2015180549A1 and CN201410047904.X, covered the development of the I-type crystal, stability experiment, conversion rate research, bioavailability experiment, safety assessment, and solubility study. HAO472 hewed out new avenues to explore the therapeutic properties of oridonin derivatives and develop promising treatment of cancer originated from naturally derived drug candidates. Herein, we sought to overview recent progress of the synthetic, physiological, and pharmacological investigations of oridonin and its derivatives, aiming to disclose the therapeutic potentials and broaden the platform for the discovery of new anticancer drugs.

Pseudolaric acid B induces apoptosis in human rhabdomyosarcoma RD cells

Pseudolaric acid B (PAB) is a diterpene-type acid isolated from the root and trunk bark of Pseudolarix kaempferi Gordon of the Pinaceae family that has been demonstrated to induce apoptosis in various cell lines and autophagy in certain cell lines including murine fibrosarcoma L929, human thyroid squamous cell carcinoma SW579 and human lung fibroblast MRC5 cells. However, in human rhabdomyosarcoma RD cells, which are derived from the most common soft tissue sarcoma in children and represent a high-grade neoplasm of a skeletal myoblast type, it is not clear whether PAB induces apoptosis or autophagy. The identification of the exact mechanism of PAB is important for studying its antitumor effects and its potential application in the treatment of human rhabdomyosarcoma. To confirm the inhibitory ability of PAB on RD cells, the inhibitory ratio of PAB was analyzed, and the results of MTT assay demonstrated that PAB inhibited RD cell proliferation. Meanwhile aggregation of the microtubule fibers was found in PAB-treated RD cells compared with that in control-treated cells, which was consistent with previous studies. In addition, PAB inhibited RD cell migration, induced apoptosis and cell cycle arrest at the G2/M phase. These results suggested that the mechanism of PAB-mediated growth inhibition in RD was similar to that reported in the human breast cancer cell line MCF-7 and the neuroglioma cell line A172; however, it was different from that reported in the L929, MRC5 and SW579 cell lines. Additional experiments demonstrated that PAB regulated the activation of caspase-8 and caspase-9 to induce apoptosis and caused an upregulation of phosphorylated H2A histone family member X and cyclin B1 expression in order to induce cell cycle arrest. Therefore, PAB may be considered a potential treatment agent for human rhabdomyosarcoma.

Nucleophosmin in Its Interaction with Ligands

Nucleophosmin (NPM1) is a mainly nucleolar protein that shuttles between nucleoli, nucleoplasm and cytoplasm to fulfill its many functions. It is a chaperone of both nucleic acids and proteins and plays a role in cell cycle control, centrosome duplication, ribosome maturation and export, as well as the cellular response to a variety of stress stimuli. NPM1 is a hub protein in nucleoli where it contributes to nucleolar organization through heterotypic and homotypic interactions. Furthermore, several alterations, including overexpression, chromosomal translocations and mutations are present in solid and hematological cancers. Recently, novel germline mutations that cause dyskeratosis congenita have also been described. This review focuses on NPM1 interactions and inhibition. Indeed, the list of NPM1 binding partners is ever-growing and, in recent years, many studies contributed to clarifying the structural basis for NPM1 recognition of both nucleic acids and several proteins. Intriguingly, a number of natural and synthetic ligands that interfere with NPM1 interactions have also been reported. The possible role of NPM1 inhibitors in the treatment of multiple cancers and other pathologies is emerging as a new therapeutic strategy.

Engineering chromosome region maintenance 1 fragments that bind to nuclear export signals

Chromosome region maintenance 1 (CRM1) exports nuclear export signal (NES) containing cargos from nucleus to cytoplasm and plays critical roles in cancer and viral infections. Biochemical and biophysical studies on this protein were often obstructed by its low purification yield and stability. With the help of PROSS server and NES protection strategy, we successfully designed three small fragments of CRM1, each made of four HEAT repeats and capable of binding to NESs in the absence of RanGTP. One of the fragments, C7, showed dramatically improved purification yield, thermostability, mechanostability, and resistance to protease digestion. We showed by isothermal titration that the protein kinase inhibitor NES binds to C7 at 1.18 μM affinity. Direct binding to C7 by several reported CRM1 inhibitors derived from plants were verified using pull-down assays. These fragments might be useful for the development of CRM1 inhibitors towards treatment of related diseases. The strategy applied here might help to tackle similar problems encountered in different fields.

Small Molecule Inhibitors of CRM1

The transport through the nuclear pore complex is used by cancer cells to evade tumor-suppressive mechanisms. Several tumor-suppressors have been shown to be excluded from the cell nucleus in cancer cells by the nuclear export receptor CRM1 and abnormal expression of CRM1 is oncogenic. Inhibition of CRM1 has long been postulated as potential approach for the treatment of cancer and to overcome therapy resistance. Furthermore, the nuclear export of viral components mediated by the CRM1 is crucial in various stages of the viral lifecycle and assembly of many viruses from diverse families, including coronavirus. However, the first nuclear export inhibitors failed or never entered into clinical trials. More recently CRM1 reemerged as a cancer target and a successful proof of concept was achieved with the clinical approval of Selinexor. The chemical complexity of natural products is a promising perspective for the discovery of new nuclear export inhibitors with a favorable toxicity profile. Several screening campaigns have been performed and several natural product-based nuclear export inhibitors have been identified. With this review we give an overview over the role of CRM1-mediated nuclear export in cancer and the effort made to identify and develop nuclear export inhibitors in particular from natural sources.

Potential Applications of NRF2 Modulators in Cancer Therapy

The nuclear factor erythroid 2-related factor 2 (NRF2)-Kelch-like ECH-associated protein 1 (KEAP1) regulatory pathway plays an essential role in protecting cells and tissues from oxidative, electrophilic, and xenobiotic stress. By controlling the transactivation of over 500 cytoprotective genes, the NRF2 transcription factor has been implicated in the physiopathology of several human diseases, including cancer. In this respect, accumulating evidence indicates that NRF2 can act as a double-edged sword, being able to mediate tumor suppressive or pro-oncogenic functions, depending on the specific biological context of its activation. Thus, a better understanding of the mechanisms that control NRF2 functions and the most appropriate context of its activation is a prerequisite for the development of effective therapeutic strategies based on NRF2 modulation. In line of principle, the controlled activation of NRF2 might reduce the risk of cancer initiation and development in normal cells by scavenging reactive-oxygen species (ROS) and by preventing genomic instability through decreased DNA damage. In contrast however, already transformed cells with constitutive or prolonged activation of NRF2 signaling might represent a major clinical hurdle and exhibit an aggressive phenotype characterized by therapy resistance and unfavorable prognosis, requiring the use of NRF2 inhibitors. In this review, we will focus on the dual roles of the NRF2-KEAP1 pathway in cancer promotion and inhibition, describing the mechanisms of its activation and potential therapeutic strategies based on the use of context-specific modulation of NRF2.

Mechanistic Pathways and Molecular Targets of Plant-Derived Anticancer ent-Kaurane Diterpenes

Since the first discovery in 1961, more than 1300 ent-kaurane diterpenoids have been isolated and identified from different plant sources, mainly the genus Isodon. Chemically, they consist of a perhydrophenanthrene subunit and a cyclopentane ring. A large number of reports describe the anticancer potential and mechanism of action of ent-kaurane compounds in a series of cancer cell lines. Oridonin is one of the prime anticancer ent-kaurane diterpenoids that is currently in a phase-I clinical trial in China. In this review, we have extensively summarized the anticancer activities of ent-kaurane diterpenoids according to their plant sources, mechanistic pathways, and biological targets. Literature analysis found that anticancer effect of ent-kauranes are mainly mediated through regulation of apoptosis, cell cycle arrest, autophagy, and metastasis. Induction of apoptosis is associated with modulation of BCL-2, BAX, PARP, cytochrome c, and cleaved caspase-3, -8, and -9, while cell cycle arrest is controlled by cyclin D1, c-Myc, p21, p53, and CDK-2 and -4. The most common metastatic target proteins of ent-kauranes are MMP-2, MMP-9, VEGF, and VEGFR whereas LC-II and mTOR are key regulators to induce autophagy.

Oridonin induces Mdm2-p60 to promote p53-mediated apoptosis and cell cycle arrest in neuroblastoma

Oridonin could induce NB (neuroblastoma) cells growth inhibition by inducing apoptosis and cell cycle arrest, and the molecular mechanisms behind the effects deserve to be further explored. Here, oridonin was confirmed to cause the reactivation of p53 (cellular tumor antigen p53) to promote the expression of a series of apoptosis‐ and cell cycle arrest‐related proteins for the biological effects. During the process, oridonin relied on the caspase activation to cleave p53‐induced Mdm2 (E3 ubiquitin‐protein ligase Mdm2) to generate Mdm2‐p60. The generation of Mdm2‐p60 stabilized p53, and resulted in p53 accumulation for p53 continuous activation. In our research, it was also found that the reactivation of p53 induced by oridonin was closely related with the generation of ROS (reactive oxygen species). Taken together, these findings explain that oridonin exerts its anticancer activity partially by targeting the Mdm2‐p53 axis in NB cells, which lay an experimental base for future research of exploring the effects and molecular mechanisms of oridonin.

Oridonin exerts anticancer effect on osteosarcoma by activating PPAR-γ and inhibiting Nrf2 pathway

Osteosarcoma is the most common high-grade human primary malignant bone sarcoma with lower survival in the past decades. Oridonin, a bioactive diterpenoid isolated from Rabdosia rubescens, has been proved to possess potent anti-cancer effects. However, its potential mechanism still remains not fully clear nowadays. In this study, we investigated the anticancer effect of oridonin on human osteosarcoma and illuminated the underlying mechanisms. In vitro, oridonin inhibited the cell viability of various osteosarcoma cells. We demonstrated that oridonin induced mitochondrial-mediated apoptosis by increasing Bax/Bcl-2 ratio, loss of mitochondrial membrane potential (MMP), triggering reactive oxygen species (ROS) generation and activating caspase-3 and caspase-9 cleavage in MG-63 and HOS cells. Moreover, we found that oridonin triggered ROS by inhibiting NF-E2-related factor 2 (Nrf2) pathway and induced mitochondrial apoptosis via inhibiting nuclear factor-κB (NF-κB) activation by activating Peroxisome Proliferator-Activated Receptor γ (PPAR-γ) in MG-63 and HOS cells. We further confirmed the results by PPAR-γ inhibitor GW9662, PPAR-γ siRNA as well as overexpression of PPAR-γ and Nrf2 in vitro. Furthermore, our in vivo study showed that oridonin inhibited tumor growth with high safety via inducing apoptosis through activating PPAR-γ and inhibiting Nrf2 activation in xenograft model inoculated HOS tumor. Taken together, oridonin exerted a dramatic pro-apoptotic effect by activating PPAR-γ and inhibiting Nrf2 pathway in vitro and in vivo. Therefore, oridonin may be a promising and effective agent for human osteosarcoma in the future clinical applications.

Pseudolaric acid B induced autophagy, but not apoptosis, in MRC5 human fibroblast cells

Autophagy and apoptosis are closely associated. In previous studies, pseudolaric acid B (PAB), a diterpene acid isolated from the root and trunk bark of Pseudolarix kaempferi Gordon (Pinaceae), was demonstrated to induce apoptosis in various cell lines. However, in L929 murine fibrosarcoma and SW579 human thyroid squamous cell carcinoma cells, only autophagy was induced. In the present study, another cell line, MRC5 human lung fibroblast cells, was identified in which PAB only induced autophagy. The relationship between apoptosis and autophagy subsequent to PAB treatment in MRC5 cells was explored. When autophagy was inhibited by 3-methyladenine (3MA), apoptosis was induced in the PAB-treated MRC5 cells. To study the mechanism for the promotion of apoptosis by 3MA in the PAB-treated cells, the expression of members from the apoptotic signal pathways was assessed. As Bcl-2, Bcl-2 associated X and pro-caspase-9 expression following PAB treatment was not affected by 3MA treatment, it was determined that apoptosis was induced independent of the mitochondrial pathway of apoptosis. As Fas and pro-caspase-8 expression following PAB treatment were not altered by 3MA, it was further determined that the death receptor pathway was not induced. However, the phosphorylation of c-Jun-N-terminal kinase and the expression of pro-caspase-3 were upregulated, and the phosphorylation of extracellular signal-regulated kinase downregulated, by the combination of PAB and 3MA treatment compared with PAB alone. It was also observed that 3MA did not affect the microtubule aggregation ability of PAB. Therefore, inhibiting autophagy in MRC5 cells did not affect the role of PAB in microtubule aggregation, while apoptosis was induced. This may present a strategy to enhance the anti-tumor effects of PAB.

Conformational stabilization as a strategy to prevent nucleophosmin mislocalization in leukemia

Nucleophosmin (NPM) is a nucleolar protein involved in ribosome assembly and cell homeostasis. Mutations in the C-terminal domain of NPM that impair native folding and localization are associated with acute myeloid leukemia (AML). We have performed a high-throughput screening searching for compounds that stabilize the C-terminal domain. We identified three hit compounds which show the ability to increase the thermal stability of both the C-terminal domain as well as full-length NPM. The best hit also seemed to favor folding of an AML-like mutant. Computational pocket identification and molecular docking support a stabilization mechanism based on binding of the phenyl/benzene group of the compounds to a particular hydrophobic pocket and additional polar interactions with solvent-accessible residues. Since these results indicate a chaperoning potential of our candidate hits, we tested their effect on the subcellular localization of AML-like mutants. Two compounds partially alleviated the aggregation and restored nucleolar localization of misfolded mutants. The identified hits appear promising as pharmacological chaperones aimed at therapies for AML based on conformational stabilization of NPM.

Production of oridonin-rich extracts from Rabdosia rubescens using hyphenated ultrasound-assisted supercritical carbon dioxide extraction

BACKGROUND

Among active components in Rabdosia rubescens, oridonin has been considered a key component and the most valuable compound because it has a wide range of activities beneficial to human health. To produce a high-quality oridonin extract, an alternative hyphenated procedure involving an ultrasound-assisted and supercritical carbon dioxide (HSC-CO₂ ) extraction method to extract oridonin from R. rubescens was developed in this study. Fictitious solubilities of oridonin in supercritical CO₂ (SC-CO₂ ) with ultrasound assistance were measured by using the dynamic method at temperatures ranging from 305.15 K to 342.15 K over a pressure range of 11.5 to 33.5 MPa.

RESULTS

Fictitious solubilities of oridonin at different temperatures and pressures were over the range of 2.13 × 10^-6 to 10.09 × 10^-6 (mole fraction) and correlated well with the density-based models, including the Bartle model, the Chrastil model, the Kumar and Johnston model and the Mendez-Santiago and Teja model, with overall average absolute relative deviations (AARDs) of 6.29%, 4.39%, 3.12% and 5.07%, respectively.

CONCLUSION

Oridonin exhibits retrograde solubility behaviour in the supercritical state. Fictitious solubility data were further determined and obtained a good fit with four semi-empirical models. Simultaneously, the values of the total heat of solution, vaporisation and solvation of oridonin were estimated. © 2016 Society of Chemical Industry.

Pseudolaric acid B inhibits neuroglioma cell proliferation through DNA damage response

Human neuroglioma is one of the most common malignant intracranial tumors in neurosurgery, and accounts for more than 50% of all brain cancer cases. Thus, a clinically effective drug with which to treat neuroglioma is urgently required. Pseudolaric acid B (PAB), a diterpene acid isolated from the root and trunk bark of Pseudolarix kaempferi Gordon (Pinaceae), was found to inhibit cell growth in a variety of cancer cell lines, but to date the effect of PAB on neuroglioma remains unclear. MTT analysis confirmed that PAB inhibited neuroglioma A172 cell growth in a time- and dose-dependent manner. In addition, PAB influenced the aggregation of tubulin in A172 cells. Meanwhile following PAB treatment, a higher percentage of cells accumulated in the G2/M phase from 12 to 48 h, while at 36 h, cell cycle slippage into the G0/G1 phase, and at 48 h, slippage into the S phase was observed using flow cytometric analysis. Corresponding protein expression was consistent with the cell cycle alteration as detected by western blotting, and it was speculated that cell cycle slippage was related to reduced effectiveness of PAB which warrants further investigation. Meanwhile PAB induced cell death by regulating p38, ERK and JNK expression and activating the DNA damage response. Therefore, PAB plays an antitumor role in A172 cells, and may be a candidate drug for neuroglioma therapy.

Mechanisms of inhibiting human leukemia cell lines by serum of rats treated with compound banmao capsule

Compound banmao capsule (CBC) is a traditional Chinese medicinal formula composed of extracts from 11 organisms. The present study investigated the mechanism of CBC on the biological behavior of human leukemia cell lines using seropharmacological methods. CBC-containing rat serum was prepared by intragastrical administration of CBC to rats. The proliferation of human leukemia HL60 and K562 cell lines was assayed by measuring cell viability with the 3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium method, while cell cycle distribution and the rate of apoptosis were evaluated with flow cytometry. The mRNA expression of vascular endothelial growth factor A (VEGF-A) and chemotactic and inflammatory genes in human leukemia cell lines was examined using reverse transcription quantitative-polymerase chain reaction methods. It was revealed that the proliferation of K562 and HL60 cells was significantly inhibited by the CBC-containing rat serum at 72 h. The CBC-containing serum also promoted the apoptosis of K562 and HL60 cell lines. The CBC-containing serum altered the cell cycle progression of K562 and HL60, increasing the proportion of the cells in G1 phase and decreasing the proportion of the cells in S phase. Attenuated expression of VEGF-A and a decreasing trend in the expression of chemotactic and inflammatory genes were identified following treatment with CBC-containing serum in HL60 and K562 cells. In conclusion, CBC-containing serum exerted an inhibitory effect on the growth of K562 and HL60 cells by decreasing cellular proliferation, promoting apoptosis and cell cycle arrest, and decreasing the expression of VEGF-A, and chemotactic and inflammatory genes.

A flavonoid compound from Chrysosplenium nudicaule inhibits growth and induces apoptosis of the human stomach cancer cell line SGC-7901

CONTEXT

Gastric cancer remains highly prevalent, but treatment options are limited. Natural products have proved to be a rich source of anticancer drugs. Chrysosplenium nudicaule Ledeb. (Saxifragaceae) is a perennial herb that grows in the highlands of China. It has been used as a traditional Chinese medicine to treat digestive diseases for hundreds of years. Recent studies revealed that this herb had anticancer activity, and the flavonoids were speculated to be the effective components. 6,7,3'-Trimethoxy-3,5,4'-trihydroxy flavone (TTF) and 5,4'-dihydroxy-3,6,3'trimethoxy-flavone-7-O-β-d-glucoside (DTFG) are flavonoid compounds isolated from Chrysosplenium nudicaule.

OBJECTIVE

This study examined the effect of TTF and DTFG on SGC-7901 human stomach cancer cell in vitro to determine the anticancer and induction of apoptosis properties of TTF.

MATERIALS AND METHODS

The proliferation of cells treated with 32, 16, 8, 4, and 2 μg/mL of TTF or DTFG for 24, 48, and 72 h was assessed by the MTT assay. After being treated with TTF, the apoptosis of SGC-7901 cells was assessed by acridine orange staining, ultrastructure, electrophoresis of DNA fragmentation, and flow cytometry.

RESULTS

Results indicated that TTF inhibited the growth of cancer cells with an IC50 value of 8.33 μg/mL after 72 h incubation. However, DTFG showed no inhibitory effect on the growth of the cancer cell. Further studies on TTF also confirmed that it was able to induce apoptosis of SGC-7901 cells at a concentration as low as 4 μg/mL.

DISCUSSION AND CONCLUSION

The apoptotic effect of TTF makes it a promising candidate for future chemotherapeutic application in treating stomach cancer.

Inhibiting cancer cell hallmark features through nuclear export inhibition

Treating cancer through inhibition of nuclear export is one of the best examples of basic research translation into clinical application. Nuclear export factor chromosomal region maintenance 1 (CRM1; Xpo1 and exportin-1) controls cellular localization and function of numerous proteins that are critical for the development of many cancer hallmarks. The diverse actions of CRM1 are likely to explain the broad ranging anti-cancer potency of CRM1 inhibitors observed in pre-clinical studies and/or clinical trials (phase I–III) on both advanced-stage solid and hematological tumors. In this review, we compare and contrast the mechanisms of action of different CRM1 inhibitors, and discuss the potential benefit of unexplored non-covalent CRM1 inhibitors. This emerging field has uncovered that nuclear export inhibition is well poised as an attractive target towards low-toxicity broad-spectrum potent anti-cancer therapy.

Steroid receptor coactivator-3 is a pivotal target of gambogic acid in B-cell Non-Hodgkin lymphoma and an inducer of histone H3 deacetylation

Gambogic acid (GA), the active ingredient from gamboges, has been verified as a potent anti-tumor agent in many cancer cells. Nevertheless, its function in lymphoma, especially in B-cell Non-Hodgkin lymphoma (NHL), remains unclear. Amplification and/or overexpression of steroid receptor coactivator-3 (SRC-3) have been detected in multiple tumors and have confirmed its critical roles in carcinogenesis, progression, metastasis and therapy resistance in these cancers. However, no clinical data have revealed the overexpression of SRC-3 and its role in B-cell NHL. In this study, we demonstrated the anti-tumor effects of GA, which included cell growth inhibition, G1/S phase cell cycle arrest and apoptosis in B-cell NHL. We also verified that SRC-3 was overexpressed in B-cell NHL in both cell lines and lymph node samples from patients. The overexpressed SRC-3 was a central drug target of GA, and its down-regulation subsequently modulated down-stream gene expression, ultimately contributing to apoptosis. Silencing SRC-3 decreased the expression of Bcl-2, Bcl-6 and cyclin D3, but not of NF-κB and IκB-α. GA treatment did not inhibit the activation of AKT signaling pathway, but induced the deacetylation of histone H3 at lysine 9 and lysine 27. Down-regulated SRC-3 was observed to interact with more HDAC1 to mediate the deacetylation of H3. As the component of E3 ligase, Cullin3 was up-regulated and mediated the degradation of SRC-3. Our results demonstrate that GA is a potent anti-tumor agent that can be used for therapy against B-cell NHL, especially against those with an abundance of SRC-3.

Pseudolaric acid B inhibits proliferation in SW579 human thyroid squamous cell carcinoma

Primary squamous cell carcinoma of the thyroid is a rare and aggressive type of neoplasm, which is routinely treated with surgery; however, despite this, survival time is not commonly more than six months. Thus, the aim of the present study was to determine the efficacy of pseudolaric acid (PAB) as a therapeutic agent. PAB is an antitubulin agent, and in the present study, inhibition of the SW579 thyroid squamous cell carcinoma cell line by PAB was investigated. PAB was found to inhibit SW579 cell growth in a time- and dose-dependent manner via interference in α-tubulin polymerization. However, the inhibitory role of PAB in SW579 cells was not predominantly due to apoptosis, but was due to the cytostatic status resulting from cell cycle arrest. The present study proposes that this is the underlying mechanism of the antitumor properties of PAB. During cytostatis, autophagy was activated to sustain cell survival and SW579 cell migration was inhibited. Nuclear p53 expression was observed to be reduced, however the role of reduced p53 requires further investigation. Therefore, PAB induced cytostasis, which inhibited SW579 cell growth and therefore may function as an antitubulin therapeutic agent.