Arctigenin inhibits triple-negative breast cancers by targeting CIP2A to reactivate protein phosphatase 2A

Management of triple-negative breast cancer by natural compounds through different mechanistic pathways

Triple-negative breast cancer (TNBC) is the most severe form of breast cancer, characterized by the loss of estrogen, progesterone, and human epidermal growth factor receptors. It is caused by various genetic and epigenetic factors, resulting in poor prognosis. Epigenetic changes, such as DNA methylation and histone modification, are the leading mechanisms responsible for TNBC progression and metastasis. This review comprehensively covers the various subtypes of TNBC and their epigenetic causes. In addition, the genetic association of TNBC with all significant genes and signaling pathways linked to the progression of this form of cancer has been enlisted. Furthermore, the possible uses of natural compounds through different mechanistic pathways have also been discussed in detail for the successful management of TNBC.

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.

Exploring the composition of protein-ligand binding sites for cancerous inhibitor of PP2A (CIP2A) by inhibitor guided binding analysis: paving a new way for the Discovery of drug candidates against triple negative breast cancer (TNBC)

Triple-negative breast cancer (TNBC) is associated with high-grade invasive carcinoma leading to a 10% to 15% death rate in younger premenopausal women. Targeting cancerous inhibitors of protein phosphatase (CIP2A) has been a highly effective approach for exploring therapeutic drug candidates. Lapatinib, a dual tyrosine kinase inhibitor, has shown promising inhibition properties by inducing apoptosis in TNBC carcinogenesis in vivo. Despite knowledge of the 3D structure of CIP2A, no reports provide insight into CIP2A ligand binding sites. To this effect, we conducted in silico site identification guided by lapatinib binding. Four of the five sites identified were cross-validated, and the stem domain revealed more excellent ligand binding affinity. The binding affinity of lapatinib in these sites was further computed using the Molecular Mechanics/Poisson-Boltzmann Surface Area (MM/PBSA) approach. According to MM/PBSA//200 ns MD simulations, lapatinib exhibited a higher binding affinity against CIP2A in site 2 with ΔG critical values of -37.1 kcal/mol. The steadiness and tightness of lapatinib with CIP2A inside the stem domain disclosed glutamic acid-318 as the culprit amino acid with the highest electrostatic energy. These results provide clear information on the CIP2A domain capable of ligand binding and validate lapatinib as a promising CIP2A inhibitor in TNBC carcinogenesis.

A systematic review on botany, ethnopharmacology, quality control, phytochemistry, pharmacology and toxicity of Arctium lappa L. fruit

ETHNOPHARMACOLOGICAL RELEVANCE

Arctium lappa L., is a biennial plant that grows around the Eurasia. Many parts of Arctium lappa L. (roots, leaves and fruits, etc.) are medically used in different countries. Arctium lappa L. fruit, also called Arctii Fructus, is traditionally applied to dispel wind-heat, ventilate lung to promote eruption, remove toxicity substance and relieve sore throat.

THE AIM OF THE REVIEW

The review aims to integrate the botany, ethnopharmacology, quality control, phytochemistry, pharmacology, derivatives and toxicity information of Arctii Fructus, so as to facilitate future research and explore the potential of Arctii Fructus as an agent for treating diseases.

MATERIALS AND METHODS

Related knowledge about Arctii Fructus were acquired from Science Direct, GeenMedical, PubMed, China National Knowledge Infrastructure (CNKI), Web of Science, Pharmacopoeia of the People's Republic of China, Doctoral and Master's thesis, ancient books, etc. RESULTS: Arctii Fructus as an herb used for medicine and food was pervasively distributed and applicated around the world. It was traditionally used to treat anemopyretic cold, dyspnea and cough, sore throat, etc. To date, more than 200 compounds have been isolated and identified from Arctii Fructus. It contained lignans, phenolic acids and fatty acids, terpenoids, volatile oils and others. Lignans, especially arctigenin and arctiin, had the extensive pharmacological effects such as anti-cancer, antiviral, anti-inflammatory activities. The ester derivatives of arctigenin had the anti-cancer, anti-Alzheimer's disease and immunity enhancing effects. Although Arctii Fructus extract had no toxicity, arctigenin was toxic at a certain dose. The alleviating effects of Arctii Fructus on chronic inflammation and ageing have been demonstrated by clinical studies.

CONCLUSION

Arctii Fructus is regarded as a worthy herb with many chemical components and various pharmacological effects. Several traditional applications have been supported by modern pharmacological research. However, their action mechanisms need to be further studied. Although many chemical components were isolated from Arctii Fructus, the current research mainly focused on lignans, especially arctiin and arctigenin. Therefore, it is very important to deeply clarify the pharmacological activities and action mechanism of the compounds and make full medicinal use of the resources of Arctii Fructus.

Preclinical Evidence that Arctigenin Effectively and Selectively Targets Clear Cell Renal Cell Carcinoma Via Suppressing EGFR and RhoA

Clear cell renal cell carcinoma (ccRCC) has poor clinical outcomes and necessitates new treatment options. Epidermal growth factor receptor (EGFR) is a potential therapeutic target, due to the associations with various carcinomas' progression. Arctigenin, a natural compound of Arctium lappa, has been shown to display anticancer abilities in various carcinomas. Cellular assays and combination studies were conducted using arctigenin and anti-ccRCC drugs. In vivo efficacy of arctigenin was determined using ccRCC xenograft mouse model. Immunoblotting and biochemistry analysis were applied to investigate the signaling affected by arctigenin. Arctigenin inhibits growth, migration, and survival of ccRCC cells while sparing normal kidney cells. Arctigenin acts synergistically with 5-FU and sorafenib but not temsirolimus in inhibiting ccRCC cells. Synergism of arctigenin with 5-FU and sorafenib was further shown in ccRCC xenograft mouse model. The combination of arctigenin with clinical anti-RCC drugs completely inhibits tumor growth without tumor progression even for an extended time period. Mechanistically, arctigenin inhibits migration in a RhoA-dependent manner while inhibits growth via suppressing EGFR-mediated signaling pathways. Our findings suggest that arctigenin performs well to add to current treatment in ccRCC and confirm the value to target EGFR to improve therapy in RCC.

The therapeutic potential of arctigenin against multiple human diseases: A mechanistic review

BACKGROUND

Arctigenin (ATG), a dibenzyl butyrolactone lignan compound, is one of the major bioactive components from the medicinal plant Arctium lappa. ATG possesses remarkable therapeutic potential against a wide range of human diseases, such as cancers, immune disorders and chronical diseases. The molecular mechanisms behind the biological effects of ATG have been intensively studied.

PURPOSE

This review aims to systematically summarize the updated knowledge of the proteins and signaling pathways behind the curative property of ATG, and further analyze the potential connections between them.

METHOD

SciFinder, Pubmed, Web of Science and Cochrane Library databases were queried for publications reporting the therapeutic properties of ATG. "Arctigenin", "disease", "cancer", "inflammation", "organ damage", "infection", "toxicity" and "pharmacokinetics" were used as the searching titles.

RESULT

625 publications were identified and 95 met the inclusion criteria and exclusion criteria. 42 studies described the molecular mechanisms implicated in ATG treatments. Several proteins including phosphodiesterase subtype 4D (PDE4D), estrogen receptor (ER) β, protein phosphatase 2A (PP2A), phosphoinositide 3-kinase (PI3K) and transmembrane protein 16A (TMEM16A) are targeted by ATG in different settings. The frequently described signaling pathways are TLR4/NF-κB, PI3K/AKT/mTOR, AMP-activated protein kinase (AMPK) and nuclear factor erythroid 2-related factor 2 (Nrf-2) signalings.

CONCLUSION

Inhibition of PI3K/AKT pathway and activation of AMPK signaling play the pivotal roles in the therapeutic effects of ATG. PI3K/AKT and AMPK signaling widely link to other signaling pathways, modulating various biological processes such as anti-inflammation, anti-oxidative stress, anti-fibrosis, anti-ER stress, anti-steatosis and pro-apoptosis, which constitute the curative mechanisms of ATG against multiple human diseases.

Combinatorial Effects of the Natural Products Arctigenin, Chlorogenic Acid, and Cinnamaldehyde Commit Oxidation Assassination on Breast Cancer Cells

Major obstacles in current breast cancer treatment efficacy include the ability of breast cancer cells to develop resistance to chemotherapeutic drugs and the off-target cytotoxicity of these drugs on normal cells, leading to debilitating side effects. One major difference between cancer and normal cells is their metabolism, as cancer cells acquire glycolytic and mitochondrial metabolism alterations throughout tumorigenesis. In this study, we sought to exploit this metabolic difference by investigating alternative breast cancer treatment options based on the application of phytochemicals. Herein, we investigated three phytochemicals, namely cinnamaldehyde (CA), chlorogenic acid (CGA), and arctigenin (Arc), regarding their anti-breast-cancer properties. These phytochemicals were administered alone or in combination to MCF-7, MDA-MB-231, and HCC1419 breast cancer or normal MCF-10A and MCF-12F breast cells. Overall, our results indicated that the combination treatments showed stronger inhibitory effects on breast cancer cells versus single treatments. However, only treatments with CA (35 μM), CGA (250 μg/mL), and the combination of CA + CGA (35 μM + 250 μg/mL) showed no significant cytotoxic effects on normal mammary epithelial cells, suggesting that Arc was the driver of normal cell cytotoxicity in all other treatments. CA + CGA and, to a lesser extent, CGA alone effectively induced breast cancer cell death accompanied by decreases in mitochondrial membrane potential, increased mitochondrial superoxide, reduced mitochondrial and glycolytic ATP production, and led to significant changes in cellular and mitochondrial morphology. Altogether, the combination of CA + CGA was determined as the best anti-breast-cancer treatment strategy due to its strong anti-breast-cancer effects without strong adverse effects on normal mammary epithelial cells. This study provides evidence that targeting the mitochondria may be an effective anticancer treatment, and that using phytochemicals or combinations thereof offers new approaches in treating breast cancer that significantly reduce off-target effects on normal cells.

CIP2A as a Key Regulator for AKT Phosphorylation Has Partial Impact Determining Clinical Outcome in Breast Cancer

Together with its reported ability to modulate AKT phosphorylation (p-AKT) status in several tumor types, the oncoprotein CIP2A has been described to induce breast cancer progression and drug resistance. However, the clinical and therapeutic relevance of the CIP2A/AKT interplay in breast cancer remains to be fully clarified. Here, we found high p-AKT levels in 80 out of 220 cases (36.4%), which were associated with negative estrogen receptor expression (p = 0.049) and CIP2A overexpression (p < 0.001). Interestingly, p-AKT determined substantially shorter overall (p = 0.002) and progression-free survival (p = 0.003), and multivariate analyses showed its CIP2A-independent prognostic value. Moreover, its clinical relevance was further confirmed in the triple negative and HER2-positive subgroups after stratifying our series by molecular subtype. Functionally, we confirmed in vitro the role of CIP2A as a regulator of p-AKT levels in breast cancer cell lines, and the importance of the CIP2A/AKT axis was also validated in vivo. Finally, p-AKT also showed a higher predictive value of response to doxorubicin than CIP2A in ex vivo analyses. In conclusion, our findings suggest that CIP2A overexpression is a key contributing event to AKT phosphorylation and highlights the CIP2A/AKT axis as a promising therapeutic target in breast cancer. However, our observations highlight the existence of alternative mechanisms that regulate AKT signaling in a subgroup of breast tumors without altered CIP2A expression that determines its independent value as a marker of poor outcome in this disease.

Arctigenin, an anti-tumor agent; a cutting-edge topic and up-to-the-minute approach in cancer treatment

Today, herbal-derived compounds are being increasingly studied in cancer treatment. Over the past decade, Arctigenin has been introduced as a bioactive dibenzylbutyrolactone lignan which is found in Chinese herbal medicines. In addition to anti-microbial, anti-inflammatory, immune-modulatory functions, Arctigenin has attracted growing attention due to its anti-tumor capabilities. It has been shown that Arctigenin can induce apoptosis and necrosis and abolish drug resistance in tumor cells by inducing apoptotic signaling pathways, caspases, cell cycle arrest, and the modulating proteasome. Moreover, Arctigenin mediates other anti-tumor functions through several mechanisms. It has been demonstrated that Arctigenin can act as an anti-inflammatory compound to inhibit inflammation in the tumor microenvironment. It also downregulates factors involved in tumor metastasis and angiogenesis, such as matrix metalloproteinases, N-cadherin, TGF-β, and VEGF. Additionally, Arctigenin, through modulation of MAPK signaling pathways and stress-related proteins, is able to abolish tumor cell growth in nutrient-deprived conditions. Due to the limited solubility of Arctigenin in water, it is suggested that modification of this compound through amino acid esterification can improve its pharmacogenetic properties. Collectively, it is hoped that using Arctigenin or its derivates might introduce new chemotherapeutic approaches in future treatment.

Arctigenin inhibits human breast cancer cell proliferation, migratory and invasive abilities and epithelial to mesenchymal transition by targeting 4EBP1

Breast cancer (BC) is one of the most common types of cancer with the highest morbidity rate amongst all cancers in women worldwide. Arctigenin is isolated from the seeds of Asteraceae lappa and exhibits anti-inflammatory and anti-viral effects. The present study aimed to investigate the effect of arctigenin on BC cells and to explore the regulation of arctigenin on eukaryotic translation initiation factor 4E binding protein 1 (4EBP1) expression. To do so, MDA-MB-231 and BT549 cells were treated with arctigenin at various concentrations (0, 5, 10, 20 and 40 µM). Cells treated with 40 µM arctigenin were transfected with pcDNA3.1-4EBP1 or NC control. Cell Counting Kit-8 assay was used to determine cell proliferation, reverse transcription quantitative PCR was used to evaluate the transfection efficiency, western blotting was used to detect relative protein expression and Transwell assays were performed to evaluate the migratory and invasive abilities of BC cells. The results demonstrated that arctigenin could inhibit the proliferation, migratory and invasive abilities, and epithelial to mesenchymal transition (EMT) of MDA-MB-231 and BT549 cells. Furthermore, arctigenin downregulated the expression of 4EBP1 in MDA-MB-231 and BT549 cells, whereas 4EBP1 overexpression could reverse the inhibiting effect of arctigenin on proliferation, migratory and invasive abilities, and EMT in MDA-MB-231 and BT549 cells. The findings suggested that arctigenin may inhibit human BC cell proliferation, migratory and invasive abilities, and EMT by targeting 4EBP1.

Blockade of AMPK-Mediated cAMP-PKA-CREB/ATF1 Signaling Synergizes with Aspirin to Inhibit Hepatocellular Carcinoma

Simple Summary

Epidemiological and experimental studies have demonstrated that aspirin (acetylsalicylic acid) may prevent the incidence of some types of human cancer, including colorectal cancer and hepatocellular carcinoma (HCC). In addition, preclinical studies indicate that aspirin in combination with other treatments may achieve a more significant anti-cancer effect for established tumors. This study aims to improve the anti-cancer effect of aspirin by targeting signaling pathways related to aspirin and its targets. We find that aspirin may induce cAMP–PKA–CREB/ATF1 signaling in HCC via AMPK and its downstream target carbamoyl-phosphate synthase 1 (CPS1). Blockade of PKA–CREB/ATF1 signaling by the natural agent berbamine could sensitize HCC to aspirin. This research indicates that the combination of two inexpensive drugs, aspirin and berbamine, holds promise in preventing and treating HCC.

Abstract

Aspirin can prevent or inhibit inflammation-related cancers, such as colorectal cancer and hepatocellular carcinoma (HCC). However, the effectiveness of chemotherapy may be compromised by activating oncogenic pathways in cancer cells. Elucidation of such chemoresistance mechanisms is crucial to developing novel strategies to maximize the anti-cancer effects of aspirin. Here, we report that aspirin markedly induces CREB/ATF1 phosphorylation in HCC cells, which compromises aspirin’s anti-HCC effect. Inhibition of AMP-activated protein kinase (AMPK) abrogates the induction of CREB/ATF1 phosphorylation by aspirin. Mechanistically, activation of AMPK by aspirin results in decreased expression of the urea cycle enzyme carbamoyl-phosphate synthase 1 (CPS1) in HCC cells and xenografts. Treatment with aspirin or CPS1 knockdown stimulates soluble adenylyl cyclase expression, thereby increasing cyclic AMP (cAMP) synthesis and stimulating PKA–CREB/ATF1 signaling. Importantly, abrogation of aspirin-induced CREB/ATF1 phosphorylation could sensitize HCC to aspirin. The bis-benzylisoquinoline alkaloid berbamine suppresses the expression of cancerous inhibitor of protein phosphatase 2A (CIP2A), leading to protein phosphatase 2A-mediated downregulation of CREB/ATF1 phosphorylation. The combination of berbamine and aspirin significantly inhibits HCC in vitro and in vivo. These data demonstrate that the regulation of cAMP-PKA-CREB/ATF1 signaling represents a noncanonical function of CPS1. Targeting the PKA–CREB/ATF1 axis may be a strategy to improve the therapeutic effects of aspirin on HCC.

A Review of Natural Therapies Potentially Relevant in Triple Negative Breast Cancer Aimed at Targeting Cancer Cell Vulnerabilities

We reviewed the research into the mechanisms of growth of triple negative breast cancer (TNBC) based on laboratory pre-clinical studies that have shaped understanding of the disease over the past decade. In response to these findings, we propose an approach to potentially prevent cancer metabolic adaptation and recurrence. This paper collates pre-clinical results, first to determine the tumor’s mechanisms of growth and then to source natural substances that could potentially suppress those mechanisms. The results from in vivo and in vitro studies of TNBC were combined first to select 10 primary mechanisms (Hypoxia-inducible factor 1α, Hedgehog, MAPK, MTAP, NF-κ B, Notch, P13K, STAT3, and Wnt signaling pathways plus p53 and POL2A gene expression) that promote TNBC growth, and second to propose a treatment array of 21 natural compounds that suppress laboratory models of TNBC via these mechanisms. We included BRCA mutations in the review process, but only pathways with the most preclinical studies utilizing natural products were included. Then we outlined potential biomarkers to assess the changes in the micro-environment and monitor biochemical pathway suppression. This suppression-centric aim targets these mechanisms of growth with the goal of potentially halting tumor growth and preventing cancer cell metabolic adaptation. We chose TNBC to demonstrate this 5-step strategy of supplementary therapy, which may be replicated for other tumor types.

Arctigenin Enhances the Cytotoxic Effect of Doxorubicin in MDA-MB-231 Breast Cancer Cells

Several reports have described the anti-cancer activity of arctigenin, a lignan extracted from Arctium lappa L. Here, we investigated the effect of arctigenin (ATG) on doxorubicin (DOX)-induced cell death using MDA-MB-231 human breast cancer cells. The results showed that DOX-induced cell death was enhanced by ATG/DOX co-treatment in a concentration-dependent manner and that this was associated with increased DOX uptake and the suppression of multidrug resistance-associated protein 1 (MRP1) gene expression in MDA-MB-231 cells. ATG enhanced DOX-induced DNA damage and decreased the phosphorylation of signal transducer and activator of transcription 3 (STAT3) and the expressions of RAD51 and survivin. Cell death caused by ATG/DOX co-treatment was mediated by the nuclear translocation of apoptosis inducing factor (AIF), reductions in cellular and mitochondrial Bcl-2 and Bcl-xL, and increases in mitochondrial BAX levels. However, caspase-3 and -7 did not participate in DOX/ATG-induced cell death. We also found that DOX/ATG-induced cell death was linked with activation of the p38 signaling pathway and suppressions of the phosphorylations and expressions of Akt and c-Jun N-terminal kinase. Taken together, these results show that ATG enhances the cytotoxic activity of DOX in MDA-MB-231 human breast cancer cells by inducing prolonged p21 expression and p38-mediated AIF-dependent cell death. In conclusion, our findings suggest that ATG might alleviate the side effects and improve the therapeutic efficacy of DOX.

Akt-targeted therapy as a promising strategy to overcome drug resistance in breast cancer - A comprehensive review from chemotherapy to immunotherapy

Breast cancer is the most frequently occurring cancer in women. Chemotherapy in combination with immunotherapy has been used to treat breast cancer. Atezolizumab targeting the protein programmed cell death-ligand (PD-L1) in combination with paclitaxel was recently approved by the Food and Drug Administration (FDA) for Triple-Negative Breast Cancer (TNBC), the most incurable type of breast cancer. However, the use of such drugs is restricted by genotype and is effective only for those TNBC patients expressing PD-L1. In addition, resistance to chemotherapy with drugs such as lapatinib, geftinib, and tamoxifen can develop. In this review, we address chemoresistance in breast cancer and discuss Akt as the master regulator of drug resistance and several oncogenic mechanisms in breast cancer. Akt not only directly interacts with the mitogen-activated protein (MAP) kinase signaling pathway to affect PD-L1 expression, but also has crosstalk with Notch and Wnt/β-catenin signaling pathways involved in cell migration and breast cancer stem cell integrity. In this review, we discuss the effects of tyrosine kinase inhibitors on Akt activation as well as the mechanism of Akt signaling in drug resistance. Akt also has a crucial role in mitochondrial metabolism and migrates into mitochondria to remodel breast cancer cell metabolism while also functioning in responses to hypoxic conditions. The Akt inhibitors ipatasertib, capivasertib, uprosertib, and MK-2206 not only suppress cancer cell proliferation and metastasis, but may also inhibit cytokine regulation and PD-L1 expression. Ipatasertib and uprosertib are undergoing clinical investigation to treat TNBC. Inhibition of Akt and its regulators can be used to control breast cancer progression and also immunosuppression, while discovery of additional compounds that target Akt and its modulators could provide solutions to resistance to chemotherapy and immunotherapy.

FL118 inhibits viability and induces apoptosis of colorectal cancer cells via inactivating the CIP2A/PP2A axis

AIMS

FL118, a novel camptothecin analogue, has been extensively studied for its superior antitumor potency. The aim of this research study is to explore its potential mechanism of action in anti- colorectal cancer (CRC).

MAIN METHODS

The effect of FL118 on CRC cell proliferation was assessed using CCK-8 assay, while apoptosis was detected using Hoechst staining and Flow cytometry assays. The expression levels of CIP2A were analyzed using qRT-PCR. The expression of CIP2A, PP2A-C, Bax, cleaved caspase-3 and PARP were analyzed using western blotting analysis. The expressions of related proteins in CRC tissues were detected using immunohistochemical staining. TUNEL assay was used to detect apoptosis of tissue. Toxicity of FL118 in primary organs were examined using H&E staining.

KEY FINDINGS

The results show that FL118 can inhibit the proliferation and clonogenic potential of CRC cells and increase the expression of pro-apoptosis proteins, Bax, cleaved caspase-3 and PARP. Microarray analyses found that FL118 treatment significantly decreases cancerous inhibition of protein phosphatase 2A (CIP2A). Further validation found that CIP2A is aberrantly upregulated in CRC tissues, and is positively correlated with the progression of CRC. In vitro findings confirm that FL118 mediates the downregulation of CIP2A, at both protein and mRNA levels. Co-treatment with Okadaic acid (OA) (a PP2A inhibitor) partially abolishes the anti-proliferative and pro-apoptotic effect of FL118. Consistently, in vivo experiment demonstrates that FL118 can effectively suppress tumorigenesis without any obvious toxic effects.

SIGNIFICANCE

Collectively, these findings exhibit the anti-neoplastic effects of FL118 against CRC through the down regulation of CIP2A, which subsequently enhances the activity of PP2A.

PP2A: A Promising Biomarker and Therapeutic Target in Endometrial Cancer

Over the last decade, the use of targeted therapies has immensely increased in the treatment of cancer. However, treatment for endometrial carcinomas (ECs) has lagged behind, although potential molecular markers have been identified. This is particularly problematic for the type II ECs, since these aggressive tumors are usually not responsive toward the current standard therapies. Therefore, type II ECs are responsible for most EC-related deaths, indicating the need for new treatment options. Interestingly, molecular analyses of type II ECs have uncovered frequent genetic alterations (up to 40%) in PPP2R1A, encoding the Aα subunit of the tumor suppressive heterotrimeric protein phosphatase type 2A (PP2A). PPP2R1A mutations were also reported in type I ECs and other common gynecologic cancers, albeit at much lower frequencies (0-7%). Nevertheless, PP2A inactivation in the latter cancer types is common via other mechanisms, in particular by increased expression of Cancerous Inhibitor of PP2A (CIP2A) and PP2A Methylesterase-1 (PME-1) proteins. In this review, we discuss the therapeutic potential of direct and indirect PP2A targeting compounds, possibly in combination with other anti-cancer drugs, in EC. Furthermore, we investigate the potential of the PP2A status as a predictive and/or prognostic marker for type I and II ECs.

Cucurbitacin B Induces the Lysosomal Degradation of EGFR and Suppresses the CIP2A/PP2A/Akt Signaling Axis in Gefitinib-Resistant Non-Small Cell Lung Cancer

Non-small cell lung cancer (NSCLC) patients carrying an epidermal growth factor receptor (EGFR) mutation are initially sensitive to EGFR-tyrosine kinase inhibitors (TKIs) treatment, but soon develop an acquired resistance. The treatment effect of EGFR-TKIs-resistant NSCLC patients still faces challenges. Cucurbitacin B (CuB), a triterpene hydrocarbon compound isolated from plants of various families and genera, elicits anticancer effects in a variety of cancer types. However, whether CuB is a viable treatment option for gefitinib-resistant (GR) NSCLC remains unclear. Here, we investigated the anticancer effects and underlying mechanisms of CuB. We report that CuB inhibited the growth and invasion of GR NSCLC cells and induced apoptosis. The inhibitory effect of CuB occurred through its promotion of the lysosomal degradation of EGFR and the downregulation of the cancerous inhibitor of protein phosphatase 2A/protein phosphatase 2A/Akt (CIP2A/PP2A/Akt) signaling axis. CuB and cisplatin synergistically inhibited tumor growth. A xenograft tumor model indicated that CuB inhibited tumor growth in vivo. Immunohistochemistry results further demonstrated that CuB decreased EGFR and CIP2A levels in vivo. These findings suggested that CuB could suppress the growth and invasion of GR NSCLC cells by inducing the lysosomal degradation of EGFR and by downregulating the CIP2A/PP2A/Akt signaling axis. Thus, CuB may be a new drug candidate for the treatment of GR NSCLC.

Modular Synthesis and Biological Investigation of 5-Hydroxymethyl Dibenzyl Butyrolactones and Related Lignans

Dibenzyl butyrolactone lignans are well known for their excellent biological properties, particularly for their notable anti-proliferative activities. Herein we report a novel, efficient, convergent synthesis of dibenzyl butyrolactone lignans utilizing the acyl-Claisen rearrangement to stereoselectively prepare a key intermediate. The reported synthetic route enables the modification of these lignans to give rise to 5-hydroxymethyl derivatives of these lignans. The biological activities of these analogues were assessed, with derivatives showing an excellent cytotoxic profile which resulted in programmed cell death of Jurkat T-leukemia cells with less than 2% of the incubated cells entering a necrotic cell death pathway.

Euxanthone suppresses tumor growth and metastasis in colorectal cancer via targeting CIP2A/PP2A pathway

AIM

Colorectal cancer (CRC) accounts for over 600,000 deaths annually worldwide. Euxanthone is a flavonoid compound extracted from Polygala caudata, with documented anti-neoplastic actions. The current study aimed to determine the therapeutic potential of euxanthone in CRC.

METHODS AND MATERIALS

Cell Counting Kit-8 (CCK-8) assay was used to analyze the effect of euxanthone on the cell viability, and apoptosis was detected by the TUNEL assay. The in vitro migratory capacity was determined by wound healing and the invasiveness was assessed by Transwell assay. Western blotting was used to determine the level of relevant proteins. Furthermore, a CRC xenograft murine model was used to analyze the therapeutic efficacy of euxanthone in vivo. Isobaric tags for relative and absolute quantification (iTRAQ) was then performed to identify the potential targets of euxanthone. To validate the role of cancerous inhibitor of PP2A (CIP2A) in the anti-cancer effects of euxanthone, plasmid overexpressing CIP2A and shRNA targeting CIP2A were used in in vitro assays.

KEY FINDINGS

Euxanthone decreased cell viability and increased apoptosis in CRC cells, in addition to restraining migration, invasion and EMT. Similarly, euxanthone also effectively suppressed tumor growth and pulmonary metastasis in vivo. iTRAQ analysis identified CIP2A as the primary target responsible for the anticancer effects of euxanthone. The mediatory role of CIP2A was validated when the anticancer activity of euxanthone was significantly blocked by CIP2A overexpression, while CIP2A knockdown sensitized the CRC cells to euxanthone.

SIGNIFICANCE

Euxanthone exerts anti-cancer effects in vitro and in vivo in CRC by targeting CIP2A/PP2A signaling.

Long non-coding RNA ASBEL promotes osteosarcoma cell proliferation, migration, and invasion by regulating microRNA-21

Osteosarcoma is the most common malignant bone tumor in children and adolescents with high rate of incidence, high frequency of recurrence, and high degree of metastasis. This study aimed to investigate the effects of long noncoding RNA antisense ncRNA in the abundant in neuroepithelium area (ANA)/B-cell translocation gene 3 (BTG3) locus (lncRNA ASBEL) on the pathogenesis of osteosarcoma. The expression levels of ASBEL in human osteoblast cells and human osteosarcoma cells were evaluated using qRT-PCR. Effects of ASBEL knockdown on cell viability, migration, and invasion were detected using trypan blue exclusion assay, cell migration, and cell invasion assay, respectively. The regulatory effects of ASBEL on microRNA-21 (miR-21) were analyzed using qRT-PCR. The roles of miR-21 and protein phosphatase 2A (PP2A), the possible downstream factor of miR-21, in osteosarcoma cell proliferation, migration, and invasion were also explored. The results showed that ASBEL was highly expressed in osteosarcoma cells. Knockdown of ASBEL inhibited osteosarcoma cell viability, migration, and invasion, as well as the expression level of miR-21. PP2A was a direct target of miR-21, which participated in the effects of ASBEL and miR-21 on the activation of phosphatidylinositol 3-kinase/protein kinase 3/glycogen synthase kinase-3β (PI3K/AKT/GSK3β) and mitogen-activated protein kinase/extracellular regulated protein kinase (MEK/ERK) signaling pathways as well as the enhancement of osteosarcoma cell proliferation, migration, and invasion. In conclusion, we verified that ASBEL-miR-21-PP2A pathway might play critical regulatory effects on the pathogenesis of osteosarcoma and could be as the potential therapeutic target and biomarker for osteosarcoma treatment.

Ethoxysanguinarine inhibits viability and induces apoptosis of colorectal cancer cells by inhibiting CIP2A

Cancerous inhibitor of protein phosphatase 2A (CIP2A) an endogenous inhibitor of protein phosphatase 2A (PP2A), which can promote proliferation and transformation of several cancer types, has been shown to be a target for tumor therapy. The present study investigated the effects and underlying mechanisms of action of a novel natural compound, ethoxysanguinarine (Eth), on colorectal cancer (CRC) cells. MTT assay and flow cytometric assay found that Eth inhibited the viability and induced the apoptosis of the CRC cells. The inhibition of viability and activation of apoptosis was mediated through the Eth-induced decrease in CIP2A expression. Knockdown of CIP2A by RNA interference sensitized, whereas overexpression of CIP2A antagonized, Eth-induced viability inhibition and apoptosis. Furthermore, western blot analysis suggested that Eth inhibited phosphorylation of CIP2A downstream molecule protein kinase B via the activation of PP2A. CRC xenograft tests also confirmed the antitumor effect of Eth in vivo. These results advance our understanding of Eth-induced viability inhibition and apoptosis, implying the requirement for further investigation of Eth as a CIP2A inhibitor for cancer therapies.

Arctigenin represses TGF-β-induced epithelial mesenchymal transition in human lung cancer cells

Arctigenin (ARC) is a lignan that is abundant in Asteraceae plants, which show anti-inflammatory and anti-cancer activities. The current study investigated whether ARC affects cancer progression and metastasis, focusing on EMT using invasive human non-small cell lung cancer (NSCLC) cells. No toxicity was observed in the cells treated with different doses of ARC (12-100 μM). The treatment of ARC repressed TGF-β-stimulated changes of metastatic morphology and cell invasion and migration. ARC inhibited TGF-β-induced phosphorylation and transcriptional activity of smad2/3, and expression of snail. ARC also decreased expression of N-cadherin and increased expression of E-cadherin in dose-dependent and time-dependent manners. These changes were accompanied by decreased amount of phospho-smad2/3 in nucleus and nuclear translocation of smad2/3. Moreover, ARC repressed TGF-β-induced phosphorylation of ERK and transcriptional activity of β-catenin. Our data demonstrate anti-metastatic activity of ARC in lung cancer model.