Oleanolic acid suppresses the proliferation of lung carcinoma cells by miR-122/Cyclin G1/MEF2D axis

Targeting microRNAs: a new action mechanism of natural compounds

Unlike genetics, epigenetics involves the modification of genome without changes in DNA sequences, including DNA methylation, histone modification, chromatin remodeling and noncoding RNA regulation. MicroRNA (miRNA), a member of noncoding RNAs superfamily, participates in RNA interference through a unique mechanism. Currently, microRNAs have been found to be regulated by some natural compounds. Through altering the expression of miRNAs and influencing the downstream signaling pathways or target genes, several natural compounds exhibit its bioactivity in the prevention, diagnosis, therapy, prognosis and drug resistance of human diseases, such as cancer. In this review, several natural compounds and their studies about miRNA-related action mechanism were summarized. These studies provide a new insight into action mechanism by which natural compound exerts its bioactivity and a novel treatment strategy, demonstrating natural compound a promising remedy for clinical treatments.

Dietary Phytochemicals and Cancer Chemoprevention: A Perspective on Oxidative Stress, Inflammation, and Epigenetics

Oxidative stress occurs when cellular reactive oxygen species levels exceed the self-antioxidant capacity of the body. Oxidative stress induces many pathological changes, including inflammation and cancer. Chronic inflammation is believed to be strongly associated with the major stages of carcinogenesis. The nuclear factor erythroid 2-related factor 2 (Nrf2) pathway plays a crucial role in regulating oxidative stress and inflammation by manipulating key antioxidant and detoxification enzyme genes via the antioxidant response element. Many dietary phytochemicals with cancer chemopreventive properties, such as polyphenols, isothiocyanates, and triterpenoids, exert antioxidant and anti-inflammatory functions by activating the Nrf2 pathway. Furthermore, epigenetic changes, including DNA methylation, histone post-translational modifications, and miRNA-mediated post-transcriptional alterations, also lead to various carcinogenesis processes by suppressing cancer repressor gene transcription. Using epigenetic research tools, including next-generation sequencing technologies, many dietary phytochemicals are shown to modify and reverse aberrant epigenetic/epigenome changes, potentially leading to cancer prevention/treatment. Thus, the beneficial effects of dietary phytochemicals on cancer development warrant further investigation to provide additional impetus for clinical translational studies.

The miR27b-CCNG1-P53-miR-508-5p axis regulates multidrug resistance of gastric cancer

Multidrug resistance (MDR) correlates with treatment failure and poor prognosis among gastric cancer (GC) patients. In a previous study using high-throughput functional screening, we identified 11 microRNAs (miRNAs) that regulate MDR in GC and found that miR-508-5p reversed MDR by targeting ABCB1 and ZNRD1. However, the mechanism by which miR-508-5p was decreased in chemo-resistant GC cells was unclear. In this study, we found that ectopic miR-27b is sufficient to sensitize tumors to chemotherapy in vitro and in vivo. Moreover, miR-27b directly targets the 3′ untranslated regions (3′-UTRs) of CCNG1, a well-known negative regulator of P53 stability. Interestingly, miR-27b up-regulation leads to increased miR-508-5p expression, and this phenomenon is mediated by CCNG1 and P53. Further investigation indicated that miR-508-5p is directly regulated by P53. Thus, the miR-27b/CCNG1/P53/miR-508-5p axis plays important roles in GC-associated MDR. In addition, miR-27b and miR-508-5p expression was detected in GC tissues with different chemo-sensitivities, and we found that tissues in which miR-27b and miR-508-5p are up-regulated are more sensitive to chemotherapy. Together, these data suggest that the combination of miR-27b and miR-508-5p represents a potential marker of MDR. Restoring the miR-27b and miR-508-5p levels might contribute to MDR reversion in future clinical practice.

MEF2D Transduces Microenvironment Stimuli to ZEB1 to Promote Epithelial-Mesenchymal Transition and Metastasis in Colorectal Cancer

Epithelial-mesenchymal transition (EMT) is an essential mechanism of metastasis, including in colorectal cancer. Although EMT processes are often triggered in cancer cells by their surrounding microenvironment, how EMT-relevant genes control these processes is not well understood. In multiple types of cancers, the transcription factor MEF2D has been implicated in cell proliferation, but its contributions to metastasis have not been addressed. Here, we show MEF2D is overexpressed in clinical colorectal cancer tissues where its high expression correlates with metastatic process. Functional investigations showed that MEF2D promoted cancer cell invasion and EMT and that it was essential for certain microenvironment signals to induce EMT and metastasis in vivo Mechanistically, MEF2D directly regulated transcription of the EMT driver gene ZEB1 and facilitated histone acetylation at the ZEB1 promoter. More importantly, MEF2D responded to various tumor microenvironment signals and acted as a central integrator transducing multiple signals to activate ZEB1 transcription. Overall, our results define a critical function for MEF2D in upregulating EMT and the metastatic capacity of colorectal cancer cells. Further, they offer new insights into how microenvironment signals activate EMT-relevant genes and deepen the pathophysiologic significance of MEF2D, with potential implications for the prevention and treatment of metastatic colorectal cancer. Cancer Res; 76(17); 5054-67. ©2016 AACR.

Solid inclusion complexes of oleanolic acid with amino-appended β-cyclodextrins (ACDs): Preparation, characterization, water solubility and anticancer activity

Oleanolic acid (OA) is a pentacyclic triterpenoid acid of natural abundance in plants which possesses important biological activities. However, its medicinal applications were severely impeded by the poor water solubility and resultant low bioavailability and potency. In this work, studies on solid inclusion complexes of OA with a series of amino-appended β-cyclodextrins (ACDs) were conducted in order to address this issue. These complexes were prepared by suspension method and were well characterized by NMR, SEM, XRD, TG, DSC and Zeta potential measurement. The 2:1 inclusion mode of ACDs/OA complexes was elucidated by elaborate 2D NMR (ROESY). Besides, water solubility of OA was dramatically promoted by inclusion complexation with ACDs. Moreover, in vitro anticancer activities of OA against human cancer cell lines HepG2, HT29 and HCT116 were significantly enhanced after formation of inclusion complexes, while the apoptotic response results indicated their induction of apoptosis of cancer cells. This could provide a novel approach to development of novel pharmaceutical formulations of OA.

MiR-19a, miR-122 and miR-223 are differentially regulated by hepatitis B virus X protein and involve in cell proliferation in hepatoma cells

Background

Hepatitis B virus (HBV) X protein (HBx) is a type of oncogenic protein involved in the progression of hepatocellular carcinoma (HCC) via interacting with host genes. Dysregulation of microRNAs (miRNAs) has been observed in HCC. This study aimed to investigate the role of HBx protein in the regulation of miR-19a, miR-122 and miR-223, and examine if these miRNAs involve in progression of malignant hepatocytes.

Methods

Quantitative real time PCR (qRT-PCR) was used to measure the expression of miR-19a, miR-122 and miR-223 in patient samples and in HepG2 cells transfected with HBx or 1.3 fold HBV genome and also in HepG2.2.15 cells, which stably produces HBV. Their target mRNAs and proteins-PTEN, cyclin G1 and c-myc were measured by qRT-PCR and western blot, respectively. The effect of miR-19a, miR-122 and miR-223, and their respective target genes, on cell proliferation was analyzed using 5-ethynyl-2-deoxyuridine incorporation and MTT assay.

Results

MiR-19a showed an up-regulation in HBV-positive HCC patients compared to healthy controls and HBV-negative HCC patients, while miR-122 and miR-223 showed a down-regulation compared to healthy controls, and miR-122 in HBV-positive HCC patients was also down-regulated when compared to HBV-negative HCC patients. MiR-19a was found to be up-regulated in HepG2 cells transfected with HBx or 1.3 fold HBV genome, but down-regulated in HepG2.2.15 cells. MiR-122 and miR-223 were down-regulated in HBx or 1.3 fold HBV transfected HepG2 cells as well as in HepG2.2.15 cell. Their target mRNAs and corresponding proteins-PTEN was down-regulated, while cyclin G1 and c-myc were found to be up-regulated. Modulated expression of miR-19a, miR-122 and miR-223 enhanced cell proliferation of HBx-transfected HepG2 cells, and rescue experiment further showed that their target genes-PTEN, cyclin G1and c-myc involved in cell proliferation of HBx-transfected HepG2 cells.

Conclusions

The expression of miR-19a, miR-122 and miR-223 were differentially regulated by HBx protein, the differential expression of miR-19a, miR-122 and miR-223 plays an important role in cell proliferation of HCC. This study provides new insight into understanding how HBx protein interacts with miRNAs and subsequently regulates host function.

MEF2D/Wnt/β-catenin pathway regulates the proliferation of gastric cancer cells and is regulated by microRNA-19

The underlying molecular pathogenesis in gastric cancer remains poorly unknown. The transcription factor myocyte enhancer factor 2D (MEF2D) participates in the initiation and development of many human cancers. However, its potential roles in gastric cancer have surprisingly not been studied. In present study, we first explored MEF2's expression in gastric cancer, finding that only MEF2D rather than MEF2A, 2B, or 2C was elevated in gastric cancer clinical specimens. Furthermore, immunohistochemical analysis on the tissue samples obtained from 260 patients with gastric cancer revealed that MEF2D expression was significantly associated with the clinical stage, vascular invasion, metastasis, and tumor size. Gastric cancer patients with MEF2D expression showed a significantly shorter overall survival time compared with that of patients lacking of MEF2D. Multivariate analysis revealed that MEF2D expression was an independent prognostic factor for overall survival. These results indicated that MEF2D was a prognostic marker for gastric cancer. Notably, MEF2D silencing was able to reduce the proliferation and survival of gastric cancer cells. Further study revealed that MEF2D suppression significantly inactivated the oncogenic Wnt/β-catenin pathway. Downregulation of MEF2D inhibited the tumorigenesis of gastric cancer cells in nude mice. Finally, MEF2D is a direct target of miR-19, which was found to be decreased in gastric cancer clinical specimens. Collectively, we found that miR-19/MEF2D/Wnt/β-catenin regulatory network contributes to the growth of gastric cancer, hinting a new promising target for gastric cancer treatment.

Natural compound-derived epigenetic regulators targeting epigenetic readers, writers and erasers

Post-translational modifications can affect gene expression in a long-term manner without changes in the primary nucleotide sequence of the DNA. These epigenetic alterations involve dynamic processes that occur in histones, chromatin-associated proteins and DNA. In response to environmental stimuli, abnormal epigenetic alterations cause disorders in the cell cycle, apoptosis and other cellular processes and thus contribute to the incidence of diverse diseases, including cancers. In this review, we will summarize recent studies focusing on certain epigenetic readers, writers, and erasers associated with cancer development and how newly discovered natural compounds and their derivatives could interact with these targets. These advances provide insights into epigenetic alterations in cancers and the potential utility of these alterations as therapeutic targets for the future development of chemopreventive and chemotherapeutic drugs.

Oleanolic acid inhibits cell survival and proliferation of prostate cancer cells in vitro and in vivo through the PI3K/Akt pathway

Oleanolic acid (OA) is a naturally occurring pentacyclic triterpenoid and possesses diverse pharmacological activities, including anti-cancer effects that have been confirmed in multiple types of human cancers. However, the potential effect of natural OA on human prostate cancer is still unclear. The present study aimed to explore whether and how OA exerted anti-cancer effects in prostate cancer. Our data showed that OA inhibited cell viability and proliferation, and promoted cell apoptosis and G0/G1 phase cell cycle arrest in prostate cancer PC-3, DU145, and LNCaP cells, in a dose-dependent manner. In addition, OA was found to regulate the expression levels of apoptosis-related and cell cycle-related proteins, as well as the activity of PI3K/Akt pathway, in a dose-dependent manner. Mechanistically, our data revealed that OA exerted anti-cancer effects in vitro in PC-3 and DU145 cells by repressing the PI3K/Akt pathway. In agreement, OA also suppressed the tumor growth of PC-3 cells in vivo via inhibition of the PI3K/Akt pathway. In conclusion, our findings demonstrate the anti-cancer properties of OA in prostate cancer cells, both in vitro and in vivo, and provide the experimental evidence for the use of OA as an adjuvant agent for prostate cancer patients.

The involvement of myocyte enhancer factor 2D in regulating tumor biology of cardiac myxoma

The pro-survival transcription factor myocyte enhancer factor 2D (MEF2D) is identified to exhibit pro-tumor effects based on clinical and experimental studies. However, the detailed mechanisms underlying IGF-1-MEF2D pathway-induced tumor biology in cardiac myxoma (CM) was not clear. Here, we investigated the role of MEF2D in CM tissues and cells using RT-PCR, western blot, gene silencing, et al. Our findings revealed MEF2D was significantly increased in CM tissues compared with adjacent normal tissues and closely related to tumor size. In vitro assay demonstrated that IGF-1 enhanced CM cell proliferation in a time-dependent fashion. However, knockdown of MEF2D reversed the IGF-1-induced proliferative effects on CM cells in a time-dependent fashion and further resulted in cell cycle arrest. Based on the molecular level, IGF-1 enhanced the expression of epidermal growth factor receptor (EGFR) and matrix metalloprotein 9 (MMP9) in CM cells, whereas knockdown of MEF2D was able to reduce the expression of EGFR and MMP9 compared with vector control. Furthermore, we found knockdown of MEF2D directly affected G1/S transition in cultured CM cells. In conclusion, MEF2D regulates IGF-1-induced proliferation and apoptosis in CM development, indicating IGF-1-MEF2D pathway may be a useful target for treatment.

miR-218 suppressed the growth of lung carcinoma by reducing MEF2D expression

Lung carcinoma is a deadly malignant disease with poor prognosis and increasing incidence in recent years. However, the molecular mechanism underlying the initiation and progression of lung cancer is still not completely elucidated. Recently, myocyte enhancer factor 2D (MEF2D) has been reported to promote the growth of liver cancer, but its implication in lung cancer is still unknown. This study is aimed to determine the role of MEF2D in lung carcinoma. Quantitative PCR (qPCR) and immunoblot assays showed that MEF2D was overexpressed in lung cancer tissues and cell lines, compared with the matched normal tissues and cell lines. Small interfering RNA (siRNA) suppression of MEF2D was able to reduce the proliferation, survival, and invasion of lung carcinoma cells. The transfection of MEF2D-expressing constructs into normal lung fibroblast cells promoted their proliferation and motility. The role of MEF2D in the growth of lung cancer was also confirmed in mice. Further study revealed that miR-218, which was underexpressed in lung carcinoma, was predicted to bind the 3'-untranslated region (UTR) of MEF2D mRNA. miR-218 was shown to suppress the activity of luciferase with MEF2D 3'-UTR. The changes in miR-218 levels affected the expression of MEF2D in lung cancer cells and normal fibroblast cells. There is also an inverse association between miR-218 abundance and MEF2D levels in the lung carcinoma specimen. Furthermore, the transfection of a plasmid that expressed MEF2D resistance to miR-218 regulation abolished the inhibitory effect of miR-218 on lung cancer cells. Collectively, MEF2D overexpression participated in the growth of lung cancers and its aberrant expression may result from the reduction of tumor suppressor miR-218.

miR-1244/Myocyte Enhancer Factor 2D Regulatory Loop Contributes to the Growth of Lung Carcinoma

Lung carcinoma greatly threatens human health, due to its increasing incidence in recent years and poor prognosis. However, this malignancy displays resistance against current therapeutic strategies. One of major causes leading to bad outcomes for lung cancer therapy is the lack of understanding on its tumorigenesis and progression. To explore the molecular mechanism by which lung cancer progresses, we employed multidisciplinary approaches and used lung cancer cell lines as research models. miR-1244 was underexpressed in lung carcinoma by 40.6-73.8%, which is highly associated with patients' survival. miR-1244 restoration was shown to affect the proliferation, survival, and invasion of lung cancer cells. miR-1244 suppression rendered normal lung fibroblasts with malignant phenotypes. miR-1244 overexpression can reduce the growth of lung cancer xenografts. miR-1244 was then verified to negatively regulate the expression of myocyte enhancer factor 2D (MEF2D) in lung cancer cells. MEF2D can also affect the expression of miR-1244 by directly binding to its promoter. Further study showed that MEF2D is required for the effect of miR-1244 on lung cancer and normal cells. These results suggested that there is an autoregulatory circuit consisting of miR-1244 and MEF2D, which contributes to the progression of lung cancer. Targeting this molecular loop may be a promising strategy for lung carcinoma treatment.

Comparison of the inhibition capability of oleanolic acid and betulinic acid towards drug-metabolizing enzymes

BACKGROUND

Human UDP-glucuronosyltransferases (UGTs) are important membrane proteins located in endoplasmic reticulum, and play important roles in metabolism of a variety of endogenous and exogenous compounds.

AIMS

To determine the influence of subtle difference in the structure of oleanolic acid and betulinic acid towards the inhibition towards the activity of UGT isoforms.

METHODS

In vitro glucuronidation of 4-methylumbelliferone (4-MU) reaction was employed as the probe reaction to determine the inhibition of these two compounds towards UGTs' activity.

RESULTS

The inhibition of capability of oleanolic acid towards UGT1A6 and UGT1A8 were higher than betulinic acid. However, no significant difference was observed for the inhibition of oleanolic acid and betulinic acid towards UGT1A7. Furthermore, concentration-dependent behaviour was determined for the inhibition of oleanolic acid and betulinic acid towards UGT1A6 and UGT1A8. At various concentrations of oleanolic acid and betulinic acid, the inhibition of oleanolic acid towards UGT1A6 and UGT1A8 was higher than betulinic acid.

CONSLUSION

Given that UGT1A6 and UGT1A8 play key role in the the inhibition of oleanolic acid towards UGT1A6 and UGT1A8 will induce drug-drug interaction and the risk of diseases.

Oleanolic acid induces mitochondrial-dependent apoptosis and G0/G1 phase arrest in gallbladder cancer cells

Oleanolic acid (OA), a naturally occurring triterpenoid, exhibits potential antitumor activity in many tumor cell lines. Gallbladder carcinoma is the most common malignancy of the biliary tract, and is a highly aggressive tumor with an extremely poor prognosis. Unfortunately, the effects of OA on gallbladder carcinoma are unknown. In this study, we investigated the effects of OA on gallbladder cancer cells and the underlying mechanism. The results showed that OA inhibits proliferation of gallbladder cancer cells in a dose-dependent and time-dependent manner on MTT and colony formation assay. A flow cytometry assay revealed apoptosis and G0/G1 phase arrest in GBC-SD and NOZ cells. Western blot analysis and a mitochondrial membrane potential assay demonstrated that OA functions through the mitochondrial apoptosis pathway. Moreover, this drug inhibited tumor growth in nude mice carrying subcutaneous NOZ tumor xenografts. These data suggest that OA inhibits proliferation of gallbladder cancer cells by regulating apoptosis and the cell cycle process. Thus, OA may be a promising drug for adjuvant chemotherapy in gallbladder carcinoma.

The role of Cyclin G1 in cellular proliferation and apoptosis of human epithelial ovarian cancer

Cyclin G1 plays an essential role in the development of human carcinoma. Here, we characterized the clinical significance of Cyclin G1 and investigated its role in cellular proliferation and apoptosis of epithelial ovarian cancer (EOC). Western blot was used to evaluate the expression of Cyclin G1 in nine fresh EOC tissues and three fresh normal ovarian tissues. Immunohistochemistry analysis was performed on formalin-fixed paraffin-embedded section of 119 cases of EOCs. Using cell counting kit (CCK)-8 and colony formation assays, we analyzed the effect of Cyclin G1 in cellular proliferation of EOC. Besides, the immunofluorescence and flow cytometry analysis was performed to study the role of Cyclin G1 in cellular apoptosis of EOC. We found Cyclin G1 was up-regulated in EOC tissues compared with the normal ovary tissues. Cyclin G1 expression in EOC was closely correlated with differentiation grade (P = 0.009) and malignant tumor cells in ascites (P = 0.009). The Kaplan-Meier curve showed that higher expression of Cyclin G1 was associated with significantly shorter survival in EOC patients. Multivariate analysis suggested Cyclin G1 expression was an independent prognostic factor for overall survival. CCK-8 and colony formation assays revealed that depletion of Cyclin G1 inhibited the proliferation and clone formation. Combined immunofluorescence and flow cytometry analysis showed that silencing of Cyclin G1 with shRNA could promote apoptosis of ovarian cancer cells. Additionally, the result of immunoprecipitation test showed Cyclin G1 interacted with CDK2 in EOC cells. In summary, our findings suggest that Cyclin G1 may be involved in the prognosis of EOC patients and be a useful therapeutic target for EOC.

Oleanolic Acid Loaded PEGylated PLA and PLGA Nanoparticles with Enhanced Cytotoxic Activity against Cancer Cells

Oleanolic acid (OA) is a natural triterpenoid with anticancer properties, but its hydrophobic nature and poor aqueous solubility pose challenges in pharmaceutical formulation development. The present study aimed at developing OA-loaded mPEG-PLGA or mPEG-PLA nanoparticles (NPs) to improve the delivery of OA. The NPs were prepared by nanoprecipitation, and their physicochemical properties were characterized. The OA encapsulation efficiency of the NPs was between 40 and 75%. The size of the OA-loaded NPs was around 200-250 nm, which fell within the range required for tumor targeting by means of the enhanced permeability and retention (EPR) effect, and the negatively charged NPs remained physically stable for over 20 weeks with no aggregation observed. The OA-loaded NPs produced significant cytotoxic effects through apoptosis in cancer cell lines. Overall, the OA-loaded mPEG-PLGA NPs and mPEG-PLA NPs shared similar physicochemical properties. The former, especially the OA-loaded mPEG-P(D,L)LGA NPs, were more cytotoxic to cancer cells and therefore were more efficient for OA delivery.