Pristimerin causes G1 arrest, induces apoptosis, and enhances the chemosensitivity to gemcitabine in pancreatic cancer cells

Synthesis of 1,10-Phenanthroline-2,9-bistriazoles: Evaluation as G-Quadruplex Binders and Anti-Tumor Activity

Novel 1,10-phenanthroline-2,9-bistriazoles derivatives have been synthesized by copper-catalyzed azide/alkyne cycloaddition reactions and assessed for their ability to bind and stabilize G-quadruplex (G4) structures. Ten novel compounds were evaluated using Förster resonance energy transfer (FRET) melting, circular dichroism (CD), and fluorescence spectroscopy on several G4 sequences. Biophysical characterization led to the identification of compounds 4 a, 4 b, and 5 b as good G4 ligands of KRAS G4 sequences. The impact on cell viability of all derivatives was also assessed, revealing weak effects. However, compound 2 a exhibited cytotoxicity activity on A549 and H1299 cancer cells and low cytotoxicity towards MRC-5 non-malignant cells MRC-5 not connected with its G4-binding ability. Flow cytometry showed that 2 a induced a cell viability decrease in S and G2/M phases for A549 and H1299; thus, more studies should be performed to explore the proteins involved in cell cycle regulation.

Pristimerin Exerts Pharmacological Effects Through Multiple Signaling Pathways: A Comprehensive Review

Pristimerin, a natural triterpenoid isolated from the plants of southern snake vine and Maidenwood in the family Weseraceae, is anti-inflammatory, insecticidal, antibacterial, and antiviral substance and has been used for its cardioprotective and antitumor effects and in osteoporosis treatment. These qualities explain Pristimerin's therapeutic effects on different types of tumors and other diseases. More and more studies have shown that pristimerin acts in a wide range of biological activities and has shown great potential in various fields of modern and Chinese medicine. While Pristimerin's wide range of pharmacological effects have been widely studied by others, our comprehensive review suggests that its mechanism of action may be through affecting fundamental cellular events, including blocking the cell cycle, inducing apoptosis and autophagy, and inhibiting cell migration and invasion, or through activating or inhibiting certain key molecules in several cell signaling pathways, including nuclear factor κB (NF-κB), phosphatidylinositol 3-kinase/protein kinase B/mammalian-targeted macromycin (PI3K/Akt/mTOR), mitogen-activated protein kinases (MAPKs), extracellular signal-regulated protein kinase 1/2 (ERK1/2), Jun amino-terminal kinase (JNK1/2/3), reactive oxygen species (ROS), wingless/integrin1 (Wnt)/β-catenin, and other signaling pathways. This paper reviews the research progress of Pristimerin's pharmacological mechanism of action in recent years to provide a theoretical basis for the molecular targeting therapy and further development and utilization of Pristimerin. It also provides insights into improved treatments and therapies for clinical patients and the need to explore pristimerin as a potential facet of treatment.

Anticancer Potential and Molecular Targets of Pristimerin in Human Malignancies

The growing global burden of malignant tumors with increasing incidence and mortality rates underscores the urgent need for more effective and less toxic therapeutic options. Herbal compounds are being increasingly studied for their potential to meet these needs due to their reduced side effects and significant efficacy. Pristimerin (PS), a triterpenoid from the quinone formamide class derived from the Celastraceae and Hippocrateaceae families, has emerged as a potent anticancer agent. It exhibits broad-spectrum anti-tumor activity across various cancers such as breast, pancreatic, prostate, glioblastoma, colorectal, cervical, and lung cancers. PS modulates several key cellular processes, including apoptosis, autophagy, cell migration and invasion, angiogenesis, and resistance to chemotherapy, targeting crucial signaling pathways such as those involving NF-κB, p53, and STAT3, among others. The main objective of this review is to provide a comprehensive synthesis of the current literature on PS, emphasizing its mechanisms of action and molecular targets with the utmost clarity. It discusses the comparative advantages of PS over current cancer therapies and explores the implications for future research and clinical applications. By delineating the specific pathways and targets affected by PS, this review seeks to offer valuable insights and directions for future research in this field. The information gathered in this review could pave the way for the successful development of PS into a clinically applicable anticancer therapy.

ACAT1 promotes proliferation and metastasis of bladder cancer via AKT/GSK3β/c-Myc signaling pathway

Acetyl-CoA acetyltransferase 1 (ACAT1) plays a significant role in the regulation of gene expression and tumorigenesis. However, the biological role of ACAT1 in bladder cancer (BLCA) has yet to be elucidated. This research aimed to elucidate the bioinformatics features and biological functions of ACAT1 in BLCA. Here, we demonstrate that ACAT1 is elevated in BLCA tissues and is correlated with specific clinicopathological features and an unfavorable prognosis for survival in BLCA patients. ACAT1 was identified as an independent risk factor in BLCA. Phenotypically, both in vitro and in vivo, ACAT1 knockdown suppressed BLCA cell proliferation and migration, while ACAT1 overexpression had the opposite effect. Mechanistic assays revealed that ACAT1 enhances BLCA cell proliferation and metastasis through the AKT/GSK3β/c-Myc signaling pathway by modulating the cell cycle and EMT. Taken together, the results of our study reveal that ACAT1 is an oncogenic driver in BLCA that enhances tumor proliferation and metastasis, indicating its potential as a diagnostic and therapeutic target for this disease.

Analysis of signaling cascades from myeloma cells treated with pristimerin

Multiple myeloma (MM) is the 2nd most frequently diagnosed blood cancer after non-Hodgkin's lymphoma. The present study aimed to identify the differentially expressed genes (DEGs) between the control and pristimerin-treated MM cell lines. We examined the GSE14011 microarray dataset and screened DEGs with GEO2R statistical tool using the inbuilt limma package. We used a bioinformatics pipeline to identify the differential networks, signaling cascades, and the survival of the hub genes. We implemented two different enrichment analysis including ClueGO and Metacore™, to get accurate annotation for most significant DEGs. We screened the most significant 408 DEGs from the dataset based on p-values and logFC values. Using protein network analysis, we found the genes UBC, HSP90AB1, HSPH1, HSPA1B, HSPA1L, HSPA6, HSPD1, DNAJB1, HSPE1, DNAJC10, BAG3, and DNAJC7 had higher node degree distribution. In contrast, the functional annotation provided that the DEGs were predominantly enriched in B-cell receptor signaling, unfolded protein response, positive regulation of phagocytosis, HSP70, and HSP40-dependent folding, and ubiquitin-proteasomal proteolysis. Using network algorithms, and comparing enrichment analysis, we found the hub genes enriched were INHBE, UBC, HSPA1A, HSP90AB1, IKBKB, and BAG3. These DEGs were further validated with overall survival and gene expression analysis between the tumor and control groups. Finally, pristimerin effects were validated independently in a cell line model consisting of IM9 and U266 MM cells. Pristimerin induced in vitro cytotoxicity in MM cells in a dose-dependent manner. Pristimerin inhibited NF-κB, induced accumulation of ubiquitinated proteins and inhibited HSP60 in the validation of bioinformatics findings, while pristimerin-induced caspase-3 and PARP cleavage confirmed cell death. Taken together, we found that the identified DEGs were strongly associated with the apoptosis induced in MM cell lines due to pristimerin treatment, and combinatorial therapy derived from pristimerin could act as novel anti-myeloma multifunctional agents.

STIL Promotes Tumorigenesis of Bladder Cancer by Activating PI3K/AKT/mTOR Signaling Pathway and Targeting C-Myc

SCL/TAL1 interrupting locus (STIL) regulates centriole replication and causes chromosome instability, which is closely related to malignant tumors. The purpose of our study was to investigate the role of STIL in bladder cancer (BC) tumorigenesis for the first time. The public database indicated that STIL is highly expressed and correlated with the cell cycle in BC. Immunohistochemistry staining showed that STIL expression is significantly elevated in BC tissues compared with paracancer tissues. CRISPR-Cas9 gene editing technology was used to induce BC cells to express STIL-specific sgRNA, revealing a significantly delayed growth rate in STIL knockout BC cells. Moreover, cell cycle arrest in the G0/G1 phase was triggered by decreasing STIL, which led to delayed BC cell growth in vitro and in vivo. Mechanically, STIL knockout inhibited the PI3K/AKT/mTOR pathway and down-regulated the expression of c-myc. Furthermore, SC79 (AKT activating agent) partially reversed the inhibitory effects of STIL knockout on the proliferation and migration of BC cells. In conclusion, STIL enhanced the PI3K/AKT/mTOR pathway, resulting in increased expression of c-myc, ultimately promoting BC occurrence and progression. These results indicate that STIL might be a potential target for BC patients.

The multifaceted mechanisms of pristimerin in the treatment of tumors state-of-the-art

As a globally complicated disease, malignant tumor has long been posing a threat to human health with increasingly high morbidity and mortality. Notably, existing treatments for tumors like chemotherapy generally carry intolerable toxicity, necessitating novel agents balancing safety and potency. Among them, the anti-tumor potency of herbs, featuring few adverse effects and promising efficacy, has attracted much attention recently. Pristimerin, a Quinone formamide triterpenoid compound extracted from Celastraceae and Portulacaceae, carries pronounced anti-tumor activity. It applies to various malignant tumors, including breast cancer, bile duct cancer, gastric cancer, pancreatic cancer, prostate cancer, glioblastoma, colorectal cancer, oral squamous cell carcinoma, cervical cancer, and lung cancer. In state-of-the-art understanding, pristimerin, alone or combined, can inhibit tumor cell proliferation, induce tumor cell apoptosis, inhibit tumor migration and invasion, inhibit angiogenesis, induce tumor cell autophagy, regulate the occurrence of inflammation related tumors, enhance chemosensitivity and regulate tumor microenvironment and immune cells. Despite the abundance of pristimerin-based research, systematic reviews on its anti-tumor mechanism remain needed. This study presented the anti-tumor mechanism of pristimerin by literature review, which might serve as a reference for further research and clinical practice.

Cellular and Molecular Mechanisms of Pristimerin in Cancer Therapy: Recent Advances

Seeking an efficient and safe approach to eliminate tumors is a common goal of medical fields. Over these years, traditional Chinese medicine has attracted growing attention in cancer treatment due to its long history. Pristimerin is a naturally occurring quinone methide triterpenoid used in traditional Chinese medicine to treat various cancers. Recent studies have identified alterations in cellular events and molecular signaling targets of cancer cells under pristimerin treatment. Pristimerin induces cell cycle arrest, apoptosis, and autophagy to exhibit anti-proliferation effects against tumors. Pristimerin also inhibits the invasion, migration, and metastasis of tumor cells via affecting cell adhesion, cytoskeleton, epithelial-mesenchymal transition, cancer stem cells, and angiogenesis. Molecular factors and pathways are associated with the anti-cancer activities of pristimerin. Furthermore, pristimerin reverses multidrug resistance of cancer cells and exerts synergizing effects with other chemotherapeutic drugs. This review aims to discuss the anti-cancer potentials of pristimerin, emphasizing multi-targeted biological and molecular regulations in cancers. Further investigations and clinical trials are warranted to understand the advantages and disadvantages of pristimerin treatment much better.

Pristimerin Protects Against OVX-Mediated Bone Loss by Attenuating Osteoclast Formation and Activity via Inhibition of RANKL-Mediated Activation of NF-κB and ERK Signaling Pathways

Introduction

Osteoporosis is an osteolytic bone condition characterized by decreased bone strength and increased bone fragility. It is the result of elevated formation or activity of bone-resorbing osteoclasts. Although current therapeutic agents are efficacious against osteoclast-mediated bone loss, detrimental side effects preclude the long-term use of these agents. Pristimerin (PRI) is a naturally occurring quinone-methide triterpenoid that has been revealed to exert anti-inflammatory and anti-tumor effects via regulating various signaling cascades including NF-κB and MAPK activation.

Methods

The bone marrow macrophages were used to confirm the anti-osteoclastic and anti-resorptive functions of PRI in vitro. An in vivo ovariectomy (OVX) model was applied to verify the function of PRI protecting bone loss.

Results

PRI abolished the early activation of NF-κB and ERK MAPK signal cascades thereby thwarting the downstream expression of c-Fos and NFATc1, which prevented the production of mature osteoclasts. In vivo, PRI protects mice against ovariectomy (OVX)-mediated bone loss by diminishing osteoclast formation and bone resorptive activity.

Conclusion

Our study shows that PRI demonstrates therapeutic potential in the effective treatment against osteoclast-induced osteolytic diseases like osteoporosis.

Long non-coding RNA MEG3 inhibits M2 macrophage polarization by activating TRAF6 via microRNA-223 down-regulation in viral myocarditis

Viral myocarditis (VMC) commonly triggers heart failure, for which no specific treatments are available. This study aims to explore the specific role of long non‐coding RNA (lncRNA) maternally expressed 3 (MEG3) in VMC. A VMC mouse model was induced by Coxsackievirus B3 (CVB3). Then, MEG3 and TNF receptor‐associated factor 6 (TRAF6) were silenced and microRNA‐223 (miR‐223) was over‐expressed in the VMC mice, followed by determination of ventricular ejection fraction (LVEF) and left ventricular fractional shortening (LVFS). Dual‐luciferase reporter assay was introduced to test the interaction among MEG3, TRAF6 and miR‐223. Macrophages were isolated from cardiac tissues and bone marrow, and polarization of M1 or M2 macrophages was induced. Then, the expressions of components of NLRP3 inflammatory body (NLRP3, ASC, Caspase‐1), M1 markers (CD86, iNOS and TNF‐α) and M2 markers (CD206, Arginase‐1 and Fizz‐1) were measured following MEG3 silencing. In the VMC mouse model, MEG3 and TRAF6 levels were obviously increased, while miR‐223 expression was significantly reduced. Down‐regulation of MEG3 resulted in the inhibition of TRAF6 by promoting miR‐223. TRAF6 was negatively correlated with miR‐223, but positively correlated with MEG3 expression. Down‐regulations of MEG3 or TRAF6 or up‐regulation of miR‐223 was observed to increase mouse weight, survival rate, LVEF and LVFS, while inhibiting myocarditis and inflammation via the NF‐κB pathway inactivation in VMC mice. Down‐regulation of MEG3 decreased M1 macrophage polarization and elevated M2 macrophage polarization by up‐regulating miR‐223. Collectively, down‐regulation of MEG3 leads to the inhibition of inflammation and induces M2 macrophage polarization via miR‐223/TRAF6/NF‐κB axis, thus alleviating VMC.

Prothrombotic effects of high uric acid in mice via activation of MEF2C-dependent NF-κB pathway by upregulating let-7c

Serum uric acid is reportedly associated with thrombosis development. However, still unclear is the mechanism of high uric acid in thrombosis with the involvement of let-7c. In an aim to fill this void, we conducted this study by treating mice and human umbilical vein endothelial cells with high uric acid. Analysis indicated that let-7c was upregulated in hyperuricemia patients as well as in mice and human umbilical vein endothelial cells treated with high uric acid. Furthermore, high uric acid inhibited myocyte enhancer factor-2C, but activated nuclear factor-kappa B pathway in human umbilical vein endothelial cells. Then the targeting relationship between let-7c and myocyte enhancer factor-2C was verified. On the one hand, high uric acid shortened activated partial thromboplastin time and prothrombin time of mice and declined tissue plasminogen activator level. Additionally, the treatment prolonged thrombin time and elevated the levels of thrombosis related molecules or proteins such as Fibrinogen and D-dimer. Nevertheless, these alternations could be reversed by inhibition of let-7c and nuclear factor-kappa B pathway or overexpressing myocyte enhancer factor-2C. To sum up, our results uncovered the pro-thrombotic effect of high uric acid in mice by activating myocyte enhancer factor-2C-dependent nuclear factor-kappa B pathway via let-7c upregulation.

Overexpression of KLF5 is associated with poor survival and G1/S progression in pancreatic cancer

Despite improvements in surgical procedures and comprehensive therapies, pancreatic cancer remains one of the most aggressive and deadly human malignancies. It is therefore necessary to determine which cellular mediators associate with prognosis in pancreatic cancer so as to improve the treatment of this disease. In the present study, mRNA array and immunohistochemical analyses showed that KLF5 is highly expressed in tissue samples from three short-surviving patients with pancreatic cancer. Survival analysis using data from The Cancer Genome Atlas showed that patients highly expressing KLF5 exhibited shorter overall and tumor-free survival times. Mechanistically, KLF5 promoted expression of E2F1, cyclin D1 and Rad51, while inhibiting expression of p16 in pancreatic cancer cells. Finally, flow cytometric analyses verified that KLF5 promotes G1/S progression of the cell cycle in pancreatic cancer cells. Collectively, these findings demonstrate that KLF5 is an important prognostic biomarker in pancreatic cancer patients, and they shed light on the molecular mechanism by which KLF5 stimulates cell cycle progression in pancreatic cancer.

Pristimerin-induced uveal melanoma cell death via inhibiting PI3K/Akt/FoxO3a signalling pathway

Uveal melanoma (UM) is a highly invasive intraocular malignancy with high mortality. Presently, there is no FDA‐approved standard for the treatment of metastatic UM. Pristimerin is a natural quinine methide triterpenoid compound with anti‐angiogenic, anti‐cancer and anti‐inflammatory activities. However, Pristimerin potential cytotoxic effect on UM was poorly investigated. In the present study, we found the migration and invasion of UM‐1 cells were inhibited by Pristimerin which also caused a rapid increase of ROS, decreased mitochondrial membrane potential, induced the accumulation of cells in G0/G1 phase, ending with apoptotic cell death. Pristimerin inhibited Akt and FoxO3a phosphorylation and induced nuclear accumulation of FoxO3a in UM‐1 cells, increased the expression of pro‐apoptotic proteins Bim、p27^Kip1, cleaved caspase‐3, PARP and Bax, and decreased the expression of Cyclin D1 and Bcl‐2. LY294002 or Akt‐siRNA inhibited the PI3K/Akt/FoxO3a pathway and promoted the Pristimerin‐induced apoptosis, while Pristimerin effects were partially abolished in FoxO3a knockdown UM‐1 cell cultures. Taken together, present results showed that Pristimerin induced apoptotic cell death through inhibition of PI3K/Akt/FoxO3a pathway in UM‐1 cells. These findings indicate that Pristimerin may be considered as a potential chemotherapeutic agent for patients with UM.

Anti-Cancer Effects of Pristimerin and the Mechanisms: A Critical Review

As a quinonemethide triterpenoid extracted from species of the Celastraceae and Hippocrateaceae, pristimerin has been shown potent anti-cancer effects. Specifically, it was found that pristimerin can affect many tumor-related processes, such as apoptosis, autophagy, migration and invasion, vasculogenesis, and drug resistance. Various molecular targets or signaling pathways are also involved, such as cyclins, reactive oxygen species (ROS), microRNA, nuclear factor kappa B (NF-κB), mitogen-activated protein kinase (MAPK), and PI3K/AKT/mammalian target of rapamycin (mTOR) pathways. In this review, we will focus on the research about pristimerin-induced anti-cancer activities to achieve a deeper understanding of the targets and mechanisms, which offer evidences suggesting that pristimerin can be a potent anti-cancer drug.

Induction of cell-cycle arrest and apoptosis in human cholangiocarcinoma cells by pristimerin

Pristimerin, a triterpenoid isolated from Celastraceae and Hippocrateaceae, is known to induce cytotoxicity in several cancer cell lines. However, whether pristimerin can induce apoptosis in cholangiocarcinoma cells and the underlying mechanism remain unexplored. We assessed the function of human cholangiocarcinoma QBC and RBE cell lines using various experimental methods such as the cell viability assay to elucidate the viability of cells, flow cytometry to detect the death rate of cells, and Western blot analysis to evaluate the expression of cell cycle-related proteins and autophagy-related proteins. Human cholangiocarcinoma QBC cells were transplanted to nude mice to establish an animal model, and the effect of pristimerin on tumor growth in this model was observed. QBC and RBE cell lines treated with pristimerin (0, 5, 10, and 20 μmol/L) demonstrated the induction of apoptosis in a dose-dependent manner. The cell viability assay revealed a reduction in the cell viability with an increase in the pristimerin concentration. Similarly, flow cytometry revealed a gradual increase in the cell death rate with an increase in the pristimerin concentration. In addition, pristimerin significantly lowered the expression of apoptosis-related proteins (Bcl-2, Bcl-xL, and procaspase-3), but increased the Bax expression. Furthermore, pristimerin resulted in the G0/G1 cell-cycle arrest, reducing the expression of cell cycle-related proteins (cyclin E, CDK2, and CDK4), and increased the expression of autophagy-related proteins (LC3) in QBC cell line. Treatment with pristimerin could inhibit tumor growth in the nude mouse model. Overall, this study suggests the potential effect of pristimerin on the cell-cycle arrest and apoptosis in human cholangiocarcinoma cells.

A Hopeful Natural Product, Pristimerin, Induces Apoptosis, Cell Cycle Arrest, and Autophagy in Esophageal Cancer Cells

Esophageal cancer is one of the most common malignant digestive diseases worldwide. Although many approaches have been established for the treatment of esophageal cancer, the survival outcome has not improved. Pristimerin is a quinone methide triterpenoid with anticancer, antiangiogenic, anti-inflammatory, and antiprotozoal activities. However, the role of pristimerin in cancers such as esophageal cancer is unclear. In this study, we investigated the role and mechanisms of action of pristimerin in esophageal cancer. First, we found that pristimerin can induce apoptosis in esophageal cancer in vivo and in vitro. CCK-8 and clonogenic assays showed that pristimerin decreased the growth of Eca109 cells. In addition, we found that pristimerin decreased the protein expression of CDK2, CDK4, cyclin E, and BCL-2 and increased the expression of CDKN1B. Meanwhile, pristimerin elevated the ratio of LC3-II/LC3-I. Otherwise, downregulation of CDKN1B can reduce the esophageal cancer tumor growth induced by pristimerin. In conclusion, our findings revealed an important role of pristimerin in esophageal cancer and suggest that pristimerin might be a potential therapeutic agent for this cancer.

Pristimerin enhances the effect of cisplatin by inhibiting the miR‑23a/Akt/GSK3β signaling pathway and suppressing autophagy in lung cancer cells

Lung cancer is a common type of cancer with a high mortality rate in China. Cisplatin (Cis) is one of the most effective broad‑spectrum chemotherapeutic drugs for the treatment of advanced lung cancer. However, Cis resistance remains an obstacle in the treatment of advanced lung cancer. Pristimerin (Pris), a naturally occurring triterpenoid quinone compound, not only possesses anticancer properties, but also enhances chemosensitivity. Therefore, the present study aimed to investigate whether Pris can enhance the chemosensitivity of lung cancer cells to Cis and identify the underlying mechanism. A Cell Counting kit‑8 and flow cytometry were used to determine cell viability, cell cycle progression and apoptosis in A549 and NCI‑H446 cells. Western blotting was used to determine cell apoptosis‑related, cell cycle‑related and autophagy‑related proteins. The results showed that Pris inhibited cell proliferation, and induced G0/G1 arrest and cell apoptosis in A549 and NCI‑H446 cells. The western blotting revealed that Pris effectively synergized with Cis to induce cell apoptosis by inhibiting the microRNA‑23a/Akt/glycogen synthase kinase 3β signaling pathway and suppressing autophagy. In vivo xenograft experiments confirmed that Pris effectively synergized with Cis to suppress tumor growth. Collectively, these results indicate that Pris synergized with Cis and that this may be a potential therapeutic strategy to overcome lung cancer.

Pristimerin induces apoptosis of oral squamous cell carcinoma cells via G1 phase arrest and MAPK/Erk1/2 and Akt signaling inhibition

Pristimerin is an active compound isolated from the traditional Chinese herbs Celastraceae and Hippocrateaceae. It has been reported to exert antitumor effects under experimental and clinical conditions; however, the antitumor effects and underlying mechanisms of pristimerin in oral cancer cells have not yet been identified. In the present study, the anticancer potential of pristimerin was investigated in two oral squamous cell carcinoma (OSCC) cell lines, CAL-27 and SCC-25. Results demonstrated that pristimerin was toxic against the two cell lines, and exhibited inhibitory effects against proliferation. Furthermore, pristimerin exhibited a more potent anti-proliferative activity in CAL-27 and SCC-25 cells than the common chemotherapy drugs cisplatin and 5-fluorouracil. In addition, cell cycle distribution analysis revealed that G₀/G₁ phase arrest was induced following pristimerin treatment in CAL-27 and SCC-25 cells, which was strongly associated with upregulation of p21 and p27, coupled with downregulation of cyclin D1 and cyclin E. Meanwhile, pristimerin induced significant apoptosis of CAL-27 and SCC-25 cells, alongside decreased levels of caspase-3 and specific cleavage of poly (ADP-ribose) polymerase. These effects were associated with inhibition of the mitogen-activated protein kinase/extracellular signal-regulated kinase 1/2 and protein kinase B signaling pathways. With regards to these results, pristimerin may be considered a potent novel active substance for the treatment of OSCC.

Induction of apoptosis and G1 phase cell cycle arrest by Aster incisus in AGS gastric adenocarcinoma cells

In recent decades, various bioactive compounds from plants have been investigated for their potential use in the treatment of diseases in humans. Aster incisus extract (AIE) is the extract of a common plant that is mostly found in Asia. It has traditionally been used for medicinal purposes in South Korea. In this study, we evaluated the potential anticancer effects of a methanolic extract of Aster incisus in a normal human cell line (HaCaT keratinocytes) and in 4 different types of human cancer cell lines (A549, lung cancer; Hep3B, liver cancer; MDA‑MB‑231, breast cancer; and AGS, gastric cancer). The HaCaT, A549, Hep3B, MDA‑MB‑231 and AGS cells were treated with various concentrations of AIE and following treatment, cell survival was evaluated. Additional analyses, such as WST-1 assay, western blot analysis, DAPI staining, flow cytometry, immunofluorescence staining and wound healing assay were performed to elucidate the mechanisms and pathways involved in the cell death induced by AIE. Treatment with AIE induced morphological changes and considerably reduced the viability of the both normal and cancer cell lines. Further analysis of the AGS gastric cancer cells revealed that AIE led to the induction of apoptosis and a high accumulation of cells in the G1 cell phase following treatment with AIE in a dose-dependent manner. The results also revealed that AIE successfully suppressed the migration of the AIE-treated AGS cells. The results of western blot analysis indicated that AIE increased the expression of pro-apoptotic proteins, particularly Bid, Bad, Bak, cytochrome c, apoptosis inducing factor (AIF), cleaved caspase‑3, -8 and -9 and cleaved poly(ADP-ribose) polymerase (PARP). Additionally, AIE decreased the expression of the anti-apoptotic proteins, Bcl-2 and Bcl-xL. On the whole, the findings of this study demonstrate that AIE induces apoptosis through the activation of the caspase‑dependent pathway mediated by the mitochondrial pathway and by arresting the cell cycle in AGS cells.

Dihydroartemisinin suppresses pancreatic cancer cells via a microRNA-mRNA regulatory network

Despite improvements in surgical procedures and chemotherapy, pancreatic cancer remains one of the most aggressive and fatal human malignancies, with a low 5-year survival rate of only 8%. Therefore, novel strategies for prevention and treatment are urgently needed. Here, we investigated the mechanisms underlying the anti-pancreatic cancer effects dihydroartemisinin (DHA). Microarray and systematic analysis showed that DHA suppressed proliferation, inhibited angiogenesis and promoted apoptosis in two different human pancreatic cancer cell lines, and that 5 DHA-regulated microRNAs and 11 of their target mRNAs were involved in these effects via 19 microRNA-mRNA interactions. Four of these microRNAs, 9 of the mRNAs and 17 of the interactions were experimentally verified. Furthermore, we found that the anti-pancreatic caner effects of DHA in vivo involved 4 microRNAs, 9 mRNAs and 17 microRNA-mRNA interactions. These results improve the understanding of the mechanisms by which DHA suppresses proliferation and angiogenesis and promotes apoptosis in pancreatic cancer cells and indicate that DHA, an effective antimalarial drug, might improve pancreatic cancer treatments.

Pristimerin, a naturally occurring triterpenoid, attenuates tumorigenesis in experimental colitis-associated colon cancer

BACKGROUND

Pristimerin is a quinonemethide triterpenoid with anti-cancer, anti-angiogenic, anti-inflammatory and anti-protozoal activity. However, the therapeutic role of pristimerin in colitis-associated colorectal carcinogenesis is unknown.

PURPOSE

We sought to examine the therapeutic effects of pristimerin on colitis-associated colon cancer induced in mice using azoxymethane (AOM)/dextran sulfate sodium (DSS). The goal was to identify the potential mechanism of action underlying the pharmacological activity of pristimerin.

METHODS

BALB/c mice were injected with AOM and administered 2% DSS in drinking water. The mice were fed with a diet supplemented with pristimerin (1 to 5 ppm), and colonic tissue was collected at 64 days. The inflammatory status of the colon was assessed by determining the levels of cyclooxygenase-2, inducible nitric oxide synthase and pro-inflammatory cytokines using Western blotting, immunohistochemistry and real-time RT-PCR analyses. Markers of proliferation (proliferating cell nuclear antigen) and apoptosis (TUNEL) were identified in the colon tissues immunohistochemically. The levels of cell cycle-, apoptosis-, and signaling-related proteins were detected by Western blot in colon tissues.

RESULTS

Administration of pristimerin significantly reduced the formation of colonic tumors. Western blot and immunohistological analyses revealed that dietary pristimerin markedly reduced NF-κB-positive cells and levels of inflammation-related proteins in colon tissue. Pristimerin also reduced cell proliferation, induced apoptosis, and decreased the phosphorylation of AKT and FOXO3a in colon tissue.

CONCLUSION

Pristimerin administration decreased inflammation and proliferation induced by AOM/DSS in colon tissue. It also induced apoptosis and regulated the AKT/FOXO3a signaling pathway. Overall, this study indicates the potential value of pristimerin in suppressing colon tumorigenesis.

A Mechanistic Overview of Triptolide and Celastrol, Natural Products from Tripterygium wilfordii Hook F

Triptolide and celastrol are predominantly active natural products isolated from the medicinal plant Tripterygium wilfordii Hook F. These compounds exhibit similar pharmacological activities, including anti-cancer, anti-inflammation, anti-obesity, and anti-diabetic activities. Triptolide and celastrol also provide neuroprotection and prevent cardiovascular and metabolic diseases. However, toxicity restricts the further development of triptolide and celastrol. In this review, we comprehensively review therapeutic targets and mechanisms of action, and translational study of triptolide and celastrol. We systemically discuss the structure-activity-relationship of triptolide, celastrol, and their derivatives. Furthermore, we propose the use of structural derivatives, targeted therapy, and combination treatment as possible solutions to reduce toxicity and increase therapeutic window of these potent natural products from T. wilfordii Hook F.

Pristimerin exhibits in vitro and in vivo anticancer activities through inhibition of nuclear factor-кB signaling pathway in colorectal cancer cells

BACKGROUND

Colorectal cancer (CRC) is one of the most common malignancies associated with high mortality rate worldwide. We previously reported that pristimerin inhibits cell growth and induces apoptosis in CRC cells.

HYPOTHESIS/PURPOSE

To further understand the molecular mechanism by which pristimerin elicits its anticancer activities on colon cancer cells, we investigated its effect on nuclear factor-κB (NF-κB) signaling pathway.

STUDY DESIGN

This study consisted of both in vitro and in vivo experiments involving HCT-116 cell line and xenograft mouse model. Molecular techniques such as qRT-PCR, western blotting and immunofluorescence were used to demonstrate pristimerin in vitro effect on NF-κB signaling pathway; whereas it's in vivo activity was analyzed by western blot and immunohistochemistry on tumor tissues.

RESULTS

Our in vitro results on HCT-116 cells showed that pristimerin inhibited IKK phosphorylation, IкB-α degradations and IкB-α phosphorylation in both dose- and time- dependent manners, which caused suppression of NF-кB p65 phosphorylation, nuclear translocation and accumulation of NF-кB. Moreover, pristimerin was found to inhibit both constitutive activated-NF-кB and tumor necrosis factor-α (TNF-α)- and lipopolysaccharide (LPS)-induced activation of NF-кB signaling pathway. Furthermore, our in vivo results on xenograft animal model revealed that pristimerin inhibited tumor growth mainly through suppressing NF-кB activity in tumor tissues.

CONCLUSION

Pristimerin antitumor activities were mainly mediated through inhibition of NF-кB signaling pathway in colon tumor cells. These findings further explain that pristimerin has the therapeutic potential for targeting colon cancer.

A promising natural product, pristimerin, results in cytotoxicity against breast cancer stem cells in vitro and xenografts in vivo through apoptosis and an incomplete autopaghy in breast cancer

Several natural products have been suggested as effective agents for the treatment of cancer. Given the important role of CSCs (Cancer Stem Cells) in cancer, which is a trendy hypothesis, it is worth investigating the effects of pristimerin on CSCs as well as on the other malignant cells (MCF-7 and MDA-MB-231) of breast cancer. The anti-growth activity of pristimerin against MCF-7 and MCF-7s (cancer stem cell enriched population) cells was investigated by real time viability monitorization (xCELLigence System^®) and ATP assay, respectively. Mode of cell death was evaluated using electron and fluorescence microscopies, western blotting (autophagy, apoptosis and ER-stress related markers) and flow cytometry (annexin-V staining, caspase 3/7 activity, BCL-2 and PI3K expressions). Pristimerin showed an anti-growth effect on cancer cells and cancer stem cells with IC₅₀ values ranging at 0.38-1.75μM. It inhibited sphere formation at relatively lower doses (<1.56μM). Apoptosis was induced in MCF-7 and MCF-7s cells. In addition, extensive cytoplasmic vacuolation was observed, implying an incompleted autophagy as evidenced by the increase of autophagy-related proteins (p62 and LC3-II) with an unfolded protein response (UPR). Pristimerin inhibited the growth of MCF-7 and MDA-MB-231-originated xenografts in NOD.CB17-Prkdc^scid/J mice. In mice, apoptosis was further confirmed by cleavage of PARP, activation of caspase 3 and/or 7 and TUNEL staining. Taken together, pristimerin shows cytotoxic activity on breast cancer both in vitro and in vivo. It seems to represent a robust promising agent for the treatment of breast cancer. Pristimerin's itself or synthetic novel derivatives should be taken into consideration for novel potent anticancer agent(s).

Compounds From Celastraceae Targeting Cancer Pathways and Their Potential Application in Head and Neck Squamous Cell Carcinoma: A Review

Squamous cell carcinoma of the head and neck is one of the most common cancer types worldwide. It initiates on the epithelial lining of the upper aerodigestive tract, at most instances as a consequence of tobacco and alcohol consumption. Treatment options based on conventional therapies or targeted therapies under development have limited efficacy due to multiple genetic alterations typically found in this cancer type. Natural products derived from plants often possess biological activities that may be valuable in the development of new therapeutic agents for cancer treatment. Several genera from the family Celastraceae have been studied in this context. This review reports studies on chemical constituents isolated from species from the Celastraceae family targeting cancer mechanisms studied to date. These results are then correlated with molecular characteristics of head and neck squamous cell carcinoma in an attempt to identify constituents with potential application in the treatment of this complex disease at the molecular level.

Anti-cancer effect of pristimerin by inhibition of HIF-1α involves the SPHK-1 pathway in hypoxic prostate cancer cells

BACKGROUND

Hypoxia is a typical character of locally advanced solid tumours. The transcription factor hypoxia-inducible factor 1α (HIF-1α) is the main regulator under the hypoxic environment. HIF-1α regulates various genes to enhance tumour progression, angiogenesis, and metastasis. Sphingosine kinase 1 (SPHK-1) is a modulator of HIF-1α.

METHODS

To investigate the molecular mechanisms of pristimerin in association with SPHK-1 pathways in hypoxic PC-3 cancer cells. Vascular endothelial growth factor (VEGF) production, cell cycles, and SPHK-1 activity were measured, and western blotting, an MTT assay, and an RNA interference assay were performed.

RESULTS

Pristimerin inhibited HIF-1α accumulation in a concentration- and-time-dependent manner in hypoxic PC-3 cells. Pristimerin suppressed the expression of HIF-1α by inhibiting SPHK-1. Moreover, inhibiting SPHK-1 with a sphingosine kinase inhibitor enhanced the suppression of HIF-1α, phosphorylation AKT, and glycogen synthase kinase-3β (GSK-3β) by pristimerin under hypoxia. Furthermore, a reactive oxygen species (ROS) scavenger enhanced the inhibition of HIF-1α and SPHK-1 by pristimerin.

CONCLUSION

Taken together, these findings suggest that pristimerin can exert an anti-cancer activity by inhibiting HIF-1α through the SPHK-1 pathway.

Long Noncoding RNA MALAT1 Promotes Aggressive Pancreatic Cancer Proliferation and Metastasis via the Stimulation of Autophagy

Recently, pancreatic ductal adenocarcinoma (PDAC) has emerged as one of the most aggressive malignant tumors with the worst prognosis. Previous studies have demonstrated that long noncoding RNA metastasis-associated lung adenocarcinoma transcript 1 (MALAT1) is increased in pancreatic cancer and is identified as a diagnostic biomarker. Nonetheless, the molecular mechanism of elevated MALAT1 levels and tumor aggressiveness remains unknown. In this study, MALAT1 was found to be highly expressed in PDAC tissues, and elevated expression was associated with poorer prognoses. In addition, MALAT1 was positively linearly correlated with the expression of LC3B mRNA. Furthermore, several molecules involved in cellular autophagic flux were modulated following the downregulation of MALAT1, including LC3, P62, and LAMP-2. Mechanistically, we found that MALAT1 interacted with RNA binding protein HuR, and silencing of MALAT1 greatly enhanced the posttranscriptional regulation of TIA-1 and had further effects on inhibiting autophagy. MALAT1 was speculated to regulate tumorigenesis via HuR-TIA-1-mediated autophagic activation. Hence, we investigated the biological properties of MALAT1 in terms of tumor proliferation and metastasis by promoting autophagy in vitro In brief, these data demonstrate that MALAT1 could facilitate the advanced progression of tumors in vivo Our study highlights the new roles of MALAT1 on protumorigenic functioning and anticancer therapy via activating autophagy in pancreatic cancer. Mol Cancer Ther; 15(9); 2232-43. ©2016 AACR.

Pristimerin inhibits growth and induces apoptosis of gastric cancer MGC803 and SGC7901 cells

AIM: To investigate the effects of pristimerin on the growth and apoptosis of gastric cancer MGC803 and SGC7901 cells, and to preliminarily explore its action mechanism.

METHODS: MGC803 and SGC7901 cells were cultured in vitro. After treatment with pristimerin, CCK-8 assay, Annexin V-FITC/PI staining, and cell cycle analysis were conducted to investigate the effects of pristimerin on the growth and apoptosis of MGC803 and SGC7901 cells, and then the mitochondrial membrane potential and Bax and Bcl-2 protein expression were determined by Rhodamine 123 staining and Western blot, respectively. Human gastric cancer MGC803 cells were transplanted to nude mice to establish an animal model, and the effect of pristimerin on tumor growth in this model was observed.

RESULTS: Pristimerin inhibited MGC803 and SGC7901 cell growth, with the IC₅₀ values of 8.5 and 12.6 μmol/L, respectively. Annexin-V/PI staining showed that pristimerin induced the apoptosis of MGC803 and SGC7901 cells in a dose-dependent manner. The cell cycle analysis revealed that pristimerin could induce a G₁-phase arrest. Treatment with pristimerin significantly decreased the mitochondrial membrane potential. Treatment with pristimerin increased the expression of Bax protein and decreased the expression of Bcl-2 in a concentration-dependent manner. Treatment with pristimerin could inhibit tumor growth in the nude mouse model.

CONCLUSION: Pristimerin could inhibit proliferation and induce apoptosis of gastric cancer MGC803 and SGC7901 cells, possibly by inducing the loss of mitochondrial membrane potential.

Piperlongumine Suppresses Growth and Sensitizes Pancreatic Tumors to Gemcitabine in a Xenograft Mouse Model by Modulating the NF-kappa B Pathway

Pancreatic cancer is an aggressive malignancy, which generally respond poorly to chemotherapy. Hence, novel agents that are safe and effective are highly needed. The aim of this study was to investigate whether piperlongumine, a natural product isolated from the fruit of the pepper Piper longum, has any efficacy against human pancreatic cancer when used either alone or in combination with gemcitabine in vitro and in a xenograft mouse model. In vitro, piperlongumine inhibited the proliferation of pancreatic cancer cell lines, potentiated the apoptotic effects of gemcitabine, inhibited the constitutive and inducible activation of NF-κB, and suppressed the NF-κB-regulated expression of c-Myc, cyclin D1, Bcl-2, Bcl-xL, Survivin, XIAP, VEGF, and matrix metalloproteinase-9 (MMP-9). Furthermore, in an in vivo xenograft model, we found piperlongumine alone significantly suppressed tumor growth and enhanced the antitumor properties of gemcitabine. These results were consistent with the downregulation of NF-κB activity and its target genes, decreased proliferation (PCNA and Ki-67), decreased microvessel density (CD31), and increased apoptosis (TUNEL) in tumor remnants. Collectively, our results suggest that piperlongumine alone exhibits significant antitumor effects against human pancreatic cancer and it further enhances the therapeutic effects of gemcitabine, possibly through the modulation of NF-κB- and NF-κB-regulated gene products.

Interplay Between Gemcitabine and Erlotinib Over Pancreatic Adenocarcinoma Cells

OBJECTIVES

Pancreatic ductal adenocarcinoma remains as a chemoresistant disease with the poorest prognosis. Gemcitabine has been the standard treatment during the last decade. Erlotinib, a tyrosine kinase inhibitor, in combination with gemcitabine produces a small increase in survival. However, these results remain insufficient. The aim of this study was to investigate the molecular interplay in vitro between them regarding their effects over cytotoxicity, proliferation, apoptosis, and invasion.

METHODS

Using the human pancreatic cancer cell lines Panc-1 and BxPC-3 in vitro, the effects of gemcitabine and erlotinib therapy on growth, proliferation, and invasion were tested by cytotoxicity, cell cycle, and Annexin V-Fluorescein Isothiocyanate analysis, reverse transcription polymerase chain reaction, protein expression, and Chip assays.

RESULTS

Therapy decreased cell proliferation causing G0/G1 phase cell cycle arrest with induction of apoptosis in the Panc-1 cell line. This blockade was associated with increased p27 expression. Besides, treatments enhanced the nuclear factor-κB (NF-κB) pathway and the binding of NF-κB to the promoters of genes related to the proliferation and the evasion of apoptosis.

CONCLUSIONS

Our data suggest that, although gemcitabine and erlotinib exert antiproliferative effects over pancreatic cancer cell lines, the gemcitabine-induced activation of NF-κB expression and its DNA-binding activities are important drawbacks of this treatment against pancreatic cancer.

Non-aqueous extracts of Curcuma mangga rhizomes induced cell death in human colorectal adenocarcinoma cell line (HT29) via induction of apoptosis and cell cycle arrest at G0/G1 phase

OBJECTIVE

To investigate the cytotoxic activity of the hexane and ethyl acetate extracts of Curcuma mangga rhizomes against human colorectal adenocarcinoma cell lines (HT29).

METHODS

The cytotoxic activity of the hexane and ethyl acetate extracts of Curcuma mangga rhizomes against human colorectal adenocarcinoma cell lines (HT29) was determined by using the SRB assay.

RESULTS

The ethyl acetate extract showed a higher cytotoxic effect compared to the hexane extract. Morphological changes of the HT29 cells such as cell shrinkage, membrane blebbling and formation of apoptotic bodies while changes in nuclear morphology like chromatin condensation and nuclear fragmentation were observed. Further evidence of apoptosis in HT29 cells was further supported by the externalization of phosphatidylserine which indicate early sign of apoptosis.

CONCLUSIONS

The early sign of apoptosis is consistent with the cell cycle arrest at the G0/G1 checkpoint which suggests that the changes on the cell cycle lead to the induction of apoptosis in HT29.

Hyperoside induces apoptosis and inhibits growth in pancreatic cancer via Bcl-2 family and NF-κB signaling pathway both in vitro and in vivo

Although advanced surgical operation and chemotherapy have been under taken, pancreatic cancer remains one of the most aggressive and fatal human malignancies with a low 5-year survival rate of less than 5 %. Therefore, novel therapeutic strategies for prevention and remedy are urgently needed in pancreatic cancer. This present research aimed to investigate the anti-cancer effects of hyperoside in human pancreatic cancer cells. Our in vitro results showed that hyperoside suppressed the proliferation and promoted apoptosis of two different human pancreatic cancer cell lines, which correlated with up-regulation of the ratios of Bax/Bcl-2 and Bcl-xL and down-regulation of levels of nuclear factor-κB (NF-κB) and NF-κB's downstream gene products. What's more, using an orthotopic model of human pancreatic cancer, we found that hyperoside also inhibited the tumor growth significantly. Mechanically, these outcomes could also be associated with the up-regulation of the ratios of Bax/Bcl-2 and Bcl-xL and down-regulation of levels of NF-κB and NF-κB's downstream gene products. Collectively, our experiments indicate that hyperoside may be a promising candidate agent for the treatment of pancreatic cancer.

Pristimerin demonstrates anticancer potential in colorectal cancer cells by inducing G1 phase arrest and apoptosis and suppressing various pro-survival signaling proteins

Pristimerin is a naturally occurring triterpenoid that has a cytotoxic effect on several cancer cell lines. However, the cytotoxic effects of pristimerin as well as its molecular mechanisms of action against colorectal cancer have never been explored. In the present study, we investigated the anticancer potential of pristimerin, and examined the different signaling pathways affected by its action in three colon cancer cell lines namely HCT-116, COLO-205 and SW-620. Pristimerin was found to possess potent cytotoxic and proliferation inhibitory effects against these cell lines. Cell cycle analysis revealed G1 phase arrest, which was strongly associated with decreased expression of cyclin D1 and cyclin-dependent kinases (cdk4 and cdk6) with concomitant induction of p21. Pristimerin also induced apoptosis in a dose-dependent manner. Cell plasma membrane alterations studied by Annexin V/PI double staining, loss of mitochondrial membrane potential (ΔΨm), measurements of caspase activities and the inhibitory effect of Z-VAD-FMK (a caspase inhibitor) confirmed the apoptotic effect of pristimerin. Moreover, western blot data showed that apoptotic induction was associated with activated caspase-3 and -8, PARP-1 cleavage and modulation of the expression levels of Bcl-2 family proteins. Additionally, pristimerin treatment downregulated the phosphorylated forms of EGFR and HER2 proteins, and subsequently caused a decrease in the phosphorylated forms of Erk1/2, Akt, mTOR and NF-κB proteins. Taken together, these results suggest that pristimerin may have potential as a new targeting therapeutic strategy for the treatment of colon cancer.

Inhibition of hTERT/telomerase contributes to the antitumor activity of pristimerin in pancreatic ductal adenocarcinoma cells

Pristimerin (PM) is a promising anticancer agent that has exhibited strong antiproliferative and apoptosis-inducing activity in various types of cancer cells. In the present study, we investigated the role of telomerase in mediating the antitumor activity of PM in pancreatic ductal adenocarcinoma (PDA) cells. PM inhibited cell proliferation, arrested cells in the G1 cell cycle phase and induced apoptosis in MiaPaCa-2 and Panc-1 PDA cells. These antitumor activities of PM correlated well with the inhibition of human telomerase reverse transcriptase (hTERT), the gene that codes for the catalytic subunit of telomerase complex. Gene knockin and knockdown approaches demonstrated that hTERT regulates the response of PDA cells to PM. PM inhibited hTERT expression by suppressing the transcription factors Sp1, c-Myc and NF-κB which control hTERT gene expression. PM also inhibited protein kinase Akt, which phosphorylates and facilitates hTERT nuclear importation and its telomerase activity. These findings identified hTERT (telomerase) as a potential therapeutic target of PM for the treatment of PDA.

Effect of NF-κB inhibition on chemoresistance in biliary-pancreatic cancer

Biliary cancer and pancreatic cancer are considered to be difficult diseases to cure. Although complete resection provides the only means of curing these cancers, the rate of resectability is not high. Therefore, chemotherapy is often selected in patients with advanced unresectable biliary-pancreatic cancer. Many combination chemotherapy regimens have been applied in clinical trials. However, the survival time is not satisfactory. On the other hand, most chemotherapeutic agents induce anti-apoptotic transcriptional factor nuclear factor kappa b (NF-κB) activation, and agent-induced NF-κB activation is deeply involved in the onset of chemoresistance. Recently, novel approaches to potentiating chemosensitivity in cases of biliary-pancreatic cancer using NF-κB inhibitors with cytotoxic agents have been reported, most of which comprise translational research, although some clinical trials have also been conducted. Nevertheless, to date, there is no breakthrough chemotherapy regimen for these diseases. As some reports show promising data, combination chemotherapy consisting of a NF-κB inhibitor with chemotherapeutic agents seems to improve chemosensitivity and prolong the survival time of biliary-pancreatic cancer patients.

Cytotoxic effects exerted by pentachlorophenol by targeting nodal pro-survival signaling pathways in human pancreatic cancer cells

Pancreatic adenocarcinoma is one of the deadliest human solid tumors in the developed countries characterized by high resistance toward chemotherapeutic treatment. We have previously shown that silencing of the pro-survival protein kinase CK2 by RNA interference contributes to enhance the cytotoxicity of the chemotherapeutic agent 2′,2′-difluoro 2′-deoxycytidine (gemcitabine). Initial experiments showed that pentachlorophenol (PCP) inhibits CK2 and induces cell death in human pancreatic cancer cell lines. We report here evidence that exposure of this type of cells to PCP induces caspase-mediated apoptosis, inhibition of the lysosome cysteine protease cathepsin B and mitochondrial membrane depolarization. Beside cellular inhibition of CK2, the analysis of signaling pathways deregulated in pancreatic cancer cells revealed that PCP causes decreased phosphorylation levels of NF-κB/p65, suppresses its nuclear translocation and leads to activation of JNK-mediated stress response. Surprisingly, exposure to PCP results in increased phosphorylation levels of AKT at the canonical S473 and T308 activation sites supporting previous data showing that AKT phosphorylation is not predictive of tumor cell response to treatment. Taken together, our study provides novel insights into the effects induced by the exposure of pancreatic cancer cells to chlorinated aromatic compounds posing the basis for more advanced studies in vivo.

WNT5A modulates cell cycle progression and contributes to the chemoresistance in pancreatic cancer cells

BACKGROUND

Although there are many studies on the mechanism of chemoresistance in cancers, studies on the relations between WNT5A and chemoresistance in pancreatic cancer are rare. The present study was to examine the role of WNT5A in the regulation of cell cycle progression and in chemo-resistance in pancreatic cancer tissues and cell lines.

METHODS

Fresh pancreatic cancer and paracarcinoma tissues were obtained from 32 patients. The expressions of WNT5A, AKT/p-AKT and Cyclin D1 were detected by immunohistochemistry, and the correlation between WNT5A expression and clinicopathological characteristics was analyzed. The relationship between WNT5A expression and gemcitabine resistance was studied in PANC-1 and MIAPaCa2 cell lines. The effect of WNT5A on the regulation of cell cycle and gemcitabine cytotoxicity were investigated. The associations among the expressions of p-AKT, Cyclin D1 and WNT5A were also analyzed in cell lines and the effect of WNT5A on restriction-point (R-point) progression was evaluated.

RESULTS

WNT5A, p-AKT and Cyclin D1 were highly expressed in pancreatic cancer tissues, and the WNT5A expression was correlated with the TNM stages. In vitro, WNT5A expression was associated with gemcitabine chemoresistance. The percentage of cells was increased in G0/G1 phase and decreased in S phase after knockdown of WNT5A in PANC-1. WNT5A promoted Cyclin D1 expression through phosphorylation of AKT which consequently enhanced G1-S transition and gemcitabine resistance. Furthermore, WNT5A enhanced the cell cycle progression toward R-point through regulation of retinoblastoma protein (pRb) and pRb-E2F complex formation.

CONCLUSIONS

WNT5A induced chemoresistance by regulation of G1-S transition in pancreatic cancer cells. WNT5A might serve as a predictor of gemcitabine response and as a potential target for tumor chemotherapy.

Ubiquitin-proteasomal degradation of antiapoptotic survivin facilitates induction of apoptosis in prostate cancer cells by pristimerin

Pristimerin (PM), a quinonemethide triterpenoid, is a promising anticancer agent with potent antiproliferative and apoptosis-inducing activities against cancer cell lines. However, the anticancer activity and mechanisms of PM in prostate cancer cells have not been adequately investigated. Here we report that the degradation of survivin plays an important role in the antiproliferative and proapoptotic effects of PM in carcinoma of the prostate (CaP) cell lines. Treatment with PM inhibited proliferation and induced apoptosis in LNCaP and PC-3 cells as characterized by the loss of cell viability and an increase in Annexin V-binding and cleavage of PARP-1, respectively. The antiproliferative and apoptosis-inducing effects of PM were associated with the inhibition of cell cycle regulatory proteins, antiapoptotic survivin and members of the Bcl-2 family. Data showed that response to PM is regulated by survivin since overexpression of survivin rendered CaP cells resistant to PM. Furthermore, downregulation of survivin by PM was mediated through the ubiquitin-proteasomal degradation. Together, these data demonstrate that pristimerin inhibits proliferation and induces apoptosis in CaP cells by abolishing survivin through the ubiquitin-proteasome pathway.

Pristimerin, a natural anti-tumor triterpenoid, inhibits LPS-induced TNF-α and IL-8 production through down-regulation of ROS-related classical NF-κB pathway in THP-1 cells

Pristimerin, a naturally occurring quinonemethide triterpenoid compound, is known to exert a variety of pharmacological activities. In the present study, we investigated the molecular actions of pristimerin against LPS-induced inflammatory responses in human monocytic THP-1 cells. The results showed that pristimerin inhibited the production of TNF-α and IL-8 in a dose-dependent manner. To explore the possible mechanisms underlying these inhibitions by pristimerin, we examined the intracellular ROS level and the NF-κB protein signaling pathway. Pristimerin clearly scavenged LPS-induced intracellular ROS production. In addition, pristimerin prevented LPS-induced NF-κB activation through the inhibition of phosphorylation of IKKα/β, phosphorylation and degradation of IκBα, as well as phosphorylation and nuclear translocation of NF-κB p65. These findings suggest that pristimerin down-regulates the expression of pro-inflammatory mediators through blocking of NF-κB activation by inhibiting interconnected ROS/IKK/NF-κB signaling pathways.

Use of herbal medicines and natural products: an alternative approach to overcoming the apoptotic resistance of pancreatic cancer

Pancreatic cancer has a poor prognosis with a 5-year survival rate of <5%. It does not respond well to either chemotherapy or radiotherapy, due partly to apoptotic resistance (AR) of the cancer cells. AR has been attributed to certain genetic abnormalities or defects in apoptotic signaling pathways. In pancreatic cancer, significant mutations of K-ras and p53, constitutive activation of NFκB, over-expression of heat shock proteins (Hsp90, Hsp70), histone deacetylase (HDACs) and the activities of other proteins (COX-2, Nrf2 and bcl-2 family members) are closely linked with resistance to apoptosis and invasion. AR has also been associated with aberrant signaling of MAPK, PI3K-AKT, JAK/STAT, SHH, Notch, and Wnt/β-catenin pathways. Strategies targeting these signaling molecules and pathways provide an alternative for overcoming AR in pancreatic cancer. The use of herbal medicines or natural products (HM/NPs) alone or in combination with conventional anti-cancer agents has been shown to produce beneficial effects through actions upon multiple molecular pathways involved in AR. The current standard first-line chemotherapeutic agents for pancreatic cancer are gemcitabine (Gem) or Gem-containing combinations; however, the efficacy is dissatisfied and this limitation is largely attributed to AR. Meanwhile, emerging data have pointed to a combination of HM/NPs that may augment the sensitivity of pancreatic cancer cells to Gem. Greater understanding of how these compounds affect the molecular mechanisms of apoptosis may propel development of HM/NPs as anti-cancer agents and/or adjuvant therapies forward. In this review, we give a critical appraisal of the use of HM/NPs alone and in combination with anti-cancer drugs. We also discuss the potential regulatory mechanisms whereby AR is involved in these protective pathways.

Pristimerin, a quinonemethide triterpenoid, induces apoptosis in pancreatic cancer cells through the inhibition of pro-survival Akt/NF-κB/mTOR signaling proteins and anti-apoptotic Bcl-2

Lack of effective therapeutics for pancreatic cancer at the present time underscores the dire need for safe and effective agents for the treatment of this malignancy. In the present study, we have evaluated the anticancer activity and the mechanism of action of pristimerin (PM), a quinonemethide triterpenoid, against MiaPaCa-2 and Panc-1 pancreatic ductal adenocarcinoma (PDA) cell lines. Treatment with PM inhibited the proliferation and induced apoptosis in both cell lines as characterized by the increased Annexin V-binding and cleavage of PARP-1 and procaspases -3, -8 and -9. PM also induced mitochondrial depolarization and the release of cytochrome c from the mitochondria. The induction of apoptosis by PM was associated with the inhibition of the pro-survival Akt, NF-κB and mTOR signaling proteins and their downstream intermediaries such as Foxo-3α and cyclin D1 (Akt); Cox-2 and VEGF (NF-κB); p-S6K1 and p-4E-BP1 (mTOR) as well as PKCɛ. Treatment with PM also inhibited the expression of anti-apoptotic Bcl-2 and survivin but not Bcl-xL. The downregulation of Bcl-2 by PM was not due to proteasomal or lysosomal proteolytic degradation of Bcl-2, since treatment with PM in the presence of proteasomal inhibitors MG132 or lactacystin (LAC) or calpain inhibitor MG101 failed to block the downregulation of Bcl-2 by PM. On the other hand, RT-PCR analysis showed the inhibition of Bcl-2 mRNA by PM in a dose-related manner, indicating that inhibition of Bcl-2 by PM is mediated through the suppression of Bcl-2 gene expression. Thus, the mechanistic understanding of the antitumor activity of pristimerin could facilitate in vivo efficacy studies of pristimerin for pancreatic cancer.

Shikonin suppresses tumor growth and synergizes with gemcitabine in a pancreatic cancer xenograft model: Involvement of NF-κB signaling pathway

Although gemcitabine is currently the best chemotherapeutic agent available for the treatment of advanced pancreatic cancer, eventual failure of response is a significant clinical problem. Therefore, novel therapeutic approaches against this disease are highly needed. The aim of this study was to evaluate whether shikonin, a naphthoquinone derivative, has potential in the treatment of pancreatic cancer when used either alone or in combination with gemcitabine. Our in vitro results showed that shikonin inhibited the proliferation of three different human pancreatic cancer cell lines and potentiated the cytotoxic effect of gemcitabine, which correlated with the down-regulation of constitutive as well as gemcitabine-induced activation of NF-κB and NF-κB-regulated gene products. Most importantly, using a xenograft model of human pancreatic cancer, we found shikonin alone significantly suppressed tumor growth and argumented the antitumor activity of gemcitabine. These effects also correlated with the down-regulation of NF-κB activity and its target genes, decreased proliferation (PCNA and Ki-67), decreased microvessel density (CD31), and increased apoptosis (TUNEL) in tumor remnants. Collectively, our results suggest that shikonin can suppress the growth of human pancreatic tumors and potentiate the antitumor effects of gemcitabine through the suppression of NF-κB and NF-κB-regulated gene products.

Anticancer activity of pristimerin in ovarian carcinoma cells is mediated through the inhibition of prosurvival Akt/NF-κB/mTOR signaling

Pristimerin isaquinonemethidetriterpenoidthathasshown anticancer activity against some cancer types. However, the antitumor effects of pristimerin (PM) in ovarian cancer cells have not been adequately studied. The objective of the present study was to determine the anticancer activity and its mechanism of action in human ovarian carcinoma cell lines. PM strongly inhibited the proliferation of ovarian cancer cells by inducing apoptosis characterized by increased annexin V-binding, cleavage of poly (ADP-ribose) polymerase (PARP-1) and procaspases-3, -8 and -9. Furthermore, PM caused mitochondrial depolarization. Western blot analysis showed inhibition of prosurvival phospho-AKT (p-AKT), nuclear factor kappa B (NF-κB) (p65) and phospho-mammalian target of rapamycin (p-mTOR) signaling proteins in cells treated with PM. Treatment with PM also inhibited the expression of NF-κB-regulated antiapoptotic Bcl-2, Bcl-xL, c-IAP1 and survivin. Thus, our data showing potent antiproliferative and apoptosis-inducing activity of PM in ovarian carcinoma cells through the inhibition of AKT/ NF-κB/ mTOR signaling pathway warrant further investigation of PM for the management of ovarian cancer.

Pristimerin Induces Apoptosis in Prostate Cancer Cells by Down-regulating Bcl-2 through ROS-dependent Ubiquitin-proteasomal Degradation Pathway

Pristimerin is a quinonemethide triterpenoid with the potential of a promising anticancer agent. Pristimerin (PM) has shown anticancer activity against a range of cancer cell lines, but its activity for prostate cancer has not been adequately investigated. In the present study we have examined the underlying mechanisms of the apoptotic response of the hormone-sensitive (LNCaP) and hormone-refractory (PC-3) prostate cancer cell lines to PM. Treatment with PM induced apoptosis in both cell lines as characterized by increased annexin V-binding and cleavage of PARP-1 and procaspases-3 and -9. It also induced mitochondrial depolarization, cytochrome c release from mitochondria and generation of reactive oxygen species (ROS). Response to PM is regulated by Bcl-2 since it down-regulated Bcl-2 expression and overexpression of Bcl-2 rendered prostate cancer cells resistant to PM. ROS plays a role in down-regulation of Bcl-2, since treatment with PM in the presence of various ROS modulators, e.g., n-acetylcysteine (NAC), a general purpose antioxidant; diphenylene iodonium (DPI), a NADPH inhibitor; rotenone (ROT), a mitochondrial electron transport chain interrupter rotenone or MnTBAP, a O₂ scavenger, attenuated the down-regulation of Bcl-2. Furthermore, ROS is also involved in the ubiquitination and proteasomal degradation of Bcl-2 as both of these events were blocked by O ₂^- scavenger MnTBAP. Thus, pristimerin induces apoptosis in prostate cancer cells predominately through the mitochondrial apoptotic pathway by inhibiting antiapoptic Bcl-2 through a ROS-dependent ubiquitin-proteasomal degradation pathway.