Inhibition of cyclooxygenase-2-dependent survivin mediates decursin-induced apoptosis in human KBM-5 myeloid leukemia cells

Decursin Induces G1 Cell Cycle Arrest and Apoptosis through Reactive Oxygen Species-Mediated Endoplasmic Reticulum Stress in Human Colorectal Cancer Cells in In Vitro and Xenograft Models

Decursin, a coumarin isolated from Angelica gigas Nakai, possesses anti-inflammatory and anti-cancer properties. However, the molecular mechanisms underlying its anti-cancer effects against human colorectal cancer (CRC) are unclear. Therefore, this study aimed to evaluate the biological activities of decursin in CRC in vitro and in vivo and to determine its underlying mechanism of action. Decursin exhibited anti-tumor activity in vitro, accompanied by an increase in G1 cell cycle arrest and apoptosis in HCT-116 and HCT-8 CRC cells. Decursin also induced the production of reactive oxygen species (ROS), thereby activating the endoplasmic reticulum (ER) stress apoptotic pathway in CRC cells. Furthermore, the role of ROS in decursin-induced apoptosis was investigated using the antioxidant N-acetyl-L-cysteine. Inhibiting ROS production reversed decursin-induced ER stress. Moreover, decursin significantly suppressed tumor growth in a subcutaneous xenograft mouse model of HCT-116 and HCT-8 CRC cells without causing host toxicity. Decursin also decreased cell proliferation, as documented by Ki-67, and partly increased cleaved caspase 3 expression in tumor tissues by activating ER stress apoptotic pathways. These findings suggest that decursin induces cell cycle arrest and apoptosis in human CRC cells via ROS-mediated ER stress, suggesting that decursin could be a therapeutic agent for CRC.

A comprehensive review of the anticancer effects of decursin

Cancer is a globally complex disease with a plethora of genetic, physiological, metabolic, and environmental variations. With the increasing resistance to current anticancer drugs, efforts have been made to develop effective cancer treatments. Currently, natural products are considered promising cancer therapeutic agents due to their potent anticancer activity and low intrinsic toxicity. Decursin, a coumarin analog mainly derived from the roots of the medicinal plant Angelica sinensis, has a wide range of biological activities, including anti-inflammatory, antioxidant, neuroprotective, and especially anticancer activities. Existing studies indicate that decursin affects cell proliferation, apoptosis, autophagy, angiogenesis, and metastasis. It also indirectly affects the immune microenvironment and can act as a potential anticancer agent. Decursin can exert synergistic antitumor effects when used in combination with a number of common clinical anticancer drugs, enhancing chemotherapy sensitivity and reversing drug resistance in cancer cells, suggesting that decursin is a good drug combination. Second, decursin is also a promising lead compound, and compounds modifying its structure and formulation form also have good anticancer effects. In addition, decursin is not only a key ingredient in several natural herbs and dietary supplements but is also available through a biosynthetic pathway, with anticancer properties and a high degree of safety in cells, animals, and humans. Thus, it is evident that decursin is a promising natural compound, and its great potential for cancer prevention and treatment needs to be studied and explored in greater depth to support its move from the laboratory to the clinic.

A Natural Organic Compound "Decursin" Has Both Antitumor and Renal Protective Effects: Treatment for Osteosarcoma

Osteosarcoma is a rare malignant tumor that commonly occurs in children. Anticancer drugs, for example, cisplatin, aid in postsurgery recovery but induce side effects such as renal damage, affecting the life prognosis of patients. Decursin which is one of the bioactive components has been reported for its anti-inflammatory, antioxidant, and antitumor effects, but the effect on osteosarcoma is unexplained. In this study, the research theme was to examine the sensitizing effect of decursin and its influence on cisplatin-induced nephrotoxicity. The cell viability and half maximal inhibitory concentration (IC50), apoptosis induction, and effect on cell cycle and Akt pathways were examined. In vivo, we examine the effects of decursin on tumors and mice bodies. Additionally, the effects of the cisplatin-decursin combination were evaluated in vitro and in vivo. Decursin suppressed cell viability and induced apoptosis via the cell cycle. Decursin also inhibited the Akt pathway by suppressing the phosphorylation of Akt. It enhanced apoptosis induction and lowered cell viability in combination with cisplatin. The increasing tumor volume was suppressed in the decursin-administrated group with further suppression in combination with cisplatin compared to sole cisplatin administration. The decrease in renal function and renal epithelial cell damage caused by cisplatin was improved by the combinatorial treatment with decursin. Therefore, decursin demonstrated an antitumor effect on the osteosarcoma cells and a renal protective effect in combination with cisplatin. Therefore, decursin is a prospective therapeutic agent against osteosarcoma.

Novel bioactive hybrid Celecoxib-HDAC Inhibitor, induces apoptosis in human acute lymphoblastic leukemia cells

Acute lymphoblastic leukemia (ALL) is the most common malignancy in children. Here, we exploited the synergy between histone deacetylase inhibitors (HDACi) and cyclooxygenase 2 (COX-2) inhibitors by generating and testing a series of hybrid Celecoxib-HDAC inhibitors (selenium-containing analogues of Celecoxib) on ALL cells, of which compound 11 exhibited significant inducement to kill NALM6 cells with an average IC50 of 9.95 ± 0.44 μM compared with control Celecoxib at 28.58 ± 1.44 μM and inhibited NALM6 cells growth via the inhibition of the cell cycle in G2 phase. Furthermore, compound 11 induced apoptosis by activating PARP cleavage. Taken together, compound 11 possessed the potential to be developed further as a chemotherapeutic agent for ALL.

Farnesiferol C Induces Apoptosis in Chronic Myelogenous Leukemia Cells as an Imatinib Sensitizer via Caspase Activation and HDAC (Histone Deacetylase) Inactivation

Herein the underlying apoptotic mechanism of Farnesiferol C (FC) derived from Ferula assafoetida was elucidated in chronic myelogenous leukemia (CML) K562 and KBM5 cells. FC showed significant cytotoxicity in K562 and KBM5 cells, more so than in U937 and UL-60 acute myeloid leukemia (AML) cells. Cleaved PARP and caspase 9/3 attenuated the expression of Bcl2 and induced G1 arrest in K562 and KBM5 cells. Also, FC effectively abrogated the expression of cell cycle related proteins, such as: Cyclin D1, Cyclin E, Cyclin B1 in K562, and KBM5 cells, but caspase 3 inhibitor Z-DEVD-FMK rescued the cleavages of caspase 3 and PARP induced by FC in K562 cells. Of note, FC decreased histone deacetylase 1 (HDAC1) and HDAC2, and enhanced histone H3 acetylation K18 (Ac-H3K18) in K562 and KBM5 cells. Furthermore, combination of FC and Imatinib enhanced the apoptotic effect of Imatinib as a potent Imatinib sensitizer in K562 cells. Overall, our findings provide scientific evidence that inactivation of HDAC and caspase activation mediate FC induced apoptosis in CML cells.

Decursin induces apoptosis in glioblastoma cells, but not in glial cells via a mitochondria-related caspase pathway

Decursin is a major biological active component of Angelica gigas Nakai and is known to induce apoptosis of metastatic prostatic cancer cells. Recently, other reports have been commissioned to examine the anticancer activities of this plant. In this study, we evaluated the inhibitory activity and related mechanism of action of decursin against glioblastoma cell line. Decursin demonstrated cytotoxic effects on U87 and C6 glioma cells in a dose-dependent manner but not in primary glial cells. Additionally, decursin increased apoptotic bodies and phosphorylated JNK and p38 in U87 cells. Decursin also down-regulated Bcl-2 as well as cell cycle dependent proteins, CDK-4 and cyclin D1. Furthermore, decursin-induced apoptosis was dependent on the caspase activation in U87 cells. Taken together, our data provide the evidence that decursin induces apoptosis in glioblastoma cells, making it a potential candidate as a chemotherapeutic drug against brain tumor.

Far Infrared Irradiation Enhances Nutraceutical Compounds and Antioxidant Properties in Angelica gigas Nakai Powder

The aim of this study was to investigate the effect of far infrared irradiation (FIR) on nutraceutical compounds, viz. total phenolic content, total flavonoids, and antioxidant capacity, of Angelica gigas Nakai (AGN). The FIR treatment was applied for 30 min with varied temperatures of 120, 140, 160, 180, 200, 220, and 240 °C. Results showed that FIR increased total phenolic and flavonoid content in AGN at 220 °C. The HPLC results revealed higher quantities of decursin (62.48 mg/g) and decursinol angelate (41.51 mg/g) at 220 °C compared to control (38.70 mg/g, 27.54 mg/g, respectively). The antioxidant capacity of AGN was also increased at 220 °C, as measured by 1,1-diphenyl-2-picrylhydrazyl (DPPH), ferric reducing antioxidant power (FRAP), and the phosphomolybdenum (PPMD) method. A further increase of the FIR temperature caused a reduction of compound content. In addition, the results also showed a strong correlation between phenolic content and antioxidant properties of AGN powder. These findings will help to further improve the nutraceutical profile of AGN powder by optimizing the FIR conditions.

Natural Korean Medicine Dang-Gui: Biosynthesis, Effective Extraction and Formulations of Major Active Pyranocoumarins, Their Molecular Action Mechanism in Cancer, and Other Biological Activities

Angelica gigas Nakai (AGN) is a crucial oriental medicinal herb that grows especially in Korea and the Far-East countries. It contains chemically active compounds like pyranocoumarins, polyacetylenes and essential oils, which might be useful for treatment of several chronic diseases. It has been used for centuries as a traditional medicine in Southeast Asia, but in Western countries is used as a functional food and a major ingredient of several herbal products. The genus Angelica is also known as ‘female ginseng’ due to its critical therapeutic role in female afflictions, such as gynecological problems. However, it is well-documented that the AGN pyranocoumarins may play vital beneficial roles against cancer, neurodisorders, inflammation, osteoporosis, amnesia, allergies, depression, fungi, diabetes, ischemia, dermatitis, reactive oxygen species (ROS) and androgen. Though numerous studies revealed the role of AGN pyranocoumarins as therapeutic agents, none of the reviews have published their molecular mechanism of action. To the best of our knowledge, this would be the first review that aims to appraise the biosynthesis of AGN’s major active pyranocoumarins, discuss effective extraction and formulation methods, and detail the molecular action mechanism of decursin (D), decursinol angelate (DA) and decursinol (DOH) in chronic diseases, which would further help extension of research in this area.

Decursin and decursinol angelate: molecular mechanism and therapeutic potential in inflammatory diseases

Epidemiological studies have shown that inflammation plays a critical role in the development and progression of various chronic diseases, including cancers, neurological diseases, hepatic fibrosis, diabetic retinopathy, and vascular diseases. Decursin and decursinol angelate (DA) are pyranocoumarin compounds obtained from the roots of Angelica gigas. Several studies have described the anti-inflammatory effects of decursin and DA. Decursin and DA have shown potential anti-inflammatory activity by modulating growth factors such as vascular endothelial growth factor, transcription factors such as signal transducer and activator of transcription 3 and nuclear factor kappa-light-chain-enhancer of activated B cells, cellular enzymes including matrix metalloproteinases cyclooxygenase, and protein kinases such as extracellular receptor kinase, phosphatidylinositol-3-kinase, and protein kinase C. These compounds have the ability to induce apoptosis by activating pro-apoptotic proteins and the caspase cascade, and reduced the expression of anti-apoptotic proteins such as B-cell lymphoma 2 and B-cell lymphoma-extra-large. Interaction with multiple molecular targets and cytotoxic effects, these two compounds are favorable candidates for treating various chronic inflammatory diseases such as cancers (prostate, breast, leukemia, cervical, and myeloma), rheumatoid arthritis, diabetic retinopathy, hepatic fibrosis, osteoclastogenesis, allergy, and Alzheimer's disease. We have summarized the preliminary studies regarding the biological effects of decursin and DA. In this review, we will also highlight the functions of coumarin compounds that can be translated to a clinical practice for the treatment and prevention of various inflammatory ailments.

PUMA and survivin are involved in the apoptosis of HepG2 cells induced by microcystin-LR via mitochondria-mediated pathway

The present study aimed to determine the cytotoxicity of microcystin-LR (MC-LR) on the human hepatocellular carcinoma (HepG2) cells in order to elucidate the mechanism of apoptosis induced by MC-LR. Morphological evaluation results showed that MC-LR induced time- and concentration-dependent apoptosis in HepG2 cells. The biochemical assays revealed that MC-LR-exposure caused overproduction of reactive oxygen species (ROS), cyclooxygenase-2 activity alteration, cytochrome c release, and remarkable activation of caspase-3 and caspase-9 in HepG2 cells, indicating that MC-LR-induced apoptosis is mediated by mitochondrial pathway. Moreover, we also found that p53 and Bax might play an important role in MC-LR-induced apoptosis in HepG2 cells in which PUMA and survivin were involved. However, further studies are necessary to elucidate the possible functions of PUMA and survivin in MC-LR-induced apoptosis in HepG2 cells.

The influence of Cox-2 and bioactive lipids on hematological cancers

Inflammation is implicated in the progression of multiple types of cancers including lung, colorectal, breast and hematological malignancies. Cyclooxygenases (Cox) -1 and -2 are important enzymes involved in the regulation of inflammation. Elevated Cox-2 expression is associated with a poor cancer prognosis. Hematological malignancies, which are among the top 10 most predominant cancers in the USA, express high levels of Cox-2. Current therapeutic approaches against hematological malignances are insufficient as many patients develop resistance or relapse. Therefore, targeting Cox-2 holds promise as a therapeutic approach to treat hematological malignancies. NSAIDs and Cox-2 selective inhibitors are anti-inflammatory drugs that decrease prostaglandin and thromboxane production while promoting the synthesis of specialized proresolving mediators. Here, we review the evidence regarding the applicability of NSAIDs, such as aspirin, as well as Cox-2 specific inhibitors, to treat hematological malignancies. Furthermore, we discuss how FDA-approved Cox inhibitors can be used as anti-cancer drugs alone or in combination with existing chemotherapeutic treatments.

Tanshinone IIA induces autophagic cell death via activation of AMPK and ERK and inhibition of mTOR and p70 S6K in KBM-5 leukemia cells

Although tanshinone IIA (Tan IIA) from Salviae miltiorrhizae was known to induce apoptosis in various cancers, its underlying mechanism of autophagic cell death was not reported yet. Thus, in the present study, the molecular mechanism of autophagic cell death by Tan IIA was investigated in KBM-5 leukemia cells. Tan IIA significantly increased the expression of microtubule-associated protein light chain 3 (LC3) II as a hallmark of autophagy in western blotting and immunofluorescence staining. Tan IIA augmented the phosphorylation of adenosine monophosphate-activated protein kinase (AMPK) and attenuated the phosphorylation of mammalian target of rapamycin (mTOR) and p70 S6K in a dose-dependent manner. Conversely, autophagy inhibitor 3-methyladenine partly reversed the cytotoxicity and the phosphorylation of AMPK, mTOR and p70 S6K induced by Tan IIA in KBM-5 leukemia cells. In addition, Tan IIA dramatically activated the extracellular signal regulated kinase (ERK) signaling pathway including Raf, ERK and p90 RSK in a dose-dependent and time-dependent manner. Consistently, ERK inhibitor PD184352 suppressed LC3-II activation induced by Tan IIA, whereas PD184352 and PD98059 did not affect poly (ADP-ribose) polymerase cleavage and sub-G1 accumulation induced by Tan IIA in KBM-5 leukemia cells. Furthermore, Tan IIA could induce autophagy via LC3-II activation in various cancer cells such as prostate (PC-3), multiple myeloma (U266), lung (NCI-H460), and breast (MDA-MB-231) cells. Overall, these findings suggest that Tan IIA induces autophagic cell death via activation of AMPK and ERK and inhibition of mTOR and p70 S6K in KBM-5 cells as a potent natural compound for leukemia treatment.

Decursin and Doxorubicin Are in Synergy for the Induction of Apoptosis via STAT3 and/or mTOR Pathways in Human Multiple Myeloma Cells

Background. Combination cancer therapy is one of the attractive approaches to overcome drug resistance of cancer cells. In the present study, we investigated the synergistic effect of decursin from Angelica gigas and doxorubicin on the induction of apoptosis in three human multiple myeloma cells. Methodology/Principal Findings. Combined treatment of decursin and doxorubicin significantly exerted significant cytotoxicity compared to doxorubicin or decursin in U266, RPMI8226, and MM.1S cells. Furthermore, the combination treatment enhanced the activation of caspase-9 and -3, the cleavage of PARP, and the sub G1 population compared to either drug alone in three multiple myeloma cells. In addition, the combined treatment downregulated the phosphorylation of mTOR and its downstream S6K1 and activated the phosphorylation of ERK in three multiple myeloma cells. Furthermore, the combined treatment reduced mitochondrial membrane potential, suppressed the phosphorylation of JAK2, STAT3, and Src, activated SHP-2, and attenuated the expression of cyclind-D1 and survivin in U266 cells. Conversely, tyrosine phosphatase inhibitor pervanadate reversed STAT3 inactivation and also PARP cleavage and caspase-3 activation induced by combined treatment of doxorubicin and decursin in U266 cells. Conclusions/Significance. Overall, the combination treatment of decursin and doxorubicin can enhance apoptotic activity via mTOR and/or STAT3 signaling pathway in multiple myeloma cells.

Decursin exerts anti-cancer activity in MDA-MB-231 breast cancer cells via inhibition of the Pin1 activity and enhancement of the Pin1/p53 association

The peptidyl-prolyl cis/trans isomerase Pin1 is overexpressed in a wide variety of cancer cells and thus considered as an important target molecule for cancer therapy. This study demonstrates that decursin, a bioactive compound from Angelica gigas, exert the anti-cancer effect against breast cancer cells via regulation of Pin1 and its related signaling molecules. We observed that decursin induced G1 arrest with decrease in cyclin D1 level in Pin1-expressing breast cancer cells MDA-MB-231, but not Pin1-non-expressing breast cancer cells MDA-MB-157. In addition, decursin significantly reduced protein expression and enzymatic activity of Pin1 in MDA-MB-231 cells. Further, we found that decursin treatment enhanced the p53 expression level and failed to down-regulate Pin1 in the cells transfected with p53 siRNA, indicating the importance of p53 in the decursin-mediated Pin1 inhibition in MDA-MB-231 cells. Decursin stimulated association between Pin1 to p53. Moreover, decursin facilitated p53 transcription in MDA-MB-231 cells. Overall, our current study suggests the potential of decursin as an attractive cancer therapeutic agent for breast cancer by targeting Pin1 protein.

Emerging targets in lipid-based therapy

The use of prostaglandins and NSAIDS in the clinic has proven that lipid mediators and their associated pathways make attractive therapeutic targets. When contemplating therapies involving lipid pathways, several basic agents come to mind. There are the enzymes and accessory proteins that lead to the metabolism of lipid substrates, provided through diet or through actions of lipases, the subsequent lipid products, and finally the lipid sensors or receptors. There is abundant evidence that molecules along this lipid continuum can serve as prognostic and diagnostic indicators and are in fact viable therapeutic targets. Furthermore, lipids themselves can be used as therapeutics. Despite this, the vernacular dialog pertaining to "biomarkers" does not routinely include mention of lipids, though this is rapidly changing. Collectively these agents are becoming more appreciated for their respective roles in diverse disease processes from cancer to preterm labor and are receiving their due appreciation after decades of ground work in the lipid field. By relating examples of disease processes that result from dysfunction along the lipid continuum, as well as examples of lipid therapies and emerging technologies, this review is meant to inspire further reading and discovery.

Decursin inhibits UVB-induced MMP expression in human dermal fibroblasts via regulation of nuclear factor-κB

Decursin, a coumarin compound, was originally isolated from the roots of Angelica gigas almost four decades ago, and it was found to exhibit cytotoxicity against various types of human cancer cells and anti-amnesic activity in vivo through the inhibition of AChE activity. However, the anti-skin photoaging effects of decursin have not been reported to date. In the present study, we investigated the inhibitory effects of decursin on the expression of matrix metalloproteinase (MMP)-1 and MMP-3 in human dermal fibroblast (HDF) cells. Western blot analysis and real-time PCR revealed that decursin inhibited the ultraviolet (UV)B-induced expression of MMP-1 and MMP-3 in a dose-dependent manner. Decursin significantly blocked the UVB-induced activation of nuclear factor-κB (NF-κB). However, decursin showed no effect on MAPK or AP-1 activity. In this study, decursin prevented the UVB-induced expression of MMPs via the inhibition of NF-κB activation. In conclusion, decursin may be a potential agent for the prevention and treatment of skin photoaging.

Melatonin synergistically enhances cisplatin-induced apoptosis via the dephosphorylation of ERK/p90 ribosomal S6 kinase/heat shock protein 27 in SK-OV-3 cells

To evaluate melatonin's ability to enhance ovarian cancer cells to cisplatin treatment for ovarian cancer, this study was performed. Melatonin by itself had no significant cytotoxicity against SK-OV-3 cells, while cisplatin suppressed the cell viability in a dose-dependent manner. Combined treatment with cisplatin and melatonin synergistically inhibited the viability of SK-OV-3 cells with the synergism between two drugs (1 > combination index). In contrast, melatonin revealed the protective effect against cisplatin-induced cytotoxicity in OSEN normal ovarian epithelial cells. Cotreatment with cisplatin and melatonin increased the sub-G1 DNA contents and TdT-mediated dUTP nick end-labeling (TUNEL)-positive cells compared with cisplatin control in SK-OV-3 cells, suggesting that melatonin augments cisplatin-induced apoptosis. Consistently, combined treatment of cisplatin and melatonin increased the cleavage of caspase-3 and poly-(ADP-ribose) polymerase (PARP). Importantly, melatonin synergistically inhibited the phosphorylation of extracellular signal-regulated kinase (ERK) along with dephosphorylation of 90-kDa ribosomal S6 kinase (p90RSK) and heat shock protein 27 (HSP27) induced by cisplatin. Furthermore, melatonin remarkably blocked the expression and colocalization of p90RSK and HSP27 by combination treatment with cisplatin. Taken together, our findings demonstrate that melatonin enhances cisplatin-induced apoptosis via the inactivation of ERK/p90RSK/HSP27 cascade in SK-OV-3 cells as a potent synergist to cisplatin treatment.

Jolkinolide B from Euphorbia fischeriana Steud induces apoptosis in human leukemic U937 cells through PI3K/Akt and XIAP pathways

Jolkinolide B, a bioactive diterpene isolated from the roots of Euphorbia fischeriana Steud, is known to induce apoptosis in cancer cells. However, the molecular mechanism of its anti-cancer activity has not been fully elucidated. In the present study, we found that Jolkinolide B reduced cell viability and induced apoptosis in a dose- and time-dependent manner in human leukemic U937. The induction of apoptosis was also accompanied by the downregulation of PI3K/Akt and the inhibitor of apoptosis protein (IAP) family proteins. Moreover, we observed that Jolkinolide B treatment resulted in activation of caspase-3 and -9, which may partly explain the anti-cancer activity of Jolkinolide B. Taken together, our study for the first time suggest that Jolkinolide B is able to enhance apoptosis of U937 cells, at least in part, through downregulation of PI3K/Akt and IAP family proteins. Moreover, triggering of caspase-3 and -9 activation mediated apoptotic induction.

Rhapontigenin inhibited hypoxia inducible factor 1 alpha accumulation and angiogenesis in hypoxic PC-3 prostate cancer cells

Hypoxia inducible factor 1 alpha (HIF-1α) is frequently over-expressed in the numerous types of cancer and plays an important role in angiogenesis. In the present study, the inhibitory mechanism of rhapontigenin isolated from Vitis coignetiae was investigated on HIF-1α stability and angiogenesis in human prostate cancer PC-3 cells. Rhapontigenin significantly suppressed HIF-1α accumulation at protein level but not at mRNA level in PC-3 cells under hypoxia. Also, rhapontigenin suppressed hypoxia-induced HIF-1α activation in various cancer cells, such as colorectal adenocarcinoma (SW620), breast adenocarcinoma (MCF-7), fibrosarcoma (HT-1080) and prostate carcinoma (LNCaP). Interestingly, rhapontigenin had more potency in inhibition of hypoxia-induced HIF-1α expression than that of resveratrol, a known HIF-1α inhibitor. In addition, rhapontigenin promoted hypoxia-induced HIF-1α degradation and cycloheximide (CHX) blocked protein synthesis. A prolyl hydroxylase (PHD) inhibitor dimethyloxalylglycine (DMOG) is usually utilized to examine whether prolyl hydroxylation is involved in inhibition of HIF-1α accumulation. Here, DMOG recovered HIF-1α accumulation inhibited by rhapontigenin. Immunoprecipitation assay also revealed that rhapotigenin enhanced the binding of hydroxylated HIF-1α to von Hippel-Lindau (VHL) tumor suppressor protein. Furthermore, rhapontigenin reduced vascular endothelial growth factor (VEGF) secretion in hypoxic PC-3 cells as well as suppressed tube formation in human umbilical vein endothelial cells (HUVECs) treated by the conditioned media of hypoxic PC-3 cells. However, anti-angiogenic effect of rhapontigenin in hypoxic PC-3 cells was reversed by DMOG. Taken together, these findings suggest that rhapontigenin inhibits HIF-1α accumulation and angiogenesis in PC-3 prostate cancer cells.

Sphingosine kinase 1 pathway is involved in melatonin-induced HIF-1α inactivation in hypoxic PC-3 prostate cancer cells

Sphingosine kinase 1 (SPHK1) is a newly discovered modulator of hypoxia inducible factor 1α (HIF-1α) with various biological activities such as cell growth, survival, invasion, angiogenesis, and carcinogenesis. Thus, in the present study, the biological mechanisms of melatonin were elucidated in association with SPHK1 pathway in PC-3 prostate cancer cells under hypoxia. Melatonin inhibited the stability of HIF-1α in a time- and concentration- dependent manners. Also, melatonin decreased SPHK1 activity in PC-3 cells during hypoxia. Furthermore, melatonin suppressed AKT/glycogen synthase kinase-3β (GSK-3β) signaling pathway, which stabilizes HIF-1α via inhibition of von Hippel-Lindau tumor suppressor protein. Consistently, siRNA-SPHK1 and sphingosine kinase inhibitor (SKI) effectively blocked the expression of HIF-1α, phospho-AKT and vascular endothelial growth factor (VEGF) production in PC-3 cells under hypoxia, suggesting the role of SPHK1 in melatonin-inhibited HIF-1α accumulation. Moreover, reactive oxygen species (ROS) scavenger N-acteylcysteine enhanced melatonin-inhibited HIF-1α expression and SPHK1 activity. Overall, our findings suggest that melatonin suppresses HIF-1α accumulation via inhibition of SPHK1 pathway and ROS generation in PC-3 cells under hypoxia.

Melatonin promotes puromycin-induced apoptosis with activation of caspase-3 and 5'-adenosine monophosphate-activated kinase-alpha in human leukemia HL-60 cells

Melatonin, a naturally occurring molecule, is produced by the pineal gland in a circadian manner to regulate biologic rhythms in humans. Recent studies report that melatonin may be an attractive candidate as an anticancer agent or for combined therapy because of its antioxidant, oncostatic and immunoregulatory activities. In this study, the potentiating effect of melatonin was evaluated on the apoptosis induced by puromycin as an anticancer drug in acute promyelocytic leukemia HL-60 cells. Melatonin did not show significant cytotoxicity against HL-60 cells compared to puromycin. However, melatonin significantly augmented the cytotoxicity of puromycin. Consistently, combined treatment of melatonin and puromycin reduced the expression of anti-apoptotic proteins, such as bcl-2 and bcl-x(L) , and also induced caspase-3 activation and poly (ADP-ribose) polymerase (PARP) cleavage compared to puromycin treatment alone. Furthermore, cell cycle analysis revealed that melatonin promoted puromycin-induced apoptosis by increasing the sub-G1 population, but suppressing G2/M arrest in HL-60 cells. Interestingly, melatonin activated the phosphorylation of 5'-adenosine monophosphate-activated kinase (AMPK) in combination with puromycin. Taken together, our results suggest that melatonin potentiates puromycin-induced apoptosis with caspase-3 and AMPK activation in HL-60 cells, and thus, melatonin treatment can be effectively applied to leukemia treatment as a potential sensitizer for chemotherapeutic agents.

Celecoxib inhibits STAT3 phosphorylation and suppresses cell migration and colony forming ability in rhabdomyosarcoma cells

Rhabdomyosarcoma (RMS) is the most common soft tissue sarcoma in the pediatric and adolescent population. Though treatments for localized disease have reasonable long-term success rates, if disease is diffuse at diagnosis, outcomes are far poorer. Additional and/or alternative therapies are critical for improved clinical outcomes. One potentially therapeutic target is the signal transducer and activator of transcription 3 (STAT3) pathway. STAT3 has been shown to have constitutive activation in human rhabdomyosarcoma cells; thus, inhibition of STAT3 signaling may be a mechanism to induce tumor cell death. Celecoxib has been shown, by computer modeling, to bind STAT3 at the SH2 domain and competitively inhibit native peptide binding necessary for phosphorylation and subsequent propagation of the STAT3 signaling cascade. We found that celecoxib inhibits IL-6-induced and persistent STAT3 phosphorylation and inhibits cell viability in human rhabdomyosarcoma cells. We found that genes downstream of STAT3 (BCL-2, survivin, cyclin D1) were downregulated with celecoxib. Celecoxib also inhibits colony formation and cell migration. Our results suggest that, though known more commonly as a cyclooxygenase-2 (COX-2) inhibitor, celecoxib could act through the STAT3 pathway as well. More importantly, its effect on cell migration and clonogenic colony forming ability make it a potentially useful therapeutic agent for rhabdomyosarcoma, especially in metastatic disease whose clinical outcome is marginal at best with current therapies.