Po-Lin Kuo

Phthalates induce proliferation and invasiveness of estrogen receptor-negative breast cancer through the AhR/HDAC6/c-Myc signaling pathway

The environmentally present group of chemical phthalates, or phthalate esters, has been recognized as a rising threat to public health, including cancer. While most studies have addressed the estrogenic effects of phthalates in malignancies of the breast and the prostate, little is known about their role in the etiology of hormone‐independent cancer. Here we show that treatments with the phthalates n‐butyl benzyl phthalate (BBP) and dibutyl phthalate (DBP) at 1 μM induced proliferation (BBP, 3.2‐fold; DBP, 3.2‐fold), migration (BBP, 2.6‐fold; DBP, 2.6‐fold), invasion (BBP, 2.7‐fold; DBP, 3.1‐fold), and tumor formation (EC50: BBP, 0.12 μM; DBP, 0.22 μM) in estrogen receptor (ER)‐negative breast cancer cells (MDA‐MB‐231). We further demonstrate that phthalates stimulated the cell surface aryl hydrocarbon receptor (AhR) and triggered the downstream cyclic AMP (cAMP)‐PKA‐CREB1 signaling cascade. The pathway led to increased expression of HDAC6, which facilitated nuclear assembly of the β‐catenin‐LEF1/TCF4 transcriptional complex and transactivation of the c‐Myc oncogene. This nongenomic pathway emanated from the phthalateinduced AhR promoted tumorigenesis of ER‐negative breast cancer. Collectively, our findings revealed a novel oncogenic mechanism of phthalates in breast cancer independent from their estrogenic activities.—Hsieh, T.‐H., Tsai, C.‐F., Hsu, C.‐Y., Kuo, P.‐L., Lee, J.‐N., Chai, C.‐Y., Wang, S.‐C., Tsai, E.‐M. Phthalates induce proliferation and invasiveness of estrogen receptor‐negative breast cancer through the AhR/HDAC6/c‐Myc signaling pathway. FASEB J. 26, 778–787 (2012). www.fasebj.org

Isoobtusilactone A Induces Cell Cycle Arrest and Apoptosis through Reactive Oxygen Species/Apoptosis Signal-Regulating Kinase 1 Signaling Pathway in Human Breast Cancer Cells

This study is the first to investigate the anticancer effect of isoobtusilactone A (IOA) in two human breast cancer cell lines, MCF-7 and MDA-MB-231. IOA exhibited effective cell growth inhibition by inducing cancer cells to undergo G(2)-M phase arrest and apoptosis. Further investigation revealed that IOAs inhibition of cell growth was also evident in a nude mice model. Cell cycle blockade was associated with increased levels of p21 and reduced amounts of cyclin B1, cyclin A, cdc2, and cdc25C. IOA also enhanced the levels of inactivated phosphorylated cdc2 and cdc25C. IOA triggered the mitochondrial apoptotic pathway, as indicated by a change in Bax/Bcl-2 ratios, resulting in mitochondrial membrane potential loss, cytochrome c release, and caspase-9 activation. We also found that the generation of reactive oxygen species (ROS) is a critical mediator in IOA-induced cell growth inhibition. Enhancement of ROS by IOA activated apoptosis signal-regulating kinase 1 (ASK1) resulted in the increased activation of c-Jun NH(2)-terminal kinase and p38. Antioxidants EUK8 and N-acetyl cystenine significantly decreased apoptosis by inhibiting the ASK1 dephosphorylation at Ser(967) and subsequently increased the interaction of ASK1 with thioredoxin or 14-3-3 proteins. Moreover, blocking ASK1 by small interfering RNA inhibition completely suppressed IOA-induced apoptosis. Taken together, these results imply a critical role for ROS and ASK1 in IOAs anticancer activity.

Arctigenin, a dietary phytoestrogen, induces apoptosis of estrogen receptor-negative breast cancer cells through the ROS/p38 MAPK pathway and epigenetic regulation

This study investigates the anticancer effect of arctigenin (ATG), a natural lignan product of Arctium lappa L., in human breast cancer MDA-MB-231 cells. Results indicate that ATG inhibits MDA-MB-231 cell growth by inducing apoptosis in vitro and in vivo. ATG triggers the mitochondrial caspase-independent pathways, as indicated by changes in Bax/Bcl-2 ratio, resulting in AIF and EndoG nuclear translocation. ATG increased cellular reactive oxygen species (ROS) production by increasing p22(phox)/NADPH oxidase 1 interaction and decreasing glutathione level. ATG clearly increases the activation of p38 MAPK, but not JNK and ERK1/2. Antioxidant EUK-8, a synthetic catalytic superoxide and hydrogen peroxide scavenger, significantly decreases ATG-mediated p38 activation and apoptosis. Blocking p38 with a specific inhibitor suppresses ATG-mediated Bcl-2 downregulation and apoptosis. Moreover, ATG activates ATF-2, a transcription factor activated by p38, and then upregulates histone H3K9 trimethylation in the Bcl-2 gene promoter region, resulting in Bcl-2 downregulation. Taken together, the results demonstrate that ATG induces apoptosis of MDA-MB-231 cells via the ROS/p38 MAPK pathway and epigenetic regulation of Bcl-2 by upregulation of histone H3K9 trimethylation.

Lung Cancer-Derived Galectin-1 Mediates Dendritic Cell Anergy through Inhibitor of DNA Binding 3/IL-10 Signaling Pathway

Lung cancer, one of the leading causes of death worldwide, is often associated with a state of immune suppression, but the molecular and functional basis remains enigmatic. Evidence is provided in this paper supporting the role of lung cancer-derived soluble lectin, galectin-1, as a culprit in dendritic cell (DC) anergy. We have shown that galectin-1 is highly expressed in lung cancer cell lines, together with the serum and surgical samples from lung cancer patients. Functionally, lung cancer-derived galectin-1 has been shown to alter the phenotypes of monocyte-derived DCs (MdDCs) and impair alloreactive T cell response, concomitant with the increase of CD4+CD25+FOXP3+ regulatory T cells. The regulatory effect of galectin-1 is mediated, in part, through its ability to induce, in an Id3 (inhibitor of DNA binding 3)-dependent manner, the expression of IL-10 in monocytes and MdDCs. This effect is inhibited by the addition of lactose, which normalizes the phenotypic and functional alterations seen in MdDCs. Of note, significant upregulation of IL-10 was seen in tumor-infiltrating CD11c+ DCs in human lung cancer samples. This was also noted in mice transplanted with lung cancer cells, but not in those receiving tumor cells with galectin-1 knockdown. Furthermore, a significant reduction was noted in lung cancer incidence and in the levels of IL-10–expressing, tumor-infiltrating DCs, in mice receiving galectin-1–silenced tumor cells. These results thus suggest that the galectin-1/IL-10 functional axis may be crucial in lung cancer-mediated immune suppression, and that galectin-1 may serve as a target in the development of lung cancer immunotherapy.

Breast tumor-associated osteoblast-derived CXCL5 increases cancer progression by ERK/MSK1/Elk-1/snail signaling pathway.

The skeleton is the most common metastatic site for breast cancer, with bone metastasis causing pain as well as risk of pathological fractures. Interaction between tumors and the bone microenvironment creates a vicious cycle that accelerates both bone destruction and cancer progression. This study is the first to analyze the soluble factors secreted by breast tumor-associated osteoblasts (TAOBs), which are responsible for promoting cancer progression. The addition of CXCL5 (chemokine (C-X-C motif) ligand 5), present in large amounts in TAOB-condition medium (TAOB-CM), mimicked the inductive effect of TAOB-CM on breast cancer epithelial–mesenchymal transition, migration and invasion. In contrast, inhibition of CXCL5 in OBs decreased TAOB-mediated cancer progression. Inducement of MCF-7 and MDA-MB-231 cancer progression by TAOB-derived CXCL5 is associated with increased Raf/MEK/ERK activation, and mitogen- and stress-activated protein kinase 1 (MSK1) and Elk-1 phosphorylation, as well as Snail upregulation. Activation of Elk-1 facilitates recruitment of phosphorylated MSK1, which in turn enhances histone H3 acetylation and phosphorylation (serine 10) of Snail promoter, resulting in Snail enhancement and E-cadherin downregulation. Moreover, mice treated with anti-CXCL5 antibodies showed decreased metastasis of 4T1 breast cancer cells. Our study suggests that inhibition of CXCL5-mediated ERK/Snail signaling is an attractive therapeutic target for treating metastases in breast cancer patients.

MicroRNA-33a functions as a bone metastasis suppressor in lung cancer by targeting parathyroid hormone related protein

BACKGROUND Bone is a common site of metastasis for lung cancer, and is associated with significant morbidity and a dismal prognosis. MicroRNAs (miRNAs) are increasingly implicated in regulating the progression of malignancies. METHODS The efficacy of miR-33a or anti-miR-33a plasmid was assessed by Real-time PCR. Luciferase assays were using One-Glo Luciferase Assay System. Measurement of secreted factors was determined by ELISA kit. RESULTS We have found that miR-33a, which is downregulated in lung cancer cells, directly targets PTHrP (parathyroid hormone-related protein), a potent stimulator of osteoclastic bone resorption, leading to decreased osteolytic bone metastasis. We also found that miR-33a levels are inversely correlated with PTHrP expression between human normal bronchial cell line and lung cancer cell lines. The reintroduction of miR-33a reduces the stimulatory effect of A549 on the production of osteoclastogenesis activator RANKL (receptor activator of nuclear factor kappa-B ligand) and M-CSF (macrophage colony-stimulating factor) on osteoblasts, while the expression of PTHrP is decreased in A549 cells. miR-33a overexpression also reduces the inhibitory activity of A549 on the production of OPG (osteoprotegerin), an osteoclastogenesis inhibitor. In addition, miR-33a-mediated PTHrP downregulation results in decreased IL-8 secretion in A549, which contributes to decreased lung cancer-mediated osteoclast differentiation and bone resorption. CONCLUSIONS These findings have led us to conclude that miR-33a may be a potent tumor suppressor, which inhibits direct and indirect osteoclastogenesis through repression of PTHrP. GENERAL SIGNIFICANCE miR-33a may even predict a poor prognosis for lung cancer patients.

Lung Tumor-associated Osteoblast-derived Bone Morphogenetic Protein-2 Increased Epithelial-to-Mesenchymal Transition of Cancer by Runx2/Snail Signaling Pathway

Bone is a frequent target of lung cancer metastasis and is associated with significant morbidity and a dismal prognosis. Interaction between cancer cells and the bone microenvironment causes a vicious cycle of tumor progression and bone destruction. This study analyzed the soluble factors secreted by lung tumor-associated osteoblast (TAOB), which are responsible for increasing cancer progression. The addition of bone morphogenetic protein-2 (BMP-2), present in large amounts in TAOB conditioned medium (TAOB-CM) and lung cancer patient sera, mimicked the inductive effect of TAOB-CM on lung cancer migration, invasion, and epithelial-to-mesenchymal transition. In contrast, inhibition of BMP by noggin decreases the inductive properties of TAOB-CM and lung cancer patient sera on cancer progression. Induction of lung cancer migration by BMP-2 is associated with increased ERK and p38 activation and the up-regulation of Runx2 and Snail. Blocking ERK and p38 by a specific inhibitor significantly decreases cancer cell migration by inhibiting Runx2 up-regulation and subsequently attenuating the expression of Snail. Enhancement of Runx2 facilitates Rux2 to recruit p300, which in turn enhances histone acetylation, increases Snail expression, and decreases E-cadherin. Furthermore, inhibiting Runx2 by siRNA also suppresses BMP-2-induced Snail up-regulation and cell migration. Our findings provide novel evidence that inhibition of BMP-2 or BMP-2-mediated MAPK/Runx2/Snail signaling is an attractive therapeutic target for osteolytic bone metastases in lung cancer patients.

Oxidative and endoplasmic reticulum stress signaling are involved in dehydrocostuslactone-mediated apoptosis in human non-small cell lung cancer cells

This study investigates the anticancer effect of dehydrocostuslactone (DHE), a medicinal plant-derived sesquiterpene lactone, on human non-small cell lung cancer cell lines, A549, NCI-H460 and NCI-H520. Our results show that DHE inhibits the proliferation of A549, NCI-H460 and NCI-H520 cells. DHE-induced apoptosis in both A549 and NCI-H460 cells. DHE triggered endoplasmic reticulum (ER) stress, as indicated by changes in cytosol-calcium levels, PKR-like ER kinase (PERK) phosphorylation, inositol requiring protein 1 (IRE1) and CHOP/GADD153 upregulation, X-box transcription factor-1 (XBP-1) mRNA splicing, and caspase-4 activation. The release of calcium triggered the production of ROS, which further enhances calcium overloading and subsequently activates p38, JNK and ERK1/2. Both IRE1 miRNA transfection and BAPTA-AM pretreatment inhibit DHE-mediated apoptosis, supporting the hypothesis that DHE induces cell death through ER stress. Importantly, a novel anticancer agent for the treatment of non-small cell lung cancer, and is supported by animal studies which have shown a dramatic 50% reduction in tumor size after 28 days of treatment. This study demonstrates that DHE may be a novel anticancer agent for the treatment of non-small cell lung cancer.

CXCL1/GROα increases cell migration and invasion of prostate cancer by decreasing fibulin-1 expression through NF-κB/HDAC1 epigenetic regulation

Inflammatory tumor microenvironments play pivotal roles in the development of cancer. Inflammatory cytokines such as CXCL1/GROα exert cancer-promoting activities by increasing tumor angiogenesis. However, whether CXCL1/GROα also plays a role in the progression of prostate cancer, particularly in highly invasive castration-resistant prostate cancer (CRPC), has not been investigated. We explored whether CXCL1/GROα enhances cell migration and invasion in PC-3 and DU145 CRPC. Induction of PC-3 and DU145 cancer progression by CXCL1/GROα is associated with increased AKT activation and IκB kinase α (IKKα) phosphorylation, resulting in nuclear factor-kappaB (NF-κB) activation. Activated NF-κB interacts with histone deacetylase 1 (HDAC1) to form a gene-silencing complex, which represses the expression of fibulin-1D by decreasing the acetylation of histone H3 and H4 on the NF-κB-binding site of the fibulin-1D promoter. Blockade of AKT2 by small hairpin RNA (shRNA) decreases IKKα phosphorylation, NF-κB nuclear translocation and cell migration, indicating that AKT is required in CXCL1/GROα-mediated NF-κB activation and cell migration. In addition, NF-κB and HDAC1 shRNA decrease the effect of CXCL1/GROα on fibulin-1D downregulation, migration and invasion, suggesting that the NF-κB/HDAC1 complex is also involved in CXCL1/GROα-mediated cancer progression. Our findings provide the first evidence that CXCL1/GROα decreases fibulin-1D expression in prostate cancer cells and also reveals novel insights into the mechanism by which CXCL1/GROα regulates NF-κB activation through the AKT pathway. Our results also clearly establish that co-operation of NF-κB and HDAC1 regulates fibulin-1D expression by epigenetic modification. Our study suggests that inhibition of CXCL1/GROα-mediated AKT/NF-κB signaling may be an attractive therapeutic target for CRPC.

Hypoxic lung cancer-secreted exosomal miR-23a increased angiogenesis and vascular permeability by targeting prolyl hydroxylase and tight junction protein ZO-1

Hypoxia plays a critical role during the evolution of malignant cells and tumour microenvironment (TME).Tumour-derived exosomes contain informative microRNAs involved in the interaction of cancer and stromal cells, thus contributing to tissue remodelling of tumour microenvironment. This study aims to clarify how hypoxia affects tumour angiogenesis through exosomes shed from lung cancer cells. Lung cancer cells produce more exosomes under hypoxic conditions than do parental cells under normoxic conditions. miR-23a was significantly upregulated in exosomes from lung cancer under hypoxic conditions. Exosomal miR-23a directly suppressed its target prolyl hydroxylase 1 and 2 (PHD1 and 2), leading to the accumulation of hypoxia-inducible factor-1 α (HIF-1 α) in endothelial cells. Consequently, hypoxic lung cancer cells enhanced angiogenesis by exosomes derived from hypoxic cancer under both normoxic and hypoxic conditions. In addition, exosomal miR-23a also inhibits tight junction protein ZO-1, thereby increasing vascular permeability and cancer transendothelial migration. Inhibition of miR-23a by inhibitor administration decreased angiogenesis and tumour growth in a mouse model. Furthermore, elevated levels of circulating miR-23a are found in the sera of lung cancer patients, and miR-23a levels are positively correlated with proangiogenic activities. Taken together, our study reveals the clinical relevance and prognostic value of cancer-derived exosomal miR-23a under hypoxic conditions, and investigates a unique intercellular communication, mediated by cancer-derived exosomes, which modulates tumour vasculature.