Abnormal activation the WNT/β-catenin signaling pathway has been associated with ovarian carcinomas, but a specific WNT ligand and pertinent downstream mechanisms are not fully understood. In this study, we found abundant WNT7A in the epithelium of serous ovarian carcinomas, but not detected in borderline and benign tumors, normal ovary or endometrioid carcinomas. To characterize the role of WNT7A in ovarian tumor growth and progression, nude mice were injected either intraperitoneally (i.p.) or subcutaneously (s.c.) with WNT7A knocked down SKOV3.ip1 and overexpressed SKOV3 cells. In the i.p. group, mice receiving SKOV3.ip1 cells with reduced WNT7A expression developed significantly fewer tumor lesions. Gross and histological examination revealed greatly reduced invasion of WNT7A knockdown cells into intestinal mesentery and serosa compared to the control cells. Tumor growth was regulated by loss or overexpression of WNT7A in mice receiving s.c. injection as well. In vitro analysis of cell function revealed that cell proliferation, adhesion, and invasion were regulated by WNT7A. The activity of the TCF/LEF reporter was stimulated by overexpression of WNT7A in ovarian cancer cells. Co-transfection with WNT7A and FZD5 receptor further increased activity, and this effect was inhibited by co-transfection with SFRP2, or dominant-negative TCF4. Overexpression of WNT7A stimulated MMP7 promoter, and mutation of TCF binding sites in MMP7 promoter confirmed that activation of MMP7 promoter by WNT7A was mediated by β-catenin/TCF signaling. Collectively, these results suggest that re-expression of WNT7A during malignant transformation of ovarian epithelial cells plays a critical role in ovarian cancer progression mediated by WNT/β-catenin signaling pathway.
WNT7A; epithelial ovarian cancer; WNT/β-catenin pathway; cyclin D1; MMP7
Glioblastoma Multiforme (GBM) is the most malignant and lethal form of astrocytoma. The GBM patient survival time of approximately one year necessitates the identification of novel molecular targets and more effective therapeutics. Cadherin-11, a calcium-dependent cell-cell adhesion molecule and mesenchymal marker, plays a role in both normal tissue development and in cancer cell migration. The functional significance of cadherin-11 in GBM has not been investigated. Here, we show that cadherin-11 is expressed in human GBM tumors and human glioma stem-like cells by immunohistochemical labeling. Additionally, we show that cadherin-11 is expressed in human glioma cell lines by immunoblotting. shRNA mediated knockdown of cadherin-11 expression in human glioma cell lines results in decreased migration and growth factor-independent cell survival in vitro. More importantly, knockdown of cadherin-11 inhibits glioma cell survival in heterotopic and orthotopic mouse xenograft models. Together, our results demonstrate the functional significance of cadherin-11 expression in GBM and provide evidence for a novel role of cadherin-11 in promoting glioma cell survival in an in vivo environment. Thus, our studies suggest cadherin-11 is a viable molecular target for therapeutic intervention in GBM.
Cadherin-11; glioma; cell migration; cell survival; mesenchymal lineage
The Fanconi Anemia (FA) pathway is required for repair of DNA interstrand crosslinks (ICLs). FA pathway-deficient cells are hypersensitive to DNA ICL-inducing drugs such as Cisplatin. Conversely, hyperactivation of the FA pathway is a mechanism that may underlie cellular resistance to DNA ICL agents. Modulating FANCD2 monoubiquitination, a key step in the FA pathway, may be an effective therapeutic approach to conferring cellular sensitivity to ICL agents. Here, we show that inhibition of the Nedd8 conjugation system increases cellular sensitivity to DNA ICL-inducing agents. Mechanistically, the Nedd8 inhibition, either by siRNA-mediated knockdown of Nedd8 conjugating enzymes or treatment with a Nedd8 activating enzyme inhibitor MLN4924, suppressed DNA damage-induced FANCD2 monoubiquitination and CHK1 phosphorylation. Our data indicate that inhibition of the FA pathway is largely responsible for the heightened cellular sensitivity to DNA ICLs upon Nedd8 inhibition. These results suggest that a combination of Nedd8 inhibition with ICL-inducing agents may be an effective strategy for sensitizing a subset of drug-resistant cancer cells.
Fanconi Anemia; Nedd8; Chemosensitization
Treatment of base excision repair-proficient mouse fibroblasts with the DNA alkylating agent methyl methanesulfonate (MMS) and a small molecule inhibitor of poly(ADP-ribose) polymerase-1 (PARP-1) results in a striking cell killing phenotype, as previously reported. Earlier studies demonstrated that the mechanism of cell death is apoptosis and requires DNA replication, expression of PARP-1, and an intact S-phase checkpoint cell signaling system. It is proposed that activity-inhibited PARP-1 becomes immobilized at DNA repair intermediates, and that this blocks DNA repair and interferes with DNA replication, eventually promoting an S-phase checkpoint and G2/M block. Here we report studies designed to evaluate the prediction that inhibited PARP-1 remains DNA-associated in cells undergoing repair of alkylation-induced damage. Using chromatin immunoprecipitation with anti-PARP-1 antibody and qPCR for DNA quantification, a higher level of DNA was found associated with PARP-1 in cells treated with MMS plus PARP inhibitor than in cells without inhibitor treatment. These results have implications for explaining the extreme hypersensitivity phenotype after combination treatment with MMS and a PARP inhibitor.
PARP inhibitor; base excision repair; PARP-1; alkylation DNA damage; apoptosis
DICER1 is essential for the generation of mature microRNAs (miRNAs) and other short noncoding RNAs. Several lines of investigation implicate DICER1 as a tumor suppressor. Reduced DICER1 levels and changes in miRNA abundance have been associated with aggressive tumor phenotypes. The global effects of reduced DICER1 on mRNA transcript abundance in tumor cells remain largely unknown. We used shRNA to stably knock down DICER1 in endometrial cancer cell lines to begin to determine how reduced DICER1 activity contributes to tumor phenotypes. DICER1 knockdown did not affect cell proliferation but caused enhanced cell migration and growth in soft agar. miRNA and mRNA profiling in KLE cells revealed overall decreases in miRNA levels and changes in the relative abundance of many mRNAs. One of the most striking changes in mRNA levels was the upregulation of interferon stimulated genes (ISGs), the majority of which lack known miRNA target sequences. IFNβ, a key upstream regulator of the interferon response, was significantly increased in DICER1 knockdowns in the AN3CA, Ishikawa, and KLE endometrial cancer cell lines and in the normal endometrial cell line EM-E6/E7/TERT. IFNβ secreted in media from KLE and EM-E6/E7/TERT shDcr cells was sufficient to activate an interferon response in HT29 cells. The reduced miRNA processing in DICER1 knockdowns was associated with increases in pre-miRNAs in the cytoplasm. Our findings suggest elevated pre-miRNA levels trigger the interferon response to double-stranded RNA. We thus report a novel effect of reduced DICER1 function in cancer cells.
Endometrial cancer; DICER1; Interferon response; microRNA; RNA-Sequencing
Prostate cancer (PCa) metastases and hematopoietic stem cells (HSCs) frequently home to the bone marrow where they compete to occupy the same HSC niche. We have also shown that under conditions of hematopoietic stress, HSCs secrete the bone morphogenetic proteins (BMPs)-2 and BMP-6 that drives osteoblastic differentiation from mesenchymal precursors. Because it is not known, we examined if metastatic PCa cells can alter regulation of normal bone formation by HSCs and hematopoietic progenitor cells (HPCs). HSC/HPCs isolated from mice bearing non-metastatic and metastatic tumor cells were isolated and their ability to influence osteoblastic and osteoclastic differentiation was evaluated. When the animals were inoculated with the LNCaP C4-2B cell line which produces mixed osteoblastic and osteolytic lesions in bone, HPCs but not HSCs were able to induced stromal cells to differentiate down an osteoblastic phenotype. Part of the mechanism responsible for this activity was the production of BMP-2. On the other hand, when the animals were implanted with PC3 cells that exhibits predominantly osteolytic lesions in bone, HSCs derived from these animals were capable of directly differentiating into tartrate-resistant acid phosphatase (TRAP) positive osteoclasts through an interleukin-6 (IL-6) mediated pathway. These studies for the first time identify HSC/HPCs as novel targets for future therapy involved in the bone abnormalities of PCa.
Hematopoietic stem cells; osteoblast; osteoclast; differentiation; disseminated tumor cells
The lens epithelium derived growth factor p75 (LEDGF/p75) is a transcription co-activator that promotes resistance to oxidative stress- and chemotherapy-induced cell death. LEDGF/p75 is also known as the dense fine speckles autoantigen of 70 kD (DFS70), and has been implicated in cancer, HIV-AIDS, autoimmunity, and inflammation. To gain insights into mechanisms by which LEDGF/p75 protects cancer cells against stress, we initiated an analysis of its interactions with other transcription factors and the influence of these interactions on stress gene activation. We report here that both LEDGF/p75 and its short splice variant LEDGF/p52 interact with MeCP2, a methylation-associated transcriptional modulator, in vitro and in various human cancer cells. These interactions were established by several complementary approaches: transcription factor protein arrays, pull down and AlphaScreen® assays, co-immunoprecipitation, and nuclear co-localization by confocal microscopy. MeCP2 was found to interact with the N-terminal region shared by LEDGF/p75 and p52, particularly with the PWWP-CR1 domain. Like LEDGF/p75, MeCP2 bound to and transactivated the Hsp27 promoter (Hsp27pr). LEDGF/p75 modestly enhanced MeCP2-induced Hsp27pr transactivation in U2OS cells, while this effect was more pronounced in PC3 cells. LEDGF/p52 repressed Hsp27pr activity in U2OS cells. Interestingly, siRNA-induced silencing of LEDGF/p75 in U2OS cells dramatically elevated MeCP2-mediated Hsp27pr transactivation, whereas this effect was less pronounced in PC3 cells depleted of LEDGF/p75. These results suggest that the LEDGF/p75-MeCP2 interaction differentially influences Hsp27pr activation depending on the cellular and molecular context. These findings are of significance in understanding the contribution of this interaction to the activation of stress survival genes.
LEDGF/p75; MeCP2; protein-protein interactions; PWWP domain; transcription
Oxidative protein folding in the endoplasmic reticulum (ER) requires strict regulation of redox homeostasis. Disruption of the lumenal redox balance induces an integrated ER stress response that is associated with reduced protein translation, increased chaperone activity, and ultimately cell death. Imexon is a small molecule chemotherapeutic agent that has been shown to bind glutathione (GSH) and induce oxidative stress in tumor cells, however the mechanism of cytotoxicity is not well understood. This In this report, we investigate the effects of imexon on the integrated ER stress response in pancreatic carcinoma cells. Acute exposure to imexon induces an ER stress response characterized by accumulation of the oxidized form of the oxidoreductase Ero1α, phosphorylation of eIF2alpha and inhibition of protein synthesis. An RNA interference chemo-sensitization screen identified the eukaryotic translation initiation factor eIF2B5 as a target that enhanced imexon-induced growth inhibition of MiaPaCa-2 pancreatic cancer cells, but did not significantly augment the effects of imexon on protein synthesis. Concurrent reduction of intracellular thiols with N-acetyl cysteine reversed imexon activity, however co-treatment with superoxide scavengers had no effect, suggesting thiol binding may be a primary component of the oxidative effects of imexon. Moreover, the data suggest that disruption of the redox balance in the ER is a potential therapeutic target.
endoplasmic reticulum; oxidative stress; imexon; pancreatic
E2F1 is responsible for the regulation of FOXM1 expression, which plays a key role in epirubicin resistance. In here, we examined the role and regulation of E2F1 in response to epirubicin in cancer cells. We first demonstrated that E2F1 plays a key role in promoting FOXM1 expression, cell survival and epirubicin resistance as its depletion by siRNA attenuated FOXM1 induction and cell viability in response to epirubicin. We also found that the p38-MAPK activity mirrors the expression patterns of E2F1 and FOXM1 in both epirubicin sensitive and resistant MCF-7 breast cancer cells, suggesting p38 has a role in regulating E2F1 expression and epirubicin resistance. Consistently, studies using pharmacological inhibitors, siRNA knockdown and knockout MEFs revealed that p38 mediates the E2F1 induction by epirubicin and that the induction of E2F1 by p38 is in turn mediated through its downstream kinase MK2 (MAPK-activated protein kinase 2; MAPKAPK2). In agreement, in vitro phosphorylation assays showed that MK2 can directly phosphorylate E2F1 at Ser-364. Transfection assays also demonstrated that E2F1 phosphorylation at Ser-364 participates in its induction by epirubicin, but also suggests that other phosphorylation events are also involved. In addition, the p38-MK2 axis can also limit JNK induction by epirubicin and notably, JNK represses FOXM1 expression. Collectively, these findings underscore the importance of p38-MK2 signalling in the control of E2F1 and FOXM1 expression as well as epirubicin sensitivity.
p38; MK2; JNK; E2F-1; epirubicin; FOXM1; resistance
Protein-tyrosine phosphatase 1B (PTP1B), a well-established metabolic regulator, plays an important role in breast cancer. Using whole-body PTP1B knockout mice, recent studies have shown that PTP1B ablation delays HER2/Neu-induced mammary cancer. Whether PTP1B plays a cell-autonomous or a non-cell-autonomous role in HER2/Neu-evoked tumorigenesis and whether it is involved in tumor maintenance was unknown. We generated mice expressing HER2/Neu and lacking PTP1B specifically in the mammary epithelium. We found that mammary-specific deletion of PTP1B delays the onset of HER2/Neu-evoked mammary tumors, establishing a cell autonomous role for PTP1B in such neoplasms. We also deleted PTP1B in established mouse mammary tumors or depleted PTP1B in human breast cancer cell lines grown as xenografts. PTP1B inhibition did not affect tumor growth in either model showing that neither epithelial nor stromal PTP1B is necessary for tumor maintenance. Taken together, our data show that despite the PTP1B contribution to tumor onset, it is not essential for tumor maintenance. This suggests that PTP1B inhibition could be effective in breast tumor prevention.
PTPN1; PTP1B; Tyrosine Phosphatases; HER2; Breast Cancer
Bradykinin (BK) has been shown to promote growth and migration of head and neck squamous cell carcinoma (HNSCC) cells via epidermal growth factor receptor (EGFR) transactivation. It has also been reported that BK can cause the induction of cyclooxygenase-2 (COX-2), a pro-tumorigenic enzyme, via the MAPK (Mitogen-Activated Protein Kinase) pathway in human airway cells. To determine whether COX-2 is up-regulated by BK in HNSCC, the current study investigated BK- induced EGFR transactivation, MAPK activation, and cyclooxygenase-2 (COX-2) expression in human HNSCC cells. BK induced a concentration- and time-dependent induction of COX-2 protein in HNSCC, which was preceded by phosphorylation of EGFR and MAPK. These effects were abolished by the B2 receptor (B2R) antagonist Hoe 140 but not the B1 receptor (B1R) antagonist, Lys-[Leu8]des-Arg9-BK. COX-2 induction was accompanied by increased release of PGE2. No effect of a B1R agonist (des-Arg9-BK) on p-MAPK or COX-2 expression was observed. B2R protein was found to be expressed in all four head and neck cell lines tested. Immunohistochemical analysis and immunoblot analysis revealed that B2R, but not B1R, was significantly over-expressed in HNSCC tumors compared to levels in normal mucosa from the same patient. In HNSCC cells, the BK-induced expression of COX-2 was inhibited by the EGFR kinase inhibitor gefitinib or mitogen activated protein kinase kinases (MEK) inhibitors (PD98059 or U0126). These results suggest that EGFR and MAPK are required for COX-2 induction by BK. Up-regulation of the B2R in head and neck cancers suggests this pathway is involved in HNSCC tumorigenesis.
Bradykinin; B2 receptor; EGFR; MAPK; cyclooxygenase-2; head and neck cancer
Glioblastoma is universally fatal because of its propensity for rapid recurrence due to highly migratory tumor cells. Unraveling the genomic complexity that underlies this migratory characteristic could provide therapeutic targets that would greatly complement current surgical therapy. Using multiple high-resolution genomic screening methods, we identified a single locus, Adherens Junctional Associated Protein 1 (AJAP1) on chromosome 1p36, that is lost or epigenetically silenced in many glioblastomas. We found AJAP1 expression absent or reduced in 86% and 100% of primary glioblastoma tumors and cell lines, respectively, and the loss of expression correlates with AJAP1 methylation. Restoration of AJAP1 gene expression by transfection or demethylation agents results in decreased tumor cell migration in glioblastoma cell lines. This work demonstrates the significant loss of expression of AJAP1 in glioblastoma and provides evidence of its role in the highly migratory characteristic of these tumors.
AJAP1 (Adherens junctional associated protein); glioblastoma; malignant glioma; methylation; gene deletion; epigenetics; migration
Pancreatic ductal adenocarcinomas (PDAC) are highly invasive and metastatic neoplasms commonly unresponsive to current drug therapy. Overwhelmingly, PDAC harbors early constitutive, oncogenic mutations in K-RasG12D that exist prior to invasion. Histologic and genetic analyses of human PDAC biopsies also exhibit increased expression of ERK1/2 and pro-invasive matrix metalloproteinases (MMPs); indicators of poor prognosis. However, the distinct molecular mechanisms necessary for K-Ras – ERK1/2 signaling and its influence on MMP-directed stromal invasion in primary human pancreatic ductal epithelial cells (PDECs) has yet to be elucidated in 3D. Expression of oncogenic K-RasG12D alone in genetically-defined PDECs reveals increased invadopodia and epithelial-to-mesenchymal transition markers, but only when cultured in a 3D model incorporating a basement membrane analog. Activation of extracellular signal-related kinase 2 (ERK2), but not ERK1, also occurs only in K-RasG12D mutated PDECs cultured in 3D and is a necessary intracellular signaling event for invasion based upon pharmacologic and shRNA inhibition. Increased active invasion of K-RasG12D PDECs through the basement membrane model is associated with a specific microarray gene expression signature and induction of MMP endopeptidases. Specifically, MMP-1 RNA, its secreted protein, and its proteolytic cleavage activity are amplified in K-RasG12D PDECs when assayed by RT q-PCR, ELISA, and fluorescence resonance energy transfer (FRET). Importantly, shRNA silencing of MMP-1 mimics ERK2 inhibition and disrupts active, vertical PDEC invasion. ERK2-isoform and MMP-1 targeting are shown to be viable strategies to attenuate invasion of K-RasG12D mutated human pancreatic cancer cells in a 3D tumor microenvironment.
K-Ras; ERK2; Pancreatic Cancer; 3D Invasion; MMP-1
The contribution of the Wnt signaling pathway to HPV-induced carcinogenesis is poorly understood. In high-grade dysplastic lesions that are caused by high-risk human papilloma viruses (HR-HPVs), β-catenin is often located in the cell nucleus, which suggests that Wnt pathway may be involved in the development of HPV-related carcinomas. Most of the oncogenic potential of HR-HPVs resides on the E6 protein’s PDZ-binding domain. We hypothesized that the PDZ-binding domain of the HPV16-E6 oncoprotein induces the nuclear accumulation of β-catenin due to its capacity to degrade PDZ-containing cellular targets. To test this hypothesis, we evaluated the staining pattern of β-catenin in the skin epidermis of transgenic mice expressing the full-length E6 oncoprotein (K14E6 mice) and measured LacZ gene expression in K14E6 mice that were crossed with a strain expressing LacZ that was knocked into the Axin2 locus (Axin2+/LacZ mice). Here, we show that the E6 oncoprotein enhances the nuclear accumulation of β-catenin, the accumulation of cellularβ-catenin-responsive genes and the expression of LacZ. None of these effects were observed when a truncated E6 oncoprotein that lacks the PDZ-binding domain was expressed alone (K14E6ΔPDZ mice) or in combination with Axin2+/LacZ. Conversely, co-transfection with either E6 or E6ΔPDZ similarly enhanced canonical Wnt signaling in short-term in vitro assays that utilized a luciferase Wnt/β-catenin/TCF-dependent promoter. We propose that the activation of canonical Wnt signaling could be induced by the HPV16-E6 oncoprotein; however, the participation of the E6 PDZ-binding domain seems to be important in in vivo models only.
HPV; Wnt/β-catenin; K14E6; K14E6-ΔPDZ; Axin2+/LacZ
Pancreatic cancer is the fourth leading cause of cancer deaths in developed countries. Smoking is an established risk factor for this malignancy but the underlying mechanisms are poorly understood. Previous reports have provided evidence that nicotinic acetylcholine receptors (nAChRs) and beta-adrenergic receptors (β-ARs) stimulate the growth and migration of pancreatic cancer cells. But a potential cooperation of these two receptor families in the regulation of pancreatic cancer has not been studied to date. Using two pancreatic cancer cell lines and immortalized pancreatic duct epithelia in vitro, our current data show, that all three cell lines synthesized and released the catecholamine neurotransmitters noradrenaline and adrenaline upon exposure to nicotine and that this activity was regulated by α3, α5, and α7-nAChRs. In accord with the established function of these catecholamines as β-AR agonists, nicotine-induced cell proliferation was blocked by the β-AR antagonist propranolol. Nicotine-induced proliferation was also abolished by the α7-nAChR antagonist α-bungarotoxin while catecholamine production in response to nicotine was blocked by gene knockdown of the α3, α5, and α7-nAChRs. The nicotinic agonists acetylcholine, nicotine, and its nitrosated carcinogenic derivative NNK induced the phosphorylation of CREB, ERK, Src and AKT and these responses were inhibited by propranolol. Our findings identify this hitherto unknown autocrine catecholamine loop as an important regulatory cascade in pancreatic cancer that may prove a promising new target for cancer intervention.
Nicotinic receptors; beta-adrenergic receptor; autocrine growth factors; pancreatic cancer; neurotransmitters
Prostate carcinoma is among the most common causes of cancer-related death in men, representing 15% of all male malignancies in developed countries. Neuroendocrine differentiation has been associated with tumor progression, poor prognosis and with the androgen-independent status. Currently, no successful therapy exists for advanced, castration-resistant disease. Because hypoxia has been linked to prostate cancer progression and unfavourable outcome, we sought to determine whether hypoxia would impact the degree of neuroendocrine differentiation of prostate cancer cells, in vitro.
exposure of LNCaP cells to low oxygen tension induced a neuroendocrine phenotype, associated with an increased expression of the transcription factor neurogenin3 and neuroendocrine markers, such as neuron-specific enolase, chromogranin A and β3-tubulin. Moreover, hypoxia triggered a significant decrease of Notch 1 and Notch 2 mRNA and protein expression, with subsequent down regulation of Notch-mediated signalling, as demonstrated by reduced levels of the Notch target genes, Hes1 and Hey1. Neuroendocrine differentiation was promoted by attenuation of Hes1 transcription, as cells expressing a dominant negative form of Hes1 displayed increased levels of neuroendocrine markers under normoxic conditions. Although hypoxia down regulated Notch 1 and Notch 2 mRNA transcription and receptor activation also in the androgen independent cell lines, PC3 and Du145, it did not change the extent of NE differentiation in these cultures, suggesting that androgen sensitivity may be required for transdifferentiation to occur.
hypoxia induces neuroendocrine differentiation of LNCaP cells in vitro, which appears to be driven by the inhibition of Notch signalling with subsequent down-regulation of Hes1 transcription.
prostate cancer; hypoxia; notch; Hes; LNCaP; neuroendocrine differentiation
Although hyper-activated mTOR is well recognized as being pivotal to prostate cancer growth and progression, the underlying mechanisms by which it promotes such responses remain incompletely understood. Here we show that rapamycin activates Smads 1 and 5 in human prostate cancer cells and tissues through blocking mTORC1 kinase. ShRNA-based gene silencing and gene overexpression approaches reveal that Smads 1 and 5 mediate while Smad8 represses rapamycin-induced cell death and expression of the BMP transcriptional target Id1 in human prostate cancer cell lines. Moreover, such phospho-Smad1/5-mediated rapamycin responses were blocked by LDN-193189 (a BMPRI kinase inhibitor) or Noggin (a BMP antagonist) in LNCaP prostate cancer cells. Likewise, the mTOR kinase inhibitors Ku-0063794 and WYE-354 each enhanced phosphorylation of Smad1/5. Intriguingly, silencing Raptor alone enhanced while silencing Rictor repressed the phosphorylation of Smad1/5, indicating that mTORC1 represses while mTORC2 activates BMP signaling. Immunohistochemical analysis showed increased levels of phospho-Smad1/5 concomitant with suppression of phospho-S6 and Survivin levels in PC3 human prostate cancer xenografts in athymic mice administered rapamycin (i.p., 5 mg/kg/day, 2 to 6 days). Moreover, we show that compared to prostate tumor tissue from untreated patients, levels of phospho-Smad1/5 were significantly elevated in the prostate tumor tissue of high-risk prostate cancer patients who received 8 weeks of the rapalog everolimus as part of a neoadjuvant clinical trial prior to undergoing local definitive therapy by radical prostatectomy. Taken together, our data implicate Smads 1, 5 and 8 as potential prognostic markers and therapeutic targets for mTOR inhibition therapy of prostate cancer.
BMP4; rapamycin; prostate; Smad1; Smad 5; Smad8; apoptosis
Infiltration of immune cells, specifically macrophages, into the tumor microenvironment has been linked to increased mammary tumor formation and progression. Activation of growth factor receptor signaling pathways within mammary epithelial cells, such as the fibroblast growth factor receptor 1 (FGFR1) pathway, induces recruitment of macrophages to the mammary epithelium. These macrophages promote increased epithelial cell proliferation and angiogenesis. However, the specific mechanisms by which these macrophages are regulated by the preneoplastic epithelial cells and the mechanisms of action of the macrophages within the developing FGFR1-driven tumor microenvironment remain unknown. In this study, we demonstrate that activation of inducible FGFR1 in mammary glands leads to decreased activity of the transforming growth factor beta (TGFβ)/Smad3 pathway in macrophages associated with early stage lesions. Further studies demonstrate that macrophages have increased expression of inflammatory chemokines that bind Cxcr2 following exposure to conditioned media from mammary epithelial and tumor cells in which the FGF pathway had been activated. The increase in these ligands is inhibited following activation of the TGFβ pathway, suggesting that decreased TGFβ signaling contributes to the upregulation of these chemokines. Using co-culture studies, we further demonstrate that macrophages are capable of promoting epithelial and tumor cell migration and invasion through activation of Cxcr2. These results indicate that macrophage-derived Cxcr2 ligands may be important for promoting mammary tumor formation regulated by FGFR signaling. Furthermore, these results suggest that targeting Cxcr2 may represent a novel therapeutic strategy for breast cancers that are associated with high levels of infiltrating macrophages.
Mammary tumor; breast cancer; FGFR1; CXCR2
Breast cancer metastasis is a major clinical problem. The molecular basis of breast cancer progression to metastasis remains poorly understood. PELP1 is an estrogen receptor (ER) coregulator that has been implicated as a proto-oncogene whose expression is deregulated in metastatic breast tumors and whose expression is retained in ER-negative tumors. We examined the mechanism and significance of PELP1-mediated signaling in ER-negative breast cancer progression using two ER-negative model cells (MDA-MB231 and 4T1 cells) that stably express PELP1-shRNA. These model cells had reduced PELP1 expression (75% of endogenous levels) and exhibited less propensity to proliferate in growth assays in vitro. PELP1 down regulation substantially affected migration of ER-negative cells in Boyden chamber and invasion assays. Using mechanistic studies, we found that PELP1 modulated expression of several genes involved in the epithelial mesenchymal transition EMT including MMPs, Snail1, Twist, and ZEB. In addition, PELP1 knockdown reduced the in vivo metastatic potential of ER-negative breast cancer cells and significantly reduced lung metastatic nodules in a xenograft assay. These results implicate PELP1 as having a role in ER-negative breast cancer metastasis, reveal novel mechanism of coregulator regulation of metastasis via promoting cell motility / EMT by modulating expression of genes, and suggest PELP1 may be a potential therapeutic target for metastatic ER-negative breast cancer.
ER-coactivators; Proto-oncogene; Breast cancer; Metastasis; PELP1
Deleted in liver cancer 1 (DLC1) is a GTPase activating protein (GAP) domain containing tumor suppressor that localizes to focal adhesions. In cancer cells, loss of DLC1 is known to enhance cancer cell migration. However, the role of DLC1 in normal cell migration has not been well studied. Here, we show that silencing of DLC1 (shDLC1) in normal prostate epithelial cells reduces cell migration in both transwell and wound healing assays. This migration defect is mainly due to upregulation of plasminogen activator inhibitor 1 (PAI-1). Silencing of PAI-1 rescues the shDLC1 reduced migration phenotype. Re-expression of DLC1 suppresses PAI-1 and restores the migration defect as well. In contrast, DLC1-K714E (GAP inactive) mutant neither decreases the PAI-1 level nor rescues the shDLC1 migration defect. Interestingly, DLC1-Y442F (tensin-binding and focal adhesion-localizing defective) mutant is able to suppress PAI-1 expression but does not restore the migration defect. Furthermore, PAI-1 upregulation in shDLC1 cells is EGFR-MEK pathway dependent and is able to promote in vitro angiogenesis. Together, our results demonstrate that at least two new mechanisms are involved in DLC1-mediated normal cell migration. (I) DLC1 modulates the expression of PAI-1, which is a negative regulator for cell migration, in a GAP domain and EGFR-MEK dependent manner. (II) Independent of PAI-1, the interaction of DLC1 with tensin members positively regulates cell migration.
DLC; PAI-1; cell migration; focal adhesion; prostate
Tumor Necrosis Factor (TNF)-Related Apoptosis Inducing Ligand (TRAIL) is a member of the TNF super family and has been shown to induce apoptosis in many cancer cell lines but not in normal cells. Breast cancers can be divided into different subgroups based on the expression of estrogen and progesterone receptors, HER-2 amplification, or the lack of these three markers (known as triple-negative or basal-type breast cancer). Our group and others have shown previously that triple-negative breast cancer cell lines are sensitive to TRAIL while others are relatively resistant. In an earlier study, we reported that inhibition of WEE1, a cell cycle checkpoint regulator, causes increased cell death in breast cancer cell lines. In this study, we tested the effects of WEE1 inhibition on TRAIL-mediated apoptosis in breast cancer cell lines. Pre-treatment with WEE1 inhibitor or knockdown of WEE1 increased the toxicity of TRAIL in the basal/triple-negative breast cancer cell lines compared to WEE1 inhibitor or TRAIL treatment alone. The enhanced cell death is attributed to increased surface expression of death receptors, increased caspase activation which could be blocked by the pan-caspase inhibitor, Z-VAD-FMK, thereby rescuing cells from caspase-mediated apoptosis. The cell death was initiated primarily by caspase-8 since knockdown of caspase-8 and not of any other initiator caspases (i.e, caspase-2, -9, or -10) rescued cells from WEE1 inhibitor sensitized TRAIL-induced cell death. Taken together, the data suggest that the combination of WEE1 inhibitor and TRAIL could provide a novel combination for the treatment of basal/triple-negative breast cancer.
TRAIL; WEE1 inhibitor; breast cancer; apoptosis; caspases
G protein-coupled receptor kinases (GRKs) regulate the function of G protein-coupled receptors (GPCRs). Previously, we found that GPCR (CXCR4)-mediated astrocytoma growth was dependent upon abnormally sustained CXCR4 signaling and was correlated with decreased GRK-mediated receptor phosphorylation. As CXCR4 has also been implicated in the stimulation of high-grade glioma growth, we sought to determine whether dysregulation of GRK expression and/or function might also be present in high-grade gliomas. In an analysis of data from The Cancer Genome Atlas we found that GRK3 expression is frequently decreased in GBM of the Classical subtype, which possess signature amplification or mutational activation of the EGF receptor. We tested the correlation between GRK3 expression and GBM subtypes, as well as the relationship between the activation of the EGF and other growth factor receptor pathways and GRK expression. In analyses of primary GBM tissue and RNA specimens, we found that GRK3 expression is correlated with established criteria for GBM subtyping including expression of EGF receptor, PDGFRα receptor, NF1, PTEN, CDKN2A and neurofilament. We also found that established drivers of gliomagenesis, the EGF, PDGF and TGF-β pathways all regulate GRK expression. Co-culture experiments, designed to mimic critical interactions between tumor and brain microvascular endothelial cells, demonstrated that specifically increasing GRK3 expression reduced the trophic effect of endothelial cells on tumor cells. Together, these experiments demonstrate that GRK3 is a negative regulator of cell growth whose expression is preferentially reduced in GBM of the Classical subtype as a consequence of activity in primary gliomagenic pathways.
GRK; GPCR; GBM; TCGA; Molecular Subtypes
Commonly observed in colorectal cancer (CRC) is elevated expression of the prostaglandin synthase cyclooxygenase-2 (COX-2). In normal intestinal epithelium, the COX-2 mRNA is targeted for rapid decay through the 3′-untranslated region (3′UTR) adenylate- and uridylate (AU)-rich element (ARE), whereas in tumors ARE-mediated decay is compromised. Here we demonstrate that the COX-2 ARE can mediate degradation through microRNA-mediated regulation. We identified miR-16 to bind the COX-2 3′UTR and inhibit COX-2 expression by promoting rapid mRNA decay. In CRC cells and tumors, miR-16 levels were decreased ~2-fold and miR-16 expression in cancer cells attenuated COX-2 expression and prostaglandin synthesis. The COX-2 ARE is also bound by the RNA-binding protein HuR. In CRC tumors, HuR is overexpressed and localized within the cytoplasm where it promotes ARE-mRNA stabilization. Under conditions of HuR overexpression, miR-16 was unable to promote rapid mRNA decay through the COX-2 ARE. Ribonucleoprotein immunoprecipitation of HuR demonstrated direct association with miR-16 that was reversed when cytoplasmic trafficking of HuR was inhibited. Furthermore, this interaction between HuR and miR-16 promoted the down regulation of miR-16. These new results identify miR-16 as a central post-transcriptional regulator of COX-2 and demonstrate the ability of elevated levels of HuR to antagonize miR-16 function. Along with insight into altered ARE-mediated mRNA decay observed in CRC, these findings provide a new explanation for tumor-derived loss of miR-16.
HuR; microRNA-16; COX-2; AU-rich elements; RNA stability; colon cancer
Extracellular superoxide dismutase (EcSOD) is an important superoxide scavenger in the lung where its loss, sequence variation, or abnormal expression contributes to lung diseases; however, the role of EcSOD in lung cancer has yet to be studied. We hypothesized that EcSOD loss could affect malignant progression in lung, and could be either genetic or epigenetic in nature. To test this we analyzed EcSOD expression, gene copy number, promoter methylation and chromatin accessibility in normal lung and carcinoma cells. We found that normal airway epithelial cells expressed abundant EcSOD and had an unmethylated promoter, whereas EcSOD-negative lung cancer cells displayed aberrant promoter hypermethylation and decreased chromatin accessibility. 5-aza-dC induced EcSOD suggesting that cytosine methylation was causal, in part, to silencing. In 48/50 lung tumors EcSOD mRNA was significantly lower as early as stage I, and the EcSOD promoter was hypermethylated in 8/10 (80%) adenocarcinomas compared to 0/5 normal lung samples. In addition, 20% of the tumors showed LOH of EcSOD. Re-expression of EcSOD attenuated the malignant phenotype of lung carcinoma cells by significantly decreasing invasion and survival. Finally, EcSOD decreased heparanase and syndecan-1 mRNAs in part by reducing NF-κB. By contrast, MnSOD and CuZnSOD showed no significant changes in lung tumors and had no effect on heparanase expression. Taken together, the loss of EcSOD expression is unique among the superoxide dismutases in lung cancer and is the result of EcSOD promoter methylation and LOH, suggesting that its early loss may contribute to ECM remodeling and malignant progression.
SOD3; EcSOD; Heparanase; Syndecan-1; NF-κB; DNA methylation
Epithelial ovarian carcinoma is a deadly disease, and little is known about the mechanisms underlying its metastatic progression. Using human specimens and established cell lines, we determined that the G protein-coupled seven-transmembrane fractalkine receptor (CX3CR1) is expressed in primary and metastatic ovarian carcinoma cells. Ovarian carcinoma cells robustly migrated toward CX3CL1, a specific ligand of CX3CR1, in a CX3CR1-dependent manner. Silencing of CX3CR1 reduced migration toward human ovarian carcinoma ascites fluid by approximately 70%. Importantly, adhesion of ovarian carcinoma cells to human peritoneal mesothelial cells was dependent on CX3CL1/CX3CR1 signaling. In addition, CX3CL1 was able to induce cellular proliferation. Together, our data suggest that the fractalkine network may function as a major contributor to the progression of epithelial ovarian carcinoma, and further attention to its role in the metastasis of this deadly malignancy is warranted.
ovarian carcinoma; CX3CR1; migration; adhesion; proliferation