"The intracellular transfer of information (biological activation/inhibition) through a signal pathway. In each signal transduction system, an activation/inhibition signal from a biologically active molecule (hormone, neurotransmitter) is mediated via the coupling of a receptor/enzyme to a second messenger system or to an ion channel. Signal transduction plays an important role in activating cellular functions, cell differentiation, and cell proliferation. Examples of signal transduction systems are the GAMMA-AMINOBUTYRIC ACID-postsynaptic receptor-calcium ion channel system, the receptor-mediated T-cell activation pathway, and the receptor-mediated activation of phospholipases. Those coupled to membrane depolarization or intracellular release of calcium include the receptor-mediated activation of cytotoxic functions in granulocytes and the synaptic potentiation of protein kinase activation. Some signal transduction pathways may be part of larger signal transduction pathways; for example, protein kinase activation is part of the platelet activation signal pathway." (Source: MeSH)
Figure: An overview of major signal transduction pathways
Source: https://en.wikipedia.org/wiki/File:Signal_transduction_pathways.svg (License: CC BY-SA 3.0)
Introduction to Cancer Biology (Part 1): Abnormal Signal Transduction
mechanismsinmedicine.com Educational animation which explains the mechanism of abnormal signal transduction resulting in uncontrolled cell proliferation. This animation also provides an overview of the potential targets of anticancer therapies.
This list of publications is regularly updated (Source: PubMed).
Suresh S, McCallum L, Crawford LJ, et al. The matricellular protein CCN3 regulates NOTCH1 signalling in chronic myeloid leukaemia. J Pathol. 2013; 231(3):378-87 [PubMed] Related Publications
Deregulated NOTCH1 has been reported in lymphoid leukaemia, although its role in chronic myeloid leukaemia (CML) is not well established. We previously reported BCR-ABL down-regulation of a novel haematopoietic regulator, CCN3, in CML; CCN3 is a non-canonical NOTCH1 ligand. This study characterizes the NOTCH1–CCN3 signalling axis in CML. In K562 cells, BCR-ABL silencing reduced full-length NOTCH1 (NOTCH1-FL) and inhibited the cleavage of NOTCH1 intracellular domain (NOTCH1-ICD), resulting in decreased expression of the NOTCH1 targets c-MYC and HES1. K562 cells stably overexpressing CCN3 (K562/CCN3) or treated with recombinant CCN3(rCCN3) showed a significant reduction in NOTCH1 signalling (> 50% reduction in NOTCH1-ICD, p < 0.05).Gamma secretase inhibitor (GSI), which blocks NOTCH1 signalling, reduced K562/CCN3 colony formation but increased that of K562/control cells. GSI combined with either rCCN3 or imatinib reduced K562 colony formation with enhanced reduction of NOTCH1 signalling observed with combination treatments. We demonstrate an oncogenic role for NOTCH1 in CML and suggest that BCR-ABL disruption of NOTCH1–CCN3 signalling contributes to the pathogenesis of CML.
Herold CI, Anders CK New targets for triple-negative breast cancer. Oncology (Williston Park). 2013; 27(9):846-54 [PubMed] Related Publications
Triple-negative breast cancer (TNBC) lacks the three most commonly targeted receptors in human breast cancer--the estrogen receptor (ER), progesterone receptor (PR), and human epidermal growth factor receptor 2 (HER2)/neu--and it is associated with an aggressive natural history. More recently, TNBC has been further dissected into smaller, distinct subsets with unique molecular alterations and response to therapy. Large-scale genomic projects have yielded new knowledge about the molecular characteristics of TNBC, including similarities with high-grade serous ovarian cancers, suggesting a possible coordinated treatment algorithm for these malignancies. Moreover, translation of preclinical findings has led to clinical trials testing a plethora of targets and pathways in TNBC, which will be reviewed here; these include epidermal growth factor receptor (EGFR), angiogenesis, DNA repair capacity, epigenetic regulation, androgen receptor (AR) and folate receptor (FR) signaling, cell-cycle control, and cell survival. Given the complexity of TNBC biology and the lack of "traditional" therapeutic targets, the advancement of care for women with TNBC will require a true partnership between clinicians, translational investigators, and basic scientists.
Corre J, Hébraud B, Bourin P Concise review: growth differentiation factor 15 in pathology: a clinical role? Stem Cells Transl Med. 2013; 2(12):946-52 [PubMed] Article available free on PMC after 01/12/2014 Related Publications
Growth differentiation factor 15 (GDF15) is a divergent member of the transforming growth factor β family discovered in a broad range of cells, as indicated by the diversity of its nomenclature. However, the only tissue that expresses a high amount of GDF15 in the physiologic state is placenta. GDF15 is easily detected in blood, and its concentration varies with age. In fact, increased blood concentration of GDF15 is associated with numerous pathological conditions. However, the biological significance underlying these observations is far from clear. GDF15 could have a positive or negative role depending on the state of cells or their environment. Furthermore, study of its biology is hampered by lack of knowledge of its receptor and thus the signaling pathways that drive its action. GDF15 seems to be an integrative signal in pathologic conditions, giving information on severity of disease. Its effectiveness in classifying patients to modulate treatment remains to be shown. Development of therapeutic interventions with GDF15 or anti-GDF15 agents remains difficult until we uncover the mechanism that drives its activity.
The mTOR protein kinase controls anabolic processes as part of mTOR complexes 1 and 2 (mTORC1 and mTORC2). The two complexes are now shown to be involved in a negative feedback regulatory mechanism, in which mTORC1 stimulation inactivates mTORC2 through the inhibitory phosphorylation of the mTORC2 component Sin1.
Genovesi LA, Ng CG, Davis MJ, et al. Sleeping Beauty mutagenesis in a mouse medulloblastoma model defines networks that discriminate between human molecular subgroups. Proc Natl Acad Sci U S A. 2013; 110(46):E4325-34 [PubMed] Article available free on PMC after 12/05/2014 Related Publications
The Sleeping Beauty (SB) transposon mutagenesis screen is a powerful tool to facilitate the discovery of cancer genes that drive tumorigenesis in mouse models. In this study, we sought to identify genes that functionally cooperate with sonic hedgehog signaling to initiate medulloblastoma (MB), a tumor of the cerebellum. By combining SB mutagenesis with Patched1 heterozygous mice (Ptch1(lacZ/+)), we observed an increased frequency of MB and decreased tumor-free survival compared with Ptch1(lacZ/+) controls. From an analysis of 85 tumors, we identified 77 common insertion sites that map to 56 genes potentially driving increased tumorigenesis. The common insertion site genes identified in the mutagenesis screen were mapped to human orthologs, which were used to select probes and corresponding expression data from an independent set of previously described human MB samples, and surprisingly were capable of accurately clustering known molecular subgroups of MB, thereby defining common regulatory networks underlying all forms of MB irrespective of subgroup. We performed a network analysis to discover the likely mechanisms of action of subnetworks and used an in vivo model to confirm a role for a highly ranked candidate gene, Nfia, in promoting MB formation. Our analysis implicates candidate cancer genes in the deregulation of apoptosis and translational elongation, and reveals a strong signature of transcriptional regulation that will have broad impact on expression programs in MB. These networks provide functional insights into the complex biology of human MB and identify potential avenues for intervention common to all clinical subgroups.
Liu P, Gan W, Inuzuka H, et al. Sin1 phosphorylation impairs mTORC2 complex integrity and inhibits downstream Akt signalling to suppress tumorigenesis. Nat Cell Biol. 2013; 15(11):1340-50 [PubMed] Article available free on PMC after 01/05/2014 Related Publications
The mechanistic target of rapamycin (mTOR) functions as a critical regulator of cellular growth and metabolism by forming multi-component, yet functionally distinct complexes mTORC1 and mTORC2. Although mTORC2 has been implicated in mTORC1 activation, little is known about how mTORC2 is regulated. Here we report that phosphorylation of Sin1 at Thr 86 and Thr 398 suppresses mTORC2 kinase activity by dissociating Sin1 from mTORC2. Importantly, Sin1 phosphorylation, triggered by S6K or Akt, in a cellular context-dependent manner, inhibits not only insulin- or IGF-1-mediated, but also PDGF- or EGF-induced Akt phosphorylation by mTORC2, demonstrating a negative regulation of mTORC2 independent of IRS-1 and Grb10. Finally, a cancer-patient-derived Sin1-R81T mutation impairs Sin1 phosphorylation, leading to hyper-activation of mTORC2 by bypassing this negative regulation. Together, our results reveal a Sin1-phosphorylation-dependent mTORC2 regulation, providing a potential molecular mechanism by which mutations in the mTORC1-S6K-Sin1 signalling axis might cause aberrant hyper-activation of the mTORC2-Akt pathway, which facilitates tumorigenesis.
Chen YJ, Cheng YJ, Hung AC, et al. The synthetic flavonoid WYC02-9 inhibits cervical cancer cell migration/invasion and angiogenesis via MAPK14 signaling. Gynecol Oncol. 2013; 131(3):734-43 [PubMed] Related Publications
OBJECTIVE: Development of flavonoids as potential chemotherapeutic agents for cervical cancer may open new avenues in anticancer drug design. In this study, the cytotoxic activity and anti-migration/invasion/angiogenesis efficiency of the synthetic flavonoid WYC02-9 on cervical cancer and the underlying mechanisms are explored. METHODS: XTT cell viability assay, apoptosis assays, cell cycle analysis, and immunoblotting analysis were applied to study the biologic activity of WYC02-9. Anchorage independent soft agar assay and xenograft nude mouse model were applied to study the anti-tumor effect of WYC02-9 in vivo. Wound healing assay, transwell invasion assay, and gelatin zymography analysis were applied to study the effect of WYC02-9 on cancer cell migration and invasion. Tube formation analysis, zebrafish angiogenesis model, and nude mice Matrigel plug angiogenesis assay were applied to study the effect of WYC02-9 on angiogenesis. RESULTS: WYC02-9 induced cytotoxicity on cervical cancer cells by promoting apoptosis and G2/M cell cycle arrest. WYC02-9 inhibited cervical cancer cell migration/invasion and angiogenesis in vitro and in vivo via MAPK14 pathway. CONCLUSION: WYC02-9 significantly inhibited cervical cancer cell proliferation/migration/invasion and angiogenesis in vitro and in vivo. WYC02-9 may be a promising drug candidate for cervical cancer chemotherapy.
Jaramillo MC, Zhang DD The emerging role of the Nrf2-Keap1 signaling pathway in cancer. Genes Dev. 2013; 27(20):2179-91 [PubMed] Article available free on PMC after 15/04/2014 Related Publications
The Nrf2 (nuclear factor erythroid 2 [NF-E2]-related factor 2 [Nrf2])-Keap1 (Kelch-like erythroid cell-derived protein with CNC homology [ECH]-associated protein 1) signaling pathway is one of the most important cell defense and survival pathways. Nrf2 can protect cells and tissues from a variety of toxicants and carcinogens by increasing the expression of a number of cytoprotective genes. As a result, several Nrf2 activators are currently being tested as chemopreventive compounds in clinical trials. Just as Nrf2 protects normal cells, studies have shown that Nrf2 may also protect cancer cells from chemotherapeutic agents and facilitate cancer progression. Nrf2 is aberrantly accumulated in many types of cancer, and its expression is associated with a poor prognosis in patients. In addition, Nrf2 expression is induced during the course of drug resistance. Collectively, these studies suggest that Nrf2 contributes to both intrinsic and acquired chemoresistance. This discovery has opened up a broad spectrum of research geared toward a better understanding of the role of Nrf2 in cancer. This review provides an overview of (1) the Nrf2-Keap1 signaling pathway, (2) the dual role of Nrf2 in cancer, (3) the molecular basis of Nrf2 activation in cancer cells, and (4) the challenges in the development of Nrf2-based drugs for chemoprevention and chemotherapy.
Tordella L, Koch S, Salter V, et al. ASPP2 suppresses squamous cell carcinoma via RelA/p65-mediated repression of p63. Proc Natl Acad Sci U S A. 2013; 110(44):17969-74 [PubMed] Article available free on PMC after 15/04/2014 Related Publications
Squamous cell carcinoma (SCC) is highly malignant and refractory to therapy. The majority of existing mouse SCC models involve multiple gene mutations. Very few mouse models of spontaneous SCC have been generated by a single gene deletion. Here we report a haploinsufficient SCC mouse model in which exon 3 of the Tp53BP2 gene (a p53 binding protein) was deleted in one allele in a BALB/c genetic background. Tp53BP2 encodes ASPP2 (ankyrin repeats, SH3 domain and protein rich region containing protein 2). Keratinocyte differentiation induces ASPP2 and its expression is inversely correlated with p63 protein in vitro and in vivo. Up-regulation of p63 expression is required for ASPP2(Δexon3/+) BALB/c mice to develop SCC, as heterozygosity of p63 but not p53 prevents them from developing it. Mechanistically, ASPP2 inhibits ΔNp63 expression through its ability to bind IκB and enhance nuclear Rel/A p65, a component of the NF-κB transcription complex, which mediates the repression of p63. Reduced ASPP2 expression associates with tumor metastasis and increased p63 expression in human head and neck SCCs. This study identifies ASPP2 as a tumor suppressor that suppresses SCC via inflammatory signaling through NF-κB-mediated repression of p63.
Kamposioras K, Konstantara A, Kotoula V, et al. The prognostic significance of WNT pathway in surgically-treated colorectal cancer: β-catenin expression predicts for disease-free survival. Anticancer Res. 2013; 33(10):4573-84 [PubMed] Related Publications
BACKGROUND: The wingless-type MMTV integration site family of proteins (WNT) pathway is highly involved in colorectal cancer development. The aim of this study was to explore the prognostic significance and clinicopatological correlations of this pathway in a cohort of surgically-treated patients with non-metastatic colorectal cancer in relation to the site of expression of pathway proteins. MATERIALS AND METHODS: Immunohistochemical expression of nuclear cyclin D1, membranous E-cadherin and P-cadherin, membranous and nuclear β-catenin in the invasive front (IF), the tumor center (TC), as well as their mean, were assessed in 106 paraffin-embedded tissue samples. Adenomatous Polyposis Coli (APC), Axin-2 (AXIN2), cyclin-D1 (CCND1), Matrix Metalloproteinase-7 (MMP7), Secreted Frizzled Related Protein (SFRP) 1, 2 and 4 and WNT5A were evaluated by RT PCR. RESULTS: Membranous β-catenin expression was statistically reduced in the IF. Cyclin-D1 was reduced in tumors arising closer to the rectum. Reduced nuclear expression of cyclin-D1 in the IF was associated with lymphatic, venous and perineural invasion. Loss of membranous β-catenin in the TC was more common among N2 tumors. Higher SFRP4 mRNA was associated with advanced T stage. In univariate analysis, membranous expression of β-catenin in TC and IF, and their mean, was associated with longer disease-free survival (DFS). In multivariate analysis, tumor stage and mean β-catenin expression were prognostic for longer DFS (hazard ratio=0.33; p=0.01). β-Catenin expression in the IF remained significant when the mean expression was not included in the multivariate analysis (hazard ratio=0.41; p=0.028). CONCLUSION: Mean membranous expression of β-catenin, as well as that in the IF, is prognostic for longer DFS in patients with non metastatic colorectal cancer.
Scheller M, Schönheit J, Zimmermann K, et al. Cross talk between Wnt/β-catenin and Irf8 in leukemia progression and drug resistance. J Exp Med. 2013; 210(11):2239-56 [PubMed] Article available free on PMC after 21/04/2014 Related Publications
Progression and disease relapse of chronic myeloid leukemia (CML) depends on leukemia-initiating cells (LIC) that resist treatment. Using mouse genetics and a BCR-ABL model of CML, we observed cross talk between Wnt/β-catenin signaling and the interferon-regulatory factor 8 (Irf8). In normal hematopoiesis, activation of β-catenin results in up-regulation of Irf8, which in turn limits oncogenic β-catenin functions. Self-renewal and myeloproliferation become dependent on β-catenin in Irf8-deficient animals that develop a CML-like disease. Combined Irf8 deletion and constitutive β-catenin activation result in progression of CML into fatal blast crisis, elevated leukemic potential of BCR-ABL-induced LICs, and Imatinib resistance. Interestingly, activated β-catenin enhances a preexisting Irf8-deficient gene signature, identifying β-catenin as an amplifier of progression-specific gene regulation in the shift of CML to blast crisis. Collectively, our data uncover Irf8 as a roadblock for β-catenin-driven leukemia and imply both factors as targets in combinatorial therapy.
Pandurangan AK, Dharmalingam P, Sadagopan SK, et al. Luteolin induces growth arrest in colon cancer cells through involvement of Wnt/β-catenin/GSK-3β signaling. J Environ Pathol Toxicol Oncol. 2013; 32(2):131-9 [PubMed] Related Publications
Cancer is a multistep process that typically occurrs over an extended period of time, beginning with initiation followed by promotion and progression. Colon cancer is the leading cause of morbidity and mortality worldwide. For a variety of reasons, patients prefer naturally occurring dietary substances over synthetic agents to prevent cancer. Luteolin, a bioflavonoid, possesses antioxidant, anti-inflammatory, and antiproliferative effects. We analyzed the in vitro anticancer and apoptosis-inducing property of luteolin using HCT-15 colon adenocarcinoma cells. Cell viability was assessed using trypan blue assay at different concentrations. Luteolin at a concentration of 100 µM (IC50) decreased the expressions of non-P-β-catenin, phosphorylated (inactive) glycogen synthase kinase-3β, and cyclin D1 expressions in HCT-15 cells, which were confirmed by Western blot analysis. Luteolin also promoted substantial cell cycle arrest at the G2/M phase in HCT-15 cells, and it induces apoptosis in HCT-15 cells, as revealed by flow cytometric analysis. Furthermore, Western blot analysis showed that luteolin treatment enhanced the expression of Bax and caspase-3, whereas the expression of Bcl-2 was suppressed. Together, the results of this study revealed that luteolin can act as a potent inhibitor of HCT-15 proliferation and can be used as an agent against colon cancer.
Shin DH, Lee HJ, Min HY, et al. Combating resistance to anti-IGFR antibody by targeting the integrin β3-Src pathway. J Natl Cancer Inst. 2013; 105(20):1558-70 [PubMed] Article available free on PMC after 16/10/2014 Related Publications
BACKGROUND: Several phase II/III trials of anti-insulin-like growth factor 1 receptor (IGF-1R) monoclonal antibodies (mAbs) have shown limited efficacy. The mechanisms of resistance to IGF-1R mAb-based therapies and clinically applicable strategies for overcoming drug resistance are still undefined. METHODS: IGF-1R mAb cixutumumab efficacy, alone or in combination with Src inhibitors, was evaluated in 10 human head and neck squamous cell carcinoma (HNSCC) and six non-small cell lung cancer (NSCLC) cell lines in vitro in two- or three-dimensional culture systems and in vivo in cell line- or patient-derived xenograft tumors in athymic nude mice (n = 6-9 per group). Cixutumumab-induced changes in cell signaling and IGF-1 binding to integrin β3 were determined by Western or ligand blotting, immunoprecipitation, immunofluorescence, and cell adhesion analyses and enzyme-linked immunosorbent assay. Data were analyzed by the two-sided Student t test or one-way analysis of variance. RESULTS: Integrin β3-Src signaling cascade was activated by IGF-1 in HNSCC and NSCLC cells, when IGF-1 binding to IGF-1R was hampered by cixutumumab, resulting in Akt activation and cixutumumab resistance. Targeting integrin β3 or Src enhanced antitumor activity of cixutumumab in multiple cixutumumab-resistant cell lines and patient-derived tumors in vitro and in vivo. Mean tumor volume of mice cotreated with cixutumumab and integrin β3 siRNA was 133.7 mm(3) (95% confidence interval [CI] = 57.6 to 209.8 mm(3)) compared with those treated with cixutumumab (1472.5 mm(3); 95% CI = 1150.7 to 1794.3 mm(3); P < .001) or integrin β3 siRNA (903.2 mm(3); 95% CI = 636.1 to 1170.3 mm(3); P < .001) alone. CONCLUSIONS: Increased Src activation through integrin ανβ3 confers considerable resistance against anti-IGF-1R mAb-based therapies in HNSCC and NSCLC cells. Dual targeting of the IGF-1R pathway and collateral integrin β3-Src signaling module may override this resistance.
Hole PS, Zabkiewicz J, Munje C, et al. Overproduction of NOX-derived ROS in AML promotes proliferation and is associated with defective oxidative stress signaling. Blood. 2013; 122(19):3322-30 [PubMed] Related Publications
Excessive production of reactive oxygen species (ROS) is frequently observed in cancer and is known to strongly influence hematopoietic cell function. Here we report that extracellular ROS production is strongly elevated (mean >10-fold) in >60% of acute myeloid leukemia (AML) patients and that this increase is attributable to constitutive activation of nicotinamide adenine dinucleotide phosphate oxidases (NOX). In contrast, overproduction of mitochondrial ROS was rarely observed. Elevated ROS was found to be associated with lowered glutathione levels and depletion of antioxidant defense proteins. We also show for the first time that the levels of ROS generated were able to strongly promote the proliferation of AML cell lines, primary AML blasts, and, to a lesser extent, normal CD34(+) cells, and that the response to ROS is limited by the activation of the oxidative stress pathway mediated though p38(MAPK). Consistent with this, we observed that p38(MAPK) responses were attenuated in patients expressing high levels of ROS. These data show that overproduction of NOX-derived ROS can promote the proliferation of AML blasts and that they also develop mechanisms to suppress the stress signaling that would normally limit this response. Together these adaptations would be predicted to confer a competitive advantage to the leukemic clone.
Li D, Jin L, Alesi GN, et al. The prometastatic ribosomal S6 kinase 2-cAMP response element-binding protein (RSK2-CREB) signaling pathway up-regulates the actin-binding protein fascin-1 to promote tumor metastasis. J Biol Chem. 2013; 288(45):32528-38 [PubMed] Article available free on PMC after 08/11/2014 Related Publications
Metastasis is the leading cause of death in patients with breast, lung, and head and neck cancers. However, the molecular mechanisms underlying metastases in these cancers remain unclear. We found that the p90 ribosomal S6 kinase 2 (RSK2)-cAMP response element-binding protein (CREB) pathway is commonly activated in diverse metastatic human cancer cells, leading to up-regulation of a CREB transcription target Fascin-1. We also observed that the protein expression patterns of RSK2 and Fascin-1 correlate in primary human tumor tissue samples from head and neck squamous cell carcinoma patients. Moreover, knockdown of RSK2 disrupts filopodia formation and bundling in highly invasive cancer cells, leading to attenuated cancer cell invasion in vitro and tumor metastasis in vivo, whereas expression of Fascin-1 significantly rescues these phenotypes. Furthermore, targeting RSK2 with the small molecule RSK inhibitor FMK-MEA effectively attenuated the invasive and metastatic potential of cancer cells in vitro and in vivo, respectively. Taken together, our findings for the first time link RSK2-CREB signaling to filopodia formation and bundling through the up-regulation of Fascin-1, providing a proinvasive and prometastatic advantage to human cancers. Therefore, protein effectors of the RSK2-CREB-Fascin-1 pathway represent promising biomarkers and therapeutic targets in the clinical prognosis and treatment of metastatic human cancers.
Ono M, Yin P, Navarro A, et al. Paracrine activation of WNT/β-catenin pathway in uterine leiomyoma stem cells promotes tumor growth. Proc Natl Acad Sci U S A. 2013; 110(42):17053-8 [PubMed] Article available free on PMC after 08/11/2014 Related Publications
Uterine leiomyomas are extremely common estrogen and progesterone-dependent tumors of the myometrium and cause irregular uterine bleeding, severe anemia, and recurrent pregnancy loss in 15-30% of reproductive-age women. Each leiomyoma is thought to arise from a single mutated myometrial smooth muscle stem cell. Leiomyoma side-population (LMSP) cells comprising 1% of all tumor cells and displaying tumor-initiating stem cell characteristics are essential for estrogen- and progesterone-dependent in vivo growth of tumors, although they have remarkably lower estrogen/progesterone receptor levels than mature myometrial or leiomyoma cells. However, how estrogen/progesterone regulates the growth of LMSP cells via mature neighboring cells is unknown. Here, we demonstrate a critical paracrine role of the wingless-type (WNT)/β-catenin pathway in estrogen/progesterone-dependent tumorigenesis, involving LMSP and differentiated myometrial or leiomyoma cells. Estrogen/progesterone treatment of mature myometrial cells induced expression of WNT11 and WNT16, which remained constitutively elevated in leiomyoma tissues. In LMSP cells cocultured with mature myometrial cells, estrogen-progesterone selectively induced nuclear translocation of β-catenin and induced transcriptional activity of its heterodimeric partner T-cell factor and their target gene AXIN2, leading to the proliferation of LMSP cells. This effect could be blocked by a WNT antagonist. Ectopic expression of inhibitor of β-catenin and T-cell factor 4 in LMSP cells, but not in mature leiomyoma cells, blocked the estrogen/progesterone-dependent growth of human tumors in vivo. We uncovered a paracrine role of the WNT/β-catenin pathway that enables mature myometrial or leiomyoma cells to send mitogenic signals to neighboring tissue stem cells in response to estrogen and progesterone, leading to the growth of uterine leiomyomas.
Gupta SC, Francis SK, Nair MS, et al. Azadirone, a limonoid tetranortriterpene, induces death receptors and sensitizes human cancer cells to tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) through a p53 protein-independent mechanism: evidence for the role of the ROS-ERK-CHOP-death receptor pathway. J Biol Chem. 2013; 288(45):32343-56 [PubMed] Article available free on PMC after 08/11/2014 Related Publications
Although tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) has shown efficacy in a phase 2 clinical trial, development of resistance to TRAIL by tumor cells is a major roadblock. We investigated whether azadirone, a limonoidal tetranortriterpene, can sensitize human tumor cells to TRAIL. Results indicate that azadirone sensitized cancer cells to TRAIL. The limonoid induced expression of death receptor (DR) 5 and DR4 but did not affect expression of decoy receptors in cancer cells. The induction of DRs was mediated through activation of ERK and through up-regulation of a transcription factor CCAAT enhancer-binding protein homologous protein (CHOP) as silencing of these signaling molecules abrogated the effect of azadirone. These effects of azadirone were cancer cell-specific. The CHOP binding site on the DR5 gene was required for induction of DR5 by azadirone. Up-regulation of DRs was mediated through the generation of reactive oxygen species (ROS) as ROS scavengers reduced the effect of azadirone on ERK activation, CHOP up-regulation, DR induction, and TRAIL sensitization. The induction of DRs by this limonoid was independent of p53, but sensitization to TRAIL was p53-dependent. The limonoid down-regulated the expression of cell survival proteins and up-regulated the proapoptotic proteins. The combination of azadirone with TRAIL was found to be additive at concentrations lower than IC50, whereas at higher concentrations, the combination was synergistic. Overall, this study indicates that azadirone can sensitize cancer cells to TRAIL through ROS-ERK-CHOP-mediated up-regulation of DR5 and DR4 signaling, down-regulation of cell survival proteins, and up-regulation of proapoptotic proteins.
Munari E, Fujita K, Faraj S, et al. Dysregulation of mammalian target of rapamycin pathway in upper tract urothelial carcinoma. Hum Pathol. 2013; 44(12):2668-76 [PubMed] Related Publications
Upper tract urothelial carcinoma (UTUC) accounts for 5% to 10% of all urothelial carcinomas. Despite many shared features, key clinical and molecular genetic differences between upper tract and bladder urothelial carcinomas are becoming apparent. We have previously demonstrated alterations of mammalian target of rapamycin (mTOR) pathway in bladder carcinoma with a potential impact on biological behavior. In the current study, we evaluated the expression status and prognostic significance of mTOR pathway members in UTUC. Archival formalin-fixed and paraffin-embedded tissues from 99 primary UTUCs were retrieved from one of the authors' institution. Tissue microarrays were constructed with triplicate tumor samples and paired nonneoplastic urothelium. Tissue microarrays were analyzed using immunohistochemistry for mTOR pathway members: PTEN, phos-AKT, phos-mTOR, phos-S6, phos-4EBP1, and related markers p27 and c-MYC; correlation with clinicopathologic parameters and outcome was performed. We found significantly lower expression of PTEN, phos-AKT, phos-mTOR, phos-S6, phos-4EBP1, p27, and c-MYC in UTUC compared with paired benign urothelium (P < .0005). We found a strong positive correlation between PTEN and phos-AKT. Moderate correlation was observed between phos-mTOR and phos-S6, PTEN and p27, phos-AKT and p27, phos-S6 and p27, phos-mTOR and c-MYC, phos-S6 and c-MYC, and p27 and c-MYC. None of the evaluated biomarkers were associated with increased hazard ratios for tumor recurrence or for cancer-specific mortality, when adjusting for relevant clinicopathologic variables. Dysregulation of the mTOR pathway was observed in UTUC compared with normal urothelium, implicating a potential pathogenic role in tumor development. In our cohort, expression of the evaluated biomarkers had no prognostic value.
He M, Dong C, Ren R, et al. Radiation enhances the invasiveness of irradiated and nonirradiated bystander hepatoma cells through a VEGF-MMP2 pathway initiated by p53. Radiat Res. 2013; 180(4):389-97 [PubMed] Related Publications
Recent evidence has shown that irradiation can promote the invasiveness of hepatocellular carcinoma cells and have an impact on the invasive behavior of nonirradiated surrounding cancer cells, which may enhance overall tumor aggressiveness. However, the role of the TP53 tumor suppressor gene in the invasion of irradiated hepatoma cells and their nonirradiated bystanders remain largely unknown. In the present study, we found that irradiation increased the invasiveness of human hepatoma HepG2 cells, and pretreatment of the cells with SU1498 (an inhibitor of vascular endothelial growth factor receptor 2, VEGFR2) and GM6001 (an inhibitor of matrix metalloproteinases 2, MMP2) demonstrated that radiation-enhanced invasiveness is associated with the interplay between MMP2 and VEGF signaling. In addition, while radiation-induced expression and phosphorylation of p53, inhibition of p53 function with pifithrin-α or transfection of cells with p53 siRNA significantly reduced the activation of both MMP2 and VEGF and resulted in a reduction of radiation-induced invasiveness. Interestingly, we also found that the invasiveness of the nonirradiated bystander cells was also elevated after co-culturing with irradiated cells and that bystander invasive potential was regulated paracrine in a manner by MMP2 and VEGF from the irradiated cells through a p53-dependent mechanism. Taken together, our data demonstrate that radiation-induced up-regulation of p53 is responsible for the promotion of VEGF-MMP2 pathway involved in the enhancement of invasiveness of both irradiated and bystander hepatoma cells.
Pawlikowski JS, McBryan T, van Tuyn J, et al. Wnt signaling potentiates nevogenesis. Proc Natl Acad Sci U S A. 2013; 110(40):16009-14 [PubMed] Article available free on PMC after 01/04/2014 Related Publications
Cellular senescence is a stable proliferation arrest associated with an altered secretory pathway (senescence-associated secretory phenotype). Cellular senescence is also a tumor suppressor mechanism, to which both proliferation arrest and senescence-associated secretory phenotype are thought to contribute. The melanocytes within benign human nevi are a paradigm for tumor-suppressive senescent cells in a premalignant neoplasm. Here a comparison of proliferating and senescent melanocytes and melanoma cell lines by RNA sequencing emphasizes the importance of senescence-associated proliferation arrest in suppression of transformation. Previous studies showed that activation of the Wnt signaling pathway can delay or bypass senescence. Consistent with this, we present evidence that repression of Wnt signaling contributes to melanocyte senescence in vitro. Surprisingly, Wnt signaling is active in many senescent human melanocytes in nevi, and this is linked to histological indicators of higher proliferative and malignant potential. In a mouse, activated Wnt signaling delays senescence-associated proliferation arrest to expand the population of senescent oncogene-expressing melanocytes. These results suggest that Wnt signaling can potentiate nevogenesis in vivo by delaying senescence. Further, we suggest that activated Wnt signaling in human nevi undermines senescence-mediated tumor suppression and enhances the probability of malignancy.
Alam M, Ahmad R, Rajabi H, et al. MUC1-C oncoprotein activates ERK→C/EBPβ signaling and induction of aldehyde dehydrogenase 1A1 in breast cancer cells. J Biol Chem. 2013; 288(43):30892-903 [PubMed] Article available free on PMC after 25/10/2014 Related Publications
Aldehyde dehydrogenase 1A1 (ALDH1A1) activity is used as a marker of breast cancer stem cells; however, little is known about the regulation of ALDH1A1 expression. Mucin 1 (MUC1) is a heterodimeric protein that is aberrantly overexpressed in most human breast cancers. In studies of breast cancer cells stably silenced for MUC1 or overexpressing the oncogenic MUC1-C subunit, we demonstrate that MUC1-C is sufficient for induction of MEK → ERK signaling and that treatment with a MUC1-C inhibitor suppresses ERK activation. In turn, MUC1-C induces ERK-mediated phosphorylation and activation of the CCAAT/enhancer-binding protein β (C/EBPβ) transcription factor. The results further show that MUC1-C and C/EBPβ form a complex on the ALDH1A1 gene promoter and activate ALDH1A1 gene transcription. MUC1-C-induced up-regulation of ALDH1A1 expression is associated with increases in ALDH activity and is detectable in stem-like cells when expanded as mammospheres. These findings demonstrate that MUC1-C (i) activates a previously unrecognized ERK→C/EBPβ→ALDH1A1 pathway, and (ii) promotes the induction of ALDH activity in breast cancer cells.
Fox SA, Richards AK, Kusumah I, et al. Expression profile and function of Wnt signaling mechanisms in malignant mesothelioma cells. Biochem Biophys Res Commun. 2013; 440(1):82-7 [PubMed] Related Publications
Malignant mesothelioma (MM) is an uncommon and particularly aggressive cancer associated with asbestos exposure, which currently presents an intractable clinical challenge. Wnt signaling has been reported to play a role in the neoplastic properties of mesothelioma cells but has not been investigated in detail in this cancer. We surveyed expression of Wnts, their receptors, and other key molecules in this pathway in well established in vitro mesothelioma models in comparison with primary mesothelial cultures. We also tested the biological response of MM cell lines to exogenous Wnt and secreted regulators, as well as targeting β-catenin. We detected frequent expression of Wnt3 and Wnt5a, as well as Fzd 2, 4 and 6. The mRNA of Wnt4, Fzd3, sFRP4, APC and axin2 were downregulated in MM relative to mesothelial cells while LEF1 was overexpressed in MM. Functionally, we observed that Wnt3a stimulated MM proliferation while sFRP4 was inhibitory. Furthermore, directly targeting β-catenin expression could sensitise MM cells to cytotoxic drugs. These results provide evidence for altered expression of a number of Wnt/Fzd signaling molecules in MM. Modulation of Wnt signaling in MM may prove a means of targeting proliferation and drug resistance in this cancer.
Hao J, Zhang Y, Jing D, et al. Role of Hippo signaling in cancer stem cells. J Cell Physiol. 2014; 229(3):266-70 [PubMed] Related Publications
Cancer stem cells (CSCs) have been proposed and evidenced as the initiator of tumor formation and the seeds of metastases. Thereby, the molecular mechanisms regarding modulation of CSCs have been widely explored, aimed to improve treatment for cancer patients. Recent progress has highlighted the effects of Hippo signaling in tumorigenesis and cancer development, including its crucial role in CSC regulation. Although the kernel Hippo signaling cascade has been well studied, its upstream inputs and downstream transcriptional regulation still remain elusive. In this review, we summarize the current understanding of the mechanism and regulatory function of Hippo signaling in CSCs, with emphasis on its possible roles in regulation of CSC self-renewal, differentiation and tumorigenesis.
Li Z, Min W, Gou J Knockdown of cyclophilin A reverses paclitaxel resistance in human endometrial cancer cells via suppression of MAPK kinase pathways. Cancer Chemother Pharmacol. 2013; 72(5):1001-11 [PubMed] Related Publications
PURPOSE: Paclitaxel resistance remains to be a major obstacle to the chemotherapy of endometrial cancer. Using proteomic-based approach, we used to identify cyclophilin A (CypA) as a potential therapeutic target for endometrial cancer. As a natural continuation, this study aimed to reveal the correlation between CypA and paclitaxel resistance and evaluate the possibility of CypA as a therapeutic target for reversal of resistance. METHODS: Two paclitaxel-resistant endometrial cancer cell sublines HEC-1-B/TAX and AN3CA/TAX were generated, and expressions of CypA, P-gp, MRP-2 and survivin were demonstrated by Western blotting. CypA was knocked down by RNA interference, and the subsequent effects on the alteration of paclitaxel resistance were examined by MTT, flow cytometry and migratory/invasive transwell assays. MAPK kinases activities were examined by Western blotting. RESULTS: CypA knockdown led to significant inhibition of cell proliferation, induction of apoptosis and suppression of migratory/invasive capacity in HEC-1-B/TAX and AN3CA/TAX cells when exposed to paclitaxel. CypA knockdown led to reductions in total and phosphorylated MAPK kinases, including Akt, ERK1/2, p38 MAPK and JNK, in HEC-1-B/TAX cells. Furthermore, pretreatment with MAPK kinase inhibitors exhibited a synergistic effect in combination with CypA knockdown. CONCLUSIONS: These results demonstrated that CypA expression was up-regulated in paclitaxel-resistant cancer cells, and knockdown of CypA could reverse the paclitaxel resistance through, at least partly, suppression of MAPK kinase pathways, presenting a possibility of CypA serving as a therapeutic target to overcome paclitaxel resistance.
Tam WL, Lu H, Buikhuisen J, et al. Protein kinase C α is a central signaling node and therapeutic target for breast cancer stem cells. Cancer Cell. 2013; 24(3):347-64 [PubMed] Related Publications
The epithelial-mesenchymal transition program becomes activated during malignant progression and can enrich for cancer stem cells (CSCs). We report that inhibition of protein kinase C α (PKCα) specifically targets CSCs but has little effect on non-CSCs. The formation of CSCs from non-stem cells involves a shift from EGFR to PDGFR signaling and results in the PKCα-dependent activation of FRA1. We identified an AP-1 molecular switch in which c-FOS and FRA1 are preferentially utilized in non-CSCs and CSCs, respectively. PKCα and FRA1 expression is associated with the aggressive triple-negative breast cancers, and the depletion of FRA1 results in a mesenchymal-epithelial transition. Hence, identifying molecular features that shift between cell states can be exploited to target signaling components critical to CSCs.
Ghosh S, Dutta K, Basu A Chandipura virus induces neuronal death through Fas-mediated extrinsic apoptotic pathway. J Virol. 2013; 87(22):12398-406 [PubMed] Article available free on PMC after 01/05/2014 Related Publications
Chandipura virus (CHPV; genus Vesiculovirus, family Rhabdoviridae) is an emerging tropical pathogen with a case fatality rate of 55 to 75% that predominantly affects children in the age group of 2 to 16 years. Although it has been established as a neurotropic virus causing encephalitis, the molecular pathology leading to neuronal death is unknown. The present study elucidates for the first time the mechanism of cell death in neurons after CHPV infection that answers the basic cause of CHPV-mediated neurodegeneration. Through various cell death assays in vitro and in vivo, a relationship between viral replication within neuron and neuronal apoptosis has been established. We report that expression of CHPV phosphoprotein increases up to 6 h postinfection and diminishes thereafter in neuronal cell lines, signifying the replicative phase of CHPV. Various analyses conducted during the investigation established that CHPV-infected neurons are undergoing apoptosis through an extrinsic pathway mediated through the Fas-associated death domain (FADD) following activation of caspase-8 and -3 and prominent cleavage of poly(ADP-ribose) polymerase (PARP). Knocking down the expression of caspase-3, the final executioner of apoptosis, in a neuronal cell line by endoribonuclease-prepared small interfering RNA (siRNA) validated its pivotal role in CHPV-mediated neurodegeneration by showing reduction in apoptosis after CHPV infection.
Hidaka Y, Mitomi H, Saito T, et al. Alteration in the Wnt/β-catenin signaling pathway in gastric neoplasias of fundic gland (chief cell predominant) type. Hum Pathol. 2013; 44(11):2438-48 [PubMed] Related Publications
Gastric neoplasia of chief cell-predominant type (GN-CCP) has been reported as a new, rare variant of gastric tumor. GN-CCPs were defined as tumors consisting of irregular anastomosing glands of columnar cells mimicking chief cells of fundic gland with nuclear atypia and prolapse-type submucosal involvement. We comparatively evaluated clinicopathologic features between 31 GN-CCPs and 130 cases of conventional gastric adenocarcinoma invading into submucosa (CGA-SM) in addition to nuclear β-catenin immunolabeling and direct sequencing of members of the Wnt/β-catenin pathway, CTNNB1, APC, and AXIN, in a subset of these tumors. GN-CCP presented as small protruded lesions located in the upper third of the stomach, with minimal involvement into the submucosa and rare lymphovascular invasion. None of the lesions have demonstrated a recurrence of disease or metastasis on follow-up. Nuclear β-catenin immunolabeling was higher in GN-CCP (labeling index [LI]: median, 19.3%; high expresser [LI >30%], 7/27 cases [26%]) than CGA-SM (median LI, 14.7%; high expresser, 1/19 cases [6%]). Missense mutation of APC was observed in 1 GN-CCP but not CGA-SM. Missense or nonsense mutations of CTNNB1 and AXIN1 were higher in GN-CCPs (14.8%, both) than CGA-SMs (5.3%, both). Missense mutations of AXIN2 were higher in GN-CCPs (25.9%) than in CGA-SMs (10.5%). Overall, 14 (51.9%) of 27 GN-CCPs and 5 (26.3%) of 19 CGA-SM cases harbored at least 1 of these gene mutations. In conclusion, GN-CCPs as a unique variant of nonaggressive tumor are characterized by nuclear β-catenin accumulation and mutation of CTNNB1 or AXIN gene, suggesting activation of the Wnt/β-catenin pathway.
Sheppard KE, Cullinane C, Hannan KM, et al. Synergistic inhibition of ovarian cancer cell growth by combining selective PI3K/mTOR and RAS/ERK pathway inhibitors. Eur J Cancer. 2013; 49(18):3936-44 [PubMed] Related Publications
BACKGROUND: Ovarian cancer is the major cause of death from gynaecological malignancy with a 5year survival of only ∼30% due to resistance to platinum and paclitaxel-based first line therapy. Dysregulation of the phosphoinositide 3-kinase/mammalian target of rapamycin (PI3K/mTOR) and RAS/extracellular signal-regulated kinase (ERK) pathways is common in ovarian cancer, providing potential new targets for 2nd line therapy. METHODS: We determined the inhibition of proliferation of an extensive panel of ovarian cancer cell lines, encompassing all the major histotypes, by the dual PI3K/mTOR inhibitor PF-04691502 and a MEK inhibitor, PD-0325901. In addition, we analysed global gene expression, mutation status of key PI3K/mTOR and RAS/ERK pathway members and pathway activation to identify predictors of drug response. RESULTS: PF-04691502 inhibits proliferation of the majority of cell lines with potencies that correlate with the extent of pathway inhibition. Resistant cell lines were characterised by activation of the RAS/ERK pathway as indicated by differential gene expression profiles and pathway activity analysis. PD-0325901 suppressed growth of a subset of cell lines that were characterised by high basal RAS/ERK signalling. Strikingly, using PF-04691502 and PD-0325901 in combination resulted in synergistic growth inhibition in 5/6 of PF-04691502 resistant cell lines and two cell lines resistant to both single agents showed robust synergistic growth arrest. Xenograft studies confirm the utility of combination therapy to synergistically inhibit tumour growth of PF-04691502-resistant tumours in vivo. CONCLUSIONS: These studies identify dual targeted inhibitors of PI3K/mTOR in combination with inhibitors of RAS/ERK signalling as a potentially effective new approach to treating ovarian cancer.
Merchant JL, Saqui-Salces M Inhibition of Hedgehog signaling in the gastrointestinal tract: targeting the cancer microenvironment. Cancer Treat Rev. 2014; 40(1):12-21 [PubMed] Article available free on PMC after 01/02/2015 Related Publications
This review summarizes emerging information regarding the Hedgehog (Hh) signaling pathway during neoplastic transformation in the gastrointestinal tract. Although there is a role for the well-established canonical pathway in which Hedgehog ligands interact with their receptor Patched, there is sufficient evidence that downstream components of the Hh pathway, e.g., Gli1, are hijacked by non-Hh signaling pathways to promote the conversion of the epithelium to dysplasia and carcinoma. We review the canonical pathway and involvement of primary cilia, and then focus on current evidence for Hh signaling in luminal bowel cancers as well as accessory organs, i.e., liver, pancreas and biliary ducts. We conclude that targeting the Hh pathway with small molecules, nutriceuticals and other mechanisms will likely require a combination of inhibitors that target Gli transcription factors in addition to canonical modulators such as Smoothened.
Ni TK, Landrette SF, Bjornson RD, et al. Low-copy piggyBac transposon mutagenesis in mice identifies genes driving melanoma. Proc Natl Acad Sci U S A. 2013; 110(38):E3640-9 [PubMed] Article available free on PMC after 17/03/2014 Related Publications
Despite considerable efforts to sequence hypermutated cancers such as melanoma, distinguishing cancer-driving genes from thousands of recurrently mutated genes remains a significant challenge. To circumvent the problematic background mutation rates and identify new melanoma driver genes, we carried out a low-copy piggyBac transposon mutagenesis screen in mice. We induced eleven melanomas with mutation burdens that were 100-fold lower relative to human melanomas. Thirty-eight implicated genes, including two known drivers of human melanoma, were classified into three groups based on high, low, or background-level mutation frequencies in human melanomas, and we further explored the functional significance of genes in each group. For two genes overlooked by prevailing discovery methods, we found that loss of membrane associated guanylate kinase, WW and PDZ domain containing 2 and protein tyrosine phosphatase, receptor type, O cooperated with the v-raf murine sarcoma viral oncogene homolog B (BRAF) recurrent V600E mutation to promote cellular transformation. Moreover, for infrequently mutated genes often disregarded by current methods, we discovered recurrent mitogen-activated protein kinase kinase kinase 1 (Map3k1)-activating insertions in our screen, mirroring recurrent MAP3K1 up-regulation in human melanomas. Aberrant expression of Map3k1 enabled growth factor-autonomous proliferation and drove BRAF-independent ERK signaling, thus shedding light on alternative means of activating this prominent signaling pathway in melanoma. In summary, our study contributes several previously undescribed genes involved in melanoma and establishes an important proof-of-principle for the utility of the low-copy transposon mutagenesis approach for identifying cancer-driving genes, especially those masked by hypermutation.