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Signal Transduction

"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)

An overview of major signal transduction pathways
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)

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Web Resources: Signal Transduction and Cancer
Latest Research Publications

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Latest Research Publications

This list of publications is regularly updated (Source: PubMed).

Menendez JA, Schroeder B, Peirce SK, et al.
Blockade of a key region in the extracellular domain inhibits HER2 dimerization and signaling.
J Natl Cancer Inst. 2015; 107(6):djv090 [PubMed] Related Publications
BACKGROUND: Several treatment strategies target the human epidermal growth factor receptor 2 (HER2) in breast carcinomas, including monoclonal antibodies directed against HER2's extracellular domain (ECD) and small molecule inhibitors of its tyrosine kinase activity. Yet, novel therapies are needed that prevent HER2 dimerization with other HER family members, because current treatments are only partially effective.
METHODS: To test the hypothesis that HER2 activation requires a protein sequence in the HER2-ECD that mediates HER2 homo- and heterodimerization, we introduced a series of deletion mutations in the third subdomain of HER2-ECD. These deletion mutants were retrovirally expressed in breast cancer (BC) cells that naturally overexpress HER2 and in noncancerous, HER2-negative breast epithelial cells. One-factor analysis of variance or Student's t test were used to analyze differences. All statistical tests were two-sided.
RESULTS: The smallest deletion in the ECD domain of HER2, which removed only 16 amino acids (HER2-ECDΔ451-466), completely disrupted the oncogenic potential of HER2. In contrast to wild-type HER2, the mutant-inhibited anchorage-independent growth (mean number of colonies: mutant, 70, 95% confidence interval [CI] = 55 to 85; wild-type, 400, 95% CI = 320 to 480, P < .001) increased sensitivity to paclitaxel treatment in both transformed and nontransformed cells. Overexpression of HER2Δ451-466 efficiently inhibited activation of HER1, HER2, and HER3 in all cell lines tested.
CONCLUSIONS: These findings reveal that an essential "activating" sequence exists in the extracellular domain of HER2. Disruption of this sequence disables the HER2 dimerization loop, blocks subsequent activation of HER2-driven oncogenic signaling, and generates a dominant-negative form of HER2. Reagents specifically against this molecular activation switch may represent a novel targeted approach for the management of HER2-overexpressing carcinomas.

Zhang MZ, Ferrigno O, Wang Z, et al.
TGIF governs a feed-forward network that empowers Wnt signaling to drive mammary tumorigenesis.
Cancer Cell. 2015; 27(4):547-60 [PubMed] Article available free on PMC after 13/04/2016 Related Publications
Many types of human cancers having hyperactivated Wnt signaling display no causative alterations in known effectors of this pathway. Here, we report a function of TGIF in Wnt signaling. TGIF associates with and diverts Axin1 and Axin2 from the β-catenin destruction complex, therefore allowing β-catenin accrual. Intriguingly, activation of Wnt signaling induces the expression of TGIF, which unveils a feed-forward loop that ensures effective integration of Wnt signaling. In triple-negative breast cancers (TNBC), elevated levels of TGIF correlate with high Wnt signaling and poor survival of patients. Moreover, genetic experiments revealed that Tgif1 ablation impeded mammary tumor development in MMTV-Wnt1 mice, further underscoring a requirement of TGIF for oncogenic Wnt signaling.

Andrikopoulou M, Salakos N, Deligeoroglou E, et al.
The role of mTOR signaling pathway in premalignant and malignant cervical lesions.
Eur J Gynaecol Oncol. 2015; 36(1):36-43 [PubMed] Related Publications
PURPOSE OF THE STUDY: Aberrant activation of the Akt/mTOR/pS6 signaling pathway has been identified in various types of cancer and is under investigation in cervical cancer. The purpose of this study was to assess the expression of the phosphorylated/activated forms of Akt (upstream molecule), 4E-BP1 and pS6 (downstream molecules) in biopsy samples of cervical low grade squamous intraepithelial lesions (LSIL), high grade squamous intraepithelial lesions (HSIL), and squamous cell carcinoma (Ca) compared to normal cervical epithelium.
MATERIAL AND METHODS: The study included 38 cases diagnosed as LSIL, 31 cases as HSIL, 29 cases as Ca, and eight control cases from normal cervix. Immunohistochemistry was used to assess the expression of pAkt, p4E-BP1 and pS6.
RESULTS: Statistical analysis revealed significant differences between HSIL and Ca groups compared to controls regarding intensity, positivity, and total scores for all three molecules (p < 0.001). A trend for higher expression with increasing grade of dysplasia was demonstrated.
CONCLUSION: These results strongly support the view that the mTOR signaling pathway is involved in cervical carcinogenesis.

Pérez-Gómez E, Andradas C, Blasco-Benito S, et al.
Role of cannabinoid receptor CB2 in HER2 pro-oncogenic signaling in breast cancer.
J Natl Cancer Inst. 2015; 107(6):djv077 [PubMed] Related Publications
BACKGROUND: Pharmacological activation of cannabinoid receptors elicits antitumoral responses in different cancer models. However, the biological role of these receptors in tumor physio-pathology is still unknown.
METHODS: We analyzed CB2 cannabinoid receptor protein expression in two series of 166 and 483 breast tumor samples operated in the University Hospitals of Kiel, Tübingen, and Freiburg between 1997 and 2010 and CB2 mRNA expression in previously published DNA microarray datasets. The role of CB2 in oncogenesis was studied by generating a mouse line that expresses the human V-Erb-B2 Avian Erythroblastic Leukemia Viral Oncogene Homolog 2 (HER2) rat ortholog (neu) and lacks CB2 and by a variety of biochemical and cell biology approaches in human breast cancer cells in culture and in vivo, upon modulation of CB2 expression by si/shRNAs and overexpression plasmids. CB2-HER2 molecular interaction was studied by colocalization, coimmunoprecipitation, and proximity ligation assays. Statistical tests were two-sided.
RESULTS: We show an association between elevated CB2 expression in HER2+ breast tumors and poor patient prognosis (decreased overall survival, hazard ratio [HR] = 0.29, 95% confidence interval [CI] = 0.09 to 0.71, P = .009) and higher probability to suffer local recurrence (HR = 0.09, 95% CI = 0.049 to 0.54, P = .003) and to develop distant metastases (HR = 0.33, 95% CI = 0.13 to 0.75, P = .009). We also demonstrate that genetic inactivation of CB2 impairs tumor generation and progression in MMTV-neu mice. Moreover, we show that HER2 upregulates CB2 expression by activating the transcription factor ELK1 via the ERK cascade and that an increased CB2 expression activates the HER2 pro-oncogenic signaling at the level of the tyrosine kinase c-SRC. Finally, we show HER2 and CB2 form heteromers in cancer cells.
CONCLUSIONS: Our findings reveal an unprecedented role of CB2 as a pivotal regulator of HER2 pro-oncogenic signaling in breast cancer, and they suggest that CB2 may be a biomarker with prognostic value in these tumors.

Furnari FB, Cloughesy TF, Cavenee WK, Mischel PS
Heterogeneity of epidermal growth factor receptor signalling networks in glioblastoma.
Nat Rev Cancer. 2015; 15(5):302-10 [PubMed] Related Publications
As tumours evolve, the daughter cells of the initiating cell often become molecularly heterogeneous and develop different functional properties and therapeutic vulnerabilities. In glioblastoma (GBM), a lethal form of brain cancer, the heterogeneous expression of the epidermal growth factor receptor (EGFR) poses a substantial challenge for the effective use of EGFR-targeted therapies. Understanding the mechanisms that cause EGFR heterogeneity in GBM should provide better insights into how they, and possibly other amplified receptor tyrosine kinases, affect cellular signalling, metabolism and drug resistance.

Zhang L, Zhou Y, Cheng C, et al.
Genomic analyses reveal mutational signatures and frequently altered genes in esophageal squamous cell carcinoma.
Am J Hum Genet. 2015; 96(4):597-611 [PubMed] Article available free on PMC after 02/10/2015 Related Publications
Esophageal squamous cell carcinoma (ESCC) is one of the most common cancers worldwide and the fourth most lethal cancer in China. However, although genomic studies have identified some mutations associated with ESCC, we know little of the mutational processes responsible. To identify genome-wide mutational signatures, we performed either whole-genome sequencing (WGS) or whole-exome sequencing (WES) on 104 ESCC individuals and combined our data with those of 88 previously reported samples. An APOBEC-mediated mutational signature in 47% of 192 tumors suggests that APOBEC-catalyzed deamination provides a source of DNA damage in ESCC. Moreover, PIK3CA hotspot mutations (c.1624G>A [p.Glu542Lys] and c.1633G>A [p.Glu545Lys]) were enriched in APOBEC-signature tumors, and no smoking-associated signature was observed in ESCC. In the samples analyzed by WGS, we identified focal (<100 kb) amplifications of CBX4 and CBX8. In our combined cohort, we identified frequent inactivating mutations in AJUBA, ZNF750, and PTCH1 and the chromatin-remodeling genes CREBBP and BAP1, in addition to known mutations. Functional analyses suggest roles for several genes (CBX4, CBX8, AJUBA, and ZNF750) in ESCC. Notably, high activity of hedgehog signaling and the PI3K pathway in approximately 60% of 104 ESCC tumors indicates that therapies targeting these pathways might be particularly promising strategies for ESCC. Collectively, our data provide comprehensive insights into the mutational signatures of ESCC and identify markers for early diagnosis and potential therapeutic targets.

Sharma P, Allison JP
The future of immune checkpoint therapy.
Science. 2015; 348(6230):56-61 [PubMed] Related Publications
Immune checkpoint therapy, which targets regulatory pathways in T cells to enhance antitumor immune responses, has led to important clinical advances and provided a new weapon against cancer. This therapy has elicited durable clinical responses and, in a fraction of patients, long-term remissions where patients exhibit no clinical signs of cancer for many years. The way forward for this class of novel agents lies in our ability to understand human immune responses in the tumor microenvironment. This will provide valuable information regarding the dynamic nature of the immune response and regulation of additional pathways that will need to be targeted through combination therapies to provide survival benefit for greater numbers of patients.

François CM, Wargnier R, Petit F, et al.
17β-estradiol inhibits spreading of metastatic cells from granulosa cell tumors through a non-genomic mechanism involving GPER1.
Carcinogenesis. 2015; 36(5):564-73 [PubMed] Article available free on PMC after 01/05/2016 Related Publications
Granulosa cell tumor (GCT) is a rare and severe form of sex-cord stromal ovarian tumor that is characterized by its long natural history and tendency to recur years after surgical ablation. Because there is no efficient curative treatment beyond surgery, ~20% of patients die of the consequences of their tumor. However, very little is known of the molecular etiology of this pathology. About 70% of GCT patients present with elevated circulating estradiol (E2). Because this hormone is known to increase tumor growth and progression in a number of cancers, we investigated the possible role of E2 in GCTs. Cell-based studies with human GCT metastases and primary tumor-derived cells, ie KGN and COV434 cells, respectively, aimed at evaluating E2 effect on cell growth, migration and invasion. Importantly, we found that E2 did not affect GCT cell growth, but that it significantly decreased the migration and matrix invasion of metastatic GCT cells. Noteworthy, our molecular studies revealed that this effect was accompanied by the inhibition through non-genomic mechanisms of extracellular signal-regulated kinase 1/2 (ERK1/2), which is constitutively activated in GCTs. By using pharmacological and RNA silencing approaches, we found that E2 action was mediated by G protein-coupled estrogen receptor 1 (GPER1) signaling pathway. Analyses of GPER1 expression on tissue microarrays from human GCTs confirmed its expression in ~90% of GCTs. Overall, our study reveals that E2 would act via non-classical pathways to prevent metastasis spreading in GCTs and also reveals GPER1 as a possible target in this disease.

Das S, Martinez LR, Ray S
Phospholipid remodeling and eicosanoid signaling in colon cancer cells.
Indian J Biochem Biophys. 2014; 51(6):512-9 [PubMed] Article available free on PMC after 01/05/2016 Related Publications
Phospholipid remodeling and eicosanoid synthesis are central to lipid-based inflammatory reactions. Studies have revealed that membrane phospholipid remodeling by fatty acids through deacylation/reacylation reactions increases the risk of colorectal cancers (CRC) by allowing the cells to produce excess inflammatory eicosanoids, such as prostaglandins, thromboxanes and leukotrienes. Over the years, efforts have been made to understand the lipid remodeling pathways and to design anti-cancer drugs targeting the enzymes of eicosanoid biosynthesis. Here, we discuss the recent progress in phospholipid remodeling and eicosanoid biosynthesis in CRC.

Ray A, Alalem M, Ray BK
Insulin signaling network in cancer.
Indian J Biochem Biophys. 2014; 51(6):493-8 [PubMed] Related Publications
The primary function of insulin is viewed as a hormone that controls blood glucose level. However, there is growing evidence that aberrant insulin level and insulin-mediated signaling can lead to cancer development and progression. The insulin-cancer relationship has stemmed from various observational and epidemiological studies, which linked higher incidence of cancer with central obesity, type II diabetes and other conditions associated with increased levels of circulating insulin, insulin resistance and hyperinsulinemic states. Increased risk of developing a range of cancers is also seen with a certain treatment options used to lower blood glucose level in diabetic patients. While metformin monotherapy has the lowest risk of developing cancer, in comparison, treatment with insulin or insulin secretagogues shows more likelihood to develop solid cancers. Cellular signaling initiated by insulin provides a clue regarding these diverse cellular outcomes. This review discusses how the insulin enacts such diverse physiological effects and the insulin-cancer relationship, with focus on the role of insulin signaling in cancer.

Leung WK, He M, Chan AW, et al.
Wnt/β-Catenin activates MiR-183/96/182 expression in hepatocellular carcinoma that promotes cell invasion.
Cancer Lett. 2015; 362(1):97-105 [PubMed] Related Publications
Nearly 50% of known miRNAs are found in clusters and transcribed as polycistronic transcripts. In this study, we showed that over-expression of miR-183/96/182 cluster is frequent in hepatocellular carcinoma (HCC), a highly aggressive malignancy that is commonly fatal. In a cohort of HCC patients (n = 81), miR-183/96/182 up-regulation correlated with metastatic features including presence of microvascular invasion, advanced tumor differentiation, and shorter recurrence-free survival. Univariate and multivariate analyses further showed miR-183/96/182 over-expression represented an independent prognostic factor (Relative Risk: 2.0471; P = 0.0289). Functional investigation using siRNA against miR-183/96/182 in two invasive HCC cells indicated significant inhibition on cell migration and invasion without affecting cell viability. Forkhead boxO1 (FOXO1) was further validated as a downstream target of these three miRNAs. In investigating the regulatory mechanism underlining miR-183/96/182 over-expression, a direct interaction of CTNNB1 on the promoter region was confirmed by ChIP-PCR and luciferase reporter validations. Knockdown of CTNNB1 also showed concordant down-regulations of miR-183, -96 and -182, and the re-expression of FOXO1. Our findings demonstrated that over-expression of miR-183/96/182 confers an oncogenic function in HCC cell dissemination, and could serve as an independent prognostic predictor for HCC patients.

Martinez-Outschoorn UE, Sotgia F, Lisanti MP
Caveolae and signalling in cancer.
Nat Rev Cancer. 2015; 15(4):225-37 [PubMed] Related Publications
It has been over 20 years since the discovery that caveolar lipid rafts function as signalling organelles. Lipid rafts create plasma membrane heterogeneity, and caveolae are the most extensively studied subset of lipid rafts. A newly emerging paradigm is that changes in caveolae also generate tumour metabolic heterogeneity. Altered caveolae create a catabolic tumour microenvironment, which supports oxidative mitochondrial metabolism in cancer cells and which contributes to dismal survival rates for cancer patients. In this Review, we discuss the role of caveolae in tumour progression, with a special emphasis on their metabolic and cell signalling effects, and their capacity to transform the tumour microenvironment.

Hnisz D, Schuijers J, Lin CY, et al.
Convergence of developmental and oncogenic signaling pathways at transcriptional super-enhancers.
Mol Cell. 2015; 58(2):362-70 [PubMed] Article available free on PMC after 16/04/2016 Related Publications
Super-enhancers and stretch enhancers (SEs) drive expression of genes that play prominent roles in normal and disease cells, but the functional importance of these clustered enhancer elements is poorly understood, so it is not clear why genes key to cell identity have evolved regulation by such elements. Here, we show that SEs consist of functional constituent units that concentrate multiple developmental signaling pathways at key pluripotency genes in embryonic stem cells and confer enhanced responsiveness to signaling of their associated genes. Cancer cells frequently acquire SEs at genes that promote tumorigenesis, and we show that these genes are especially sensitive to perturbation of oncogenic signaling pathways. Super-enhancers thus provide a platform for signaling pathways to regulate genes that control cell identity during development and tumorigenesis.

Chen Z, Shojaee S, Buchner M, et al.
Signalling thresholds and negative B-cell selection in acute lymphoblastic leukaemia.
Nature. 2015; 521(7552):357-61 [PubMed] Article available free on PMC after 21/11/2015 Related Publications
B cells are selected for an intermediate level of B-cell antigen receptor (BCR) signalling strength: attenuation below minimum (for example, non-functional BCR) or hyperactivation above maximum (for example, self-reactive BCR) thresholds of signalling strength causes negative selection. In ∼25% of cases, acute lymphoblastic leukaemia (ALL) cells carry the oncogenic BCR-ABL1 tyrosine kinase (Philadelphia chromosome positive), which mimics constitutively active pre-BCR signalling. Current therapeutic approaches are largely focused on the development of more potent tyrosine kinase inhibitors to suppress oncogenic signalling below a minimum threshold for survival. We tested the hypothesis that targeted hyperactivation--above a maximum threshold--will engage a deletional checkpoint for removal of self-reactive B cells and selectively kill ALL cells. Here we find, by testing various components of proximal pre-BCR signalling in mouse BCR-ABL1 cells, that an incremental increase of Syk tyrosine kinase activity was required and sufficient to induce cell death. Hyperactive Syk was functionally equivalent to acute activation of a self-reactive BCR on ALL cells. Despite oncogenic transformation, this basic mechanism of negative selection was still functional in ALL cells. Unlike normal pre-B cells, patient-derived ALL cells express the inhibitory receptors PECAM1, CD300A and LAIR1 at high levels. Genetic studies revealed that Pecam1, Cd300a and Lair1 are critical to calibrate oncogenic signalling strength through recruitment of the inhibitory phosphatases Ptpn6 (ref. 7) and Inpp5d (ref. 8). Using a novel small-molecule inhibitor of INPP5D (also known as SHIP1), we demonstrated that pharmacological hyperactivation of SYK and engagement of negative B-cell selection represents a promising new strategy to overcome drug resistance in human ALL.

Graziani G, Artuso S, De Luca A, et al.
A new water soluble MAPK activator exerts antitumor activity in melanoma cells resistant to the BRAF inhibitor vemurafenib.
Biochem Pharmacol. 2015; 95(1):16-27 [PubMed] Related Publications
Recovery of mitogen activated protein kinase (MAPK) or activation of alternative pathways, such as the PI3K/AKT/mTOR, are involved in acquired resistance to BRAF inhibitors which represent the first-line treatment of BRAF-mutated metastatic melanoma. We recently demonstrated that 6-((7-nitrobenzo[c][1,2,5]oxadiazol-4-yl)thio)hexan-1-ol (NBDHEX) and its water soluble analog 2-(2-(2-((7-nitrobenzo[c][1,2,5]oxadiazol-4-yl)thio)ethoxy)ethoxy)ethanol (MC3181) trigger apoptosis in BRAF V600E mutated melanoma cells through activation of the MAPK c-Jun N-terminal kinase (JNK). Herein, we investigated whether NBDHEX and MC3181 might exert antitumor activity against BRAF V600E mutated human melanoma cells rendered resistant to the BRAF inhibitor vemurafenib. To this aim we generated a subline of A375 melanoma resistant in vitro and in vivo to vemurafenib (A375-VR8) and characterized by NRAS G13R mutation, high basal levels of CRAF protein and phospho-activation of AKT. In these cells ERK phosphorylation was not significantly down-modulated by vemurafenib concentrations capable of abrogating ERK phosphorylation in sensitive A375 cells. Both NBDHEX and MC3181 induced marked antiproliferative and apoptotic effects in A375-VR8 cells and, at equitoxic concentrations, caused a strong phosphorylation of JNK, p38, and of the downstream mediators of apoptosis ATF2 and p53. Drug treatment further increased ERK phosphorylation, which was required for the cellular response to the NBD derivatives, as apoptosis was antagonized by the ERK inhibitor FR180204. Finally, in vivo administration of MC3181 provoked JNK activation at the tumor site and markedly reduced A375-VR8 growth. These evidences strongly suggest that the activation of multiple pro-apoptotic MAPK pathways by MC3181 might represent a new strategy for the treatment of melanoma resistant to BRAF inhibitors.

Jiang L, Zhang C, Wu Y, et al.
67kDa laminin receptor regulates the activation of MAPKs through DUSPs in glioma cell line U251.
J BUON. 2015 Jan-Feb; 20(1):253-60 [PubMed] Related Publications
PURPOSE: All-trans-retinoic-acid (ATRA), the active derivative of vitamin A, is critical in regulating cell cycle as well as inhibiting tumor growth and angiogenesis. It has been used in the clinical treatment of leukemia. 67kDa laminin receptor (67LR), as one of the receptor of laminin, plays an important role in tumor cells invasion, proliferation and metastasis. Current research indicates that 67LR is highly expressed in glioma and is associated with tumor progression. However, the underlying molecular mechanisms, especially the signaling pathways involved, have not been reported yet. Therefore it is of great importance to clarify its downstream targets.
METHODS: The U251 glioma cell line was used in this study. Cell Counting Kit-8 was used in cell proliferation assay. Quantitative real-time PCR (qRT-PCR) was used to determine the transcription level of dual specificity phosphatases (DUSPs). Western blot analysis was used to detect the expression of mitogen activated protein kinases (MAPKs) and phosphorylated MAPKs.
RESULTS: 67LR could influence the transcription of DUSPs and expression of MAPKs. ATRA could enhance the expression of 67LR in U251 cells and this enhancement was dose-dependent. ATRA was able to inhibit the growth of U251 cells.
CONCLUSIONS: ATRA expressed significant therapeutic effect on glioma cells, and 67LR is not the only factor that can influence the proliferation of U251 cells.

Zhang CZ, Wang XD, Wang HW, et al.
Sorafenib inhibits liver cancer growth by decreasing mTOR, AKT, and PI3K expression.
J BUON. 2015 Jan-Feb; 20(1):218-22 [PubMed] Related Publications
PURPOSE: The purpose of this study was to determine the impact of sorafenib on PI3K/AKT/mTOR signaling pathway and to further define its mechanism for treating hepatocellular carcinoma (HCC).
METHODS: Human SMMC-7721 hepatic carcinoma cells were treated with or without 4 μmoL/L sorafenib. SMMC- 7721 cells were harvested at various time points (0-48 hrs) and assessed for changes in PI3K, mTOR, and AKT protein and mRNA levels.
RESULTS: Human SMMC-7721 hepatic tumor cells exposed to sorafenib had decreased expression of PI3K/mTOR/AKT.
CONCLUSION: Sorafenib appears to inhibit hepatic tumor growth by downregulating PI3k/Akt/mTOR signaling pathway.

Hara Y, Yamashita T, Oishi N, et al.
TSU-68 ameliorates hepatocellular carcinoma growth by inhibiting microenvironmental platelet-derived growth factor signaling.
Anticancer Res. 2015; 35(3):1423-31 [PubMed] Related Publications
BACKGROUND: TSU-68 is a multikinase inhibitor that targets platelet-derived growth factor receptors (PDGFRs). In the present study, we evaluated the effect of TSU-68 on the tumor-microenvironment interaction in hepatocellular carcinoma (HCC).
MATERIALS AND METHODS: HCC and fibroblast cell lines (HuH7, Hep3B, HuH1 and WI-38) were used to evaluate their interactions. Cancer characteristics were evaluated by spheroid formation and tumorigenicity in immunodeficient mice. Time-lapse image analysis was performed to monitor cell motility.
RESULTS: Although PDGFA was abundantly expressed, PDGFR-α was predominantly located in the cytoplasm and was not functional in HuH7 cells. Co-culture experiments demonstrated that HCC cells induced phosphorylation of PDGFR-α in WI-38 fibroblasts and that stimulated fibroblasts, in turn, boosted the spheroid formation capacity of HCC cells. TSU-68 inhibited phosphorylation of PDGFR-α in WI-38 cells and suppressed the growth of subcutaneously co-injected HuH7/WI-38 tumor xenografts.
CONCLUSION: TSU-68 inhibits stromal PDGF signaling activated by cancer cells and suppresses HCC growth.

Ali I, Damdimopoulou P, Stenius U, Halldin K
Cadmium at nanomolar concentrations activates Raf-MEK-ERK1/2 MAPKs signaling via EGFR in human cancer cell lines.
Chem Biol Interact. 2015; 231:44-52 [PubMed] Related Publications
Cadmium (Cd) is an environmental contaminant classified as carcinogenic to humans by the International Agency for Research on Cancer, supported by data from occupational exposure. Environmentally relevant dietary exposure to Cd has recently been associated with osteoporosis and cancers of the prostate, endometrium, and breast in the general population. The low exposure effects have been proposed to result from endocrine modulative properties of Cd, which mimic the physiological actions of estrogen and androgen. However, the mechanism of action of Cd is an unanswered question. We have shown previously, using mouse models, that canonical estrogen receptor signaling is not involved in estrogen mimicry effects of Cd. Instead, low-level Cd exposure stimulated the mitogen-activated protein kinases (MAPKs) ERK1/2 in these mice. Here we investigate further the ERK1/2 MAPK signaling activation by Cd in vitro by using nanomolar concentrations of cadmium chloride (CdCl2) in three different human carcinoma cell lines: HepG2, MCF-7, and ECC-1. The findings also were confirmed in previously collected mouse tissue samples. We show that 10(-8)M levels of CdCl2 activate ERK1/2 (Tyr 204) and the p53 specific ubiquitin ligase Mdm2 (Ser 166) via Raf and MEK by acting through the epidermal growth factor receptor (EGFR). Furthermore, our results suggest that the CdCl2-induced activation of ERK1/2 and Mdm2 may interfere with the p53 response to genotoxic compounds in cancer cell lines. Our data collectively suggest that nanomolar levels of CdCl2 activate Raf-MEK-ERK1/2 via EGFR. We hypothesize that this signaling cascade may be involved in observed low exposure effects of Cd in certain human populations.

Zuo M, Rashid A, Churi C, et al.
Novel therapeutic strategy targeting the Hedgehog signalling and mTOR pathways in biliary tract cancer.
Br J Cancer. 2015; 112(6):1042-51 [PubMed] Article available free on PMC after 17/03/2016 Related Publications
BACKGROUND: Activation of the PI3K/mTOR and Hedgehog (Hh) signalling pathways occurs frequently in biliary tract cancer (BTC). Crosstalk between these pathways occurs in other gastrointestinal cancers. The respective signalling inhibitors rapamycin and vismodegib may inhibit BTC synergistically and suppress cancer stem cells (CSCs).
METHODS: Gene expression profiling for p70S6k and Gli1 was performed with BTC cell lines. Tumour and pathway inhibitory effects of rapamycin and vismodegib were investigated in BTC preclinical models and CSCs.
RESULTS: Rapamycin and vismodegib synergistically reduced BTC cell viability and proliferation. This drug combination arrested BTC Mz-ChA-1 cells in the G1 phase but had no significant effect on the cell cycle of BTC Sk-ChA-1 cells. Combined treatment inhibited the proliferation of CSCs and ALDH-positive cells. Nanog and Oct-4 expression in CSCs was decreased by the combination treatment. Western blotting results showed the p-p70S6K, p-Gli1, p-mTOR, and p-AKT protein expression were inhibited by the combination treatment in BTC cells. In an Mz-ChA-1 xenograft model, combination treatment resulted in 80% inhibition of tumour growth and prolonged tumour doubling time. In 4 of 10 human BTC specimens, tumour p-p70S6K and Gli1 protein expression levels were decreased with the combination treatment.
CONCLUSIONS: Targeted inhibition of the PI3K/mTOR and Hhpathways indicates a new avenue for BTC treatment with combination therapy.

Yang P, Li Z, Wang Y, et al.
Secreted pyruvate kinase M2 facilitates cell migration via PI3K/Akt and Wnt/β-catenin pathway in colon cancer cells.
Biochem Biophys Res Commun. 2015; 459(2):327-32 [PubMed] Related Publications
Pyruvate Kinase M2 (PKM2) is a key glycolytic enzyme, which highly expressed in tumor cells, and plays a pivotal role in the growth, survival and metabolism reprogramming of cancer cells. Besides the location of cytoplasm as a glycolytic enzyme and the location of nucleus as a protein kinase, extracellular PKM2 is present in serum and feces of tumor patients. However, little is known about the secretion of PKM2 and its significance in the progression of colon cancer. Here we demonstrated that PKM2 could be secreted from colon cancer cells, and purified PKM2 protein mimicing the secreted PKM2 was able to promote colon cancer cell migration. Moreover, PI3K/Akt and Wnt/β-catenin signaling were involved in secreted PKM2 induced colon cancer cell migration. The results reveal critical roles of secreted PKM2 in the progression of colon cancer, and indicate that PKM2 may be a therapeutic target for colon cancer.

Sun SS, Zhang L, Yang J, Zhou X
Role of runt-related transcription factor 2 in signal network of tumors as an inter-mediator.
Cancer Lett. 2015; 361(1):1-7 [PubMed] Related Publications
Runt-related transcription factor 2 (RUNX2) is a member of the polyomavirus enhancer-binding protein 2/core-binding factor superfamily. RUNX2 is known for its contribution to osteoblast phenotype and bone formation. In recent years, increasing attention has been focused on the relationship of Runx2 with tumorigenesis. In different types of tumor cells, RUNX2 cooperates with its co-activators or co-inhibitors, and mediates the responses of cells to various signaling pathways that are hyperactive in tumors. Thus, several downstream target genes of RUNX2 are activated when RUNX2 interacts with its co-factors, leading to a variety of effects on tumor cells (epithelial-mesenchymal transition, metastasis, proliferation, and osteolytic lesion). This review focuses on the involvement of RUNX2 in tumor cells in the crosstalk of diverse signaling pathways and its multiple functions to develop optimal and feasible approaches for clinical treatment based on the functions of RUNX2.

Yang Y, Cheon S, Jung MK, et al.
Interleukin-18 enhances breast cancer cell migration via down-regulation of claudin-12 and induction of the p38 MAPK pathway.
Biochem Biophys Res Commun. 2015; 459(3):379-86 [PubMed] Related Publications
Interleukin-18 (IL-18) was recently reported to have a pro-tumor effect in various cancers. Increased IL-18 levels in the serum of cancer patients correlated with malignancy, and IL-18 acts a crucial factor for cell migration in gastric cancer and melanoma. Claudins, which are the most important tight junction proteins, are also linked with cancer progression and metastasis. However, the relationship between claudins and IL-18 is not well-understood. Here, we show that the migratory ability of MCF-7 cells was reduced when endogenous IL-18 expression was inhibited with IL-18 siRNA. Moreover, exogenous IL-18 enhanced breast cancer cell migration and suppressed the expression of the tight junction proteins claudin-1, claudin-3, claudin-4, and claudin-12 in MCF-7 cells. Knockdown of claudin-3, claudin-4, and claudin-12, but not claudin-1, increased breast cancer migration with maximal effects observed in claudin-12 siRNA-transfected cells. To investigate whether the mitogen-activated protein kinase (MAPK) signaling pathway is involved in IL-18-induced cell migration and claudin-12 expression, cells were pretreated with SB203580 (an inhibitor of p38 MAPK) or PD98059 (an inhibitor of ERK1/2) prior to the addition of IL-18. Although pretreatment of MCF-7 cells with SB203580 blocked both the enhanced cell migration and the decreased claudin-12 expression, PD98059 only blocked cell migration and did not affect claudin-12 expression. In addition, exogenous IL-18 induced rapid phosphorylation of p38 MAPK. These results suggest that IL-18 is an important factor inducing breast cancer cell migration through down-regulation of claudin-12 and activation of the p38 MAPK pathway.

Guo J, Xu Y, Ji W, et al.
Effects of exposure to benzo[a]pyrene on metastasis of breast cancer are mediated through ROS-ERK-MMP9 axis signaling.
Toxicol Lett. 2015; 234(3):201-10 [PubMed] Related Publications
Metastasis is the leading cause of deaths in patients with breast cancer. Benzo[a]pyrene is a cumulative carcinogen and ubiquitous environmental pollutant with potent carcinogenic properties. As we report here, we established an accumulative mouse model mimicking the cumulative effects of benzo[a]pyrene exposure in human breast carcinogenesis. Our focus was on elucidating the mechanisms by which benzo[a]pyrene contributes to the process of breast cancer metastasis. Our study indicated that benzo[a]pyrene increased the migration of breast cancer cells both in vitro and in vivo. Specifically, we demonstrated that benzo[a]pyrene enhances breast cancer cell migration and invasion by up-regulating ROS-induced ERK signaling, leading to the activation of matrix metalloproteinases 9. Our results suggest that benzo[a]pyrene-induced mammary gland cancer metastasis is an important and intricate process facilitated by cumulative benzo[a]pyrene exposure leading to activation of the ROS-ERK-MMP9 signaling pathway.

Montero J, Sarosiek KA, DeAngelo JD, et al.
Drug-induced death signaling strategy rapidly predicts cancer response to chemotherapy.
Cell. 2015; 160(5):977-89 [PubMed] Article available free on PMC after 26/02/2016 Related Publications
There is a lack of effective predictive biomarkers to precisely assign optimal therapy to cancer patients. While most efforts are directed at inferring drug response phenotype based on genotype, there is very focused and useful phenotypic information to be gained from directly perturbing the patient's living cancer cell with the drug(s) in question. To satisfy this unmet need, we developed the Dynamic BH3 Profiling technique to measure early changes in net pro-apoptotic signaling at the mitochondrion ("priming") induced by chemotherapeutic agents in cancer cells, not requiring prolonged ex vivo culture. We find in cell line and clinical experiments that early drug-induced death signaling measured by Dynamic BH3 Profiling predicts chemotherapy response across many cancer types and many agents, including combinations of chemotherapies. We propose that Dynamic BH3 Profiling can be used as a broadly applicable predictive biomarker to predict cytotoxic response of cancers to chemotherapeutics in vivo.

Oshimori N, Oristian D, Fuchs E
TGF-β promotes heterogeneity and drug resistance in squamous cell carcinoma.
Cell. 2015; 160(5):963-76 [PubMed] Related Publications
Subsets of long-lived, tumor-initiating stem cells often escape cancer therapies. However, sources and mechanisms that generate tumor heterogeneity and drug-resistant cell population are still unfolding. Here, we devise a functional reporter system to lineage trace and/or genetic ablate signaling in TGF-β-activated squamous cell carcinoma stem cells (SCC-SCs). Dissecting TGF-β's impact on malignant progression, we demonstrate that TGF-β concentrating near tumor-vasculature generates heterogeneity in TGF-β signaling at tumor-stroma interface and bestows slower-cycling properties to neighboring SCC-SCs. While non-responding progenies proliferate faster and accelerate tumor growth, TGF-β-responding progenies invade, aberrantly differentiate, and affect gene expression. Intriguingly, TGF-β-responding SCC-SCs show increased protection against anti-cancer drugs, but slower-cycling alone does not confer survival. Rather, TGF-β transcriptionally activates p21, which stabilizes NRF2, thereby markedly enhancing glutathione metabolism and diminishing effectiveness of anti-cancer therapeutics. Together, these findings establish a surprising non-genetic paradigm for TGF-β signaling in fueling heterogeneity in SCC-SCs, tumor characteristics, and drug resistance.

Lee JC, Chung LC, Chen YJ, et al.
Upregulation of B-cell translocation gene 2 by epigallocatechin-3-gallate via p38 and ERK signaling blocks cell proliferation in human oral squamous cell carcinoma cells.
Cancer Lett. 2015; 360(2):310-8 [PubMed] Related Publications
Oral squamous cell carcinoma (OSCC) is a well-known malignancy that accounts for the majority of oral cancers. B-cell translocation gene 2 (BTG2) is an important regulator of cell cycle dynamics in cancer cells. However, the role of BTG2 in OSCC cells and the influences of epigallocatechin-3-gallate (EGCG) on BTG2 gene expressions have not been well evaluated. The objectives of this study were to examine the effect of EGCG-induced BTG2 expression and the potential signal pathways involved. The (3)H-thymidine incorporation and Western-blot assays revealed cell proliferation was attenuated by EGCG via upregulation of BTG2 expression causing cell cycle G1 phase arrest in OSCC cells. BTG2 overexpression decreased tumor cell growth, while BTG2 knockdown illuminated the opposite effect in xenograft animal studies. Overexpressed BTG2 arrested the cell cycle at the G1 phase and downregulated protein expressions of cyclin A, cyclin D, and cyclin E. Western-blot assays indicated that EGCG induced phosphorylation of p38, JNK, and ERK. However, pretreatments with selective mitogen-activated protein kinase (MAPK) inhibitors, SB203580 (p38 inhibitor) and PD0325901 (ERK1/2 inhibitor), significantly suppressed the activation of EGCG on BTG2 expression. Our results indicate that EGCG attenuates cell proliferation of OSCC cells by upregulating BTG2 expression via p38 and ERK pathways.

Xing C, Zhang R, Cui J, et al.
Pathway crosstalk analysis of non-small cell lung cancer based on microarray gene expression profiling.
Tumori. 2015 Jan-Feb; 101(1):111-6 [PubMed] Related Publications
AIMS AND BACKGROUND: Lung cancer is characterized by uncontrolled cell growth in the lung tissue. A major challenge in cancer research is the biological interpretation of the complexity of cancer somatic mutation profiles. This study examines the role of pathway crosstalk in the metastatic process of lung cancer cells based on DNA microarray analysis.
METHODS: We downloaded the gene expression profile GSE10096 from the Gene Expression Omnibus database. Differentially expressed genes (DEGs) were identified and the gene functions of selected DEGs were further analyzed. After KEGG pathway analysis, dysfunctional pathways and dysfunctional crosstalk between pathways in two types of lung cancer cells (low metastasis, M1, and high metastasis, M5) were examined.
RESULTS: A total of 13433 genes were filtered as DEGs, and after pathway analysis, 108 signaling pathways related to cancer signaling pathways were screened, including a host pathway hsa05223 and 79 neighbor pathways. Dysfunctional crosstalk analysis of pathways revealed that pathway crosstalk dysfunction of M1 and M5 cells mainly occurred between hsa05223 (non-small cell lung cancer) and hsa04310 (Wnt signaling pathway), and between non-small cell lung cancer and hsa04520 (adherens junction), respectively. Significant pathway crosstalk dysfunction also existed between adherens junction and other classical signaling pathways such as hsa04110 (cell cycle), hsa04310 (Wnt signaling pathway), hsa04350 (TGF-beta signaling pathway), and hsa04630 (Jak-STAT signaling pathway).
CONCLUSIONS: Our discovery will help to elucidate the molecular mechanisms of the high carcinogenic and metastatic potential of lung cancer cells. In addition, it will pave the way to developing effective therapies for lung cancer.

Samadani R, Zhang J, Brophy A, et al.
Small-molecule inhibitors of ERK-mediated immediate early gene expression and proliferation of melanoma cells expressing mutated BRaf.
Biochem J. 2015; 467(3):425-38 [PubMed] Related Publications
Constitutive activation of the extracellular-signal-regulated kinases 1 and 2 (ERK1/2) are central to regulating the proliferation and survival of many cancer cells. The current inhibitors of ERK1/2 target ATP binding or the catalytic site and are therefore limited in their utility for elucidating the complex biological roles of ERK1/2 through its phosphorylation and regulation of over 100 substrate proteins. To overcome this limitation, a combination of computational and experimental methods was used to identify low-molecular-mass inhibitors that are intended to target ERK1/2 substrate-docking domains and selectively interfere with ERK1/2 regulation of substrate proteins. In the present study, we report the identification and characterization of compounds with a thienyl benzenesulfonate scaffold that were designed to inhibit ERK1/2 substrates containing an F-site or DEF (docking site for ERK, FXF) motif. Experimental evidence shows the compounds inhibit the expression of F-site containing immediate early genes (IEGs) of the Fos family, including c-Fos and Fra1, and transcriptional regulation of the activator protein-1 (AP-1) complex. Moreover, this class of compounds selectively induces apoptosis in melanoma cells containing mutated BRaf and constitutively active ERK1/2 signalling, including melanoma cells that are inherently resistant to clinically relevant kinase inhibitors. These findings represent the identification and initial characterization of a novel class of compounds that inhibit ERK1/2 signalling functions and their potential utility for elucidating ERK1/2 and other signalling events that control the growth and survival of cancer cells containing elevated ERK1/2 activity.

Wu K, Fukuda K, Xing F, et al.
Roles of the cyclooxygenase 2 matrix metalloproteinase 1 pathway in brain metastasis of breast cancer.
J Biol Chem. 2015; 290(15):9842-54 [PubMed] Article available free on PMC after 10/04/2016 Related Publications
Brain is one of the major sites of metastasis in breast cancer; however, the pathological mechanism of brain metastasis is poorly understood. One of the critical rate-limiting steps of brain metastasis is the breaching of blood-brain barrier, which acts as a selective interface between the circulation and the central nervous system, and this process is considered to involve tumor-secreted proteinases. We analyzed clinical significance of 21 matrix metalloproteinases on brain metastasis-free survival of breast cancer followed by verification in brain metastatic cell lines and found that only matrix metalloproteinase 1 (MMP1) is significantly correlated with brain metastasis. We have shown that MMP1 is highly expressed in brain metastatic cells and is capable of degrading Claudin and Occludin but not Zo-1, which are key components of blood-brain barrier. Knockdown of MMP1 in brain metastatic cells significantly suppressed their ability of brain metastasis in vivo, whereas ectopic expression of MMP1 significantly increased the brain metastatic ability of the cells that are not brain metastatic. We also found that COX2 was highly up-regulated in brain metastatic cells and that COX2-induced prostaglandins were directly able to promote the expression of MMP1 followed by augmenting brain metastasis. Furthermore, we found that COX2 and prostaglandin were able to activate astrocytes to release chemokine (C-C motif) ligand 7 (CCL7), which in turn promoted self-renewal of tumor-initiating cells in the brain and that knockdown of COX2 significantly reduced the brain metastatic ability of tumor cells. Our results suggest the COX2-MMP1/CCL7 axis as a novel therapeutic target for brain metastasis.

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