Molecular Target For Cancer Therapeutics Research Articles

Cytotoxic Activity of Novel GnRH Analogs Conjugated with Mitoxantrone in Ovarian Cancer Cells.

The gonadotropin-releasing hormone (GnRH) receptor (GnRH-R) is highly expressed in ovarian cancer cells (OCC), and it is an important molecular target for cancer therapeutics. To develop a new class of drugs targeting OCC, we designed and synthesized Con-3 and Con-7 which are novel high-affinity GnRH-R agonists, covalently coupled through a disulfide bond to the DNA synthesis inhibitor mitoxantrone. We hypothesized that Con-3 and Con-7 binding to the GnRH-R of OCC would expose the conjugated mitoxantrone to the cellular thioredoxin, which reduces the disulfide bond of Con-3 and Con-7. The subsequent release of mitoxantrone leads to its intracellular accumulation, thus exerting its cytotoxic effects. To test this hypothesis, we determined the cytotoxic effects of Con-3 and Con-7 using the SKOV-3 human OCC. Treatment with Con-3 and Con-7, but not with their unconjugated GnRH counterparts, resulted in the accumulation of mitoxantrone within the SKOV-3 cells, increased their apoptosis, and reduced their proliferation, in a dose- and time-dependent manner, with half-maximal inhibitory concentrations of 0.6-0.9 µM. It is concluded that Con-3 and Con-7 act as cytotoxic "prodrugs" in which mitoxantrone is delivered in a GnRH-R-specific manner and constitute a new class of lead compounds for use as anticancer drugs targeting ovarian tumors.

Single-Cell Visualization of Monogenic RNA G-quadruplex and Occupied G-quadruplex Ratio through a Module-Assembled Multifunctional Probes Assay (MAMPA).

G-quadruplexes (G4s), non-canonical nucleic acid secondary structure, regulate many biological functions and are considered potential molecular targets for cancer therapeutics. However, due to the lack of analytical methods, the regulating mechanism of monogenic G4s is still unclear. Here, we developed a Module Assembled Multifunctional Probes Assay (MAMPA) for visualizing endogenous G4s in individual genes in single cells. Two modular probes separately recognize G4 structures and the adjacent RNA sequences, and the module assembly enables imaging of G4s in an individual RNA with high specificity. Through imaging G4s in several individual genes, we found that G4s were steadily occupied by G4 Binding Proteins (G4BPs) in various mRNAs in every cell line and defined "Occupied G4 Ratio". We demonstrated MAMPA was suitable for most experimental situations and found that Occupied G4 Ratios had the potential to become a new parameter for the study of G4s in living cells.

Single‐Cell Visualization of Monogenic RNA G‐quadruplex and Occupied G‐quadruplex Ratio through a Module‐Assembled Multifunctional Probes Assay (MAMPA)

AbstractG‐quadruplexes (G4s), non‐canonical nucleic acid secondary structure, regulate many biological functions and are considered potential molecular targets for cancer therapeutics. However, due to the lack of analytical methods, the regulating mechanism of monogenic G4s is still unclear. Here, we developed a Module Assembled Multifunctional Probes Assay (MAMPA) for visualizing endogenous G4s in individual genes in single cells. Two modular probes separately recognize G4 structures and the adjacent RNA sequences, and the module assembly enables imaging of G4s in an individual RNA with high specificity. Through imaging G4s in several individual genes, we found that G4s were steadily occupied by G4 Binding Proteins (G4BPs) in various mRNAs in every cell line and defined “Occupied G4 Ratio”. We demonstrated MAMPA was suitable for most experimental situations and found that Occupied G4 Ratios had the potential to become a new parameter for the study of G4s in living cells.

An Updated Focus on Quadruplex Structures as Potential Therapeutic Targets in Cancer.

Non-canonical, four-stranded nucleic acids secondary structures are present within regulatory regions in the human genome and transcriptome. To date, these quadruplex structures include both DNA and RNA G-quadruplexes, formed in guanine-rich sequences, and i-Motifs, found in cytosine-rich sequences, as their counterparts. Quadruplexes have been extensively associated with cancer, playing an important role in telomere maintenance and control of genetic expression of several oncogenes and tumor suppressors. Therefore, quadruplex structures are considered attractive molecular targets for cancer therapeutics with novel mechanisms of action. In this review, we provide a general overview about recent research on the implications of quadruplex structures in cancer, firstly gathering together DNA G-quadruplexes, RNA G-quadruplexes as well as DNA i-Motifs.

Pathophysiological Role of Histamine H4 Receptor in Cancer: Therapeutic Implications.

Cancer is a leading cause of death in both developed and developing countries. Although advances in cancer research lead to improved anti-neoplastic therapies, they continue to have unfavorable outcomes, including poor response and severe toxicity. Thus, the challenge for the new therapeutic approaches is to increase anti-tumor efficacy by targeting different molecules encompassed in the tumor and its microenvironment, as well as their specific interactions. The histamine H4 receptor (H4R) is the last discovered histamine receptor subtype and it modulates important immune functions in innate and in adaptive immune responses. Several ligands have been developed and some of them are being used in clinical trials for immune disorders with promising results. When searched in The Cancer Genome Atlas (TCGA) database, human H4R gene was found to be expressed in bladder cancer, kidney cancer, breast cancer, gastrointestinal cancers, lung cancer, endometrial cancer, and skin cancer. In the present work, we aimed to briefly summarize current knowledge in H4R’s pharmacology and in the clinical use of H4R ligands before focusing on recent data reporting the expression of H4R and its pathophysiological role in cancer, representing a potential molecular target for cancer therapeutics. H4R gene and protein expression in different types of cancers compared with normal tissue as well as its relationship with patient prognosis in terms of survival will be described.

MiR-149 as a Potential Molecular Target for Cancer.

MicroRNAs (miRNAs) are frequently dysregulated in cancers and serve as attractive targets for prognostication and therapeutic applications. Besides cancer, the biological functions of miR-149 have been studied in various diseases. This review aims to summarize the reports available in the literature, regarding miR-149 as a molecular target for cancer therapeutics. An extensive literature search was conducted using the Pubmed database to sieve out articles related to the roles of miR-149 in carcinogenesis and cancer progression, and potential miRNA-based therapies. A total of 89 publications were selected for inclusion in this review. Depending on the cancer type, miR-149 can behave either as a tumor suppressor or as an 'onco-miR' that promotes tumorigenesis and cancer spread, suggesting that this miRNA has diverse functions. Potential miRNA-based therapies include the use of miRNA mimics, miRNA inhibitors, demethylating agents and circular RNAs. Although targeting miRNA is an attractive anti-cancer strategy, not all cancers can be treated by the same miRNA-based strategy. A comprehensive understanding of miRNA regulatory mechanism is also necessary to improve the design of miRNA-based therapeutics and there is a need for safe and efficient delivery methods when using this approach for anti-cancer treatment.

Epigenetic restriction of Hippo signaling by MORC2 underlies stemness of hepatocellular carcinoma cells.

The evolutionarily conserved Hippo signaling pathway is a key regulator of stem cell self-renewal, differentiation, and organ size. While alterations in Hippo signaling are causally linked to uncontrolled cell growth and a broad range of malignancies, genetic mutations in the Hippo pathway are uncommon and it is unclear how the tumor suppressor function of the Hippo pathway is disrupted in human cancers. Here, we report a novel epigenetic mechanism of Hippo inactivation in the context of hepatocellular carcinoma (HCC). We identify a member of the microrchidia (MORC) protein family, MORC2, as an inhibitor of the Hippo pathway by controlling upstream Hippo regulators, neurofibromatosis 2 (NF2) and kidney and brain protein (KIBRA). Mechanistically, MORC2 forms a complex with DNA methyltransferase 3A (DNMT3A) at the promoters of NF2 and KIBRA, leading to their DNA hyper-methylation and transcriptional repression. As a result, NF2 and KIBRA are crucial targets of MORC2 to regulate confluence-induced activation of Hippo signaling and contact inhibition of cell growth under both physiological and pathological conditions. The MORC2-NF2/KIBRA axis is critical for maintaining self-renewal, sorafenib resistance, and oncogenicity of HCC cells in vitro and in nude mice. Furthermore, MORC2 expression is elevated in HCC tissues, associated with stem-like properties of cancer cells, and disease progression in patients. Collectively, MORC2 promotes cancer stemness and tumorigenesis by facilitating DNA methylation-dependent silencing of Hippo signaling and could be a potential molecular target for cancer therapeutics.

Natural Alkaloids and Heterocycles as G-Quadruplex Ligands and Potential Anticancer Agents.

G-quadruplexes are four-stranded nucleic acid secondary structures that are formed in guanine-rich sequences. G-quadruplexes are widely distributed in functional regions of the human genome and transcriptome, such as human telomeres, oncogene promoter regions, replication initiation sites, and untranslated regions. Many G-quadruplex-forming sequences are found to be associated with cancer, and thus, these non-canonical nucleic acid structures are considered to be attractive molecular targets for cancer therapeutics with novel mechanisms of action. In this mini review, we summarize recent advances made by our lab in the study of G-quadruplex-targeted natural alkaloids and their derivatives toward the development of potential anticancer agents.

UHRF1: The key regulator of epigenetics and molecular target for cancer therapeutics.

UHRF1 is a master regulator of epigenome as it coordinates DNA methylation and histone modifications. Compelling evidence suggests a strong link between UHRF1 overexpression and tumorigenesis, substantiating its ability to act as a potential biomarker for cancer diagnosis and prognosis. UHRF1 also mediates repair of damaged DNA that makes cancer cells resistant toward cytocidal drugs. Hence, understanding the molecular mechanism of UHRF1 regulation would help in developing cancer therapeutics. Natural compounds have shown applicability to downregulate UHRF1 leading to growth arrest and apoptosis in cancer cells.

STIM and ORAI proteins: crucial roles in hallmarks of cancer.

Intracellular Ca(2+) signals play a central role in several cellular processes; therefore it is not surprising that altered Ca(2+) homeostasis regulatory mechanisms lead to a variety of severe pathologies, including cancer. Stromal interaction molecules (STIM) and ORAI proteins have been identified as critical components of Ca(2+) entry in both store-dependent (SOCE mechanism) and independent by intracellular store depletion and have been implicated in several cellular functions. In recent years, both STIMs and ORAIs have emerged as possible molecular targets for cancer therapeutics. In this review we focus on the role of STIM and ORAI proteins in cancer progression. In particular we analyze their role in the different hallmarks of cancer, which represent the organizing principle that describes the complex multistep process of neoplastic diseases.

DNA G-quadruplex and its potential as anticancer drug target.

G-quadruplex secondary structures are four-stranded globular nucleic acid structures form in the specific DNA and RNA G-rich sequences with biological significance such as human telomeres, oncogene-promoter regions, replication initiation sites, and 5' and 3'-untranslated (UTR) regions. The non-canonical G-quadruplex secondary structures can readily form under physiologically relevant ionic conditions and are considered to be new molecular target for cancer therapeutics. This review discusses the essential progress in our lab related to the structures and functions of biologically relevant DNA G-quadruplexes in human gene promoters and telomeres, and the opportunities presented for the development of G-quadruplex-targeted small- molecule drugs.

Abstract B73: Proteostasis network modules as molecular targets for cancer therapeutics.

Abstract The maintenance of biomolecules functionality is essential for the assurance of cellular homeostasis. At the proteome level this is achieved by the action of a modular, yet integrated subcellular compartment-specific system which ensures proteome quality control and it is called the proteostasis network (PN). PN is orchestrated by a plethora of different mechanisms and complex protein machines aiming to respond to stressors, recognize and either rescue (via the action of chaperones) or degrade unfolded, misfolded or damaged polypeptides at the two main cellular proteolytic systems, namely the proteasome and the lysosome. We have found that aging is accompanied by increased proteotoxic stress and a reduction of PN modules functionality. Interestingly, proteotoxic stress is also an emerging hallmark of age-related diseases, including tumorigenesis, and we recently proposed that age-related disruption of proteostasis contributes to tumor formation by (among others) increasing genomic instability due to reduced fidelity in processes like DNA replication or repair. We also hypothesized that the carcinogenesis-related increasing proteome instability eventually triggers the reactivation of the PN modules at advanced and/or metastatic stages in order for the tumor to survive and enable its various malignant phenotypes. We are testing these hypotheses by examining the differential regulation of PN components in precancerous and cancerous lesions of tumor biopsies, as well as, in cellular models of step-wise carcinogenesis. Specifically, precancerous and cancerous lesions of the larynx along with normal epithelium were examined by immunohistochemical staining for the expression levels of Apolipoprotein J/Clusterin (CLU); a molecular chaperone that has been implicated in tumor formation, metastasis and tumor cells resistance to chemotherapeutic drugs. Additionally, human bronchial epithelial cells into which various oncogenes were sequentially introduced, as well as, a mouse skin carcinogenesis model have been used to: a) investigate the status of PN components as a response to oncogenic hits and, b) to test the differential sensitivity of tumor vs. normal cells to stressors and to PN modules inhibitors. We found that CLU expression is induced by de novo synthesis in larynx dysplasia. In support, at both human and mouse cellular models of carcinogenesis we noted higher levels and activities of PN modules in advanced tumorigenesis; these phenotypes were accompanied with increased oxidative damage and proteome instability. Interestingly, advanced and/or metastatic mouse tumor cells were more sensitive to disruption of proteostasis (e.g. proteasome inhibition) or increased oxidative load compared to normal cells, while combined proteasome and lysosomal inhibition further sensitized metastatic tumor cells. These observations indicate that while tumor evolves over a cellular landscape of increased proteome instability, tumor cells eventually become “addicted” to higher activities of the PN modules in order to survive. Thus, inhibition of PN components provides a strategy for the development of novel tumor specific therapies. We are currently investigating this option by screening for natural compounds functioning as potent inhibitors of PN modules. Citation Information: Mol Cancer Ther 2013;12(11 Suppl):B73. Citation Format: Eirini-Stavroula Komseli, Fabiola Sesti, Konstantinos Evangelou, Christina Cheimonidou, Athanassios Kotsinas, Vassilis Gorgoulis, Ioannis P. Trougakos. Proteostasis network modules as molecular targets for cancer therapeutics. [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2013 Oct 19-23; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2013;12(11 Suppl):Abstract nr B73.

Targeting Hypoxia for Sensitization of Tumors to Radio- and Chemotherapy

The heterogeneous distribution of hypoxic regions within solid tumors renders them refractive to chemo- and radio-therapies and contributes positively to tumor invasion and metastasis. Moreover, hypoxia favors the enrichment of cancer stem cells by interacting with differentiation signals via the maintenance of stem cell properties of undifferentiated cells or via the induction of cellular dedifferentiation. The discovery of the hypoxia inducible factor 1alpha (HIF-1α) has led to the current extensive interest in the signal molecules related to tumor hypoxia and the major regulatory pathways that control the family of hypoxia-inducible factors as potential molecular targets for cancer therapeutics. Multiple approaches have been developed to circumvent hypoxia-induced resistance, such as oxygenating tumors, using radiosensitizers and more recently using bio-reductively activated pro-drugs. Recent evidence suggests that radio-sensitization has undergone a paradigm shift from compounds that enhance the effect of radiation via mimicking oxygen, to compounds that target HIF-mediated signaling pathways eventually reducing radio-resistance. In this paper, we give an overview of our recent understandings in hypoxia research, discuss the mechanisms of resistance of hypoxic tumors and of hypoxia-induced cancer stem cells and highlight the latest advances in cancer treatments that target tumor hypoxia and the resistant populations of cancer stem cells. Classical and novel radio-sensitization methods, mainly the molecular inhibition of HIFs and downstream targets and the use of hypoxia-activated drugs are compared and contrasted. Such multi-faceted targeted therapies ultimately enhance treatment outcomes and reduce normal tissue toxicity by the selective targeting of solid tumors.

MicroRNAs involved in regulating epithelial–mesenchymal transition and cancer stem cells as molecular targets for cancer therapeutics

One of the major challenges in cancer gene therapy is the identification of functionally relevant tumor-specific genes as the therapeutic targets. MicroRNAs (miRNAs) are a class of small, 22-25 nucleotides, endogenously expressed noncoding RNA. miRNAs are important genetic regulators: one miRNA can possibly target multiple genes and they can function as tumor promoters (oncogenic miRNAs, oncomirs) or tumor suppressors (anti-oncomirs). Therefore, the identification of misregulated miRNAs in cellular signaling pathways related to oncogenesis can have profound implications for cancer therapy. The epithelial-mesenchymal transition (EMT) converts epithelial cells into mesenchymal cells, a normal embryological process that frequently get activated during cancer invasion and metastasis. Recent evidence also supports the presence of a small subset of self-renewing, stem-like cells within the tumor mass that possess the capacity to seed new tumors and they have been termed 'cancer stem cells (CSC)'. Conceivably, these CSCs could provide a resource for cells that cause therapy resistance. Although the cell origin of CSCs remains to be fully elucidated, a growing body of evidence has demonstrated that the biology of EMT and CSCs is tightly linked with the sequences and compositions of miRNA molecules. Therefore, targeting miRNAs involved in EMT and CSCs regulation can provide novel miRNA-based therapeutic strategies in oncology.

Novel regulation of checkpoint kinase 1: Is checkpoint kinase 1 a good candidate for anti‐cancer therapy?

DNA-damaging strategies, such as radiotherapy and the majority of chemotherapeutic therapies, are the most frequently used non-surgical anti-cancer therapies for human cancers. These therapies activate DNA damage/replication checkpoints, which induce cell-cycle arrest to provide the time needed to repair DNA damage. Due to genetic defect(s) in the ATM (ataxia-telangiectasia mutated)-Chk2-p53 pathway, an ATR (ATM- and Rad3-related)-Chk1-Cdc25 route is the sole checkpoint pathway in a majority of cancer cells. Chk1 inhibitors are expected to selectively induce the mitotic cell death (mitotic catastrophe) of cancer cells. However, recent new findings have pointed out that Chk1 is essential for the maintenance of genome integrity even during unperturbed cell-cycle progression, which is controlled by a variety of protein kinases. These observations have raised concerns about a possible risk of Chk1 inhibitors on the clinics. In this review, we summarize recent advances in Chk1 regulation by phosphorylation, and discuss Chk1 as a molecular target for cancer therapeutics.

Novel small molecule Raf kinase inhibitors for targeted cancer therapeutics

Aberrant activation of Raf signaling pathway is frequently found in various human tumors, it has been considered as distinct and promising molecular target for cancer therapeutics. B-Raf is most attractive drug target out of three Raf isoforms (A-Raf, B-Raf and C-Raf) because it exhibits high kinase activity due to frequent mutations in human tumors. However, most recently, it has been reported that Raf isoforms show the cross-activation in the presence of specific B-Raf inhibitors, which brings about the paradoxical p-ERK activation as well as tumor promoting effect. According to these findings, it remains controversy whether pan-Raf kinase inhibitor is more valuable and promising rather than specific B-Raf inhibitor under certain conditions in terms of cancer therapeutics. In this short review, novel Raf kinase inhibitors undergoing clinical investigation are introduced. Moreover, the paradoxical p-ERK activation is discussed with specific B-Raf inhibitors, PLX4032/4720 compounds.

The mitochondrial protein C1qbp promotes cell proliferation, migration and resistance to cell death

Complement 1q-Binding Protein (C1qbp) is a mitochondrial protein reported to be upregulated in cancer. However, whether C1qbp plays a tumor suppressive or tumorigenic role in the progression of cancer is controversial. Moreover, the exact effects of C1qbp on cell proliferation, migration, and death/survival have not been definitely proven. To this end, we comprehensively examined the effects of C1qbp on mitochondrial-dependent cell death, proliferation, and migration in both normal and breast cancer cells using genetic gain- and loss-of-function approaches. In normal fibroblasts, overexpression of C1qbp protected the cells against staurosporine-induce apoptosis, increased proliferation, decreased cellular ATP, and increased cell migration in a wound-healing assay. In contrast, the opposite effects were observed in fibroblasts depleted of C1qbp by RNA interference. C1qbp expression was found to be markedly elevated in 4 different human breast cancer cell lines as well as in ductal and adenocarcinoma tumors from breast cancer patients. Stable knockdown of C1qbp by shRNA in the aggressive MDA-MB-231 breast cancer cell line greatly reduced cell proliferation, increased ATP levels, and decreased cell migration compared to control shRNA-transfected cells. Moreover, C1qbp knockdown elicited a significant increase in doxorubicin-induced apoptosis in the MDA-MB-231 cells. Finally, C1qbp upregulation was not restricted to breast cancer cells and tumors, as levels of C1qbp were also found to be significantly elevated in both human lung and colon cancer cell lines and carcinomas. Together, these results establish a pro-tumor, rather than anti-tumor, role for C1qbp, and indicate that C1qbp could serve as a molecular target for cancer therapeutics.

Foxo3a Suppression of Urothelial Cancer Invasiveness through Twist1, Y-Box–Binding Protein 1, and E-Cadherin Regulation

Invasion and metastasis are key steps in the progression of urothelial cancer (UC) into a critical disease. Foxo3a is a member of the Foxo transcription factor family that modulates the expression of various genes. We aimed to elucidate the role of Foxo3a in UC invasion. Foxo3a mRNA and protein expressions in UC samples were investigated by gene expression assays and immunohistochemistry, respectively. Foxo3a expression was compared with clinicopathologic characteristics and patient prognoses based on UC samples. Quantitative real-time polymerase chain reaction, Western blotting, and migration assays were also conducted in UC cells. Foxo3a expression decreased in invasive UC; patients with low Foxo3a expression had poor disease-free survival, cancer-specific survival, and overall survival; Foxo3a knockdown in UC cells increased cellular motility. Foxo3a negatively regulated Twist1 and Y-box-binding protein 1 (YB-1), and positively regulated E-cadherin in KK47 and TCCsup cells that expressed Twist1, but not in T24 cells that did not express Twist1. Foxo3a-associated acetyltransferase p300 and Foxo3a acetylation status also affected UC motility. The results of this study indicate that Foxo3a regulates motility of UC through negative regulation of Twist1 and YB-1, and through positive regulation of E-cadherin. This suggests that Foxo3a could act as an independent prognostic factor in UC and could represent a promising molecular target for cancer therapeutics.

Abstract 765: Drug discovery for targeting the tumor microenvironment from propolis

Abstract The tumor microenvironment, characterized by regions of hypoxia, low nutrition, and acidosis due to incomplete blood vessel networks, has been recognized as a major factor that influences not only the response to conventional anti-cancer therapies but also malignant progression and metastasis. However, exploiting such a cumbersome tumor microenvironment for cancer treatment could provide tumor-specific therapeutic approaches. In particular, hypoxia is now considered a fundamentally important characteristic of the tumor microenvironment in which HIF-1 mediated gene regulation being essential for angiogenesis and tumor development. This has led to the current extensive interest in the drug discovery for tumor microenvironment including tumor specific potential molecular targets for cancer therapeutics. Propolis has pleiotropic effects and contains a variety of bioactive polyphenolic compounds. Some flavonoids of them have been reported to inhibit HIF-1α. We therefore evaluated the effects of composition of Brazilian propolis on cellular responses to hypoxia or nutrition deprivation stress for the development of novel anti-cancer drug targeting the tumor microenvironment. Materials and Method: The ethanol extract of Brazilian propolis was subjected to a series of chromatographic separations to examine HIF-1 inhibition and cytotoxicity under hypoxic and/or glucose deprived condition. The HIF-1α trans-activation effect was evaluated by HIF-1 reporter assay using stable cell lines expressing p2.1. The effect on unfolded protein response (UPR) activation in tumor cell induced by glucose deprivation or 2-deoxyglucose was also examined by GRP78 promoter reporter assay. We performed Immunoblot analysis of the HIF-1α and UPR target genes. The effects on HIF-1α dependent gene expression were investigated by RT-PCR using HCT116 cells. Result: The propolis whole extract increased HRE-dependent luciferase activity in a dose-dependent manner. From a series of chromatographic separations, we obtained fractions 3, 5 and 8 that inhibited HIF-1-dependent induction of luciferase, while fractions 6 and 10-13 increased the luciferase activity. Cinnamic acid derivative, GPU-215 was isolated from Fr.6 reduced HIF1 transactivation activity, expression of HIF-1α protein and GLUT1 mRNA under hypoxia, while flavonoid, GPU-216 from Fr.8 increased HIF-1α transactivation activity and UPR activation. Conclusion: We discovered promising compounds from Brazilian propolis for novel anti-cancer drug targeting tumor microenvironment. GPU-215 has inhibitory effect on HIF-1α expression and function, while GPU-216 increased HIF-1α transactivation and UPR activation. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 765.

Abstract 5194: Induction of Fyn via the Ras/PI3K pathway is necessary and sufficient for enhanced migration and invasion

Abstract Over-expression and activation of Src family kinases, particularly Fyn, is relatively frequent in human cancers. Fyn promotes cancer progression, tumor survival and carcinoma invasion, making it a potential molecular target for cancer therapeutics; however the mechanism of Fyn over-expression in cancers is not clear. Since activation of Ras oncogenes in human cancers is a very common oncogenic event, we explored if an active Ras oncogene could induce Fyn expression. Interestingly, retroviral transduction of the immortalized human keratinocyte cell line HaCaT with oncogenic H-Ras dramatically upregulated Fyn mRNA, protein, and activity (>100 fold mRNA induction, p<0.001). Src levels and kinase activity were not affected by H-Ras transduction. Furthermore, activation of Akt, but not MAPK or EGFR, was necessary and sufficient for induction of Fyn by H-Ras. The enhanced migration and invasion induced by H-Ras could be significantly blocked (70% reduction, p<0.0001) by Fyn specific siRNA knockdown or inhibition by PP2 (10 µM). In addition, expression of active Fyn in HaCaT cells was sufficient for increased migration or invasion of cells. These results implicate induction of Fyn in Ras-induced enhanced migration and invasion of cancer cells. Focal adhesion kinase (FAK) activation has been strongly linked with the Ras-mediated increased migratory phenotype of tumor cells. We found that Fyn was necessary and sufficient for Ras induced activation of FAK. In summary, we show that Fyn induction by oncogenic Ras/PI3K/Akt pathway can account for the elevated Src family kinase activity in cancers, and is a critical mediator of the Ras-stimulated invasive cell phenotype. These results have strong implications for the development of therapeutic strategies targeting Akt/Fyn pathway to block migration and invasion of tumor cells. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 5194.