CIP4 and Src in Promoting the Migration and Invasion of Breast Cancers

Cellular invasion represents a critical early step in the metastatic cascade, and many proteins have been identified as part of an “invasive signature.” The non-receptor tyrosine kinase Src is commonly upregulated in breast cancers, often in conjunction with overexpression of EGFR. Signaling from this pathway stimulates cell proliferation, migration, and invasion and frequently involves proteins that regulate the cytoskeleton. My data demonstrates that inhibition of Src, using the small-molecule inhibitor dasatinib, impairs cellular migration and invasion. Furthermore, Src inhibition sensitizes the cells to the effects of the chemotherapeutic doxorubicin resulting in dramatic, synergistic inhibition of proliferation with combination treatments. The Src-targeted protein CIP4 (Cdc42-interacting protein 4) associates with curved plasma membranes to scaffold complexes of Cdc42 and N-WASp. In these experiments, I show that CIP4 overexpression correlates with triple-negative biomarker status, cellular migration, and invasion of (breast cancer cells. Inhibition of CIP4 expression significantly decreases migration and invasion. Furthermore, I demonstrate the novel finding that CIP4 localizes to invadopodia, which are finger-like projections of the actin cytoskeleton that are associated with matrix degradation and cellular invasion. Depletion of CIP4 in invasive cells impairs the formation of invadopodia and the degradation of gelatin. Therefore, CIP4 is a critical component of the invasive phenotype acquired by human breast cancer cells. In this body of work, I propose a model in which CIP4 promotes actin polymerization by stabilizing the active conformation of N-WASp. CIP4 and N-WASp are both phosphorylated by Src, implicating this pathway in Src-dependent cytoskeletal rearragement. This represents a novel role for F-BAR proteins in migration and invasion.

Study of the cellular mechanism of Sunitinib mediated inactivation of activated hepatic stellate cells and its implications in angiogenesis

The development of hepatocellular carcinomas from malignant hepatocytes is frequently associated with intra- and peritumoral accumulation of connective tissue arising from activated hepatic stellate cells (HSC). Inhibition of receptor tyrosine kinase (RTK) signaling showed promise in the treatment of hepatocellular carcinoma. However, there is a lack of knowledge about the effects of RTK inhibitors on the tumor supportive cells. We performed in vitro experiments to study whether Sunitinib, a platelet-derived growth factor (PDGF) and vascular endothelial growth factor (VEGF) RTKs' inhibitor, could block both activated HSC functions and angiogenesis and thus prevent the progression of cirrhotic liver to hepatocellular carcinoma. In immortalized human activated HSC LX-2, treatment with Sunitinib 100 nM blocked collagen synthesis by 47%, as assessed by Sirius Red staining, attenuated HSC contraction by 65%, and reduced cell migration by 28% as evaluated using a Boyden's chamber, without affecting cell viability, measured by Trypan blue staining, and apoptosis, measured by propidium iodide (PI) incorporation assay. Our data revealed that Sunitinib treatment blocked the transdifferentiation of primary human HSC (hHSC) to activated myofibroblast-like cells by 65% without affecting hHSC apoptosis and migration. In in vitro angiogenic assays, Sunitinib 100 nM reduced endothelial cells (EC) ring formation by 46% and tube formation by 68%, and decreased vascular sprouting in aorta ring assay and angiogenesis in vascular bed of chick embryo. In conclusion, the present study demonstrates that the RTK inhibitor Sunitinib blocks the activation of HSC and angiogenesis suggesting its potential as a drug candidate in pathological conditions like liver fibrosis and hepatocellular carcinoma.

Biological, diagnostic and therapeutic relevance of the MET receptor signaling in head and neck cancer.

Head and neck cancer constitutes the 6th most common malignancy worldwide and affects the crucial anatomical structures and physiological functions of the upper aerodigestive tract. Classical therapeutic strategies such as surgery and radiotherapy carry substantial toxicity and functional impairment. Moreover, the loco-regional control rates as well as overall survival still need to be improved in subgroups of patients. The scatter-factor/hepatocyte growth factor receptor tyrosine kinase MET is an established effector in the promotion, maintenance and progression of malignant transformation in a wide range of human malignancies, and has been gaining considerable interest in head and neck cancer over the last 15 years. Aberrant MET activation due to overexpression, mutations, tumor-stroma paracrine loops, and cooperative/redundant signaling has been shown to play prominent roles in epithelial-to-mesenchymal transition, angiogenesis, and responses to anti-cancer therapeutic modalities. Accumulating preclinical and translational evidence highly supports the increasing interest of MET as a biomarker for lymph node and distant metastases, as well as a potential marker of stratification for responses to ionizing radiation. The relevance of MET as a therapeutic molecular target in head and neck cancer described in preclinical studies remains largely under-evaluated in clinical trials, and therefore inconclusive. Also in the context of anti-cancer targeted therapy, a large body of preclinical data suggests a central role for MET in treatment resistance towards multiple therapeutic modalities in malignancies of the head and neck region. These findings, as well as the potential use of combination therapies including MET inhibitors in these tumors, need to be further explored.

Ceramide kinase contributes to proliferation but not to prostaglandin E2 formation in renal mesangial cells and fibroblasts

Background/Aims: Ceramide kinase (CerK) catalyzes the generation of the sphingolipid ceramide-1-phosphate (C1P) which regulates various cellular functions including cell growth and death, and inflammation. Here, we used a novel catalytic inhibitor of CerK, NVP-231, and CerK knockout cells to investigate the contribution of CerK to proliferation and inflammation in renal mesangial cells and fibroblasts. Methods: Cells were treated with NVP-231 and [3H]-thymidine incorporation into DNA, [3H]-arachidonic acid release, prostaglandin E2 (PGE2) synthesis, cell cycle distribution, and apoptosis were determined. Results: Treatment of rat mesangial cells and mouse renal fibroblasts with NVP-231 decreased DNA synthesis, but not of agonist-stimulated arachidonic acid release or PGE2 synthesis. Similarly, proliferation but not arachidonic acid release or PGE2 synthesis was reduced in CERK knockout renal fibroblasts. The anti-proliferative effect of NVP-231 on mesangial cells was due to M phase arrest as determined using the mitosis markers phospho-histone H3, cdc2 and polo-like kinase-1, and induction of apoptosis. Moreover, loss of CerK sensitized cells towards stress-induced apoptosis. Conclusions: Our data demonstrate that CerK induces proliferation but not PGE2 formation of renal mesangial cells and fibroblasts, and suggest that targeted CerK inhibition has potential for treating mesangioproliferative kidney diseases.

Nck-interacting Ste20 kinase couples Eph receptors to c-Jun N-terminal kinase and integrin activation.

The mammalian Ste20 kinase Nck-interacting kinase (NIK) specifically activates the c-Jun amino-terminal kinase (JNK) mitogen-activated protein kinase module. NIK also binds the SH3 domains of the SH2/SH3 adapter protein Nck. To determine whether Nck functions as an adapter to couple NIK to a receptor tyrosine kinase signaling pathway, we determined whether NIK is activated by Eph receptors (EphR). EphRs constitute the largest family of receptor tyrosine kinases (RTK), and members of this family play important roles in patterning of the nervous and vascular systems. In this report, we show that NIK kinase activity is specifically increased in cells stimulated by two EphRs, EphB1 and EphB2. EphB1 kinase activity and phosphorylation of a juxtamembrane tyrosine (Y594), conserved in all Eph receptors, are both critical for NIK activation by EphB1. Although pY594 in the EphB1R has previously been shown to bind the SH2 domain of Nck, we found that stimulation of EphB1 and EphB2 led predominantly to a complex between NIK/Nck, p62(dok), RasGAP, and an unidentified 145-kDa tyrosine-phosphorylated protein. Tyrosine-phosphorylated p62(dok) most probably binds directly to the SH2 domain of Nck and RasGAP and indirectly to NIK bound to the SH3 domain of Nck. We found that NIK activation is also critical for coupling EphB1R to biological responses that include the activation of integrins and JNK by EphB1. Taken together, these findings support a model in which the recruitment of the Ste20 kinase NIK to phosphotyrosine-containing proteins by Nck is an important proximal step in the signaling cascade downstream of EphRs.

Interplay between receptor tyrosine kinases and hypoxia signaling in cancer.

Deregulated signaling via receptor tyrosine kinase (RTK) pathways is prevalent in numerous types of human cancers and is commonly correlated with worst prognosis, resistance to various treatment modalities and increased mortality. Likewise, hypoxic tumors are often manifested by aggressive mode of growth and progression following an adaptive genetic reprogramming with consequent transcriptional activation of genes encoding proteins, which support tumor survival under low oxygen-related conditions. Consequently, both the hypoxia-inducible factor (HIF) system, which is the major mediator of hypoxia-related signaling, and numerous RTK systems are considered critical molecular targets in current cancer therapy. It is now evident that there is an intricate molecular crosstalk between RTKs and hypoxia-related signaling in the sense that hypoxia can activate expression of particular RTKs and/or their corresponding ligands, while some RTK systems have been shown to trigger activation of the HIF machinery. Moreover, signaling regulation of some RTK systems under hypoxic conditions has also been documented to take place in a HIF-independent manner. With this review we aim at overviewing the most current observations on that topic and highlight the importance of the potential co-drugging the HIF system along with particular relevant RTKs for better tumor growth control.

A frequent hypofunctional IRAK2 variant is associated with reduced spontaneous hepatitis C virus clearance.

UNLABELLED Patients carrying very rare loss-of-function mutations in interleukin-1 receptor-associated kinase 4 (IRAK4), a critical signaling mediator in Toll-like receptor signaling, are severely immunodeficient, highlighting the paramount role of IRAK kinases in innate immunity. We discovered a comparatively frequent coding variant of the enigmatic human IRAK2, L392V (rs3844283), which is found homozygously in ∼15% of Caucasians, to be associated with a reduced ability to induce interferon-alpha in primary human plasmacytoid dendritic cells in response to hepatitis C virus (HCV). Cytokine production in response to purified Toll-like receptor agonists was also impaired. Additionally, rs3844283 was epidemiologically associated with a chronic course of HCV infection in two independent HCV cohorts and emerged as an independent predictor of chronic HCV disease. Mechanistically, IRAK2 L392V showed intact binding to, but impaired ubiquitination of, tumor necrosis factor receptor-associated factor 6, a vital step in signal transduction. CONCLUSION Our study highlights IRAK2 and its genetic variants as critical factors and potentially novel biomarkers for human antiviral innate immunity.

Emodin, a tyrosine kinase inhibitor, and human cancer

Many human diseases, including cancers, result from aberrations of signal transduction pathways. The recent understanding of the molecular biochemistry of signal transduction in normal and transformed cells enable us to have a better insight about cancer and design new drugs to target this abnormal signaling in the cancer cells. Tyrosine kinase pathway plays a very important role in normal and cancer cells. Enhanced activity of tyrosine kinases has been associated with many human cancer types. Therefore, identifying the type of tyrosine kinases involved in a particular cancer type and blocking these tyrosine kinase pathways may provide a way to treat cancer. Receptor tyrosine kinase expression, namely epidermal growth factor receptor (EGFR) family, was examined in the oral squamous cell carcinoma patients. The expression levels of different members of the EGFR family were found to be significantly associated with shorter patients' survival. Combining EGFR, HER-2/neu, and HER-3 expression can significantly improve the predicting power. The effect of emodin, a tyrosine kinase inhibitor, on these receptors in head and neck squamous cell carcinoma cell lines was examined. Emodin was found to suppress the tyrosine phosphorylation of HER-2/neu and EGF-induced tyrosine phosphorylation of EGFR. Emodin also induced apoptosis and downregulated the expression of anti-apoptotic protein bcl-2 in oral squamous cell carcinoma cells. It is known that tyrosine kinase pathways are involved in estrogen receptor signaling pathway. Therefore, the effects of inhibiting the tyrosine kinase pathway in estrogen receptor-positive breast cancers was studied. Emodin was found to act similarly to antiestrogens, capable of inhibiting estrogen-stimulated growth and DNA synthesis, and the phosphorylation of Rb protein. Interestingly, emodin, and other tyrosine kinase inhibitors, such as RG 13022 and genistein, depleted cellular levels of estrogen receptor protein. Emodin-induced depletion of estrogen receptor was mediated by the proteasome degradation pathway. In summary, we have demonstrated that tyrosine kinase pathways play an important role in oral squamous cell carcinoma and estrogen receptor-positive breast cancer. Targeting the tyrosine kinases by inhibitors, such as emodin, may provide a potential way to treat the cancer patients. ^

The transcriptional regulation of the {\it neu\/} gene: Examples of activation, repression, and cell-specific expression

The neu oncogene encodes a growth factor receptor-like protein, p185, with an intrinsic tyrosine kinase activity. A single point mutation, an A to T transversion resulting in an amino acid substitution from valine to glutamic acid, in the transmembrane domain of the rat neu gene was found to be responsible for the transforming and tumorigenic phenotype of the cells that carry it. In contrast, the human proto-neu oncogene is frequently amplified in tumors and cell lines derived from tumors and the human neu gene overexpression/amplification in breast and ovarian cancers is known to correlate with poor patient prognosis. Examples of the human neu gene overexpression in the absence of gene amplification have been observed, which may suggest the significant role of the transcriptional and/or post-transcriptional control of the neu gene in the oncogenic process. However, little is known about the transcriptional mechanisms which regulate the neu gene expression. In this study, three examples are presented to demonstrate the positive and negative control of the neu gene expression.^ First, by using band shift assays and methylation interference analyses, I have identified a specific protein-binding sequence, AAGATAAAACC ($-$466 to $-$456), that binds a specific trans-acting factor termed RVF (for EcoRV factor on the neu promoter). The RVF-binding site is required for maximum transcriptional activity of the rat neu promoter. This same sequence is also found in the corresponding regions of both human and mouse neu promoters. Furthermore, this sequence can enhance the CAT activity driven by a minimum promoter of the thymidine kinase gene in an orientation-independent manner, and thus it behaves as an enhancer. In addition, Southwestern (DNA-protein) blot analysis using the RVF-binding site as a probe points to a 60-kDa polypeptide as a potential candidate for RVF.^ Second, it has been reported that the E3 region of adenovirus 5 induces down-regulation of epidermal growth factor (EGF) receptor through endocytosis. I found that the human neu gene product, p185, (an EGF receptor-related protein) is also down-regulated by adenovirus 5, but via a different mechanism. I demonstrate that the adenovirus E1a gene is responsible for the repression of the human neu gene at the transcriptional level.^ Third, a differential expression of the neu gene has been found in two cell model systems: between the mouse fibroblast Swiss-Webster 3T3 (SW3T3) and its variant NR-6 cells; and between the mouse liver tumor cell line, Hep1-a, and the mouse pancreas tumor cell line, 266-6. Both NR-6 and 266-6 cell lines are not able to express the neu gene product, p185. I demonstrate that, in both cases, the transcriptional repression of the neu gene may account for the lack of the p185 expression in these two cell lines. ^

Biological effects of PEA3 expression in {\it HER-2\/}/{\it neu\/}-overexpressing human cancer cells and the molecular mechanisms of PEA3-mediated transcriptional repression on {\it HER-2\/}/{\it neu\/}

HER-2/neu is a receptor tyrosine kinase highly homologous with epidermal growth factor receptor. Overexpression and/or amplification of HER-2/neu has been implicated in the genesis of a number of human cancers, especially breast and ovarian cancers. Transcriptional upregulation has been shown to contribute significantly to the overexpression of this gene. Studies on the transcriptional regulation of HER-2/neu gene are important for understanding the mechanism of cell transformation and developing the therapeutic strategies to block HER-2/neu-mediated cancers. PEA3 is a DNA binding transcriptional factor and its consensus sequence exists on the HER-2/neu promoter. To examine the role of PEA3 in HER-2/neu expression and cell transformation, we transfected PEA3 into the human breast and ovarian cancer cells that overexpress HER-2/neu and showed that PEA3 dramatically represses HER-2/neu transcription. PEA3 suppresses the oncogenic neu-mediated transformation in mouse fibroblast NIH 3T3 cells. Expression of PEA3 selectively blocks the growth of human cancer cells that overexpress HER-2/neu and inhibits their colony formation. It does not occur in the cancer cells expressing basal level of HER-2/neu. Further studies in the orthotopic ovarian cancer model demonstrated that expression of PEA3 preferentially inhibits growth and tumor development of human cancer cells that overexpress HER-2/neu, the tumor-bearing mice survived significantly longer if treated by injection of the PEA3-liposome complex intraperitoneally. Immunoblotting and immunohistochemical analysis of the tumor tissues indicated that PEA3 mediates the tumor suppression activity through targeting HER-2/neu-p185. Thus, PEA3 is a negative regulator of HER-2/neu gene expression and functions as a tumor suppressor gene in the HER-2/neu-overexpressing human cancer cells.^ The molecular mechanisms of PEA3 mediated transcriptional repression were investigated. PEA3 binds specifically at the PEA3 site on HER-2/neu promoter and this promoter-binding is required for the PEA3 mediated transcriptional repression. Mutation of the PEA3 binding site on HER-2/neu promoter causes decreased transcriptional activity, indicating that the PEA3 binding site is an enhancer-like element in the HER-2/neu-overexpressing cells. We therefore hypothesized that in the HER-2/neu-overexpressing cells, PEA3 competes with a transactivator for binding to the PEA3 site, preventing the putative factor from activating the transcription of HER-2/neu. This hypothesis was supported by the data which demonstrate that PEA3 competes with another nuclear protein for binding to the HER-2/neu promoter in vitro, and expression of a truncated protein which encodes the DNA binding domain of PEA3 is sufficient to repress HER-2/neu transcription in the HER-2/neu-overexpressing human cancer cells. ^

Papel de la interleuquina 23 en la diferenciación hacia Th17

The incidence of inflammatory and autoimmune diseases has increased among developed countries in the past 30 years, creating a demand for the development of effective and economic therapies for these diseases. Interleukin 23 (IL-23) is a pro-inflammatory cytokine whose increased production has been shown to play a key role in the establishment and maintenance of inflammatory and autoimmune diseases in different murine models such as inflammatory bowel disease, psoriasis and experimental autoimmune encephalomyelitis. More importantly, increased levels of IL-23 have been found in biopsies from patients with Crohn’s disease and ulcerative colitis, and psoriasis. The pathological consequences of excessive IL-23 signalling have been linked to its ability to promote the production of interleukin 17 (IL-17), particularly in the subpopulation of CD4 T cells Th17. However, the precise molecular mechanisms by which IL-23 sustains the Th17 response and induces pathogenic effector functions in these cells remain largely unknown. The global objective of the experiments carried out in this work was to determine the effect of IL-23 on the proliferation, survival and IL-17 and interferon gamma (IFN-ɣ) production in Th17 cells. These experiments have shown that IL-23 does not promote proliferation or survival of in vitro generated Th17 cells, and that there is no difference in the production of IL -17 in the absence or presence of IL -23. The IL-23 receptor, like other cytokine receptors, lacks intrinsic enzymatic activity. Instead, IL-23 receptor associates with members of the Janus tyrosine kinase family (Jaks). Cytokine binding to a Jak-associated receptor triggers the activation of the Signal Transducers and Activators of Transcription (STAT) family of transcription factors. Previous work indicated that the IL-23 receptor complex is associated with the tyrosine kinases Jak2 and Tyk2 that promote STAT3 phosphorylation. Subsequent studies showed that IL23 activation of STAT3 induces the expression of the transcription factor RORγt, which is crucial for IL-17 production. This work has explored the IL-23 signalling cascade, determining the optimal conditions for STAT3 activation and demonstrating the activation of other transcription factors such as STAT4, STAT5 and STAT1 that contribute to IL-23-mediated signalling pathways.

Plasmodium falciparum domain mediating adhesion to chondroitin sulfate A: A receptor for human placental infection

Malaria during the first pregnancy causes a high rate of fetal and neonatal death. The decreasing susceptibility during subsequent pregnancies correlates with acquisition of antibodies that block binding of infected red cells to chondroitin sulfate A (CSA), a receptor for parasites in the placenta. Here we identify a domain within a particular Plasmodium falciparum erythrocyte membrane protein 1 that binds CSA. We cloned a var gene expressed in CSA-binding parasitized red blood cells (PRBCs). The gene had eight receptor-like domains, each of which was expressed on the surface of Chinese hamster ovary cells and was tested for CSA binding. CSA linked to biotin used as a probe demonstrated that two Duffy-binding-like (DBL) domains (DBL3 and DBL7) bound CSA. DBL7, but not DBL3, also bound chondroitin sulfate C (CSC) linked to biotin, a negatively charged sugar that does not support PRBC adhesion. Furthermore, CSA, but not CSC, blocked the interaction with DBL3; both CSA and CSC blocked binding to DBL7. Thus, only the DBL3 domain displays the same binding specificity as PRBCs. Because protective antibodies present after pregnancy block binding to CSA of parasites from different parts of the world, DBL-3, although variant, may induce cross-reactive immunity that will protect pregnant women and their fetuses.

Activation of the c-Jun N-terminal kinase pathway by a novel protein kinase related to human germinal center kinase

The c-Jun N-terminal kinase (JNK), or stress-activated protein kinase plays a crucial role in cellular responses stimulated by environmental stress and proinflammatory cytokines. However, the mechanisms that lead to the activation of the JNK pathway have not been elucidated. We have isolated a cDNA encoding a novel protein kinase that has significant sequence similarities to human germinal center kinase (GCK) and human hematopoietic progenitor kinase 1. The novel GCK-like kinase (GLK) has a nucleotide sequence that encodes an ORF of 885 amino acids with 11 kinase subdomains. Endogenous GLK could be activated by UV radiation and proinflammatory cytokine tumor necrosis factor α. When transiently expressed in 293 cells, GLK specifically activated the JNK, but not the p42/44MAPK/extracellular signal-regulated kinase or p38 kinase signaling pathways. Interestingly, deletion of amino acids 353–835 in the putative C-terminal regulatory region, or mutation of Lys-35 in the putative ATP-binding domain, markedly reduced the ability of GLK to activate JNK. This result indicates that both kinase activity and the C-terminal region of GLK are required for maximal activation of JNK. Furthermore, GLK-induced JNK activation could be inhibited by a dominant-negative mutant of mitogen-activated protein kinase kinase kinase 1 (MEKK1) or mitogen-activated protein kinase kinase 4/SAPK/ERK kinase 1 (SEK1), suggesting that GLK may function upstream of MEKK1 in the JNK signaling pathway.

A transformation-associated complex involving tyrosine kinase signal adapter proteins and caldesmon links v-ErbB signaling to actin stress fiber disassembly

The avian erythroblastosis viral oncogene (v-erbB) encodes a receptor tyrosine kinase that possesses sarcomagenic and leukemogenic potential. We have expressed transforming and nontransforming mutants of v-erbB in fibroblasts to detect transformation-associated signal transduction events. Coimmunoprecipitation and affinity chromatography have been used to identify a transformation-associated, tyrosine phosphorylated, multiprotein complex. This complex consists of Src homologous collagen protein (Shc), growth factor receptor binding protein 2 (Grb2), son of sevenless (Sos), and a novel tyrosine phosphorylated form of the cytoskeletal regulatory protein caldesmon. Immunofluorescence localization studies further reveal that, in contrast to the distribution of caldesmon along actin stress fibers in normal fibroblasts, caldesmon colocalizes with Shc in plasma membrane blebs in transformed fibroblasts. This colocalization of caldesmon and Shc correlates with actin stress fiber disassembly and v-erbB-mediated transformation. The tyrosine phosphorylation of caldesmon, and its association with the Shc–Grb2–Sos signaling complex directly links tyrosine kinase oncogenic signaling events with cytoskeletal regulatory processes, and may define one mechanism regulating actin stress fiber disassembly in transformed cells.

An Eph receptor regulates integrin activity through R-Ras

The ability of integrins to mediate cell attachment to extracellular matrices and to blood proteins is regulated from inside the cell. Increased ligand-binding activity of integrins is critical for platelet aggregation upon blood clotting and for leukocyte extravasation to inflamed tissues. Decreased adhesion is thought to promote tumor cell invasion. R-Ras, a small intracellular GTPase, regulates the binding of integrins to their ligands outside the cell. Here we show that the Eph receptor tyrosine kinase, EphB2, can control integrin activity through R-Ras. Cells in which EphB2 is activated become poorly adherent to substrates coated with integrin ligands, and a tyrosine residue in the R-Ras effector domain is phosphorylated. The R-Ras phosphorylation and loss of cell adhesion are causally related, because forced expression of an R-Ras variant resistant to phosphorylation at the critical site made cells unresponsive to the anti-adhesive effect of EphB2. This is an unusual regulatory pathway among the small GTPases. Reduced adhesiveness induced through the Eph/R-Ras pathway may explain the repulsive effect of the Eph receptors in axonal pathfinding and may facilitate tumor cell invasion and angiogenesis.