Tumour metastasis is the primary cause of mortality in cancer patients and remains the key challenge for cancer therapy. New therapeutic approaches to block inhibitory pathways of the immune system ...have renewed hopes for the utility of such therapies. Here we show that genetic deletion of the E3 ubiquitin ligase Cbl-b (casitas B-lineage lymphoma-b) or targeted inactivation of its E3 ligase activity licenses natural killer (NK) cells to spontaneously reject metastatic tumours. The TAM tyrosine kinase receptors Tyro3, Axl and Mer (also known as Mertk) were identified as ubiquitylation substrates for Cbl-b. Treatment of wild-type NK cells with a newly developed small molecule TAM kinase inhibitor conferred therapeutic potential, efficiently enhancing anti-metastatic NK cell activity in vivo. Oral or intraperitoneal administration using this TAM inhibitor markedly reduced murine mammary cancer and melanoma metastases dependent on NK cells. We further report that the anticoagulant warfarin exerts anti-metastatic activity in mice via Cbl-b/TAM receptors in NK cells, providing a molecular explanation for a 50-year-old puzzle in cancer biology. This novel TAM/Cbl-b inhibitory pathway shows that it might be possible to develop a 'pill' that awakens the innate immune system to kill cancer metastases.
Receptor tyrosine kinases are a subclass of cell-surface growth-factor receptors with an intrinsic, ligand-controlled tyrosine-kinase activity. They regulate diverse functions in normal cells and ...have a crucial role in oncogenesis. Twenty years ago, the first primary structure of a receptor tyrosine kinase, the epidermal growth factor receptor, was elucidated. The characterization of both the molecular architecture of receptor tyrosine kinases and the main functions of these proteins and their ligands in tumorigenesis opened the door to a new era in molecular oncology and paved the way to the development of the first target-specific cancer therapeutics.
Chronic kidney disease (CKD) is a worldwide public health threat that increases risk of death due to cardiovascular complications, including left ventricular hypertrophy (LVH). Novel therapeutic ...targets are needed to design treatments to alleviate the cardiovascular burden of CKD. Previously, we demonstrated that circulating concentrations of fibroblast growth factor (FGF) 23 rise progressively in CKD and induce LVH through an unknown FGF receptor (FGFR)-dependent mechanism. Here, we report that FGF23 exclusively activates FGFR4 on cardiac myocytes to stimulate phospholipase Cγ/calcineurin/nuclear factor of activated T cell signaling. A specific FGFR4-blocking antibody inhibits FGF23-induced hypertrophy of isolated cardiac myocytes and attenuates LVH in rats with CKD. Mice lacking FGFR4 do not develop LVH in response to elevated FGF23, whereas knockin mice carrying an FGFR4 gain-of-function mutation spontaneously develop LVH. Thus, FGF23 promotes LVH by activating FGFR4, thereby establishing FGFR4 as a pharmacological target for reducing cardiovascular risk in CKD.
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•In the absence of α-klotho, FGF23 induces binding of FGFR4 to PLCγ•FGF23 activates calcineurin/NFAT signaling in cardiac myocytes via FGFR4•FGFR4 blockade protects CKD rats with high serum FGF23 from cardiac hypertrophy•Knockin mice carrying a FGFR4 gain-of-function mutation develop cardiac hypertrophy
Grabner et al. reveal that FGFR4 mediates the pro-hypertrophic cardiac effects of FGF23, a phosphate-regulating hormone elevated in patients with chronic kidney disease (CKD). Activation of FGFR4/calcineurin/NFAT signaling is sufficient to induce cardiac hypertrophy in mice, while FGFR4 blockade attenuates cardiac hypertrophy in a rat model of CKD.
Selective inhibition of protein tyrosine kinases is gaining importance as an effective therapeutic approach for the treatment of a wide range of human cancers. However, as extensively documented for ...the BCR-ABL oncogene in imatinib-treated leukaemia patients, clinical resistance caused by mutations in the targeted oncogene has been observed. Here, we look at how structural and mechanistic insights from imatinib-insensitive Bcr-Abl have been exploited to identify second-generation drugs that override acquired target resistance. These insights have created a rationale for the development of either multi-targeted protein kinase inhibitors or cocktails of selective antagonists as antitumour drugs that combine increased therapeutic potency with a reduced risk of the emergence of molecular resistance.
Abnormal accumulation and dysregulation of the epidermal growth factor receptor family member HER3 is associated with the development of various human cancers including those of the breast, lung, and ...ovary. We have previously shown that in melanoma HER3 is frequently overexpressed and is associated with poor prognosis. However, the importance of HER3 in colon cancer and its putative prognostic significance is still unknown.
HER3 expression was analyzed in primary colon tumors from 110 patients by immunohistochemistry and correlated with time of progression. Parallel to this, the influence of HER3 overexpression on cell proliferation, migration, invasion, and apoptosis was investigated in four different colon cancer cell lines including DLD-1, LoVo, CaCO2, and T-84.
HER3 was detected at high frequency and exclusively at the membrane of the primary tumors. Elevated HER3 expression levels may serve as a putative prognostic marker because it associates with cell proliferation and decreased time to disease progression. High HER3 protein expression as well as phosphorylation levels were detected in tested cells. HER3 downregulation by RNA interference abrogated cell proliferation, migration, and invasion. In addition, suppression of HER3 resulted in a G(2)-M cell-cycle arrest, induced apoptosis, and led to morphologic changes in colon cancer cell lines. Furthermore, application of a monoclonal antibody specific to the extracellular portion of the receptor reduced heregulin-β1-induced migration and invasion and also induced apoptosis in colon cancer cell lines.
We postulate that HER3 is critically involved in colon cancer progression and may serve as a novel target for therapeutic intervention.
•Nek9 depletion caused mitotic catastrophe by impairment of checkpoint and spindle dynamics.•Nek9 depletion induced cell death due to abnormal cell cycle in cancer cells but not in normal cells.•We ...propose that Nek9 inhibition represents a novel anti-cancer strategy.
NEK9 is known to play a role in spindle assembly and in the control of centrosome separation, but the consequences of NEK9 targeting in cancer cells remain to be elucidated. In this study, we used siRNA to investigate the consequences of targeting NEK9 in glioblastoma and kidney cancer cells as a first step in assessing its potential as an anti-cancer therapeutic target. Live cell imaging revealed that NEK9 depletion of U1242 glioblastoma and Caki2 kidney carcinoma cells resulted in failure of cytokinesis. Interestingly, NEK9-depleted Caki2 cells overrode mitosis under incorrect chromosome alignment and were converted to a micronucleated phenotype, leading to cell death. Whereas, the RPE1 normal epithelium cell line was refractory to abnormal mitosis upon NEK9 knockdown. Nocodazole-induced mitotic arrest was compromised after NEK9 depletion, indicating that NEK9 has an important role in mitotic checkpoint system. Taken together, we propose that NEK9 inhibition represents a novel anti-cancer strategy by induction of mitotic catastrophe via impairment of spindle dynamics, cytokinesis and mitotic checkpoint control.
Exceptional advances in molecular biology and genetic research have expedited cancer drug development tremendously. The declared paradigm is the development of 'personalized and tailored drugs' that ...precisely target the specific molecular defects of a cancer patient. It is therefore appropriate to revisit the intellectual foundations of the development of such agents, as many have shown great clinical success. One hundred years ago, Paul Ehrlich, the founder of chemotherapy, received the Nobel Prize for Physiology or Medicine. His postulate of creating 'magic bullets' for use in the fight against human diseases inspired generations of scientists to devise powerful molecular cancer therapeutics.
Signalling through G-protein-coupled receptors (GPCRs) and receptor tyrosine kinases (RTK) is involved in the regulation of essential cellular processes and its deregulation is associated with ...tumorigenesis in vitro and in vivo. We investigated pathophysiological processes that are regulated by GPCR pathways in human kidney and bladder cancer cell lines. Our results show that GPCR ligands induce tyrosine phosphorylation of the epidermal growth factor receptor (EGFR) as well as downstream signalling events such as recruitment of the adapter protein Shc and activation of the mitogen-activated protein kinases (MAPK) ERK1/2, JNK and p38. Moreover, we report that the EGFR transactivation signal involves the EGFR ligands amphiregulin, HB-EGF and TGFalpha as well as the metalloproteinases ADAM 10, 15 and 17, depending on the cellular system. Finally, we demonstrate that EGFR transactivation is part of a regulatory system that modulates the migratory and invasive behaviour of kidney and bladder cancer cells. In conclusion, our findings demonstrate that metalloproteinase-mediated transactivation of the EGFR is a key mechanism of the cellular signalling network that promotes MAPK activation as well as tumour cell migration and invasion in response to a variety of physiologically relevant GPCR ligands, and therefore represents a novel target for cancer intervention strategies.
Protein Tyrosin Kinase 7 (PTK7) is upregulated in several human cancers; however, its clinical implication in breast cancer (BC) and lymph node (LN) is still unclear. In order to investigate the ...function of PTK7 in mediating BC cell motility and invasivity, PTK7 expression in BC cell lines was determined. PTK7 signaling in highly invasive breast cancer cells was inhibited by a dominant-negative PTK7 mutant, an antibody against the extracellular domain of PTK7, and siRNA knockdown of PTK7. This resulted in decreased motility and invasivity of BC cells. We further examined PTK7 expression in BC and LN tissue of 128 BC patients by RT-PCR and its correlation with BC related genes like HER2, HER3, PAI1, MMP1, K19, and CD44. Expression profiling in BC cell lines and primary tumors showed association of PTK7 with ER/PR/HER2-negative (TNBC-triple negative BC) cancer. Oncomine data analysis confirmed this observation and classified PTK7 in a cluster with genes associated with agressive behavior of primary BC. Furthermore PTK7 expression was significantly different with respect to tumor size (ANOVA, p = 0.033) in BC and nodal involvement (ANOVA, p = 0.007) in LN. PTK7 expression in metastatic LN was related to shorter DFS (Cox Regression, p = 0.041). Our observations confirmed the transforming potential of PTK7, as well as its involvement in motility and invasivity of BC cells. PTK7 is highly expressed in TNBC cell lines. It represents a novel prognostic marker for BC patients and has potential therapeutic significance.
The receptor tyrosine kinase Axl has recently been identified as a critical element in the invasive properties of glioma cell lines. However, the effect of Axl and its ligand growth arrest--specific ...gene 6 (Gas6) in human gliomas is still unknown.
Axl and Gas6 expression was studied in 42 fresh-frozen and 79 paraffin-embedded glioma specimens by means of reverse transcription-PCR and immunohistochemistry. The prognostic value of Axl and Gas6 expression was evaluated using a population-based tissue microarray derived from a cohort of 55 glioblastoma multiforme (GBM) patients.
Axl and Gas6 were detectable in gliomas of malignancy grades WHO 2 to 4. Moderate to high Axl mRNA expression was found in 61%, Axl protein in 55%, Gas6 mRNA in 81%, and Gas6 protein in 74% of GBM samples, respectively. GBM patients with high Axl expression and Axl/Gas6 coexpression showed a significantly shorter time to tumor progression and an association with poorer overall survival. Comparative immunohistochemical studies showed that Axl staining was most pronounced in glioma cells of pseudopalisades and reactive astrocytes. Additionally, Axl/Gas6 coexpression was observed in glioma cells and tumor vessels. In contrast, Axl staining was not detectable in nonneoplastic brain tissue and Gas6 was strongly expressed in neurons.
In human gliomas, Axl and Gas6 are frequently overexpressed in both glioma and vascular cells and predict poor prognosis in GBM patients. Our results indicate that specific targeting of the Axl/Gas6 signaling pathway may represent a potential new approach for glioma treatment.
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