Summary 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 cells 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 knock-in 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.

In multicellular organisms, communication between individual cells is essential for the regulation and coordination of complex cellular processes such as growth, differentiation, migration and apoptosis. The plethora of signal transduction networks mediating these biological processes is regulated in part by polypeptide growth factors that can generate signals by activating cell surface receptors either in paracrine or autocrine manner. The primary mediators of such physiological cell responses are receptor tyrosine kinases (RTKs) that couple ligand binding to downstream signalling cascades and gene transcription. Investigations over the past 18 years have revealed that RTKs are not only key regulators of normal cellular processes but are also critically involved in the development and progression of human cancers. Therefore, signalling pathways controlled by tyrosine kinases offer unique opportunities for pharmacological intervention. The aim of this review is to give a broad overview of RTK signalling involved in tumorigenesis and the possibility of target-selective intervention for anti-cancer therapy.

The recent completion of the human genome sequence has raised great hopes for the discovery of new breast cancer therapies based on newly-discovered genes linked to breast cancer development and progression. Here we describe breast cancer therapies that have emerged from gene-based scientific efforts over the past 20 years and that are now approved for clinical testing or treatment.

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According to this study, FGFR4 Arg388 genotype is a marker for breast cancer progression in patients with adjuvant systemic therapy, particularly chemotherapy, and thus may indicate therapy resistance.

After decades of rigorous investigations of chemotherapeutic cancer therapies, many cancers, including those of the head and neck, remain beyond our clinical ability to control them. From 3% to 5% of all patients initially cured of early-stage head and neck cancer will develop second primary tumors or local recurrences. 1 This phenomenon has been explained by the concept of field cancerization, which argues that certain risk factors such as alcohol and tobacco change the lining of the upper aerodigestive tract into a so-called condemned mucosa. In such a scenario, alcohol may represent the key risk factor for neoplastic transformation in the oral cavity, the oro-and hypopharynx. [2][3][4] An increasing amount of evidence suggests that alcohol intake and smoking play a synergistic role in the neoplastic progress.One of the most important achievements of molecular oncology has been the demonstration that cancer represents a genetic disease that begins with genetic damages in the genome of one cell in the form of point mutations, DNA rearrangement and gene amplification leading to the distortion of the expression and biochemical function of respective gene products. Growth factor receptors of the class I subfamily, which include the epidermal growth factor receptor (EGFR/HER1) and the related proteins HER2, HER3 and HER4, have shown that amplification or overexpression of those receptors, especially well documented for HER2 in patients with breast and ovarian cancers, plays an important role in carcinogenesis and tumor progression. [5][6][7][8] Multivariate survival analysis showed that HER2 amplification or overexpression is more predictive of clinical outcome than all other known prognosticators with the exception of positive lymph nodes. 9,10 These findings have validated the HER2 receptor as a target for therapeutic intervention. Moreover, recent clinical investigations have confirmed the benefit of antagonistic HER2 antibody therapy in breast cancer using herceptin. 11 Minute genetic changes such as point mutations have been found to cause constitutive activation of the HER2/neu kinase activity and to induce neoplastic disorders. 12 Similarly, the 2 amino acid substitutions Gly380Arg and Ala391Glu in the transmembrane domain of fibroblast growth factor receptor 3 (FGFR3) have been shown to be responsible for 2 forms of human dwarfism, namely, achondroplasia and morbus crouzon. [13][14][15] Other mutations in the FGFR3 gene have been associated with bladder and cervix cancer. 16 The FGFR signaling system is composed of 4 receptor tyrosine kinases (RTKs) and more than 20 known ligands and has been implicated in the regulation of a multitude of both physiologic and pathophysiologic processes, including migration, wound healing, angiogenesis and cancer. 17 More recently, we have identified a single nucleotide polymorphism (SNP) in codon 388 of the FGFR4 gene, which plays a pivotal role in the progression of breast cancer. This SNP is present at a significantly higher rate in breast cancer patients with early relap...

Purpose: Establishment of antiapoptotic signaling pathways in tumor cells is a major cause for the failure of chemotherapy against cancer.Toinvestigate the underlying mechanisms, we developed an experimentalapproach that is basedonthe genetic plasticity of cancer cells and the selectionfor cell survival on treatment with chemotherapeutic agents. Experimental Design: Gene expression changes of surviving cell clones were analyzed by macroarrays. Involvement of fibroblast growth factor receptor 4 (FGFR4) in antiapoptotic pathways was elucidated by apoptosis assays, small interfering RNA experiments, and an antagonistic antibody. Results:We show that FGFR4 gene expression is up-regulated in doxorubicin-treated, apoptosisresistant cancer cell clones. Ectopic expression of FGFR4 in cancer cells led to reduced apoptosis sensitivity on treatment with doxorubicin or cyclophosphamide, whereas knockdown of endogenous FGFR4 expression in breast cancer cell lines had the opposite effect. FGFR4 overexpression resulted in Bcl-xl up-regulation at both mRNA and proteinlevels. Knockdown of FGFR4 expression by small interfering RNA caused a decrease in phospho-extracellular signal-regulated kinase 1/2 levels and reduced Bcl-xl expression. Moreover, an antagonistic FGFR4 antibody suppressed the resistance of cancer cells with endogenous FGFR4 expression against apoptosis-inducing chemotherapeutic agents. Conclusion: Based on these findings, we propose an antiapoptotic signaling pathway that is initiatedby FGFR4 andregulatingthe expressionof Bcl-xl throughthemitogen-activatedproteinkinase cascade. Our findings are exemplary for a novel strategy toward the elucidation of diverse signaling pathways that define antiapoptotic potential in cancer cells.These observations open new avenues toward the diagnosis of chemoresistant tumors and therapies targeting FGFR4-overexpressing cancers.Breast cancer is the most frequent malignancy among women in the western world. 3,4 Although much effort has been invested into designing new therapies, classic chemotherapeutic agents such as doxorubicin (Adriamycin) are still widely employed in the clinic (1). Chemotherapeutic drugs are used as primary or adjuvant therapy with response rates from 60% to 100% (2, 3). A major problem of most of the current therapies are the sometimes severe side effects and the intrinsic or acquired drug resistance of cancer cells to these drugs, which lead to relapse and metastatic progression of the tumor. This is reflected by the decline in the response rates with second-line chemotherapy to 20% to 30% (4).Motivated by these facts, a comprehensive characterization of genes contributing to a drug resistance phenotype has been done in this study. Based on an approach of Hudziak et al. (5) and Abraham et al. (6), where tumor necrosis factor-a-resistant and Fas ligand-resistant cell clones were established, we respectively took advantage of the genomic instability of breast cancer cell lines to generate doxorubicin-resistant cell clones. When treated with chemothera...

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