FGFR3 mutations in prostate cancer: association with low-grade tumors

Futibatinib, an Irreversible FGFR1-4 Inhibitor for the Treatment of FGFR-Aberrant Tumors

Fibroblast growth factor receptors (FGFR) are emerging as an important therapeutic target for patients with advanced, refractory cancers. Most selective FGFR inhibitors under investigation show reversible binding, and their activity is limited by acquired drug resistance. This review summarizes the preclinical and clinical development of futibatinib, an irreversible FGFR1-4 inhibitor. Futibatinib stands out among FGFR inhibitors because of its covalent binding mechanism and low susceptibility to acquired resistance. Preclinical data indicated robust activity of futibatinib against acquired resistance mutations in the FGFR kinase domain. In early-phase studies, futibatinib showed activity in cholangiocarcinoma, and gastric, urothelial, breast, central nervous system, and head and neck cancers harboring various FGFR aberrations. Exploratory analyses indicated clinical benefit with futibatinib after prior FGFR inhibitor use. In a pivotal phase II trial, futibatinib demonstrated durable objective responses (42% objective response rate) and tolerability in previously treated patients with advanced intrahepatic cholangiocarcinoma harboring FGFR2 fusions or rearrangements. A manageable safety profile was observed across studies, and patient quality of life was maintained with futibatinib treatment in patients with cholangiocarcinoma. Hyperphosphatemia, the most common adverse event with futibatinib, was well managed and did not lead to treatment discontinuation. These data show clinically meaningful benefit with futibatinib in FGFR2-rearrangement-positive cholangiocarcinoma and provide support for further investigation of futibatinib across other indications. Future directions for this agent include elucidating mechanisms of resistance and exploration of combination therapy approaches.

Prostate Cancer: Advances in Genetic Testing and Clinical Implications

The demand for genetic testing (GT) for prostate cancer (PCa) is expanding, but there is limited knowledge about the genetic counseling (GC) needs of men. A strong-to-moderate inherited genetic predisposition causes approximately 5–20% of prostate cancer (PCa). In men with prostate cancer, germline testing may benefit the patient by informing treatment options, and if a mutation is noticed, it may also guide screening for other cancers and have family implications for cascade genetic testing (testing of close relatives for the same germline mutation). Relatives with the same germline mutations may be eligible for early cancer detection strategies and preventive measures. Cascade family testing can be favorable for family members, but it is currently unutilized, and strategies to overcome obstacles like knowledge deficiency, family communication, lack of access to genetic services, and testing expenses are needed. In this review, we will look at the genetic factors that have been linked to prostate cancer, as well as the role of genetic counseling and testing in the early detection of advanced prostate cancer.

Drug Conjugation via Maleimide-Thiol Chemistry Does Not Affect Targeting Properties of Cysteine-Containing Anti-FGFR1 Peptibodies

With a wide range of available cytotoxic therapeutics, the main focus of current cancer research is to deliver them specifically to the cancer cells, minimizing toxicity against healthy tissues. Targeted therapy utilizes different carriers for cytotoxic drugs, combining a targeting molecule, typically an antibody, and a highly toxic payload. For the effective delivery of such cytotoxic conjugates, a molecular target on the cancer cell is required. Various proteins are exclusively or abundantly expressed in cancer cells, making them a possible target for drug carriers. Fibroblast growth factor receptor 1 (FGFR1) overexpression has been reported in different types of cancer, but no FGFR1-targeting cytotoxic conjugate has been approved for therapy so far. In this study, the FGFR1-targeting peptide previously described in the literature was reformatted into a peptibody–peptide fusion with the fragment crystallizable (Fc) domain of IgG1. PeptibodyC19 can be effectively internalized into FGFR1-overexpressing cells and does not induce cells’ proliferation. The main challenge for its use as a cytotoxic conjugate is a cysteine residue located within the targeting peptide. A standard drug-conjugation strategy based on the maleimide–thiol reaction involves modification of cysteines within the Fc domain hinge region. Applied here, however, may easily result in the modification of the targeting peptide with the drug, limiting its affinity to the target and therefore the potential for specific drug delivery. To investigate if this is the case, we have performed conjugation reactions with different auristatin derivatives (PEGylated and unmodified) under various conditions. By controlling the reduction conditions and the type of cytotoxic payload, different numbers of cysteines were substituted, allowing us to avoid conjugating the drug to the targeting peptide, which could affect its binding to FGFR1. The optimized protocol with PEGylated auristatin yielded doubly substituted peptibodyC19, showing specific cytotoxicity toward the FGFR1-expressing lung cancer cells, with no effect on cells with low FGFR1 levels. Indeed, additional cysteine poses a risk of unwanted modification, but changes in the type of cytotoxic payload and reaction conditions allow the use of standard thiol–maleimide-based conjugation to achieve standard Fc hinge region cysteine modification, analogously to antibody–drug conjugates.

Exploring the FGF/FGFR System in Ocular Tumors: New Insights and Perspectives

Ocular tumors are a family of rare neoplasms that develop in the eye. Depending on the type of cancer, they mainly originate from cells localized within the retina, the uvea, or the vitreous. Even though current treatments (e.g., radiotherapy, transpupillary thermotherapy, cryotherapy, chemotherapy, local resection, or enucleation) achieve the control of the local tumor in the majority of treated cases, a significant percentage of patients develop metastatic disease. In recent years, new targeting therapies and immuno-therapeutic approaches have been evaluated. Nevertheless, the search for novel targets and players is eagerly required to prevent and control tumor growth and metastasis dissemination. The fibroblast growth factor (FGF)/FGF receptor (FGFR) system consists of a family of proteins involved in a variety of physiological and pathological processes, including cancer. Indeed, tumor and stroma activation of the FGF/FGFR system plays a relevant role in tumor growth, invasion, and resistance, as well as in angiogenesis and dissemination. To date, scattered pieces of literature report that FGFs and FGFRs are expressed by a significant subset of primary eye cancers, where they play relevant and pleiotropic roles. In this review, we provide an up-to-date description of the relevant roles played by the FGF/FGFR system in ocular tumors and speculate on its possible prognostic and therapeutic exploitation.

Semi-Automated Cell Panning for Efficient Isolation of FGFR3-Targeting Antibody

Phage display technology is a widely used practical tool for isolating binding molecules against the desired targets in phage libraries. In the case of targeting the membrane protein with its natural conformation, conventional bio-panning has limitations on the efficient screening of the functionally relevant antibodies. To enrich the single-chain variable fragment (scFv) pools for recognizing the natural conformation of the membrane targets, the conventional bio-panning and screening process was modified to include the semi-automated cell panning protocol. Using FGFR3-overexpressing patient-derived cancer cells, biotin-X-DHPE was introduced and coupled to Streptavidin-coated magnetic beads for use in the solution-phage bio-panning procedure. The resulting clones of scFv were compared to the diversity of the binding region, especially on CDR-H3. The clones enriched further by cell-based panning procedure possessed a similar binding site and the CDR-H3 loop structure. The resulting antibodies inhibited cell growth and induced target degradation. This process may be a useful tool for screening biologically related antibodies that recognize natural conformational structure on cell membrane protein. Furthermore, cell-based panning has the potential to further expand to a high-throughput screening (HTS) system and automation process.

Recent advances of dual FGFR inhibitors as a novel therapy for cancer

Fibroblast growth factor receptor (FGFR) includes four highly conserved transmembrane receptor tyrosine kinases (FGFR1-4). FGF and FGFR regulate many biological processes, such as angiogenesis, wound healing and tissue regeneration. The abnormal expression of FGFR is related to the tumorigenesis, tumor progression and drug resistance of anti-tumor treatments in many types of tumors. Nowadays there are many anti-cancer drugs targeting FGFR. However, traditional single-target anti-tumor drugs are easy to acquire drug resistance. The therapeutic effect can be enhanced by simultaneously inhibiting FGFR and another target (such as VEGFR, EGFR, PI3K, CSF-1R, etc.). We know drug combination can bring problems such as drug interactions. Therefore, the development of FGFR dual target inhibitors is an important direction. In this paper, we reviewed the research on dual FGFR inhibitors in recent years and made brief comments on them.

FGF/FGFR signaling in health and disease

Growing evidences suggest that the fibroblast growth factor/FGF receptor (FGF/FGFR) signaling has crucial roles in a multitude of processes during embryonic development and adult homeostasis by regulating cellular lineage commitment, differentiation, proliferation, and apoptosis of various types of cells. In this review, we provide a comprehensive overview of the current understanding of FGF signaling and its roles in organ development, injury repair, and the pathophysiology of spectrum of diseases, which is a consequence of FGF signaling dysregulation, including cancers and chronic kidney disease (CKD). In this context, the agonists and antagonists for FGF-FGFRs might have therapeutic benefits in multiple systems.

The FGF/FGFR system in the physiopathology of the prostate gland

Fibroblast growth factors (FGFs) are a family of proteins possessing paracrine, autocrine, or endocrine functions in a variety of biological processes, including embryonic development, angiogenesis, tissue homeostasis, wound repair, and cancer. Canonical FGFs bind and activate tyrosine kinase FGF receptors (FGFRs), triggering intracellular signaling cascades that mediate their biological activity. Experimental evidence indicates that FGFs play a complex role in the physiopathology of the prostate gland that ranges from essential functions during embryonic development to modulation of neoplastic transformation. The use of ligand- and receptor-deleted mouse models has highlighted the requirement for FGF signaling in the normal development of the prostate gland. In adult prostate, the maintenance of a functional FGF/FGFR signaling axis is critical for organ homeostasis and function, as its disruption leads to prostate hyperplasia and may contribute to cancer progression and metastatic dissemination. Dissection of the molecular landscape modulated by the FGF family will facilitate ongoing translational efforts directed toward prostate cancer therapy.

mTOR: Role in cancer, metastasis and drug resistance

Mammalian target of rapamycin (mTOR) is a serine/threonine kinase that gets inputs from the amino acids, nutrients, growth factor, and environmental cues to regulate varieties of fundamental cellular processes which include protein synthesis, growth, metabolism, aging, regeneration, autophagy, etc. The mTOR is frequently deregulated in human cancer and activating somatic mutations of mTOR were recently identified in several types of human cancer and hence mTOR is therapeutically targeted. mTOR inhibitors were commonly used as immunosuppressors and currently, it is approved for the treatment of human malignancies. This review briefly focuses on the structure and biological functions of mTOR. It extensively discusses the genetic deregulation of mTOR including amplifications and somatic mutations, mTOR-mediated cell growth promoting signaling, therapeutic targeting of mTOR and the mechanisms of resistance, the role of mTOR in precision medicine and other recent advances in further understanding the role of mTOR in cancer.

A Novel FGFR3 Splice Variant Preferentially Expressed in African American Prostate Cancer Drives Aggressive Phenotypes and Docetaxel Resistance

Alternative splicing (AS) has been shown to participate in prostate cancer development and progression; however, a link between AS and prostate cancer health disparities has been largely unexplored. Here we report on the cloning of a novel splice variant of FGFR3 that is preferentially expressed in African American (AA) prostate cancer. This novel variant (FGFR3-S) omits exon 14, comprising 123 nucleotides that encode the activation loop in the intracellular split kinase domain. Ectopic overexpression of FGFR3-S in European American (EA) prostate cancer cell lines (PC-3 and LNCaP) led to enhanced receptor autophosphorylation and increased activation of the downstream signaling effectors AKT, STAT3, and ribosomal S6 compared with FGFR3-L (retains exon 14). The increased oncogenic signaling imparted by FGFR3-S was associated with a substantial gain in proliferative and antiapoptotic activities, as well as a modest but significant gain in cell motility. Moreover, the FGFR3-S-conferred proliferative and motility gains were highly resistant to the pan-FGFR small-molecule inhibitor dovitinib and the antiapoptotic gain was insensitive to the cytotoxic drug docetaxel, which stands in marked contrast with dovitinib- and docetaxel-sensitive FGFR3-L. In an in vivo xenograft model, mice injected with PC-3 cells overexpressing FGFR3-S exhibited significantly increased tumor growth and resistance to dovitinib treatment compared with cells overexpressing FGFR3-L. In agreement with our in vitro and in vivo findings, a high FGFR3-S/FGFR3-L expression ratio in prostate cancer specimens was associated with poor patient prognosis. IMPLICATIONS: This work identifies a novel FGFR3 splice variant and supports the hypothesis that differential AS participates in prostate cancer health disparities.

SPOP and FOXA1 mutations are associated with PSA recurrence in ERG wt tumors, and SPOP downregulation with ERG-rearranged prostate cancer

BACKGROUND

ERG fusion-related prostate cancer (PrCa) is the most prevalent oncogenic driver subclass. SPOP, FOXA1, and IDH1 mutations are other three main oncogenic driver subclasses in non-ETS-fusion PrCa. ERG protein levels seem to be increased in SPOP-mutated cases, and different studies reported that SPOP mutations and ERG fusions are mutually exclusive. The aim of this study has been to analyze the alterations in non-ETS-oncogenic drivers in PrCa.

METHODS

SPOP, FOXA1, and IDH mutations were investigated by polymerase chain reaction (PCR) and Sanger direct sequencing. ERG, SPOP, and TMPRSS2-ERG messenger RNA expression was assessed by quantitative real-time PCR from complementary DNA, and the presence of the fusion was also analyzed by nonquantitative PCR. The clinical pathological features were retrieved from the charts of the 111 patients included in the study (MARBiobanc, Barcelona, Spain).

RESULTS

Loss of SPOP expression (25.2%) was associated with ERG overexpression (P = 0.0036). SPOP mutations were found in 5.4% cases, all with wild-type (wt) ERG (P = 0.007). FOXA1 mutations were found in 8.2% cases, most of them ERG wt (P = 0.06). No IDH1 mutations were found. SPOP or FOXA1 mutations were found in 1.7% of ERG-rearranged, and 34.2% of non-ERG-rearranged cases (P < 0.0001). SPOP or FOXA1 alterations (mutations or expression loss) were significantly more common in GG5, while isolated ERG overexpression was more common in GG1 tumors (P = 0.042). SPOP-or FOXA1-mutated cases were associated with a shorter time to prostate-specific antigen (PSA) recurrence in the univariate (P = 0.0009), and with the PSA recurrence risk in the multivariate (P = 0.023) analysis.

CONCLUSIONS

In conclusion, SPOP and FOXA1 mutations may have prognostic value in ERG wt tumors. Interestingly, in absence of SPOP mutations, downregulation of this gene is a feature of many ERG-rearranged prostate tumors.

Recent developments and advances of FGFR as a potential target in cancer

FGFs and their receptors (FGFRs) are critical for many biologic processes, including angiogenesis, wound healing and tissue regeneration. Aberrations in FGFR signaling are common in cancer, making FGFRs a promising target in antitumor studies. To date, many FGFR inhibitors are being detected in clinical studies, and resistance to some inhibitors has emerged. Understanding the mechanisms of resistance is a fundamental step for further implementation of targeted therapies. In this review, we will describe the basic knowledge regarding FGF/FGFR signaling and categorize the clinical FGFR inhibitors. The mechanisms of resistance to FGFR inhibitors and corresponding strategies of overcoming drug resistance will also be discussed.

Nintedanib antiangiogenic inhibitor effectiveness in delaying adenocarcinoma progression in Transgenic Adenocarcinoma of the Mouse Prostate (TRAMP)

Background

In recent times, anti-cancer treatments have focused on Fibroblast Growth Factor (FGF) and Vascular-Endothelial Growth Factor (VEGF) pathway inhibitors so as to target tumor angiogenesis and cellular proliferation. One such drug is Nintedanib; the present study evaluated the effectiveness of Nintedanib treatment against in vitro proliferation of human prostate cancer (PCa) cell lines, and growth and progression of different grades of PCa lesions in pre-clinical PCa transgenic adenocarcinoma for the mouse prostate (TRAMP) model.

Methods

Both androgen-independent (LNCaP) and androgen-dependent (PC3) PCa cell lines were treated with a range of Nintedanib doses for 72 h, and effect on cell growth and expression of angiogenesis associated VEGF receptors was analyzed. In pre-clinical efficacy evaluation, male TRAMP mice starting at 8 and 12 weeks of age were orally-fed with vehicle control (10% Tween 20) or Nintedanib (10 mg/Kg/day in vehicle control) for 4 weeks, and sacrificed immediately after 4 weeks of drug treatment or sacrificed 6–10 weeks after stopping drug treatments. At the end of treatment schedule, mice were sacrificed and ventral lobe of prostate was excised along with essential metabolic organ liver, and subjected to histopathological and extensive molecular evaluations.

Results

The total cell number decreased by 56–80% in LNCaP and 45–93% in PC3 cells after 72 h of Nintedanib treatment at 2.5–25 μM concentrations. In pre-clinical TRAMP studies, Nintedanib led to a delay in tumor progression in all treatment groups; the effect was more pronounced when treatment was given at the beginning of the glandular lesion development and continued till study end. A decreased microvessel density and VEGF immunolocalization was observed, besides decreased expression of Androgen Receptor (AR), VEGFR-1 and FGFR-3 in some of the treated groups. No changes were observed in the histological liver analysis.

Conclusions

Nintedanib treatment was able to significantly decrease the growth of PCa cell lines and also delay growth and progression of PCa lesions to higher grades of malignancy (without inducing any hepatotoxic effects) in TRAMP mice. Furthermore, it was observed that Nintedanib intervention is more effective when administered during the early stages of neoplastic development, although the drug is capable of reducing cell proliferation even after treatment interruption.

Establishment of a novel cellular model for myxofibrosarcoma heterogeneity

Human cancers frequently display substantial intra-tumoural heterogeneity in virtually all distinguishable phenotypic features, such as cellular morphology, gene expression, and metastatic potential. In order to investigate tumour heterogeneity in myxofibrosarcoma, we established a novel myxofibrosarcoma cell line with two well defined sub-clones named MUG-Myx2a and MUG-Myx2b. The parental tumour tissue and both MUG-Myx2 cell lines showed the same STR profile. The fact that MUG-Myx2a showed higher proliferation activity, faster migration and enhanced tumourigenicity was of particular interest. NGS mutation analysis revealed corresponding mutations in the FGFR3, KIT, KDR and TP53 genes. In contrast, the MUG-Myx2a cell lines showed an additional PTEN mutation. Analysis of CNV uncovered a highly aberrant karyotype with frequent losses and gains in the tumour sample. The two MUG-Myx2 cell lines share several CNV features of the tumour tissue, while some CNVs are present only in the two cell lines. Furthermore, certain CNV gains and losses that are exclusive to either MUG-Myx2a or MUG-Myx2b, distinguish the two cell lines. As it is currently not possible to purchase two different sarcoma cell lines derived from the same patient, the novel myxofibrosarcoma cell lines MUG-Myx2a and MUG-Myx2b will be useful tools to study pathogenesis, tumour heterogeneity and treatment options.

Inhibition of the fibroblast growth factor receptor (FGFR) pathway: the current landscape and barriers to clinical application

The fibroblast growth factor/fibroblast growth factor receptor (FGF/FGFR) is a tyrosine kinase signaling pathway that has a fundamental role in many biologic processes including embryonic development, tissue regeneration, and angiogenesis. Increasing evidence indicates that this pathway plays a critical role in oncogenesis via gene amplification, activating mutations, or translocation in tumors of various histologies. With multiplex sequencing technology, the detection of FGFR aberrations has become more common and is tied to cancer cell proliferation, resistance to anticancer therapies, and neoangiogenesis. Inhibition of FGFR signaling appears promising in preclinical studies, suggesting a pathway of clinical interest in the development of targeted therapy. Phase I trials have demonstrated a manageable toxicity profile. Currently, there are multiple FGFR inhibitors under study with many non-selective (multi-kinase) inhibitors demonstrating limited clinical responses. As we progress from the first generation of non-selective drugs to the second generation of selective FGFR inhibitors, it is clear that FGFR aberrations do not behave uniformly across cancer types; thus, a deeper understanding of biomarker strategies is undoubtedly warranted. This review aims to consolidate data from recent clinical trials with a focus on selective FGFR inhibitors. As Phase II clinical trials emerge, concentration on patient selection as it pertains to predicting response to therapy, feasible methods for overcoming toxicity, and the likelihood of combination therapies should be utilized. We will also discuss qualities that may be desirable in future generations of FGFR inhibitors, with the hope that overcoming these current barriers will expedite the availability of this novel class of medications.

Roles of FGFR in oral carcinogenesis

Fibroblast growth factor receptors (FGFRs) play essential roles in organ development during the embryonic period, and regulate tissue repair in adults. Accumulating evidence suggests that alterations in FGFR signalling are involved in diverse types of cancer. In this review, we focus on aberrant regulation of FGFRs in pathogenesis of oral squamous cell carcinoma (OSCC), including altered expression and subcellular location, aberrant isoform splicing and mutations. We also provide an overview of oncogenic roles of each FGFR and its downstream signalling pathways in regulating OSCC cell proliferation and metastasis. Finally, we discuss potential application of FGFRs as anti-cancer targets in the preclinical environment and in clinical practice.

Differential Roles of Carboxylated and Uncarboxylated Osteocalcin in Prostate Cancer Growth

Serum levels of osteocalcin (OC), a bone matrix non-collagenous protein secreted by osteoblasts, are correlated with pathological bone remodeling such as the bone metastasis of cancer, as well as physiological bone turnover. The pathological roles in prostate cancer growth of the two existing types of serum OC, γ-carboxylated (GlaOC) and lower- (or un-) carboxylated (GluOC), have not yet been discriminatively examined. In the present study, we demonstrate that normal prostate epithelial cell growth was promoted by both types of OC, while growth of cancer cells in the prostate was accelerated by GlaOC but suppressed by GluOC. We suggest that OC regulates prostate cancer growth depending on the γ-carboxylation, in part by triggering reduced phosphorylation of receptor tyrosine kinases.

Retrospective study testing next generation sequencing of selected cancer-associated genes in resected prostate cancer

PURPOSE

Prostate cancer (PCa) has a highly heterogeneous outcome. Beyond Gleason Score, Prostate Serum Antigen and tumor stage, nowadays there are no biological prognostic factors to discriminate between indolent and aggressive tumors.The most common known genomic alterations are the TMPRSS-ETS translocation and mutations in the PI3K, MAPK pathways and in p53, RB and c-MYC genes.The aim of this retrospective study was to identify by next generation sequencing the most frequent genetic variations (GVs) in localized and locally advanced PCa underwent prostatectomy and to investigate their correlation with clinical-pathological variables and disease progression.

RESULTS

Identified non-synonymous GVs included TP53 p.P72R (78% of tumors), two CSFR1 SNPs, rs2066934 and rs2066933 (70%), KDR p.Q472H (67%), KIT p.M541L (28%), PIK3CA p.I391M (19%), MET p.V378I (10%) and FGFR3 p.F384L/p.F386L (8%). TP53 p.P72R, MET p.V378I and CSFR1 SNPs were significantly associated with the HI risk group, TP53 and MET variations with T≥T2c. FGFR3 p.F384L/p.F386L was correlated with T≤T2b. MET p.V378I mutation, detected in 20% of HI risk patients, was associated with early biochemical recurrence.

EXPERIMENTAL DESIGN

Nucleic acids were obtained from tissue samples of 30 high (HI) and 30 low-intermediate (LM) risk patients, according to D'Amico criteria. Genomic DNA was explored with the Ion_AmpliSeq_Cancer_Hotspot_Panel_v.2 including 50 cancer-associated genes. GVs with allelic frequency (AF) ≥10%, affecting protein function or previously associated with cancer, were correlated with clinical-pathological variables.

CONCLUSION

Our results confirm a complex mutational profile in PCa, supporting the involvement of TP53, MET, FGFR3, CSF1R GVs in tumor progression and aggressiveness.

Design strategies, structure activity relationship and mechanistic insights for purines as kinase inhibitors

Kinases control a diverse set of cellular processes comprising of reversible phosphorylation of proteins. Protein kinases play a pivotal role in human tumor cell proliferation, migration and survival of neoplasia. In the recent past, purine based molecules have emerged as significantly potent kinase inhibitors. In view of their promising potential for the inhibition of kinases, this review article focuses on purines which have progressed as kinase inhibitors during the last five years. A detailed account of the design strategies employed for the synthesis of purine analogs exerting inhibitory effects on diverse kinases has been presented. Apart from presenting the design strategies, the article also highlights the structure activity relationship along with mechanistic insights revealed during the biological evaluation of the purine analogs for kinase inhibition. The interactions with the amino acid residues responsible for kinase inhibitory potential of purine based molecules have also been discussed. In this assemblage, purine based protein kinase inhibitors patented in the past have also been summarized in the tabular form. This compilation will be of great interest for the researchers working in the area of protein kinase inhibitors.

Recent developments in receptor tyrosine kinases targeted anticancer therapy

Novel concepts and understanding of receptors lead to discoveries and optimization of many small molecules and antibodies as anti-cancerous drugs. Receptor tyrosine kinases (RTKs) are such a promising class of receptors under the investigation in past three decades. RTKs are one of the essential mediators of cell signaling mechanism for various cellular processes. Transformations such as overexpression, dysregulation, or mutations of RTKs may result into malignancy, and thus are an important target for anticancer therapy. Numerous subfamilies of RTKs, such as epidermal growth factor receptor, vascular endothelial growth factor receptor, fibroblast growth factor receptors, insulin-like growth factor receptor, and hepatocyte growth factor receptor, have been being investigated in recent years as target for anticancer therapy. The present review focuses several small molecules drugs as well as monoclonal antibodies targeting aforesaid subfamilies either approved or under investigation to treat the various cancers.

Targeting RTK Signaling Pathways in Cancer

The RAS/MAP kinase and the RAS/PI3K/AKT pathways play a key role in the regulation of proliferation, differentiation and survival. The induction of these pathways depends on Receptor Tyrosine Kinases (RTKs) that are activated upon ligand binding. In cancer, constitutive and aberrant activations of components of those pathways result in increased proliferation, survival and metastasis. For instance, mutations affecting RTKs, Ras, B-Raf, PI3K and AKT are common in perpetuating the malignancy of several types of cancers and from different tissue origins. Therefore, these signaling pathways became prime targets for cancer therapy. This review aims to provide an overview about the most frequently encountered mutations, the pathogenesis that results from such mutations and the known therapeutic strategies developed to counteract their aberrant functions.

Polymorphisms of FGFR1 in HBV-related hepatocellular carcinoma

Hepatitis B virus (HBV)-induced hepatocellular carcinoma (HCC) is one of the most commonly diagnosed cancers in China. It is important to understand the genetic mechanisms underlying the development and progression of HBV-related HCC and to identify new biomarkers for clinical treatment. The important role of fibroblast growth factor receptors (FGFRs) has been widely recognized in many types of cancers, but the association between FGFR polymorphisms and HCC carcinogenesis has been rarely reported. In this study, 199 patients with HBV-associated cirrhosis, 203 with HBV-associated HCC, and 184 healthy controls with no liver diseases were enrolled as participants. Using SNaPshot assays, five SNPs (rs13317, rs7825208, rs1047057, rs1047111, and rs1966265) of growth factor receptor genes were genotyped. Our results showed that the G/A and G/G genotypes at rs7825208 of FGFR1 were negatively correlated with HBV-related HCC (odds ratio (OR) = 0.45, 95% confidence interval (CI) = 0.22-0.93, P = 0.027). However, after Bonferroni correction, these significant differences no longer existed (P > 0.05). Our results indicated that these five polymorphisms of fibroblast growth factor receptor genes do not play any independent roles in the tumorigenesis and progression of HBV-related HCC in Han Chinese patients.

Bioinformatics analysis of the target gene of fibroblast growth factor receptor 3 in bladder cancer and associated molecular mechanisms

The aim of the present study was to elucidate the molecular mechanisms of fibroblast growth factor receptor 3 (FGFR3) activation via overexpression or mutation of the FGFR3 target gene in bladder cancer (BC). The transcription profile data GSE41035, which included 18 BC samples, containing 3 independent FGFR3 short hairpin (sh)RNA, and 6 control samples, containing enhanced green fluorescent protein (EGFP) shRNA, were obtained from the National Center of Biotechnology Information Gene Expression Omnibus database. The Limma package with multiple testing correction was used to identify differentially expressed genes (DEGs) between FGFR3 knockdown and control samples. Gene ontology (GO) and pathway enrichment analysis were conducted in order to investigate the DEGs at the functional level. In addition, differential co-expression analysis was employed to construct a gene co-expression network. A total of 196 DEGs were acquired, of which 101 were downregulated and 95 were upregulated. In addition, a gene signature was identified linking FGFR3 signaling with de novo sterol biosynthesis and metabolism using GO and pathway enrichment analysis. Furthermore, the present study demonstrated that the genes NME2, CCNB1 and H2AFZ were significantly associated with BC, as determined by the protein-protein interaction network of DEGs and co-expressed genes. In conclusion, the present study revealed the involvement of FGFR3 in the regulation of sterol biosynthesis and metabolism in the maintenance of BC; in addition, the present study provided a novel insight into the molecular mechanisms of FGFR3 in BC. These results may therefore contribute to the theoretical guidance into the detection and therapy of BC.

Gene expression profiling analysis of castration-resistant prostate cancer

Background

Prostate cancer is a global health issue. Usually, men with metastatic disease will progress to castration-resistant prostate cancer (CRPC). We aimed to identify the differentially expressed genes (DEGs) in tumor samples from non-castrated and castrated men from LNCaP Orthotopic xenograft models of prostate cancer and to study the mechanisms of CRPC.

Material/Methods

In this work, GSE46218 containing 4 samples from non-castrated men and 4 samples from castrated men was downloaded from Gene Expression Omnibus. We identified DEGs using limma Geoquery in R, the Robust Multi-array Average (RMA) method in Bioconductor, and Bias methods, followed by constructing an integrated regulatory network involving DEGs, miRNAs, and TFs using Cytoscape. Then, we analyzed network motifs of the integrated gene regulatory network using FANMOD. We selected regulatory modules corresponding to network motifs from the integrated regulatory network by Perl script. We preformed gene ontology (GO) and pathway enrichment analysis of DEGs in the regulatory modules using DAVID.

Results

We identified total 443 DEGs. We built an integrated regulatory network, found three motifs (motif 1, motif 2 and motif 3), and got two function modules (module 1 corresponded to motif 1, and module 2 corresponded to motif 2). Several GO terms (such as regulation of cell proliferation, positive regulation of macromolecule metabolic process, phosphorylation, and phosphorus metabolic process) and two pathways (pathway in cancer and Melanoma) were enriched. Furthermore, some significant DEGs (such as CAV1, LYN, FGFR3 and FGFR3) were related to CPRC development.

Conclusions

These genes might play important roles in the development and progression of CRPC.

Tyrosine kinase receptors as molecular targets in pheochromocytomas and paragangliomas

Pheochromocytomas and paragangliomas are neuroendocrine tumors shown to be responsive to multitargeted tyrosine kinase inhibitor (TKI) treatment. Despite growing knowledge regarding their genetic basis, the ability to predict behavior in these tumors remains challenging. There is also limited knowledge of their tyrosine kinase receptor expression and whether the clinical response observed to the TKI sunitinib relates only to its anti-angiogenic properties or also due to a direct effect on tumor cells. To answer these questions, an in vitro model of sunitinib treatment of a pheochromocytoma cell line was created. Sunitinib targets (VEGFRs, PDGFRs, and C-KIT), FGFRs, and cell cycle regulatory proteins were investigated in human tissue microarrays. SDHB immunohistochemistry was used as a surrogate marker for the presence of succinate dehydrogenase mutations. The FGFR4 G388R single nucleotide polymorphism was also investigated. Sunitinib treatment in vitro decreases cell proliferation mainly by targeting cell cycle, DNA metabolism, and cell organization genes. FGFR1, -2, and -4, VEGFR2, PDGFRα, and p16 were overexpressed in primary human pheochromocytomas and paragangliomas. Discordant results were observed for VEGFR1, p27, and p21 overexpressed in paragangliomas but underexpressed in pheochromocytomas; PDGFRβ, Rb, and Cyclin D1 overexpressed in paragangliomas only; and FGFR3 overexpressed in pheochromocytomas and underexpressed in paragangliomas. Low expression of C-KIT, p53, and Aurora kinase A and B was observed. Nuclear FGFR2 expression was associated with increased risk of metastasis (odds ratio (OR)=7.61, P=0.008), as was membranous PDGFRα (OR=13.71, P=0.015), membranous VEGFR1 (OR=8.01, P=0.037), nuclear MIB1 (OR=1.26, P=0.008), and cytoplasmic p27 (OR=1.037, P=0.030). FGFR3, VEGFR2, and C-KIT levels were associated with decreased risk of metastasis. We provide new insights into the mechanistic actions of sunitinib in pheochromocytomas and paragangliomas, and support current evidence that multitargeted TKIs might be a suitable treatment alternative for these tumors.

Clinical significance of FGFR1 gene amplification in lung cancer patients

SUMMARY 

Background: Lung cancer is the leading cause of cancer related death worldwide. Molecular targeted therapies are routinely used for pulmonary adenocarcinomas, harboring therapeutically tractable genomic aberrations such as EGFR mutations, ALK and ROS1 fusions. Comparable therapeutic options are still missing for squamous and small-cell lung cancer. Results: Molecular analyses revealed a significant amplification of FGFR1 in 20% of squamous and 6% of small-cell carcinomas. Preclinical and first clinical trials with FGFR inhibitors have shown that this genomic alteration is therapeutically actionable. For detection of FGFR1 amplification fluorescence in situ hybridization is a specific biomarker assay. We review evaluation strategy and criteria for FGFR1 positivity. Conclusion: FGFR1 amplification represents a promising potential target in squamous and small-cell lung cancer.

Prognostic significance of the co-overexpression of fibroblast growth factor receptors 1, 2 and 4 in gastric cancer

The overexpression of fibroblast growth factor receptor (FGFR) 2 is an established prognostic factor and treatment target in gastric cancer. However, the roles of other FGFRs have not been fully elucidated. In this study, we investigated the correlations of the expression of FGFR1-4 with clinicopathological characteristics and outcomes in gastric cancer. Tumor samples were obtained from 222 patients with gastric adenocarcinoma who underwent gastrectomy between 2003 and 2007. The expression of each FGFR was measured in the tumors by immunohistochemical analysis. The overexpression of FGFR1, FGFR2 or FGFR4 was found to be significantly associated with tumor progression, including depth of invasion, lymph node metastasis, pathological stage and distant metastasis or recurrent disease. Patients exhibiting overexpression of FGFR1, FGFR2 or FGFR4 had a significantly poorer disease-specific survival (DSS; P<0.001, P=0.008 and P<0.001, respectively). Moreover, the co-overexpression of all three FGFRs was significantly associated with a poorer DSS compared to the expression of none or only one of the FGFRs (P<0.001 and P=0.001, respectively) and it was found to be an independent prognostic factor (HR=1.71, 95% CI: 1.02-2.85, P=0.041). In conclusion, high expression of FGFR1, FGFR2 or FGFR4 was associated with tumor progression and poor survival in patients with gastric cancer. Similar to FGFR2, FGFR1 and FGFR4 may be considered as prognostic factors and treatment targets in gastric cancer.

High IGF2 and FGFR3 are associated with tumour progression in undifferentiated pleomorphic sarcomas, but EGFR and FGFR3 mutations are a rare event

AIM

Pleomorphic undifferentiated sarcomas (formerly known as malignant fibrous histiocytomas) are recognised by the actual WHO classification as an undifferentiated, unclassifiable category of pleomorphic sarcomas which show no definable line of differentiation and are still a diagnosis of exclusion. Therefore, diagnostic, prognostic and therapeutic options of these tumours are urgently needed.

METHODS

Three hundred and twenty-seven spindle cell tumours of a German consultation and reference centre of soft tissue tumours consisting of 200 undifferentiated pleomorphic sarcomas (UPS), 45 low-grade sarcomas (10 low-grade fibromyxoid sarcomas, 32 low-grade myofibroblastic sarcomas and three myxoinflammatory fibroblastic sarcomas) and 82 tumours of the fasciitis family were revisited. The specimens were analysed immunohistochemically with distinct markers including tyrosine kinases and expression correlated with clinicopathological parameters. Additionally, mutational analysis was performed on specimens with high expression of EGFR and FGFR3.

RESULTS

At the protein level high IGF2 expression was observed in 86 %, FGFR3 (69 %), PDGFRA (62 %), PDGFRB (39 %), FGFR1 (8 %), EGFR (5 %), KDR/VEGFR2 (3 %), ALK (0 %) and high Ki67 (63 %) in UPS. High expressions of IGF2 and FGFR3 are significantly correlated with a higher grading (p = 0.023 and p = 0.016, respectively) and a high Ki67 index (p = 0.017 and p = 0.001, respectively). No mutations were found in the hot spots of tumour specimens with a high expression of EGFR gene (exons 18-21) and FGFR3 gene (exons 7, 10 and 15).

CONCLUSIONS

High expressions of IGF2 and FGFR3 are significantly associated with tumour progression, grading and Ki67 and might classify a subgroup of undifferentiated pleomorphic sarcoma. These markers might guide targeted therapies in these neoplasms.

Fibroblast growth factor signaling and inhibition in non-small cell lung cancer and their role in squamous cell tumors

With the introduction of targeted agents primarily applicable to non-small cell lung cancer (NSCLC) of adenocarcinoma histology, there is a heightened unmet need in the squamous cell carcinoma population. Targeting the angiogenic fibroblast growth factor (FGF)/FGF receptor (FGFR) signaling pathway is among the strategies being explored in squamous NSCLC; these efforts are supported by growth-promoting effects of FGF signaling in preclinical studies (including interactions with other pathways) and observations suggesting that FGF/FGFR-related aberrations may be more common in squamous versus adenocarcinoma and other histologies. A number of different anti-FGF/FGFR approaches have shown promise in preclinical studies. Clinical trials of two multitargeted tyrosine kinase inhibitors are restricting enrollment to patients with squamous NSCLC: a phase I/II trial of nintedanib added to first-line gemcitabine/cisplatin and a phase II trial of ponatinib for previously treated advanced disease, with the latter requiring not only squamous disease but also a confirmed FGFR kinase amplification or mutation. There are several ongoing clinical trials of multitargeted agents in general NSCLC populations, including but not limited to patients with squamous disease. Other FGF/FGFR-targeted agents are in earlier clinical development. While results are awaited from these clinical investigations in squamous NSCLC and other disease settings, additional research is needed to elucidate the role of FGF/FGFR signaling in the biology of NSCLC of different histologies.

Functional roles of fibroblast growth factor receptors (FGFRs) signaling in human cancers

The fibroblast growth factor receptors (FGFRs) regulate important biological processes including cell proliferation and differentiation during development and tissue repair. Over the past decades, numerous pathological conditions and developmental syndromes have emerged as a consequence of deregulation in the FGFRs signaling network. This review aims to provide an overview of FGFR family, their complex signaling pathways in tumorigenesis, and the current development and application of therapeutics targeting the FGFRs signaling for treatment of refractory human cancers.

Small molecule inhibition of fibroblast growth factor receptors in cancer

Fibroblast growth factors (FGFs) signal through FGF receptors (FGFRs), which are a sub-family of the superfamily of receptor tyrosine kinases, to regulate human development and metabolism. Uncontrolled FGF signaling is responsible for diverse array of developmental disorders, most notably skeletal syndromes due to FGFR gain-of-function mutations. Studies in the last few years have provided significant evidence for the importance of FGF signaling in the pathogenesis of diverse cancers, including endometrial and bladder cancers. FGFs are both potent mitogenic and angiogenic factors and can contribute to carcinogenesis by stimulating cell proliferation and tumor angiogenesis. Gene knockout and pharmacological inhibition of FGFRs in in vivo and in vitro models validate FGFRs as a target for cancer treatment. Considerable efforts are being expended to develop specific, small-molecule inhibitors for treating FGFR-driven cancers. Recent reviews on the FGF/FGFR system have focused primarily on signaling, pathophysiology, and functions in cancer. In this article, we review the key roles of FGFR in cancer, provide an update on the status of clinical trials with small-molecule FGFR inhibitors, and discuss how the current structural data on FGFR kinases guide the design and characterization of new FGFR inhibitors.

A new algorithm for integrated analysis of miRNA-mRNA interactions based on individual classification reveals insights into bladder cancer

Background

MicroRNAs (miRNAs) are small non-coding RNAs that regulate gene expression. It has been proposed that miRNAs play an important role in cancer development and progression. Their ability to affect multiple gene pathways by targeting various mRNAs makes them an interesting class of regulators.

Methodology/Principal Findings

We have developed an algorithm, Classification based Analysis of Paired Expression data of RNA (CAPE RNA), which is capable of identifying altered miRNA-mRNA regulation between tissues samples that assigns interaction states to each sample without preexisting stratification of groups. The distribution of the assigned interaction states compared to given experimental groups is used to assess the quality of a predicted interaction. We demonstrate the applicability of our approach by analyzing urothelial carcinoma and normal bladder tissue samples derived from 24 patients. Using our approach, normal and tumor tissue samples as well as different stages of tumor progression were successfully stratified. Also, our results suggest interesting differentially regulated miRNA-mRNA interactions associated with bladder tumor progression.

Conclusions/Significance

The need for tools that allow an integrative analysis of microRNA and mRNA expression data has been addressed. With this study, we provide an algorithm that emphasizes on the distribution of samples to rank differentially regulated miRNA-mRNA interactions. This is a new point of view compared to current approaches. From bootstrapping analysis, our ranking yields features that build strong classifiers. Further analysis reveals genes identified as differentially regulated by miRNAs to be enriched in cancer pathways, thus suggesting biologically interesting interactions.

Fibroblast growth factor receptor inhibitors as a cancer treatment: from a biologic rationale to medical perspectives

The fibroblast growth factor/fibroblast growth factor receptor (FGF/FGFR) signaling pathway plays a fundamental role in many physiologic processes, including embryogenesis, adult tissue homeostasis, and wound healing, by orchestrating angiogenesis. Ligand-independent and ligand-dependent activation have been implicated in a broad range of human malignancies and promote cancer progression in tumors driven by FGF/FGFR oncogenic mutations or amplifications, tumor neoangiogenesis, and targeted treatment resistance, thereby supporting a strong rationale for anti-FGF/FGFR agent development. Efforts are being pursued to develop selective approaches for use against this pathway by optimizing the management of emerging, class-specific toxicity profiles and correctly designing clinical trials to address these different issues.

A novel FGFR3-binding peptide inhibits FGFR3 signaling and reverses the lethal phenotype of mice mimicking human thanatophoric dysplasia

Gain-of-function mutations in fibroblast growth factor receptor-3 (FGFR3) lead to several types of human skeletal dysplasia syndromes including achondroplasia, hypochondroplasia and thanatophoric dysplasia (TD). Currently, there are no effective treatments for these skeletal dysplasia diseases. In this study, we screened, using FGFR3 as a bait, a random 12-peptide phage library and obtained 23 positive clones that share identical amino acid sequences (VSPPLTLGQLLS), named as peptide P3. This peptide had high binding specificity to the extracellular domain of FGFR3. P3 inhibited tyrosine kinase activity of FGFR3 and its typical downstream molecules, extracellular signal-regulated kinase/mitogen-activated protein kinase. P3 also promoted proliferation and chondrogenic differentiation of cultured ATDC5 chondrogenic cells. In addition, P3 alleviated the bone growth retardation in bone rudiments from mice mimicking human thanatophoric dysplasia type II (TDII). Finally, P3 reversed the neonatal lethality of TDII mice. Thus, this study identifies a novel inhibitory peptide for FGFR3 signaling, which may serve as a potential therapeutic agent for the treatment of FGFR3-related skeletal dysplasia.

Receptor tyrosine kinases activate canonical WNT/β-catenin signaling via MAP kinase/LRP6 pathway and direct β-catenin phosphorylation

Receptor tyrosine kinase signaling cooperates with WNT/β-catenin signaling in regulating many biological processes, but the mechanisms of their interaction remain poorly defined. We describe a potent activation of WNT/β-catenin by FGFR2, FGFR3, EGFR and TRKA kinases, which is independent of the PI3K/AKT pathway. Instead, this phenotype depends on ERK MAP kinase-mediated phosphorylation of WNT co-receptor LRP6 at Ser1490 and Thr1572 during its Golgi network-based maturation process. This phosphorylation dramatically increases the cellular response to WNT. Moreover, FGFR2, FGFR3, EGFR and TRKA directly phosphorylate β-catenin at Tyr142, which is known to increase cytoplasmic β-catenin concentration via release of β-catenin from membranous cadherin complexes. We conclude that signaling via ERK/LRP6 pathway and direct β-catenin phosphorylation at Tyr142 represent two mechanisms used by various receptor tyrosine kinase systems to activate canonical WNT signaling.

Mechanisms of FGFR-mediated carcinogenesis

In this review, the evidence for a role of fibroblast growth factor receptor (FGFR) mediated signalling in carcinogenesis are considered and relevant underlying mechanisms highlighted. FGF signalling mediated by FGFR follows a classic receptor tyrosine kinase signalling pathway and its deregulation at various points of its cascade could result in malignancy. Here we review the accumulating reports that revealed the association of FGF/FGFRs to various types of cancer at a genetic level, along with in vitro and in vivo evidences available so far, which indicates the functional involvement of FGF signalling in tumour formation and progression. An increasing number of drugs against the FGF pathways is currently in clinical testing. We will discuss the strategies for future FGF research in cancer and translational approaches.

A novel, selective inhibitor of fibroblast growth factor receptors that shows a potent broad spectrum of antitumor activity in several tumor xenograft models

The fibroblast growth factor receptors (FGFR) are tyrosine kinases that are present in many types of endothelial and tumor cells and play an important role in tumor cell growth, survival, and migration as well as in maintaining tumor angiogenesis. Overexpression of FGFRs or aberrant regulation of their activities has been implicated in many forms of human malignancies. Therefore, targeting FGFRs represents an attractive strategy for development of cancer treatment options by simultaneously inhibiting tumor cell growth, survival, and migration as well as tumor angiogenesis. Here, we describe a potent, selective, small-molecule FGFR inhibitor, (R)-(E)-2-(4-(2-(5-(1-(3,5-Dichloropyridin-4-yl)ethoxy)-1H-indazol-3yl)vinyl)-1H-pyrazol-1-yl)ethanol, designated as LY2874455. This molecule is active against all 4 FGFRs, with a similar potency in biochemical assays. It exhibits a potent activity against FGF/FGFR-mediated signaling in several cancer cell lines and shows an excellent broad spectrum of antitumor activity in several tumor xenograft models representing the major FGF/FGFR relevant tumor histologies including lung, gastric, and bladder cancers and multiple myeloma, and with a well-defined pharmacokinetic/pharmacodynamic relationship. LY2874455 also exhibits a 6- to 9-fold in vitro and in vivo selectivity on inhibition of FGF- over VEGF-mediated target signaling in mice. Furthermore, LY2874455 did not show VEGF receptor 2-mediated toxicities such as hypertension at efficacious doses. Currently, this molecule is being evaluated for its potential use in the clinic.

No evidence of FGFR3 mutations in prostate cancer

BACKGROUND

FGFR3 mutations are associated with a good clinical disease course in bladder tumors. Currently, prognostic markers to stratify prostate cancer (PCa) patients for conservative management are lacking. Conflicting results have been found on the presence of FGFR3 mutations in PCa. Our objective was to determine the prevalence of FGFR3 mutations in a subset of prostate tumors. Next, determine the prevalence of FGFR3 mutations in PCa patients with coexistent tumors in other tissues.

METHODS

Primary and locally advanced prostate tumors (n =132) were collected at our medical center. From the 132 PCa patients, 28 (21%) were diagnosed with coexistent primary tumors (bladder, skin, pancreas, renal cell, gastric, colon, hepatic, and lung). Tumors were analyzed by FGFR3 mutation analysis on exon 7, 10, and 15, known to harbor the most frequent mutations.

RESULTS

The prevalence of FGFR3 mutations in patients with only PCa was 0%. Most PCa patients presented with coexistent bladder (n=12) and bladder and skin tumors (n =7). Other coexistent tumors in PCa patients included: bladder and pancreatic cancer (n=1); bladder and renal cell carcinoma (n=1); bladder and gastric carcinoma (n=1); skin cancer (n=1); colon cancer (n= 3); hepatic carcinoma (n=1); and lung cancer (n = 1). FGFR3 mutations were detected in 9/15 (60%) analyzed bladder tumors.

CONCLUSIONS

FGFR3 mutations were absent in the investigated prostate tumors, suggesting a minor role of these mutations in tumorigenesis. Hence, FGFR3 mutation analysis is not suitable to select patients for conservative management. Interestingly, if a prostate tumor coincided with other tumors these were mostly bladder and skin.

Targeting fibroblast-growth-factor-receptor-dependent signaling for cancer therapy

INTRODUCTION

Fibroblast growth factors (FGF) exert a combination of biological effects that contribute to four of the six essential hallmarks of cancer. It is no surprise that FGF-dependent signaling has increasingly moved to the center of cancer therapy research during the past decade. This is illustrated by the large number of publications focusing on various aspects of this theme that have been published in the past 5 years.

AREAS COVERED

Information from these sources as well as ongoing work from the authors' groups is used to outline the physiological functions of FGF signaling and to highlight how the high oncogenic effects of deregulated FGFs and FGFRs derive from their physiological functions. The biological effect of deregulated FGFR signaling in malignant diseases is described and the current state of therapeutic targeting of FGFR is summarized.

EXPERT OPINION

Strategies for targeting FGFR-signaling for cancer therapy are very promising, but need to be carefully developed based on the physiological roles of FGF signaling. Preventive measures may be necessary for protection from FGF-related side effects. Combined targeting of several receptor tyrosine kinases or combination with other therapies may be a useful way of avoiding or ameliorating side effects. FGF-related markers of prognosis and therapy response still need to be investigated.

PI3K signaling pathway is activated by PIK3CA mRNA overexpression and copy gain in prostate tumors, but PIK3CA, BRAF, KRAS and AKT1 mutations are infrequent events

The phosphatidylinositol 3-kinase (PI3K)-AKT and RAS-MAPK pathways are deregulated in a wide range of human cancers by gain or loss of function in several of their components. Our purpose has been to identify genetic alterations in members of these pathways in prostate cancer. A total of 102 prostate tumors, 79 from prostate cancer alone (group G1) and 23 from bladder and prostate cancer patients (G2), are the subject of this study. In 20 of these 23, the bladder tumors were also analyzed. PIK3CA, KRAS, BRAF and AKT1 mutations were analyzed by direct sequencing, and BRAF also by pyrosequencing. PIK3CA quantitative mRNA expression and fluorescence in situ hybridization (FISH) gains were tested in 25 and 32 prostate tumors from both groups (G1 and G2), respectively. Immunohistochemistry for pAKT was performed in 55 prostate tumors. Of 25 prostate tumors, 10 (40%) had PIK3CA mRNA overexpression that was statistically associated with Gleason score ≥ 7 (P=0.018). PIK3CA copy gain was detected in 9 of 32 (28%) prostate tumors. Of 20 bladder tumors, 3 (15%) displayed mutations in PIK3CA, KRAS and AKT1, the corresponding prostate tumors being wt. We also detected a previously not reported PIK3CA polymorphism (IVS9+91) in two prostate tumors. In all, 56% of prostate tumors overexpressed pAKT. There is a statistical association (P<0.0001) of strong pAKT immunostaining with high Gleason score, and with PIK3CA alterations (mRNA overexpression and/or FISH gains). PIK3CA gene is deregulated by mRNA overexpression and DNA gain in ∼ 40 and 28% of prostate tumors, respectively. High-grade prostate tumors are associated with PIK3CA mRNA overexpression, but not with FISH status. PIK3CA, BRAF, KRAS and AKT1 mutations are very infrequent events in prostate tumors. However, PI3K signaling pathway is activated by PIK3CA FISH gain and/or mRNA overexpression, leading to an increased pAKT protein expression.

Synthesis of purin-2-yl and purin-6-yl-aminoglucitols as C-nucleosidic ATP mimics and biological evaluation as FGFR3 inhibitors

Two new series of C-nucleosidic ATP mimics have been synthesized using an efficient and versatile synthetic pathway. These compounds were designed as FGFR3 inhibitors using purine as a central scaffold. The two substituents, a polyhydroxylated ribose mimic and a lipophilic moiety, were linked either in position 2 or 6 of the purine ring in order to explore any possible binding mode. All the compounds were able to inhibit FGFR3 kinase activity at a concentration of 50 μM. Unexpectedly, the best inhibitor was found to be one of the synthetic intermediates 13 bearing an iodine atom in position 2. Docking studies have confirmed its location in the ATP binding site and revealed halogen bonding among key interactions.

Roles of fibroblast growth factor receptors in carcinogenesis

The fibroblast growth factor receptors (FGFR) play essential roles both during development and in the adult. Upon ligand binding, FGFRs induce intracellular signaling networks that tightly regulate key biological processes, such as cell proliferation, survival, migration, and differentiation. Deregulation of FGFR signaling can thus alter tissue homeostasis and has been associated with several developmental syndromes as well as with many types of cancer. In human cancer, FGFRs have been found to be deregulated by multiple mechanisms, including aberrant expression, mutations, chromosomal rearrangements, and amplifications. In this review, we will give an overview of the main FGFR alterations described in human cancer to date and discuss their contribution to cancer progression.

FGFR3 signaling induces a reversible senescence phenotype in chondrocytes similar to oncogene-induced premature senescence

Oncogenic activation of the RAS-ERK MAP kinase signaling pathway can lead to uncontrolled proliferation but can also result in apoptosis or premature cellular senescence, both regarded as natural protective barriers to cell immortalization and transformation. In FGFR3-related skeletal dyplasias, oncogenic mutations in the FGFR3 receptor tyrosine kinase cause profound inhibition of cartilage growth resulting in severe dwarfism, although many of the precise mechanisms of FGFR3 action remain unclear. Mutated FGFR3 induces constitutive activation of the ERK pathway in chondrocytes and, remarkably, can also cause both increased proliferation and apoptosis in growing cartilage, depending on the gestational age. Here, we demonstrate that FGFR3 signaling is also capable of inducing premature senescence in chondrocytes, manifested as reversible, ERK-dependent growth arrest accompanied by alteration of cellular shape, loss of the extracellular matrix, upregulation of senescence markers (alpha-GLUCOSIDASE, FIBRONECTIN, CAVEOLIN 1, LAMIN A, SM22alpha and TIMP 1), and induction of senescence-associated beta-GALACTOSIDASE activity. Our data support a model whereby FGFR3 signaling inhibits cartilage growth via exploiting cellular responses originally designed to eliminate cells harboring activated oncogenes.