Mutant fibroblast growth factor receptor 3 induces intracellular signaling and cellular transformation in a cell type- and mutation-specific manner

Relationship between clonal evolution and drug resistance in bladder cancer: A genomic research review

Bladder cancer stands as a prevalent global malignancy, exhibiting notable sex-based variations in both incidence and prognosis. Despite substantial strides in therapeutic approaches, the formidable challenge of drug resistance persists. The genomic landscape of bladder cancer, characterized by intricate clonal heterogeneity, emerges as a pivotal determinant in fostering this resistance. Clonal evolution, encapsulating the dynamic transformations within subpopulations of tumor cells over time, is implicated in the emergence of drug-resistant traits. Within this review, we illuminate contemporary insights into the role of clonal evolution in bladder cancer, elucidating its influence as a driver in tumor initiation, disease progression, and the formidable obstacle of therapy resistance.

The roles of FGFR3 and c-MYC in urothelial bladder cancer

Bladder cancer is one of the most frequently occurring cancers worldwide. At diagnosis, 75% of urothelial bladder cancer cases have non-muscle invasive bladder cancer while 25% have muscle invasive or metastatic disease. Aberrantly activated fibroblast growth factor receptor (FGFR)-3 has been implicated in the pathogenesis of bladder cancer. Activating mutations of FGFR3 are observed in around 70% of NMIBC cases and ~ 15% of MIBCs. Activated FGFR3 leads to ligand-independent receptor dimerization and activation of downstream signaling pathways that promote cell proliferation and survival. FGFR3 is an important therapeutic target in bladder cancer, and clinical studies have shown the benefit of FGFR inhibitors in a subset of bladder cancer patients. c-MYC is a well-known major driver of carcinogenesis and is one of the most commonly deregulated oncogenes identified in human cancers. Studies have shown that the antitumor effects of FGFR inhibition in FGFR3 dependent bladder cancer cells and other FGFR dependent cancers may be mediated through c-MYC, a key downstream effector of activated FGFR that is involved tumorigenesis. This review will summarize the current general understanding of FGFR signaling and MYC alterations in cancer, and the role of FGFR3 and MYC dysregulation in the pathogenesis of urothelial bladder cancer with the possible therapeutic implications.

A Tetravalent Bispecific Antibody Selectively Inhibits Diverse FGFR3 Oncogenic Variants

The receptor tyrosine kinase FGFR3 is frequently mutated in bladder cancer and is a validated therapeutic target. Although pan-FGFR tyrosine kinase inhibitors (TKI) have shown clinical efficacy, toxicity and acquired resistance limit the benefit of these agents. While antibody-based therapeutics can offer superior selectivity than TKIs, conventional ligand-blocking antibodies are usually ineffective inhibitors of constitutively active receptor tyrosine kinases. Furthermore, the existence of multiple oncogenic variants of FGFR3 presents an additional challenge for antibody-mediated blockade. Here, we developed a tetravalent FGFR3×FGFR3 bispecific antibody that inhibited FGFR3 point mutants and fusion proteins more effectively than any of the conventional FGFR3 antibodies that we produced. Each arm of the bispecific antibody contacted two distinct epitopes of FGFR3 through a cis mode of binding. The antibody blocked dimerization of the most common FGFR3 oncogenic variant (S249C extracellular domain mutation) and inhibited the function of FGFR3 variants that are resistant to pan-FGFR TKIs. The antibody was highly effective in suppressing growth of FGFR3-driven tumor models, providing efficacy comparable to that of the FDA-approved TKI erdafitinib. Thus, this bispecific antibody may provide an effective approach for broad and highly selective inhibition of oncogenic FGFR3 variants. Significance: Development of a bispecific antibody that broadly inhibits gain-of-function FGFR3 variants provides a therapeutic strategy to target tumors with oncogenic FGFR3 point mutations and fusions, a particularly difficult case for antibody blockade.

Photodynamic Diagnosis and Therapy in Non-Muscle-Invasive Bladder Cancer

Bladder cancer (BC) possesses distinct molecular profiles that influence progression depending on its biological nature and delivered treatment intensity. Muscle-invasive BC (MIBC) and non-MIBC (NMIBC) demonstrate great intrinsic heterogeneity regarding different prognoses, survival, progression, and treatment outcomes. Transurethral resection of bladder tumor (TURBT) is the standard of care in treating NMIBC and serves both diagnostic and therapeutic purposes despite the prevalent recurrence and progression among many patients. In particular, flat urothelial carcinoma in situ and urothelial carcinoma with lamina propria invasion are the major precursors of MIBC. A new-generation photosensitizer, 5-Aminolevulinic acid (5-ALA), demonstrates high tumor specificity by illuminating the tumor lesion with a specific wavelength of light to produce fluorescence and has been studied for photodynamic diagnosis to detect precise tumor areas by TURBT. Additionally, it has been applied for treatment by producing its cytotoxic reactive oxygen species, as well as screening for urological carcinomas by excreting porphyrin in the blood and urine. Moreover, 5-ALA may contribute to screening before and after TURBT in NMIBC. Here, we summarize the updated evidence and ongoing research on photodynamic technology for NMIBC, providing insight into the potential for improving patient outcomes.

Bladder cancer

Bladder cancer is a global health issue with sex differences in incidence and prognosis. Bladder cancer has distinct molecular subtypes with multiple pathogenic pathways depending on whether the disease is non-muscle invasive or muscle invasive. The mutational burden is higher in muscle-invasive than in non-muscle-invasive disease. Commonly mutated genes include TERT, FGFR3, TP53, PIK3CA, STAG2 and genes involved in chromatin modification. Subtyping of both forms of bladder cancer is likely to change considerably with the advent of single-cell analysis methods. Early detection signifies a better disease prognosis; thus, minimally invasive diagnostic options are needed to improve patient outcomes. Urine-based tests are available for disease diagnosis and surveillance, and analysis of blood-based cell-free DNA is a promising tool for the detection of minimal residual disease and metastatic relapse. Transurethral resection is the cornerstone treatment for non-muscle-invasive bladder cancer and intravesical therapy can further improve oncological outcomes. For muscle-invasive bladder cancer, radical cystectomy with neoadjuvant chemotherapy is the standard of care with evidence supporting trimodality therapy. Immune-checkpoint inhibitors have demonstrated benefit in non-muscle-invasive, muscle-invasive and metastatic bladder cancer. Effective management requires a multidisciplinary approach that considers patient characteristics and molecular disease characteristics.

Hypochondroplasia gain-of-function mutation in FGFR3 causes defective bone mineralization in mice

Hypochondroplasia (HCH) is a mild dwarfism caused by missense mutations in fibroblast growth factor receptor 3 (FGFR3), with the majority of cases resulting from a heterozygous p.Asn540Lys gain-of-function mutation. Here, we report the generation and characterization of the first mouse model (Fgfr3Asn534Lys/+) of HCH to our knowledge. Fgfr3Asn534Lys/+ mice exhibited progressive dwarfism and impairment of the synchondroses of the cranial base, resulting in defective formation of the foramen magnum. The appendicular and axial skeletons were both severely affected and we demonstrated an important role of FGFR3 in regulation of cortical and trabecular bone structure. Trabecular bone mineral density (BMD) of long bones and vertebral bodies was decreased, but cortical BMD increased with age in both tibiae and femurs. These results demonstrate that bones in Fgfr3Asn534Lys/+ mice, due to FGFR3 activation, exhibit some characteristics of osteoporosis. The present findings emphasize the detrimental effect of gain-of-function mutations in the Fgfr3 gene on long bone modeling during both developmental and aging processes, with potential implications for the management of elderly patients with hypochondroplasia and osteoporosis.

Current and emerging therapies for Achondroplasia: The dawn of precision medicine

Achondroplasia is a rare disease affecting bone growth and is caused by a missense mutation in the fibroblast growth factor receptor 3 (FGFR3) gene. In the past few years, there were multiple experimental drugs entering into clinical trials for treating achondroplasia including vosoritide, the first precision medicine approved for this indication. This perspective presents the mechanism of action, benefit, and potential mechanistic limitation of the drugs currently being evaluated in clinical trials for achondroplasia. This article also discusses the potential impact of those drugs not only in increasing the growth of individuals living with achondroplasia but also in improving their quality of life.

Case Report: PD-L1-negative advanced bladder cancer effectively treated with anlotinib and tislelizumab: A report of two cases

Second-line treatment for metastatic or locally advanced urothelial cancer (UC) is limited. Immunotherapy is approved as a second-line treatment for metastatic UC. Its use as a first-line agent is limited to patients who are ineligible for cisplatin-based treatments. The fibroblast growth factor receptor (FGFR) inhibitor, erdafitinib, can be applied as a third-line approach after the failure of these prior treatments in eligible patients. Therefore, it is especially important to combine limited drugs for second-line treatment of advanced or metastatic UC. Anlotinib is a multiple tyrosine kinase inhibitor agent with both anti-angiogenic and FGFR inhibitory effects. For two patients with advanced and metastatic UC, we combined anlotinib and tislelizumab therapy even though there is no indication of its use. We describe two patients with programmed death ligand-1 (PD-L1)-negative advanced bladder cancer, one with FGFR3 mutation and another with FGFR3 wild type. Both patients had progressed after first-line chemotherapy with gemcitabine and cisplatin. We selected anlotinib in combination with tislelizumab, a programmed death-1 (PD-1) immune checkpoint inhibitor, for second-line treatment. Responses were evaluated as partial remission in both cases, who achieved up to 12 months of progression-free survival with no significant adverse events. Two patients with PD-L1-negative UC underwent second-line therapy using tislelizumab in combination with anlotinib, and the efficacy was better than that of tislelizumab alone. These results suggest that anlotinib may act synergistically with tislelizumab in the treatment of UC.

Multiparametric Classification of Non-Muscle Invasive Papillary Urothelial Neoplasms: Combining Morphological, Phenotypical, and Molecular Features for Improved Risk Stratification

Diagnosis and grading of non-invasive papillary urothelial tumors according to the current WHO classification poses some challenges for pathologists. The diagnostic reproducibility of separating low-grade and high-grade lesions is low, which impacts their clinical management. Whereas papillary urothelial neoplasms with low malignant potential (PUN-LMP) and low-grade papillary non-invasive carcinoma (LG-PUC) are comparable and show frequent local recurrence but rarely metastasize, high-grade papillary non-invasive carcinoma (HG-PUC) has a poor prognosis. The main objective of this work is to develop a multiparametric classification to unambiguously distinguish low-grade and high-grade tumors, considering immunohistochemical stains for p53, FGFR3, CK20, MIB-1, p16, p21 and p-HH3, and pathogenic mutations in TP53, FGFR3, TP53, ERCC2, PIK3CA, PTEN and STAG2. We reviewed and analyzed the clinical and histological data of 45 patients with a consensus diagnosis of PUN-LMP (n = 8), non-invasive LG-PUC (n = 23), and HG-PUC (n = 14). The proliferation index and mitotic count assessed with MIB-1 and P-HH3 staining, respectively correlated with grading and clinical behavior. Targeted sequencing confirmed frequent FGFR3 mutations in non-invasive papillary tumors and identified mutations in TP53 as high-risk. Cluster analysis of the different immunohistochemical and molecular parameters allowed a clear separation in two different clusters: cluster 1 corresponding to PUN-LMP and LG-PUC (low MIB-1 and mitotic count/FGFR3 and STAG2 mutations) and cluster 2, HG-PUC (high MIB-1 and mitosis count/CK20 +++ expression, FGFR3 WT and TP53 mutation). Further analysis is required to validate and analyze the reproducibility of these clusters and their biological and clinical implication.

Dual targeting of FGFR3 and ERBB3 enhances the efficacy of FGFR inhibitors in FGFR3 fusion-driven bladder cancer

BACKGROUND

Mutations and fusions in Fibroblast Growth Factor Receptor 3 (FGFR3) occur in 10-20% of metastatic urothelial carcinomas and confer sensitivity to FGFR inhibitors. However, responses to these agents are often short-lived due to the development of acquired resistance. The objective of this study was to identify mechanisms of resistance to FGFR inhibitors in two previously uncharacterised bladder cancer cell lines harbouring FGFR3 fusions and assess rational combination therapies to enhance sensitivity to these agents.

METHODS

Acquired resistance to FGFR inhibitors was generated in two FGFR3 fusion harbouring cell lines, SW780 (FGFR3-BAIAP2L1 fusion) and RT4 (FGFR3-TACC3 fusion), by long-term exposure to the FGFR inhibitor BGJ398. Changes in levels of receptor tyrosine kinases were assessed by phospho-RTK arrays and immunoblotting. Changes in cell viability and proliferation were assessed by the Cell-Titre Glo assay and by propidium iodide staining and FACS analysis.

RESULTS

Long term treatment of FGFR3-fusion harbouring SW780 and RT4 bladder cancer cell lines with the FGFR inhibitor BGJ398 resulted in the establishment of resistant clones. These clones were cross-resistant to the clinically approved FGFR inhibitor erdafitinib and the covalently binding irreversible FGFR inhibitor TAS-120, but remained sensitive to the MEK inhibitor trametinib, indicating resistance is mediated by alternate activation of MAPK signalling. The FGFR inhibitor-resistant SW780 and RT4 lines displayed increased expression of pERBB3, and strikingly, combination treatment with an FGFR inhibitor and the ATP-competitive pan-ERBB inhibitor AZD8931 overcame this resistance. Notably, rapid induction of pERBB3 and reactivation of pERK also occurred in parental FGFR3 fusion-driven lines within 24 h of FGFR inhibitor treatment, and combination treatment with an FGFR inhibitor and AZD8931 delayed the reactivation of pERBB3 and pERK and synergistically inhibited cell proliferation.

CONCLUSIONS

We demonstrate that increased expression of pERBB3 is a key mechanism of adaptive resistance to FGFR inhibitors in FGFR3-fusion driven bladder cancers, and that this also occurs rapidly following FGFR inhibitor treatment. Our findings demonstrate that resistance can be overcome by combination treatment with a pan-ERBB inhibitor and suggest that upfront combination treatment with FGFR and pan-ERBB inhibitors warrants further investigation for FGFR3-fusion harbouring bladder cancers.

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.

RAF1 amplification: an exemplar of MAPK pathway activation in urothelial carcinoma

Despite recent therapeutic gains in the treatment of advanced bladder cancer, the overall survival in patients with metastatic disease remains poor and further therapeutic discovery is needed. Advanced bladder cancer is a molecularly heterogeneous disease, and the identification of driver genetic alterations has led to effective targeted therapeutic agents, such as fibroblast growth factor receptor (FGFR) inhibitors. In this issue of the JCI, Bekele et al. identify a subtype of muscle-invasive bladder cancer (MIBC) that harbors RAF1 amplification. The authors showed that RAF1 inhibition, with pan-RAF inhibitors, and the combination of RAF1 inhibition with MEK inhibition were efficacious in preclinical models harboring RAF1 amplifications as well as in tumors with HRAS and NRAS mutations. This study highlights RAF1 amplification as a driver event in bladder cancer and establishes the central role of the MAPK pathway in bladder tumorigenesis.

Targeted Next-Generation Sequencing of Cancer-Related Genes in a Norwegian Patient Cohort With Head and Neck Squamous Cell Carcinoma Reveals Novel Actionable Mutations and Correlations With Pathological Parameters

Background

Targeted next-generation sequencing (NGS) is increasingly applied in clinical oncology to advance personalized treatment. Despite success in many other tumour types, use of targeted NGS panels for assisting diagnosis and treatment of head and neck squamous cell carcinomas (HNSCC) is still limited.

Aim

The focus of this study was to establish a robust NGS panel targeting most frequent cancer mutations in long-term preserved formalin-fixed paraffin-embedded (FFPE) tissue samples of HNSCC from routine diagnostics.

Materials and Methods

Tumour DNA obtained from archival FFPE tissue blocks of HNSCC patients treated at Haukeland University Hospital between 2003-2016 (n=111) was subjected to mutational analysis using a custom made AmpliSeq Library PLUS panel targeting 31 genes (Illumina). Associations between mutational burden and clinical and pathological parameters were investigated. Mutation and corresponding clinicopathological data from HNSCC were extracted for selected genes from the Cancer Genome Atlas (TCGA) and used for Chi-square and Kaplan-Meier analysis.

Results

The threshold for sufficient number of reads was attained in 104 (93.7%) cases. Although the specific number of PCR amplified reads detected decreased, the number of NGS-annotated mutations did not significantly change with increased tissue preservation time. In HPV-negative carcinomas, mutations were detected mainly in TP53 (73.3%), FAT1 (26.7%) and FLG (16.7%) whereas in HPV-positive, the common mutations were in FLG (24.3%) FAT1 (17%) and FGFR3 (14.6%) genes. Other less common pathogenic mutations, including well reported SNPs were reproducibly identified. Presence of at least one cancer-specific mutations was found to be positively associated with an extensive desmoplastic stroma (p=0.019), and an aggressive type of invasive front (p=0.035), and negatively associated with the degree of differentiation (p=0.041). Analysis of TCGA data corroborated the association between cancer-specific mutations and tumour differentiation and survival analysis showed that tumours with at least one mutation had shorter disease-free and overall survival (p=0.005).

Conclusions

A custom made targeted NGS panel could reliably detect several specific mutations in archival samples of HNSCCs preserved up to 17 years. Using this method novel associations between mutational burden and clinical and pathological parameters were detected and actionable mutations in HPV-positive HNSCC were discovered.

Targetable Pathways in Advanced Bladder Cancer: FGFR Signaling

Bladder cancer is the 10th most commonly diagnosed cancer in the world, accounting for around 573,000 new cases and 213,000 deaths in 2020. The current standard treatment for locally advanced bladder cancer is neoadjuvant cisplatin (NAC)-based chemotherapy followed by cystectomy. The significant progress being made in the genomic and molecular understandings of bladder cancer has uncovered the genetic alterations and signaling pathways that drive bladder cancer progression. These developments have led to a dramatic increase in the evaluation of molecular agents targeting at these alterations. One example is Erdafitinib, a first-in-class FGFR inhibitor being approved as second-line treatment for locally advanced or metastatic urothelial carcinoma with FGFR mutations. Immunotherapy has also been approved as second-line treatment for advanced and metastatic bladder cancer. Preclinical studies suggest targeted therapy combined with immunotherapy has the potential to markedly improve patient outcome. Given the prevalence of FGFR alternations in bladder cancer, here we review recent preclinical and clinical studies on FGFR inhibitors and analyze possible drug resistance mechanisms to these agents. We also discuss FGFR inhibitors in combination with other therapies and its potential to improve outcome.

Comprehensive functional evaluation of variants of fibroblast growth factor receptor genes in cancer

Various genetic alterations of the fibroblast growth factor receptor (FGFR) family have been detected across a wide range of cancers. However, inhibition of FGFR signaling by kinase inhibitors demonstrated limited clinical effectiveness. Herein, we evaluated the transforming activity and sensitivity of 160 nonsynonymous FGFR mutations and ten fusion genes to seven FGFR tyrosine kinase inhibitors (TKI) using the mixed-all-nominated-in-one (MANO) method, a high-throughput functional assay. The oncogenicity of 71 mutants was newly discovered in this study. The FGFR TKIs showed anti-proliferative activities against the wild-type FGFRs and their fusions, while several hotspot mutants were relatively resistant to those TKIs. The drug sensitivities assessed with the MANO method were well concordant with those evaluated using in vitro and in vivo assays. Comprehensive analysis of published FGFR structures revealed a possible mechanism through which oncogenic FGFR mutations reduce sensitivity to TKIs. It was further revealed that recurrent compound mutations within FGFRs affect the transforming potential and TKI-sensitivity of corresponding kinases. In conclusion, our study suggests the importance of selecting suitable inhibitors against individual FGFR variants. Moreover, it reveals the necessity to develop next-generation FGFR inhibitors, which are effective against all oncogenic FGFR variants.

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.

Targeting Drugs Against Fibroblast Growth Factor(s)-Induced Cell Signaling

BACKGROUND

The fibroblast growth factor (FGF) family is comprised of 23 highly regulated monomeric proteins that regulate a plethora of developmental and pathophysiological processes, including tissue repair, wound healing, angiogenesis, and embryonic development. Binding of FGF to fibroblast growth factor receptor (FGFR), a tyrosine kinase receptor, is facilitated by a glycosaminoglycan, heparin. Activated FGFRs phosphorylate the tyrosine kinase residues that mediate induction of downstream signaling pathways, such as RAS-MAPK, PI3K-AKT, PLCγ, and STAT. Dysregulation of the FGF/FGFR signaling occurs frequently in cancer due to gene amplification, FGF activating mutations, chromosomal rearrangements, integration, and oncogenic fusions. Aberrant FGFR signaling also affects organogenesis, embryonic development, tissue homeostasis, and has been associated with cell proliferation, angiogenesis, cancer, and other pathophysiological changes.

OBJECTIVE

This comprehensive review will discuss the biology, chemistry, and functions of FGFs, and its current applications toward wound healing, diabetes, repair and regeneration of tissues, and fatty liver diseases. In addition, specific aberrations in FGFR signaling and drugs that target FGFR and aid in mitigating various disorders, such as cancer, are also discussed in detail.

CONCLUSION

Inhibitors of FGFR signaling are promising drugs in the treatment of several types of cancers. The clinical benefits of FGF/FGFR targeting therapies are impeded due to the activation of other RTK signaling mechanisms or due to the mutations that abolish the drug inhibitory activity on FGFR. Thus, the development of drugs with a different mechanism of action for FGF/FGFR targeting therapies is the recent focus of several preclinical and clinical studies.

Molecular and Clinical Insights in Malignant Brenner Tumor of the Testis With Liver Metastases:A Case Report

Malignant Brenner Tumor (mBT) is extremely rare. Although BT are almost exclusive ovarian neoplasms, they may constitute a highly unusual tumor of the testis; in fact, only seven fully documented cases have been reported to date. Because of their rarity, the pathogenesis of these tumors has not been clarified and there is no standard therapeutic approach. We report the first case of epididymal mBT with synchronous, multiple, liver metastases and a very dramatic clinical course. Both primary tumor and metastasis were subjected to mutational analysis of 20 cancer associated genes. Primary tumor showed FGFR3 Tyr375Cys and PIK3CA His1047Arg missense mutations. Both mutations are reported as pathogenic in ClinVar database. The same FGFR3 mutation was present in liver metastasis. Based on these results we believe that the FGFR pathway could be an ideal candidate for personalized treatment, offering hope to a subset of patients with mBT. Personalized approach, including mutational analysis and molecular testing should be required in patients with rare tumors in order to clarify diagnosis and improve therapeutic strategies.

Integrative multi-omics analysis of muscle-invasive bladder cancer identifies prognostic biomarkers for frontline chemotherapy and immunotherapy

Only a subgroup of patients with muscle-invasive bladder cancer (MIBC) are responders toward cisplatin-based chemotherapy and PD-L1 blockade immunotherapy. There is a clinical need to identify MIBC molecular subtypes and biomarkers for patient stratification toward the therapies. Here, we performed an integrative clustering analysis of 388 MIBC samples with multi-omics data and identified basal and luminal/differentiated integrative subtypes and derived a 42 gene panel for classification of MIBC. Using nine additional gene expression data (n = 844), we demonstrated the prognostic value of the 42 basal-luminal genes. The basal subtype was associated with worse overall survival in patients receiving no neoadjuvant chemotherapy (NAC), but better overall survival in patients receiving NAC in two clinical trials. Each of the subtypes could be further divided into chr9 p21.3 normal or loss subgroup. The patients with low expression of MTAP/CDKN2A/2B (indicative of chr9 p21.3 loss) had a significantly lower response rate to anti-PD-L1 immunotherapy and worse survival than the patients with high expression of MTAP/CDKN2A/2B. This integrative analysis reveals intrinsic MIBC subtypes and biomarkers with prognostic value for the frontline therapies.

FGFR3 – a Central Player in Bladder Cancer Pathogenesis?

The identification of mutations in FGFR3 in bladder tumors in 1999 led to major interest in this receptor and during the subsequent 20 years much has been learnt about the mutational profiles found in bladder cancer, the phenotypes associated with these and the potential of this mutated protein as a target for therapy. Based on mutational and expression data, it is estimated that >80% of non-muscle-invasive bladder cancers (NMIBC) and ∼40% of muscle-invasive bladder cancers (MIBC) have upregulated FGFR3 signalling, and these frequencies are likely to be even higher if alternative splicing of the receptor, expression of ligands and changes in regulatory mechanisms are taken into account. Major efforts by the pharmaceutical industry have led to development of a range of agents targeting FGFR3 and other FGF receptors. Several of these have entered clinical trials, and some have presented very encouraging early results in advanced bladder cancer. Recent reviews have summarised the drugs and related clinical trials in this area. This review will summarise what is known about the effects of FGFR3 and its mutant forms in normal urothelium and bladder tumors, will suggest when and how this protein contributes to urothelial cancer pathogenesis and will highlight areas that may benefit from further study.

FGFR3△7-9 promotes tumor progression via the phosphorylation and destabilization of ten-eleven translocation-2 in human hepatocellular carcinoma

Overexpression of fibroblast growth factor receptor 3 (FGFR3) correlates with more severe clinical features of hepatocellular carcinoma (HCC). Our previous study has shown that FGFR3_∆7–9, a novel splicing mutation of FGFR3, contributes significantly to HCC malignant character, but the epigenetic mechanism is still elusive. In this study, through mass spectrometry and co-immunoprecipitation studies, we discover a close association between FGFR3_∆7–9 and the DNA demethylase Ten-Eleven Translocation-2 (TET2). Unlike other certain types of cancer, mutation of TET2 is rare in HCC. However, activation of FGFR3_∆7–9 by FGF1 dramatically shortens TET2 half-life. FGFR3_∆7–9, but not wild-type FGFR3, directly interacts with TET2 and phosphorylates TET2 at Y1902 site, leading to the ubiquitination and proteasome-mediated degradation of TET2. Overexpression of a phospho-deficient mutant TET2 (Y1902F) significantly reduces the oncogenic potential of FGFR3_∆7–9 in vitro and in vivo. Furthermore, FGFR3_∆7–9 significantly enhances HCC cell proliferation through the TET2-PTEN-AKT pathway. Specifically, TET2 offsets the elevation of p-AKT level induced by FGFR3_∆7–9 through directly binding to PTEN promoter and increasing 5-hmC. Therefore, through phosphorylation and inhibition of TET2, FGFR3_∆7–9 reduces PTEN expression and substantiates AKT activation to stimulate HCC proliferation. Together, this study identifies TET2 as a key regulator of the oncogenic role of FGFR3_∆7–9 in HCC carcinogenesis and sheds light on new therapeutic strategies for HCC treatment.

Identification of Four Immune Subtypes in Bladder Cancer Based on Immune Gene Sets

Molecular classification of bladder cancer is becoming increasingly important for its clinical management. And, the current classifications are primarily based on gene expression profiles. We identified four immunotypes of bladder cancer (referred to as C1–C4) based on gene expression profiles performed by immune-related gene sets in three independent data sets, and proved that this classification is effective and reproducible. We found that C2 is an immune-infiltrating type and C4 is an immune “desert” type. These types are characterized by the up- and downregulation of genes encoding numerous immune checkpoint proteins and HLA and regulating human immune cell subgroups. The survival rate was better for the C2 subtype than for other subtypes. We believe that this can be explained by the antitumor effects of CD4 memory T cells and CD8 T cells as well as their ability to circumvent M0 macrophage antitumor immunity. In addition, C2 was most sensitive to not only anti-PD-1 immunosuppressive therapy, but also conventional chemotherapeutics such as gemcitabine and bleomycin. The C4 subtype was most sensitive to the chemotherapy drugs cisplatin and doxorubicin. This theoretical framework may guide the personalized treatment of bladder cancer in the future. It is worth noting that the C2 immune infiltration type positively correlates with a variety of stromal components, such as enrichment of endothelial cells and fibroblasts, epithelial-mesenchymal transition, and angiogenesis, together with enrichment of seven kinds of stem cells. We further identified tumor-related JAK-STAT and other signaling pathways in the C2 subtype, along with important mutations in the proteins involved in these pathways, revealing the complex mechanism underlying tumor immune escape. Our results, and particularly the identification of hub genes specific to the C2 and C4 subtypes, provide a reference for the development of immunotherapeutic agents against bladder cancer.

Reassessment of p53 immunohistochemistry thresholds in invasive high grade bladder cancer shows a better correlation with TP53 and FGFR3 mutations

FGFR3 mutations are frequently mutually exclusive of TP53 mutations in invasive high grade urothelial carcinoma (HGUC) and p53 immunohistochemistry is often used as a surrogate for TP53 mutations. A 10 % staining cut off has been used in HGUC for designation as p53 positive or negative however, a novel contemporary method we have previously proposed (0% or >50 % - abnormal vs. 1-49 % - wild type) has shown significant correlation with oncologic outcome as well. We aimed to compare how a ≥10 % vs. 0 % and ≥ 50 % cut off p53 assessment method correlates with TP53 and FGFR3 mutation status. Tissue microarrays created from three retrospective cohorts (two cystectomy cohorts (cohort A, n = 206 and cohort B, n = 91; one T1 transurethral resection cohort (cohort C, n = 47)) were stained with p53 and scored by two blinded reviewers using both p53 scoring schemes. 50 cases from cohort A were assessed for TP53 and FGFR3 mutation status using next generation sequencing and FGFR3 mutation status was separately assessed in cohorts B and C using SNaPshot methodology. 202 (58.7 %) and 142 (41.3 %) cases showed abnormal and wild type p53 staining, respectively. Using the 10 % cut off, 254 cases were positive (73.8 %) and 90 cases were negative (26.2 %). 27 (14.4 %) and 15 (30 %) assessed cases demonstrated FGFR3 and TP53 mutations, respectively; 19/27 FGFR3 mutated showed a wild type pattern of p53 expression while 15/15 TP53 mutated tumours showed an abnormal pattern of p53 expression. There was a significant correlation between the contemporary p53 scoring scheme and TP53 and FGFR3 mutations (p < 0.0001 and p = 0.002, respectively). Improved sensitivity, specificity, positive predictive value, and negative predictive value for TP53 mutation was also seen compared to the 10 % cut off; specifically, the sensitivity and negative predictive value were 100 %. These findings might be of clinical relevance in the era of precision medicine.

Urothelial carcinoma: the development of FGFR inhibitors in combination with immune checkpoint inhibitors

INTRODUCTION

The recent approval of erdafitinib and the emergence of other potent and selective fibroblast growth factor receptor (FGFR) inhibitors (FGFRi's) are shifting the treatment paradigm for patients with advanced urothelial carcinoma (UC) harboring FGFR3 alterations. Whether such therapies can, and should, be combined with immune checkpoint inhibitors (ICI's) is an area of major research interest. Areas covered: Herein, we review the FGFR signaling pathway and impact of altered FGFR signaling on UC tumorigenesis, the clinical development of FGFRi's, the rationale for FGFRi-ICI combinations, current trials, and future directions. Expert opinion: FGFR3 altered UCs are not less responsive to ICI's compared with FGFR3 wild-type (WT) tumors. However, FGFR3 altered tumors may exhibit distinct immunobiology compared with WT tumors that could potentially be exploited therapeutically. Given these considerations along with the clinical non-cross resistance of these therapeutic classes, clinical investigation of regimens combining FGFR3i and ICI is warranted.

Targeting the Src Pathway Enhances the Efficacy of Selective FGFR Inhibitors in Urothelial Cancers with FGFR3 Alterations

Selective FGFR inhibitors such as infigratinib (BGJ398) and erdafitinib (JNJ-42756493) have been evaluated in clinical trials for cancers with FGFR3 molecular alterations, particularly in urothelial carcinoma patients. However, a substantial proportion of these patients (up to 50%) display intrinsic resistance to these drugs and receive minimal clinical benefit. There is thus an unmet need for alternative therapeutic strategies to overcome primary resistance to selective FGFR inhibitors. In this study, we demonstrate that cells expressing cancer-associated activating FGFR3 mutants and the FGFR3-TACC3 fusion showed primary resistance to infigratinib in long-term colony formation assays in both NIH-3T3 and urothelial carcinoma models. We find that expression of these FGFR3 molecular alterations resulted in elevated constitutive Src activation compared to wildtype FGFR3 and that cells co-opted this pathway as a means to achieve intrinsic resistance to infigratinib. Targeting the Src pathway with low doses of the kinase inhibitor dasatinib synergistically sensitized multiple urothelial carcinoma lines harbouring endogenous FGFR3 alterations to infigratinib. Our data provide preclinical rationale that supports the use of dasatinib in combination with selective FGFR inhibitors as a means to overcome intrinsic drug resistance in the salvage therapy setting in urothelial cancer patients with FGFR3 molecular alterations.

ETV5 links the FGFR3 and Hippo signalling pathways in bladder cancer

Activating mutations of fibroblast growth factor receptor 3 (FGFR3) are common in urothelial carcinoma of the bladder (UC). Silencing or inhibition of mutant FGFR3 in bladder cancer cell lines is associated with decreased malignant potential, confirming its important driver role in UC. However, understanding of how FGFR3 activation drives urothelial malignant transformation remains limited. We have previously shown that mutant FGFR3 alters the cell-cell and cell-matrix adhesion properties of urothelial cells, resulting in loss of contact-inhibition of proliferation. In this study, we investigate a transcription factor of the ETS-family, ETV5, as a putative effector of FGFR3 signalling in bladder cancer. We show that FGFR3 signalling induces a MAPK/ERK-mediated increase in ETV5 levels, and that this results in increased level of TAZ, a co-transcriptional regulator downstream of the Hippo signalling pathway involved in cell-contact inhibition. We also demonstrate that ETV5 is a key downstream mediator of the oncogenic effects of mutant FGFR3, as its knockdown in FGFR3-mutant bladder cancer cell lines is associated with reduced proliferation and anchorage-independent growth. Overall this study advances our understanding of the molecular alterations occurring during urothelial malignant transformation and indicates TAZ as a possible therapeutic target in FGFR3-dependent bladder tumours.

Beyond BCG: the approaching era of personalised bladder-sparing therapies for non-muscle-invasive urothelial cancers

Progress in the management of non-muscle invasive bladder cancer has been slow. Despite longstanding use of intravesical therapies (e.g., Bacille Calmette-Guerin; BCG) to complement cystoscopic resection of high-grade lesions, many patients still develop recurrences requiring cystectomy, while others suffer side-effects of BCG without definite benefit. Many questions remain: for example, how many patients receive intravesical prophylaxis without efficacy? Which high-risk patients are best managed with early cystectomy? Could systemic therapies and/or radiotherapy extend bladder preservation times? Such questions may soon be refined by clinicopathologic non-muscle invasive bladder cancer signatures that predict sensitivity to cytotoxic, immune and targeted therapies. Hypothesis-based trials using these signatures should lead to more rational adjuvant treatments, longer bladder preservation times, and better quality of life for patients.

FGFR3 mutation increases bladder tumourigenesis by suppressing acute inflammation

Recent studies of muscle-invasive bladder cancer show that FGFR3 mutations are generally found in a luminal papillary tumour subtype that is characterised by better survival than other molecular subtypes. To better understand the role of FGFR3 in invasive bladder cancer, we examined the process of tumour development induced by the tobacco carcinogen OH-BBN in genetically engineered models that express mutationally activated FGFR3 S249C or FGFR3 K644E in the urothelium. Both occurrence and progression of OH-BBN-driven tumours were increased in the presence of an S249C mutation compared to wild-type control mice. Interestingly, at an early tumour initiation stage, the acute inflammatory response in OH-BBN-treated bladders was suppressed in the presence of an S249C mutation. However, at later stages of tumour progression, increased inflammation was observed in S249C tumours, long after the carcinogen administration had ceased. Early-phase neutrophil depletion using an anti-Ly6G monoclonal antibody resulted in an increased neutrophil-to-lymphocyte ratio at later stages of pathogenesis, indicative of enhanced tumour pathogenesis, which supports the hypothesis that suppression of acute inflammation could play a causative role. Statistical analyses of correlation showed that while initial bladder phenotypes in morphology and inflammation were FGFR3-dependent, increased levels of inflammation were associated with tumour progression at the later stage. This study provides a novel insight into the tumour-promoting effect of FGFR3 mutations via regulation of inflammation at the pre-tumour stage in the bladder. Copyright © 2018 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

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.

The evolution of bladder cancer genomics: What have we learned and how can we use it?

BACKGROUND

With advancements in molecular biology techniques, great progress has been made in the understanding of urothelial carcinoma pathogenesis.

OBJECTIVE

To examine the historic description of molecular alterations in bladder cancer and their evolution towards our current comprehension of the biology of the disease.

RESULTS

Historically, a two-pathway model was described from histological and cytogenetic studies: low-grade papillary non-muscle invasive bladder cancers (NMIBC) were described to arise from epithelial hyperplasia with loss of chromosome 9 as an early event, whereas muscle-invasive bladder cancers (MIBC) were considered to develop from dysplasia, associated with genetic instability. Although there could be connections between the 2 pathways, NMIBC and MIBC were largely believed to develop secondary to different molecular alterations. Next-generation sequencing has allowed important insights into cancer biology and a better understanding of the pathways involved in bladder cancer pathogenesis and heterogeneity. Urothelial carcinoma has been found to have a high frequency of somatic mutations compared to other solid tumors, including several mutations in multiple signaling pathways, such as cell cycle regulators (TP53, RB1), RTK/RAS/RAF pathway, PI3K/AKT/mTOR pathway and TERT gene promoter. Epigenetic changes and mutations in chromatin remodeling genes are especially frequent in bladder cancer. Mutations in FGFR3 and KDM6A are more common in NMIBC than in MIBC, whereas mutations in TP53 and KMT2D are more common in MIBC, suggesting the previously hypothesized 2 different pathways, with a subset of tumors progressing from NMIBC to MIBC. Using comprehensive RNA expression profiling studies, at least 5 subtypes of bladder cancer have been identified, the most fundamental division being Basal/Squamous-like and Luminal. These subtypes have different prognoses, natural histories and responses to systemic treatments: Luminal subtypes are enriched with papillary histology and have a better prognosis, while Basal/Squamous-like subtypes are enriched with squamous features, are associated with advanced stage at presentation, and portend a worse prognosis.

CONCLUSION

This new understanding of bladder cancer will optimistically translate into better understanding of this heterogeneous disease and lead to improvement in patient outcome and quality of life through better tailored treatments.

Unique signalling connectivity of FGFR3-TACC3 oncoprotein revealed by quantitative phosphoproteomics and differential network analysis

The FGFR3-TACC3 fusion is an oncogenic driver in diverse malignancies, including bladder cancer, characterized by upregulated tyrosine kinase activity. To gain insights into distinct properties of FGFR3-TACC3 down-stream signalling, we utilised telomerase-immortalised normal human urothelial cell lines expressing either the fusion or wild-type FGFR3 (isoform IIIb) for subsequent quantitative proteomics and network analysis. Cellular lysates were chemically labelled with isobaric tandem mass tag reagents and, after phosphopeptide enrichment, liquid chromatography-high mass accuracy tandem mass spectrometry (LC-MS/MS) was used for peptide identification and quantification. Comparison of data from the two cell lines under non-stimulated and FGF1 stimulated conditions and of data representing physiological stimulation of FGFR3 identified about 200 regulated phosphosites. The identified phosphoproteins and quantified phosphosites were further analysed in the context of functional biological networks by inferring kinase-substrate interactions, mapping these to a comprehensive human signalling interaction network, filtering based on tissue-expression profiles and applying disease module detection and pathway enrichment methods. Analysis of our phosphoproteomics data using these bioinformatics methods combined into a new protocol-Disease Relevant Analysis of Genes On Networks (DRAGON)-allowed us to tease apart pathways differentially involved in FGFR3-TACC3 signalling in comparison to wild-type FGFR3 and to investigate their local phospho-signalling context. We highlight 9 pathways significantly regulated only in the cell line expressing FGFR3-TACC3 fusion and 5 pathways regulated only by stimulation of the wild-type FGFR3. Pathways differentially linked to FGFR3-TACC3 fusion include those related to chaperone activation and stress response and to regulation of TP53 expression and degradation that could contribute to development and maintenance of the cancer phenotype.

Genetic Alterations in the Molecular Subtypes of Bladder Cancer: Illustration in the Cancer Genome Atlas Dataset

CONTEXT

Recent whole genome mRNA expression profiling studies revealed that bladder cancers can be grouped into molecular subtypes, some of which share clinical properties and gene expression patterns with the intrinsic subtypes of breast cancer and the molecular subtypes found in other solid tumors. The molecular subtypes in other solid tumors are enriched with specific mutations and copy number aberrations that are thought to underlie their distinct progression patterns, and biological and clinical properties.

OBJECTIVE

The availability of comprehensive genomic data from The Cancer Genome Atlas (TCGA) and other large projects made it possible to correlate the presence of DNA alterations with tumor molecular subtype membership. Our overall goal was to determine whether specific DNA mutations and/or copy number variations are enriched in specific molecular subtypes.

EVIDENCE

We used the complete TCGA RNA-seq dataset and three different published classifiers developed by our groups to assign TCGA's bladder cancers to molecular subtypes, and examined the prevalence of the most common DNA alterations within them. We interpreted the results against the background of what was known from the published literature about the prevalence of these alterations in nonmuscle-invasive and muscle-invasive bladder cancers.

EVIDENCE SYNTHESIS

The results confirmed that alterations involving RB1 and NFE2L2 were enriched in basal cancers, whereas alterations involving FGFR3 and KDM6A were enriched in luminal tumors.

CONCLUSIONS

The results further reinforce the conclusion that the molecular subtypes of bladder cancer are distinct disease entities with specific genetic alterations.

PATIENT SUMMARY

Our observation showed that some of subtype-enriched mutations and copy number aberrations are clinically actionable, which has direct implications for the clinical management of patients with bladder cancer.

Bladder cancer

Bladder cancer is a highly prevalent disease and is associated with substantial morbidity, mortality and cost. Environmental or occupational exposures to carcinogens, especially tobacco, are the main risk factors for bladder cancer. Most bladder cancers are diagnosed after patients present with macroscopic haematuria, and cases are confirmed after transurethral resection of bladder tumour (TURBT), which also serves as the first stage of treatment. Bladder cancer develops via two distinct pathways, giving rise to non-muscle-invasive papillary tumours and non-papillary (solid) muscle-invasive tumours. The two subtypes have unique pathological features and different molecular characteristics. Indeed, The Cancer Genome Atlas project identified genetic drivers of muscle-invasive bladder cancer (MIBC) as well as subtypes of MIBC with distinct characteristics and therapeutic responses. For non-muscle-invasive bladder cancer (NMIBC), intravesical therapies (primarily Bacillus Calmette-Guérin (BCG)) with maintenance are the main treatments to prevent recurrence and progression after initial TURBT; additional therapies are needed for those who do not respond to BCG. For localized MIBC, optimizing care and reducing morbidity following cystectomy are important goals. In metastatic disease, advances in our genetic understanding of bladder cancer and in immunotherapy are being translated into new therapies.

Vulvar Squamous Cell Carcinoma (VSCC) as Two Diseases: HPV Status Identifies Distinct Mutational Profiles Including Oncogenic Fibroblast Growth Factor Receptor 3

Purpose: Patients with advanced or recurrent invasive vulvar squamous cell carcinoma (VSCC) have limited treatment options and a grave prognosis. Understanding the genomic landscape may facilitate the identification of new therapies and improve clinical outcomes.Experimental Design: A retrospective chart review and molecular analysis of patients with VSCC from 2000 to 2016 was performed at the Ottawa Hospital Research Institute. The presence of oncogenic human papillomavirus (HPV) was determined by nested PCR and amplified DNA was sequenced using the Ion AmpliSeq Cancer Hotspot v2 Panel. The patients were divided into two groups according to HPV status (HPV-positive versus HPV-negative) and clinical outcome correlated with mutation status using descriptive statistics.Results: In 43 VSCC patients, there was a high mutation rate in both HPV-positive (73%) and HPV-negative (90%) disease with the two subgroups expressing distinct genetic profiles. HPV-positive tumors were characterized by oncogenic mutations in PIK3CA (27%), FGFR3 (14%), and PTEN (9%), whereas HPV-negative tumors were found to have mutations in TP53 (57%), HRAS (24%), PI3KCA (19%), and CDKN2A (14%). Mutation S249C in FGFR3 occurred in 14% of HPV-positive tumors. While there were notable differences in the occurrence of TP53, HRAS, PTEN, and FGFR3 mutations according to HPV status, only the rate of TP53 mutations was statistically significant (P = 0.0004). No significant difference in prognosis was found between patients with HPV-positive and HPV-negative VSCC.Conclusions: HPV-positive VSCC is characterized by oncogenic FGFR3 mutations that helps classify this subtype as a separate disease. Inhibitors of FGFR3 merit consideration as a therapeutic strategy in this neglected cancer in women. Clin Cancer Res; 23(15); 4501-10. ©2017 AACR.

ASP5878, a selective FGFR inhibitor, to treat FGFR3-dependent urothelial cancer with or without chemoresistance

FGF/FGFR gene aberrations such as amplification, mutation and fusion are associated with many types of human cancers including urothelial cancer. FGFR kinase inhibitors are expected to be a targeted therapy for urothelial cancer harboring FGFR3 gene alternations. ASP5878, a selective inhibitor of FGFR1, 2, 3 and 4 under clinical investigation, selectively inhibited cell proliferation of urothelial cancer cell lines harboring FGFR3 point mutation or fusion (UM-UC-14, RT-112, RT4 and SW 780) among 23 urothelial cancer cell lines. Furthermore, ASP5878 inhibited cell proliferation of adriamycin-resistant UM-UC-14 cell line harboring MDR1 overexpression and gemcitabine-resistant RT-112 cell line. The protein expression of c-MYC, an oncoprotein, in gemcitabine-resistant RT-112 cell line was higher than that in RT-112 parental cell line and ASP5878 decreased the c-MYC expression in both RT-112 parental and gemcitabine-resistant RT-112 cell lines. Once-daily oral administration of ASP5878 exerted potent antitumor activities in UM-UC-14, RT-112 and gemcitabine-resistant RT-112 xenograft models without affecting body weight. These findings suggest that ASP5878 has the potential to be an oral targeted therapy against urothelial cancer harboring FGFR3 fusion or FGFR3 point mutation after the acquisition of gemcitabine- or adriamycin-resistance.

Genetic and Epigenetic Alterations in Bladder Cancer

Bladder cancer is one of the most common cancers worldwide, with a high rate of recurrence and poor outcomes as a result of relapse. Bladder cancer patients require lifelong invasive monitoring and treatment, making bladder cancer one of the most expensive malignancies. Lines of evidence increasingly point to distinct genetic and epigenetic alteration patterns in bladder cancer, even between the different stages and grades of disease. In addition, genetic and epigenetic alterations have been demonstrated to play important roles during bladder tumorigenesis. This review will focus on bladder cancer-associated genomic and epigenomic alterations, which are common in bladder cancer and provide potential diagnostic markers and therapeutic targets for bladder cancer treatment.

Spectrum of genomic alterations in FGFR3: current appraisal of the potential role of FGFR3 in advanced urothelial carcinoma

Molecular analysis has identified subsets of urothelial carcinoma (UC) expressing distinct genetic signatures. Genomic alterations in the oncogenic fibroblast growth factor receptor 3 (FGFR3) pathway are among the most well described in UC and have led to extensive and ongoing investigation of FGFR3-targeted therapies in this disease, although no new drugs have yet been approved. Given the unmet need for effective treatments in advanced and metastatic UC, a better understanding of the known molecular alterations of FGFR3 and of the previous and ongoing clinical investigations of this promising target in UC deserves attention. The objective of the present review is to describe the landscape of alterations and biology of FGFR3 in UC, comprehensively summarize the current state of UC clinical trials of FGFR3 inhibitors, and discuss future therapeutic applications. Using the Pubmed and Clinicaltrials.gov databases, articles describing the spectrum and biological activity of FGFR3 genomic alterations and trials of FGFR3 inhibitors in UC were identified. Search terms included 'FGFR3 genomic alterations' and 'urothelial cancer' or 'bladder cancer'. Genomic alterations, including translocations and activating mutations, are increasingly described in advanced and metastatic UC. The majority of clinical trials have been performed in unselected populations; however, recent studies have reported encouraging preliminary data. We argue that routine use of molecular genomic tumour analysis in UC may inform selection of patients for appropriate trials and we further investigate the potential of FGFR3 as a meaningful clinical target for this difficult disease.

A place for precision medicine in bladder cancer: targeting the FGFRs

Bladder tumors show diverse molecular features and clinical outcome. Muscle-invasive bladder cancer has poor prognosis and novel approaches to systemic therapy are urgently required. Non-muscle-invasive bladder cancer has good prognosis, but high recurrence rate and the requirement for life-long disease monitoring places a major burden on patients and healthcare providers. Studies of tumor tissues from both disease groups have identified frequent alterations of FGFRs, including mutations of FGFR3 and dysregulated expression of FGFR1 and FGFR3 that suggest that these may be valid therapeutic targets. We summarize current understanding of the molecular alterations affecting these receptors in bladder tumors, preclinical studies validating them as therapeutic targets, available FGFR-targeted agents and results from early clinical trials in bladder cancer patients.

FGFR3-TACC3 fusion proteins act as naturally occurring drivers of tumor resistance by functionally substituting for EGFR/ERK signaling

The epidermal growth factor receptor (EGFR) is a clinically validated target in head and neck squamous cell carcinoma (HNSCC), where EGFR-blocking antibodies are approved for first-line treatment. However, as with other targeted therapies, intrinsic/acquired resistance mechanisms limit efficacy. In the FaDu HNSCC xenograft model, we show that combined blockade of EGFR and ERBB3 promotes rapid tumor regression, followed by the eventual outgrowth of resistant cells. RNA sequencing revealed that resistant cells express FGFR3-TACC3 fusion proteins, which were validated as drivers of the resistant phenotype by several approaches, including CRISPR-mediated inactivation of FGFR3-TACC3 fusion genes. Interestingly, analysis of signaling in resistant cell lines demonstrated that FGFR3-TACC3 fusion proteins promote resistance by preferentially substituting for EGFR/RAS/ERK signaling rather than ERBB3/PI3K/AKT signaling. Furthermore, although FGFR3-TACC3 fusion proteins promote resistance of additional EGFR-dependent HNSCC and lung cancer cell lines to EGFR blockade, they are unable to compensate for inhibition of PI3K signaling in PIK3CA-mutant HNSCC cell lines. Validation of FGFR3-TACC3 fusion proteins as endogenous drivers of resistance in our screen provides strong evidence that these fusions are capable of substituting for EGFR signaling. Thus, FGFR3-TACC3 fusion proteins may represent a novel mechanism of acquired resistance in EGFR-dependent cancers of multiple cell lineages.

Phenotypic and Signaling Consequences of a Novel Aberrantly Spliced Transcript FGF Receptor-3 in Hepatocellular Carcinoma

Fibroblast growth factor receptor 3 (FGFR3) plays important roles in cell proliferation, differentiation, and angiogenesis. FGFR3 is abnormally upregulated in hepatocellular carcinoma (HCC), where it correlates positively with clinicopathologic index, HCC differentiation, and advanced nuclear grade. In this study, we describe an aberrantly spliced transcript of FGFR3, termed FGFR3Δ7-9, was identified as a high frequency even in HCC. FGFR3Δ7-9 lacks exons encoding the immunoglobulin-like III domain and promoted the proliferation, migration, and metastasis of HCC cells both in vitro and in vivo Coimmunoprecipation and surface plasmon resonance assays demonstrated that the binding affinity of the aberrant FGFR3Δ7-9 receptor to FGFs was significantly higher than wild-type FGFR3IIIc Furthermore, FGFR3Δ7-9 could be self-activated by homodimerization and autophosphorylation even in the absence of ligand. Finally, FGFR3Δ7-9 more potently induced phosphorylation of the ERK and AKT kinases, leading to abnormal downstream signaling through the ERK and PI3K/AKT/mTOR pathways. FGFR3Δ7-9 also upregulated the metastasis-associated molecules Snail, MMP-9, and downregulated E-cadherin, which associated directly with FGFR3Δ7-9 Thus, as a ligand-dependent or -independent receptor, FGFR3Δ7-9 exerted multiple potent oncogenic functions in HCC cells, including proliferation, migration, and lung metastatic capacity. Overall, FGFR3 mRNA missplicing in HCC contributes significantly to its malignant character, with implications for therapeutic targeting. Cancer Res; 76(14); 4205-15. ©2016 AACR.

Landscape of activating cancer mutations in FGFR kinases and their differential responses to inhibitors in clinical use

Frequent genetic alterations discovered in FGFRs and evidence implicating some as drivers in diverse tumors has been accompanied by rapid progress in targeting FGFRs for anticancer treatments. Wider assessment of the impact of genetic changes on the activation state and drug responses is needed to better link the genomic data and treatment options. We here apply a direct comparative and comprehensive analysis of FGFR3 kinase domain variants representing the diversity of point-mutations reported in this domain. We reinforce the importance of N540K and K650E and establish that not all highly activating mutations (for example R669G) occur at high-frequency and conversely, that some "hotspots" may not be linked to activation. Further structural characterization consolidates a mechanistic view of FGFR kinase activation and extends insights into drug binding. Importantly, using several inhibitors of particular clinical interest (AZD4547, BGJ-398, TKI258, JNJ42756493 and AP24534), we find that some activating mutations (including different replacements of the same residue) result in distinct changes in their efficacy. Considering that there is no approved inhibitor for anticancer treatments based on FGFR-targeting, this information will be immediately translatable to ongoing clinical trials.

Comparative Aspects of BRAF Mutations in Canine Cancers

Activating mutations of the BRAF gene lead to constitutive activation of the MAPK pathway. The characterization and discovery of BRAF mutations in a variety of human cancers has led to the development of specific inhibitors targeting the BRAF/MAPK pathway and dramatically changed clinical outcomes in BRAF-mutant melanoma patients. Recent discovery of BRAF mutation in canine cancers underscores the importance of MAPK pathway activation as an oncogenic molecular alteration evolutionarily conserved between species. A comparative approach using the domestic dog as a spontaneous cancer model will provide new insights into the dysregulation of BRAF/MAPK pathway in carcinogenesis and facilitate in vivo studies to evaluate therapeutic strategies targeting this pathway's molecules for cancer therapy. The BRAF mutation in canine cancers may also represent a molecular marker and therapeutic target in veterinary oncology. This review article summarizes the current knowledge on BRAF mutations in human and canine cancers and discusses the potential applications of this abnormality in veterinary oncology.

Redesigning a Monospecific Anti-FGFR3 Antibody to Add Selectivity for FGFR2 and Expand Antitumor Activity

FGF receptors (FGFR) are attractive candidate targets for cancer therapy because they are dysregulated in several human malignancies. FGFR2 and FGFR3 can be inhibited potentially without disrupting adult tissue homeostasis. In contrast, blocking the closely related FGFR1 and FGFR4, which regulate specific metabolic functions, carries a greater safety risk. An anti-FGFR3 antibody was redesigned here to create function-blocking antibodies that bind with dual specificity to FGFR3 and FGFR2 but spare FGFR1 and FGFR4. R3Mab, a previously developed monospecific anti-FGFR3 antibody, was modified via structure-guided phage display and acquired additional binding to FGFR2. The initial variant was trispecific, binding tightly to FGFR3 and FGFR2 and moderately to FGFR4, while sparing FGFR1. The X-ray crystallographic structure indicated that the antibody variant was bound to a similar epitope on FGFR2 as R3Mab on FGFR3. The antibody was further engineered to decrease FGFR4-binding affinity while retaining affinity for FGFR3 and FGFR2. The resulting dual-specific antibodies blocked FGF binding to FGFR3 and FGFR2 and inhibited downstream signaling. Moreover, they displayed efficacy in mice against human tumor xenografts overexpressing FGFR3 or FGFR2. Thus, a monospecific antibody can be exquisitely tailored to confer or remove binding to closely related targets to expand and refine therapeutic potential.

Molecular biology of bladder cancer: new insights into pathogenesis and clinical diversity

Urothelial carcinoma of the bladder comprises two long-recognized disease entities with distinct molecular features and clinical outcome. Low-grade non-muscle-invasive tumours recur frequently but rarely progress to muscle invasion, whereas muscle-invasive tumours are usually diagnosed de novo and frequently metastasize. Recent genome-wide expression and sequencing studies identify genes and pathways that are key drivers of urothelial cancer and reveal a more complex picture with multiple molecular subclasses that traverse conventional grade and stage groupings. This improved understanding of molecular features, disease pathogenesis and heterogeneity provides new opportunities for prognostic application, disease monitoring and personalized therapy.