Fibroblast growth factor receptor (FGFR) genetic alterations are frequently observed in cancer, suggesting that FGFR inhibition may be a promising therapy in patients harboring these lesions. Identification of predictive and pharmacodynamic biomarkers to select and monitor patients most likely to respond to FGFR inhibition will be the key to clinical development of this class of agents. Sensitivity to FGFR inhibition and correlation with FGFR pathway activation status were determined in molecularly annotated panels of cancer cell lines and xenograft models. Pathway inhibition in response to FGFR inhibitor treatment was assessed in cell lines (both in vitro and in vivo) and in samples from patients treated with the FGFR inhibitor JNJ-42756493 (erdafitinib). Frequency of FGFR aberrations was assessed in a panel of NSCLC, breast, prostate, ovarian, colorectal, and melanoma human tumor tissue samples. FGFR translocations and gene amplifications present in clinical specimens were shown to display potent transforming activity associated with constitutive pathway activation. Tumor cells expressing these FGFR activating mutants displayed sensitivity to the selective FGFR inhibitor erdafitinib and resulted in suppression of FGFR phosphorylation and downstream signal transduction. Clinically, patients receiving erdafitinib showed decreased Erk phosphorylation in tumor biopsies and elevation of serum phosphate. In a phase I study, a heavily pretreated bladder cancer patient with an FGFR3-TACC3 translocation experienced a partial response when treated with erdafitinib. This preclinical study confirmed pharmacodynamics and identified new predictive biomarkers to FGFR inhibition with erdafitinib and supports further clinical evaluation of this compound in patients with FGFR genetic alterations.

Autocrine or paracrine constitutive Wnt pathway activation occurs at a high frequency in several tumor types. The R-spondin (RSPO) protein family is comprised of four secreted growth factors. The four paralogs share 40-60% pairwise amino acid sequence identity and are predicted to share substantial structural homology. RSPO proteins are involved in vertebrate development and their ligand-type activities overlap substantially with those of canonical Wnt ligands. A characteristic feature of all four RSPO members is their ability to activate β-catenin signaling and enhance WNT-mediated β-catenin activation. It has recently been described that recurrent gene fusions involving RSPO family members RSPO2 and RSPO3 occur in ∼10% of colon tumors. In this study we developed a TaqMan qRT-PCR-based approach to evaluate the expression of these three (3) RSPO fusion transcripts in formalin-fixed paraffin embedded tissue (FFPET) samples. We examined 324 lung cancer, 81 colorectal cancer, 71 head & neck, 11 esophageal, 92 ovarian cancer, and 103 breast cancer FFPET samples for the presence of EIF3E(e1)-RSPO2(e1), PTPRK(e1)-RSPO3(e2), and PTPRK(e7)-RSPO3(e2). EIF3E(e1)-RSPO2(e1), a fusion which is expected to produce a functional RSPO2 protein driven by the EIF3E promoter, was identified in ∼1-2% of most of cancer types with the exception of breast cancer. The PTPRK(e1)-RSPO3(e2) fusion was expressed by ∼1-11% of the samples in the different cancers, making it the most prevalent of the fusions. PTPRK(e1)-RSPO3(e2) fusion is an in-frame fusion that preserves the entire coding sequence of RSPO3 and replaces its secretion signal sequence with that of PTPRK. The PTPRK(e7)-RSPO3(e2) fusion is also an in-frame fusion in which the RSPO3 native signal peptide is replaced by the secretion signal of PTPRK. The PTPRK(e7)-RSPO3(e2) was the least prevalent of all the fusions, positive samples were found exclusively in the head and neck (∼2%) and breast cancer samples (∼2%). All of the fusions detected were mutually exclusive. The RSPO gene fusions identified may provide new potential opportunities for therapeutic intervention. Citation Format: Gabriela Martinez Cardona, Katherine Bell, Joseph Portale, Dana Gaffney, Christopher Moy, Suso Platero, Matthew V. Lorenzi, Jayaprakash Karkera. Identification of R-Spondin fusions in various types of human cancer. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 2408. doi:10.1158/1538-7445.AM2014-2408

<p>Table S1. Frequencies of gene locus amplifications across tumor types; Table S2. Effect of FGFR inhibitors on growth of RK3E expressing FGFR2 and FGFR3 fusion constructs and RT-4 bladder cancer cell line; Figure S1. Chemical structure of JNJ-42756493; Figure S2. Western Blot confirming the overexpression of HA-tagged FGFR2 fusion genes</p>

<p>Table S1. Frequencies of gene locus amplifications across tumor types; Table S2. Effect of FGFR inhibitors on growth of RK3E expressing FGFR2 and FGFR3 fusion constructs and RT-4 bladder cancer cell line; Figure S1. Chemical structure of JNJ-42756493; Figure S2. Western Blot confirming the overexpression of HA-tagged FGFR2 fusion genes</p>

Fibroblast growth factors (FGFs) are a family of homologous secreted glycoproteins involved in signaling pathways responsible for embryonic development, cell proliferation, survival, and migration. FGF activity is mediated by four transmembrane fibroblast growth factor receptors (FGFRs) which are receptor tyrosine kinases. Typically, FGF binding induces FGFR dimerization, leading to phosphorylation of the intracellular tyrosine kinase domain. This leads to downstream activation of multiple signaling pathways, including the mitogen-activated protein kinase (MAPK), PI3K/AKT, signal transducer and activator of transcription (STAT), and phospholipase-C-γ cascades. Deregulated FGFR activity, through mutations or translocations, is often associated with oncogenic events. Aberrations in FGFR genes have been observed in several tumor types including bladder, gastric, colorectal, ovarian, and hematologic cancers. To date, several FGFR3 mutations have been identified in bladder cancer. In this study, we developed a TaqMan qRT-PCR-based approach to detect four FGFR3 mutations in formalin-fixed paraffin embedded tissue (FFPET) samples. Cell lines overexpressing FGFR3 mutations were generated to determine impact on cell signaling, and sensitivity to the small-molecule pan-FGFR inhibitor JNJ-42756493. To determine the role and significance of these FGFR3 mutations in cancer, mutation expression constructs were designed and individually transfected into normal rat kidney epithelial cells. Cells harboring the FGFR3 mutations exhibited anchorage-independent growth, increased proliferation, and showed increased sensitivity to the FGFR inhibitor JNJ-42756493 in vitro compared to parental lines. These findings underline the oncogenic potential of the FGFR3 mutation genes and highlight their unique potential as predictive biomarkers in the selection of patients for FGFR-targeted therapy. Citation Format: Gabriela Martinez Cardona, Dana Gaffney, Katherine Bell, Joseph Portale, Matthew Dunworth, Matthew Lorenzi, Suso Platero, Jayaprakash Karkera. FGFR3 mutations as novel oncogenic targets. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 3990.

Fusion genes are chromosomal aberrations that are found in many cancers and can be used as prognostic markers and drug targets in clinical practice. Gene fusions can lead to the production of oncogenic fusion proteins or to enhanced expression of oncogenes. Advances in next-generation sequencing technologies have made possible to identify more efficiently novel fusion proteins in cancer. Recently, several FGFR fusion genes with intact kinase domains have been identified in bladder, lung, breast, thyroid, oral, and prostate cancers, as well as other tumor types. To date, several FGFR3 partner genes have been identified. In this study, we focused on the FGFR3-BAIAP2L1 and FGFR3-TACC3 gene fusions and investigated their tumorigenic activity, mechanism of activation, and sensitivity to the FGFR inhibitor JNJ-42756493. To determine the role and significance of FGFR fusion genes in cancer, FGFR fusion expression constructs were designed and individually transfected into normal rat kidney epithelial cells. FGFR fusion overexpressing cells not only showed increased cell proliferation, but also exhibited anchorage-independent cell growth. Cells harboring the FGFR fusions showed increased sensitivity to the FGFR inhibitor JNJ-42756493 in vitro, whereas the wild-type FGFR3 did not in the absence of FGF ligands. In addition, Western blotting analyses indicated that the overexpression of the FGFR fusions resulted in highly activated proteins that induce signaling via the MAPK pathway. These findings underline the oncogenic potential of the FGFR fusion genes and highlight their unique potential as predictive biomarkers in the selection of patients for FGFR-targeted therapy. Citation Format: Gabriela Martinez Cardona, Katherine Bell, Dana Gaffney, Joseph Portale, Suso Platero, Matthew Lorenzi, Jayaprakash Karkera. The role of FGFR fusion genes as novel oncogenic targets. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 4325. doi:10.1158/1538-7445.AM2015-4325