👤 William R Doerfler

Approximately 10-20% of thyroid cancers are driven by gene fusions, which activate oncogenic signaling through aberrant overexpression, ligand-independent dimerization or loss of inhibitory motifs. We identified 13 thyroid tumors with thyroglobulin (TG) gene fusions and aimed to assess their histopathology and the fusions' oncogenic and tumorigenic properties. Of eleven cases with surgical pathology, 82% were carcinomas and 18% were noninvasive follicular thyroid neoplasms with papillary-like nuclear features (NIFTP). TG fusions preserved exon(s) 1, 1-15, 1-35 or most frequently, 1-47 of TG and, based on the 3' partner were grouped as i) involving receptor tyrosine kinases (RTKs) (TG::FGFR1, TG::RET, TG::ALK and TG::NTRK1), ii) driving aberrant DPRX and chromosome 19 microRNA cluster expression (TG::DPRX) or iii) involving IGF2 mRNA-binding protein (TG::IGF2BP1). All 13 fusion-positive tumors exhibited strong (8.5 ± 3.3 log2-fold) 3' partner overexpression driven by the TG promoter. Gene expression analysis revealed TG::RET- and TG::ALK-positive tumors being BRAFV600E-like and remaining tumors RAS-like. In thyroid PCCL3 cells, the TG::NTRK1 fusion demonstrated both spontaneous and ligand-associated dimerization, activated downstream MAPK, AKT and STAT3 signaling and drove xenograft tumorigenesis in nude mice. FDA-approved NTRK inhibitors entrectinib and larotrectinib effectively blocked TG::NTRK1 signaling in vitro and inhibited xenograft tumor growth in vivo. In summary, we report a spectrum of TG gene fusions as recurrent oncogenic events in thyroid cancer and NIFTP that drive strong overexpression of partner genes, frequently RTKs. The TG::NTRK1 fusion is prone to dimerization, activates oncogenic signaling, drives tumorigenesis in thyroid cells and, like other fusions involving RTKs, represents a potential therapeutic target in thyroid cancer. Show less

Adamantinomatous craniopharyngiomas (ACP) as benign sellar brain tumors are challenging to treat. In order to develop robust in vivo drug testing methodology, the murine orthotopic craniopharyngioma model (PDX) was characterized by magnetic resonance imaging (MRI) and histology in xenografts from three patients (ACP1-3). In ACP PDX, multiparametric MRI was conducted to assess morphologic characteristics such as contrast-enhancing tumor volume (CETV) as well as functional parameters from dynamic contrast-enhanced MRI (DCE-MRI) and diffusion-weighted imaging (DWI) including area-under-the-curve (AUC), peak enhancement (PE), time-to-peak (TTP) and apparent diffusion coefficient (ADC). These MRI parameters evaluated in 27 ACP PDX were correlated to histological features and percentage of vital tumor cell content. Qualitative analysis of MRI and histology from PDX revealed a similar phenotype as seen in patients, although the MRI appearance in mice resulted in a more solid tumor growth than in humans. CETV were significantly higher in ACP2 xenografts relative to ACP1 and ACP3 which correspond to respective average vitality of 41%, <10% and 26% determined histologically. Importantly, CETV prove tumor growth of ACP2 PDX as it significantly increases in longitudinal follow-up of 110 days. Furthermore, xenografts from ACP2 revealed a significantly higher AUC, PE and TTP in comparison to ACP3, and significantly increased ADC relative to ACP1 and ACP3 respectively. Overall, DCE-MRI and DWI can be used to distinguish vital from non-vital grafts, when using a cut off value of 15% for vital tumor cell content. MRI enables the assessment of craniopharyngioma PDX vitality in vivo as validated histologically. Show less