The neurotrophic tyrosine receptor kinase (

Brooke-Spiegler syndrome (BSS; a.k.a. tuban tumor syndrome) is an autosomal dominant inherited skin disorder caused by germline mutations in the CYLD tumor suppressor gene. BSS is characterized by multiple skin adnexal tumors, mainly cylindromas and spiradenomas on the head and neck. The tumors are often severely disfiguring and require repeated surgical interventions. Here, we describe a four-generation BSS-family with a novel germline c.1613_1614delGC CYLD mutation that introduces a premature STOP codon predicted to result in a truncated, inactivated CYLD protein. In addition, we present a pilot study describing establishment of the first patient-derived xenografts (PDXs) from cutaneous CYLD-defective cylindromas. Fresh tumor tissues from cylindromas were transplanted into immunocompromised mice to generate PDXs. One xenograft showed progressive tumor growth after 3 months whereas the others remained unchanged in size during the 6 months study period. Histopathological and immunohistochemical analyses of the PDXs revealed that they recapitulate the histological and molecular features of their respective primary tumors, including expression of NTRK3 and the oncogenic driver MYB. In summary, we present the first preclinical BSS-model that morphologically and genetically recapitulates human CYLD-defective cylindromas. This model will be useful for preclinical therapeutic drug testing and for further studies of the molecular pathogenesis of inherited cylindromas.

Gastric cancer (GC) is the most common gastrointestinal malignancy in the digestive system. Recent studies have proven that long non-coding RNAs (lncRNAs) are closely related to tumor growth and metastasis. The study aimed to explore the effect of LINC00978 on GC cells proliferation and tumorigenesis. LINC00978 was up-regulated in GC tissues and cell lines. Up-regulation of LINC00978 was positively correlated with low survival rate. LINC00978 silence inhibited proliferation, metastasis, and promoted apoptosis in BGC-823 cells. Additionally, LINC00978 functioned as competing endogenous RNA to inhibit miR-497 expression. Further, NTRK3 was confirmed as a target gene of miR-497. Up-regulation of NTRK3 was found in GC tissues, and the positive correlation was presented between LINC00978 and NTRK3. Further, LINC00978 promoted cell proliferation and tumor weight by regulation of NTRK3. These findings demonstrated that LINC00978 promoted cell proliferation and tumorigenesis by regulating miR-497/NTRK3 axis in GC.

NTRK gene fusions involving either NTRK1, NTRK2 or NTRK3 (encoding the neurotrophin receptors TRKA, TRKB and TRKC, respectively) are oncogenic drivers of various adult and paediatric tumour types. These fusions can be detected in the clinic using a variety of methods, including tumour DNA and RNA sequencing and plasma cell-free DNA profiling. The treatment of patients with NTRK fusion-positive cancers with a first-generation TRK inhibitor, such as larotrectinib or entrectinib, is associated with high response rates (>75%), regardless of tumour histology. First-generation TRK inhibitors are well tolerated by most patients, with toxicity profiles characterized by occasional off-tumour, on-target adverse events (attributable to TRK inhibition in non-malignant tissues). Despite durable disease control in many patients, advanced-stage NTRK fusion-positive cancers eventually become refractory to TRK inhibition; resistance can be mediated by the acquisition of NTRK kinase domain mutations. Fortunately, certain resistance mutations can be overcome by second-generation TRK inhibitors, including LOXO-195 and TPX-0005 that are being explored in clinical trials. In this Review, we discuss the biology of NTRK fusions, strategies to target these drivers in the treatment-naive and acquired-resistance disease settings, and the unique safety profile of TRK inhibitors.

Perineural invasion (PNI) potentially increases the risk of relapse and abdominal pain in patients with pancreatic ductal adenocarcinoma (PDAC). However, the underlying mechanisms of PNI of PDAC is incompletely revealed. Our study aimed to investigate roles of miR-429 in modulating PNI in PDAC. We found that miR-429 was downregulated in PDAC cancer tissues and was profoundly decreased in tissues with PNI. It was reduced in nine of the ten examined pancreatic cancer cell lines. MiR-429 mimics restored its cellular expressions in MIA PaCa-2 and BxCP3 cells and significantly suppressed cell viability and invasion of the cancer cells. The online bioinformatic software predicted that neurotrophin-3 (NT-3) was a potential target gene of miR-429. It was showed that NT-3 mRNA elevated in PC cancer tissues, especially in patients presenting PNI. MiR-429 upregulation substantially suppressed the NT-3 mRNA and secretion in cancer cells. Also, the dual luciferase reporter assays confirmed the interaction between miR-429 and NT-3. When co-culturing the two PDAC cells with PC-12 cells, the invaded cell counts significantly increased comparing with the sole culture of cancer cells. However, miR-429 mimic transfection or NT-3 blocking retarded the cancer invasion in the co-culture system. Besides, we found that cancer cells conditioned medium (CM) treatment significantly increased the neurite outgrowth percentage in PC-12 cells, which was suppressed by culturing with CM from miR-429 mimics-transfected cells. In the CM cultured PC-12 cells, NT-3 receptor TrkC as well as pain-related proteins TRPV1 and TRPV2 significantly elevated. Collectively, miR-429 potentially suppressed neurotrophin-3 to alleviate PNI of PDAC.

Cutaneous spindle-cell neoplasms in adults as well as children represent a frequent dilemma for pathologists. Along this neoplasm spectrum, the differential diagnosis with CD34-positive proliferations can be challenging, particularly concerning neoplasms of fibrohistiocytic and fibroblastic lineages. In children, cutaneous and superficial soft-tissue neoplasms with CD34-positive spindle cells are associated with benign to intermediate malignancy potential and include lipofibromatosis, plaque-like CD34-positive dermal fibroma, fibroblastic connective tissue nevus, and congenital dermatofibrosarcoma protuberans. Molecular biology has been valuable in showing dermatofibrosarcoma protuberans and infantile fibrosarcoma that are characterized by COL1A1-PDGFB and ETV6-NTRK3 rearrangements respectively. We report a case of congenital CD34-positive dermohypodermal spindle-cell neoplasm occurring in a female infant and harboring a novel KHDRBS1-NTRK3 fusion. This tumor could belong to a new subgroup of pediatric cutaneous spindle-cell neoplasms, be an atypical presentation of a plaque-like CD34-positive dermal fibroma, of a fibroblastic connective tissue nevus, or represent a dermatofibrosarcoma protuberans with an alternative gene rearrangement.

BACKGROUND: Arsenic trioxide (As
METHODS: The aim of the present study was to investigate the effect of As
RESULTS: Immunohistochemical and real-time PCR analyses indicated that TrkA and TrkC were over-expressed in NB, and specifically during stages 1, 2 and 4S of the disease progression. TrkB expression was increased in stage 3 and 4 NB. As
CONCLUSION: The present findings suggested that As

The neurotrophin-3 (NT-3) receptor tropomyosin receptor kinase C (TrkC/NTRK3) has been described as a dependence receptor and, as such, triggers apoptosis in the absence of its ligand NT-3. This proapoptotic activity has been proposed to confer a tumor suppressor activity to this classic tyrosine kinase receptor (RTK). By investigating interacting partners that might facilitate TrkC-induced cell death, we have identified the basic helix-loop-helix (bHLH) transcription factor Hey1 and importin-α3 (karyopherin alpha 4 [KPNA4]) as direct interactors of TrkC intracellular domain, and we show that Hey1 is required for TrkC-induced apoptosis. We propose here that the cleaved proapoptotic portion of TrkC intracellular domain (called TrkC killer-fragment [TrkC-KF]) is translocated to the nucleus by importins and interacts there with Hey1. We also demonstrate that Hey1 and TrkC-KF transcriptionally silence mouse double minute 2 homolog (MDM2), thus contributing to p53 stabilization. p53 transcriptionally regulates the expression of TrkC-KF cytoplasmic and mitochondrial interactors cofactor of breast cancer 1 (COBRA1) and B cell lymphoma 2-associated X (BAX), which will subsequently trigger the intrinsic pathway of apoptosis. Of interest, TrkC was proposed to constrain tumor progression in neuroblastoma (NB), and we demonstrate in an avian model that TrkC tumor suppressor activity requires Hey1 and p53.

Activating neurotrophic receptor kinase (NTRK) fusions define certain pediatric mesenchymal tumors, including infantile fibrosarcoma and cellular mesoblastic nephroma. Traditionally, molecular confirmation of these fusions has included either fluorescent in situ hybridization for ETV6 rearrangements or reverse-transcriptase polymerase chain reaction for the classic ETV6-NTRK3 fusion. However, these methods overlook variant NTRK rearrangements, which are increasingly appreciated as recurrent events in a subset of pediatric mesenchymal tumors. New therapeutic agents successfully target these fusions and may prevent morbid surgeries in very young children, making recognition of tumors harboring NTRK rearrangements of increasing importance. We evaluated the performance of immunohistochemical (IHC) staining using pan-Trk and TrkA antibodies in 79 pediatric mesenchymal tumors. Negative controls included pediatric mesenchymal tumors not harboring (n=28) or not expected to harbor (n=22) NTRK fusions. NTRK rearrangements were detected predominantly by DNA-based next-generation sequencing assays, specifically UW OncoPlex and UCSF500 Cancer Gene Panel. Pan-Trk IHC (EPR17341) was 97% sensitive and 98% specific for the presence of an NTRK rearrangement, and TrkA IHC (EP1058Y) was 100% sensitive and 63% specific for the presence of an NTRK rearrangement. Tumors with NTRK1 or NTRK2 rearrangements showed cytoplasmic staining, whereas tumors with NTRK3 rearrangements showed nuclear +/- cytoplasmic staining. We conclude that pan-Trk IHC is a highly sensitive and specific marker for NTRK rearrangements in pediatric mesenchymal tumors.

Tropomyosin receptor kinase (Trk) inhibitors have shown high response rates in patients with tumors harboring NTRK fusions. We identified 4 NTRK fusion-positive uterine sarcomas that should be distinguished from leiomyosarcoma and undifferentiated uterine sarcoma. NTRK rearrangements were detected by fluorescence in situ hybridization (FISH) and/or targeted RNA or DNA sequencing in 4 undifferentiated uterine sarcomas with spindle cell morphology. Because of histologic overlap with leiomyosarcoma, TrkA and pan-Trk immunohistochemistry was performed in 97 uterine leiomyosarcomas. NTRK1 and NTRK3 FISH was performed on tumors with TrkA or pan-Trk staining. We also performed whole transcriptome RNA sequencing of a leiomyosarcoma with TrkA expression and targeted RNA sequencing of 2 additional undifferentiated uterine sarcomas. FISH and/or targeted RNA or DNA sequencing in the study group showed TPM3-NTRK1, LMNA-NTRK1, RBPMS-NTRK3, and TPR-NTRK1 fusions. All tumors were composed of fascicles of spindle cells. Mitotic index was 7 to 30 mitotic figures per 10 high power fields; tumor necrosis was seen in 2 tumors. Desmin, estrogen receptor, and progesterone receptor were negative in all tumors, while pan-Trk was expressed in all tumors with concurrent TrkA staining in 3 of them. TrkA and/or pan-Trk staining was also seen in 6 leiomyosarcomas, but these tumors lacked NTRK fusions or alternative isoforms by FISH or whole transcriptome sequencing. No fusions were detected in 2 undifferentiated uterine sarcomas. NTRK fusion-positive uterine spindle cell sarcomas constitute a novel tumor type with features of fibrosarcoma; patients with these tumors may benefit from Trk inhibition. TrkA and pan-Trk expression in leiomyosarcomas is rare and does not correlate with NTRK rearrangement.

Perivascular epithelioid cell tumor (PEComa) is an uncommon tumor which presents with epithelioid and spindled cell morphology and is immunoreactive for myogenic and melanocytic markers. Recently, a subset of PEComas has been reported to harbor

Activation of tropomyosin receptor kinase (TRK) family tyrosine kinases by chromosomal rearrangement has been shown to drive a wide range of solid tumors and hematologic malignancies. TRK fusions are actionable targets as evidenced by recent clinical trial results in solid tumors. Entrectinib (RXDX-101) is an investigational, orally available, CNS-active, highly potent, and selective kinase inhibitor against TRKA/B/C, ROS1, and ALK kinase activities. Here, we demonstrate that TRK kinase inhibition by entrectinib selectively targets preclinical models of TRK fusion-driven hematologic malignancies. In acute myelogenous leukemia (AML) cell lines with endogenous expression of the

Despite advances in genomic analysis, the molecular origin of neuroendocrine tumors (NETs) is complex and poorly explained by described oncogenes. The neurotrophic TRK family, including

Neonatal intussusception of the intestinal tract is rare. However, most neonatal intussusceptions have an organic lead point. For the lead point to be a neoplasm is extremely rare. We report a case that presented with neonatal intussusception with a congenital infantile fibrosarcoma as the lead point. The detection of ETV6-NTRK3 gene fusion was useful, although the definitive diagnosis was achieved by a comprehensive evaluation including this gene analysis, standard histology and immunohistochemistry. Neonatal intussusception should be suspected to be caused by a neoplasm. If pathological diagnosis is difficult, molecular analysis should be utilized to diagnose congenital infantile fibrosarcoma.

Neurotrophic tyrosine kinase genes encode for the Trk-family proteins TrkA, TrkB, and TrkC, which have an important role in the development of the nervous system; however, they have been identified as oncogenic fusions in solid tumors (NTK-1, NTRK-2, and NTRK-3) and are associated with poor survival in lung cancer. These three new fusions can be detected by fluorescent in situ hybridization or next-generation sequencing in less than 5% of the lung tumors. There are several ongoing clinical trials of NTRK oncogenes in lung cancer and other tumors. The agents entrectinib (RXDX-101), a multi-kinase small molecule inhibitor that selectively inhibits NTRK1, NTRK2, and NTRK3, ROS1 and ALK, and LOXO-101, an ATP-competitive pan-NTRK inhibitor, have shown responses in patients with lung cancer with an acceptable toxicity profile. Although these oncogenic fusions are not very prevalent, the high prevalence of lung cancer makes these findings very relevant and suggests the feasibility of these oncogenes as targets in lung cancer. New data from Ozono and collaborators presented in this issue suggest that BDNF/TrkB signal promotes proliferating migratory and invasive phenotypes and cellular plasticity in squamous cell carcinoma (SCC) of the lung but that it also represents a druggable target that may bring hope to squamous lung cancer patients.

OBJECTIVE: PTC-specific analysis identified novel fusions involving
DESIGN AND METHODS: The prevalence of the fusions was determined by RT-PCR in 71 classical PTC, 45 follicular variants of PTC (FVPTC), 19 follicular thyroid adenomas (FTAs) and 22 follicular thyroid carcinomas (FTCs).

In the last few years, exciting reports have emerged regarding the role of the two types of neurotrophin receptors, p75

Infantile fibrosarcomas (IFS) represent a distinct group of soft tissue tumors occurring in patients under 2 years of age and most commonly involving the extremities. Most IFS show recurrent ETV6-NTRK3 gene fusions, sensitivity to chemotherapy, and an overall favorable clinical outcome. However, outside these well-defined pathologic features, no studies have investigated IFS lacking ETV6-NTRK3 fusions, or tumors with the morphology resembling IFS in older children. This study was triggered by the identification of a novel SEPT7-BRAF fusion in an unclassified retroperitoneal spindle cell sarcoma in a 16-year-old female by targeted RNA sequencing. Fluorescence in situ hybridization screening of 9 additional tumors with similar phenotype and lacking ETV6-NTRK3 identified 4 additional cases with BRAF gene rearrangements in the pelvic cavity (n=2), paraspinal region (n=1), and thigh (n=1) of young children (0 to 3 y old). Histologically, 4 cases including the index case shared a fascicular growth of packed monomorphic spindle cells, with uniform nuclei and fine chromatin, and a dilated branching vasculature; while the remaining case was composed of compact cellular sheets of short spindle to ovoid cells. In addition, a minor small blue round cell component was present in 1 case. Mitotic activity ranged from 1 to 9/10 high power fields. Immunohistochemical stains were nonspecific, with only focal smooth muscle actin staining demonstrated in 3 cases tested. Of the remaining 5 BRAF negative cases, further RNA sequencing identified 1 case with EML4-NTRK3 in an 1-year-old boy with a foot IFS, and a second case with TPM3-NTRK1 fusion in a 7-week-old infant with a retroperitoneal lesion. Our findings of recurrent BRAF gene rearrangements in tumors showing morphologic overlap with IFS expand the genetic spectrum of fusion-positive spindle cell sarcomas, to include unusual presentations, such as older children and adolescents and predilection for axial location, thereby opening new opportunities for kinase-targeted therapeutic intervention.

Platinum resistance is a critical barrier for clinicians to improve the survival of ovarian cancer. Our study evaluated the correlation between copy number variations (CNVs) of neurotrophic tyrosine receptor kinase 3 (NTRK3) and the prognosis of ovarian cancer, which might predict platinum resistance in ovarian cancer patients.Array comparative genomic hybridization (CGH) was used to test gene backgrounds between platinum-sensitive and platinum-resistant relapsed populations and CNVs of NTRK3 were indicated by cluster analysis. Fluorescence in situ hybridization (FISH) was adopted in 41 cases for further verification, which confirmed the results of array CGH. Spearman's rank correlation analysis and χ test were used to evaluate the accuracy of CNVs of NTRK3 which predicted platinum-sensitive or platinum-resistant recurrence.We detected CNVs of NTRK3 between 2 groups by array CGH, and amplification of NTRK3 was confirmed by FISH in the platinum-sensitive recurrence group with enlarged samples. The test concordance of 2 methods was 78.6%. Among 41 cases with satisfied FISH results, the median time to recurrence (TTR) of patients with amplified and nonamplified NTRK3 were respectively 18 and 5 months (P <.01). The cut-off value of TTR to differentiate platinum-sensitive or platinum-resistant recurrence was 6 months in accordance with clinical practice. According to the above standard, 15 cases with NTRK3 amplification were platinum-sensitive and 12 cases without NTRK3 amplification were platinum-resistant recurrences which demonstrated that the accuracy of NTRK3 amplification/nonamplification to predict recurrent types was 65.9% (27/41).CNVs of NTRK3 were associated with platinum-sensitive and platinum-resistant recurrences. Amplification of NTRK3 perfectly predicted platinum-sensitive relapse of ovarian cancer.

Neurotrophins are a family of growth factors that are vital to the proper development of the central nervous system. Their effects on cells are governed by the expression and activation of the tyrosine kinase receptors TrkA, TrkB and TrkC. TrkB has been immensely implicated in mediating neuronal migration, development and differentiation. It has also been shown to protect several neuronal cell types from an array of cytotoxic stressors after activation by its conjugate ligand brain-derived neurotrophic factor (BDNF). Over the past two decades, it has been shown that TrkB and BDNF are up-regulated in many types of cancers, conferring aggressive phenotypes underpinned by their resistance to several standard chemotherapeutic agents. This resistance to chemotherapy is modulated by the downstream targets of the TrkB receptor which include the well-characterized PI3K /Akt growth pathway, a hallmark of uncontrolled cancer cell growth and proliferation. Pre-clinical efforts to develop inhibitors of this receptor are promising, and such inhibitors also seem to sensitize cancer cells to standard chemotherapies. However, new evidence suggests that BDNF overexpression in the hypothalamus has immunoaugmenting properties, eliciting an increased anti-tumor immune response and reducing the activity of several proteins that would normally confer resistance to chemotherapeutic agents. In the current work, we provide a global analysis of the physiological consequences of TrkB receptor activation in vitro and discuss the dynamic consequences of TrkB activation in vivo. Finally, we propose a clinically-feasible option for increasing BDNF expression in the hypothalamus to more readily utilize the oncolytic effects of BDNF.

Low-grade sinonasal adenocarcinomas (low-grade SNACs) of the sinonasal tract comprise a poorly characterized and histologically heterogeneous group of tumors. We describe three cases of a histologically distinct variant of low-grade SNAC characterized by ETV6 gene rearrangements. The patients included 2 women (aged 32 and 88 y) and a man (aged 75 y); all were initially treated with surgery alone. Follow-up ranged from 9 to 170 months with one patient having 2 local recurrences and none experiencing distant or regional metastases. Tumors were composed of cytologically bland columnar and cuboidal eosinophilic tumor cells with basally located nuclei arranged in tubular and tubulotrabecular patterns. Immunohistochemically, CK7, DOG1, GCDFP-15, and SOX10 were positive in all cases, and vimentin was positive in 2 cases. Scattered single cells or small groups of tumor cells were S-100 positive. Only one case had weak, focal expression of GATA3, and mammaglobin was consistently negative. Two cases had ETV6-NTRK3 gene fusions, whereas ETV6 had an unknown fusion partner gene in one case. The highly similar morphology, immunohistochemical profile, and genetics of the presented cases are suggestive of a specific disease. Although translocation-associated adenocarcinomas in the sinonasal tract have previously been described exclusively as salivary-type carcinomas, we present the first type of carcinoma characterized by recurrent genetic rearrangements and distinct phenotype occurring exclusively in the sinonasal tract with no known major salivary gland counterpart. We provisionally designate this tumor ETV6-rearranged low-grade SNAC. Identification of additional cases is necessary to fully appreciate the morphologic and biological spectrum of this disease.

Activating neurotrophic tyrosine receptor kinase (NTRK) fusions, typically detected using nucleic-acid based assays, are highly targetable and define certain tumors. Here, we explore the utility of pan-TRK immunohistochemistry (IHC) to detect NTRK fusions. NTRK rearrangements were detected prospectively using MSK-IMPACT, a DNA-based next-generation sequencing assay. Transcription of novel NTRK rearrangements into potentially functional fusion transcripts was assessed via Archer Dx fusion assay. Pan-Trk IHC testing with mAb EPR17341 was performed on all NTRK rearranged cases and 20 cases negative for NTRK fusions on Archer. Of 23 cases with NTRK rearrangements, 15 had known activating fusions. Archer detected fusion transcripts in 6 of 8 novel NTRK rearrangements of uncertain functional significance. Pan-Trk IHC was positive in 20 of 21 cases with NTRK fusion transcripts confirmed by Archer. The discordant negative case was a mismatch repair- deficient colorectal carcinoma with an ETV6-NTRK3 fusion. All 20 additional Archer-negative cases had concordant pan-TRK IHC results. Pan-Trk IHC sensitivity and specificity for transcribed NTRK fusions was 95.2% and 100%, respectively. All positive IHC cases had cytoplasmic staining while the following fusion partner-specific patterns were discovered: all 5 LMNA-NTRK1 fusions displayed nuclear membrane accentuation, all 4 TPM3/4 fusions displayed cellular membrane accentuation, and half (3/6) of ETV6-NTRK3 fusions displayed nuclear staining. Pan-Trk IHC is a time-efficient and tissue-efficient screen for NTRK fusions, particularly in driver-negative advanced malignancies and potential cases of secretory carcinoma and congenital fibrosarcoma. Pan-Trk IHC can help determine whether translation occurs for novel NTRK rearrangements.

PURPOSE: High messenger RNA (mRNA) expression of the tropomyosin receptor kinase C gene (TrkC) has been associated with favorable survival in medulloblastoma patients. Untested is whether it plays a role through modulating the response to therapy or whether it might be a surrogate marker for a favorable molecular subgroup.
METHODS: The medulloblastoma-derived cell line DAOY was stably transfected to overexpress TrkC (clone DAOY-TrkC) and compared to a control (clone DAOY-EV, empty vector transfected). Cell viability (MTS assay) was tested after irradiation or incubation with chemotherapeutic drugs. Neuroradiologic response to postoperative chemotherapy or craniospinal irradiation (CSI) of medulloblastoma patients aged 3-21 years with postoperative residual disease treated within the consecutive trials HIT'91/HIT2000 was compared to TrkC mRNA expression in their tumor samples. Five well-characterized independent expression-profiling studies covering together 686 medulloblastoma patients were analyzed for TrkC levels according to the molecular subgroups.
RESULTS: Cell viability of DAOY-TrkC compared to DAOY-EV was not different after exposure to increasing doses of irradiation, cisplatin, etoposide, or vincristine. While TrkC mRNA expression tended to be higher in non-responders (n = 5/19) to postoperative CSI (p = 0.03, ratio 15.5, 95% CI 9-267), this was the case in responders (n = 23/43) to chemotherapy (p = 0.04, ratio 6.1, 95% CI 1.1-35), both analyzed with Mann-Whitney U test (not significant after Bonferroni adjustment). The highest TrkC mRNA levels were found in the SHH subgroup across all expression-profiling studies.
CONCLUSIONS: High TrkC mRNA expression appears to be frequent in the SHH subgroup and seems not to have a major effect on therapy responsiveness in medulloblastoma patients.

Pediatric fibroblastic/myofibroblastic lesions are a relatively common group of tumors with varying morphologies, for which the molecular mechanisms are becoming increasingly well characterized. Congenital infantile fibrosarcoma (CIFS), perhaps the most well studied of these lesions is characterized by a recurrent ETV6-NTRK3 gene fusion. However, a notable subset of locally aggressive congenital/infantile soft tissue lesions with similar morphologic features to CIFS, have not to-date, shown evidence of any canonical molecular aberration. We describe 6 patients with mesenchymal tumors composed of infiltrative fibroblastic/myofibroblastic tumor cells and showing a morphologic spectrum of features much analogous to that previously described in CIFS but without ETV6 fusion transcripts. These tumors lacked a uniform immunoprofile, but showed variable expression of CD34, S100, smooth muscle actin, and CD30. All patients first developed a mass in infancy (≤2 months of age). Using next-generation DNA sequencing, TMP3-NTRK1 fusions were identified in 4 cases, an LMNA-NTRK1 fusion in one case, and a variant EML4-NTRK3 fusion in one case. Similar to infantile fibrosarcoma, these tumors were locally aggressive (with local recurrences if incompletely excised) and rarely metastasized (lung metastases in one patient). Proper identification of these tumors including investigation for NTRK family gene rearrangements is essential for diagnostic accuracy, as well as for clinical management decisions. Given the morbidity associated with radical resection of large soft tissue tumors, children with unresectable, recurrent, and/or metastatic disease may benefit from treatment with NTRK targeted therapies.

Acquired epidermal growth factor receptor (EGFR) resistance mutations to osimertinib are common, including the EGFR C797S that abolishes the covalent binding of osimertinib to EGFR. Here we report the emergence of novel EGFR solvent front mutations at Gly796 (G796S/R) in addition to a hinge pocket L792F/H mutations, and C797S/G all in cis with T790M in a single patient on progression on osimertinib as detected by plasma circulating tumor DNA (ctDNA) assay in the course of clinical care. A 69-year-old Caucasian female former light-smoker presented with stage IV EGFR L858R positive adenocarcinoma who developed EGFR T790M mutation after 8 month treatment of erlotinib. The patient was initiated on osimertinib with disease shrinkage after 2 months, but tumor regrowth was observed after 5 months of osimertinib treatment. Assay of plasma ctDNA at this time revealed these different secondary resistance mutations all in trans with each other including distinct mutations at the same codon producing different amino acid changes: G796S/R (mutant allele frequency [MAF]; 14.4%), C797S/G (MAF: 2.26%), L792F/H (MAF: 0.36%), and V802F (MAF: 0.40%), in addition to the pre-existing L858R (MAF:17.9%) and T790M (MAF:18.2%) but all in cis with T790M. The G796S/R mutations are homologous with known reported solvent front mutations in ALK G1202R, ROS1 G2032R, TrkA G595R and TrkC G623R, all of which are associated with acquired resistance to type I TKIs. In silico modeling revealed mutation at G796 interferes with osimertinib binding to the EGFR kinase domain at the phenyl aromatic ring position as this residue forms a narrow "hydrophobic sandwich" with L718, while L792F/H mutation interferes with osimertinib binding at the methoxyl group on the phenyl ring. Multiple resistance mutations at differing allele frequencies including novel EGFR solvent front mutations can emerge in a single patient with progression on osimertinib potentially due to tumor hetereogeneity and definitely present a significant therapeutic and drug development challenge.

Deficient mismatch repair (MMR) and microsatellite instability (MSI) contribute to ~15% of colorectal cancer (CRCs). We hypothesized MSI leads to mutations in DNA repair proteins including BRCA2 and cancer drivers including EGFR. We analyzed mutations among a discovery cohort of 26 MSI-High (MSI-H) and 558 non-MSI-H CRCs profiled at Caris Life Sciences. Caris-profiled MSI-H CRCs had high mutation rates (50% vs 14% in non-MSI-H, P < 0.0001) in BRCA2. Of 1104 profiled CRCs from a second cohort (COSMIC), MSH2/MLH1-mutant CRCs showed higher mutation rates in BRCA2 compared to non-MSH2/MLH1-mutant tumors (38% vs 6%, P < 0.0000001). BRCA2 mutations in MSH2/MLH1-mutant CRCs included 75 unique mutations not known to occur in breast or pancreatic cancer per COSMIC v73. Only 5 deleterious BRCA2 mutations in CRC were previously reported in the BIC database as germ-line mutations in breast cancer. Some BRCA2 mutations were predicted to disrupt interactions with partner proteins DSS1 and RAD51. Some CRCs harbored multiple BRCA2 mutations. EGFR was mutated in 45.5% of MSH2/MLH1-mutant and 6.5% of non-MSH2/MLH1-mutant tumors (P < 0.0000001). Approximately 15% of EGFR mutations found may be actionable through TKI therapy, including N700D, G719D, T725M, T790M, and E884K. NTRK gene mutations were identified in MSH2/MLH1-mutant CRC including NTRK1 I699V, NTRK2 P716S, and NTRK3 R745L. Our findings have clinical relevance regarding therapeutic targeting of BRCA2 vulnerabilities, EGFR mutations or other identified oncogenic drivers such as NTRK in MSH2/MLH1-mutant CRCs or other tumors with mismatch repair deficiency.

The current work reveals that TrkC receptor is crucial to many aspects of tumorigenicity and metastasis of cancer. However, with only a few exceptions, such as colorectal cancer (CRC), where suppressing tumorigenic and metastatic ability via expression of TrkC as tumor suppressor have been proposed. These diverse lines of evidence led us to investigate whether TrkC is involved in CRC progression. By using mouse models and molecular biology analyses, we demonstrate that TrkC acts as an activator in tumorigenicity and metastasis of colorectal cancer. In this study, TrkC was frequently overexpressed in CRC cells, patients' tumor samples and an azoxymethane/dextran sulphate sodium-induced mouse model of colitis-associated CRCs. TrkC expression was associated with a high-grade CRC phenotype, leading to significantly poorer survival. Also, TrkC expression promoted the acquisition of motility and invasiveness in CRC. Moreover, TrkC increased the ability to form tumor spheroids, a property associated with cancer stem cells. Importantly, knockdown of TrkC in malignant mouse or human CRC cells inhibited tumor growth and metastasis in a mouse xenograft model. Furthermore, TrkC enhanced metastatic potential and induced proliferation by aberrant gain of AKT activation and suppression of transforming growth factor (TGF)-β signalling. Interestingly, TrkC not only modulated the actions of TGF-β type II receptor, but also attenuated expression of this receptor. These findings reveal an unexpected physiological role of TrkC in the pathogenesis of CRC. Therefore, TrkC is a potential target for designing effective therapeutic strategies for CRC development.

Spitzoid neoplasms are a distinct group of melanocytic tumors. Genetically, they lack mutations in common melanoma-associated oncogenes. Recent studies have shown that spitzoid tumors may contain a variety of kinase fusions, including ROS1, NTRK1, ALK, BRAF, and RET fusions. We report herein the discovery of recurrent NTRK3 gene rearrangements in childhood melanocytic neoplasms with spitzoid and/or atypical features, based on genome-wide copy number analysis by single-nucleotide polymorphism array, which showed intragenic copy number changes in NTRK3. Break-apart fluorescence in situ hybridization confirmed the presence of NTRK3 rearrangement, and a novel MYO5A-NTRK3 transcript, representing an in-frame fusion of MYO5A exon 32 to NTRK3 exon 12, was identified using a rapid amplification of cDNA ends-based anchored multiplex PCR assay followed by next-generation sequencing. The predicted MYO5A-NTRK3 fusion protein consists of several N-terminal coiled-coil protein dimerization motifs encoded by MYO5A and C-terminal tyrosine kinase domain encoded by NTRK3, which is consistent with the prototypical structure of TRK oncogenic fusions. Our study also demonstrates how array-based copy number analysis can be useful in discovering gene fusions associated with unbalanced genomic aberrations flanking the fusion points. Our findings add another potentially targetable kinase fusion to the list of oncogenic fusions in melanocytic tumors.

BACKGROUND: The BRAF
METHODS: Among 63 postoperative specimens of childhood and adolescent PTCs, which had been discovered by the thyroid ultrasound screening program in Fukushima, nine samples without prevalent known oncogenes, BRAF
RESULTS: Of the above nine samples, five samples were suspected to harbor a fusion, and using subsequent 5' rapid amplification of cDNA end (RACE), two already reported fusion oncogenes, STRN/ALK and TPR/NTRK1, and three novel fusions, SQSTM1/NTRK3, AFAP1L2/RET, and PPFIBP2/RET, were identified. Functional analyses of these three chimeric genes were performed, and their transforming abilities were confirmed through the activation of mitogen-activated protein kinase (MAPK).
CONCLUSIONS: Three novel fusion oncogenes have been identified in young PTC patients in Fukushima, suggesting that rare fusions may be present among the cases negative for known oncogenes in this age group and that such rearrangements can play a significant role in thyroid carcinogenesis.

Entrectinib, a potent oral inhibitor of the tyrosine kinases TRKA/B/C, ROS1, and ALK, was evaluated in two phase I studies in patients with advanced or metastatic solid tumors, including patients with active central nervous system (CNS) disease. Here, we summarize the overall safety and report the antitumor activity of entrectinib in a cohort of patients with tumors harboring