Prevalence and detection methodology for preliminary exploration of NTRK fusion in gastric cancer from a single-center retrospective cohort.

The fusion of neurotrophic tyrosine receptor kinase (NTRK) is a novel target for cancer therapy and offers hope for patients with gastric cancer (GC). However, there are few studies on the prevalence and detection methods of NTRK fusions in GC. In this study, we used immunohistochemistry (IHC) as a screening method to select cases for molecular testing and evaluated the effectiveness of IHC, fluorescence in situ hybridization (FISH), and next-generation sequencing (NGS). We retrospectively collected 1970 patients with GC. Pan-TRK IHC was conducted in all cases, and three cases were positive: one with strong and diffuse cytoplasmic staining, while two with weak cytoplasmic staining. All three cases were validated using NTRK1/2/3 FISH. FISH results revealed a single 3' signal of NTRK1 in 95% of the tumor cells in the first case, while the remaining two cases were negative. NGS confirmed LMNA-NTRK1 fusion in the first case, with no gene fusion detected in the other two cases. Out of 46 negative controls, one had a non-functional fusion of IGR-NTRK1, and four had point mutations. The case with LMNA-NTRK1 fusion were negative for pMMR, EBV, HER2, and AFP. The pan-TRK IHC showed a 33.33% (1/3) concordance rate with RNA-based NGS. If the criterion for positivity was 3+ cytoplasmic staining, the agreement between IHC and RNA-based NGS was 100% (1/1). In conclusion, the incidence of NTRK fusion in GC is extremely low (0.05%). If the criteria are strict, pan-TRK IHC is highly effective for screening NTRK fusions. FISH could complement NGS detection, particularly when NTRK fusion is detected by DNA sequencing. NTRK fusion in GC may not be limited to specific subtypes.

Mutation of neurotrophic tyrosine receptor kinase can promote pan-cancer immunity and the efficacy of immunotherapy.

The Neurotrophic tyrosine receptor kinase (NTRK) family plays important roles in tumor progression and is involved in tumor immunogenicity. Here, we conducted a comprehensive bioinformatic and clinical analysis to investigate the characteristics of NTRK mutations and their association with the outcomes in pan-cancer immunotherapy. In 3888 patients across 12 cancer types, patients with NTRK-mutant tumors showed more benefit from immunotherapy in terms of objective response rate (ORR; 41.7% vs. 27.5%; P < 0.001), progress-free survival (PFS; HR = 0.80; 95% CI, 0.68-0.96; P = 0.01), and overall survival (OS; HR = 0.71; 95% CI, 0.61-0.82; P < 0.001). We further constructed and validated a nomogram to estimate survival probabilities after the initiation of immunotherapy. Multi-omics analysis on intrinsic and extrinsic immune landscapes indicated that NTRK mutation was associated with enhanced tumor immunogenicity, enriched infiltration of immune cells, and improved immune responses. In summary, NTRK mutation may promote cancer immunity and indicate favorable outcomes in immunotherapy. Our results have implications for treatment decision-making and developing immunotherapy for personalized care.

Modification of a Selective NTRK2 Agonist and Confirmation of Activity in a Glaucoma-on-a-Chip Model.

Purpose: RNYK is a selective agonist of the neurotrophic tyrosine kinase receptor type 2 (NTRK2) which has been screened from a phage-displayed peptide library. Its sequence is SGVYKVAYDWQH, similar to a native NTRK2 ligand, that is, brain-derived neurotrophic factor (BDNF). The current study was performed to recognize and confirm critical residues for RNYK activity in a glaucoma-on-a-chip model. Methods: We designed a modified RNYK (mRNYK) peptide based on hotspots of the RNYK sequence identified by alanine scanning. The critical residues consisted of tyrosine, valine, aspartic acid, and tryptophan (YVDW); however, lysine and glutamine were also maintained in the final sequence (YKVDWQ) for forming amide bonds and peptide dimerization. The affinity of mRNYK binding was confirmed by testing against NTRK2 receptors on the surface of ATRA-treated SH-SY5Y cells. The neuroprotective effect of mRNYK was also evaluated in cell culture after elevated pressure insult in a glaucoma-on-a-chip model. Results: The primary amine on the lysine side-chain from one sequence (YKVDWQ) reacted with a γ-carboxamide group of glutamine from the other sequence, forming dimeric mRNYK. In silico, molecular dynamic simulations of the mRNYK-NTRK2 complex showed more stable and stronger interactions as compared to the RNYK-NTRK2 complex. In vitro, mRNYK demonstrated a neuroprotective effect on SH-SY5Y cells under normal and elevated pressure comparable to RNYK. The 50% effective concentration (logEC50) for mRNYK was 0.7009, which was better than RNYK with a logEC50 of 0.8318. Conclusion: The modified peptide studied herein showed improved stability over the original peptide (RNYK) and demonstrated potential for use as a BDNF agonist with neuroprotective properties for treatment of neurodegenerative disorders such as glaucoma.

[Detection and Significance of Molecular Markers in Immunotherapy and Targeted Therapy of Colorectal Cancer in Tibet].

Objective To study the expression of SWI/SNF-related,matrix-associated,actin-dependent regulator of chromatin,subfamily A,member 4(SMARCA4)/Brahma-related gene 1,V-raf murine sarcoma viral oncogene homolog B(BRAF),P53,programmed cell death protein-1(PD-1),and programmed death-ligand 1(PD-L1),and changes in the expression of BRAF and neurotrophic tyrosine receptor kinase(NTRK) in the patients with colorectal cancer in Tibet,thereby providing a basis for targeted therapy and immunotherapy for this disease in Tibet. Methods A total of 64 patients with colorectal cancer resected in the Tibet Autonomous Region People's Hospital from January 2015 to July 2021 were enrolled in this study.The expression of SMARCA4,BRAF,P53,PD-1,and PD-L1 was detected by immunohistochemical staining.The gene fusion involving NTRK1,NTRK2,and NTRK3 was detected by fluorescence in situ hybridization,and the BRAF V600E gene mutation by polymerase chain reaction. Results The 64 patients with colorectal cancer were at a male-to-female ratio of 1.21∶1,with the mean age of (56.59±13.27) years.The tumors were located in the colon in 46(71.88%) patients and in the rectum in 18(28.12%) patients.Sixty(93.75%) patients presented adenocarcinoma,and 4(6.25%) patients presented other types of tumors.The patients in T1/T2 and T3/T4 phases accounted for 17.19%(n=11) and 82.81%(n=53),respectively.Lymph node metastasis occurred in 24(37.50%) patients.The immunohistochemical staining results showed partially down-regulated or absent expression of SMARCA4 in 1(1.56%) patient,positive BRAF expression in 4(6.25%) patients,and mutant expression of P53 in 35(54.69%) patients.The PD-1-expressing tumor associated immune cell was proportion score<10% in 45(70.31%) patients and≥10% in 19(29.69%) patients.The PD-L1 combined positive score was<10 in 52(81.25%) patients and≥10 in 12(18.75%) patients.The gene fusion of NTRK1,NTRK2,and NTRK3 was negative in all the patients,and BRAF V600E gene mutation was positive in 4(6.25%) patients.The SMARCA4 gene alteration was not detected in the patient with partial expression missing of SMARCA4.The PD-L1 combine positive score was correlated with the deficient mismatch repair(dMMR)/microsatellite instability-high (MSI-H) and the PD-1 expression (χ2=10.223,P=0.001;χ2=11.979,P=0.001). Conclusions The down-regulated or absent SMARCA4 expression and NTRK gene fusion are rare in the patients with colorectal cancer in Tibet.A few patients present BRAF V600E gene mutations,and Pan-TRK and BRAF expression can be used for the primary screening of NTRK gene fusion and BRAF gene mutation.The patients with dMMR/MSI-H are prone to high expression of PD-L1 and expected to benefit from immunotherapy.No significant correlation exists between P53 mutation and PD-L1 expression.The high expression of PD-1 is positively correlated with the high expression of PD-L1.

Nicotine downregulates miR-375-3p via neurotrophic tyrosine receptor kinase 2 to enhance the malignant behaviors of laryngopharyngeal squamous epithelial cells.

Nicotine exposure from smoking constitutes a significant global public health concern. Furthermore, smoking represents a pivotal risk factor for head and neck squamous cell carcinoma (HNSCC). However, the influence of nicotine on HNSCC remains relatively underexplored. Our aim was to unravel the molecular mechanisms that underlie the effect of nicotine on the metastatic cascade of HNSCC. In this study, we discovered a significant association between smoking and HNSCC metastasis and prognosis. Nicotine significantly enhanced HNSCC cell proliferation, migration, invasion, and epithelial-mesenchymal transition (EMT) in vitro. Analysis of TCGA-HNSCC and FDEENT-HNSCC cohorts revealed reduced miR-375-3p levels in HNSCC tumor tissues, particularly among current smokers. Additionally, miR-375-3p level was strongly correlated with both lymph node metastasis and tumor stage. By downregulating miR-375-3p, nicotine promotes HNSCC cell metastasis in vitro and hematogenous metastatic capacity in vivo. Utilizing transcriptomic sequencing, molecular docking, dual-luciferase reporter assay, and fluorescence in situ hybridization (FISH), we demonstrated that miR-375-3p specifically binds to 3' untranslated region (3'UTR) of NTRK2 mRNA. Thus, this study uncovers a novel nicotine-induced mechanism involving miR-375-3p-mediated NTRK2 targeting, which promotes HNSCC metastasis. These findings have implications for improving the prognosis of patients with HNSCC, especially in smokers.

Imaging characterization of paediatric tumours with the neurotrophic tyrosine receptor kinase fusion transcript.

OBJECTIVES: The neurotrophic tyrosine receptor kinase (NTRK) fusion transcript (FT) is a major genetic landmark of infantile fibrosarcoma (IFS) and cellular congenital mesoblastic nephroma (cCMN) but is also described in other tumours. The recent availability of NTRK-targeted drugs enhances the need for better identification. We aimed to describe the anatomic locations and imaging features of tumours with NTRK-FT in children. CASE SERIES: Imaging characteristics of NTRK-FT tumours of 41 children (median age: 4 months; 63% <1 year old; range: 0-188) managed between 2001 and 2019 were retrospectively analysed. The tumours were located in the soft tissues (n = 24, including 19 IFS), kidneys (n = 9, including 8 cCMN), central nervous system (CNS) (n = 5), lung (n = 2), and bone (n = 1). The tumours were frequently deep-located (93%) and heterogeneous (71%) with necrotic (53%) or haemorrhagic components (29%). Although inconstant, enlarged intratumoural vessels were a recurrent finding (70%) with an irregular distribution (63%) in the most frequent anatomical locations. CONCLUSION: Paediatric NTRK-FT tumours mainly occur in infants with very variable histotypes and locations. Rich and irregular intra-tumoural vascularization are recurrent findings. ADVANCES IN KNOWLEDGE: Apart from IFS of soft tissues and cCMN of the kidneys, others NTRK-FT tumours locations have to be known, as CNS tumours. Better knowledge of the imaging characteristics may help guide the pathological and biological identification.

Impact of tissue-agnostic approvals on management of primary brain tumors.

Novel tissue-agnostic therapeutics targeting driver mutations in tumor cells have been recently approved by FDA, driven by basket trials that have demonstrated their efficacy and safety across diverse tumor histology. However, the relative rarity of primary brain tumors (PBTs) has limited their representation in early trials of tissue-agnostic medications. Thus, consensus continues to evolve regarding utility of tissue-agnostic medications in routine practice for PBTs, a diverse group of neoplasms characterized by limited treatment options and unfavorable prognoses. We describe current and potential impact of tissue-agnostic approvals on management of PBTs. We discuss data from clinical trials for PBTs regarding tissue-agnostic targets, including BRAFV600E, neurotrophic tyrosine receptor kinase (NTRK) fusions, microsatellite instability-high (MSI-High), mismatch repair deficiency (dMMR), and high tumor mutational burden (TMB-H), in context of challenges in managing PBTs. Described are additional tissue-agnostic targets that hold promise for benefiting patients with PBTs, including RET fusion, fibroblast growth factor receptor (FGFR), ERBB2/HER2, and KRASG12C, and TP53Y220C.

Oncogenic fusions: Targeting NTRK.

Non-Small Cell Lung Cancer (NSCLC) is responsible for the highest number of cancer-related deaths in the United States. Thankfully, advancements in the detection and targeting of gene mutations have greatly improved outcomes for many patients. One significant mutation driving oncogenesis in various cancers, including NSCLC, is the neurotrophic tyrosine receptor kinase (NTRK) fusion. Presently, larotrectinib and entrectinib are the only FDA-approved therapies for NTRK-mutated cancers. Despite the efficacy and tolerability exhibited by these therapies, several clinical hurdles persist for physicians, including resistance mutations and limited penetration of the central nervous system (CNS), which diminishes their effectiveness. The treatment landscape for NTRK cancers is still being explored, with numerous new tyrosine kinase inhibitors currently in development or undergoing phase 1 and 2 clinical trials. In this review, we delve into both established and novel therapies targeting NTRK-mutated NSCLC.

NTRK rearranged sarcoma of the bone. Role for larotrectinib in the neoadjuvant setting of an ultra-rare tumor: a case report.

BACKGROUND: Neurotrophic tyrosine receptor kinase (NTRK) gene-fusion targeted molecules revolutionized the paradigm of treatment of a limited subgroup of cancers of various histologies. Entrectinib and larotrectinib obtained unprecedented response rates in patients with cancer harboring NTRK rearrangements. This evidence recently led to the agnostic approval of these drugs, and evidence (confirmation) of their activity in a broader disease setting is emerging. Here, we report the case of a patient affected by EML4-NTRK3 rearranged undifferentiated spindle cell bone sarcoma treated with larotrectinib, and we argue (discuss about) the incidence and clinical presentation of NTRK gene-fusion positive bone sarcomas, the potential use of upfront treatment with NTRK inhibitors in neoadjuvant setting, and the role of a multidisciplinary tumor board. Despite the rarity of these rearrangements in patients with primitive bone sarcomas, the therapy with NTRK inhibitors represents a highly effective strategy to be pursued in selected cases even in neoadjuvant settings. The management of these very rare cancers should always be discussed in a multidisciplinary board of reference centers.

Paradigm shift of chemotherapy and systemic treatment for biliary tract cancer.

Biliary tract cancers (BTC) are frequently identified at late stages and have a poor prognosis due to limited systemic treatment regimens. For more than a decade, the combination of gemcitabine and cis-platin has served as the first-line standard treatment. There are few choices for second-line chemo-therapy. Targeted treatment with fibroblast growth factor receptor 2 inhibitors, neurotrophic tyrosine receptor kinase inhibitors, and isocitrate dehydrogenase 1 inhibitors has had important results. Immune checkpoint inhibitors (ICI) such as pembrolizumab are only used in first-line treatment for microsatellite instability high patients. The TOPAZ-1 trial's outcome is encouraging, and there are several trials underway that might soon put targeted treatment and ICI combos into first-line options. Newer targets and agents for existing goals are being studied, which may represent a paradigm shift in BTC management. Due to a scarcity of targetable mutations and the higher toxicity profile of the current medications, the new category of drugs may occupy a significant role in BTC therapies.

NTRK gene aberrations in triple-negative breast cancer: detection challenges using IHC, FISH, RT-PCR, and NGS.

Triple-negative breast cancer (TNBC) is usually an aggressive disease with a poor prognosis and limited treatment options. The neurotrophic tyrosine receptor kinase (NTRK) gene fusions are cancer type-agnostic emerging biomarkers approved by the Food and Drug Administration (FDA), USA, for the selection of patients for targeted therapy. The main aim of our study was to investigate the frequency of NTRK aberrations, i.e. fusions, gene copy number gain, and amplification, in a series of TNBC using different methods. A total of 83 TNBCs were analyzed using pan-TRK immunohistochemistry (IHC), fluorescence in situ hybridization (FISH), real-time polymerase chain reaction (RT-PCR), and RNA-based next-generation sequencing (NGS). Of 83 cases, 16 showed pan-TRK positivity although no cases had NTRK-fusions. Indeed, FISH showed four cases carrying an atypical NTRK1 pattern consisting of one fusion signal and one/more single green signals, but all cases were negative for fusion by NGS and RT-PCR testing. In addition, FISH analysis showed six cases with NTRK1 amplification, one case with NTRK2 copy number gain, and five cases with NTRK3 copy number gain, all negative for pan-TRK IHC. Our data demonstrate that IHC has a high false-positive rate for the detection of fusions and molecular testing is mandatory; there is no need to perform additional molecular tests in cases negativity for NTRK by IHC. In conclusion, the NTRK genes are not involved in fusions in TNBC, but both copy number gain and amplification are frequent events, suggesting a possible predictive role for other NTRK aberrations.

Case report: Complete and durable response to larotrectinib (TRK inhibitor) in an infant diagnosed with angiosarcoma harbouring a KHDRBS1-NTRK3 fusion gene.

Significant improvements in the survival rates of paediatric cancer have been achieved over the past decade owing to recent advances in therapeutic and diagnostic strategies. However, disease progression and relapse remain a major challenge for the clinical management of paediatric angiosarcoma. Comprehensive genomic profiling of these rare tumours using high-throughput sequencing technologies may improve patient stratification and identify actionable biomarkers for therapeutic intervention. Here, we describe the clinical, histopathological, immunohistochemical and molecular profile of a novel and precision medicine-informed case where a KHDRBS1-NTRK3 fusion determined by next-generation sequencing-based comprehensive genomic profiling led to complete and sustained remission (clinical and radiological response) in an otherwise incurable disease. Our patient represents the first paediatric angiosarcoma harbouring a targetable NTRK3 fusion in the literature and demonstrates the first example of targeting this alteration in angiosarcoma using larotrectinib, an NTRK inhibitor. Clinical and radiological remission was achieved in under two months of therapy, and the patient is currently in complete remission, 4 month after stopping larotrectinib therapy, which was given over 17 months with only mild side effects reported. Therefore, this remarkable case exemplifies the true essence of precision-based care by incorporating conventional pathology with the why, when, and how to test for rare oncogenic drivers and agnostic biomarkers in paediatric angiosarcoma.

ISO 15189 is a sufficient instrument to guarantee high-quality manufacture of laboratory developed tests for in-house-use conform requirements of the European In-Vitro-Diagnostics Regulation.

The EU In-Vitro Diagnostic Device Regulation (IVDR) aims for transparent risk-and purpose-based validation of diagnostic devices, traceability of results to uniquely identified devices, and post-market surveillance. The IVDR regulates design, manufacture and putting into use of devices, but not medical services using these devices. In the absence of suitable commercial devices, the laboratory can resort to laboratory-developed tests (LDT) for in-house use. Documentary obligations (IVDR Art 5.5), the performance and safety specifications of ANNEX I, and development and manufacture under an ISO 15189-equivalent quality system apply. LDTs serve specific clinical needs, often for low volume niche applications, or correspond to the translational phase of new tests and treatments, often extremely relevant for patient care. As some commercial tests may disappear with the IVDR roll-out, many will require urgent LDT replacement. The workload will also depend on which modifications to commercial tests turns them into an LDT, and on how national legislators and competent authorities (CA) will handle new competences and responsibilities. We discuss appropriate interpretation of ISO 15189 to cover IVDR requirements. Selected cases illustrate LDT implementation covering medical needs with commensurate management of risk emanating from intended use and/or design of devices. Unintended collateral damage of the IVDR comprises loss of non-profitable niche applications, increases of costs and wasted resources, and migration of innovative research to more cost-efficient environments. Taking into account local specifics, the legislative framework should reduce the burden on and associated opportunity costs for the health care system, by making diligent use of existing frameworks.

Tropomyosin-Related Kinase Fusions in Gastrointestinal Stromal Tumors.

The canonical mutations in gastrointestinal stromal tumors (GISTs) are typically activating mutations in KIT and platelet-derived growth factor receptor alpha (PDGFRA). GISTs with non-canonical mutations are a heterogeneous group. Here, we examined tropomyosin-related kinase (TRK) fusion in GIST cases without KIT/PDGFRA mutations (KIT/PDGFRA wild-type (WT) GISTs). We retrospectively analyzed patients who were diagnosed with GISTs at the Yonsei Cancer Center, Severance Hospital, between January 1998 and December 2016. Thirty-one patients with KIT/PDGFRA WT GISTs were included in the analysis. TRK expression in tumor samples was assessed by pan-TRK immunohistochemistry (IHC), and the neurotrophic tyrosine receptor kinase (NTRK: the gene encoding TRK) rearrangement was analyzed by fluorescence in situ hybridization (FISH). IHC analyses revealed that five cases in this cohort exhibited a weak to moderate TRK expression. NTRK1 fusions were detected in three tumor samples, and two samples harbored NTRK3 fusions. The remaining 26 samples did not harbor NTRK fusions. Two types of NTRK fusions were detected, and the overall NTRK fusion frequency in KIT/PDGFRA WT GIST cases was 16% (5/31). Our data provide insights into the molecular alterations underpinning KIT/PDGFRA WT GISTs. More effort should be devoted to improve methods to identify this distinct disease subtype within the KIT/PDGFRA WT GIST group.

New Approaches with Precision Medicine in Adult Brain Tumors.

Primary central nervous system (CNS) tumors represent a heterogenous group of tumors. The 2021 fifth edition of the WHO Classification of Tumors of the CNS emphasizes the advanced role of molecular diagnostics with routine implementation of molecular biomarkers in addition to histologic features in the classification of CNS tumors. Thus, novel diagnostic methods such as DNA methylome profiling are increasingly used to provide a more precise diagnostic work-up of CNS tumors. In addition to these diagnostic precision medicine advantages, molecular alterations are also addressed therapeutically with targeted therapies. Like in other tumor entities, precision medicine has therefore also arrived in the treatment of CNS malignancies as the application of targeted therapies has shown promising response rates. Nevertheless, large prospective studies are currently missing as most targeted therapies were evaluated in single arm, basket, or platform trials. In this review, we focus on the current evidence of precision medicine in the treatment of primary CNS tumors in adults. We outline the pathogenic background and prevalence of the most frequent targetable genetic alterations and summarize the existing evidence of precision medicine approaches for the treatment of primary CNS tumors.

GISTs with NTRK Gene Fusions: A Clinicopathological, Immunophenotypic, and Molecular Study.

The most common mutations in gastrointestinal stromal tumors (GISTs) are KIT or PDGFRA mutations. Recently, neurotrophic tyrosine receptor kinase (NTRK) fusions have been reported in WT GISTs, which increased interest in introducing tropomyosin receptor kinase (TRK) inhibitors as treatments for GISTs with NTRK fusions. Hence, we aimed to screen NTRK fusions in WT GISTs; we used fluorescence in situ hybridization (FISH), next-generation sequencing (NGS), and immunohistochemistry (IHC) to screen NTRK fusions in 46 WT GISTs and evaluate each method. We further reviewed NTRK fusion-positive GISTs from the literature and performed clinical and pathological analyses; two GISTs with an ETV6-NTRK3 fusion (5%) were identified, while only one (50%) was positive for Pan-TRK expression. On the other hand, among the six GISTs with Pan-TRK-positive expression, only one (17%) harbored NTRK fusion. The literature review revealed the strong consistency between FISH and NGS and the limited value of Pan-TRK IHC in screening NTRK fusions in GISTs. In addition, the clinical and pathological analysis showed that GISTs with NTRK rearrangement occurred less frequently in the stomach, were more frequently larger in size, and the epithelioid type presented with a higher risk of recurrence. The NTRK3 fusion has been more common than the NTRK1 fusion in GISTs to date; our study identified two ETV6-NTRK3 fusions in 46 WT GISTs. Compared with FISH and IHC, NGS is preferred for screening WT GISTs, including NTRK rearrangements. However, since GISTs with NTRK fusions are rare, further studies including more samples and mechanistic investigations should be conducted in the future.

P75NTR Exacerbates SCI-induced Mitochondrial Damage and Neuronal Apoptosis Depending on NTRK3.

OBJECTIVE: The aim of the study was to investigate the mechanism by which p75 neurotrophin receptor (p75NTR) affects mitochondrial damage and neuronal apoptosis in spinal cord injury (SCI). METHODS: After the establishment of SCI rat models, short hairpin (sh) RNA of p75NTR and control sh-RNA were injected into SCI rats, respectively. On days 1, 7 and 21 after SCI, the severity of SCI and cell apoptosis in SCI rats were determined as well as the recovery of hind limb performance and p75NTR expression. After spinal cord neurons were transfected with p75NTR overexpression plasmid or empty plasmid vector or cotransfected with overexpression plasmids of p75NTR and neurotrophic tyrosine receptor kinase3 (NTRK3), the expression levels of p75NTR and NTRK3 were quantified. Moreover, we detected the apoptosis and proliferation rates of the neurons in addition to the levels of reactive oxygen species (ROS) and mitochondrial membrane potential (MMP) in the neurons. The binding between p75NTR and NTRK3 was confirmed via Co-immunoprecipitation (Co-IP). RESULTS: The rat spinal cords in the Model group were notably damaged after SCI accompanied by increased apoptosis and decreased locomotor function. The expression of p75NTR was significantly upregulated after SCI. The aforementioned injuries were remarkably ameliorated in response to injection of sh-p75NTR. p75NTR overexpression induced mitochondrial damage and neuronal apoptosis in spinal cord neurons, while the promotive effects were perturbed by NTRK3 overexpression. Furthermore, p75NTR directly bound to and downregulated NTRK3. CONCLUSION: Both in vivo and in vitro experiments showed that p75NTR aggravates mitochondrial damage and neuronal apoptosis in SCI through downregulating NTRK3.

Activation of HERV-K(HML-2) disrupts cortical patterning and neuronal differentiation by increasing NTRK3.

The biological function and disease association of human endogenous retroviruses (HERVs) are largely elusive. HERV-K(HML-2) has been associated with neurotoxicity, but there is no clear understanding of its role or mechanistic basis. We addressed the physiological functions of HERV-K(HML-2) in neuronal differentiation using CRISPR engineering to activate or repress its expression levels in a human-pluripotent-stem-cell-based system. We found that elevated HERV-K(HML-2) transcription is detrimental for the development and function of cortical neurons. These effects are cell-type-specific, as dopaminergic neurons are unaffected. Moreover, high HERV-K(HML-2) transcription alters cortical layer formation in forebrain organoids. HERV-K(HML-2) transcriptional activation leads to hyperactivation of NTRK3 expression and other neurodegeneration-related genes. Direct activation of NTRK3 phenotypically resembles HERV-K(HML-2) induction, and reducing NTRK3 levels in context of HERV-K(HML-2) induction restores cortical neuron differentiation. Hence, these findings unravel a cell-type-specific role for HERV-K(HML-2) in cortical neuron development.

NTRK Fusions and TRK Inhibitors: Potential Targeted Therapies for Adult Glioblastoma.

INTRODUCTION: Glioblastoma multiforme (GBM) is the most common primary central nervous (CNS) system malignancy with a poor prognosis. The standard treatment for GBM is neurosurgical resection, followed by radiochemotherapy and adjuvant temozolomide chemotherapy. Predictive biomarkers, such as methylation of the promoter region of the O6-methylguanine DNA methyltransferase (MGMT) gene, can successfully distinguish subgroups with different prognosis after temozolomide chemotherapy. Based on multiomics studies, epidermal growth factor receptor (EGFR), vascular endothelial growth factor (VEGF), BRAF V600E mutation, neurotrophic tyrosine receptor kinase (NTRK) fusions and other potential therapy targets have been found. METHODS: We have reviewed the preclinical and clinical evidence for NTRK fusions and TRK inhibitors therapy in cancers with NTRK fusions in pan-cancer and gliomas. RESULTS: Several NTRK1/2/3 fusions have been reported in GBM and preclinical studies have proven that NTRK fusions are potential driver mutations in some high-grade gliomas. Tropomyosin receptor kinase (TRK) inhibitors have shown efficacy as targeted therapies for extracranial tumors with NTRK fusions in recent clinical trials, with potential CNS tolerability and activity. However, whether NTRK gene fusions can affect survival status, the efficacy and resistance of TRK inhibitors in GBMs are lacking high-level evidences. CONCLUSIONS: For GBM patients, NTRK fusions and TRK inhibitors are potential target therapy strategy but remain biological mechanism and clinical significance unclarified. More clinical data and future clinical trials are needed to provide more evidence that supports targeted therapy for GBM with NTRK fusions.

Neurotrophic tyrosine kinase inhibitors: A review of implications for patients, clinicians and healthcare services.

Neurotrophic tyrosine receptor kinase (NTRK) inhibitors represent the latest advancement as a treatment option in targeted therapies for malignant disease. NTRK gene fusions involving NTRK1, 2 or 3 are implicated as genetics drivers for a number of tumour types which arise within adult and paedatric patients. NTRK inhibitors (Larotrectinib and Entrectinib) are effective agents which have demonstrated clinical benefit in the treatment of NTRK fusion positive solid tumours. Larotrectinib represents the first targeted agent to receive approval from international authorisation and commissioning bodies for the treatment of a specific genetic expression indiscriminate of the site from which the tumour has arisen. As such NTRK inhibitors could pave the way for international healthcare bodies to adopt a similar approach for future targeted therapies thereby altering the manner in which healthcare providers and patients are able to access and utilise innovative, targeted treatment options in future. The potential implications of this new approach are likely to impact upon several aspects of the traditional authorisation and commissioning pathways with potential changes to the design of clinical trials, the review and approval process by regulatory bodies and immunohistopathology services.