Prior immune checkpoint inhibitors may enhance severe hypersensitivity related to selpercatinib in RET fusion gene-positive lung cancer

Selpercatinib, a tyrosine kinase inhibitor approved for RET-fusion gene-positive lung cancer, can induce hypersensitivity, potentially exacerbated by prior immune checkpoint inhibitor (ICI) therapy. We present a case of severe toxicity following selpercatinib treatment in a 58-year-old female with lung adenocarcinoma, refractory to previous treatments including pembrolizumab. Symptoms included fever, rash, and multiorgan failure indicative of grade 4 hypersensitivity. Treatment involved platelet transfusion, heparin therapy, and prednisolone, leading to improvement upon selpercatinib cessation. This case highlights the importance of monitoring for hypersensitivity reactions in patients treated with selpercatinib, especially following prior ICI therapy.

Creatine Kinase-MM/Proto-oncogene Tyrosine-Protein Kinase Receptor as a Sensitive Indicator for Duchenne Muscular Dystrophy Carriers

Duchenne muscular dystrophy (DMD), a lethal X-linked recessive genetic disease, is characterized by progressive muscle wasting which will lead to premature death by cardiorespiratory complications in their late twenties. And 2.5-19% DMD carriers that also suffer from skeletal muscle damage or dilated cardiomyopathy when diagnosed as soon as possible is meaningful for prenatal diagnosis and advance warning for self-health. The current DMD carrier screening mainly relies on detecting serum creatine kinase activity, covering only 50-70% DMD carriers which will cause many false negatives and require the discovery of highly effective biomarker and simple detection procedure for DMD carriers. In this article, we have compiled a comprehensive summary of all documented biomarkers associated with DMD and categorized them based on their expression patterns. We specifically pinpointed novel DMD biomarkers, previously unreported in DMD carriers, and conducted further investigations to explore their potential. Compared to creatine kinase activity alone in DMD carriers, creatine kinase-MM can improve the specificity from 73 to 81%. And our investigation revealed another promising protein: proto-oncogene tyrosine-protein kinase receptor (RET). When combined with creatine kinase-MM (creatine kinase-MM/RET ratio), it significantly enhances the specificity (from 81 to 83%) and sensitivity (from 71.4 to 93%) of detecting DMD carriers in serum. Moreover, we successfully devised an efficient method for extracting RET from dried blood spots. This breakthrough allowed us to detect both creatine kinase-MM and RET using dried blood spots without compromising the detection rate.

Discovery of 9H-pyrimido[4,5-b]indole derivatives as dual RET/TRKA inhibitors

Aberrant RET kinase signaling is activated in numerous cancers including lung, thyroid, breast, pancreatic, and prostate. Recent approvals of selective RET inhibitors, pralsetinib and selpercatinib, has shifted the focus of RET kinase drug discovery programs towards the development of selective inhibitors. However, selective inhibitors invariably lose efficacy as the selective nature of the inhibitor places Darwinian-like pressure on the tumor to bypass treatment through the selection of novel oncogenic drivers. Further, selective inhibitors are restricted for use in tumors with specific genetic backgrounds that do not encompass diverse patient classes. Here we report the identification of a pyrimido indole RET inhibitor found to also have activity against TRK. This selective dual RET/TRK inhibitor can be utilized in tumors with both RET and TRK genetic backgrounds and can also provide blockade of NTRK-fusions that are selected for from RET inhibitor treatments. Efforts towards developing dual RET/TRK inhibitors can be beneficial in terms of encompassing more diverse patient classes while also achieving blockade against emerging resistance mechanisms.

Next-generation sequencing identified that RET variation associates with lymph node metastasis and the immune microenvironment in thyroid papillary carcinoma

BACKGROUND

To date, although most thyroid carcinoma (THCA) achieves an excellent prognosis, some patients experience a rapid progression episode, even with differentiated THCA. Nodal metastasis is an unfavorable predictor. Exploring the underlying mechanism may bring a deep insight into THCA.

METHODS

A total of 108 THCA from Chinese patients with next-generation sequencing (NGS) were recruited. It was used to explore the gene alteration spectrum of THCA and identify gene alterations related to nodal metastasis in papillary thyroid carcinoma (PTC). The Cancer Genome Atlas THCA cohort was further studied to elucidate the relationship between specific gene alterations and tumor microenvironment. A pathway enrichment analysis was used to explore the underlying mechanism.

RESULTS

Gene alteration was frequent in THCA. BRAF, RET, POLE, ATM, and BRCA1 were the five most common altered genes. RET variation was positively related to nodal metastasis in PTC. RET variation is associated with immune cell infiltration levels, including CD8 naïve, CD4 T and CD8 T cells, etc. Moreover, Step 3 and Step 4 of the cancer immunity cycle (CIC) were activated, whereas Step 6 was suppressed in PTC with RET variation. A pathway enrichment analysis showed that RET variation was associated with several immune-related pathways.

CONCLUSION

RET variation is positively related to nodal metastasis in Chinese PTC, and anti-tumor immune response may play a role in nodal metastasis triggered by RET variation.

LncRNA PFAR facilitates the proliferation and migration of papillary thyroid carcinoma by competitively binding to miR-15a

Papillary thyroid carcinoma (PTC) is type of aggressive tumor, with a markedly declined survival rate when distant metastasis occurs. It is of great significance to develop potential biomarkers to evaluate the progression of PTC. LncRNAs are recently widely claimed with biomarker value in malignant tumors. Herein, the role of LncRNA PFAR in PTC was investigated to explore potential prognostic marker for PTC. Compared to NTHY-ORI 3-1 cells, LncRNA PFAR was found markedly upregulated in PTC cell lines. In LncRNA PFAR knockdown TPC-1 cells, markedly declined cell viability, increased apoptotic rate, enhancive number of migrated cells, and elevated migration distance were observed, accompanied by a suppressed activity of the RET/AKT/mTOR signaling. In LncRNA PFAR overexpressed BCPAP cells, signally increased cell viability, declined apoptotic rate, reduced number of migrated cells, decreased migration distance, and increased tumor volume and tumor weight in nude mice xenograft model were observed, accompanied by an activation of the RET/AKT/mTOR signaling. The binding site between LncRNA PFAR and miR-15a, as well as miR-15a and RET, was confirmed by the dual luciferase reporter assay. The FISH study revealed that LncRNA PFAR was mainly located in the cytoplasm. Furthermore, the impact of the siRNA targeting LncRNA PFAR against the growth and migration of PTC cells was abolished by the inhibitor of miR-15a or SC79, an activator of AKT/mTOR signaling. Collectively, LncRNA PFAR facilitated the proliferation and migration of PTC cells by mediating the miR-15a/RET axis.

Loss of tumor suppressor TMEM127 drives RET-mediated transformation through disrupted membrane dynamics

Internalization from the cell membrane and endosomal trafficking of receptor tyrosine kinases (RTKs) are important regulators of signaling in normal cells that can frequently be disrupted in cancer. The adrenal tumor pheochromocytoma (PCC) can be caused by activating mutations of the rearranged during transfection (RET) receptor tyrosine kinase, or inactivation of TMEM127, a transmembrane tumor suppressor implicated in trafficking of endosomal cargos. However, the role of aberrant receptor trafficking in PCC is not well understood. Here, we show that loss of TMEM127 causes wildtype RET protein accumulation on the cell surface, where increased receptor density facilitates constitutive ligand-independent activity and downstream signaling, driving cell proliferation. Loss of TMEM127 altered normal cell membrane organization and recruitment and stabilization of membrane protein complexes, impaired assembly, and maturation of clathrin-coated pits, and reduced internalization and degradation of cell surface RET. In addition to RTKs, TMEM127 depletion also promoted surface accumulation of several other transmembrane proteins, suggesting it may cause global defects in surface protein activity and function. Together, our data identify TMEM127 as an important determinant of membrane organization including membrane protein diffusability and protein complex assembly and provide a novel paradigm for oncogenesis in PCC where altered membrane dynamics promotes cell surface accumulation and constitutive activity of growth factor receptors to drive aberrant signaling and promote transformation.

Seventy years of pheochromocytomas and paragangliomas in Argentina. The FRENAR database

Pheochromocytomas and paragangliomas (PPGL) are neuroendocrine tumors characterized by the excessive production of catecholamines. This study aims to describe the clinical characteristics of PPGL cases in Argentina over recent decades. A multicenter retrospective cross-sectional analysis was carried out using a database comprising both pediatric and adult patients with confirmed PPGL diagnoses based on pathological reports. A cohort of 486 patients with PPGL was recruited. Women represent 58.4% of the patients, with a mean age of 38.3 years old at the time of diagnosis and 15.2% of the patients were under the age of 18. Hypertension, as well as classic signs and symptoms, were present in 80.9% of the patients. The adrenal incidentaloma, as a mode of presentation, increased in the last two decades rising from 3.9% (1953-2000) to 21.8% (2001-2022), p<0.001. Most tumors were located within the adrenal glands, accounting 83.0% of the cases, with bilateral occurrences noted in 20.0%. The median tumor size was 4.8cm. Local recurrence and metastases were observed in 10.9% and 12.2%. Out of 412 patients, 87.0% exhibited urinary excretion elevation of catecholamines and/or their metabolites. Furthermore, 148 patients, representing 30.4% of the study population, displayed a distinct genetic profile indicative of hereditary syndromes. The distribution of hereditary syndromes revealed that MEN2, VHL, and PGL4 constituted the most prevalent syndromes. This population-based study, spanning seven decades, offers valuable insights into the demographic and clinical characteristics of PPGL patients in Argentina.

Clinical Activity of Selpercatinib in RET-mutant Pheochromocytoma

INTRODUCTION

Activating RET alterations have been reported in a variety of solid tumors, including pheochromocytoma where they occur both sporadically and as part of familial multiple endocrine neoplasia type 2 (MEN2) syndromes. Selpercatinib is a first-in-class, highly selective, and potent small molecule RET kinase inhibitor that has demonstrated marked and durable anti-tumor activity in diverse RET-activated solid tumors in the LIBRETTO-001 study (NCT03157128).

METHODS

We describe the first six pheochromocytoma cases treated with selpercatinib in the LIBRETTO-001 study.

RESULTS

Of the six patients (one sporadic and five reported as part of MEN2 syndromes) in this case report, four had a partial response/complete response and two had stable disease per independent review committee. Treatment duration ranged from 9.2 months to more than 56.4 months. The safety profile of treatment was consistent with selpercatinib in other indications.

CONCLUSION

These data support selpercatinib as an effective therapy against RET-mutant pheochromocytoma, adding to the diversity of RET-activated tumor types that may benefit from targeted RET inhibition.

Not Only RET but NF1 and Chromosomal Instability Are Seen in Young Patients with Sporadic Medullary Thyroid Carcinoma

Context

Genetic analysis of sporadic medullary thyroid carcinoma (MTC) has revealed somatic variants in RET, RAS, and occasionally other genes. However, around 20% of patients with sporadic MTC lack a known genetic driver.

Objective

To uncover potential new somatic or germline drivers, we analyze a distinct cohort of patients with sporadic, very early-onset, and aggressive MTC.

Methods

Germline and somatic DNA exome sequencing was performed in 19 patients, previously tested negative for germline RET variants.

Results

Exome sequencing of 19 germline samples confirmed the absence of RET and identified an NF1 pathogenic variant in 1 patient. Somatic sequencing was successful in 15 tumors revealing RET variants in 80%, predominantly p.Met918Thr, which was associated with disease aggressiveness. In RET-negative tumors, pathogenic variants were found in HRAS and NF1. The NF1 germline and somatic variants were observed in a patient without a prior clinical diagnosis of neurofibromatosis type 1, demonstrating that the loss of heterozygosity of NF1 functions as a potential MTC driver. Somatic copy number alterations analysis revealed chromosomal alterations in 53.3% of tumors, predominantly in RET-positive cases, with losses in chromosomes 9 and 22 being the most prevalent.

Conclusion

This study reveals that within a cohort of early-onset nonhereditary MTC, RET remains the major driver gene. In RET-negative tumors, NF1 and RAS are drivers of sporadic MTC. In addition, in young patients without a RET germline mutation, a careful clinical evaluation with a consideration of germline NF1 gene analysis is ideal to exclude Neurofibromatosis type 1 (NF1).

Loss of Tumour Suppressor TMEM127 Drives RET-mediated Transformation Through Disrupted Membrane Dynamics

Internalization from the cell membrane and endosomal trafficking of receptor tyrosine kinases (RTK) are important regulators of signaling in normal cells that can frequently be disrupted in cancer. The adrenal tumour pheochromocytoma (PCC) can be caused by activating mutations of the RET receptor tyrosine kinase, or inactivation of TMEM127, a transmembrane tumour suppressor implicated in trafficking of endosomal cargos. However, the role of aberrant receptor trafficking in PCC is not well understood. Here, we show that loss of TMEM127 causes wildtype RET protein accumulation on the cell surface, where increased receptor density facilitates constitutive ligand-independent activity and downstream signaling, driving cell proliferation. Loss of TMEM127 altered normal cell membrane organization and recruitment and stabilization of membrane protein complexes, impaired assembly, and maturation of clathrin coated pits, and reduced internalization and degradation of cell surface RET. In addition to RTKs, TMEM127 depletion also promoted surface accumulation of several other transmembrane proteins, suggesting it may cause global defects in surface protein activity and function. Together, our data identify TMEM127 as an important determinant of membrane organization including membrane protein diffusability, and protein complex assembly and provide a novel paradigm for oncogenesis in PCC where altered membrane dynamics promotes cell surface accumulation and constitutive activity of growth factor receptors to drive aberrant signaling and promote transformation.

Updates on the genetics of multiple endocrine neoplasia

Multiple endocrine neoplasia (MEN) is a group of syndromes with a genetic predisposition to the appearance of endocrine tumors, and shows autosomal dominant transmission. The advent of molecular genetics has led to improvements in the management of MEN in terms of diagnosis, prognosis and therapy. The genetics of MEN is the subject of regular updates, which will be presented throughout this paper. MEN1, the first to be described, is associated with the MEN1 gene. MEN1 is well known in terms of the observed phenotype, with genetic analysis being conclusive in 90% of patients with a typical phenotype, but is negative in around 10% of families with MEN1. Improvement in analysis techniques and the identification of other genes responsable for phenocopies allows the resolution of some, but not all, cases, notably non-familial forms suspected to be fortuitous assocations with tumors. MEN4 is a rare phenocopy of MEN1 linked to constitutional mutations in the CDKN1B gene. Though it closely resembles the phenotype of MEN1, published data suggests the appearance of tumors is later and less frequent in MEN4. MEN2, which results from mutations in the RET oncogene, shows a strong genotype-phenotype correlation. This correlation is particularly evident in the major manifestation of MEN2, medullary thyroid carcinoma (MTC), in which disease aggressiveness is dependent on the pathogenic variant of RET. However, recent studies cast doubt on this correlation between MTC and pathogenic variant. Lastly, the recent description of families carrying a mutation in MAX, which is known to predispose to the development of pheochromocytoma and paraganglioma, and presents a phenotypic spectrum that evokes MEN, suggests the existence of another syndrome, MEN5.

RET kinase inhibitors for the treatment of RET-altered thyroid cancers: Current knowledge and future directions

RET gain-of-function mutations are the most common drivers in medullary thyroid carcinoma, while RET fusions are identified in 5-10% of papillary thyroid carcinomas. Thus, RET plays a major role in the tumorigenesis of thyroid neoplasia, making it a valuable therapeutic target. Over a decade ago, multikinase inhibitors (MKIs) were first shown to have variable degrees of anti-RET activity. Despite some clinical efficacy in RET-altered thyroid cancers, significant off-target activity of MKIs led to marked toxicities limiting their use. More recently, two potent, highly selective RET inhibitors, selpercatinib and pralsetinib, were shown to have notable efficacy in RET-altered cancers, associated with more tolerable side effect profiles than those of MKIs. However, these treatments are non-curative, and emerging evidence suggests that patients who progress on therapy acquire mutations conferring drug resistance. Thus, the quest for a more definitive treatment for advanced, RET-altered thyroid cancers continues. This year we celebrate the 30th anniversary of the association of germline mutations of the RET proto-oncogene with the multiple endocrine neoplasia (MEN) type 2 syndromes. In this timely review, we summarize the current state-of-the-art treatment strategies for RET-altered thyroid cancers, their limitations, as well as future therapeutic avenues.

Targeting RET alterations in non-small cell lung cancer

Rearranged during transfection (RET) alterations, which lead to aberrant activation of the RET proto-oncogene, have been identified in various cancers. In non-small cell lung cancer (NSCLC), RET mutations often manifest as RET fusion genes and are observed in 1-2 % of patients with NSCLC. In recent years, selective RET inhibitors such as selpercatinib and pralsetinib, approved by the Food and Drug Administration (FDA) in 2020, have been part of the revolutionary changes in the treatment landscape for non-small cell lung cancer. While first-generation RET inhibitors have become part of the standard of care for RET-fusion positive NSCLC, a new challenge has emerged: acquired resistance to RET inhibitors. RET resistance is a complex phenomenon that can manifest as either on-target or off-target resistance. Numerous studies have been conducted to identify the mechanisms behind this resistance. This review provides an overview of the biology of RET in NSCLC, methods of RET testing, and a comprehensive analysis of the clinical outcomes associated with multikinase and selective RET inhibitors for NSCLC. Additionally, we will explore future perspectives for RET fusion-positive NSCLC, including ongoing trials and the challenges involved in overcoming resistance to RET inhibitors.

RET splice site variants in medullary thyroid carcinoma

Introduction: Medullary thyroid carcinoma (MTC) is an aggressive cancer that is often caused by driver mutations in RET. Splice site variants (SSV) reflect changes in mRNA processing, which may alter protein function. RET SSVs have been described in thyroid tumors in general but have not been extensively studied in MTC. Methods: The prevalence of RET SSVs was evaluated in 3,624 cases with next generation sequence reports, including 25 MTCs. Fisher exact analysis was performed to compare RET SSV frequency in cancers with/without a diagnosis of MTC. Results: All 25 MTCs had at least one of the two most common RET SSVs versus 0.3% of 3,599 cancers with other diagnoses (p < 0.00001). The 11 cancers with non-MTC diagnoses that had the common RET SSVs were 4 neuroendocrine cancers, 4 non-small cell lung carcinomas, 2 non-MTC thyroid cancers, and 1 melanoma. All 25 MTCs analyzed had at least one of the two most common RET SSVs, including 4 with no identified mutational driver. Discussion: The identification of RET SSVs in all MTCs, but rarely in other cancer types, demonstrates that these RET SSVs distinguish MTCs from other cancer types. Future studies are needed to investigate whether these RET SSVs play a pathogenic role in MTC.

Enhancer-activated RET confers protection against oxidative stress to KMT2A-rearranged acute myeloid leukemia

Ectopic activation of rearranged during transfection (RET) has been reported to facilitate lineage differentiation and cell proliferation in different cytogenetic subtypes of acute myeloid leukemia (AML). Herein, we demonstrate that RET is significantly (p < 0.01) upregulated in AML subtypes containing rearrangements of the lysine methyltransferase 2A gene (KMT2A), commonly referred to as KMT2A-rearranged (KMT2A-r) AML. Integrating multi-epigenomics data, we show that the KMT2A-MLLT3 fusion induces the development of CCCTC-binding (CTCF)-guided de novo extrusion enhancer loop to upregulate RET expression in KMT2A-r AML. Based on the finding that RET expression is tightly correlated with the selective chromatin remodeler and mediator (MED) proteins, we used a small-molecule inhibitor having dual inhibition against RET and MED12-associated cyclin-dependent kinase 8 (CDK8) in KMT2A-r AML cells. Dual inhibition of RET and CDK8 restricted cell proliferation by producing multimodal oxidative stress responses in treated cells. Our data suggest that epigenetically enhanced RET protects KMT2A-r AML cells from oxidative stresses, which could be exploited as a potential therapeutic strategy.

Anaplastic and poorly differentiated thyroid carcinomas: genetic evidence of high-grade transformation from differentiated thyroid carcinoma

Anaplastic thyroid carcinoma (ATC) is the most advanced and aggressive thyroid cancer, and poorly differentiated thyroid carcinoma (PDTC) lacks anaplastic histology but has lost architectural and cytologic differentiation. Only a few studies have focused on the genetic relationship between the two advanced carcinomas and coexisting differentiated thyroid carcinomas (DTCs). In the present study, we investigated clinicopathologic features and genetic profiles in 57 ATC and PDTC samples, among which 33 cases had concomitant DTC components or DTC history. We performed immunohistochemistry for BRAF V600E, p53, and PD-L1 expression, Sanger sequencing for TERT promoter and RAS mutations, and fluorescence in situ hybridization for ALK and RET rearrangements. We found that ATCs and PDTCs shared similar gene alterations to their coexisting DTCs, and most DTCs were aggressive subtypes harboring frequent TERT promoter mutations. A significantly higher proportion of ATCs expressed p53 and PD-L1, and a lower proportion expressed PAX-8 and TTF-1, than the coexisting DTCs. Our findings provide more reliable evidence that ATCs and PDTCs are derived from DTCs.

RET 634 germline/gonadal mosaicism generating a second pathogenic amino acid change in multiple endocrine neoplasia type 2A

Genetic testing for germline RET pathogenic variants, which cause the Multiple Endocrine Neoplasia Type 2 (MEN2) syndrome, has become crucial in managing patients with medullary thyroid carcinoma (MTC). Classically, RET heterozygous missense pathogenic variants are transmitted in a Mendelian autosomal dominant pattern, of which germline/gonadal mosaicism has never been reported. We report the novel occurrence of a MEN2A patient's family in which the siblings inherited three different RET 634 genotypes: wild type (p.Cys634), p.Cys634Gly or p.Cys634Arg heterozygous pathogenic variants. We hypothesized that germline/gonadal mosaicism, derived from an inherited + early somatic mutation in the mother or a double de novo mutation during maternal embryogenesis, led to this rare event in the RET gene. Exome analysis of the proband's deceased mother's paraffin-embedded thyroid tissue confirmed the three nucleotides in the same 634 codon position. For the first time, we describe germline/gonadal mosaicism in RET, generating a second pathogenic amino acid change in the same codon causing MEN2A. Our finding shows that RET parental mosaicism, confirmed by somatic exome sequencing, might explain discrepant genotype cases in siblings with inherited cancers.

A Highly Sensitive XNA-Based RT-qPCR Assay for the Identification of ALK, RET, and ROS1 Fusions in Lung Cancer

Lung cancer is often triggered by genetic alterations that result in the expression of oncogenic tyrosine kinases. Specifically, ALK, RET, and ROS1 chimeric receptor tyrosine kinases are observed in approximately 5-7%, 1-2%, and 1-2% of NSCLC patients, respectively. The presence of these fusion genes determines the response to tyrosine kinase inhibitors. Thus, accurate detection of these gene fusions is essential in cancer research and precision oncology. To address this need, we have developed a multiplexed RT-qPCR assay using xeno nucleic acid (XNA) molecular clamping technology to detect lung cancer fusions. This assay can quantitatively detect thirteen ALK, seven ROS1, and seven RET gene fusions in FFPE samples. The sensitivity of the assay was established at a limit of detection of 50 copies of the synthetic template. Our assay has successfully identified all fusion transcripts using 50 ng of RNA from both reference FFPE samples and cell lines. After validation, a total of 77 lung cancer patient FFPE samples were tested, demonstrating the effectiveness of the XNA-based fusion gene assay with clinical samples. Importantly, this assay is adaptable to highly degraded RNA samples with low input amounts. Future steps involve expanding the testing to include a broader range of clinical samples as well as cell-free RNAs to further validate its applicability and reliability.

Generating Potential RET-Specific Inhibitors Using a Novel LSTM Encoder-Decoder Model

The receptor tyrosine kinase RET (rearranged during transfection) plays a vital role in various cell signaling pathways and is a critical factor in the development of the nervous system. Abnormal activation of the RET kinase can lead to several cancers, including thyroid cancer and non-small-cell lung cancer. However, most RET kinase inhibitors are multi-kinase inhibitors. Therefore, the development of an effective RET-specific inhibitor continues to present a significant challenge. To address this issue, we built a molecular generation model based on fragment-based drug design (FBDD) and a long short-term memory (LSTM) encoder-decoder structure to generate receptor-specific molecules with novel scaffolds. Remarkably, our model was trained with a molecular assembly accuracy of 98.4%. Leveraging the pre-trained model, we rapidly generated a RET-specific-candidate active-molecule library by transfer learning. Virtual screening based on our molecular generation model was performed, combined with molecular dynamics simulation and binding energy calculation, to discover specific RET inhibitors, and five novel molecules were selected. Further analyses indicated that two of these molecules have good binding affinities and synthesizability, exhibiting high selectivity. Overall, this investigation demonstrates the capacity of our model to generate novel receptor-specific molecules and provides a rapid method to discover potential drugs.

RET gene fusion and emergent Selpercatinib resistance in a calcitonin-rich neuroendocrine carcinoma: a case report

Metastatic lung neuroendocrine carcinomas provide diagnostic challenges in identifying the cell of origin. High level calcitonin expression is not pathognomonic for medullary thyroid cancer. Tumor mutation analysis may provide essential clues regarding tissue origin and treatment targets. Oncogenic RET gene fusions have been identified in non-small cell lung cancer and non-medullary thyroid cancers, whereas RET point mutations are the key genetic finding in both inherited and sporadic MTC. Patients who receive radiation for the treatment of other cancers have an increased risk of developing a second malignancy, including a neuroendocrine carcinoma. Herein, we present a case of calcitonin-rich neuroendocrine carcinoma emerging on a background of prior radiation and chemotherapy for the treatment of Hodgkin's disease. Identification of a RET gene rearrangement (KIF5B-RET) led to initial successful treatment with selpercatinib, with eventual resistance associated with an activating mutation involving the MEK1 protein (MAP2K1 p. E102-I103 del) that led to relapse and progression of the disease.

Kinase Fusions in Spitz Melanocytic Tumors: The Past, the Present, and the Future

In recent years, particular interest has developed in molecular biology applied to the field of dermatopathology, with a focus on nevi of the Spitz spectrum. From 2014 onwards, an increasing number of papers have been published to classify, stratify, and correctly frame molecular alterations, including kinase fusions. In this paper, we try to synthesize the knowledge gained in this area so far. In December 2023, we searched Medline and Scopus for case reports and case series, narrative and systematic reviews, meta-analyses, observational studies-either longitudinal or historical, case series, and case reports published in English in the last 15 years using the keywords spitzoid neoplasms, kinase fusions, ALK, ROS1, NTRK (1-2-3), MET, RET, MAP3K8, and RAF1. ALK-rearranged Spitz tumors and ROS-1-rearranged tumors are among the most studied and characterized entities in the literature, in an attempt (although not always successful) to correlate histopathological features with the probable molecular driver alteration. NTRK-, RET-, and MET-rearranged Spitz tumors present another studied and characterized entity, with several rearrangements described but as of yet incomplete information about their prognostic significance. Furthermore, although rarer, rearrangements of serine-threonine kinases such as BRAF, RAF1, and MAP3K8 have also been described, but more cases with more detailed information about possible histopathological alterations, mechanisms of etiopathogenesis, and also prognosis are needed. The knowledge of molecular drivers is of great interest in the field of melanocytic diagnostics, and it is important to consider that in addition to immunohistochemistry, molecular techniques such as FISH, PCR, and/or NGS are essential to confirm and classify the different patterns of mutation. Future studies with large case series and molecular sequencing techniques are needed to allow for a more complete and comprehensive understanding of the role of fusion kinases in the spitzoid tumor family.

Response to immune checkpoint inhibitor combination therapy in metastatic RET-mutated lung cancer from real-world retrospective data

BACKGROUND

The impact of immune checkpoint inhibitors (ICIs) based treatments on non-small cell lung cancers (NSCLCs) with RET fusions remains poorly understood.

METHODS

We screened patients with RET fusions at the First Affiliated Hospital of Zhengzhou University and included those who were treated with ICIs based regimens for further analysis. We evaluated clinical indicators including objective response rate (ORR), disease control rate (DCR), progression-free survival (PFS), and overall survival (OS).

RESULTS

A total of 232 patients with RET fusions were included in the study. Of these, 129 patients had their programmed death-ligand 1 (PDL1) expression levels tested, with 22 patients (17.8%) having a PDL1 level greater than or equal to 50%. Additionally, tumor mutational burden (TMB) status was evaluated in 35 patients, with the majority (30/35, 85.8%) having a TMB of less than 10 mutations per megabase. Out of the 38 patients treated with ICI based regimens, the median PFS was 5 months (95% confidence interval [CI]: 2.4-7.6 months) and the median OS was 19 months (95% CI: 9.7-28.3 months) at the time of data analysis. Stratification based on treatment lines did not show any significant differences in OS (18 vs. 19 months, p = 0.63) and PFS (6 vs. 5 months, p = 0.86). The ORR for patients treated with ICIs was 26.3%. Furthermore, no significant differences were found for PFS (p = 0.27) and OS (p = 0.75) between patients with positive and negative PDL1 expression. Additionally, there was no significant difference in PD-L1 levels (p = 0.10) between patients who achieved objective response and those who did not.

CONCLUSIONS

Patients with RET fusion positive NSCLCs may not benefit from ICI based regimens and therefore should not be treated with ICIs in clinical practice.

Association of the Genomic Profile of Medullary Thyroid Carcinoma with Tumor Characteristics and Clinical Outcomes in an International Multicenter Study

Purpose: The prognostic importance of RET and RAS mutations and their relationship to clinicopathologic parameters and outcomes in medullary thyroid carcinoma (MTC) need to be clarified. Experimental Design: A multicenter retrospective cohort study was performed utilizing data from 290 patients with MTC. The molecular profile was determined and associations were examined with clinicopathologic data and outcomes. Results: RET germ line mutations were detected in 40 patients (16.3%). Somatic RET and RAS mutations occurred in 135 (46.9%) and 57 (19.8%) patients, respectively. RETM918T was the most common somatic RET mutation (n = 75). RET somatic mutations were associated with male sex, larger tumor size, advanced American Joint Committee Cancer (AJCC) stage, vascular invasion, and high International Medullary Thyroid Carcinoma Grading System (IMTCGS) grade. When compared with other RET somatic mutations, RETM918T was associated with younger age, AJCC (eighth edition) IV, vascular invasion, extrathyroidal extension, and positive margins. RET somatic or germ line mutations were significantly associated with reduced distant metastasis-free survival on univariate analysis, but there were no significant independent associations on multivariable analysis, after adjusting for tumor grade and stage. There were no significant differences in outcomes between RET somatic and RET germ line mutations, or between RETM918T and other RET mutations. Other recurrent molecular alterations included TP53 (4.2%), ARID2 (2.9%), SETD2 (2.9%), KMT2A (2.9%), and KMT2C (2.9%). Among them, TP53 mutations were associated with decreased overall survival (OS) and disease-specific survival (DSS), independently of tumor grade and AJCC stage. Conclusions: RET somatic mutations were associated with high-grade, aggressive primary tumor characteristics, and decreased distant metastatic-free survival but this relationship was not significant after accounting for tumor grade and disease stage. RETM918T was associated with aggressive primary tumors but was not independently associated with clinical outcomes. TP53 mutation may represent an adverse molecular event associated with decreased OS and DSS in MTC, but its prognostic value needs to be confirmed in future studies.

The frequency of mutations in advanced thyroid cancer in Japan: a single-center study

We analyzed the outcomes of genetic testing to study the frequency of mutations in advanced thyroid cancer in Japan. Patients (n = 96) with unresectable or metastatic thyroid carcinoma were included for retrospective chart review. Results of gene panel testing, which was performed between May 2020 and April 2023, were analyzed. The median age of the patients was 73.5 years (range, 17-88); 59 were women, and 39 were men. Overall, 17 patients had anaplastic thyroid carcinoma (ATC), 68 had papillary thyroid carcinoma (PTC), 7 had follicular thyroid carcinoma, and 6 had poorly differentiated thyroid carcinoma (PDTC). Of the 81 patients with differentiated thyroid carcinoma (DTC) and PDTC, 88.9% were radioactive iodine-refractory, and 32.7% of all cases had previously been treated with multiple kinase inhibitors. Of ATC cases, 52.9% had BRAF mutations, and 5.9% had RET fusion. Of PTC cases, 83.1% had BRAF mutations, 9.2% had RET fusion, and 1.5% had NTRK fusion. One case each of ATC and PTC had a tumor mutation burden of ≥10. ATC cases had a significantly higher prevalence of TP53 alterations than the other cases (82.3% vs. 11.8%), whereas the frequencies of TERT promoter mutations were 88.2% in ATC cases and 64.7% in the other cases, albeit without a significant difference. In conclusion, 58.8% of ATC, 93.8% of PTC, and 42.9% of PDTC had genetic alterations linked to therapeutic agents. Active gene panel testing is required to increase treatment options.

Is Immunotherapy Beneficial in Patients with Oncogene-Addicted Non-Small Cell Lung Cancers? A Narrative Review

Over the past 20 years, there has been a paradigm shift in the care of patients with non-small cell lung cancer (NSCLC), who now have a range of systemic treatment options including targeted therapy, chemotherapy, immunotherapy (ICI), and antibody-drug conjugates (ADCs). A proportion of these cancers have single identifiable alterations in oncogenes that drive their proliferation and cancer progression, known as "oncogene-addiction". These "driver alterations" are identified in approximately two thirds of patients with lung adenocarcinomas, via next generation sequencing or other orthogonal tests. It was noted in the early clinical development of ICIs that patients with oncogene-addicted NSCLC may have differential responses to ICI. The toxicity signal for patients with oncogene-addicted NSCLC when treated with ICIs also seemed to differ depending on the alteration present and the specific targeted agent used. Developing a greater understanding of the underlying reasons for these clinical observations has become an important area of research in NSCLC. In this review, we analyze the efficacy and safety of ICI according to specific mutations, and consider possible future directions to mitigate safety concerns and improve the outcomes for patients with oncogene-addicted NSCLC.

High incidence of EDNRB gene mutation in seven southern Chinese familial cases with Hirschsprung's disease

PURPOSE

Hirschsprung's disease (HSCR) is the leading cause of neonatal functional intestinal obstruction, which has been identified in many familial cases. HSCR, a multifactorial disorder of enteric nervous system (ENS) development, is associated with at least 24 genes and seven chromosomal loci, with RET and EDNRB as its major genes. We present a genetic investigation of familial HSCR to clarify the genotype-phenotype relationship.

METHODS

We performed whole exome sequencing (WES) on Illumina HiSeq X Ten platform to investigate genetic backgrounds of core family members, and identified the possibly harmful mutation genes. Mutation carriers and pedigree relatives were validated by Sanger sequencing for evaluating the gene penetrance.

RESULTS

Four familial cases showed potential disease-relative variants in EDNRB and RET gene, accounting for all detection rate of 57.1%. Three familial cases exhibited strong pathogenic variants as frameshift or missense mutations in EDNRB gene. A novel c.367delinsTT mutation of EDNRB was identified in one family member. The other two EDNRB mutations, c.553G>A in family 2 and c.877delinsTT in family 5, have been reported in previous literatures. The penetrance of EDNRB variants was 33-50% according mutation carries. In family 6, the RET c.1858T>C (C620R) point mutation has previously been reported to cause HSCR, with 28.5% penetrance.

CONCLUSION

We identified a novel EDNRB (deleted C and inserted TT) mutation in this study using WES. Heterozygote variations in EDNRB gene were significantly enriched in three families and RET mutations were identified in one family. EDNRB variants showed an overall higher incidence and penetrance than RET in southern Chinese families cases.

Comprehensive molecular analysis identifies RET alterations association with response of ICIs in multi-immunotherapy cohorts

BACKGROUND

The RET gene, which is frequently mutated across many types of cancer, has been proven to be critically involved in tumorigenesis and tumour development; however, its prediction of the therapeutic efficacy of immune checkpoint inhibitor (ICI) therapy remains to be elucidated. The present research aims to investigate the association between RET mutations and the efficiency of ICI therapy.

METHOD

We analysed the role of RET mutations in predicting the prognosis of patients receiving ICIs therapy in the discovery cohort and validated it in the validation cohort. Then, multi-omics data from TCGA pan-cancer cohort was employed to propose the association between RET mutations and tumour inflamed anti-tumour immune response and tumour antigenicity.

RESULTS

Our study revealed that among 606 cases and across five types of cancer, RET mutation was associated with better clinical outcomes for ICIs therapy, including elevated response rate, longer progression-free survival PFS, and longer overall survival OS. Multivariate analysis showed that RET mutation could independently predict the prognosis of patients treated with ICIs, after adjusting cancer types. The predictive value of RET status for the OS of patients treated with ICIs immunotherapy was further validated in the validation cohort (n = 1,409). Subgroup analysis suggested that only the monotherapy group showed significant differences in OS(P < 0.05) and PFS(P < 0.05) between RET-wildtype tumours and RET-mutant tumours. Multi-omics data analysis revealed potential anti-tumour immunity mechanisms of RET mutations, suggesting that RET-mutant tumours have enhanced immunogenicity, higher expression of immune checkpoints and chemokines, and higher immune cell infiltration than those observed in RET-wildtype tumours; thus, potentially indicating a more favourable response to immunotherapy.

CONCLUSIONS

RET mutation may be a predictive biomarker of enhanced response to ICIs therapy. Extensive investigation of the underlying molecular mechanisms and prospective studies are needed in the future.

Functional role of glial-derived neurotrophic factor in a mixed allergen murine model of asthma

Our previous study showed that glial-derived neurotrophic factor (GDNF) expression is upregulated in asthmatic human lungs, and GDNF regulates calcium responses through its receptor GDNF family receptor α1 (GFRα1) and RET receptor in human airway smooth muscle (ASM) cells. In this study, we tested the hypothesis that airway GDNF contributes to airway hyperreactivity (AHR) and remodeling using a mixed allergen mouse model. Adult C57BL/6J mice were intranasally exposed to mixed allergens (ovalbumin, Aspergillus, Alternaria, house dust mite) over 4 wk with concurrent exposure to recombinant GDNF, or extracellular GDNF chelator GFRα1-Fc. Airway resistance and compliance to methacholine were assessed using FlexiVent. Lung expression of GDNF, GFRα1, RET, collagen, and fibronectin was examined by RT-PCR and histology staining. Allergen exposure increased GDNF expression in bronchial airways including ASM and epithelium. Laser capture microdissection of the ASM layer showed increased mRNA for GDNF, GFRα1, and RET in allergen-treated mice. Allergen exposure increased protein expression of GDNF and RET, but not GFRα1, in ASM. Intranasal administration of GDNF enhanced baseline responses to methacholine but did not consistently potentiate allergen effects. GDNF also induced airway thickening, and collagen deposition in bronchial airways. Chelation of GDNF by GFRα1-Fc attenuated allergen-induced AHR and particularly remodeling. These data suggest that locally produced GDNF, potentially derived from epithelium and/or ASM, contributes to AHR and remodeling relevant to asthma.NEW & NOTEWORTHY Local production of growth factors within the airway with autocrine/paracrine effects can promote features of asthma. Here, we show that glial-derived neurotrophic factor (GDNF) is a procontractile and proremodeling factor that contributes to allergen-induced airway hyperreactivity and tissue remodeling in a mouse model of asthma. Blocking GDNF signaling attenuates allergen-induced airway hyperreactivity and remodeling, suggesting a novel approach to alleviating structural and functional changes in the asthmatic airway.

Clinical, Morphological and Molecular Features of Spitz tumors

Spitz tumors represent a heterogeneous group of challenging melanocytic neoplasms, displaying a range of biological behaviors, spanning from benign lesions, Spitz nevi (SN) to Spitz melanomas (SM), with intermediate lesions in between known as atypical Spitz tumors (AST). They are histologically characterized by large epithelioid and/or spindled melanocytes arranged in fascicles or nests, often associated with characteristic epidermal hyperplasia and fibrovascular stromal changes. In the last decade, the detection of mutually exclusive structural rearrangements involving receptor tyrosine kinases ROS1, ALK, NTRK1, NTRK2, NTRK3, RET, MET, serine threonine kinases BRAF and MAP3K8, or HRAS mutation, led to a clinical, morphological and molecular based classification of Spitz tumors. The recognition of some reproducible histological features can help dermatopathologist in assessing these lesions and can provide clues to predict the underlying molecular driver. In this review, we will focus on clinical and morphological findings in molecular Spitz tumor subgroups.

Kinase fusion positive intra-osseous spindle cell tumors: A series of eight cases with review of the literature

Mesenchymal spindle cell tumors with kinase fusions, often presenting in superficial or deep soft tissue locations, may rarely occur in bone. Herein, we describe the clinicopathologic and molecular data of eight bone tumors characterized by various kinase fusions from our files and incorporate the findings with the previously reported seven cases, mainly as single case reports. In the current series all but one of the patients were young children or teenagers, with an age range from newborn to 59 years (mean 19 years). Most tumors (n = 5) presented in the head and neck area (skull base, mastoid, maxilla, and mandible), and remaining three in the tibia, pelvic bone, and chest wall. The fusions included NTRK1 (n = 3), RET (n = 2), NTRK3 (n = 2), and BRAF (n = 1). In the combined series (n = 15), most tumors (73%) occurred in children and young adults (<30 years) and showed a predilection for jaw and skull bones (40%), followed by long and small tubular bones (33%). The fusions spanned a large spectrum of kinase genes, including in descending order NTRK3 (n = 6), NTRK1 (n = 4), RET (n = 2), BRAF (n = 2), and RAF1 (n = 1). All fusions confirmed by targeted RNA sequencing were in-frame and retained the kinase domain within the fusion oncoprotein. Similar to the soft tissue counterparts, most NTRK3-positive bone tumors in this series showed high-grade morphology (5/6), whereas the majority of NTRK1 tumors were low-grade (3/4). Notably, all four tumors presenting in the elderly were high-grade spindle cell sarcomas, with adult fibrosarcoma (FS)-like, malignant peripheral nerve sheath tumor (MPNST)-like and MPNST phenotypes. Overall, 10 tumors had high-grade morphology, ranging from infantile and adult-types FS, MPNST-like, and MPNST, whereas five showed benign/low-grade histology (MPNST-like and myxoma-like). Immunohistochemically (IHC), S100 and CD34 positivity was noted in 57% and 50%, respectively, while co-expression of S100 and CD34 in 43% of cases. One-third of tumors (4 high grade and the myxoma-like) were negative for both S100 and CD34. IHC for Pan-TRK was positive in all eight NTRK-fusion positive tumors tested and negative in two tumors with other kinase fusions. Clinical follow-up was too limited to allow general conclusions.

Branchioma: immunohistochemical and molecular genetic study of 23 cases highlighting frequent loss of retinoblastoma 1 immunoexpression

Branchioma is an uncommon benign neoplasm with an adult male predominance, typically occurring in the lower neck region. Different names have been used for this entity in the past (ectopic hamartomatous thymoma, branchial anlage mixed tumor, thymic anlage tumor, biphenotypic branchioma), but currently, the term branchioma has been widely accepted. Branchioma is composed of endodermal and mesodermal lineage derivatives, in particular epithelial islands, spindle cells, and mature adipose tissue without preexistent thymic tissue or evidence of thymic differentiation. Twenty-three branchiomas were evaluated morphologically. Eighteen cases with sufficient tissue were assessed by immunohistochemistry, next-generation sequencing (NGS) using the Illumina Oncology TS500 panel, and fluorescence in situ hybridization (FISH) using an RB1 dual-color probe. All cases showed a biphasic morphology of epithelial and spindle cells with intermingled fatty tissue. Carcinoma arising in branchioma was detected in three cases. The neoplastic cells showed strong AE1/3 immunolabeling (100%), while the spindle cells expressed CD34, p63, and SMA (100%); AR was detected in 40-100% of nuclei (mean, 47%) in 14 cases. Rb1 showed nuclear loss in ≥ 95% of neoplastic cells in 16 cases (89%), while two cases revealed retained expression in 10-20% of tumor cell nuclei. NGS revealed a variable spectrum of likely pathogenic variants (n = 5) or variants of unknown clinical significance (n = 6). Loss of Rb1 was detected by FISH in two cases. Recent developments support branchioma as a true neoplasm, most likely derived from the rudimental embryological structures of endoderm and mesoderm. Frequent Rb1 loss by immunohistochemistry and heterozygous deletion by FISH is a real pitfall and potential confusion with other Rb1-deficient head and neck neoplasms (i.e., spindle cell lipoma), especially in small biopsy specimens.

Impact of the overexpression of the tyrosine kinase receptor RET in the hematopoietic potential of induced pluripotent stem cells (iPSCs)

INTRODUCTION

Previous studies have suggested that the tyrosine kinase receptor RET plays a significant role in the hematopoietic potential in mice and could also be used to expand cord-blood derived hematopoietic stem cells (HSCs). The role of RET in human iPSC-derived hematopoiesis has not been tested so far.

METHODS

To test the implication of RET on the hematopoietic potential of iPSCs, we activated its pathway with the lentiviral overexpression of RETWT or RETC634Y mutation in normal iPSCs. An iPSC derived from a patient harboring the RETC634Y mutation (iRETC634Y) and its CRISPR-corrected isogenic control iPSC (iRETCTRL) were also used. The hematopoietic potential was tested using 2D cultures and evaluated regarding the phenotype and the clonogenic potential of generated cells.

RESULTS

Hematopoietic differentiation from iPSCs with RET overexpression (WT or C634Y) led to a significant reduction in the number and in the clonogenic potential of primitive hematopoietic cells (CD34+/CD38-/CD49f+) as compared to control iPSCs. Similarly, the hematopoietic potential of iRETC634Y was reduced as compared to iRETCTRL. Transcriptomic analyses revealed a specific activated expression profile for iRETC634Y compared to its control with evidence of overexpression of genes which are part of the MAPK network with negative hematopoietic regulator activities.

CONCLUSION

RET activation in iPSCs is associated with an inhibitory activity in iPSC-derived hematopoiesis, potentially related to MAPK activation.

Modeling RET-Rearranged Non-Small Cell Lung Cancer (NSCLC): Generation of Lung Progenitor Cells (LPCs) from Patient-Derived Induced Pluripotent Stem Cells (iPSCs)

REarranged during Transfection (RET) oncogenic rearrangements can occur in 1-2% of lung adenocarcinomas. While RET-driven NSCLC models have been developed using various approaches, no model based on patient-derived induced pluripotent stem cells (iPSCs) has yet been described. Patient-derived iPSCs hold great promise for disease modeling and drug screening. However, generating iPSCs with specific oncogenic drivers, like RET rearrangements, presents challenges due to reprogramming efficiency and genotypic variability within tumors. To address this issue, we aimed to generate lung progenitor cells (LPCs) from patient-derived iPSCs carrying the mutation RETC634Y, commonly associated with medullary thyroid carcinoma. Additionally, we established a RETC634Y knock-in iPSC model to validate the effect of this oncogenic mutation during LPC differentiation. We successfully generated LPCs from RETC634Y iPSCs using a 16-day protocol and detected an overexpression of cancer-associated markers as compared to control iPSCs. Transcriptomic analysis revealed a distinct signature of NSCLC tumor repression, suggesting a lung multilineage lung dedifferentiation, along with an upregulated signature associated with RETC634Y mutation, potentially linked to poor NSCLC prognosis. These findings were validated using the RETC634Y knock-in iPSC model, highlighting key cancerous targets such as PROM2 and C1QTNF6, known to be associated with poor prognostic outcomes. Furthermore, the LPCs derived from RETC634Y iPSCs exhibited a positive response to the RET inhibitor pralsetinib, evidenced by the downregulation of the cancer markers. This study provides a novel patient-derived off-the-shelf iPSC model of RET-driven NSCLC, paving the way for exploring the molecular mechanisms involved in RET-driven NSCLC to study disease progression and to uncover potential therapeutic targets.

Addition of Trastuzumab Deruxtecan to Selpercatinib in a Patient With RET Fusion-Driven NSCLC and an Acquired HER2 Amplification: Case Report

Despite the high activity of selective RET inhibitors in RET-driven NSCLC, resistance eventually develops and there is unmet need to better define therapeutic options for patients. This is a case of a patient initially thought to have no targetable alterations, then found to have a RET fusion, and subsequently HER2 amplification on three distinct biopsies. She was treated initially with chemotherapy and immune therapy, then switched to selpercatinib, and eventually had fam-trastuzumab deruxtecan added to selpercatinib. She also developed neuroendocrine differentiation at time of progression in the context of a p53 mutation, which is a known factor that can lead to small cell transformation. This patient's case highlights the need for comprehensive molecular testing at both diagnosis and progression, as unexpected resistance mechanisms may be identified particularly for patients with uncommon driver mutations.

A Detailed Histologic and Molecular Assessment of the Diffuse Sclerosing Variant of Papillary Thyroid Carcinoma

Diffuse sclerosing variant papillary thyroid carcinoma (DS-PTC) is characterized clinically by a predilection for children and young adults, bulky neck nodes, and pulmonary metastases. Previous studies have suggested infrequent BRAFV600E mutation but common RET gene rearrangements. Using strict criteria, we studied 43 DS-PTCs (1.9% of unselected PTCs in our unit). Seventy-nine percent harbored pathogenic gene rearrangements involving RET, NTRK3, NTRK1, ALK, or BRAF; with the remainder driven by BRAFV600E mutations. All 10 pediatric cases were all gene rearranged (P = .02). Compared with BRAFV600E-mutated tumors, gene rearrangement was characterized by psammoma bodies involving the entire lobe (P = .038), follicular predominant or mixed follicular architecture (P = .003), pulmonary metastases (24% vs none, P = .04), and absent classical, so-called "BRAF-like" atypia (P = .014). There was no correlation between the presence of gene rearrangement and recurrence-free survival. Features associated with persistent/recurrent disease included pediatric population (P = .030), gene-rearranged tumors (P = .020), microscopic extrathyroidal extension (P = .009), metastases at presentation (P = .007), and stage II disease (P = .015). We conclude that DS-PTC represents 1.9% of papillary thyroid carcinomas and that actionable gene rearrangements are extremely common in DS-PTC. DS-PTC can be divided into 2 distinct molecular subtypes and all BRAFV600E-negative tumors (1.5% of papillary thyroid carcinomas) are driven by potentially actionable oncogenic fusions.

RET fusion genes in pediatric and adult thyroid carcinomas: cohort characteristics and prognosis

Thyroid cancer is associated with a broad range of different mutations, including RET (rearranged during transfection) fusion genes. The importance of characterizing RET fusion-positive tumors has recently increased due to the possibility of targeted treatment. The aim of this study was to identify RET fusion-positive thyroid tumors, correlate them with clinicopathological features, compare them with other mutated carcinomas, and evaluate long-term follow-up of patients. The cohort consisted of 1564 different thyroid tissue samples (including 1164 thyroid carcinoma samples) from pediatric and adult patients. Samples were analyzed for known driver mutations occurring in thyroid cancer. Negative samples were subjected to extensive RET fusion gene analyses using next-generation sequencing and real-time PCR. RET fusion genes were not detected in any low-risk neoplasm or benign thyroid tissue and were detected only in papillary thyroid carcinomas (PTCs), in 113/993 (11.4%) patients, three times more frequently in pediatric and adolescent patients (29.8%) than in adult patients (8.7%). A total of 20 types of RET fusions were identified. RET fusion-positive carcinomas were associated with aggressive tumor behavior, including high rates of lymph node (75.2%) and distant metastases (18.6%), significantly higher than in NTRK fusion, BRAF V600E and RAS-positive carcinomas. Local and distant metastases were also frequently found in patients with microcarcinomas positive for the RET fusions. 'True recurrences' occurred rarely (2.4%) and only in adult patients. The 2-, 5-, 10-year disease-specific survival rates were 99%, 96%, and 95%, respectively. RET fusion-positive carcinomas were associated with high invasiveness and metastatic activity, but probably due to intensive treatment with low patient mortality.

Familial Clinical Heterogeneity of Medullary Thyroid Cancer with Germline RET S891A Protooncogene Mutation: 7-Year Follow-up with Successful Sorafenib Treatment

Hereditary forms of Medullary thyroid carcinoma (MTC) are rare. Different phenotypes with the same mutation may be due to differences in the timing of RET activation steps, additional mutations in other regions of the gene, or the co-occurrence of germline and somatic mutations, which is an infrequent possibility. Here, we aim to present the different features and difficulties in the follow-up of three family members with the same germline mutation. A 4-year-old male patient with respiratory distress was diagnosed with MTC and found to have a heterozygous germline mutation C.2671T>G(S891A) in the RET gene (classified as intermediate risk according to ATA). As the tumor was inoperable, treatment with a tyrosine kinase inhibitor (sorafenib) was initiated. Sorafenib has prevented tumor progression for seven years. Whole exome sequencing (WES) did not identify additional mutations. Segregation analysis showed the same mutation in the asymptomatic mother and sister. In our case, thyroid tissues were examined for somatic mutations, and SDHA c.1223C>T (p.S408L) was found. The clinical presentation of rare mutations such as RET p.S891A differed among family members carrying the same germline mutation. Our index case's more severe clinical presentation may be due to an additional somatic mutation. Sorafenib treatment can be an option for advanced MTC and may prevent disease progression.

Pralsetinib-associated pneumonia in RET fusion-positive non-small cell lung cancer

OBJECTIVE

Oncogenic alternation in RET is one of the important targets of non-small cell lung cancer (NSCLC). Pralsetinib has shown great efficacy in RET fusion-positive NSCLC, but a series of adverse reactions will inevitably occur in the meantime. We aimed to explore the clinical characteristics of patients with pneumonia and recognition it in early stage, so patients could longer benefit from pralsetinib.

METHODS

This is a multicenter, retrospective study. RET fusion-positive advanced NSCLC patients who developed pneumonia during pralsetinib treatment from January 2020 to December 2022 were included. Clinical data, time to onset of pneumonia, methods of pneumonia diagnosis, treatment with pneumonia, prognosis of pneumonia, and the effect of pneumonia on the efficacy of pralsetinib.

RESULTS

A total of 8 patients with pneumonia were included in the study, most of which were non-smoking female patients and the main fusion gene was KIF5B (87.5%), which was consistent with the general characteristics of RET fusion population. The median occurrence time of pralsetinib-associated pneumonia was 2.15 (range 1.1-6.63) months. All patients were infected by opportunistic pathogens, and the most common pathogen was human herpesviruses and pneumospora yerbii. Fever was always the first symptom, and timely anti-infective treatment including antibiotics, antiviral drugs, and antifungal drugs was effective. Until February 28, 2023, the median follow-up time was 18.7 months, the mean PFS of patients was 17.4 months, and the median PFS was not reached. Fortunately, patients who restarted pralsetinib after infection control continued to benefit.

CONCLUSIONS

Opportunistic infection may be a unique adverse effect of pralsetinib. During the treatment of pralsetinib, we should be vigilant about the occurrence of pneumonia and achieve early recognition and timely treatment.

Caution on the Use of 68Ga-DOTATATE for the Diagnosis of Pheochromocytoma: A Report of 2 Cases

Pheochromocytomas are intra-adrenal sympathetic neuroendocrine tumors that arise from chromaffin cells. Paragangliomas similarly arise from chromaffin cells, although at extra-adrenal sites such as sympathetic paraganglia in the abdomen/thorax, or parasympathetic paraganglia in the head/neck. Collectively, pheochromocytomas and paragangliomas are important to diagnose and resect because they may secrete harmful levels of catecholamines, have mass effects, hemorrhage, and/or metastasize. Anatomic imaging of pheochromocytomas is usually completed with computed tomography or magnetic resonance imaging; however, functional imaging may be used to provide additional localization, staging, and/or biologic information. Accordingly, selection of the proper functional imaging modality can be critical to developing the optimal therapeutic strategy. 68Gallium- and 64Copper-1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid (DOTA)-octreotate positron emission tomography computed tomography (68Ga- and 64Cu-DOTATATE) are widely used in evaluating pheochromocytomas and paragangliomas, although data regarding the sensitivity for diagnosing pheochromocytoma are limited. We report 2 cases of pheochromocytoma that showed nondiagnostic 68Ga-DOTATATE uptake but were subsequently visualized using alternative functional imaging modalities. Additionally, we provide a review of the literature to highlight the underappreciated limitations of functional adrenal imaging with somatostatin-based compounds.

Lenvatinib and selpercatinib successfully treated RET fusion gene-positive papillary thyroid carcinoma cardiac metastases: a case report

Background

Cardiac metastasis from thyroid cancer is rare and has an extremely poor prognosis. Although some patients who undergo heart surgery survive, the therapeutic effectiveness of systemic therapy is limited.

Case Description

A 53-year-old woman with a history of papillary thyroid carcinoma (PTC) presented with cough and right chest discomfort. She underwent total thyroidectomy, followed by three rounds of radioactive iodine therapy, to treat pulmonary metastasis. Metastases to the lung, chest wall, liver, heart, and lymph nodes were observed on computed tomography. Core needle biopsy of the tumor in the right chest wall revealed the recurrence of PTC. Cardiac metastasis was discovered by echocardiography and cardiac magnetic resonance imaging, and blood test indicated a thyroglobulin level of 851 ng/mL. Based on the presence of cardiac metastasis and strong clinical symptoms, the condition was assumed to be fatal, and lenvatinib was started right away. Three weeks after starting lenvatinib, every metastatic lesion shrank. Once the ERC1-RET fusion gene was identified, we switched to selpercatinib therapy. Ten weeks after starting selpercatinib, every tumor shrank and blood thyroglobulin dropped to 68.1 ng/mL. Initial symptoms such as cough and right chest pain improved. Lenvatinib- and selpercatinib-related adverse effects can be managed with supportive care.

Conclusions

To the best of our knowledge, this is the first case of successful systemic therapy for cardiac metastasis from PTC. Conventionally, cardiac surgery is the main treatment for cardiac metastasis, but now systemic therapy is also an important alternative.

Molecular Basis and Natural History of Medullary Thyroid Cancer: It is (Almost) All in the RET

Medullary thyroid cancer (MTC) is a rare disease, which can be either sporadic (roughly 75% of cases) or genetically determined (multiple endocrine neoplasia type 2, due to REarranged during Transfection RET germline mutations, 25% of cases). Interestingly, RET pathogenic variants (mainly M918T) have also been reported in aggressive forms of sporadic MTC, suggesting the importance of RET signalling pathways in the pathogenesis of MTC. The initial theory of RET codon-related MTC aggressiveness has been recently questioned by studies suggesting that this would only define the age at disease onset rather than the aggressiveness of MTC. Other factors might however impact the natural history of the disease, such as RET polymorphisms, epigenetic factors, environmental factors, MET (mesenchymal-epithelial transition) alterations, or even other genetic alterations such as RAS family (HRAS, KRAS, NRAS) genetic alterations. This review will detail the molecular bases of MTC, focusing on RET pathways, and the potential mechanisms that explain the phenotypic intra- and interfamilial heterogeneity.

Targeting the RET tyrosine kinase in neuroblastoma: A review and application of a novel selective drug design strategy

The RET (REarranged during Transfection) gene, which encodes for a transmembrane receptor tyrosine kinase, is an established oncogene associated with the etiology and progression of multiple types of cancer. Oncogenic RET mutations and rearrangements resulting in gene fusions have been identified in many adult cancers, including medullary and papillary thyroid cancers, lung adenocarcinomas, colon and breast cancers, and many others. While genetic RET aberrations are much less common in pediatric solid tumors, increased RET expression has been shown to be associated with poor prognosis in children with solid tumors such as neuroblastoma, prompting an interest in RET inhibition as a form of therapy for these children. A number of kinase inhibitors currently in use for patients with cancer have RET inhibitory activity, but these inhibitors also display activity against other kinases, resulting in unwanted side effects and limiting their safety and efficacy. Recent efforts have been focused on developing more specific RET inhibitors, but due to high levels of conservation between kinase binding pockets, specificity remains a drug design challenge. Here, we review the background of RET as a potential therapeutic target in neuroblastoma tumors and the results of recent preclinical studies and clinical trials evaluating the safety and efficacy of RET inhibition in adults and children. We also present a novel approach to drug discovery leveraging the chemical phenomenon of atropisomerism to develop specific RET inhibitors and present preliminary data demonstrating the efficacy of a novel RET inhibitor against neuroblastoma tumor cells.

TMEM127 suppresses tumor development by promoting RET ubiquitination, positioning, and degradation

The TMEM127 gene encodes a transmembrane protein of poorly known function that is mutated in pheochromocytomas, neural crest-derived tumors of adrenomedullary cells. Here, we report that, at single-nucleus resolution, TMEM127-mutant tumors share precursor cells and transcription regulatory elements with pheochromocytomas carrying mutations of the tyrosine kinase receptor RET. Additionally, TMEM127-mutant pheochromocytomas, human cells, and mouse knockout models of TMEM127 accumulate RET and increase its signaling. TMEM127 contributes to RET cellular positioning, trafficking, and lysosome-mediated degradation. Mechanistically, TMEM127 binds to RET and recruits the NEDD4 E3 ubiquitin ligase for RET ubiquitination and degradation via TMEM127 C-terminal PxxY motifs. Lastly, increased cell proliferation and tumor burden after TMEM127 loss can be reversed by selective RET inhibitors in vitro and in vivo. Our results define TMEM127 as a component of the ubiquitin system and identify aberrant RET stabilization as a likely mechanism through which TMEM127 loss-of-function mutations cause pheochromocytoma.

Analysis of Acute and Chronic Methamphetamine Treatment in Mice on Gdnf System Expression Reveals a Potential Mechanism of Schizophrenia Susceptibility

The increase in presynaptic striatal dopamine is the main dopaminergic abnormality in schizophrenia (SCZ). SCZ is primarily treated by modulating the activity of monoamine systems, with a focus on dopamine and serotonin receptors. Glial cell line-derived neurotrophic factor (GDNF) is a strong dopaminergic factor, that recently was shown to correlate with SCZ in human CSF and in striatal tissue. A 2-3-fold increase in GDNF in the brain was sufficient to induce SCZ-like dopaminergic and behavioural changes in mice. Here, we analysed the effect of acute, chronic, and embryonic methamphetamine, a drug known to enhance the risk of psychosis, on Gdnf and its receptors, Gfra1 and Ret, as well as on monoamine metabolism-related gene expression in the mouse brain. We found that acute methamphetamine application increases Gdnf expression in the striatum and chronic methamphetamine decreases the striatal expression of GDNF receptors Gfra1 and Ret. Both chronic and acute methamphetamine treatment upregulated the expression of genes related to dopamine and serotonin metabolism in the striatum, prefrontal cortex, and substantia nigra. Our results suggest a potential mechanism as to how methamphetamine elicits individual psychosis risk in young adults-variation in initial striatal GDNF induction and subsequent GFRα1 and RET downregulation may determine individual susceptibility to psychosis. Our results may guide future experiments and precision medicine development for methamphetamine-induced psychosis using GDNF/GFRa1/RET antagonists.

ALK, ROS1, RET and NTRK1-3 Gene Fusions in Colorectal and Non-Colorectal Microsatellite-Unstable Cancers

This study aimed to conduct a comprehensive analysis of actionable gene rearrangements in tumors with microsatellite instability (MSI). The detection of translocations involved tests for 5'/3'-end expression imbalance, variant-specific PCR and RNA-based next generation sequencing (NGS). Gene fusions were detected in 58/471 (12.3%) colorectal carcinomas (CRCs), 4/69 (5.8%) gastric cancers (GCs) and 3/65 (4.6%) endometrial cancers (ECs) (ALK: 8; RET: 12; NTRK1: 24; NTRK2: 2; NTRK3: 19), while none of these alterations were observed in five cervical carcinomas (CCs), four pancreatic cancers (PanCs), three cholangiocarcinomas (ChCs) and two ovarian cancers (OCs). The highest frequency of gene rearrangements was seen in KRAS/NRAS/BRAF wild-type colorectal carcinomas (53/204 (26%)). Surprisingly, as many as 5/267 (1.9%) KRAS/NRAS/BRAF-mutated CRCs also carried tyrosine kinase fusions. Droplet digital PCR (ddPCR) analysis of the fraction of KRAS/NRAS/BRAF mutated gene copies in kinase-rearranged tumors indicated that there was simultaneous co-occurrence of two activating events in cancer cells, but not genetic mosaicism. CRC patients aged above 50 years had a strikingly higher frequency of translocations as compared to younger subjects (56/365 (15.3%) vs. 2/106 (1.9%), p = 0.002), and this difference was particularly pronounced for tumors with normal KRAS/NRAS/BRAF status (52/150 (34.7%) vs. 1/54 (1.9%), p = 0.001). There were no instances of MSI in 56 non-colorectal tumors carrying ALK, ROS1, RET or NTRK1 rearrangements. An analysis of tyrosine kinase gene translocations is particularly feasible in KRAS/NRAS/BRAF wild-type microsatellite-unstable CRCs, although other categories of tumors with MSI also demonstrate moderate occurrence of these events.

A Shift in Molecular Drivers of Papillary Thyroid Carcinoma Following the 2017 World Health Organization Classification: Characterization of 554 Consecutive Tumors With Emphasis on BRAF-Negative Cases

Most studies for comprehensive molecular profiling of papillary thyroid carcinoma (PTC) have been performed before the 2017 World Health Organization (WHO) classification, in which the diagnostic criteria of follicular variants of PTC have been modified and noninvasive follicular thyroid neoplasm with papillary-like nuclear features has been introduced. This study aims to investigate the shift in the incidence of BRAF V600E mutations in PTCs following the 2017 WHO classification and to further characterize the histologic subtypes and molecular drivers in BRAF-negative cases. The study cohort consisted of 554 consecutive PTCs larger than 0.5 cm between January 2019 and May 2022. Immunohistochemistry for BRAF VE1 was performed for all cases. Compared with a historical cohort of 509 PTCs from November 2013 to April 2018, the incidence of BRAF V600E mutations was significantly higher in the study cohort (86.8% vs 78.8%, P = .0006). Targeted RNA-based next-generation sequencing using a FusionPlex Pan Solid Tumor v2 panel (ArcherDX) was performed for BRAF-negative PTCs from the study cohort. Eight cribriform-morular thyroid carcinomas and 3 cases with suboptimal RNA quality were excluded from next-generation sequencing. A total of 62 BRAF-negative PTCs were successfully sequenced, including 19 classic follicular predominant PTCs, 16 classic PTCs, 14 infiltrative follicular PTCs, 7 encapsulated follicular PTCs, 3 diffuse sclerosing PTCs, 1 tall cell PTC, 1 solid PTC, and 1 diffuse follicular PTC. Among them, RET fusions were identified in 25 cases, NTRK3 fusions in 13 cases, BRAF fusions in 5 cases including a novel TNS1::BRAF fusion, NRAS Q61R mutations in 3 cases, KRAS Q61K mutations in 2 cases, NTRK1 fusions in 2 cases, an ALK fusion in 1 case, an FGFR1 fusion in 1 case, and an HRAS Q61R mutation in 1 case. No genetic variants, from our commercially employed assay, were detected in the remaining 9 cases. In summary, the incidence of BRAF V600E mutations in PTCs significantly increased from 78.8% to 86.8% in our post-2017 WHO classification cohort. RAS mutations accounted for only 1.1% of the cases. Driver gene fusions were identified in 8.5% of PTCs and were clinically relevant given the emerging targeted kinase inhibitor therapy. Of the 1.6% of cases for which no driver alteration was detected, the specificity of drivers tested and tumor classification require further investigation.

A Metastatic Pulmonary Sarcomatoid Carcinoma Patient Harboring KIF5B-RET Fusion Responds to First-Line Pralsetinib Treatment: A Case Report

Pulmonary sarcomatoid carcinoma (PSC) is a rare subtype of non-small cell lung cancer (NSCLC), accounting for about 1% of cases. These tumors are characterized by their high malignancy and frequent resistance to chemotherapy, resulting in a worse prognosis compared to other NSCLC subtypes. Currently, there is no established therapeutic strategy for PSC. Recent advancements in targeted therapies have led to the development of ret proto-oncogene (RET) inhibitors, such as selpercatinib and pralsetinib, which have been approved for the treatment of RET fusion-positive NSCLC patients. Despite their effectiveness in RET fusion-positive NSCLC is observed, the efficacy of these inhibitors in PSC remains unclear. In this context, we present a case of metastatic PSC harboring de novo KIF5B-RET fusion. The patient responded to first-line trametinib treatment. These findings suggest that RET inhibitors could be a potential treatment option for metastatic PSC patients with RET fusion-positive tumors.

Personalized Medicine in Medullary Thyroid Carcinoma: A Broad Review of Emerging Treatments

Medullary thyroid carcinoma (MTC) arises from parafollicular cells in the thyroid gland, and although rare, it represents an aggressive type of thyroid cancer. MTC is recognized for its low mutational burden, with point mutations in RET or RAS genes being the most common oncogenic events. MTC can be resistant to cytotoxic chemotherapy, and multitarget kinase inhibitors (MKIs) have been considered a treatment option. They act by inhibiting the activities of specific tyrosine kinase receptors involved in tumor growth and angiogenesis. Several tyrosine kinase inhibitors are approved in the treatment of advanced MTC, including vandetanib and cabozantinib. However, due to the significant number of adverse events, debatable efficiency and resistance, there is a need for novel RET-specific TKIs. Newer RET-specific TKIs are expected to overcome previous limitations and improve patient outcomes. Herein, we aim to review MTC signaling pathways, the most recent options for treatment and the applications for personalized medicine.

Small bowel edema and lymphocytic duodenitis as severe reversible gastrointestinal toxicity of selpercatinib in RET fusion-positive non-small cell lung cancer: a case report

Introduction

Rearranged during transfection (RET) gene rearrangements occur in 1%-2% of non-small cell lung cancer (NSCLC). Because of the results of the study LIBRETTO-001, selpercatinib has been approved as the first-line treatment for patients with RET fusion-positive advanced NSCLC. Selpercatinib demonstrated to be well tolerated. Despite this, gastrointestinal adverse events (AEs) are frequently reported, and no clinical-radiological and endoscopic features and their impact in terms of treatment discontinuations, interruptions, and dose reductions have been described so far.

Case report

A 37-year-old never-smoker woman was treated in our institution with selpercatinib for a RET fusion-positive NSCLC. After 9 months of treatment, the patient referred abdominal pain of grade (G) 2, associated with nausea of G2, bilious vomiting of G3, and weight loss of G1. At computed tomography scan, the presence of important bowel wall thickening, free ascitic fluid, mesenteric congestion, and stranding was detected. The patient underwent an anterograde enteroscopy extended to jejunum with detection of lymphocytic duodenitis with sub-mucosal edema. Selpercatinib treatment was temporary interrupted with complete resolution of the symptoms and then re-administered with dose reduction, without relapsed of the gastrointestinal toxicity after 120 days.

Conclusion

To our knowledge, this is the first case report of a patient with NSCLC treated with selpercatinib outside a clinical study who developed severe gastrointestinal toxicity characterized by small bowel edema and lymphocytic duodenitis, leading to treatment interruption and dose reduction. The gastrointestinal AE has been described by a radiological, endoscopic, and histopathological point of view. Further investigations are needed to better identify pathological mechanisms of gastrointestinal toxicity for an appropriate AE management.