RET-mediated modulation of tumor microenvironment and immune response in multiple endocrine neoplasia type 2 (MEN2)

Molecular genetics, therapeutics and RET inhibitor resistance for medullary thyroid carcinoma and future perspectives

Medullary thyroid carcinoma (MTC) is a rare type of thyroid malignancy that accounts for approximately 1-2% of all thyroid cancers (TCs). MTC include hereditary and sporadic cases, the former derived from a germline mutation of rearrangement during transfection (RET) proto-oncogene, whereas somatic RET mutations are frequently present in the latter. Surgery is the standard treatment for early stage MTC, and the 10-year survival rate of early MTC is over 80%. While for metastatic MTC, chemotherapy showing low response rate, and there was a lack of effective systemic therapies in the past. Due to the high risk (ca. 15-20%) of distant metastasis and limited systemic therapies, the 10-year survival rate of patients with advanced MTC was only 10-40% from the time of first metastasis. Over the past decade, targeted therapy for RET has developed rapidly, bringing hopes to patients with advanced and progressive MTC. Two multi-kinase inhibitors (MKIs) including Cabozantinib and Vandetanib have been shown to increase progression-free survival (PFS) for patients with metastatic MTC and have been approved as choices of first-line treatment. However, these MKIs have not prolonged overall survival (OS) and their utility is limited due to high rates of off-target toxicities. Recently, new generation TKIs, including Selpercatinib and Pralsetinib, have demonstrated highly selective efficacy against RET and more favorable side effect profiles, and gained approval as second-line treatment options. Despite the ongoing development of RET inhibitors, the management of advanced and progressive MTC remains challenging, drug resistance remains the main reason for treatment failure, and the mechanisms are still unclear. Besides, new promising therapeutic approaches, such as novel drug combinations and next generation RET inhibitors are under development. Herein, we overview the pathogenesis, molecular genetics and current management approaches of MTC, and focus on the recent advances of RET inhibitors, summarize the current situation and unmet needs of these RET inhibitors in MTC, and provide an overview of novel strategies for optimizing therapeutic effects.

Discovery of Pharmaceutical Composition for Prevention and Treatment in Patient-Derived Metastatic Medullary Thyroid Carcinoma Model

Medullary thyroid carcinoma (MTC) is a well-known neuroendocrine carcinoma, derived from C cells of the thyroid gland. Additionally, MTC is an uncommon aggressive carcinoma that metastasizes to lymph nodes, bones, lungs and liver. For MTC, the 10-year general survival ratio of patients with localized disease is about 95%, whereas that of patients with local phase disorder is around 75%. Only 20% of patients with distant metastasis to lung at diagnosis survive 10 years, which is notably lower than survival for well-differentiated thyroid carcinoma (WDTC). The management of MTC with distant metastasis to lung could be re-surgery or chemotherapy. In this research, we planned to assess the in vitro and in vivo combinational anticancer effect of a novel combination of low-dose cisplatin and sorafenib in patient-derived MTC. The patient-derived MTC cell lines YUMC-M1, M2, and M3 were isolated and treated with a combination of cisplatin and sorafenib or either agent alone. Cisplatin and sorafenib acted in combination to forward tumor restraint compared with each agent administered alone at a low dose. Therefore, a combination of cisplatin and sorafenib could be a new therapeutic approach for MTC.

Patients deriving long-term benefit from immune checkpoint inhibitors demonstrate conserved patterns of site-specific mutations

Immune checkpoint inhibitors (ICIs) have revolutionized cancer therapy and are now the preferred treatment for several tumor types. Though ICIs have shown remarkable efficacy in several cancer histologies, in many cases providing long-term disease control, not all patients will derive clinical benefit from such approaches. Given the lack of a reliable predictive biomarker for therapeutic responses to ICIs, we conducted a retrospective analysis of publicly available genomic data from a large pan-cancer cohort of patients receiving ICI-based immunotherapy. Consistent with previous results, patients in the combined cohort deriving a long-term survival benefit from ICIs were more likely to have a higher tumor mutational burden (TMB). However, this was not uniform across tumor-types, failing to predict for long-term survivorship in most non-melanoma cancers. Interestingly, long-term survivors in most cancers had conserved patterns of mutations affecting several genes. In melanoma, this included mutations affecting TET1 or PTPRD. In patients with colorectal cancer, mutations affecting TET1, RNF43, NCOA3, LATS1, NOTCH3, or CREBBP were also associated with improved prognosis, as were mutations affecting PTPRD, EPHA7, NTRK3, or ZFHX3 in non-small cell lung cancer, RNF43, LATS1, or CREBBP mutations in bladder cancer, and VHL mutations in renal cell carcinoma patients. Thus, this study identified several genes that may have utility as predictive biomarkers for therapeutic responses in patients receiving ICIs. As many have no known relationship to immunotherapy or ICIs, these genes warrant continued exploration, particularly for cancers in which established biomarkers such as PD-L1 expression or TMB have little predictive value.

Oncological drug discovery: AI meets structure-based computational research

The integration of machine learning and structure-based methods has proven valuable in the past as a way to prioritize targets and compounds in early drug discovery. In oncological research, these methods can be highly beneficial in addressing the diversity of neoplastic diseases portrayed by the different hallmarks of cancer. Here, we review six use case scenarios for integrated computational methods, namely driver prediction, computational mutagenesis, (off)-target prediction, binding site prediction, virtual screening, and allosteric modulation analysis. We address the heterogeneity of integration approaches and individual methods, while acknowledging their current limitations and highlighting their potential to bring drugs for personalized oncological therapies to the market faster.

Hallmarks of RET and Co-occuring Genomic Alterations in RET-aberrant Cancers

Activating receptor-tyrosine kinase rearranged during transfection (RET) mutations and fusions are potent drivers of oncogenesis. The recent FDA approvals of highly potent and selective RET inhibitors, selpercatinib and pralsetinib, has altered the therapeutic management of RET aberrant tumors. There is ample evidence of the role of RET signaling in certain cancers. RET aberrations as fusions or mutations occur in multiple cancers, however, there is considerable phenotypic diversity. There is emerging data on the lack of responsiveness of immunotherapy in RET-altered cancers. Herein, we review the registrational data from the selective RET-inhibitor trials, and comprehensively explore RET alterations in pan-cancer adult malignancies and their co-alterations. These co-occuring alterations may define the future of RET inhibition from specific selective targeting to customized combination therapies as data are rapidly emerging on both on-target and off-target acquired resistance mechanisms. Fascinatingly, oncogenic RET fusions have been reported to mediate resistance to EGFR inhibition and KRAS^G12C inhibition.

Immune Profiling of Medullary Thyroid Cancer-An Opportunity for Immunotherapy

Medullary thyroid cancer (MTC) is a rare malignancy that arises from calcitonin-producing C-cells. Curative treatment for patients with metastatic MTC is challenging. Identifying the mechanisms by which cancer cells inhibit the activity of immune cells provides an opportunity to develop new therapies that restore anticancer activity. Little is known about the immunological phenomena underlying MTC. Here, we examined the expression profile of 395 genes associated with MTC. The study included 51 patients diagnosed with MTC at a single center. Bioinformatical analysis revealed that CD276 expression in MTC cells was at least three-fold higher than that in normal tissue. The expression of CD276 showed a weak but statistically significant positive correlation with tumor diameter, but we did not find a significant association between CD276 expression and other histopathological clinical factors, or the response to initial therapy. A search of published data identified the monoclonal antibody (inhibitor) enoblituzumab as a potential drug for patients diagnosed with MTC overexpressing CD276.

Selective Antitumor Activity of Datelliptium toward Medullary Thyroid Carcinoma by Downregulating RET Transcriptional Activity

Simple Summary

Medullary thyroid carcinoma (MTC) is a rare aggressive type of thyroid cancer with a propensity for metastasizing to the lymph nodes, liver, bones, and lungs. Previous studies have demonstrated that activated REarranged during Transfection (RET) mutants are key regulators of invasive and metastatic behaviors in MTC. The present study aimed to evaluate the antiinvasive and antimetastatic potential of a novel RET transcription inhibitor, datelliptium, which stabilizes the RET G-quadruplex structures and suppresses RET oncogene transcription by examining its effects on epithelial-to-mesenchymal transition (EMT), cancer stem cells (CSCs), and MTC cell migration. Interestingly, the ablation of RET with datelliptium resulted in decreased EMT, spheroid formation, and MTC cell migration. In this study, we also demonstrated the in vivo antitumor activity in TT tumor-bearing mice with about 75% tumor growth inhibition.

Abstract

Medullary thyroid carcinoma (MTC) is a rare aggressive form of thyroid cancer with high rates of metastasis. Sporadic and hereditary MTC are strongly driven by somatic and germline mutations, respectively, in the transmembrane REarranged during Transfection (RET) proto-oncogene, which encodes a receptor tyrosine kinase. Our previous study identified datelliptium as a novel RET transcription inhibitor, which stabilizes the RET G-quadruplex structures and suppresses RET oncogene transcription. The present study aimed to elucidate the effect of datelliptium on the suppression of epithelial-to-mesenchymal transition (EMT) and metastasis-related behaviors of MTC cells, including cell migration and formation of cancer stem cells (CSCs). Our results demonstrated that datelliptium downregulated the expression of the mesenchymal markers, including N-cadherin, vimentin, slug, snail, and claudin-1. Compared to untreated cells, datelliptium significantly decreased the migration of TT cells in a dose-dependent manner in a wound healing assay. Additionally, datelliptium significantly reduced the size of preformed spheroids from TT cells over the time course. Finally, datelliptium inhibited approximately 75% of MTC xenograft growth with minimal systemic toxicity. In conclusion, datelliptium exerts its antitumor activity against MTC cells by reducing the EMT program, migratory ability, and self-renewal capacity of TT cells, thus preventing invasive and metastatic behavior of MTC.

Genomics and Epigenomics of Medullary Thyroid Carcinoma: From Sporadic Disease to Familial Manifestations

Our understanding of the genomics and epigenomics of medullary thyroid carcinoma (MTC) has advanced since the initial recognition of RET as a driver of MTC tumorigenesis in familial MTC. We now have insight into the frequency and prognostic significance of specific RET mutations in sporadic MTC. For example, the most common RET mutation in sporadic MTC is the RET Met918Thr mutation, the same mutation that underlies MEN2B and a poor prognosticator. This mutation is relatively infrequent in medullary thyroid microcarcinomas but is over-represented in advanced-stage disease. RAS mutations are detected in 70% of sporadic, RET wild-type MTC. Although next-generation and whole-exome sequencing studies have shown that tumors that are wild-type for RET and RAS mutations essentially lack other recurrent mutations, additional pathways and epigenetic alterations have been implicated in MTC tumorigenesis. Increased insight into the clinical course of patients with familial MTC with specific RET mutations has guided treatment recommendations for these patients. Finally, an understanding of the genomics has informed treatment for patients with advanced MTC. In this review, we will examine the genomics and epigenomics of sporadic and familial MTC, along with the prognostic significance of molecular alterations, management of patients with germline RET mutations, and treatment strategies for MTC patients.

Is there any place for immune-checkpoint inhibitors in the treatment algorithm of fusion-driven non-small cell lung cancer?-a literature review

The advent of immune-checkpoint inhibitors (ICIs) targeting the programmed death-1 (PD-1)/programmed death ligand-1 (PD-L1) axis, produced a paradigm change of the treatment algorithm for metastatic, non-oncogene addicted, non-small cell lung cancer (NSCLC). However, the majority of patients with oncogene-addicted disease have been excluded from the "immunotherapy revolution", thus the clinical efficacy of these agents in this subset of patients remains largely unknown. Although pre-clinical evidence provided a good rationale to pursue the investigation of ICI treatment in specific subgroups of oncogene-addicted NSCLC, current available evidence suggested that tumors harboring molecular alterations likely do not represent the best candidate to single agent ICI therapy. Furthermore, the prospect of further improving overall survival (OS) with the combination of tyrosine kinase inhibitors (TKIs) and ICIs led to unexpected poor results and safety issues in recent phase I trials exploring different therapeutic associations. Conversely, the combination of immunotherapy and chemotherapy is emerging as a potential effective strategy in specific subsets of NSCLC patients harboring oncogenic drivers. In this review we particularly focus on the subgroup of patients whose disease harbor oncogenic rearrangements, summarizing current evidence from preclinical and clinical studies and discussing their practical implications, in order to define the potential role of ICIs in the clinical management of fusion-driven NSCLC.

Updates in the advances of sporadic medullary thyroid carcinoma: from the molecules to the clinic

Medullary thyroid carcinoma (MTC) is a rare neuroendocrine malignancy that originates in parafollicular cells. It is well-known that a quarter of MTC are involved in hereditary multiple endocrine neoplasia type 2 syndromes, whereas most MTC are sporadic. Unlike the commonly encountered gastrointestinal or pulmonary neuroendocrine tumors, most sporadic MTCs have distinct genetic alterations featured by somatic changes of either Rearranged during Transfection (RET) or RAS point mutation. The increasing application of next-generation sequencing, whole-exome sequencing, and other molecular detection techniques enables us to understand MTC comprehensively concerning its detailed molecular changes and their clinical correlations. This article reviews the advances in genetic alterations and their prognostic impact in sporadic MTC among different populations and discusses the associated tumor immune microenvironments and the potential role of immunotherapy targeting PD-L1/PD-1 in treating MTC. Furthermore, the current multikinase inhibitor targeting therapy for sporadic MTC has been summarized here and its efficacy and drug toxicity are discussed. Updates in advance of the role of calcitonin/procalcitonin/calcitonin-related polypeptide alpha (CALCA) gene transcripts in diagnosing and handling MTC are also mentioned. The treatment of advanced MTC is still challenging and might require a combination of several modalities.

RET S409Y Germline Mutation and Associated Medullary Thyroid Carcinoma

Background: Inherited medullary thyroid carcinoma (MTC) is primarily caused by RET mutations that are commonly localized in exons 5, 8, 10, 11, and 13-16. In this study, we report pedigrees for individuals with MTC that harbor a germline S409Y variant within exon 6 of the RET proto-oncogene. Methods: Targeted sequencing was used to diagnose four apparently sporadic MTC index cases carrying the germline RET S409Y (c.1226 C>A) variant. Subsequently, 27 relatives of these individuals underwent clinical and genetic assessments and/or thyroid surgery. Furthermore, in silico analyses and in vitro assays were performed to predict or verify the potential oncogenic activity of the S409Y variant. Results: Overall, 15 of 31 participants were found to carry the RET S409Y variant. Of these, 6 presented with isolated MTC (mean age 50.2 years; range 41-75 years), of which 3 presented with neck lymph node metastases and 2 presented with distant liver or lung metastases. Among the remaining 9 carriers, 3 (mean age 56 years; range 41-76 years) had elevated serum calcium-stimulated calcitonin (sCtn) or concurrent marginally elevated serum calcitonin (Ctn) levels, whereas the other 6 (mean age 37.5 years; range 14-52 years) exhibited typical Ctn/sCtn levels (p < 0.05). None of the 15 carriers in these 4 families presented clinical evidence of pheochromocytoma, hyperparathyroidism, or Hirschsprung's disease. In silico analyses revealed that S409Y was a "possibly damaging" mutation that could affect the RET protein inter-domain interface. An in vitro assay revealed that the phosphorylation level of RET tyrosine 905 was relatively higher in the RET S409Y mutant than in wild-type (WT) RET. Moreover, transfection of HEK 293 cells with S409Y enhanced the phosphorylation activity of AKT, ERK pathways, and it increased cell proliferation compared with WT RET, but to a lesser degree than that for the RET C618Y and C634Y mutations. Conclusions: This study demonstrates that the novel germline RET S409Y variant is likely pathogenic and is associated with lower penetrance of MTC than that for the C618Y and C634Y mutations. Individuals with S409Y should be managed using a personalized approach, and additionally, "at-risk" family members should be evaluated. Additional studies are needed to elucidate the correlation between the S409Y mutation and multiple endocrine neoplasia type 2-specific tumors.

GDNF and the RET Receptor in Cancer: New Insights and Therapeutic Potential

The Glial cell line-derived neurotrophic Family Ligands (GFL) are soluble neurotrophic factors that are required for development of multiple human tissues, but which are also important contributors to human cancers. GFL signaling occurs through the transmembrane RET receptor tyrosine kinase, a well-characterized oncogene. GFL-independent RET activation, through rearrangement or point mutations occurs in thyroid and lung cancers. However, GFL-mediated activation of wildtype RET is an increasingly recognized mechanism promoting tumor growth and dissemination of a much broader group of cancers. RET and GFL expression have been implicated in metastasis or invasion in diverse human cancers including breast, pancreatic, and prostate tumors, where they are linked to poorer patient prognosis. In addition to directly inducing tumor growth in these diseases, GFL-RET signaling promotes changes in the tumor microenvironment that alter the surrounding stroma and cellular composition to enhance tumor invasion and metastasis. As such, GFL RET signaling is an important target for novel therapeutic approaches to limit tumor growth and spread and improve disease outcomes.

Overview of Genetically Determined Diseases/Multiple Endocrine Neoplasia Syndromes Predisposing to Endocrine Tumors

In this chapter, we present an overview of multiple endocrine neoplasia syndromes including their most important clinical and molecular features. Multiple endocrine neoplasia type 1 and 2 syndromes (MEN1 and MEN2) are discussed in detail. Syndromes that are presented in other chapters are only briefly mentioned. We discuss the relevance of germline gene alterations in apparently sporadic endocrine tumors, e.g., medullary thyroid cancer, primary hyperparathyroidism, and neuroendocrine tumors. McCune-Albright syndrome that only exists in non-hereditary, sporadic forms is also discussed in detail, as tumors of several endocrine organs can develop in the same individual.

A dual mechanism of activation of the Sonic Hedgehog pathway in anaplastic thyroid cancer: crosstalk with RAS-BRAF-MEK pathway and ligand secretion by tumor stroma

Sonic Hedgehog (Shh) pathway regulates embryonic development of different organs including the thyroid gland. The aberrant activation of Shh signaling has been found in several types of cancer and according to recent evidences it represents an important regulator of tumor-stroma interaction. In this study, we have analyzed expression, activation and molecular mechanisms regulating the Shh pathway and its involvement in the modulation of tumor stroma interaction in anaplastic thyroid cancer (ATC) cells. Our results suggest that Shh signaling undergoes a dual mechanism of induction in ATC cells: 1) a basal non-canonical Smo-dependent activation of Gli transcription factor that is partly caused by interaction with the RAS/BRAF/MEK oncogenic pathway and is characterized by the absence of Shh ligand expression in thyroid cancer cells and 2) a paracrine response of cancer cells to Shh ligand secreted by tumor stroma (fibroblasts and mesenchymal stromal cells, MSCs) inducing cancer cell migration and in vitro tumorigenesis. Our data therefore suggest Shh as a potential novel therapeutic target in aggressive thyroid cancers.