BRAF Inhibitors in Thyroid Cancer: Clinical Impact, Mechanisms of Resistance and Future Perspectives

V600EBRAF Inhibition Induces Cytoprotective Autophagy through AMPK in Thyroid Cancer Cells

The dysregulation of autophagy is important in the development of many cancers, including thyroid cancer, where ^V600EBRAF is a main oncogene. Here, we analyse the effect of ^V600EBRAF inhibition on autophagy, the mechanisms involved in this regulation and the role of autophagy in cell survival of thyroid cancer cells. We reveal that the inhibition of ^V600EBRAF activity with its specific inhibitor PLX4720 or the depletion of its expression by siRNA induces autophagy in thyroid tumour cells. We show that ^V600EBRAF downregulation increases LKB1-AMPK signalling and decreases mTOR activity through a MEK/ERK-dependent mechanism. Moreover, we demonstrate that PLX4720 activates ULK1 and increases autophagy through the activation of the AMPK-ULK1 pathway, but not by the inhibition of mTOR. In addition, we find that autophagy blockade decreases cell viability and sensitize thyroid cancer cells to ^V600EBRAF inhibition by PLX4720 treatment. Finally, we generate a thyroid xenograft model to demonstrate that autophagy inhibition synergistically enhances the anti-proliferative and pro-apoptotic effects of ^V600EBRAF inhibition in vivo. Collectively, we uncover a new role of AMPK in mediating the induction of cytoprotective autophagy by ^V600EBRAF inhibition. In addition, these data establish a rationale for designing an integrated therapy targeting ^V600EBRAF and the LKB1-AMPK-ULK1-autophagy axis for the treatment of ^V600EBRAF-positive thyroid tumours.

Concise genetic profile of lung carcinoma

The WHO classification of lung cancer (2015) is based on immunohistochemistry and molecular evaluation. This also includes microscopic analysis of morphological patterns that aids in the pathological diagnosis and classification of lung cancers. Lung cancers are the leading cause of cancer deaths worldwide. Recent advancements in identifying the etiopathogenesis are majorly driven by gene mutation studies. This has been explained by The Cancer Genome Atlas, next-generation sequencer and TRAcking non-small cell lung cancer evolution through therapy [Rx]. This article reviews the genetic profile of adenocarcinoma, squamous cell carcinoma, small cell carcinoma, large cell neuroendocrine carcinoma and pulmonary carcinoids. This includes the prolific genetic alterations and novel molecular changes seen in these tumours. In addition, target- specific drugs that have shown promising effects in clinical use and trials are also briefly discussed.

BRAF Inhibitors Induce Feedback Activation of RAS Pathway in Thyroid Cancer Cells

BRAF^V600E is the most frequent oncogenic mutation identified in papillary thyroid cancer (PTC). In PTC patients who do not respond to standard treatment, BRAF inhibitors are currently tested as alternative strategies. However, as observed for other targeted therapies, patients eventually develop drug resistance. The mechanisms of BRAF inhibitors response are still poorly understood in a thyroid cancer (TC) context. In this study, we investigated in BRAF^V600E mutated TC cell lines the effects of Vemurafenib and Dabrafenib, two BRAF inhibitors currently used in a clinical setting. We assessed cell proliferation, and the expression and activity of the thyroid function related transporter NIS following the treatment with BRAF inhibitors. In addition, we investigated the global gene expression by microarray, the relevant modulated biological processes by gene set enrichment analysis (GSEA), and TC specific gene signatures related to MAPK pathway activation, thyroid differentiation, and transcriptional profile associated with BRAF^V600E or RAS mutation. We found that both inhibitors induce antiproliferative and redifferentiative effects on TC cells, as well as a rewiring of the MAPK pathway related to RAS signaling. Our results suggest a possible mechanism of drug response to the BRAF inhibitors Vemurafenib or Dabrafenib, supporting very recent findings in TC patients treated with targeted therapies.

Recurrent Somatic MAP2K1 Mutations in Papillary Thyroid Cancer and Colorectal Cancer

Mitogen-activated protein kinase kinase 1 (MAP2K1) is a dual specificity protein kinase that phosphorylates both threonine and tyrosine residues in ERK. MAP2K1 mutations have been identified in several cancers. However, their role in Middle Eastern papillary thyroid cancer (PTC) and colorectal cancer (CRC) is lacking. In this study, we evaluated the prevalence of MAP2K1 mutations in a large cohort of Middle Eastern PTC and CRC using whole-exome and Sanger sequencing technology. In the discovery cohort of 100 PTC and 100 CRC cases (comprising 50 MAPK mutant and 50 MAPK wildtype cases each), we found one MAP2K1 mutation each in PTC and CRC, both of which were MAPK wildtype. We further analyzed 286 PTC and 289 CRC MAPK wildtype cases and found three MAP2K1 mutant PTC cases and two MAP2K1 mutant CRC cases. Thus, the overall prevalence of MAP2K1 mutation in MAPK wildtype cases was 1.1% (4/336) in PTC and 0.9% (3/339) in CRC. Histopathologically, three of the four MAP2K1 mutant PTC cases were follicular variant and all four tumors were unifocal with absence of extra-thyroidal extension. All the three CRC cases harboring MAP2K1 mutation were of older age (> 50 years) and had moderately differentiated stage II/III tumors located in the left colon. In conclusion, this is the first comprehensive report of MAP2K1 somatic mutations prevalence in PTC and CRC from this ethnicity. The mutually exclusive nature of MAP2K1 and MAPK mutations suggests that each of these mutation may function as an initiating mutation driving tumorigenesis through MAPK signaling pathway.

Open-Label, Single-Arm, Multicenter, Phase II Trial of Lenvatinib for the Treatment of Patients With Anaplastic Thyroid Cancer

PURPOSE

Anaplastic thyroid cancer (ATC), an aggressive malignancy, is associated with a poor prognosis and an unmet need for effective treatment, especially for patients without BRAF mutations or NTRK or RET fusions. Lenvatinib is US Food and Drug Administration-approved for radioiodine-refractory differentiated thyroid cancer and has previously demonstrated activity in a small study of patients with ATC (n = 17). We aimed to further evaluate lenvatinib in ATC.

METHODS

This open-label, multicenter, international, phase II study enrolled patients with ATC, who had ≥ 1 measurable target lesion, to receive lenvatinib 24 mg once daily. The primary end points were objective response rate (ORR) by investigator assessment per RECIST v1.1 and safety. Responses were confirmed ≥ 4 weeks after the initial response. Additional end points included progression-free survival and overall survival (OS).

RESULTS

The study was halted for futility as the minimum ORR threshold of 15% was not met upon interim analysis. The interim analysis set included the first 20 patients. The full analysis set includes all 34 enrolled and treated patients. In the full analysis set, one patient achieved a partial response (ORR, 2.9%; 95% CI, 0.1 to 15.3). More than half of the evaluable patients experienced tumor shrinkage; three patients experienced a > 30% tumor reduction. The median progression-free survival was 2.6 months (95% CI, 1.4 to 2.8); the median overall survival was 3.2 months (95% CI, 2.8 to 8.2). The most common treatment-related adverse events (AEs) were hypertension (56%), decreased appetite (29%), fatigue (29%), and stomatitis (29%). No major treatment-related bleeding events or grade 5 treatment-related AEs occurred.

CONCLUSION

The safety profile of lenvatinib in ATC was manageable, and many AEs were attributable to the progression of ATC. The results suggest that lenvatinib monotherapy may not be an effective treatment for ATC; further investigation may be warranted.

MAP-Kinase-Driven Hematopoietic Neoplasms: A Decade of Progress in the Molecular Age

Mutations in members of the mitogen-activated protein kinase (MAPK) pathway are extensively studied in epithelial malignancies, with BRAF mutations being one of the most common alterations activating this pathway. However, BRAF mutations are overall quite rare in hematological malignancies. Studies over the past decade have identified high-frequency BRAF V600E, MAP2K1, and other kinase alterations in two groups of MAPK-driven hematopoietic neoplasms: hairy cell leukemia (HCL) and the systemic histiocytoses. Despite HCL and histiocytoses sharing common molecular alterations, these are phenotypically distinct malignancies that differ in respect to clinical presentation and suspected cell of origin. The purpose of this review is to highlight the molecular advancements over the last decade in the histiocytic neoplasms and HCL and discuss the impact these insights have had on our understanding of the molecular pathophysiology, cellular origins, and therapy of these enigmatic diseases as well as perspectives for future research directions.

Molecular mechanisms of radioactive iodine refractoriness in differentiated thyroid cancer: Impaired sodium iodide symporter (NIS) expression owing to altered signaling pathway activity and intracellular localization of NIS

The advanced, metastatic differentiated thyroid cancers (DTCs) have a poor prognosis mainly owing to radioactive iodine (RAI) refractoriness caused by decreased expression of sodium iodide symporter (NIS), diminished targeting of NIS to the cell membrane, or both, thereby decreasing the efficacy of RAI therapy. Genetic aberrations (such as BRAF, RAS, and RET/PTC rearrangements) have been reported to be prominently responsible for the onset, progression, and dedifferentiation of DTCs, mainly through the activation of mitogen-activated protein kinase (MAPK) and phosphoinositide 3-kinase (PI3K)/AKT signaling pathways. Eventually, these alterations result in a lack of NIS and disabling of RAI uptake, leading to the development of resistance to RAI therapy. Over the past decade, promising approaches with various targets have been reported to restore NIS expression and RAI uptake in preclinical studies. In this review, we summarized comprehensive molecular mechanisms underlying the dedifferentiation in RAI-refractory DTCs and reviews strategies for restoring RAI avidity by tackling the mechanisms.

New Insights into the Link between Melanoma and Thyroid Cancer: Role of Nucleocytoplasmic Trafficking

Cancer remains a major public health concern, mainly because of the incompletely understood dynamics of molecular mechanisms for progression and resistance to treatments. The link between melanoma and thyroid cancer (TC) has been noted in numerous patients. Nucleocytoplasmic transport of oncogenes and tumor suppressor proteins is a common mechanism in melanoma and TC that promotes tumorigenesis and tumor aggressiveness. However, this mechanism remains poorly understood. Papillary TC (PTC) patients have a 1.8-fold higher risk for developing cutaneous malignant melanoma than healthy patients. Our group and others showed that patients with melanoma have a 2.15 to 2.3-fold increased risk of being diagnosed with PTC. The BRAF V600E mutation has been reported as a biological marker for aggressiveness and a potential genetic link between malignant melanoma and TC. The main mechanistic factor in the connection between these two cancer types is the alteration of the RAS-RAF-MEK-ERK signaling pathway activation and translocation. The mechanisms of nucleocytoplasmic trafficking associated with RAS, RAF, and Wnt signaling pathways in melanoma and TC are reviewed. In addition, we discuss the roles of tumor suppressor proteins such as p53, p27, forkhead O transcription factors (FOXO), and NF-_KB within the nuclear and cytoplasmic cellular compartments and their association with tumor aggressiveness. A meticulous English-language literature analysis was performed using the PubMed Central database. Search parameters included articles published up to 2021 with keyword search terms melanoma and thyroid cancer, BRAF mutation, and nucleocytoplasmic transport in cancer.

Perspectives on the Treatment of Advanced Thyroid Cancer: Approved Therapies, Resistance Mechanisms, and Future Directions

For differentiated thyroid cancer (DTC), systemic therapy with radioactive iodine (RAI) is utilized for radiosensitive disease, while for radioiodine refractory (RAIR) disease, current standard of care is treatment with multikinase tyrosine kinase inhibitors (TKI). For BRAF-mutant DTC or anaplastic thyroid cancer (ATC), treatment with inhibitors targeting BRAF and MEK are important advances. RET-inhibitors for RET-mutated medullary thyroid cancer (MTC) recently have been FDA-approved for metastatic disease. Nevertheless, treatment of thyroid cancer resistant to current systemic therapies remains an important area of need. Resistance mechanisms are being elucidated, and novel therapies including combinations of BRAF and MEK inhibitors with RAI or other targeted therapies or TKIs combined with checkpoint inhibition are current areas of exploration.

Novel Therapeutics in Radioactive Iodine-Resistant Thyroid Cancer

Iodine-resistant cancers account for the vast majority of thyroid related mortality and, until recently, there were limited therapeutic options. However, over the last decade our understanding of the molecular foundation of thyroid function and carcinogenesis has driven the development of many novel therapeutics. These include FDA approved tyrosine kinase inhibitors and small molecular inhibitors of VEGFR, BRAF, MEK, NTRK and RET, which collectively have significantly changed the prognostic outlook for this patient population. Some therapeutics can re-sensitize de-differentiated cancers to iodine, allowing for radioactive iodine treatment and improved disease control. Remarkably, there is now an FDA approved treatment for BRAF-mutated patients with anaplastic thyroid cancer, previously considered invariably and rapidly fatal. The treatment landscape for iodine-resistant thyroid cancer is changing rapidly with many new targets, therapeutics, clinical trials, and approved treatments. We provide an up-to-date review of novel therapeutic options in the treatment of iodine-resistant thyroid cancer.

BRAF: A Two-Faced Janus

Gain-of-function of V-Raf Murine Sarcoma Viral Oncogene Homolog B (BRAF) is one of the most frequent oncogenic mutations in numerous cancers, including thyroid papillary carcinoma, melanoma, colon, and lung carcinomas, and to a lesser extent, ovarian and glioblastoma multiforme. This mutation aberrantly activates the mitogen-activated protein (MAP) kinase extracellular signal-regulated kinase (MEK)/extracellular signal-regulated kinase (ERK) signaling pathway, thereby eliciting metastatic processes. The relevance of BRAF mutations stems from its prognostic value and, equally important, from its relevant therapeutic utility as an actionable target for personalized treatment. Here, we discuss the double facets of BRAF. In particular, we argue the need to implement diagnostic molecular algorithms that are able to detect this biomarker in order to streamline and refine diagnostic and therapeutic decisions.

What Is New in Thyroid Cancer: The Special Issue of the Journal Cancers

The incidence of thyroid cancer has increased over the past 3 to 4 decades. Nonetheless, the mortality from thyroid cancer has remained stable. The thyroid gland may develop nodules encompassing several types of cell proliferation, from frankly benign to very aggressive forms with many intermediate challenging variants. For this reason, there is growing interest in evaluating thyroid nodules from many points of view, from the clinical to the molecular aspects, in the search for innovative diagnostic and prognostic parameters. The aim of this Special Issue was to provide an overview of recent developments in understanding the biology and molecular oncology of thyroid tumors of follicular cell derivation and their repercussions on the diagnosis, prognosis, and therapy. The contributions of many experts in the field made up a Special Issue of Cancers journal, that focusing on different aspects, including mechanistic and functional facets, gives the status of art of clinical and biological perspectives of thyroid cancer.

Developing Drugs for Tissue-Agnostic Indications: A Paradigm Shift in Leveraging Cancer Biology for Precision Medicine

Targeted therapies have reshaped the landscape of the development of cancer therapeutics. Recent biomarker‐driven, tissue‐agnostic clinical trials represent a significant paradigm shift in precision cancer medicine. Despite their growth in preclinical and clinical studies, to date only a few biomarker‐driven, tissue‐agnostic indications have seen approval by the US Food and Drug Administration (FDA). These approvals include pembrolizumab in microsatellite instability‐high or mismatch repair deficient solid tumors, as well as both larotrectinib and entrectinib in NTRK fusion‐positive tumors. Complex cancer biology, clinical trial design, and identification of resistance mechanisms represent some of the challenges that future tissue‐agnostic therapies have to overcome. In this Review, we present a brief history of the development of tissue‐agnostic therapies, comparing the similarities in the approval of pembrolizumab, larotrectinib, and entrectinib for tissue‐agnostic indications. We also explore the future of tissue‐agnostic cancer therapeutics while identifying important challenges for the future that drugs targeting tissue‐agnostic indications will face.

Evaluation of the expression levels of BRAFV600E mRNA in primary tumors of thyroid cancer using an ultrasensitive mutation assay

Background

The BRAF^V600E gene encodes for the mutant BRAF^V600E protein, which triggers downstream oncogenic signaling in thyroid cancer. Since most currently available methods have focused on detecting BRAF^V600E mutations in tumor DNA, there is limited information about the level of BRAF^V600E mRNA in primary tumors of thyroid cancer, and the diagnostic relevance of these RNA mutations is not known.

Methods

Sixty-two patients with thyroid cancer and non-malignant thyroid disease were included in the study. Armed with an ultrasensitive technique for mRNA-based mutation analysis based on a two step RT-qPCR method, we analysed the expression levels of the mutated BRAF^V600E mRNA in formalin-fixed paraffin-embedded samples of thyroid tissues. Sanger sequencing for detection of BRAF^V600E DNA was performed in parallel for comparison and normalization of BRAF^V600E mRNA expression levels.

Results

The mRNA-based mutation detection assay enables detection of the BRAF^V600E mRNA transcripts in a 10,000-fold excess of wildtype BRAF counterparts. While BRAF^V600E mutations could be detected by Sanger sequencing in 13 out of 32 malignant thyroid cancer FFPE tissue samples, the mRNA-based assay detected mutations in additionally 5 cases, improving the detection rate from 40.6 to 56.3%. Furthermore, we observed a surprisingly large, 3-log variability, in the expression level of the BRAF^V600E mRNA in FFPE samples of thyroid cancer tissue.

Conclusions

The expression levels of BRAF^V600E mRNA was characterized in the primary tumors of thyroid cancer using an ultrasensitive mRNA-based mutation assay. Our data inspires further studies on the prognostic and diagnostic relevance of the BRAF^V600E mRNA levels as a molecular biomarker for the diagnosis and monitoring of various genetic and malignant diseases.

ETV5 overexpression contributes to tumor growth and progression of thyroid cancer through PIK3CA

AIMS

Thyroid cancer is a common endocrine malignancy and sex hormone plays an important role in it. We have previously shown that activation of estrogen receptor (ER) α promotes thyroid cancer cell proliferation and invasion. Here, we attempted to investigate the role of ETS variant 5 (ETV5) on estrogen drived thyroid malignancy.

MAIN METHODS

Ten patients with follicular thyroid cancer were enrolled in this study. Cell proliferation and migration ability were analyzed by CCK-8 assay and cell migration assay, respectively. Chromatin immunoprecipitation-PCR and luciferase assay were conducted to analyze the relationship of ETV5 and PIK3CA.

KEY FINDINGS

ETV5 is highly expressed in thyroid tissues from patients with follicular thyroid cancer as well as in FTC133 cells. 17b-estradiol or overexpression of ERα induced an increase in ETV5 protein level in FTC133 cells. Knockdown of ETV5 inhibited FTC133 cell proliferation, migration, and epithelial-mesenchymal transition, while 17b-estradiol could not correct this effect. Additionally, the level of PIK3CA was markedly decreased in ETV5 knockdown cells and had a positive correlation with ETV5 in thyroid cancer patients. Chromatin immunoprecipitation-PCR analysis and luciferase assay confirmed that ETV5 directly targeted PIK3CA and that ETV5 was bound to the promoter region of PIK3CA. In addition, PIK3CA overexpression abrogated ETV5-induced cell growth, migration and epithelial-mesenchymal transition.

SIGNIFICANCE

ETV5 enhanced cell proliferation, migration, and epithelial-mesenchymal transition through the PIK3CA signaling pathway, indicating that ETV5 may be a therapeutic target in thyroid cancer.

ANGPTL4 Promotes the Proliferation of Papillary Thyroid Cancer via AKT Pathway

Purpose

Although papillary thyroid carcinoma (PTC) is associated with a generally favorable prognosis, about 15% of patients present recurrence and distant metastasis in the next decade leading to death. Angiopoietin-like 4 (ANGPTL4) is secreted to circulation and belongs to the angiopoietin-like proteins. The expression of ANGPTL4 was increased in several solid tumor tissues compared to corresponding paracancerous tissues. ANGPTL4 was identified as pro-tumorigenic protein, including stimulating tumor cell growth, promoting tumor metastasis. However, the clinical significance and biological function of ANGPTL4 in PTC is still unclear. Hence, the purpose of this study was to evaluate the role of ANGPTL4 in PTC, investigating the possibility of whether ANGPTL4 could become a novel target for PTC therapy.

Methods

We investigated the expression level of ANGPTL4 and pAKT in PTC and paracancerous tissue by immunohistochemistry. We determined the effect of ANGPTL4 in PTC cell proliferation through cell counting kit-8 (CCK-8) and cell cycle by flow cytometry analysis. Furthermore, the correlation between ANGPTL4 expression levels and PTC cell proliferation from the TCGA data set was analyzed by GSEA. We explored the role of ANGPTL4 on the phosphorylation of AKT and proliferation in PTC cells via overexpression or knockdown assays and AKT inhibitor assay.

Results

In the present study, we found that ANGPTL4 was highly expressed in both protein and mRNA level in PTC compared with adjacent noncancerous tissues or benign nodule. ANGPTL4 expression increased according to thyroid tumor progression. ANGPTL4 level was positively correlated with the size of PTC. ANGPTL4 increased cell proliferation and decreased cell cycle arrest of PTC. Knockdown of ANGPTL4 inhibited the phosphorylation of AKT. ANGPTL4 regulated PTC cell proliferation through AKT signaling pathway.

Conclusion

Our findings suggested that ANGPTL4 was increased in PTC compared with adjacent noncancerous tissues, and ANGPTL4 increased cell proliferation and inhibited cell cycle arrest in PTC cells via promoting AKT phosphorylation. The study may provide fundamental information to suggest its suitability as a target for the treatment of PTC.

Disparity between Inter-Patient Molecular Heterogeneity and Repertoires of Target Drugs Used for Different Types of Cancer in Clinical Oncology

Inter-patient molecular heterogeneity is the major declared driver of an expanding variety of anticancer drugs and personalizing their prescriptions. Here, we compared interpatient molecular heterogeneities of tumors and repertoires of drugs or their molecular targets currently in use in clinical oncology. We estimated molecular heterogeneity using genomic (whole exome sequencing) and transcriptomic (RNA sequencing) data for 4890 tumors taken from The Cancer Genome Atlas database. For thirteen major cancer types, we compared heterogeneities at the levels of mutations and gene expression with the repertoires of targeted therapeutics and their molecular targets accepted by the current guidelines in oncology. Totally, 85 drugs were investigated, collectively covering 82 individual molecular targets. For the first time, we showed that the repertoires of molecular targets of accepted drugs did not correlate with molecular heterogeneities of different cancer types. On the other hand, we found that the clinical recommendations for the available cancer drugs were strongly congruent with the gene expression but not gene mutation patterns. We detected the best match among the drugs usage recommendations and molecular patterns for the kidney, stomach, bladder, ovarian and endometrial cancers. In contrast, brain tumors, prostate and colorectal cancers showed the lowest match. These findings provide a theoretical basis for reconsidering usage of targeted therapeutics and intensifying drug repurposing efforts.