Diego Claro de Mello

Anaplastic thyroid carcinoma (ATC) is the most aggressive thyroid cancer type harboring TP53, TERT promoter and MAPK signaling alterations. Additionally, EZH2 overexpression leads to epigenetic silencing of tumor suppressor and cell differentiation genes. Here, we investigate the mechanism of EZH2 transcriptional activation in ATC. We used several luciferase reporter constructs with deletion of transcription factor (TF) binding sites identified in silico to determine EZH2 minimal promoter in ATC. MAPK signaling blockage with U0126, TF overexpression and knock-down strategies were used to evaluate EZH2 expression and reporter plasmid response, and the cross talk with TFs. As a result, we observed that EZH2 transcription is regulated by a minimal promoter of 107 bp (E3/4 region), that contains binding sites for TF NFYA, YY1 and FOXM1, highly expressed in ATC, that when deleted reduced EZH2 promoter activation. MAPK blockage reduced EZH2 and influenced YY1 and FOXM1 TF levels, while overexpression of NFYA, YY1 and FOXM1 resulted in pro-tumoral effects and EZH2 upregulation in papillary thyroid cancer cells. On the other hand, FOXM1 knock-down reduced EZH2 activation in ATC cells. Thus, we identified the minimal promoter region essential for EZH2 activation in ATC that is controlled by MAPK signaling in crosstalk with TFs.

Lung adenocarcinoma is the most common form of lung cancer with a 5-year survival rate of 15%, largely due to asymptomatic metastasis and late diagnosis. Overexpression of Polycomb group (PcG) proteins, particularly EZH2, the catalytic component of Polycomb Repressive Complex 2 (PRC2), has been associated with the pathogenesis of lung cancer, frequently showing correlation with cancer progression and poor prognosis. In this study, EZH2 levels were modulated by CRISPR/Cas9 gene editing and PRC2 activity was inhibited with EZH2 inhibitor EPZ6438 or EED inhibitor MAK683. EZH2 gene editing reduced cell proliferation, migration, invasion, and colony formation and reduced NFκ-B signaling activation, indicating an antitumoral effect in vitro. Moreover, EZH2 inhibition also increased the expression of differentiation-related genes, such as GATA5, FOXA2, and lung surfactants, indicating a pro-differentiation effect. However, EZH2-edited cells injected into an immunocompromised mouse model generated larger tumors compared to unedited cells. This was accompanied by increased expression of other PcG genes, including EZH1, CBX2, RING1, EED, and SUZ12, suggesting a compensatory interaction between PRC2 and PRC1 complexes. These findings provide significant clinical relevance, both in elucidating the mechanisms of novel molecular targets and in guiding treatment strategies for lung cancer when using epigenetic inhibitors.

Anaplastic thyroid carcinoma (ATC) is a highly aggressive malignancy characterized by dedifferentiation and radioiodine refractoriness. We investigated whether EZH2‐mediated H3K27me3 deposition represses thyroid differentiation genes (TDGs) in ATC cells. Online ChIP‐seq analyses and CUT&RUN confirmed EZH2/H3K27me3 enrichment at key TDGs ( SLC5A5 , NKX2‐1 , TSHR , FOXE1 , TPO ). Pharmacological inhibition of EZH2 with EPZ6438 reactivated TDG expression in RAS and BRAF‐mutated ATC cell lines and partially restored iodide uptake. Co‐treatment with the MEK1/2 inhibitor U0126 further enhanced TDG expression, consistent with MAPK‐dependent regulation of EZH2. These findings reveal EZH2 as a mediator of ATC dedifferentiation and highlight its inhibition as a potential strategy to restore thyroid function and sensitize tumors to radioiodine. Impact statement: This study reveals how EZH2‐driven epigenetic remodeling controls thyroid cell dedifferentiation and loss of iodide uptake in anaplastic thyroid cancer. Our findings provide new mechanistic insights and highlight an FDA‐approved drug with repurposing potential, advancing both anaplastic thyroid cancer biology research and therapeutic perspectives.

Modulating the expression of a coding or noncoding gene is a key tool in scientific research. This strategy has evolved methodologically due to advances in cloning approaches, modeling/algorithms in short hairpin RNA (shRNA) design for knockdown efficiency, and biochemical modifications in RNA synthesis, among other developments. Overall, these modifications have improved the ways to either reduce or induce the expression of a given gene with efficiency and facility for implementation in the lab. Allied with that, the existence of [...] ABSTRACT Modulating the expression of a coding or noncoding gene is a key tool in scientific research. This strategy has evolved methodologically due to advances in cloning approaches, modeling/algorithms in short hairpin RNA (shRNA) design for knockdown efficiency, and biochemical modifications in RNA synthesis, among other developments. Overall, these modifications have improved the ways to either reduce or induce the expression of a given gene with efficiency and facility for implementation in the lab. Allied with that, the existence of

Non-coding RNAs (ncRNAs) have emerged as pivotal regulators in cellular biology, dispelling their former perception as ‘junk transcripts’. Notably, the DLK1-DIO3 region harbors numerous ncRNAs, including long non-coding RNAs (lncRNAs) and over 50 microRNA genes. While papillary thyroid cancer showcases a pervasive decrease in DLK1-DIO3-derived ncRNA expression, the precise mechanisms driving this alteration remain elusive. We hypothesized that epigenetic alterations underlie shifts in ncRNA expression during thyroid cancer initiation and progression. This study aimed to elucidate the epigenetic mechanisms governing DLK1-DIO3 region expression in this malignancy. We have combined the analysis of DNA methylation by bisulfite sequencing together with that of histone modifications through ChIP-qPCR to gain insights into the epigenetic contribution to thyroid cancer in cell lines representing malignancies with different genetic backgrounds. Our findings characterize the region’s epigenetic signature in thyroid cancer, uncovering distinctive DNA methylation patterns, particularly within CpG islands on the lncRNA MEG3-DMR, which potentially account for its downregulation in tumors. Pharmacological intervention targeting DNA methylation combined with histone deacetylation restored ncRNA expression. These results contribute to the understanding of the epigenetic mechanisms controlling the DLK1-DIO3 region in thyroid cancer, highlighting the combined role of DNA methylation and histone marks in regulating the locus’ expression.

Anaplastic thyroid cancer (ATC) is a rare and lethal form of thyroid cancer that requires urgent investigation of new molecular targets involved in its aggressive biology. In this context, the overactivation of Polycomb Repressive Complex 2/EZH2, which induces chromatin compaction, is frequently observed in aggressive solid tumors, making the EZH2 methyltransferase a potential target for treatment. However, the deregulation of chromatin accessibility is yet not fully investigated in thyroid cancer. In this study, EZH2 expression was modulated by CRISPR/Cas9-mediated gene editing and pharmacologically inhibited with EZH2 inhibitor EPZ6438 alone or in combination with the MAPK inhibitor U0126. The results showed that CRISPR/Cas9-induced EZH2 gene editing reduced cell growth, migration and invasion in vitro and resulted in a 90% reduction in tumor growth when EZH2-edited cells were injected into an immunocompromised mouse model. Immunohistochemistry analysis of the tumors revealed reduced tumor cell proliferation and less recruitment of cancer-associated fibroblasts in the EZH2-edited tumors compared to the control tumors. Moreover, EZH2 inhibition induced thyroid-differentiation genes’ expression and mesenchymal-to-epithelial transition (MET) in ATC cells. Thus, this study shows that targeting EZH2 could be a promising neoadjuvant treatment for ATC, as it promotes antitumoral effects in vitro and in vivo and induces cell differentiation.

Important advances on the role of genetic alterations in thyroid cancer have been achieved in the last two decades. One key reason is linked to the development of technical approaches that allowed for the mimicking of genetic alterations in vitro and in vivo and, more recently, the gene editing methodology. The CRISPR/Cas methodology has emerged as a tangible tool for editing virtually any DNA sequence in the genome. To induce a double-strand break and programmable gene editing, Cas9 endonuclease is guided by a single-guide RNA (sgRNA) that is complementary to the target sequence in DNA. The gene editing per se occurs as the cells repair the broken DNA and may erroneously change the original DNA sequence. In this review, we explore the principles of the CRISPR/Cas system to facilitate an understanding of the mainstream technique and its applications in gene editing. Furthermore, we explored new applications of CRISPR/Cas for gene modulation without changing the DNA sequence and provided a Dry Lab experience for those who are interested in starting “CRISPRing” any given gene. In the last section, we will discuss the progress in the knowledge of thyroid cancer biology fostered by the CRISPR/Cas gene editing tools.