Targeting autophagy in thyroid cancers

Role of thyroid hormone in an experimental model of atherosclerosis: the potential mediating role of immune response and autophagy

Accumulating evidence has revealed that several conditions related to abnormal thyroid hormone status, such as dyslipidemia, hypertension, or hypercoagulable state, can exacerbate atherosclerotic vascular disease. Thyroid hormone effects on vascular smooth muscle cells and endothelial cells have also been studied extensively. However, only limited information is available on thyroid hormone-mediated immune response in current review articles on the pathophysiology of atherosclerosis. This report thus presents an overview of the recent advances in the understanding of the dynamic interactions taking place between thyroid hormone status and immune response in the pathogenesis of atherosclerosis. In particular, we focus on macrophages and T-lymphocytes, which have been recognized as important determinants for the initiation and development of atherosclerosis. Numerous studies have revealed the role of autophagy in immune cells produced in atherosclerosis. In addition, thyroid hormones induce autophagy in several cells and tissues, such as liver, skeletal muscles, lungs, and brown adipose tissue. Our research group, among others, have reported different targets of thyroid hormone-mediated autophagy, including lipid droplets (lipophagy), mitochondria (mitophagy), and aggregated proteins (aggrephagy). Based on these findings, thyroid hormone-mediated autophagy could serve as a novel therapeutic approach for atherosclerosis. We also consider the limitations of the current murine models for studies on atherosclerosis, especially in relation to low-density lipoprotein-cholesterol driven atherosclerotic plaque.

Thyroid Cancer and Fibroblasts

Thyroid cancer is the most common type of endocrine cancer, and its prevalence continue to rise. Non-metastatic thyroid cancer patients are successfully treated. However, looking for new therapeutic strategies is of great importance for metastatic thyroid cancers that still lead to death. With respect to this, the tumor microenvironment (TME), which plays a key role in tumor progression, should be considered as a new promising therapeutic target to hamper thyroid cancer progression. Indeed, thyroid tumors consist of cancer cells and a heterogeneous and ever-changing niche, represented by the TME, which contributes to establishing most of the features of cancer cells. The TME consists of extracellular matrix (ECM) molecules, soluble factors, metabolites, blood and lymphatic tumor vessels and several stromal cell types that, by interacting with each other and with tumor cells, affect TME remodeling, cancer growth and progression. Among the thyroid TME components, cancer-associated fibroblasts (CAFs) have gained more attention in the last years. Indeed, recent important evidence showed that thyroid CAFs strongly sustain thyroid cancer growth and progression by producing soluble factors and ECM proteins, which, in turn, deeply affect thyroid cancer cell behavior and aggressiveness. Hence, in this article, we describe the thyroid TME, focusing on the desmoplastic stromal reaction, which is a powerful indicator of thyroid cancer progression and an invasive growth pattern. In addition, we discuss the origins and features of the thyroid CAFs, their influence on thyroid cancer growth and progression, their role in remodeling the ECM and their immune-modulating functions. We finally debate therapeutic perspectives targeting CAFs.

Curcumin induces autophagic cell death in human thyroid cancer cells

Curcumin, a polyphenolic compound, is a well-known anticancer agent, although its poor bioavailability remains a big concern. Recent studies suggest that autophagy-targeted therapy may be a useful adjunct treatment for patients with thyroid cancer. Curcumin acts as an autophagy inducer on many cancer cells. However, little is known about the exact role of curcumin on thyroid cancer cells. In the present study, curcumin significantly inhibited the growth of thyroid cancer cells. Autophagy was markedly induced by curcumin treatment as evidenced by an increase in LC3-II conversion, beclin-1 accumulation, p62 degradation as well as the increased formation of acidic vesicular organelles (AVOs). 3-MA, an autophagy inhibitor, partially rescued thyroid cancer cells from curcumin-induced cell death. Additionally, curcumin was found to exert selective cytotoxicity on thyroid cancer cells but not normal epithelial cells and acted as an autophagy inducer through activation of MAPK while inhibition of mTOR pathways. Hyperactivation of the AKT/mTOR axis was observed in the majority of PTC samples we tested, and thyroid cancer cell lines along with cancer tissue specimens sustained a low basal autophagic activity. Taken together, our results provide new evidence that inducing autophagic cell death may serve as a potential anti-cancer strategy to handle thyroid cancer.

Next-Generation Molecular Imaging of Thyroid Cancer

An essential aspect of thyroid cancer (TC) management is personalized and precision medicine. Functional imaging of TC with radioiodine and [18F]FDG has been frequently used in disease evaluation for several decades now. Recently, advances in molecular imaging have led to the development of novel tracers based on aptamer, peptide, antibody, nanobody, antibody fragment, and nanoparticle platforms. The emerging targets-including HER2, CD54, SHP2, CD33, and more-are promising targets for clinical translation soon. The significance of these tracers may be realized by outlining the way they support the management of TC. The provided examples focus on where preclinical investigations can be translated. Furthermore, advances in the molecular imaging of TC may inspire the development of novel therapeutic or theranostic tracers. In this review, we summarize TC-targeting probes which include transporter-based and immuno-based imaging moieties. We summarize the most recent evidence in this field and outline how these emerging strategies may potentially optimize clinical practice.

Pseudogene legumain promotes thyroid carcinoma progression via the microRNA-495/autophagy pathway

The pseudogene legumain (LGMN) has been reported to regulate cancer cell biology. However, the role of LGMN in thyroid carcinoma remains unknown. Herein, Cell Counting Kit 8 and Transwell assays were performed to evaluate cellular proliferation and invasion capacity, respectively. In addition, a tube formation assay was performed to assess HUVEC angiogenesis. The results showed that LGMN depletion attenuated cellular proliferation, invasion and tube formation ability, and that LGMN expression was dysregulated in thyroid carcinoma tumors. Furthermore, patients with high LGMN expression levels exhibited a lower overall survival rate than those with low expression levels. LGMN and microRNA (miR)-495 modulated the expression levels of autophagy-related gene 3 (ATG3) and p62. Finally, ATG3 overexpression rescued the LGMN-regulated thyroid carcinoma phenotype. In conclusion, LGMN was found to promote thyroid carcinoma progression via the miR-495/autophagy axis, thus providing novel insights for understanding the pathogenesis of thyroid carcinoma.

Inhibition of the sonic hedgehog pathway activates TGF-β-activated kinase (TAK1) to induce autophagy and suppress apoptosis in thyroid tumor cells

The sonic hedgehog (Shh) pathway is highly activated in a variety of malignancies and plays important roles in tumorigenesis, tumor growth, drug resistance, and metastasis. Our recent study showed that the inhibitors of the Shh pathway such as cyclopamine (CP), a Smothened (SMO) inhibitor, and GANT61, a Gli1 inhibitor, have modest inhibitory effects on thyroid tumor cell proliferation and tumor growth. The objective of this study was to determine whether autophagy was induced by inhibition of the Shh pathway and could negatively regulate GANT61-induced apoptosis. Here we report that inhibition of the Shh pathway by Gli1 siRNA or by cyclopamine and GANT61 induced autophagy in SW1736 and KAT-18 cells, two anaplastic thyroid cancer cell lines; whereas Gli1 overexpression suppressed autophagy. Mechanistic investigation revealed that inhibition of the Shh pathway activated TAK1 and its two downstream kinases, the c-Jun-terminal kinase (JNK) and AMP-activated protein kinase (AMPK). GANT61-induced autophagy was blocked by TAK1 siRNA and the inhibitors of TAK1 (5Z-7-oxozeaenol, 5Z), JNK (SP600125), and AMPK (Compound C, CC). Inhibition of autophagy by chloroquine and 5Z and by TAK1 and Beclin-1 siRNA enhanced GANT61-induced apoptosis and its antiproliferative activity. Our study has shown that inhibition of the Shh pathway induces autophagy by activating TAK1, whereas autophagy in turn suppresses GANT61-induced apoptosis. We have uncovered a previously unrecognized role of TAK1 in Shh pathway inhibition-induced autophagy and apoptosis.

Repositioning of Antiparasitic Drugs for Tumor Treatment

Drug repositioning is a strategy for identifying new antitumor drugs; this strategy allows existing and approved clinical drugs to be innovatively repurposed to treat tumors. Based on the similarities between parasitic diseases and cancer, recent studies aimed to investigate the efficacy of existing antiparasitic drugs in cancer. In this review, we selected two antihelminthic drugs (macrolides and benzimidazoles) and two antiprotozoal drugs (artemisinin and its derivatives, and quinolines) and summarized the research progresses made to date on the role of these drugs in cancer. Overall, these drugs regulate tumor growth via multiple targets, pathways, and modes of action. These antiparasitic drugs are good candidates for comprehensive, in-depth analyses of tumor occurrence and development. In-depth studies may improve the current tumor diagnoses and treatment regimens. However, for clinical application, current investigations are still insufficient, warranting more comprehensive analyses.

Genomic DNA methylation analysis reveals that BLNK is a key potential gene in the regulation of autophagy-related thyroid cancer progression

The purpose of this study was to explore the relationship between autophagy and DNA methylation, and to identify key genes for autophagy-regulated thyroid cancer progression. We divided patients with thyroid cancer into high-autophagy score (AS) group and low-AS group based on their AS values. The results found that AS was associated with the distant metastasis of thyroid cancer, and adversely affected prognosis. Then, we screened 359 differently expressed genes (DEGs) with DNA methylation status consistent with gene expression change. Functional classification analysis demonstrated that the 359 DEGs consistent with DNA methylation status were significantly involved in adhesion, migration, and differentiation of immune cells. To further screen the key genes in the autophagy-related thyroid cancer progression, we constructed a protein-protein interactions (PPI) network and performed prognostic analysis. B cell linker (BLNK) was identified as the key potential gene affecting autophagy-related thyroid cancer progression. Finally, we verified that BLNK promoted the proliferation of thyroid cancer cells, and BLNK expression was regulated by DNA methylation. Our research provides a new perspective for exploring the relationship between autophagy and DNA methylation during the progression of thyroid cancer and provides a new target for the treatment of metastatic thyroid cancer.

Molecular Mechanism of Resistance to Chemotherapy in Gastric Cancers, the Role of Autophagy

Gastric cancer (GC) is biologically and genetically heterogeneous with complex carcinogenesis at the molecular level. Despite the application of multiple approaches in the GC treatment, its 5-year survival is poor. A major limitation of anti-cancer drugs application is intrinsic or acquired resistance, especially to chemotherapeutical agents. It is known that the effectiveness of chemotherapy remains debatable and varies according to the molecular type of GC. Chemotherapy has an established role in the management of GC. Perioperative chemotherapy or postoperative chemotherapy is applied for localized ones. Most of the advanced GC patients have a poor response to treatment and unfavorable outcomes with standard therapies. Resistance substantially limits the depth and duration of clinical responses to targeted anticancer therapies. Through the use of complementary experimental approaches, investigators have revealed that cancer cells can achieve resistance through adaptation or selection driven by specific genetic, epigenetic, or microenvironmental alterations. Ultimately, these diverse alterations often lead to the activation of MAPK, AKT/mTOR, and Wnt/β-catenin signaling pathways that, when co-opted, enable cancer cells to survive drug treatments. We have summarized the mechanisms of resistance development to cisplatin, 5-fluorouracil, and multidrug resistance in the GC management. The complexity of molecular targets and components of signaling cascades altered in the resistance development results in the absence of significant benefits in GC treatment, and its efficacy remains low. The universal process responsible for the failure in the multimodal approach in GC treatment is autophagy. Its dual role in oncogenesis is the most unexplored issue. We have discussed the possible mechanism of autophagy regulation upon the action of endogenous factors and drugs. The experimental data obtained in the cultured GC cells need further verification. To overcome the cancer resistance and to prevent autophagy as the main reason of ineffective treatment, it is suggested the concept of the direct influence of autophagy molecular markers followed by the standard chemotherapy. Dozen of studies have focused on finding the rationale for the benefits of such complex therapy. The perspectives in the molecular-based management of GC are associated with the development of molecular markers predicting the protective autophagy initiation and search for novel targets of effective anticancer therapy.

HIF-1α-Mediated Telomerase Reverse Transcriptase Activation Inducing Autophagy Through Mammalian Target of Rapamycin Promotes Papillary Thyroid Carcinoma Progression During Hypoxia Stress

Background: It is important to properly understand the molecular mechanisms of aggressive tumors among papillary thyroid carcinomas (PTCs) that are often the most indolent. Hypoxia inducible factor-1α (HIF-1α), induced by hypoxia, plays pivotal roles in the development and metastasis of the many tumors, including PTCs. Upregulation of telomerase reverse transcriptase (TERT) activity is found in highly invasive PTCs. Further, previous studies have reported that autophagy serves as a protective mechanism to facilitate PTC cell survival. We, therefore, hypothesized that there was a link between HIF-1α, TERT, and autophagy in promoting PTC progression. Methods: Immunohistochemistry staining was conducted to evaluate the expressions of HIF-1α, TERT, and autophagy marker, LC3-II, in matched PTC tumors and corresponding nontumor tissues. Two PTC cell lines (TPC-1 and BCPAP) were used in subsequent cytological function studies. Cell viability, proliferation, apoptosis, migration, and invasion were assessed during hypoxia, genetic enhancement and inhibition of TERT, and chemical and genetic inhibition of autophagy. The protein expression levels of the corresponding biomarkers were determined by Western blotting, and autophagy flow was detected. We characterized the molecular mechanism of PTC cell progression. Results: The protein expression levels of HIF-1α, TERT, and LC3-II were upregulated in PTCs and were significantly correlated with high tumor-node-metastasis stage. Further, an in vitro study indicated that HIF-1α induced by hypoxia functioned as a transcriptional activator by binding with sequences potentially located in the TERT promoter and was positively correlated with the malignant behavior of PTC cell lines. Overexpression of TERT inhibited the kinase activity of mammalian target of rapamycin (mTOR), resulting in the activation of autophagy. Functionally, TERT-induced autophagy provided a survival advantage to PTC cells during hypoxia stress. Conclusions: We identified a novel molecular mechanism involving the HIF-1α/TERT axis, which promoted PTC progression by inducing autophagy through mTOR during hypoxia stress. These findings may provide a basis for the new treatment of aggressive PTCs.

ATF2-Induced lncRNA GAS8-AS1 Promotes Autophagy of Thyroid Cancer Cells by Targeting the miR-187-3p/ATG5 and miR-1343-3p/ATG7 Axes

Long non-coding RNAs (lncRNAs) play an essential regulatory role in multiple cancers. However, the role of lncRNAs in papillary thyroid carcinoma (PTC) is still unknown. Here, GAS8-AS1, a novel lncRNA that is significantly downregulated in PTC, was selected for further investigation. The roles of GAS8-AS1 in PTC cells were verified by gain- and loss-of-function experiments. The functional mechanism of GAS8-AS1 on the microRNA (miR)-187-3p/ATG5 axis and miR-1343-3p/ATG7 axis in PTC cells was evaluated using bioinformatics analysis, luciferase reporter assay, Cell Counting Kit-8 (CCK-8) assay, immunohistochemistry analysis, transmission electron microscopy, and immunofluorescence. We found that GAS8-AS1 was downregulated in PTC tissues and cell lines. In patients with PTC, low GAS8-AS1 expression was associated with higher tumor-node-metastasis (TNM) stage and lymph node metastasis (LNM). Functionally, GAS8-AS1 significantly promoted autophagy and inhibited PTC cell proliferation in vitro and promoted tumorigenesis in vivo. Mechanistically, GAS8-AS1 acted as a sponge of miR-187-3p and miR-1343-3p and upregulated ATG5 and ATG7 expression, respectively. The transcription factor ATF2 regulated GAS8-AS1 by binding to the GAS8-AS1 promoter. In conclusion, upregulation of ATF2 activated GAS8-AS1-promoted autophagy of PTC cells by sponging oncogenic miR-187-3p and miR-1343-3p and upregulating the expression of ATG5 and ATG7, respectively, making GAS8-AS1 a potential prognostic biomarker and therapeutic target for PTC.

Hormonal Regulation of Autophagy in Thyroid PCCL3 Cells and the Thyroids of Male Mice

Autophagy is an evolutionarily conserved catabolic process by which cells degrade intracellular proteins and organelles in the lysosomes and recycle their metabolites. We have recently demonstrated the crucial role for the basal level of autophagic activity in thyrocyte survival and homeostasis using the thyroid-specific autophagy knockout mice. Here, we first studied hormonal regulation of autophagy in thyrocytes in vitro using a rat thyroid cell line PCCl3 and in vivo with mice. In cultured PCCl3 cells, thyroxine decreased microtubule-associated protein 1 light chain 3 (LC3) puncta (a component of autophagosome) and increased p62 (an autophagy substrate) levels, showing thyroxine-suppression of autophagy. In contrast, TSH increased both LC3 puncta and p62 levels, but at the same time stabilized p62 protein by inhibiting p62 degradation, indicating TSH induction of autophagy. Our experiments with various inhibitors identified that both the cAMP-protein kinase (PK) A-cAMP response element binding protein/ERK and PKC signaling pathways regulates positively autophagic activity. The in vivo results obtained with wild-type mice treated with methimazole and perchlorate or thyroxine were consistent with in vitro results. Next, in thyroid-specific autophagy knockout mice treated with methimazole and perchlorate (that is, mice were placed under a stressed condition where enhanced autophagy was required) for 2 months, lower follicle sizes and lower thyroglobulin contents in thyrocytes were observed, suggesting impaired thyroglobulin production presumably from insufficient nutrient supply. We therefore conclude that TSH positively regulates autophagic activity through the cAMP-PKA-cAMP response element binding protein/ERK and PKC signaling pathways, whereas thyroid hormones inhibit its activity in thyrocytes. Metabolites produced by autophagy appear to be necessary for protein synthesis stimulated by TSH.

Tissue Factor-Targeted ImmunoPET Imaging and Radioimmunotherapy of Anaplastic Thyroid Cancer

Anaplastic thyroid cancer (ATC) is the most aggressive subtype of thyroid cancers with a dismal prognosis. It is aimed to explore a new biomarker and devise a marker-dependent theranostic pair for ATC. Flow cytometry is used to determine tissue factor (TF) expression in thyroid cancer cell lines. ALT-836, a TF-specific monoclonal antibody, is radiolabeled with 64Cu to develop 64Cu-NOTA-ALT-836. The diagnostic utility is assessed by immuno-positron emission tomography (immunoPET) imaging in ATC models. To facilitate total surgical removal of orthotopic ATCs, a near-infrared fluorescent imaging probe IRDye 800CW-ALT-836 is designed. As the therapeutic component, 131I-ALT-836 is further developed and the radioimmunotherapy (RIT) efficacy of this agent is interrogated in orthotopic ATC models. The results demonstrate that TF is highly expressed on the ATC cell line THJ-16T. 64Cu-NOTA-ALT-836 immunoPET imaging clearly delineates both subcutaneous and orthotopic ATCs, with a peak tumor uptake of 19.93 ± 2.17% ID per g (n = 3) and 37.20 ± 1.71% ID per g (n = 3), respectively. Fluorescent imaging with IRDye 800CW-ALT-836 facilitates the total resection of orthotopic ATCs. Moreover, 131I-ALT-836 RIT prolongs the survival of ATC-bearing mice. Taken together, TF is a promising marker for ATC and successive use of 64Cu-NOTA-ALT-836 and 131I-ALT-836 can realize precise management of ATC.

LHPP inhibits cell growth and migration and triggers autophagy in papillary thyroid cancer by regulating the AKT/AMPK/mTOR signaling pathway

In recent decades, the incidence rate of papillary thyroid carcinoma (PTC) has been rapidly increasing. However, the molecular mechanism of the physiological and pathological processes of PTC is still largely unknown. Phospholysine phosphohistidine inorganic pyrophosphate phosphatase (LHPP) is a tumor suppressor and exerts anti-tumor effect in several human cancers, while the role and underlying mechanism of LHPP in PTC remain vague. In this study, we firstly evaluated the roles of LHPP in PTC and explored its underlying mechanism. Using clinical tissue samples, we detected the level of LHPP in PTC tissues and in matched adjacent normal tissues. Lower level of LHPP was found in PTC tissues than in matched adjacent normal tissues. Similar LHPP expression pattern was found in PTC cell lines when compared with that in normal human thyroid follicular epithelial cells. Then, we over-expressed LHPP in three PTC cell lines and results showed that ectopic LHPP expression consistently reduced cell viability, proliferation, and migration and triggered cell autophagy. Furthermore, over-expression of LHPP inhibited the activation of the AKT/mTOR pathway and promoted the AMPK signaling pathway. In addition, the activation of AKT/mTOR and inhibition of AMPK signaling pathways restored the role of ectopic LHPP expression in PTC cell lines, indicating that LHPP exerts its anti-tumor activity through regulating the AKT/AMPK/mTOR pathway. Ultimately, we illustrated that ectopic LHPP expression inhibited PTC tumor growth in vivo. In conclusion, we revealed that LHPP has an anti-tumor effect in PTC and indicated that LHPP might serve as an effective diagnostic and therapeutic target for PTC.

Polymer Nanoformulation of Sorafenib and All-Trans Retinoic Acid for Synergistic Inhibition of Thyroid Cancer

Part of differentiated thyroid cancer will relapse or develop into dedifferentiated thyroid cancer after standard therapy, such as surgery or radionuclide therapy. Sorafenib (SOR) is recommended for the treatment of advanced or radioiodine-refractory thyroid cancer. The monotherapy using SOR is often hampered by its modest efficacy, serve systemic toxicity, and high occurrence of drug resistance. In order to enhance the antitumor effect of SOR and reduce its side effects, SOR and all-trans retinoic acid (ATRA), a differentiation-promoting drug, were loaded into poly(ethylene glycol)-poly(lactide-co-glycolide) (PEG-PLGA) polymer micelles in this study. The drug-loaded micelles, PM/(SOR+ATRA), exhibited relatively slow drug release and effective cell uptake. Compared with other treatment groups, the PM/(SOR+ATRA) treatment group showed the most significant antitumor effect and minimal systemic toxicity toward the FTC-133 thyroid cancer-bearing BALB/c nude mouse model. Immunofluorescence analysis confirmed that PM/(SOR+ATRA) could significantly promote apoptosis and re-differentiation of tumor cells. All the results demonstrated that polymer micelles loaded with SOR and ATRA could treat thyroid cancer more effectively and safely.