Roles and new Insights of Macrophages in the Tumor Microenvironment of Thyroid Cancer

A zebrafish xenotransplant model of anaplastic thyroid cancer to study tumor microenvironment and innate immune cell interactions in vivo

Anaplastic thyroid cancer (ATC) is of the most aggressive thyroid cancer. While ATC is rare, it accounts for a disproportionately high number of thyroid cancer-related deaths. Here, we developed an ATC xenotransplant model in zebrafish larvae, where we can study tumorigenesis and therapeutic response in vivo. Using both mouse (T4888M) and human (C643)-derived fluorescently labeled ATC cell lines, we show these cell lines display different engraftment rates, mass volume, proliferation, cell death, angiogenic potential, and neutrophil and macrophage recruitment and infiltration. Next, using a PIP-FUCCI reporter to track proliferation in vivo, we observed cells in each phase of the cell cycle. Additionally, we performed long-term non-invasive intravital microscopy over 48 h to understand cellular dynamics in the tumor microenvironment at the single-cell level. Lastly, we tested two drug treatments, AZD2014 and a combination therapy of dabrafenib and trametinib, to show our model could be used as an effective screening platform for new therapeutic compounds for ATC. Altogether, we show that zebrafish xenotransplants make a great model to study thyroid carcinogenesis and the tumor microenvironment, while also being a suitable model to test new therapeutics in vivo.

Research progress of immunotherapy against anaplastic thyroid cancer

Anaplastic thyroid cancer (ATC) is the most aggressive type of thyroid cancer. While ATC is rare, its mortality is high. Standard treatments, such as surgery, radiotherapy, and chemotherapy, have demonstrated limited efficacy in managing ATC. However, the advent of immunotherapy has significantly improved the prognosis for patients with ATC. Immunotherapy effectively targets and eliminates tumor cells by using the power of the body's immune cells. The neoantigen is an atypical protein generated by somatic mutation, is exclusively observed in neoplastic cells, and is devoid of central tolerance. Neoantigens exhibit enhanced specificity towards tumor cells and display robust immunogenic properties. Currently, neoantigen therapy is primarily applied in immune checkpoint inhibitors and cellular immunotherapy, encompassing adoptive immunotherapy and tumor vaccines. This study discusses the mechanism, tumor microenvironment, clinical trials, adverse events, limitations and future directions associated with ATC immunotherapy.

Tumor-associated macrophages as a potential therapeutic target in thyroid cancers

Macrophages are important precursor cell types of the innate immune system and bridge adaptive immune responses through the antigen presentation system. Meanwhile, macrophages constitute substantial portion of the stromal cells in the tumor microenvironment (TME) (referred to as tumor-associated macrophages, or TAMs) and exhibit conflicting roles in the development, invasion, and metastasis of thyroid cancer (TC). Moreover, TAMs play a crucial role to the behavior of TC due to their high degree of infiltration and prognostic relevance. Generally, TAMs can be divided into two subgroups; M1-like TAMs are capable of directly kill tumor cells, and recruiting and activating other immune cells in the early stages of cancer. However, due to changes in the TME, M2-like TAMs gradually increase and promote tumor progression. This review aims to discuss the impact of TAMs on TC, including their role in tumor promotion, gene mutation, and other factors related to the polarization of TAMs. Finally, we will explore the M2-like TAM-centered therapeutic strategies, including chemotherapy, clinical trials, and combinatorial immunotherapy.

HHV-6A Infection of Papillary Thyroid Cancer Cells Induces Several Effects Related to Cancer Progression

Recent studies have shown that thyrocytes are permissive to HHV-6A infection and that the virus may contribute to the pathogenesis of autoimmune thyroiditis. Thyroid autoimmune diseases increase the risk of papillary cancer, which is not surprising considering that chronic inflammation activates pathways that are also pro-oncogenic. Moreover, in this condition, cell proliferation is stimulated as an attempt to repair tissue damage caused by the inflammatory process. Interestingly, it has been reported that the well-differentiated papillary thyroid carcinoma (PTC), the less aggressive form of thyroid tumor, may progress to the more aggressive follicular thyroid carcinoma (FTC) and eventually to the anaplastic thyroid carcinoma (ATC), and that to such progression contributes the presence of an inflammatory/immune suppressive tumor microenvironment. In this study, we investigated whether papillary tumor cells (BCPAP) could be infected by human herpes virus-6A (HHV-6A), and if viral infection could induce effects related to cancer progression. We found that the virus dysregulated the expression of several microRNAs, such as miR-155, miR-9, and the miR-221/222 cluster, which are involved in different steps of carcinogenesis, and increased the secretion of pro-inflammatory cytokines, particularly IL-6, which may also sustain thyroid tumor cell growth and promote cancer progression. Genomic instability and the expression of PTEN, reported to act as an oncogene in mutp53-carrying cells such as BCPAP, also increased following HHV-6A-infection. These findings suggest that a ubiquitous herpesvirus such as HHV-6A, which displays a marked tropism for thyrocytes, could be involved in the progression of PTC towards more aggressive forms of thyroid tumor.

METTL3 inhibition induced by M2 macrophage-derived extracellular vesicles drives anti-PD-1 therapy resistance via M6A-CD70-mediated immune suppression in thyroid cancer

The treatment options for advanced papillary thyroid cancer (PTC) and anaplastic thyroid cancer (ATC) refractory to standard therapies are limited. Although anti-PD-1 therapy has a manageable safety profile and has been effective in a small percentage of patients with advanced PTC and refractory ATC, the majority of the patients either do not respond or develop resistance to anti-PD-1 therapy. N6-methyladenosine (m6A) modification is a critical determinant of the complexity of the tumor microenvironment (TME). However, it is unclear whether and how m6A modification in tumor cells shapes the immune landscape of PTC and ATC. In this study, we performed bulk and single cell RNA sequencing analysis of PTC and ATC tissues, and found that low METTL3 expression not only correlated to poor response to immune checkpoint blockade (ICB) but was also associated with increased TNF family-related ligand-receptor interactions in the immunosuppressive Tregs and exhausted T cells. Furthermore, overexpression of METTL3 in PTC and ATC cells enhanced the efficacy of anti-PD-1 therapy in a peripheral blood mononuclear cell humanized NCG (huPBMC-NCG) mouse model. Mechanistically, M2 macrophage-derived extracellular vesicles (M2 EVs) inhibited METTL3 expression in PTC and ATC cells via miR-21-5p. Downregulation of METTL3 promoted demethylation of CD70 mRNA, which prevented YTHDF2-mediated degradation of the transcripts. The stabilization of CD70 mRNA, and the subsequent upregulation in CD70 protein levels increased the abundance of the immunosuppressive Tregs and terminally exhausted T cells, thereby inducing resistance to anti-PD-1 therapy. Furthermore, blocking CD70 using cusatuzumab, a high-affinity monoclonal antibody, reversed the anti-PD-1 therapy resistance induced by M2 EVs in vivo. Finally, we demonstrated that METTL3 expression negatively correlated with CD70 expression and M2 macrophages and Tregs infiltration in PTC and ATC tissues. Our findings provide new insights into developing novel therapies for advanced PTC and ATC.

Can Routine Laboratory Tests Be Suggestive in Determining Suspicions of Malignancy in the Case of Thyroid Nodules?

Background and objectives: Thyroid nodules are a common finding in clinical practice and can be either benign or malignant. The aim of this study was to compare laboratory parameters between patients with malignant thyroid nodules and those with benign thyroid nodules. Materials and methods: A total of 845 patients were included, with 251 in the study group (malignant thyroid nodules) and 594 in the control group (benign thyroid nodules). Results: Our results show that there were statistically significant differences in several laboratory parameters, including FT3, FT4, ESR, fibrinogen, WBC, and lymphocyte percentage, between the two patient groups (p < 0.05). Conclusions: These findings suggest that certain laboratory parameters may be useful in differentiating between benign and malignant thyroid nodules and could aid in the diagnosis and treatment of thyroid cancer. However, further diagnostic tests such as fine-needle aspiration biopsy and imaging studies are typically required for an accurate diagnosis. Routine laboratory tests prove most effective when combined with other diagnostic methods to identify thyroid cancer. Although not conclusive on their own, these tests significantly suggest and guide physicians to suspect malignancy in thyroid nodules. This affirmative answer to our question, "Can routine laboratory tests be suggestive in determining suspicions of malignancy in the case of thyroid nodules?" aligns with the results of our study.

Advances in the molecular mechanism and targeted therapy of radioactive-iodine refractory differentiated thyroid cancer

Most patients with differentiated thyroid cancer have a good prognosis after radioactive iodine-131 treatment, but there are still a small number of patients who are not sensitive to radioiodine treatment and may subsequently show disease progression. Therefore, radioactive-iodine refractory differentiated thyroid cancer treated with radioiodine usually shows reduced radioiodine uptake. Thus, when sodium iodine symporter expression, basolateral membrane localization and recycling degradation are abnormal, radioactive-iodine refractory differentiated thyroid cancer may occur. In recent years, with the deepening of research into the pathogenesis of this disease, an increasing number of molecules have become or are expected to become therapeutic targets. The application of corresponding inhibitors or combined treatment regimens for different molecular targets may be effective for patients with advanced radioactive-iodine refractory differentiated thyroid cancer. Currently, some targeted drugs that can improve the progression-free survival of patients with radioactive-iodine refractory differentiated thyroid cancer, such as sorafenib and lenvatinib, have been approved by the FDA for the treatment of radioactive-iodine refractory differentiated thyroid cancer. However, due to the adverse reactions and drug resistance caused by some targeted drugs, their application is limited. In response to targeted drug resistance and high rates of adverse reactions, research into new treatment combinations is being carried out; in addition to kinase inhibitor therapy, gene therapy and rutin-assisted iodine-131 therapy for radioactive-iodine refractory thyroid cancer have also made some progress. Thus, this article mainly focuses on sodium iodide symporter changes leading to the main molecular mechanisms in radioactive-iodine refractory differentiated thyroid cancer, some targeted drug resistance mechanisms and promising new treatments.

TIM3 Expression in Anaplastic-Thyroid-Cancer-Infiltrating Macrophages: An Emerging Immunotherapeutic Target

Anaplastic thyroid cancer (ATC) is a clinically aggressive form of undifferentiated thyroid cancer with limited treatment options. Immunotherapy for patients with ATC remains challenging. Tumor-associated macrophages (TAMs) constitute over 50% of ATC-infiltrating cells, and their presence is associated with a poor prognosis. Consequently, the development of new therapies targeting immune checkpoints in TAMs is considered a promising therapeutic approach for ATC. We have previously shown that soluble factors secreted by ATC cells induced pro-tumor M2-like polarization of human monocytes by upregulating the levels of the inhibitory receptor TIM3. Here, we extended our observations on ATC-cell-induced xenograft tumors. We observed a large number of immune cells infiltrating the ATC xenograft tumors. Significantly, 24-28% of CD45+ immune cells were macrophages (CD11b+ F4/80+). We further showed that 40% of macrophages were polarized toward a M2-like phenotype, as assessed by CD206 expression and by a significant increase in the Arg1/iNOS (M2/M1) ratio. Additionally, we found that ATC xenograft tumors had levels of TIM3 expression when determined by RT-PCR and immunofluorescence assays. Interestingly, we detected the expression of TIM3 in macrophages in ATC tumors by flow cytometry assays. Furthermore, TIM3 expression correlated with macrophage marker expression in human ATC. Our studies show that TIM3 is a newly identified immune checkpoint in macrophages. Since TIM3 is known as a negative immune regulator, it should be considered as a promising immunotherapeutic target for ATC.

Construction of a ferroptosis-related eight gene signature for predicting the prognosis and immune infiltration of thyroid cancer

BACKGROUND

Thyroid cancer is the most common malignant tumor of the endocrine system. Most patients with thyroid cancer have a good prognosis, although a small proportion experience recurrence and metastasis and have a poor prognosis. Ferroptosis is a novel form of regulated cell death (RCD); previous studies have confirmed that ferroptosis was associated with thyroid cancer. The purpose of this study was to investigate the key ferroptosis-related genes in thyroid cancer and their relationship with prognosis and immune cell infiltration.

METHODS

In this study, 497 thyroid cancer RNA expression datasets were downloaded from the cancer genome atlas (TCGA) cohort and a prognostic risk model for eight ferroptosis-related genes (FRGs) was constructed by Lasso-Cox regression. The prognostic value of the risk model and the correlation of prognostic features with immune scores and tumor immune cell infiltration were systematically analyzed.

RESULTS

The prognostic risk model for eight FRGs (DPP4, TYRO3, TIMP1, CDKN2A, SNCA, NR4A1, IL-6 and FABP4) were constructed and validated in training and testing cohorts. Kaplan-Meier curve and receiver operating characteristic (ROC) curve analysis confirmed that that the ferroptosis-related eight gene signature had good predictive value for the prognosis of thyroid cancer (THCA) patients. Multivariate regression analysis further showed that the risk score of the prognostic model could be used as an independent prognostic factor for THCA patients. Functional enrichment analysis showed that DEGs in high risk and low risk groups were involved in immune-related biological processes and that there were significant differences in immune cell infiltration between the two risk groups.

CONCLUSION

We identified eight key genes related to ferroptosis in THCA patients. Further studies are now needed to investigate the mechanisms involved; these genes may represent clinical diagnostic and prognostic biomarkers.