The incidence of thyroid cancer has increased rapidly in recent decades (Sung et al.,2021). Differentiated thyroid carcinoma, which consists of papillary thyroid carcinoma (PTC) and follicular thyroid carcinoma (FTC), comprises 90% of thyroid cancer (Fagin and Wells Jr,2016). Meanwhile, most DTC can be effectively cured with standard surgical treatment, selective radioactive iodine (RAI) therapy, and thyroid stimulating hormone (TSH) suppression therapy (Filetti et al.,2019). However, 30% of DTC patients would experience relapse, and 10% would develop distant metastases within ten years (Mazzaferri and Jhiang,1994; Fabian and Hodge, 2021. Compounding the challenge, two-thirds of these patients would eventually develop into refractory to RAI (RAI-R) and have a 10-year overall survival of less than 10% (Schlumberger et al.,2014).

Cytotoxic chemotherapy has mostly been abandoned for treating DTC metastases due to its toxicity and limited effectiveness, while systemic treatments such as angiogenesis inhibitors and kinase inhibitors are now commonly employed (Schlumberger and Leboulleux, 2021). Patients with progressively advanced radioiodine-refractory differentiated thyroid cancer (DTC) have shown improvement in progression-free survival (PFS) after receiving anti-angiogenic multi-kinase inhibitors (MKI). However, they eventually experienced disease progression (Locati et al.,2019;Wirth et al.,2022). Currently, although some small molecule kinase inhibitors have been used for the treatment of locally-regional relapse, RAI-R DTC, and metastatic DTC, tumor progression rapidly occurs due to drug resistance and toxic side effects in a sizable proportion of patients, severely restricting their clinical use (Schlumberger et al.,2015). Therefore, effective treatments for locally-regional relapsed or distant metastatic thyroid cancer should be developed Fagin and Wells, 2016.

The TSH receptor (TSHR), a transmembrane glycoprotein receptor, belongs to a subfamily of G protein-coupled receptors and is essential for thyroid growth and function (Kleinau et al.,2013). The TSH receptor is primarily expressed in the normal thyroid follicular epithelium and exists in most DTC (Brabantet al., 1991; Tanakaet al., 2000; Daher and Rezvani, 2021. Levothyroxine administration is used to suppress the growth signal transduced by TSH-TSHR in DTC patients (Baueret al., 2005). These findings collectively support the notion that TSHR is essential for the cell growth and survival of DTC and serves as a promising target for the disease (Rowe et al., 2017). The majority of DTC patients experiencing relapse and distant metastases have undergone total or subtotal thyroidectomy, setting the stage for effective targeted therapy.

Chimeric antigen receptor (CAR)-T cell therapy has been revolutionary as it has produced remarkably effective and durable clinical responses (Sterner and Sterner, 2021). CAR-T therapy involves genetically modifying the patient’s T cells to express CARs, and these CARs are designed to recognize and target specific antigens expressed on cancer cells. By equipping T cells with CARs, CAR-T therapy enhances the immune system’s ability to identify and eliminate cancer cells (Sadelain et al.,2013) specifically. Meanwhile, The TSHR-CAR T therapy demonstrates efficacy against DTC and presents a potential postoperative systemic treatment option for patients with recurrence/metastasis or resistance to radioactive iodine therapy (Ding et al.,2022;Li et al.,2022). In addition, compared to CAR-T cell therapy, NK cell therapy has distinct advantages, such as a low rate of cytokine release syndrome (CRS) and graft-vs-host disease, as well as shorter manufacturing time and lower cost (Rafei et al.,2021). Furthermore, NK-92 cells have successfully been employed in clinical cell immunotherapy (Liu et al.,2021). Thus, in this study, we aimed to identify TSHR as a viable target on DTC tissues and investigate the efficacy of TSHR-CAR NK-92 cells against DTC both in vitro and in vivo Li et al., 2022a, Li et al., 2022b.