CAR-T cells Targeting Thyroid-stimulating Hormone Receptor (TSHR) Demonstrate Safety and Potent Preclinical Activity Against Differentiated Thyroid Cancer

Background Differentiated thyroid cancer (DTC) is usually very treatable and is often cured with surgery and, if indicated, follow with radioactive iodine (RAI) and long-term thyroid-stimulating hormone (TSH) suppression with levothyroxine. Unfortunately, locoregional relapse and distant metastases occur in up to 20% at ten years; those relapsed or distant metastatic thyroid cancer is relatively uncommon compare to other cancers, cytotoxic chemotherapies provided low response rates, and two-thirds of cases became RAI refractory (RAI-R). New therapy options for local-regional relapsed or distant metastases thyroid cancer are desperately needed. Chimeric antigen receptor T cells (CAR-T) have been demonstrated remarkable efficacy in hematological cancers but have not yet translated in treating solid tumors. The significant hurdles limiting CAR-T therapy were due to a paucity of differentially expressed cell surface molecules on solid tumors that can be safely targeted. Here, we present thyroid-stimulating hormone receptor (TSHR) as a putative target for CAR-T therapy of DTC. Methods We undertook a large-scale screen on thyroid cancer tissues and multiple internal organs through bioinformatical analysis and immunohistochemistry to date TSHR expression. Using three previously described mAb, we generate three third-generation CAR-Ts. We tested anti-TSHR CAR-T in vitro activity by T-cell function assay and killing assay. Then we tested pre-clinical therapeutical efficacy in a xenograft mouse model of DTC and analyzed mice’s physical conditions and histological abnormalities to evaluate anti-TSHR CAR-T’s safety. Results TSHR is highly and homogeneously expressed on 90.8%(138/152) of papillary thyroid cancer, 89.2% (33/37) of follicular thyroid cancer, 78.2% (18/23) of the cervical lymph node metastases, and 86.7% of locally recurrent or metastasis lesions with RAI-R disease. We develop three novel anti-TSHR CAR-T from mAb M22, K1-18, and K1-70, all three CAR-Ts mediate significant anti-tumor activity in vitro. Among these, we demonstrate that K1-70 CAR-T can have therapeutical efficacy in vivo, and no apparent toxicity has been observed. Conclusion TSHR is a latent target antigen of CAR-T therapy for DTC. Anti-TSHR CAR-T has strong therapeutical efficacy in vivo while without prominent adverse events. Anti-TSHR CAR-T could represent an exciting therapeutic option for patients with specific local-regional relapsed or distant metastases thyroid cancer and should be tested in carefully designed clinical trials.