Abstract 5859: Circulating myeloid-derived suppressor cells (MDSC) are increased and correlated with immunosuppression, systemic inflammation and malnutrition in patients with anaplastic thyroid cancer

Abstract Anaplastic thyroid cancer (ATC) is one of the most aggressive neoplasm in humans. Myeloid-derived suppressor cells (MDSC) contribute to the negative regulation of immune responses in cancer and are reported to be further increased in patients who immune checkpoint inhibitor is not effective. In order to investigate the pathophysiology of thyroid cancer, peripheral blood mononuclear cells (PBMC) were obtained from 49 patients with thyroid cancer, 18 with non-cancerous thyroid diseases and 22 healthy volunteers. MDSC were detected by flow cytometry (CD14-CD11b+CD33+) and Tcell-mediated immune response is measured by stimulation index (SI) of PHA-stimulated proliferation of lymphocytes. CRP (C-reactive protein) levels were used as inflammatory and serum albumin levels were used as nutritional parameters. MDSC levels were significantly higher in thyroid cancer than in healthy volunteers and non-cancerous patients, and those of ATC was highest among patients with thyroid cancer. SI were significantly lower, and CRP levels were higher in ATC than other histological types of thyroid cancer. The patients with thyroid cancer were divided into 2 groups with the average level of MDSC (1.578 %PBMC) in patients with thyroid cancer. CRP levels were significantly higher, serum albumin levels were significantly lower in high MDSC group than in low MDSC group. These data indicate that MDSCs are increased in patients with ATC. Furthermore, these patients exhibited immunosuppression, enhanced chronic inflammation and nutritional impairment. Citation Format: Masahiko Shibata, Shinichi Suzuki, Koji Kono, Seiichi Takenoshita. Circulating myeloid-derived suppressor cells (MDSC) are increased and correlated with immunosuppression, systemic inflammation and malnutrition in patients with anaplastic thyroid cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2025; Part 1 (Regular Abstracts); 2025 Apr 25-30; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2025;85(8_Suppl_1):Abstract nr 5859.