OR14-05 Taking Advantage Of The Interleukin-6-Biology In Differentiated Thyroid Cancer To Stimulate Sodium Iodide Symporter (NIS)-mediated Iodide Uptake In Engineered Mesenchymal Stem Cells

Abstract Disclosure: V.F. Koehler: Speaker; Self; Sanofi. L. Drago: None. M. Hageneier: None. C. Kitzberger: None. N. Schwenk: None. K. Shehzad: None. Y. Han: None. J. Nagarajah: None. P.J. Nelson: None. C. Spitzweg: None. Based on its role in mediating iodide uptake from the blood into thyroid follicular cells, the sodium iodide symporter (NIS) provides the basis for the use of radioiodine (RAI) for diagnostic imaging and therapy of differentiated thyroid cancer (DTC). The loss of functional NIS expression leads to RAI-refractory disease. The tumor-selective delivery of NIS as a transgene using mesenchymal stem cells (MSCs) represents a therapeutic strategy for RAI-refractory DTC. Interleukin-6 (IL-6) is a potent cytokine omnipresent in the inflammatory microenvironment of many solid tumors thought to sustain and promote tumor proliferation, invasion and angiogenesis, and contribute to immune escape. With the aim to selectively drive NIS-transgene expression in the context of DTC, MSCs were stably transfected with a NIS-expressing plasmid controlled by the human IL-6-promoter (IL-6-NIS-MSCs). This approach may represent a new tumor-target gene therapy for RAI-refractory DTC. To confirm the inducibility of the IL-6 promoter in IL-6-NIS-MSCs, the murine cytokines (IL-1 β, TNF-α, IFN-γ) were applied to stimulate promoter activation. The resulting functional NIS expression was analyzed by an 125Iuptake assay in vitro. The invitro IL-6 concentration in the papillary thyroid cancer cells BCPAP and K1either co-cultured with or without IL-6-NIS-MSCs was determined by ELISA. Subsequently, IL-6-NIS-MSCs were subjected to a gradient of serum free tumor cell conditioned medium (CM) and serum free unconditioned medium and its migratory response was assessed using 3D live-cell imaging migration assay.IL-6-NIS-MSCs treated with IL-1 β, IFN-γ and TNF-α revealed an increased125I uptake as compared to single stimulation studies. Asa basis for a future in vivo application, incubation of IL-6-NIS-MSC with CM of BCPAP and K1 containing diverse tumor-derived factors or directly co-cultured with these cell lines resulted in significant increase of 125I uptake as compared to untreated cells. The ELISA assay revealed high levels of IL-6 secretion in K1-CM andIL-6-NIS-MSCs co-cultured with BCPAP and K1, while a lower concentration was measured in BCPAP-CM. IL-6-NIS-MSCssubjected to a gradient between a serum free tumor cell-CM and serum free unconditioned medium, showed an increased migration towards tumor cell-CM over a period of 24 h. Taken together, our results indicate the feasibility of targeting IL-6 induction in the inflammatory-rich tumor environment of RAI-refractory DTC to re-establish functional NIS expression using engineered MSCs as delivery vehicles. These data also show us the potential of cytokine-induced promoters for driving NIS transgene expression for a novel imaging and theranostic NIS gene approach. Presentation: Friday, June 16, 2023