Betulinic acid is an effective CD97 inhibitor in the human medullary thyroid carcinoma cell line MTC-SK

4238 Introduction: The heterodimeric CD97 protein is a member of the EGF-TM7 family of class II seven-transmembrane (7TM) receptors of 75-90 kD and structurally related to the secretin receptor family. CD97 is expressed on leucocytes, lymphocytes and in cells of the hematopoietic system and serves as a dedifferentiation marker in thyroid carcinogenesis. Due to the interaction with its ligand CD55, CD97 is involved in carcinoma cell spread and metastasis. Aim and Objectives: We investigated the regulation of CD97 under stimulation with 1μM all-trans-retinoic acid (RA), 3mM sodium butyrate (SB) and 2mM betulinic acid (BA) in the human MTC cell line MTC-SK by FACS analysis and real time PCR. The CD97 transcript of the unstimulated control was set to 100%. Results: The CD97 mRNA and protein expression remained still constant after 24h with and without RA, SB and BA. A significant decrease of CD97 mRNA/ protein expression was observed after 48 hours and continued after 72 hours. We observed a stronger downregulation of CD97 after BA treatment (48%) than under the influence of RA or SB ( both