To test whether the ssDNA is associated with enhanced cGAS-STING activity, MDA-MB-231 and SUM159 cells were cultured in normal or serum-free media in the presence and absence of the pharmacological compound RU.521, a potent investigational inhibitor of cGAS to be used for treating inflammatory symptoms of autoimmune diseases (13, 14). Here, CGAS is linked to autoimmune disease.