ESR1 and breast cancer: To determine whether the observed effects of ENDX on PKCβ1 degradation and AKTSer473 phosphorylation inhibition are dependent on the presence of ERα, we additionally evaluated ENDX effects on PKCβ1 degradation and AKTSer473 phosphorylation in the ER negative (ER-) MDAMB231 breast cancer cells and nonbreast HEK293F cells, a human embryonic kidney cell line, both of which express higher amounts of PKCβ1 compared to ERα+ MCF7AC1 cells (Supplementary Fig. 5a).