ESR1 and breast cancer: However, tumor growth was blocked using the combination of RAD001 and ABT-263 throughout the 16-day treatment period (N = 7), confirming that mTORC1 inhibition restrained Mcl-1 upregulation following Bcl-2/Bcl-xL inhibition, increasing the therapeutic effect of ABT-263 in ERɑ+ breast cancer xenografts in vivo.