Although si-NPs targeting Mcl-1 remain to be tested in vivo, Mcl-1-specific inhibition in cell culture-based models dramatically reduced Mcl-1 expression in both LTED and parental breast cancer cells (Figs. 4a and  5b), increasing tumor cell killing in cells that have developed resistance to current standard of care therapies. The gene discussed is MCL1; the disease is breast carcinoma.