As triple negative breast cancer constitutes a highly heterogeneous cell population, the effect of SMC1 suppression by SMC1 siRNA (50 nM) combined with 0–100 μM ABT-888 was tested in both basal-like (MDA-MB-468, HCC 1937), and mesenchymal stem like (MDA-MB-231, MDA-MB-436) subtypes of TNBC cells. The gene discussed is SMC1A; the disease is triple-negative breast carcinoma.