Effect of DSS1 knockdown in the breast cancer cell lines MCF7 and MDA-MB-231. DSS1 knockdown was carried out in MCF7 and MDA-MB-231 cells by treatment with siDSS1. Two siDSS1 sequences targeting two separate regions of the sequence showed similar knockdown efficiencies and similar effects on the proliferation of MCF7 and MDA-MB-231 cells (Figure S4). (A) The proliferation rates of siCtrl- and siDSS1-(a)-treated cells were assessed by MTT assay (left) and cell counting (right). (B) Cell cycle profiles of the transfectants were examined on day 3 and day 5 of culture (right; day 5 profile). The proportions of dead cells were measured by the counting sub-G1 fraction and are compared in the graph (right). The experiments were carried out more than three times, and the results are shown as an average. Statistical significance was assessed by Student’s t-test, with *P < 0.05 and **P < 0.01.