SOX9 and cancer: Because the fusion of a cancer cell with a stem cell (or a stem-like cell) may result in CS/IC-like hybrid cells, M13HS hybrid cell clones were analyzed for CS/IC-related characteristics, including the expression of stemness factors SOX9 and SLUG, the capacity of forming colonies and mammospheres, as well as aldehyde dehydrogenase 1 (ALDH1) expression.