Chemotherapy sensitivity assays of SP and non-SP cells. Growth inhibition effect of TSA on sorted SP, non-SP cells, and unsorted HeLa cells. After 72 h of TSA treatment at various concentrations, unsorted HeLa cells and non-SP cells showed substantially suppressed growth in a dose-dependent manner, whereas SP cells were unaffected. Data are presented as the means of three separate experiments, each performed in triplicate. *P < 0.01, t-test.