Effects of chemotherapy on the sphere forming ability of HEY cells. (A) The sphere-forming assay was performed on low attachment plates as described in the Material and methods section. The total number of spheres was counted in the 24 well plates after 21 days as described in the Methods and materials. The experiment was performed three times in triplicate. Images are representative of a section of a 24 well plate. Black arrows indicate disaggregating cells in control spheres in 21 days. Magnification 200x; scale bar = 10 µM. (B) Significantly different from control untreated cells indicated by *P<0.05, *** P<0.001.