Fig. 4

Stem cell-like characteristics in therapy resistant variants. Mammosphere formation efficiency (MFE) of SKBR3 therapy sensitive and resistant variants was calculated by dividing the number of mammospheres formed by the number of cells seeded per well and multiplied by 100 for percentage. a Representative micrographs of mammosphere forming units. Fold changes of percentage are shown in: b MFE in gefitinib and lapatinib treated therapy sensitive cells relative to vehicle treated cells. c,d MFE in therapy resistant cells treated with (c) gefitinib or (d) lapatinib, relative to vehicle controls. e MFE of therapy resistant variants relative to therapy sensitive cells with no treatment. f Representative western blots of cancer stem cell markers integrin β3, CD133, and Nanog in SKBR3 therapy sensitive and resistant variants. N = 3 ± SEM,* = p ≤ 0.05 and,**** = p ≤ 0.001