Side population and tumor spheroid analysis of SCC-1, SCC-1-Erl-R and SCC-1-Gef-R cells. (A) Side population (SP) analysis of SCC-1, SCC-1-Erl-R and SCC-1-Gef-R cells. (B) Quantification of spheroids generated per well. 6000 cells were seeded in each well of 6 well plates and spheroid generation was quantified after 15 days. Resistant sublines generated a significantly higher number of spheroids (p-value < 0.05). Each data point represents the mean of two independent experiments. The error bars represent s.e.m. (n = 3).