Identification and isolation of SP cells from human anaplastic thyroid cancer BHT101 and 8305C cell lines. (A) Treatment of Hoechst 33342 dye followed by flow cytometric analysis separated the SP cells from MP cells, which are represented in the box. (B) BHT101 and 8305C cells were labeled with 5 µg/ml Hoechst 33342 either alone or in combination with 100 µg/ml verapamil. The proportion of SP cells was analyzed by flow cytometry. *P<0.05. (C) Protein level of cancer stem cell-associated markers in 8305C-SP and 8305C-MP cells. SP, side population; MP, main population; ALDH, aldehyde dehydrogenase; CD, cluster of differentiation; ABCG2, ATP-binding cassette subfamily G member 2; ABCB1, ATP-binding cassette subfamily B member 1.