Figure 1. Cancer stem-like properties of ALDH-high ME180 cells.

(A) In vitro tumorigenic capacity and self-renewal activity of cervical cancer cells according to ALDH-activity. ME180 cells that had been labeled with the Aldefluor kit were sorted using a FACScan flow cytometer. Then, ALDH-high and ALDH-low ME180 cells (1.5 × 10³ cells) were separately plated in 60 mm ultra-low attachment surface dishes and cultured for 2 weeks in the serum-free medium. The tumorigenic capacity and self-renewal activity of the cells were assessed by sphere formation assays (i), Representative photos of the spheres formed by the ALDH-high and ALDH-low cells (phase-contrast microscopy, magnification: ×400). (ii) The number of spheres counted from 5 consecutive passages (n = 3, p < 0.05, two-sided Student’s t test). (B) In vitro tumorigenic capacity of cervical cancer cells according to ALDH-activity. ME180-high and ME180-low cells (1 × 10²) were separately cultured in 60 mm dishes in the presence of 10% FBS for 3 weeks. Then, the colonies were stained with 0.5% crystal violet and the numbers of colonies were counted. (i) Representative photos of colonies. (ii), The numbers of colonies counted (Bars SD, n = 3. p < 0.05, two-sided Student’s t test). (C) In vivo tumorigenic capacity of cervical cancer cells according to ALDH-activity. ALDH-high or low ME180 cells were subcutaneously inoculated into NOD/SCID mice (100 cells; 1,000 cells; 10,000 cells). Eight weeks after the inoculation procedure, the numbers of successful tumor initiations for each condition were counted and shown (n = 4). (D) Differentiation capacity of cervical cancer cells according to ALDH-activity. (i) Population of ALDH-high cells. ALDH-high and ALDH-low ME180 cells were separately cultured in the presence of 10% FBS for 3 days in vtiro and then assessed using the Aldefluor assay (Bars SD, n = 5, p < 0.01, two-sided Student’s t test). (ii) Representative dot plots were shown.