Late-passage GG3.1 cells are more homogenously undifferentiated and have higher levels of pluripotency factor expression. (A) Comparison of Sox2 stained cells in (A) EP, (B) LP and (C) ESC cultures. LP and ESCs form tight clusters of uniformly Sox2+ cells. Under the same conditions, EP cells readily generate Sox2- cells as indicated by DAPI. (D) Real-time qRT-PCR reveals that mRNA expression for several pluripotency factor genes is elevated towards ESC levels in LP GG3.1 cells. Nanog expression remains significantly lower. Values are mean ± SD for 2-3 independent samples. Bars indicate 100 μm. *P < 0.05, **P < 0.001.