Figure 1: STO/EL cell establishment. (A) Effect of LIF concentration on maintaining ES cell cultures in an undifferentiated state. 129/Sv cells were cultured in various LIF concentrations (0–1,000 U/ml) on MEF (black column), STO (white column) and STO/E (gray column) feeder layers. ES cells were re-plated onto a MEF feeder layer and cultured in medium containing 1 × 103 U/ml LIF for 2 d. Then, AP-positive ES colonies were counted. (B) RT-PCR analysis of E-cadherin and LIF expression in STO/EL cells. (C) Western blot analysis of E-cadherin and LIF expression in STO/EL cells. (D) Effect of CM on the number of AP-positive ES cell colonies. 129/Sv cells were cultured on a MEF feeder layer in CM prepared from the various feeder layers. The control experiment was performed by culturing 129/Sv cells on a MEF feeder layer in ES/iPS medium containing 1 × 103 U/ml LIF. Experiments were performed in triplicate, and data are the means ± SD, *P<0.05.