SOX2 and embryonal carcinoma: Starting with nuclear extracts prepared from 400 L of a pluripotent embryonal carcinoma (EC) cell line NTERA-2 (NT2), we used the reconstituted transcription system supplemented with recombinant XPC complex, purified OCT4, SOX2, and a modified human Nanog template, to purify SCC-A over six successive chromatographic columns resulting in >30,000-fold increase in specific activity (Figure 1A).