NRG1 and carcinoma: Based on these results, we supplemented the G1 medium with NRG1 (20 ng ml–1) along with other factors that are beneficial for ex vivo carcinoma cultures, namely FGF3, FGF7, FGF8, FGF9, FGF10, noggin, gremlin-1, SB431542 (activin–BMP–TGFβ pathway inhibitor) and Y27632 (ROCK inhibitor)22,23.