MKI67 and neoplasm: As seen in Figs. 2 and 4b-c, CK19 antibodies undoubtedly mark only the epithelial tumour cells (Panc1, HPAFII) but not the hPSCs, thus making it possible to separate the two cell types in the co-cultures and to determine their proliferation by MKI67 double-staining (Figs. 2 and 4b, d).