Compared to 2D monolayers, there was a twofold increase in the expression of the stemness-related transcription factors SOX2 and KLF4 in PA-ECM cultures (Fig. 4a) and a much higher proportion of CD133 + /CXCR4 + cells than in spheres or organoids, which falls in the range of matched PDX tumours (Fig. 4b; Supplementary Fig. 3a). Here, CXCR4 is linked to neoplasm.