Fig. 1

CRC tumor cells can recruit fibroblasts to tumor buds. a Representative H&E images of human CRC tissue at the invasive front without (the upper panel) or with (the lower panel) tumor budding. The red triangles indicate the tumor buds. Data, n = 195. Scale bar, 50 μm. b Representative α-SMA, CD90, and FAP IHC staining images of human CRC tissue at the invasive front without (the upper panel) or with (the lower panel) tumor budding. The red triangles indicate the tumor buds. Data, n = 17. Scale bar, 50 μm. c Representative E-cad, VIM, and α-SMA IF images of human normal colorectal fibroblast cell line (CCD-18Co) and human primary normal colorectal fibroblast (NF1). Human CRC tumor cell line SW620 is the positive control for E-cad and the negative control for VIM and α-SMA. Scale bar, 20 μm. d Model diagram of recruitment assay of CRC tumor cells to fibroblasts. e Recruitment assay showing the recruitment ability of medium (Med), human normal colorectal epithelial cell line (FHC) and eight human CRC tumor cell lines (LS174T, RKO, DLD-1, Caco2, SW620, HCT-8, HCT116, HCT-15) to CCD-18Co or human primary normal colorectal fibroblast (NF1). Scale bar, 100 μm. Quantification of cell numbers of recruited fibroblasts is shown in the upper panel. Data, mean ± SD; n = 5. f Representative morphology images of tumor formation in the mouse caecum (the upper line), and H&E images of normal mouse caecum and tumor tissue in the mouse caecum (the lower two lines). The red arrows indicate the tumors in the mouse caecum. Data, normal, n = 5; tumor, n = 5. Scale bar, 50 μm. E-cad, E-cadherin; VIM, vimentin. ns, no significance; *, P < 0.05; **, P < 0.01; ***, P < 0.001 by two-tailed Student’s t test (e)