Fig. 4

Collagen XIII expression enhances cancer cell stemness. a Quantification of mRNA levels of Col13 in primary tumors (n = 11) and tumorsphere (n = 15). Data are presented as the mean ± s.e.m.; * p < 0.05. b Phase images and quantification data showed tumorshpere formation in control and Col13^−/− MDA-MB-231 cells; n = 5; *** p < 0.001. Scale bar: 200 μm. c Phase images and quantification data showed mammosphere formation in control and Col13-expressing MCF-10A cells; n = 6; *** p < 0.001. Scale bar: 200 μm. d. Cell detachment induced apoptosis was quantified in control and Col13-expressing cells. Cells were cultured with 0.5% methyl cellulose in suspension for 24 h to induce anoikis before the analysis. Cell surface phosphatidylserine was analyzed by annexin-V and followed by flow cytometry analysis. Early apoptosis was quantified with bar graph; n = 3; ** p < 0.01. e Western blot analyzing PARP-cleavage in control and Col13-expressing MCF-10A cells. Cells were treated as described in d before the analysis. f Cell detachment induced apoptosis was quantified in control and Col13^−/− MDA-MB-231 as described in d. Data are presented as the mean ± s.e.m.; n = 3; *** p < 0.001