Fig. 4. POSTN secreted by CAFs promotes the CSC-like phenotype and tumor initiation in HNSCC by interacting with PTK7.
a After being starved with serum-free DMEM overnight, HN6 shNC and shPTK7 were exposed to rhPOSTN for 0 or 72 h, and the expression of the CSC markers CD166, SALL4, CD271, CD90, OCT-4, ALDH1, SOX2, and NANOG was analyzed by RT-PCR. **p < 0.01, ***p < 0.001, ****p < 0.0001, based on Student’s t-test. b After being starved with serum-free DMEM overnight, HN6 shNC and shPTK7 were exposed to rhPOSTN for 0 or 72 h, and then their sphere-forming capacity was assessed. The results are shown as the mean ± SD. **p < 0.01, ***p < 0.001, based on Student’s t-test. Scale bar: 20 μm. c After being starved with serum-free DMEM overnight, HN6 shNC and shPTK7 were exposed to rhPOSTN for 0 or 72 h, and then colony formation assay was performed. The results are shown as the mean ± SD. **p < 0.01, ***p < 0.001, based on Student’s t-test. d After being starved with serum-free DMEM overnight, HN6 shNC and shPTK7 were exposed to erlotinib at different concentrations for 72 h. The IC50 of erlotinib was evaluated on the basis of cell viability using CCK8 assay. e After being starved with serum-free DMEM overnight, HN6 shNC and shPTK7 were exposed to rhPOSTN for 0 or 72 h, and then proliferation assay was performed. The results are shown as the mean ± SD. *p < 0.05, **p < 0.01, based on Student’s t-test. f After being starved with serum-free DMEM overnight, HN6 shNC and shPTK7 were exposed to rhPOSTN for 0 or 72 h, and then scratch-wound-healing assay was performed. The results are shown as the mean ± SD. **p < 0.01, ***p < 0.001, based on Student’s t-test. Scale bar: 40 μm. g, h After being starved with serum-free DMEM overnight, HN6 shNC and shPTK7 were exposed to rhPOSTN for 0 or 72 h, and then migration and invasion assay was performed. The results are shown as the mean ± SD. **p < 0.01, ***p < 0.001, ****p < 0.0001, based on Student’s t-test. Scale bar: 30 μm