Fig. 5

PTC-209 impaired colony and tumorsphere formation, and reduced the percentage of ALDH1⁺ and stemness markers expression in HNSCC cells. a The colony formation efficiency was pronouncedly reduced in cells pretreated with PTC-209 (10 μM) as compared to vehicle-treated cells. b The first and secondary rounds of tumorsphere formation was impaired in cells pretreated with PTC-209 (10 μM) as compared to vehicle-treated cells. Scale bar: 50 μm. The percentages of ALDH1⁺ subpopulation in Cal27 (c) and FaDu (d), which was enriched with putative CSCs, were significantly decreased after PTC-209 (10 μM ,48 h) as measured by ALDEFLUOR assay. e The expression of several CSCs markers was downregulated in PTC-209-treated cells as compared to vehicle-treated cells. Data showed here are mean ± SD from three independent experiments, *p < 0.05, **p < 0.01, Student’s t test and ANOVA analyses