Fig. 6

Hypoxia upregulates EUDAL transcription via HIF-1α, induces EGFR phosphorylation and leads to activation of STAT3 signaling. a ChIP-qPCR results indicated that HIF-1α precipitants showed the occupancy of HIF-1α on HRE4 (n = 3). b Luciferase reporter assays showed HIF-1α could directly activate EUDAL transcription (n = 3). c ChIP-qPCR showed a higher combination of HIF-1α on HRE4 in CAL-27 and HN30 (bars, left y-axis), which coincided with higher expression fold-change in these cells (dotted line, right y-axis). d Representative immunoblot images of indicated protein levels. e Upper: Knockdown of EUDAL in CAL-27 cells inhibited phosphorylation of both EGFR and STAT3. Lower: Hypoxia treatment combined with ectopic expression of EUDAL can simultaneously lead to phosphorylation of EGFR and STAT3 in HN4 cells. Data were from representative results of at least three independent experiments. Data are represented as mean ± SD. ns no significance; ****P < 0.000 1; one-way ANOVA with Turkey’s Honestly Significant Difference test (b). HRE4 Del-mut, a deletion mutant lacking the −525 to −551 bp segment in the EUDAL promoter region; wt wild-type, EUDAL Del-mut an lncRNA mutant with an EGFR-binding motif deletion (Δ254–305 nt)