DKK1 and lung cancer: To validate the results of the RNA-seq analysis, quantitative RT-PCR analysis was performed on five selected genes, AREG, EREG, FOSL1, DKK1, and MYC, which were closely correlated with lung cancer development and were downregulated by TSPX-overexpression in both A549 and SK-MES-1 cells (Figure 4C, arrows) [45,46,47,48,49,50,51,52,53,54,55].