DKK1 and lung adenocarcinoma: TCGA pan-cancer analyses showed that higher DKK1 level was significantly associated with the poor prognosis of adrenocortical carcinoma (ACC) (p < 0.01), HNSC (p < 0.01), LAML (p = 0.046), lung adenocarcinoma (LUAD) (p < 0.01), mesothelioma (MESO) (p < 0.01), PAAD (p < 0.01), and STAD (p < 0.01) (Figures 3A–G), and lower DKK1 expression was significantly associated with the poor prognosis of ESCA (p = 0.016) and kidney renal clear cell carcinoma (KIRC) (p = 0.024) (Figures 3H,I).