SPHK1 and lung adenocarcinoma: Among all the 21 prognostic genes, 14 (e.g., AQP3, BIRC5, C5AR1, HMOX1, IL32, IL6ST, MIF, MMP12, PLAUR, PMAIP1, RAC1, SMAD6, SPHK1, USP7) have been reported to be served as a prognostic biomarker or suggested to be a novel therapeutic targets for lung adenocarcinoma [53–67].