CD40 and cancer: CD40 and CEACAM5 were the top DCGs in the lung adenocarcinoma group, and both play important roles in cancer biology (Blumenthal et al., 2005; Govindan et al., 2009; Zheng et al., 2011; Rakhmilevich et al., 2012; Creelan et al., 2013; Moran et al., 2013).