SPP1 and lung adenocarcinoma: In lung adenocarcinoma, claudin-1 re-expression-modulated cell growth is associated with up-regulation of cancer invasion/metastasis suppressors (e.g., connective tissue growth factor, thrombospondin 1, deleted in liver cancer 1, occludin, and ZO-1) and down-regulation of invasion/metastasis enhancers (e.g., secreted phosphoprotein 1, cut-like homeobox 1, transforming growth factor alpha, solute carrier family 2 member 3, and placental growth factor) [27].