LGR4 and lung cancer: Using human lung cancer databases (Gyorffy et al. 2013), we next queried for mRNA expression of RANK; expression of its ligand, RANKL; expression of OPG, a soluble molecular decoy for RANKL/RANK (Simonet et al. 1997); and expression of LGR4, a recently reported RANKL receptor that can counteract RANK activation and hence functions as a membrane-bound negative regulator (Luo et al. 2016).