FZD4 and cancer: Even though GPCRs are not thought to be functionally mutated and commonly expressed (i.e., they are not “genetic drivers”) in cancers, GPCRs and post-GPCR signaling mechanisms play an important role in regulating cellular functions integral to the hallmarks of cancer (e.g., growth/proliferation, metabolism, death/apoptosis, ion and nutrient transport, and migration; Dorsam and Gutkind, 2007; Hanahan and Weinberg, 2011; O’Hayre et al., 2014).