HNF4A and cancer: A recent study demonstrated functional relevance of exosome-associated SFRP family proteins and that human lung cancer cells take up SFRP-containing exosomes, whereby SFRPs co-localize with β-catenin in both the cytoplasm and nucleus to mediate β-catenin/TCF-mediated transcription of Wnt target genes known to effect cancer stem cell properties [45].