CD44 and cancer: CSC-specific signaling proteins (β-catenin), specific surface receptors (CD133 and CD44), stem cell factors (OCT4), functional enzymes (ALDH), and transcription factors (TFs), which are activators of cell pathways all exported in exosomes, can mediate tumor stroma modulations by cancer cells and vice versa (Pavlides et al., 2009; Boelens et al., 2014; Richards et al., 2017; Jurj et al., 2020).