CD63 and breast cancer: These CAFs promote resistance by releasing exosomes containing miR-20, which targets and downregulates Retinoblastoma 1 (RB1) in cancer cells, thereby reducing the sensitivity to Cyclin-Dependent Kinases 4 and 6 (CDK4/6) inhibitors, using cyclic Arg-Gly-Asp peptide (cRGD)-miR-20 sponge nanoparticles to neutralize the miR-20 restored drug sensitivity in vitro and in vivo, suggesting that targeting CD63+ CAFs and their exosomal miR-20 could improve CDK4/6i efficacy in breast cancer [162].