PC3-ML cells contain high levels of exosomal miR-888, which downregulates proteins such as Krüppel-like factor 5 (KLF5), retinoblastoma-like protein 1 (RBL1), tissue Inhibitor of metalloproteinases 2 (TIMP2), and SMAD family member 4 (SMAD4), strengthening tumour cell abilities [54]. Here, SMAD4 is linked to neoplasm.