KIF3B and prostate cancer: For instance, in ovarian cancer, it inhibits proliferation by targeting MAPK4.[16] while in prostate cancer, its transcriptional downregulation promotes bone metastasis.[17] Similarly, in oral squamous cell carcinoma, it targets KIF3B to inhibit development.[18] The discrepancy between our genetic evidence and these functional studies highlights the critical difference between tissue-specific miRNA activity and systemic, genetically determined miRNA levels measured in plasma.