In this review, we have detailed how cancer cells rewire BCAA metabolism at every step—from transporter upregulation and BCAT-mediated transamination to dysregulated BCKDH activity—to support anabolic growth, redox homeostasis, and oncogenic signaling, highlighting both tumor-specific adaptations and shared mechanistic themes, and surveying emerging strategies for intervention. This evidence concerns the gene PPM1K and cancer.