NKX2‐1‐expressing cancer cells were highly sensitive to sertraline‐mediated serine/glycine inhibition and etoposide chemotherapyAt end‐stage disease, sertraline reduced progression, evidenced by smaller spleens and lower bone marrow infiltration vs. controlsA serine/glycine‐free diet + sertraline further enhanced disease suppression. Here, NKX2-1 is linked to cancer.