GLI1-inducible glucuronidation targets a broad spectrum of drugs.

Cancer therapies are plagued by resistance. Previously, we discovered a novel form of cancer drug resistance where the Glioma-associated protein 1 (GLI1) elevates UGT1A glucuronidation enzymes thereby glucuronidating cytarabine and ribavirin leading to resistance in leukemia patients. Here, we demonstrate that GLI1 imparts resistance to ~40 compounds, including FDA-approved drugs with disparate chemotypes (e.g. methotrexate and venetoclax). GLI1 indirectly elevates UGT1As via the chaperone calreticulin which is required for resistance. Further, we demonstrate that resistant cells are more sensitive to ATP inhibitors suggesting an Achilles' heel which could be exploited in future. In all, we identify GLI1-inducible glucuronidation as a broad-spectrum multi-drug resistance pathway.