Colon cancer cells evade drug action by enhancing drug metabolism

Colorectal cancer (CRC) is the second leading cause of cancer deaths worldwide. One key reason is the lack of durable therapies that target KRAS-dependent disease, which represents approximately 40% of CRC cases. Here, we use liquid chromatography/mass spectrometry (LC/MS) analyses on Drosophila CRC tumour models to identify multiple metabolites in the glucuronidation pathway-a toxin clearance pathway that impacts most drugs-as upregulated in trametinib-resistant RAS/APC/P53 ("RAP") tumours compared to trametinib-sensitive Ras^G12V single mutant tumours. Genetic inhibition of different steps along the glucuronidation pathway strongly reversed RAP resistance to trametinib; conversely, elevating glucuronidation pathway activity was sufficient to direct trametinib resistance in Ras^G12V animals. Mechanistically, pairing oncogenic RAS with hyperactive WNT activity strongly elevated PI3K/AKT/GLUT signalling, which in turn directed elevated glucose uptake and glucuronidation; our data also implicate the pentose phosphate pathway in this process. We provide evidence that this mechanism of trametinib resistance is conserved in a KRAS/APC/TP53 mouse CRC tumour organoid model. Finally, we identify two clinically accessible approaches to inhibiting drug glucuronidation: (i) blocking an initial HDAC1-mediated deacetylation step of trametinib with the FDA-approved drug vorinostat; (ii) reducing blood glucose by the alpha-glucosidase inhibitor acarbose. Overall, our observations demonstrate a key mechanism by which oncogenic RAS/WNT activity promotes increased drug clearance in CRC and provides a practical path towards abrogating drug resistance in CRC tumours.