Nitroxoline-O-protected derivatives inhibit MetAP2 and activate ATF4 through mTORC1 to inhibit cancer cell growth

Abstract

Reprogrammed cancer cell proliferation requires high levels of protein synthesis and concomitant folding and processing. N-terminal methionine amino peptidases (MetAP) are a class of enzymes that cleave the initiator methionine amino acids to allow for peptide maturation and co-translational processing. Specifically, based on its role in protein synthesis, MetAP2 has been found to be upregulated in cancer cells and has been explored as a potential anticancer target. Cellular perturbations that impinge on protein synthesis activate cellular stress pathways, including the integrated stress response and mTORC1. Nitroxoline, a MetAP2 inhibitor has been explored as an anticancer agent but is hampered by poor pharmacokinetic properties. Here, we synthesize a few O-substituted silyl and nonsilyl nitroxoline analogs to diversify the nitroxoline template to reduce metabolic vulnerability. In vitro MetAP2 and cancer cell proliferation inhibition assays demonstrate that synthesized analogs retain potency when compared to the parent nitroxoline. Mechanistically, we show that the lead candidate compound 3 and nitroxoline activate ATF4 mediated stress responses through non-canonical mTORC1. These results further implicate MetAP2 protein processing in mTORC1 nutrient sensing pathways and provide novel synthetic analogs of nitroxoline for potential cancer treatment.