Silylation of hydroxychloroquine enhances autophagy inhibition and antiproliferative activity in breast and pancreatic cancer cells
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Introduction
Autophagy is a key survival mechanism in cancer, and chloroquine (CQ) and hydroxychloroquine (HCQ) are widely used late-stage autophagy inhibitors. However, their low potency and the need for high doses limit antitumor efficacy and raise concerns about off-target toxicity. We therefore designed hydroxychloroquine silyl derivatives based on the hypothesis that increasing lipophilicity at the terminal 2-hydroxyethyl moiety enhances lysosomal accumulation and autophagy inhibition while preserving the 4-aminoquinoline pharmacophore.
Methods
Three HCQ silyl ethers-OTBS ( 2 ), OTIPS ( 3 ), and ODPS ( 4 ) have been synthesized by silylating the terminal hydroxyl of HCQ. Antiproliferative activity and autophagic flux along with apoptosis have been assessed for LC3B-II, p62/SQSTM1, and caspase-3-mediated PARP-1 cleavage.
Results and Discussion
The HCQ silyl derivatives retain the core pharmacophore and display improved or comparable antiproliferative activity relative to HCQ, achieving low-micromolar IC 50 values. Candidate compounds 2 and 3 strongly induce LC3B-II and p62 accumulation than HCQ, consistent with enhanced blockade of autophagic flux. This autophagy disruption is accompanied by increased PARP-1 cleavage, particularly in aggressive 4T1 and MIAPaCa-2 cells, linking reinforced lysosomal/autophagy inhibition to apoptotic signaling.
Conclusion
These findings show that silylation of HCQ enhances autophagy inhibition and pro-apoptotic activity while maintaining pharmacology, identifying HCQ silyl derivatives as promising leads for autophagy-targeting antitumor agents.
