Repurposing FDA-approved drugs to find a novel inhibitor of alpha-ketoglutarate-dependent dioxygenase FTO to treat esophageal cancer.

Background and purpose: The Fat mass and obesity-associated protein (FTO) plays a significant role in esophageal cancer by regulating N6-methyladenosine (m6A) modification. FTO inhibition has shown potential in cancer therapies but remains underexplored. This study aimed to identify a safer, FDA-approved compound for FTO inhibition that can be used in combination with chemotherapy drugs.

Experimental approach: FDA-approved drugs were screened from the Zinc 15 database using AutoDock Vina against the 3D structure of FTO (PDB ID: 3LFM). Discovery Studio software was used to determine binding interactions. The GROMACS package was used for molecular dynamics simulations. A non-toxic concentration was determined through an MTT assay on KYSE-30 esophageal cancer cells. The ELISA assay was used to measure the m6A levels in RNA.

Findings/results: Four compounds, ergotamine, midazolam, digoxin, and loratadine, were identified. Loratadine (ΔG: -8.9) formed stable interactions with FTO, specifically with residues Ser229, Tyr109, Leu109, Val229, and His231. Molecular dynamic simulations of the FTO-loratadine complex revealed higher RMSD fluctuations (0.4-0.6 nm), but the system remained stable overall. RMSF analysis showed similar fluctuation patterns in all three systems, indicating that loratadine did not affect protein structure stability. MM/PBSA calculations revealed powerful binding energy for the FTO-loratadine complex (-135.73 kJ/mol), driven by favorable van der Waals interactions. KYSE-30 cells treated with loratadine (100 μM), m6A levels in KYSE- 30 cells compared to the control group were significantly elevated at a non-toxic concentration.

Conclusion and implications: Loratadine is a promising, low-toxic FTO inhibitor that could complement chemotherapy for esophageal cancer.