anti-cancer therapeutics. The ocular cancer, retinoblastoma cells were treated with fatty acid synthase (FASN) enzyme inhibitors: cerulenin, triclosan and orlistat. The IC 50 and dose-dependent sensitivity of cancer cells to FASN inhibitors decrease in biologic enzyme activity, and cell morphology alterations were analysed. Molecular interactions of enzyme-inhibitor complexes were studied by molecular modelling and docking simulations. The crystal structures of ketoacyl synthase (PDB ID:3HHD) (cerulenin) and thioesterase (PDB ID:2PX6) (orlistat) domains of human FASN were utilized for docking, while for the non-crystallised human FASN enoyl reductase domain (triclosan), homology model was built and used for docking. All three inhibitors showed significant binding energy indicating stable complex formation with their respective FASN subunits. The predicted Ki value of the FASN inhibitors corroborated well with their corresponding anti-cancer effects.

Fatty acid synthase (FASN), a multi-enzyme complex, is involved in lipid biosynthesis. FASN is over-expressed in different types of cancers and is being widely investigated for its role in cancer progression, diagnosis and therapy. Here, three inhibitors targeting different domains of FASN -cerulenin, triclosan and orlistat -were evaluated for their anti-proliferative efficacy in ocular cancer, retinoblastoma (RB) cells and their toxicity (if any) in normal cells. FASN inhibitors were tested in cultured retinoblastoma Y79 cells, normal fibroblast (3T3) and Müller glial (MIOM1) cells. Cell viability was determined by MTT-based assay, and IC 50 (50% inhibitory concentration) of the FASN inhibitors was calculated in neoplastic and non-neoplastic cells. The IC 50 after 48 and 96 hr of incubation with the three anti-FASN agents showed that cerulenin, triclosan and orlistat inhibited retinoblastoma cell proliferation in a dose-and time-dependent manner. The cancer cells exhibited differential dose-and time-dependent response ⁄ sensitivities to cerulenin, triclosan and orlistat. The 48-hr neoplastic IC 50 dosages were, however, not toxic to the normal cells. These findings were confirmed by phase-contrast microscopic assessment of cell morphology. Therapeutic index (TI) was calculated as a ratio of the IC 50 normal cells, to the IC 50 neoplastic cells. Relative to normal MIOM1 cells, TI was 9.18 for cerulenin, while 5.32 for triclosan and 1.72 for orlistat. The TI computed relative to 3T3 cells was 28.64, 7.10 and 2.58 for cerulenin, triclosan and orlistat, respectively. DNA fragmentation analysis suggests that FASN inhibitors induced apoptotic DNA damage in retinoblastoma cells. Thus, FASN inhibition can be an effective strategy in retinoblastoma therapy.

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