Therapeutic and toxicologic evaluation of anti-lipogenic agents in cancer cells compared with non-neoplastic cells.

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.