Activation of
fatty acid synthase (FASN)
enzyme in the de novo lipogenic pathway has been reported in various
cancers including
retinoblastoma (RB), a pediatric ocular
cancer. The present study investigates lipogenesis-dependent survival of RB
cancer cells and the associated molecular pathways in FASN silenced RB cells. The
siRNA-mediated FASN gene knockdown in RB
cancer cells (Y79, WERI RB1) repressed FASN
mRNA and
protein expressions, and decreased
cancer cell viability. Global gene expression microarray analysis was performed in optimized FASN
siRNA transfected and untransfected RB cells. Deregulation of various downstream cell signaling pathways such as EGFR (n = 55 genes),
TGF-beta (n = 45 genes), cell cycle (n = 41 genes), MAPK (n = 39 genes), lipid metabolism (n = 23 genes), apoptosis (n = 21 genes), GPCR signaling (n = 21 genes), and oxidative phosporylation (n = 18 genes) were observed. The qRT-PCR validation in FASN knockdown RB cells revealed up-regulation of ANXA1,
DAPK2, and down-regulation of SKP2, SREBP1c, RXRA, ACACB, FASN, HMGCR, USP2a genes that favored the anti-
cancer effect of lipogenic inhibition in RB. The expression of these genes in primary RB
tumor tissues were correlated with FASN expression, based on their clinico-pathological features. The differential phosphorylation status of the various PI3K/AKT pathway
proteins (by western analysis) indicated that the FASN gene silencing indeed mediated apoptosis in RB cells through the PI3K/AKT pathway. Scratch assay clearly revealed that FASN silencing reduced the invading property of RB
cancer cells. Dependence of RB
cancer cells on lipid metabolism for survival and progression is implicated. Thus targeting FASN is a promising strategy in RB
therapy.