Effect of Stearoyl-CoA Desaturase Gene knock down on Lipid Synthesis and Cell Proliferation in SV40-Transformed Human Lung Fibroblasts

N. SCAGLIA; R. A. IGAL

Congreso; ICGEB Meeting: Gene Expression and RNA Processing; 2003

The saturated (SFA) and monounsaturated fatty acids (MUFA) are the main components of mammalian cell lipids. Its content is determinated by the Stearoyl-CoA Desaturase (SCD) activity, the enzyme that converts SFA into MUFA. A broad variety of human cancers express a high cellular content of MUFAs together with increased levels of SCD mRNA. In order to study the relationship between SCD expression and the neoplasic phenotype, we attempted to suppress SCD activity. To do so have stably transfected SV40-transformed human lung fibroblasts (SV 40-WI 38) with a segment of the human SCD cDNA in antisense orientation in pcDNA3 plasmid (hSCDas line). As control, the same cell line was transfected with the mock plasmid (Control line). SCD activity, using [1-14C] stearic acid as substrate, was significantly lower in all hSCDas clones analyzed (ranging from 56% to 30% of the control activity). Incorporation of [1-14C] stearic acid or its derivatives into different lipid species showed an increase in triacylglicerids radioactivity in all hSCDas clones with respect to control cell line. Although cells were incubated in presence of fetal bovine serum in all experiments, analysis of total fatty acid content showed a reduction of MUFA/SFA ratio and a consequent elevation of polyunsaturated fatty acid percentage. DNA synthesis, evaluated as [3H] Timidine incorporation/ g protein, decreased in all three hSCDas clones (exhibiting a high correlation coefficient with the diminish in SCD activity). Fluorescence microscopy analysis revealed an increased number of apoptotic nucleus in the SCD knock down cells. Taken together these results suggest that SCD knock down affects several important cellular functions such as proliferation (related to SCD participation in membrane biogenesis) and apoptosis (that could be induced by highly toxic SFA such as palmitic acid).