Antisense epidermal growth factor receptor transfection impairs the proliferative ability of human rhabdomyosarcoma cells

Human rhabdomyosarcoma cells express membrane epidermal growth factor receptor (EGF-R), which could confer responsiveness to EGF and transforming growth factor-α (TGF-α) of autocrine or paracrine origin. To study the role played by this growth factor circuit in the proliferation and differentiation of myogenic neoplastic cells, human rhabdomyosarcoma EGF-R-expressing cells (RD/18 clone) have been transfected with a plasmid containing a fragment of the EGF-R cDNA in the antisense orientation. In vitro growth and differentiative ability were studied on six antisense-transfected clones (AS) in comparison to parental RD/18 cells and to cells transfected with the plasmid containing only the neomycin resistance gene (NEO). A reduced EGF-R membrane expression was found in AS clones by decreased immunofluorescence with an anti-EGF-R monoclonal antibody. All AS transfectants had a greatly impaired proliferative ability, even when cultured in fetal bovine serum- containing medium. Proliferation of AS clones was completely blocked in medium supplemented with 2% horse serum. The differentiation ability of AS clones was heterogeneous, ranging from clones with a percentage of myosin- positive cells higher than controls to clones with a negligible myosin expression. Therefore, the growth impairment determined by the loop interruption is not sufficient to switch on the differentiation program. The role played by EGF-R in the proliferation of human rhabdomyosarcoma cells suggests that this receptor could constitute a target for a therapeutic approach.