en Medical Genetics Medical Genetics Original Research Original Research The insulin-like growth factor I receptor (IGF-IR) plays an essential role in the establishment and maintenance of transformed phenotype. Interference with the IGF-IR pathway by antisense causes reversal of the transformed phenotype in many rodent and human tumor cell lines. We stably transfected the PC-3 human prostate cancer cell line with an IGF-IR antisense RNA expression plasmid. The number of IGF-I receptors on the antisense-transfected PC-3 cells was reduced by 40.2% relative to the control-transfected cells. The transfected cells maintained their high expression of IGF-IR antisense RNA for up to one year in selective medium . The reduction in the expression of IGF-IR had no effect on the cell growth in monolayer. The clonogenicity of antisense-transfected cells was 24.7% of the clonogenicity of control-transfected cells in soft agar. There was a good correlation between IGF-IR level and inhibition of transformation in soft agar. These results indicate that reduction of IGF-IR by antisense RNA can reverse the transformed phenotype of human prostate cancer cells. Type I insulin-like growth factor receptor; Antisense; Transfonnation; prostate cancer; PC- 3. 59 66 http://mjiri.iums.ac.ir/browse.php?a_code=A-10-298-182&slc_lang=en&sid=1 R JALAL 20031947532846003908 20031947532846003908 No A DIZAGI 20031947532846003909 20031947532846003909 No K NAYERNIA 20031947532846003910 20031947532846003910 No B GOLIAEI goliaei@ibb.ut.ac.ir 20031947532846003911 20031947532846003911 Yes