Objective To explore the effects of different n-6/n-3 polyunsaturated fatty acid (PUFA) ratio on the expression of insulin-like growth factor receptor-1 (IGF-1R) in breast cancer cells.   Methods MCF-7 and MDA-MB-231 cells were treated with n-6 PUFA

or n-3 PUFA

or the mixture of n-6/n-3 PUFA at ratio of 1:1

5:1

10:1. The cell proliferation capacity was detected by MTT

and the expressions of IGF-1R mRNA and protein were assayed by RT-PCR and Western blot

respectively.  Results n-6 PUFA and 10:1 n-6/n-3 PUFA obviously promoted cell proliferation and up-regulated the expression of IGF-1R mRNA and protein. n-3 PUFA and 1:1 n-6/n-3 PUFA greatly repressed cell proliferation and down-regulated IGF-1R mRNA and protein expression. However

5:1 n-6/n-3 PUFA had no obvious influence both on the cell growth and IGF-1R expression.   Conclusion n-6/n-3 PUFA of different ratio has diverse effects on IGF-1R gene expression in breast cancer cells. n-3 PUFA and 1:1 n-6/n-3 PUFA significantly inhibit the proliferation and IGF1R gene expression.