Summary: To observe the inhibitory effects of an antisense u-PAR vector on invasion of highly inva-sive PC-3M cell subclones, the effects of the antisense u-PAR on activity of MMP-9 in those highlyinvasive cell subclones were detected by a quantitative RT-PCR and zymography. The monolayer in-vasion assay and colony formation assay in soft agar were used. And tumorigenesis rate and invasionsby the cell subclones with or without the antisense u-PAR were observed in nude mice. It was foundthat in vitro growth of highly invasive PC-3M cell subclones transfected with the antisense u-PARwas declined, and the ability of anchorage-independent growth of those cell subclones was found de-creased sharply, with the inhibiting rate becoming 79 % and 60 %, respectively. Although the anti-sense u-PAR didnt change MMP-9 gene transcription, they could inhibit the activation of MMP-9 ofhighly invasive PC-3M cell subclones. Moreover, the tumorigenesis rate of the cell subclones with theantisense u-PAR decreased and the growth of a neoplasm also slowed down. Thet tests showed thedifference between experimental and control groups was statistically significant (P＜0. 01). The anti-sense u-PAR vector could not only inhibit the invasion ability of highly invasive PC-3M cell subclonesin vitro but also restrain the growth of those cell subclones in vivo.