Amplification of the long arm of chromosome 8 is one of the most recurrent findings in prostate cancer and it is associated with poor prognosis. Several minimal regions of amplification suggest multiple target genes which are yet to be identified. We have previously shown that TCEB1, EIF3S3, KIAA0196 and RAD21 are amplified and overexpressed in prostate cancer and they are located in the 8q area. In this study, we examined the functional effects of these genes to prostate cancer cell phenotype. We overexpressed and inhibited the genes by lentivirus mediated overexpression and RNA interference, respectively. shRNA mediated TCEB1 silencing decreased significantly cellular invasion of PC-3 and DU145 cells through Matrigel. TCEB1 silencing reduced the anchorage-independent growth of PC-3 cells. Similar effects were not seen with any other genes. When overexpressed in NIH 3T3 cells, TCEB1 and EIF3S3 increased the growth rate of the cells. Transcriptional profiling of TCEB1 silenced PC-3 cells revealed decrease of genes involved in invasion and metastasis. Finally, we also confirmed here the overexpression of TCEB1 in hormone-refractory prostate tumors. This study indicates that TCEB1 promotes invasion of prostate cancer cells, is involved in development of hormone-refractory prostate cancer and is thereby a strong candidate to be one of the target genes for the 8q gain.