The metastatic lymph node 64 (MLN64) gene was initially identified its highly expressed in the metastatic lymph node from breast cancer It is localized in q12-q21 of the human chromosome 17 and is often co-amplified with erbB-2. However. the role played by MLN64 in breast cancer remains unclear In the present study, the expression of MLN64 was examined in a breast cancer cohort using quantitative real-time PCR and immunohistochemical staining It demonstrated that MLN64 was highly expressed in breast tumours compared to corresponding background tissues at both transcript level and protein level The elevated level of MLN64 transcripts was correlated with the poor prognosis and overall survival of the patients A panel of breast cancer Cell sublines was subsequently developed by knockdown of MLN64 expression Loss of MLN64 expression in MCF-7 cells resulted in a significant reduction of cell growth (absorbance for MCF-7 Delta(MLN64) being 0.87 +/- 0.07, P<0.01 vs. wild-type control (MCF-7(WT) 1 13 +/- 0 06) and transfection control (MCF-7(pEF) 1 27 +/- 0 05) In cell-matrix adhesion assay. MBA-MB-231(Delta MLN64) cells showed a significant increase III adhesion (86 +/- 14), p<0.01 compared with both MDA-MB-23I(WT) (61 +/- 20) and MDA-MB-231p(EF) (45+/-27). Further investioations demonstrated increase in protein level of the focal adhesion kinase (FAK) in MDA-MB-231 Delta(MLN64) Cells using Western blot analysis and immunofluorescent stainign of FAK Moreover, addition of FAK inhibitor to these cells diminished the effect of MLN64 oil cell-matrix adhesion. stio-estinc, that FAK contributed to the increased adhesion in MDA-MN-231 Delta(MLN64) cells III conclusion. MLN64 is overexpressed in breast cancer. and its level correlates with poor prognosis and patient survival MLN64 contributes to the development and progression of breast cancer through the regulation Of Cell proliferation and adhesive capacity.