OCA2 and breast carcinoma: However, recent data using MMTV-P-Rex1 transgenic mice have shown that P-Rex1 is not necessary for mitogenesis or survival in breast cancer, thus indicting that it may be active in late stage metastases, as has been shown by microarray analysis of breast cancer cells where P-Rex1 expression was associated with matrix metalloproteinase (MMP-10) expression, and thus, a more invasive phenotype (Barrio-Real et al., 2016).