OCA2 and breast carcinoma: In breast cancer, P-Rex1 is an intermediate in receptor tyrosine kinase (ErbB and IGF-1R) and G protein-coupled receptor (GPCR) signal transduction, is activated by PI3K, and feeds back to regulate the PI3K pathway via the Rac/PAK/RAF/MEK/ERK axis [5, 6, 11, 12].