PIK3R1 and breast cancer: However, the clinical behavior of luminal-type breast cancer can be markedly heterogeneous despite similar levels of ER expression [57]; therefore, a set of genes differentially regulated in MCF-7-14 cells (PIK3R1, SOCS2, BMP7, CD44 and CD24) may be useful markers to identify among good prognosis tumors those that will relapse and metastasize.