However, only two related breast cancer cell lines, T47D and MCF7, were able to efficiently process proMPO into the mature heterotetramer and for T47D cells those levels nearly approach the efficiency of processing (ratio of heterotetramer/proMPO on immunoblot) that occur for endogenous MPO in HL60 cells (Fig 2A, left panel). This evidence concerns the gene MPO and breast carcinoma.