ATP2B4 and ductal breast carcinoma in situ: Mammospheres generated by sh-PMCA4 or PMCA4bLA-expressing MCF-7 cells did not form central lumens; rather, they displayed several small F-actin-rich areas (Fig. 8a–c and Supplementary Fig. 6b, d) resembling the microlumens commonly seen in ductal carcinoma in situ (DCIS)54.