TACSTD2 and breast cancer: We selected two additional luminal breast cancer cell lines, HCC1500 and MDA-MB-453, that express both EpCAM and Trop2 (Appendix Fig. S1), but differ in their morphologies and have behaviours departing in opposite directions from MCF7 cells: When grown on collagen, HCC1500 cells spread very poorly on matrix (Figs. 7A,C and EV5), but establish extensive cell-cell contacts and form coherent aggregates (Figs. 7B and EV5).