PTK7 and breast cancer: To examine the effect of PTK7 downregulation on the oncogenic properties of BC cells, PTK7 was silenced in T-47D and MCF-7 HR-positive BC cells and HCC1187, MDA-MB-231, MDA-MB-436, and MDA-MB-453 TNBC cells by infection with a lentivirus encoding PTK7 shRNA (Figure 2A).