BMP6 and breast cancer: In four main subtypes of breast cancer, elevated expression of BMPR1B and ACVR2B were seen in Luminal A subtype, while BMP4, GDF15 and ACVR1B were higher in Luminal B, TGFBR1 and BMP8A were higher in HER2 positive, BMP2, BMP6 and GDF5 were higher in TNBC.