BTG2 and invasive ductal breast carcinoma: Constitutive expression of BTG2/TIS21 in the ductal carcinoma in situ (DCIS), but not in the infiltrating ductal carcinoma, strongly suggests that BTG2 might be an important barrier to block cancer progression from DCIS to infiltrating cancers31, and the notion is well supported by the report that p53 deficiency-enhanced metastatic potential of breast cancer is linked to BTG2/TIS21 loss in the primary and metastatic sites of TNBC-PDX model32.