POSTN and osteoarthritis, knee: We have reported on the importance of POSTN exon 17 in breast cancer [23], heart failure [24,25,26], cerebral infarction [27,28], diabetic retinopathy [15], and knee osteoarthritis [14] in animal models; however, the function of POSTN exon 17 in pathological organs such as the primary and metastatic regions of breast cancer is still unclear.