SPP1 and breast cancer: On the other hand, a meta-analysis of 8 studies published up to February 2014 with clinical cohorts ranging from 100 to 333 breast cancer patients [104] showed no correlation between OPN expression and several other diagnostic/prognostic biomarkers commonly used for breast cancer, such as HER2, PR, and ER, although a significant association between OPN overexpression and both lymph node metastasis and overall survival was reported.