SPP1 and breast carcinoma: A study designed to characterise the critical sequence of an RNA aptamer, OPN-R3, directed against human OPN in MDA-MB231 human breast cancer cells116 found that exposure to OPN-R3 was associated with significant downregulation of OPN signal transduction pathways, PI3K, JNK1/2, Src and Akt, as well as extracellular matrix degradation pathways involving matrix metalloproteinases.