Figure 1.

STC1 expression and cell invasion. STC1 expression is increased via a PI-3K/Akt/NF-κB-dependent signaling pathway. STC-1 protein is subsequently secreted into the extracellular matrix in an autocrine/paracrine manner. Secreted STC1 binds to its receptors on the surface of the cell membrane to form a complex which initiates the JNK/c-Jun signaling pathway. Activated c-Jun dimerizes with the Fos family of proteins to form AP-1, which activates MMP-9 transcriptional activity. Finally, increased MMP-9 expression results in increased cell invasion of triple-negative breast cancer cells as a result of extracellular matrix degradation. STC1, stanniocalcin-1; PI-3K, phosphoinositide 3-kinase; Akt, protein kinase B; NF-κB, nuclear factor-κB.