QSOX1 and breast carcinoma: Overexpression of QSOX1 in breast cancers has not previously been reported, however in a recent proteomics study, quiescin Q6-derived peptides were found to be secreted at elevated levels by two breast cancer derived cell lines, BT474 and MDA-MB-468, compared to the normal breast epithelial cell line, MCF-10A [21].