QSOX1 promotes tumor cell invasion. a.) MCF7, b.) BT549 and c.) BT474 cells transduced with shSramble, sh742 and sh528 shRNAs were seeded at equal densities in the top chamber of Matrigel™ invasion wells and allowed to incubate for 48 (BT549 and BT474) and 72 (MCF7) hours, after which cells that had digested MatrigelTM and migrated through the 8 um pores were counted on the underside of the insert. Representative 20× images are presented. MCF7 cells transduced with sh742 and sh528 show a 65% and 71% decrease in invasion. BT549 cells transduced with sh742 and sh528 showed a 60% and 40% decrease in invasion. BT474 cells transduced with sh742 and sh528 show an 82% decrease in invasion. Each knockdown was compared to shScramble controls. The invasive phenotype of shQSOX-transduced MCF7 (d.), BT549 (e.) and BT474 (f.) cells was rescued by exogenous incubation with catalytically active rhQSOX1. rhQSOX1 (AA) mutant is a mutant without enzymatic activity, generously provided by Dr. Debbie Fass. Graphs represent average ± SD (MCF7, BT549 and BT474 n = 3), significance *, P < 0.05, ** P < 0.005.