Reduced expression of QSOX1 in MCF7 and BT549 cells leads to a decrease in functional MMP-9 activity. Gelatin zymography of a) MCF7 and b) BT549 conditioned media shows a decrease in MMP-9 homodimers (130 kDa) and MMP-9 (92 kDa). The percent decrease in MMP-9 expression in MCF7 was: sh742: 70% (P = 0.0171); sh528: 77% (P = 0.0182), and in BT549 was: sh742: 34% (P = 0.0531); sh528: 88% (P = 0.0564) compared to shScramble control. c) Western blots of total cell lysate from shRNA treated MCF7 and BT549 probing for MMP-2 and -9 show insignificant changes compared to shScramble control. Full images can be seen in Additional file 1. d) QPCR of QSOX1 transcripts and MMP-2 and -9 transcripts. The graph represents relative gene expression calculated as ΔΔCq using GAPDH as the endogenous reference gene. MMP-2 - MCF7 sh742 (P = 0.5294), sh528 (P = 0.2112); BT549 sh742 (P = 0.0054), sh528 (P = 0.0019). MMP-9 - MCF7 sh742 (P = 0.3981), sh528 (P = 0.3385); BT549 sh742 (P = 0.4192), sh528 (P = 0.0701). Average ± SD; significance was determined using a Student's two-tailed t-test.