Fig. 6

IL1B promotes the invasion of breast cancer cells in an OPG-dependent manner. MDA-MB-436 breast cancer cells transfected with OPG (siOPG1) or negative control (siNeg) siRNA were pretreated with IL1B (10 ng/mL), and subsequently assayed for invasiveness. a IL1B-mediated cell invasion is reduced in OPG knockdown cells, (n = 3). Data is represented as relative fluorescence units (RFU) fold change relative to the untreated negative control. b OPG knockdown in the breast cancer cells used in the cell invasion assay was assessed at the end point of the experiment. Knockdown was verified by qRT-PCR. MDA-MB-436 cells transfected with OPG or control siRNA were treated with IL1B or PBS (10 ng/mL) for 72 h. c OPG knockdown at 72 h was verified by qRT-PCR. Assessment of d MMP3 and e IL1B mRNA levels indicate the IL1B-mediated induction is inhibited by OPG depletion, (n = 3). Data are represented by mean ± SD. Asterisks indicate statistical significance (p < 0.05). f Signaling model. IL1B secreted from macrophages and/or from breast cancer cells themselves, activate p38 and p42/44 MAPK signaling in the breast cancer cells resulting in increased OPG secretion. In turn, this OPG secretion up-regulation promotes the invasiveness of breast cancer cells. OPG levels in breast tumors