Fig. 4

MMP-8 expression by myoepithelial cells has a paracrine effect on tumour cell invasion. a β6-1089 cells transfected with empty vector (EMPTY) wild-type matrix metalloproteinase-8 (MMP-8 WT) or inactive mutant MMP-8 (EA) were plated into 24-well plates and grown in serum-free media for 24 hours. Transwells coated with Matrigel were placed into the wells and MDA-MB-231 or SUM159 cells were placed on top of the Matrigel. After 24 hours the transwells were removed and the number of invading cancer cells counted. Invasion was calculated relative to the β6-1089 transfected with empty vector. MDA-MB-231 and SUM159 cells exhibited a significant reduction in invasion when in the presence of β6-1089 transfected with WT cells, this was not observed with the β6-1089 transfected with EA cells. b MTS assay for viability on MDA-MB-231 and SUM159 cells grown for 24 hours in the presence of conditioned media (CM) from β6-1089 cells transfected with empty vector (EMPTY) wild-type MMP-8 (WT) or inactive mutant MMP-8 (EA). No difference was observed between any of the groups relative to β6-1089 transfected with empty vector. c Transwells were set up as described above with N-1089 cells transfected with siRNA targeting MMP-8 (siMMP-8) or Luciferase (siLuc) were plated into the bottom wells. MCF-7, MDA-MB-231 and SUM159 cells were plated into Matrigel-coated transwells above. After 24 hours (or 48 hours for MCF-7) the transwells were removed and the number of invading cancer cells counted. Invasion was calculated relative to the N-1089 transfected with siLUC. MDA-MB-231 and SUM159 cells exhibited a significant increase in invasion when in the presence of N-1089 transfected with siMMP-8. d MTS assay for viability on MCF-7, MDA-MB-231 and SUM159 cells grown for 24 hours in the presence of conditioned media (CM) from N-1089 cells transfected with siRNA targeting MMP-8 (siMMP-8) or Luciferase (siLuc). No difference was observed between the two groups. ^** p = 0.01, (Student’s t test). Error bars = SEM, n = 3 independent experiments