Fig. 2. Activation of MEK/ERK signaling by oncogenic RasV12 induces MMP-9 in an 3ß1-dependent manner. Wild-type MK^+/+ cells (MK+/+) or 3ß1-deficient MK^–/– cells (MK–/–) grown on LN-5 ECM were infected with adenovirus expressing either HA-tagged RasV12 (RasV12) or ß-galactosidase (control); MOI=70. Cells were then grown in serum-free medium for an additional 36 hours in the presence or absence of 10 µM U0126, as indicated. Levels of secreted MMP-9 in the culture medium were assayed by gelatin zymography (top panels); murine MMP-9 and human MMP-9 standard are indicated. To confirm RasV12 expression, equal protein from corresponding cell lysates was immunoblotted with anti-HA tag (RasV12 panel). Parallel blots with anti-phospho-ERK confirmed ERK activation in RasV12-infected cells and inhibition of ERK activation by treatment with U0126 (pERK panel).