(A) MMP-2 and MMP-9 induction by fibronectin. CEM T cells were cultured on several extracellular matrix proteins for 24 hours. The figure shows the zymographic pattern of concentrated conditioned medium of 10⁷ cells plated on polylysine (lane 1), fibronectin (lane 2), laminin-1 (lane 3), type-I collagen (lane 4), and type-IV collagen (lane 5). (B) Accumulation of MMP-2 and MMP-9 in the conditioned medium over time. 10⁷ cells were incubated on plastic or on fibronectin for different periods of time. The conditioned medium was concentrated and subjected to gelatin zymography. The figure shows the gelatinolytic signal quantified as described in the Materials and Methods section. (C) CEM cells produce activated forms of MMP-2 in response to fibronectin. Unconcentrated conditioned medium obtained from HUVEC confluent monolayers cultured on plastic was subjected to gelatin zymography in the absence (−) or in the presence (+) of p-aminophenylmercuric acetate (APMA). Concentrated conditioned medium from 10⁷ CEM cells cultured on fibronectin (Fn) for 24 hours disclosed an identical zymographic pattern.