Gelatinase A, also denoted matrix metalloproteinase 2, plays multiple critical roles in the neoplastic process, including facilitation of neoangiogenesis and formation of distal metastases. The transcriptional regulation of the gelatinase A gene is under the control of strong, evolutionarily conserved cis-acting enhancer elements, designated the r2 (human) or RE-1 (rat), that harbor contiguous binding motifs for the transcription factors activating protein-2 (AP2), p53, and YB-1. Using recombinant transcription factors, complex patterns of RE-1 binding were observed by electrophoretic mobility shift assay. Increased complex formation was detected with the AP2/YB-1 and AP2/p53 combinations, while YB-1 competed with p53 for binding. The combination of AP2, p53, and YB-1 yielded novel ternary complexes, particularly when binding to single-stranded RE-1 probes. Transient transfection of hepatocellular carcinoma cell lines with a series of gelatinase A luciferase reporter constructs were in accordance with the binding patterns determined by electrophoretic mobility shift assay. Combined AP2 and p53 increased gelatinase A luciferase reporter activity significantly, and the inclusion of YB-1 yielded further increase in both reporter activity and secreted levels of gelatinase A protein. YB-1 and p53 expression are increased following multiple genotoxic stresses, including irradiation, and the synergistic interactions of these induced transcription factors with the widely expressed AP2 protein provide a probable pathophysiologic mechanism for the enhanced tumor cell synthesis of gelatinase A induced by radiation.

Discoidin domain receptor 2 (DDR2) is an unusual receptor tyrosine kinase in that its ligand is fibrillar collagen rather than a growth factor-like peptide. We examined signal transduction pathways of DDR2. Here we show that DDR2 is also unusual in that it requires Src activity to be maximally tyrosine-phosphorylated, and that Src activity also promotes association of DDR2 with Shc. The interaction with Shc involves a portion of Shc not previously implicated in interaction with receptor tyrosine kinases. These results identify Src kinase and the adaptor protein Shc as key signaling intermediates in DDR2 signal transduction. Furthermore, Src is required for DDR2-mediated transactivation of the matrix metalloproteinase-2 promoter. The data support a model in which Src and the DDR2 receptor cooperate in a regulated fashion to direct the phosphorylation of both the receptor and its targets.