DLBCL cells autocatalyze HGF activation by producing HGFA. Conditioned medium of DLBCL cell lines OCI-LY-3 (left panel) and OCI-LY-10 (middle panel) was incubated with scHGF for 6 hours in the presence of thrombin, combined with either the serine protease inhibitor leupeptin, neutralizing antibody against HGFA (PI-4), or factor XIIa (OT-2), as indicated. As positive control, HGF conversion by recombinant HGFA is shown (right panel). HGF conversion was determined by immunoblotting with anti-HGF. αHGF indicates active α heavy chain of HGF; scHGF, inactive single chain of HGF; and HC, heavy chain of immunoglobulin.