cAMP and TNFα signaling converge in MMP-2/MMP-9 secretion and induction of CXCR4 expression by CD34⁺ progenitors. (A) MMP-2 and MMP-9 levels in the conditioned media of CB and MPBL CD34⁺ cells cultured for 24 hours with the indicated agents, as determined by gelatin zymography. Positive control (contr) is the conditioned medium of HT1080 cells. Representative gel and densitometry analysis data are shown as mean ± SD of 3 independent experiments expressed in arbitrary units (AU). Note that the presence of PKCζ PS (PSζ) abrogates MMP-2/MMP-9 secretion by cAMP and TNFα costimulated cells. (B) Membranal CXCR4 expression in MPBL CD34⁺ cells treated as in panel A. Data are shown as mean ± SD of 6 independent experiments. Representative flow cytometry analysis is presented at the bottom. IgG indicates secondary IgG only; CTRL, untreated cells.