Modulation of histone acetylation is currently being explored as a therapeutic strategy in treatment of cancer. Specifically, inhibition of historic deacetylase by trichostatin A (TSA) has been shown to prevent tumorigenesis and metastasis. In the present paper we demonstrate that increased historic acetylation by TSA-treated 3T3 cells decreases mRNA as well as zymographic activity of gelatinase A, a matrix metalloproteinase, which is itself, implicated in tumorigenesis and metastasis. Furthermore, TSA inhibits cytochalasin D-induced activation of gelatinase A, but TSA does not affect other members of the gelatinase A activation complex, MT1-MMP and TIMP-2. Thus, TSA is a selective and potent inhibitor of expression and activation of gelatinase A. This finding not only strengthens the rationale for continuing to investigate the therapeutic utility of TSA in cancer, but also, provides evidence that TSA inhibition of gelatinase A expression and activation can be used as a biological marker to monitor and determine end-points of clinical trials involving TSA. (C) 2002 Elsevier Science (USA). All rights reserved.