Construction and expression of intracellular anti-ATF-1 single chain Fv fragment: A modality to inhibit melanoma tumor growth and metastasis

The expression of the transcriptional regulators activating transcription factor-1 (ATF-1) and cAMP-responsive element (CRE)-binding protein (CREB) is upregulated in metastatic melanoma cells. However, how overexpression of ATF-1/CREB contributes to the acquisition of the metastatic phenotype is unclear. Monoclonal antibodies against ATF-1 have previously been used to inhibit the transcriptional activity of ATF-1 and its associated proteins. Here, the effect of disrupting ATF-1 activity was investigated using intracellular expression of an inhibitory anti-ATF-1 single chain antibody fragment (ScFv). Intracellular expression of ScFv anti-ATF-1 in human melanoma cells caused significant reduction in CRE-dependent promoter activation. In addition, expression of ScFv anti-ATF-1 in melanoma cells suppressed their tumorigenicity and metastatic potential in nude mice. Furthermore, expression of ScFv anti-ATF-1 rendered the melanoma cells susceptible to thapsigargin-induced apoptosis in vitro and caused massive apoptosis in vivo in tumors transplanted subcutaneously into nude mice. These studies demonstrate the potential usage of ScFv anti-ATF-1 as an inhibitor of tumor growth and metastasis of solid tumors overexpressing ATF-1/CREB.