The activity of a novel mithramycin analog is related to its binding to DNA, cellular accumulation, and inhibition of Sp1-driven gene transcription

DIG-MSK (demycarosyl-3D-β-d-digitoxosyl-mithramycin SK) is a recently isolated compound of the mithramycin family of antitumor antibiotics, which includes mithramycin A (MTA) and mithramycin SK (MSK). Here, we present evidence that the binding of DIG-MSK to DNA shares the general features of other mithramycins such as the preference for C/G-rich tracts, but there are some differences in the strength of binding and the DNA sequence preferentially recognized by DIG-MSK. We aimed at gaining further insights into the DIG-MSK mechanism of action by direct comparison with the effects of the parental MTA. Similar to MTA, MSK and DIG-MSK accumulated rapidly in A2780, IGROV1 and OVCAR3 human ovarian cancer cell lines, and DIG-MSK was a potent inhibitor of both basal and induced expression of an Sp1-driven luciferase vector. This inhibitory activity was confirmed for the endogenous Sp1 gene and a set of Sp-responsive genes, and compared to that of MTA and MSK. Furthermore, DIG-MSK was stronger than MTA as inhibitor of Sp3-driven transcription and endogenous Sp3 gene expression. Differences in the effects of MTA, MSK and DIG-MSK on gene expression may have a large influence on their biological activities. © 2014 Elsevier Ltd. All rights reserved.This work was supported by grant BFU2010-15518 from the Spanish Ministry of Science and Innovation, and the FEDER program of the European Community, and it was performed within the framework of the “Xarxa de Referencia en Biotecnologia” of the Generalitat de Catalunya. It was also supported by the Principado de Asturias Government through PCTI founds 2006-2009, 80% co-financed with the FEDER Operative Program of the Principado de Asturias 2007-2013 (project FC-11-PC-10-31) and Fondo de Investigaciones Sanitarias (Institute Carlos III) PS09/00420 and PI12/01280. A. F-G. is co-financed by the project COF-11-24 from FICYT. C.V. is recipient of a JAE-Predoc2010 fellowship (CSIC), co-financed by the European Social FundPeer Reviewe