Cytotoxic effects of mithramycin DIG-MSK can depend on the rise of autophagy

© 2015 Elsevier Ltd. DIG-MSK (demycarosil-3D-β-d-digitoxosyl mithramycin SK; EC-8042), a novel analogue of mithramycin A, induced autophagy in HCT116 human colon carcinoma and, to a lesser extent, in A2780 human ovarian carcinoma cell lines, which was followed by apoptosis and/or necrotic cell death in a timedependent way. The effects of DIG-MSK included changes in the expression of a set of genes involved in autophagy, the progression of cells through the different phases of cell cycle, and their halting at the checkpoints. Cells treated with the glucose analogue 2-DG (2-deoxy- d-glucose), which induces autophagy because it impairs cell metabolism, or cotreated with 2-DG plus DIG-MSK, also showed altered gene expression and autophagy. In A2780 cells, some genes involved in autophagy were down-regulated by the different treatments, yet the levels of the proteins they encode could be enough to ensure autophagic flux. In HCT116 cells, up-regulation of several pro-autophagic genes resulted in strong autophagic response. Acidic cell organelles and autophagic flux were more evident in HCT116 than in A2780 cells. DIG-MSK was still cytotoxic in cells that underwent autophagy induced by 2-DG. Therefore, we verified that autophagy resulting from a stress response did not protect cells against DIG-MSK, but, instead, autophagy promoted by either 2-DG or the novel mithralogue can enhance the antitumour activity, which depended on the cell typeThis work was partially 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. Carolina Vizcaíno was recipient of a JAE-Predoc2010 fellowship (CSIC), cofinanced by the European Social FundPeer reviewe