Modified anthracyclines are able to trigger autophagy.

<p>Fraction of autophagic cells in (<b>a</b>) SKOV-3 and (<b>b</b>) HepG2 cancer cell lines. The measurements were carried out in the presence or absence of the inhibitors. The cells were treated with 80 nM concentrations of DOX, O-DOX, DAU or O-DAU and then incubated for 4, 24 or 48 h. Autophagic changes in control cells (without drug treatment) measured after 2, 4, 24 and 48 h incubation were taken as 100%. 3-MA (5 mM) was added to SKOV-3 or HepG2 cell lines in the presence of 80 nM DOX, O-DOX, DAU or O-DAU for a period of 4, 24 and 48 h. (+) p < 0.05—statistically significant differences observed between the investigated probes in comparison to the effect after treatment with the 3-MA inhibitor. (<b>c</b>) Fluorescence images of autophagic SKOV-3 and HepG2 cells after 48 h incubation with 80 nM concentrations of investigated compounds. The left-hand column shows images of cells treated with DOX (A), O-DOX (B), DAU (C), O-DAU (D). Some cells display abnormal morphology: giant cells and elongated cells with protrusions from the plasma membrane (blebbing); cytoplasmic bridges between cells. The right-hand column shows representatives images of single cells with progressive autophagosome formation (autophagy is indicated by bright green staining of autophagic vacuoles–marked by the yellow arrows). (<b>d</b>) Fluorescence images of SKOV-3 and HepG2 cells after 48 h incubation with 80 nM concentrations of investigated compounds. Cells were stained with acridine orange (AO). The left-hand column shows images of cells treated with DOX (A), O-DOX (B), DAU (C), O-DAU (D). The right-hand column shows representative images of single cells with progressive autophagosome formation (autophagy is indicated by bright red staining of autophagosomes–marked by the yellow arrows). (<b>c, d</b>) Cells were analyzed with an inverted fluorescence microscope (Olympus IX70, Tokyo, Japan). Scale bar: 50 μm.