The effects of several individual and combined treatments on E2F1 phosphorylation and ATM/Chk2 activation in MDA-MB-231 cells. (A) The phosphorylation status of E2F1 in response to treatments was determined by MALDI-TOF mass spectroscopy. Peptides were analysed in untreated MDA-MB-231 cells (control) or those treated for 3 days with 1 μM 4OHT; 10 μM TMCG and 5 μM DIPY (TMCG/DIPY); or 10 μM TMCG, 5 μM DIPY, and 1 μM 4OHT (TMCG/DIPY/4OHT). The relative intensities of specific tryptic peptides were normalised to an internal matrix control. (B) MDA-MB-231 cells subjected to the above-described treatment were analysed by immunofluorescence for p-ATM (green), p-Chk2 (red) and DAPI (blue).