HR-MRS and CEST-MRI of cell extracts from doxorubicin treated MCF-7 and MDA-MB-231 breast cancer cells compared to the respective vehicle controls. (A) HR-MRS quantification (n=3 each) shown as difference between doxorubicin treated cell extracts minus untreated vehicle controls (dotted horizontal line at 0) in fmol per cell following treatment with 5 µM doxorubicin for 24 hours in MCF-7 (gray bars) and MDA-MB-231 (white bars) cells. (B) CEST-MRI of MDA-MB-231 cell extracts showing doxorubicin treated cells (gray squares, n=3) versus vehicle controls (black circles, n=3). (C) CEST-MRI quantified as adjusted MTRasym, which is defined as MTRasym per cell of treated cells minus vehicle controls (n=3 each), in MCF-7 (blue triangles) and MDA-MB-231 (red squares) cells. Values are mean ± standard error. * p< 0.05, treated versus control.