Starting on day 26 after inoculation of MDA453β cells into the mammary fat pads of female ICR SCID mice (4–6 weeks old, 5 mice/group) (A) and starting on day 20 after inoculation of MCF7-HER18/Fluc-GFP cells into the mammary fat pads of female Swiss nude mice (4–6 weeks old, 10 mice/group) (B), the mice were treated with PBS (control), trastuzumab (0.5 mg/mouse twice a week), epoetin alfa (100 U/mouse daily on weekdays), or trastuzumab plus epoetin alfa (same doses and schedules as each treatment alone) for 4 weeks or until mice were sacrificed, whichever came first. Tumor sizes were measured with a digital caliper every other day and plotted as a function of days after tumor cell inoculation. See also Figure S3.