Xenograft Models of Breast Cancer

Animal studies were approved by the Dartmouth College IACUC. Female NOD-scid/IL2Rγ^−/− (NSG; NOD.Cg-Prkdcscid Il2rgtm1Wjl/SzJ) mice (6–7 wks old; obtained from the Norris Cotton Cancer Center Transgenic & Genetic Construct Shared Resource) were subcutaneously injected with 5–10×10⁶ MCF-7 cells in matrigel (BD Biosciences), or orthotopically implanted with ~8-mm³ fragments of serially transplanted HCI-003 patient-derived xenograft tissue [a gift from Alana Welm, Univ. of Utah (27 (link))] in the inguinal #4 mammary fat pad; mice were subcutaneously implanted on the same day with a 17β-estradiol pellet (0.72 mg, 60-day-release; Innovative Research of America). In mice subcutaneously injected with T47D/FR cells, subcutaneous administration of 5 mg/wk fulv was initiated on the same day [clinical formulation; provides ER inhibition in MCF-7 tumors for ≥8 d (data not shown); kindly provided by AstraZeneca]. Mice bearing tumors 500–1,000 mm³ were randomized to treatment with vehicle, 5 mg/kg fulv QW, GDC-0941 (100 mg/kg QDx5d QW, 100 mg/kg BIDx3d QW, or 800 mg/kg QW, p.o. in 100 µL 0.5% methylcellulose/0.2%Tween-80), and combinations. Tumor volumes were measured twice weekly using calipers (volume = length²×width/2). Tumors were harvested and cut in pieces for snap-freezing or formalin fixation followed by paraffin embedding (FFPE).