(A) In PDXs derived from Patient 1 tumor tissue, both cetuximab (100µg/dose) and the combination (cetuximab 100µg/dose and MM-121 300ug/dose) significantly inhibited tumor growth in nude mice (p<0.001 for both treatments). There was no significant difference between cetuximab alone and the combination. However, tumors treated with cetuximab alone grew back while no tumor relapse could be detected in the combination group. (B) In PDXs derived from Patient 8, only the combination treatment significantly inhibited tumor growth (p<0.004). Combination treatment was also more effective than either single agent (p<0.032 respectively). (C) As shown by immunoblotting, HER3 expression was induced in cetuximab treated PDX tumor samples, while pAKT was reduced by MM-121 treatment. No samples from the combination-treated PDXs were available for testing as the tumors were too small to isolate sufficient protein sample. n1–3: PDX tumor samples from 3 different PDXs in the control group. c1–3: three different tumor samples from the cetuximab treated group. m1–3: three different tumor samples from the MM-121 treated group. Image represents 3 repeated experiments.