(A) Seahorse analysis of ECAR at baseline in 1mM glutamine, 1mM pyruvate without glucose and following injection of 16mM glucose (Medium) or glucose supplemented with 500nM recombinant t-Darpp (t-Darpp). (B) SK-BR-3 cells were pre-treated in media minus or plus 5µM NVP-AEW for one hour. ECAR was analyzed at baseline in 1mM glutamine, 1mM pyruvate and 16mM glucose and following injection of medium supplemented with 500nM recombinant t-Darpp, the data is presented as net change in ECAR following injection. (C) Western blot analysis of IGF-1R and Akt phosphorylation following treatment with recombinant t-Darpp protein (left) and the effect of IGF-1R inhibition with NVP-AEW prior to treatment with recombinant t-Darpp (right) Numbers indicate fold change compared to untreated samples after normalization to total protein (D) Western analysis comparing Akt phosphorylation following treatment with recombinant t-Darpp (400nM), an inhibitory IGF-1R monoclonal antibody (Ab) or both. (E) Percent change in ECAR following treatment with 500nM recombinant t-Darpp of a panel of breast cancer cell lines (SK-BR-3, BT474, T47D, MCF7, HCC1937 and MDA-MB-231). Shown is the mean change in ECAR normalized to untreated controls (n=3–6). *p<0.05, **p<0.01 ***p<0.001 ****p<0.0001