AKT/mTOR/HER/PI3K family proteins and phospho-proteins as predictors of pCR for early stage breast cancer patients treated with the AKT inhibitor MK2206 in the I-SPY 2 TRIAL (NCT01042379)

The AKT inhibitor MK2206 (M) was one of the experimental agents evaluated in I-SPY 2, a neoadjuvant platform trial for high risk, early stage breast cancer, and graduated in the HER2+, HR-, and HR-HER2+ signatures. Based on the hypotheses that since MK2206 is an enzymatic inhibitor of AKT, response to MK2206 may be predicted by the relative pre-treatment levels of phosphorylation of AKT kinase substrates, in pre-defined analyses we assessed 26 well known proteins/phospho-proteins in the HER-AKT-mTOR pathway to test their association with pCR in the MK2206 arm, in both HER2+ and HER2- subsets. We specifically used laser capture microdissection (LCM)- enriched tumor epithelium cell isolates from the clinical biopsy specimens as the sample input for all protein pathway activation analysis, which has been shown to be critical in accurate measurement of ubiquitously expressed and activated signaling proteins. To the best of our knowledge, this work represents the first rigorous study of association between direct measurement of AKT pathway activation using phospho-protein activation levels and response to MK2206 performed in early stage breast cancer patients. Reverse phase protein array (RPPA) array run on isolates from pre-treatment breast cancer biopsy samples that were first LCM-enriched for epithelial cells. The sample characteristics and their values represent: HER2: the status of the HER2 gene. 1 = positive; 0 = negative. HR: the status of hormone (estrogen and progesterone) receptors. 1 = positive; 0 = negative. pCR: the status of a pathological complete response (pCR). 1 = complete response; 0 = failed complete response Arm: arm of the trial per patient - MK2206 arm' or 'Control arm'. RPPA Array: Platform Array version. Key to convert from raw to normalized data.