Abstract P3-07-52: Identification of serum biomarkers associated with Akt inhibitor MK-2206-induced toxicity in a pre-surgical breast cancer (BC) trial
Authors: Mundi PS , Chen E , Sparano J , Andreopoulou E , Taback B , Wiechmann L , Feldman S , Ananthakrishnan P , Hibshoosh H , Connolly E , Crew K , Maurer M , Hershman DL , Kalinsky K 
Published: May 2016

Abstract
Background: The PI3K/Akt/mTOR pathway is an important oncogenic driver in BC. A major hurdle in clinical Akt inhibitor development has been dose-limiting toxicities, such as rash. To facilitate the risk assessment of Akt inhibitor associated toxicity, we hypothesize that circulating biomarkers can be identified in proteins secreted by the tumor or tumor microenvironment and systemic response after treatment. Exosomes are small membrane bound vesicles containing proteins, mRNA, miRNA, and lipids that are secreted from host cells and remain viable after long-term storage of blood. In this study, we focused on identifying biomarkers associated with drug rash from serum exosomes in BC patients treated with the Akt inhibitor MK-2206.
Methods: In an open-label pre-surgical trial, 2 doses of weekly MK2206 were administered to patients (pts) with stage I-III invasive BC: first at day -9 and second at day -2 from surgery. Sera were collected before and after MK2206. 200 μL of serum was used to isolate total exosomes by precipitation and centrifugation, followed by trypsin digestion and multiplexing labeling analysis. The Orbitrap mass spectrometer was used to acquire LC-MS/MS data. 1,053 unique proteins were identified from the uniProt database. Maximum false discovery rate level (FDR) for predictive biomarkers was controlled at 26% (q&lt;0.26). Analysis was conducted on pre-MK-2206 and post-MK-2206 treated sera from pts to develop a protein signature associated with rash and identify candidate biomarkers of MK-2206-associated rash.
Results: The study was discontinued after 12 pts were enrolled due to toxicity. Notably, an acneiform/maculopapular rash was observed in 5 pts. Unsupervised principal component analysis on the pre-MK-2206 specimens and the entire set of 1,053 proteins demonstrated that 4 of the 5 pts with rash formed a distinct cluster. 30 proteins were differentially expressed in pre-MK-2206 samples from pts who developed rash vs. no rash (q&lt;0.26), with ≥1.5 fold difference in expression level in those with rash after MK-2206. Ingenuity pathway analysis revealed statistically significant over-representation of pathways involved in lipid metabolism (including MALRD1, AWAT2), nucleic acid synthesis (PPAT, ADSLL1), and protein synthesis (PPIB). 45 proteins were significantly different in post-MK-2206 samples (q&lt;0.285). Lipid metabolism was the most significantly over-represented pathway in post-MK-2206 samples.
Conclusions: We demonstrated that mass spectrometry-based proteomic analysis of patient-derived serum exosomes is a promising approach to study drug-induced toxicity. We found significant changes of circulating proteins before and after MK-2206. Increased expression of different proteins involved in lipid metabolism appears to predict skin toxicity, commonly seen with PI3K/Akt pathway inhibitors. Since the PI3K/Akt signaling pathway plays a role in physiological regulation of lipid metabolism, lipid metabolic profiles of BC patients might be important for predicting the risk and controlling toxicity induced by Akt inhibitors. These toxicity-associated biomarkers should be validated and then assessed prospectively in clinical trials.
Citation Format: Mundi PS, Chen E, Sparano J, Andreopoulou E, Taback B, Wiechmann L, Feldman S, Ananthakrishnan P, Hibshoosh H, Connolly E, Crew K, Maurer M, Hershman DL, Kalinsky K. Identification of serum biomarkers associated with Akt inhibitor MK-2206-induced toxicity in a pre-surgical breast cancer (BC) trial. [abstract]. In: Proceedings of the Thirty-Eighth Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2015 Dec 8-12; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2016;76(4 Suppl):Abstract nr P3-07-52.