Abstract B1-59: Identification of key molecular characteristics for achieving increased anti-tumor activity by combined mTORC1/2 and MEK1/2 investigational agents
Authors: Shin Hyunjin , Krueger Andrew , Li Bin , Blair Derek , Trepicchio William L. , Ecsedy Jeffrey 
Published: May 2016

Abstract
The development of combination therapies is important to cancer treatment due to the potential to target multiple oncogenic pathways together, which may lead to enhanced anti-tumor activity and decreased chance for resistance. The RAS/RAF/MEK/ERK (MAP kinase) and PI3K/AKT/mTOR pathways are well-known pathways driving the oncogenic process in many cancer types; therefore, the simultaneous inhibition of these pathways may produce increased anti-tumor activity. It is important to find ideal cancer indications and molecular subtypes that may be most sensitive to drug combination inhibiting these pathways; this requires understanding of the molecular and genetic underpinnings. In this study, an in-vitro cell viability assay on 240 cancer cell lines was used to reveal the synergy mechanisms of the combination of investigational agents MLN0128 (mTORC1/2 inhibitor) with TAK733 (MEK1/2 inhibitor). Cells were administered with MLN0128 and TAK733 in DMSO in ten 2-fold serial dilutions and cell viability was measured using Promega's CellTiter-GLO® assay after a 72 hour incubation period. The 100 data points (10×10) were fit to a 9-parameter model to obtain a response surface for each cell line and the effect of the combined administration was measured using a non-linear blending score. Our previous study found that genes in the MAP kinase pathway such as KRAS, NRAS, or BRAF were mutated in cell lines demonstrating synergy. In this study, a 76-gene expression signature was additionally identified using a regression-based analysis. The 76 mRNAs include some genes within the two oncogenic pathways, as well as those that regulate feedback of the MAP kinase pathway and cross-talk between the pathways. A pathway and protein-protein interaction network-based analysis of the 76-gene signature and mutated genes suggest that the activation of the MAP kinase pathway in cells originally resistant to MLN0128 may be essential for a synergistic outcome from the MLN0128 and TAK733 combination. Cell lines with activating mutations or over-expressed genes in MAP kinase pathway are generally sensitive to TAK733 administration; these cell lines also demonstrated synergy to the combination of MLN0128 and TAK733. On the other hand, cell lines with highly expressed PI3K tend to antagonistically respond to the combination. In conclusion, our study suggests the key molecular conditions of cell lines in order to achieve increased anti-tumor activity by the combination of MLN0128 and TAK733. These findings can be utilized to establish a better-differentiated strategy in terms of patient stratification for the combination therapy using MLN0128 and TAK733.
Citation Format: Hyunjin Shin, Andrew Krueger, Bin Li, Derek Blair, William L. Trepicchio, Jeffrey Ecsedy. Identification of key molecular characteristics for achieving increased anti-tumor activity by combined mTORC1/2 and MEK1/2 investigational agents. [abstract]. In: Proceedings of the AACR Special Conference on Computational and Systems Biology of Cancer; Feb 8-11 2015; San Francisco, CA. Philadelphia (PA): AACR; Cancer Res 2015;75(22 Suppl 2):Abstract nr B1-59.