Abstract A07: MTI-101 induces synergistic cell kill in combination with Erlotinib in EGFR-driven lung cancer models.
Authors: Blumencranz Lisa E. , Nair Rajesh R. , McLaughlin Mark L. , Haura Eric B. , Hazlehurst Lori A. 
Published: August 2014

The epidermal growth factor receptor (EGFR) is a well-characterized oncogene that is mutated in approximately 10% of U.S. non-small cell lung cancer (NSCLC) patients. EGFR has understandably emerged as an important target for the treatment of this molecular subset of NSCLC patients. The use of tyrosine kinase inhibitors (TKIs) such as Erlotinib has been shown to prolong survival in metastatic NSCLC. However, clinical evidence indicates that the emergence of resistance can limit the overall success of EGFR inhibitors. Gatekeeper mutations account for approximately 50% of cases in which patients relapse with resistant disease. In the remaining 50% of resistant patients, other mechanisms of resistance include overexpression of cMET and transition to an EMT phenotype. These clinical statistics highlight the immediate need for the development of novel combination strategies for the treatment of EGFR driven lung cancer that would further improve patient outcomes. Our laboratory has been developing a novel cyclic peptide that we previously showed binds to a CD44/VLA-4 integrin complex and induces necrotic cell death in myeloma models. Consistent with what we previously reported in myeloma, in this report we show that MTI-101 induces caspase independent cell death in EGFR driven NSCLC tumor cells lines, PC9 and HCC4006. Moreover, we show that MTI-101 treatment results in ATP depletion, increased ROS levels, and depolarization of the mitochondrial membrane potential, all hallmarks of necrotic cell death. Additionally, MTI-101 was not cross-resistant in PC9 cells selected for resistance to Gefitinib (PC9/GR harboring a gatekeeper mutation) nor HCC4006 cells resistant to Erlotinib (HCC4006/ER demonstrating EMT phenotype). To delineate the cell surface targets responsible for MTI-101's actions in EGFR driven NSCLC, we utilized biotinylated MTI-101 coupled to LC-MS/MS, and discovered EGFR, CD44, β1, β4, α3 and α6 integrins were among the key molecules found in the binding complex. We are currently working to analyze the causative role of these proteins in relationship to MTI-101's mechanism of cell death in EGFR driven NSCLC. Due to the fact that EGFR was contained in the complex, we reasoned that MTI-101 in combination with Erlotinib may result in increased cell kill. In this report we show that the combination is synergistic. Furthermore, pre-treatment with Erlotinib enhances MTI-101 induced depletion of ATP levels, suggesting that the mechanism underlying synergy occurs in the necrotic cell death pathway. Interestingly, as a single agent, we discovered that MTI-101 leads to decreased activity of EGFR and PI3K. In light of this promising in vitro activity, we tested MTI-101 as a single agent and in combination with Erlotinib using an in vivo model. In this report we show increased activity in the combination treatment as determined by (i) decreased bone tumor burden contained in the tibia, (ii) decreased lung tumor nodules and, (iii) increased survival data. Taken together, our data demonstrates that rationally combining MTI-101 with an EGFR inhibitor has the potential to be an effective treatment option in EGFR driven lung cancer.

Citation Format: Lisa E. Blumencranz, Rajesh R. Nair, Mark L. McLaughlin, Eric B. Haura, Lori A. Hazlehurst. MTI-101 induces synergistic cell kill in combination with Erlotinib in EGFR-driven lung cancer models. [abstract]. In: Proceedings of the AACR-IASLC Joint Conference on Molecular Origins of Lung Cancer; 2014 Jan 6-9; San Diego, CA. Philadelphia (PA): AACR; Clin Cancer Res 2014;20(2Suppl):Abstract nr A07.