Abstract 4119: Tyrosine phosphorylation of MACC1 is essential and druggable for colorectal cancer metastasis restriction

We identified the previously undescribed gene Metastasis Associated in Colon Cancer 1 (MACC1). MACC1 is a metastasis inducer and prognostic biomarker for colorectal cancer (CRC). MACC1 has meanwhile been confirmed as decisive driver for tumorigenesis and metastasis for a broad variety of solid cancers. Here we aim to identify the impact of defined tyrosine phosphorylations on the function of the metastasis inducer MACC1. In silico identified MACC1 tyrosine phosphorylation (pY) sites were ranked and most promising positions were site-directed mutated in wildtype (wt) MACC1 constructs. Human CRC cells were transduced with these constructs. Tyrosine phosphorylation was quantified by selected reaction monitoring (SRM)-mass spectrometry. Effects of pY-MACC1 mutants on cell migration, proliferation, dissemination and colony formation were assessed in cell culture as well as on liver metastasis formation in human CRC-xenografted mice. To identify MACC1-phosphorylating kinases the MACC1 interactome was identified using mass spectrometry. Most promising binding partners were validated by immunoprecipitation. Impact of inhibitors targeting kinases phosphorylating MACC1 was assessed on MACC1-induced tumor growth and liver metastasis in human CRC-xenografted mice by in vivo imaging. We report that tyrosine phosphorylation of MACC1 is hierarchical and essential for motility and proliferation in cell culture, as well as for tumor growth and metastasis in mice. We identified kinases for MACC1 phosphorylation. Targeting these kinases using inhibitors employed in clinical trials restricts MACC1-induced tumor growth and metastasis in mice. MACC1 tyrosine phosphorylation is crucial for metastasis and is druggable by small molecule inhibitors. This fundamental finding opens new therapeutic options for inhibition of MACC1-induced cancer metastasis. Citation Format: Dennis Kobelt, Gunnar Dittmar, Claudia Fleuter, Janice Smith, Mathias Dahlmann, Rebekka Migotti, Peter M. Schlag, Ulrike S. Stein. Tyrosine phosphorylation of MACC1 is essential and druggable for colorectal cancer metastasis restriction. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 4119. doi:10.1158/1538-7445.AM2015-4119