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The HER2 receptor and its MUC4 mucin partner form an oncogenic complex via an extracellular region of MUC4 encompassing three EGF domains that promotes tumor progression of pancreatic cancer (PC) cells. However, the molecular mechanism of interaction remains poorly understood. Herein, we decipher at the molecular level the role and impact of the MUC4EGF domains in the mediation of the binding affinities with HER2 and the PC cell tumorigenicity. We used an integrative approach combining in vitro bioinformatic, biophysical, biochemical, and biological approaches, as well as an in vivo study on a xenograft model of PC. In this study, we specified the binding mode of MUC4EGF domains with HER2 and demonstrate their “growth factor-like” biological activities in PC cells leading to stimulation of several signaling proteins (mTOR pathway, Akt, and β-catenin) contributing to PC progression. Molecular dynamics simulations of the MUC4EGF/HER2 complexes led to 3D homology models and identification of binding hotspots mediating binding affinity with HER2 and PC cell proliferation. These results will pave the way to the design of potential MUC4/HER2 inhibitors targeting the EGF domains of MUC4. This strategy will represent a new efficient alternative to treat cancers associated with MUC4/HER2 overexpression and HER2-targeted therapy failure as a new adapted treatment to patients.
The MUC4 mucin and its membrane partner ErbB2 form an oncogenic complex at the surface of epithelial cancer cells that promotes tumor progression. They directly physically interact via an extracellular region of MUC4 encompassing three EGF domains opening the route to therapeutic targeting of ErbB2 over‐expressing cancers in which MUC4‐ErbB2 is present. However, before small inhibitory molecules may be designed, it is mandatory (i) to decipher at the molecular level which amino acid regions are involved in the interaction and (ii) show that they mediate cancer cell tumorigenicity. By using in vitro (2D cell culture, Micro Scale Thermophoresis, PLA assay, Co‐IP, GST pull down, Molecular Dynamics simulations) and in vivo (xenograft model of pancreatic cancer) approaches, we show that the EGF1 domain of MUC4 is central both in the interaction with ErbB2 and in the activation of cell proliferation and migration and tumor growth via activation of key oncogenic pathways (Src, Ras, p70S6K/AKT/mTOR, beta‐catenin, FAK). Finally, we have identified hotspots of interaction paving the way to the design of therapeutic inhibitory molecules targeting the EGF domains of MUC4 which may represent a new alternative strategy to overcome ErbB2 therapeutic failure in cancer.
The MUC4 mucin and its membrane partner ErbB2 form an oncogenic complex at the surface of epithelial cancer cells that promotes tumor progression. They directly physically interact via an extracellular region of MUC4 encompassing three EGF domains opening the route to therapeutic targeting of ErbB2 over-expressing cancers in which MUC4-ErbB2 is present. However, before small inhibitory molecules may be designed, it is mandatory (i) to decipher at the molecular level which amino acid regions are involved in the interaction and (ii) show that they mediate cancer cell tumorigenicity. By using in vitro (2D cell culture, Micro Scale Thermophoresis, PLA assay, Co-IP, GST pull down, Molecular Dynamics simulations) and in vivo (xenograft model of pancreatic cancer) approaches, we show that the EGF1 domain of MUC4 is central both in the interaction with ErbB2 and in the activation of cell proliferation and migration and tumor growth via activation of key oncogenic pathways (Src, Ras, p70S6K/AKT/mTOR, β-catenin, FAK). Finally, we have identified hotspots of interaction paving the way to the design of therapeutic inhibitory molecules targeting the EGF domains of MUC4 which may represent a new alternative strategy to overcome ErbB2 therapeutic failure in cancer. Citation Format: Nicolas STOUP, Maxime LIBERELLE, Céline SCHULZ, Romain VASSEUR, Romain MAGNEZ, Xavier THURU, Patricia MELNYK, Nicolas RENAULT, Nicolas JONCKHEERE, Nicolas LEBEGUE, Isabelle VAN SEUNINGEN. The EGF domains of MUC4 oncomucin interact with ErbB2 and mediate tumorigenic activity of cancer cells represent new potential therapeutic targets [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr LB106.
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