Abstract 253: Protein-tyrosine phosphatase 1B (PTP1B) as a therapeutic target in glioblastoma

New targeted therapies are urgently needed in glioblastoma (GBM). IL13Rα2 receptor is considered a highly specific receptor for GBM cells and has been proposed for therapeutic purposes. Here, we aimed to identify the protein interaction network of IL13Rα2 and its mediators in GBM searching for novel associated therapeutic targets. We investigated the IL13Rα2 protein interaction network in U251 GBM cells using immunoprecipitation followed by mass spectrometry. Different cell lines were used for validation. Two glioblastoma cell lines were used for testing proliferation, adhesion, migration and invasion. Claramine, a PTP1B inhibitor, was tested to study inhibition of GBM cells growth in cultured cells and in animal experiments. In vivo experiments with NSG mice were performed after treatment with PTP1B inhibitors. Using a proteomic approach, we identified the association of the PTP1B phosphatase with IL13Rα2 in U251 GBM cells. Although GBM cell lines were positive for PTP1B, the highest PTP1B expression was found in GBM clinical samples. Moreover, “in silico” dataset analysis showed PTP1B association with poor outcome in GBM patients. PTP1B silencing inhibited the IL-13-promoted activation of Src (Tyr419), AKT and ERK1/2 in all the cell lines tested causing a significant effect on IL-13-mediated migration and invasion, and proliferation at a lower extent, of GBM cells. Therefore, PTP1B-silencing reverted most of the pro-metastatic capacities of the IL-13/ IL13Rα2 signaling axis. Further immunoprecipitation of PTP1B showed its association with a large number of NF-κB and NOTCH-related proteins in GBM cells. Both pathways are highly relevant for cancer proliferation and invasion. Claramine, a selective inhibitor of PTP1B, caused similar results to PTP1B silencing, inhibiting the dephosphorylation of Src Tyr527, migration and invasion in GBM. Moreover, treatment with Claramine caused a complete regression of GBM xenografts in NSG mice and total inhibition of liver metastatic growth in nude mice inoculated with colorectal cancer cells. In conclusion, our results provide new insights into the mechanisms underlying IL13Rα2-driven GBM aggressiveness after identifying PTP1B as a critical mediator of IL-13/IL13Rα2 signaling. A PTP1B inhibitor such as Claramine showed a great value as a therapeutic candidate in GBM. PTP1B inhibitors might be highly effective to prevent GBM progression and invasion. Citation Format: Ruben Bartolome, Marta Jaen, Miranda Burdiel, Irina V. Balyasnikova, Ignacio Casal. Protein-tyrosine phosphatase 1B (PTP1B) as a therapeutic target in glioblastoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 253.