Abstract A060: Targeting glioma-macrophage interplay via LOX in PTEN-deficient glioblastoma

Glioblastoma multiforme (GBM) is the most lethal form of brain cancer in adults. The median survival of GBM patients is only about one year after initial diagnosis. Genomic profiling has stratified GBM into various subgroups, which are driven by specific genetic alternations of core signaling pathways, including RTK/RAS/PI3K/PTEN, P53/ARF/MDM2 and RB/CDKN2A pathways. However, targeted therapies, such as therapy against EGFR, have failed in the clinic, and no effective therapeutic drugs are available to target tumor suppressors. A key reason for therapeutic failure is inter- and intra-tumoral cancer cell genetic instability and heterogeneity, resulting in aberrant activation of multiple signaling pathways within and across tumors. Stromal/immune cells in the tumor microenvironment (TME) are genetically stable, which not only play a pivotal role in GBM progression by affecting multiple cancer hallmarks, but can also be educated by cancer cells. However, whether and how the behavior and function of specific stromal/immune cells in the TME are regulated by cancer cell with specific genetic alterations in GBM remain relatively undefined. Utilizing a large scale of bioinformatic analysis in TCGA GBM patients, we revealed that genetic alteration (deletion/mutation) of PTEN in GBM patients specifically triggers immune response by promoting macrophage recruitment, without affecting macroglia and other immune cells. Using unbiased transcriptome profiling following functional validation, we identified that lysyl oxidase (LOX) is preferentially secreted by PTEN-deficient cancer cells. In vitro transwell migration assay and in vivo Matrigel Plug assay demonstrated that LOX is a potent macrophage chemoattractant. Transcriptome profiling following Gene Set Enrichment Analysis (GSEA) and functional validation demonstrated that activation of SRC and AKT signaling pathways drives LOX upregulation in PTEN-deficient cancer cells. Genetic and pharmacologic inhibition of LOX in PTEN-deficient cancer cells does not affect tumor cell proliferation in vitro, but markedly inhibits macrophage density and tumor growth in vivo. Using the bioinformatics analysis in clinical GBM samples, we demonstrated that LOX is enriched in GBM patients with higher macrophage density, and that these patients show lower survival. Together, our findings highlight the significance of PTEN-LOX axis in macrophage infiltration in GBM, and demonstrate a possibility of improving GBM treatment by targeting this axis-mediated macrophage recruitment. Citation Format: Peiwen Chen, Alan Wang, Ronald DePinho. Targeting glioma-macrophage interplay via LOX in PTEN-deficient glioblastoma [abstract]. In: Proceedings of the Fourth CRI-CIMT-EATI-AACR International Cancer Immunotherapy Conference: Translating Science into Survival; Sept 30-Oct 3, 2018; New York, NY. Philadelphia (PA): AACR; Cancer Immunol Res 2019;7(2 Suppl):Abstract nr A060.