Abstract 5867: Multimodal analysis of glioblastoma identifies the additional function of CXCL12 for modulating GBM resistance and immunosuppressive microenvironment
Authors: Liu Chan-Chuan , Chien Chia-Hung , Yang Wen-Bin , Chuang Jian-Ying , Chang Kwang-Yu 
Published: April 2023

Abstract
Glioblastoma (GBM), a WHO Grade IV glioma, is the most common and aggressive primary brain tumor. Despite the standard of care consisting of surgery removal following radio- and chemo- therapy, the prognosis of GBM patients remain dismal. The interplay between GBM cells and its microenvironment contributes to maintaining the cancer stemness, developing resistance, and forming immunosuppression. GBM-associated macrophages (GAMs) are recruited to the GBM microenvironment by cytokines/chemokines. Conversely, GAMs may promote GBM progression. Therefore, we hypothesized that GBM cells modulated immune microenvironment via macrophage activation. We integrated the bulk RNA sequencing (seq.) of the paired primary-recurrent GBM specimens, single-cell RNA seq., and in vitro validation to investigate the hypothesis. The bulk RNA seq. of the paired primary-recurrent GBM specimens indicated that recurrent GBM enhanced the neuroinflammation pathway. Among the components, we found that CXCL12, also known as stromal cell-derived factor 1 was accumulated during GBM progression and up-regulated in temozolomide (TMZ)-resistant GBM cells. On the other hand, the newly CXCL12 receptor CXCR7 may act as a scavenger for CXCL12 during developing TMZ resistance in GBM. The bulk RNA sequencing seq. from primary-recurrent GBM specimens showed the decrement of CXCR7. Single-cell RNA seq. of GBM patients’ specimens indicated CXCR7 dominantly expressed in GBM cells other than normal neural and immune cells. Developing TMZ resistance in GBM cell lines down-regulated CXCR7 expression. Furthermore, silencing CXCR7 attenuated TMZ cytotoxicity while combining CXCR7 agonists (Plerixafor, VUF11207, and TC14012) and TMZ enhanced TMZ cytotoxicity. Otherwise, the GBM-associated CXCL12 activated M0 macrophages into GAMs by facilitating macrophage proliferation and inducing pro-tumor factors, including interleukine (IL)-1β and its receptors, IL-6, MMP9, and immune checkpoint PD-L1. Mechanistically, GBM-associated CXCL12 upregulated PD-L1 in GAMs via NF-κB. Accordingly, by multimodal analysis, CXCL12 was identified with the additional role in regulating resistance in GBM cells and GBM microenvironment. Also, re-activating CXCR7 may overcome the resistance to TMZ and immune checkpoint blockade therapy. Combination of CXCR7 activation with current therapy and immunotherapy may be an effective strategy for improving the prognosis of primary GBM patients.
Citation Format: Chan-Chuan Liu, Chia-Hung Chien, Wen-Bin Yang, Jian-Ying Chuang, Kwang-Yu Chang. Multimodal analysis of glioblastoma identifies the additional function of CXCL12 for modulating GBM resistance and immunosuppressive microenvironment [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 5867.