Novel Therapy for Glioblastoma Multiforme by Restoring LRRC4 in Tumor Cells: LRRC4 Inhibits Tumor-Infitrating Regulatory T Cells by Cytokine and Programmed Cell Death 1-Containing Exosomes

Abstract

Glioblastoma multiforme (GBM) is a heterogeneous malignant brain tumor, the pathological incidence of which induces the accumulation of tumor-infiltrating lymphocytes (TILs). As a tumor suppressor gene, LRRC4 is absent in GBM cells. Here, we report that the recovery of LRRC4 in GBM cells inhibited the infiltration of tumor-infiltrating regulatory T cells (Ti-Treg), promoted the expansion of tumor-infiltrating effector T (Ti-Teff) cells and CD4+CCR4+ T cells, and enhanced the chemotaxis of CD4+CCR4+ T cells in the GBM immune microenvironment. LRRC4 was not transferred into TILs from GBM cells through exosomes but mainly exerted its inhibiting function on Ti-Treg cell expansion by directly promoting cytokine secretion. GBM cell-derived exosomes (cytokine-free and programmed cell death 1 containing) also contributed to the modulation of LRRC4 on Ti-Treg, Ti-Teff, and CD4+CCR4+ T cells. In GBM cells, LRRC4 directly bound to phosphoinositide-dependent protein kinase 1 (PDPK1), phosphorylated IKKβser181, facilitated NF-κB activation, and promoted the secretion of interleukin-6 (IL-6), CCL2, and interferon gamma. In addition, HSP90 was required to maintain the interaction between LRRC4 and PDPK1. However, the inhibition of Ti-Treg cell expansion and promotion of CD4+CCR4+ T cell chemotaxis by LRRC4 could be blocked by anti-IL-6 antibody or anti-CCL2 antibody, respectively. miR-101 is a suppressor gene in GBM. Our previous studies have shown that EZH2, EED, and DNMT3A are direct targets of miR-101. Here, we showed that miR-101 reversed the hypermethylation of the LRRC4 promoter and induced the re-expression of LRRC4 in GBM cells by directly targeting EZH2, EED, and DNMT3A. Our results reveal a novel mechanism underlying GBM microenvironment and provide a new therapeutic strategy using re-expression of LRRC4 in GBM cells to create a permissive intratumoral environment.

Extracellular vesicles, news about their role in immune cells: physiology, pathology and diseases

“…At the time, progress was expected particularly for the EV-based immunotherapies [65][66][67]. When transported by EVs, this gene can ultimately inhibit the proliferation of regulatory T cells that infiltrate the tumour [68]. A few examples have already been reported in this review [48,50,62].…”

“…The therapeutic mechanism is based on the re-expression, within these cancer cells, of leucine-rich repeat C4 (LRRC4), a tumour suppressor gene. When transported by EVs, this gene can ultimately inhibit the proliferation of regulatory T cells that infiltrate the tumour [68]. Another approach, already promising for in-vivo therapy of breast cancer, is based on the engineering of MSC cells competent for the release of EVs enriched in the microRNA, miR-379.…”

LRRC4 Suppresses E-Cadherin-Dependent Collective Cell Invasion and Metastasis in Epithelial Ovarian Cancer

“…LRRC4 (Leucine-rich repeat-containing protein 4) is a transmembrane and cytoplasmic protein and plays an important role in neural development and malignant transformation of glioma (14)(15)(16)(17)(18). We had previously shown that LRRC4 binds to PAR6 and serves as a partner of PAR complex in the neuron polarity (14).…”

“…We had previously shown that LRRC4 binds to PAR6 and serves as a partner of PAR complex in the neuron polarity (14). LRRC4 deletion contributes to glioblastoma multiforme (GBM) malignant progression, while LRRC4 overexpression inhibits GBM cell proliferation and invasion by inhibiting the RTK/ERK/AKT/NF-kB signaling pathway (15)(16)(17)(18). LRRC4 binds to ERK1/2 directly and recruits ERK1/2 to the cytoplasm (17).…”

“…LRRC4 deletion contributes to glioblastoma multiforme (GBM) malignant progression, while LRRC4 overexpression inhibits GBM cell proliferation and invasion by inhibiting the RTK/ERK/AKT/NF-kB signaling pathway (15)(16)(17)(18). LRRC4 binds to ERK1/2 directly and recruits ERK1/2 to the cytoplasm (17). In addition, we previously unveiled signaling loops involving LRRC4, AP-2, miR-182, and LRRC4 (the LRRC4-AP-2-miR-182-LRRC4 loop) and LRRC4, miR-185, SP1, DNMT1, and LRRC4 (the LRRC4-miR-185/SP1-DNMT1-LRRC4 loop), which play important role in glioma (18).…”