Abstract 347: Tumor necrosis factor related apoptosis inducing ligand (TRAIL)-induced cytokine production in TNBC promotes neutrophil chemotaxis and immune suppression

Abstract Background: TRAIL induces apoptosis in many preclinical cancer models including breast cancers and has been extensively studied as a potential cancer therapeutic. However, its efficacy in clinical trials is limited, suggesting an unknown modulatory mechanism responsible for lack of TRAIL activity in vivo. Here, we describe that TRAIL treatment elicits transcriptional changes in TNBC cells that alter the immune milieu. Method: We performed RNAseq of MDA-MB-231 cells treated with TRAIL for different time points, followed by validation with RT-PCR in various TNBC cells. RNAi, silencing key differentially regulated genes, along with RT-PCR, ELISA and CHIP assays, were used to validate RNAseq findings. Elucidation of the functional relevance of the outcome was supported both in vitro and in vivo by chemotaxis assay, cytotoxicity assay, RNAseq analysis of donor isolated neutrophils and intravital microscopy, CODEX analysis in TNBC xenografts from mice treated with the TRAIL respectively. Results: TRAIL treatment of the TNBC significantly induced expression of several cytokines, such as CXCLs 1, 2, 3, 8, 11 and IL6, both in vitro and in vivo which are known to affect neutrophil function. Mechanistically, induction of these cytokines was predominantly mediated by death receptor 5 and caspase-8 protein, but not caspase-8 enzymatic activity. GSEA of the RNAseq data indicated that NFKB pathway was significantly enriched. Concordantly, we confirmed that both canonical NFKB1 and non-canonical NFKB2 pathways were activated by TRAIL in vitro and in vivo. However, the induction of the cytokine mRNAs was primarily dependent on the NFKB2 pathway. Neutrophils isolated from healthy human donors incubated with supernatants from TNBC cells in vitro indicated that TRAIL-induced CXCLs and IL6 significantly increased neutrophil chemotaxis. Additionally, CODEX analysis as well as intravital imaging confirmed that TRAIL treatment increases the number of neutrophils in the tumor. Preincubation of neutrophils with supernatants from TRAIL-treated TNBC significantly inhibited their cytotoxic effect against TNBCs. Further, transcriptome analysis of neutrophils incubated with either TRAIL or supernatant of TRAIL treated TNBC revealed significant enrichment of expression of inflammatory cytokine genes, immune modulating and immune checkpoint genes like PDL1. Functional studies with these neutrophils confirmed their suppressive effect on T cell function as well as the effect of TRAIL on decreased neutrophil apoptosis. Conclusion: Collectively, our study suggests the novel role of TRAIL-induced NFKB2-dependent cytokine production promoting neutrophil chemotaxis and immune suppression. This study implies that alterations in the innate immune system may modulate the effects of TRAIL on TNBC tumors. Citation Format: Manjari Kundu, Yoshimi Endo Greer, Lisa Ann Ridnour, David A Wink, Yeap S. Ng, Roberto Weigert, Stan Lipkowitz. Tumor necrosis factor related apoptosis inducing ligand (TRAIL) -induced cytokine production in TNBC promotes neutrophil chemotaxis and immune suppression abstract. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts) ; 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84 (6Suppl): Abstract nr 347.