Complement receptor C5aR1 blockade reprograms tumor-associated macrophages and synergizes with anti-PD-1 therapy in gastric cancer.

In gastric cancer (GC), the therapeutic response of immune checkpoint blockade (ICB) remains suboptimal. Targeting myeloid cell checkpoints might be feasible as adjuvant to current ICB regimens. We sought to evaluate the crucial role of C5aR1+ TAMs in regulating antitumor immunity and the efficacy of combinatorial treatment with antiprogrammed cell death protein-1 (PD-1) and C5aR1 blockade. Here, we found that C5aR1 was predominantly expressed on macrophages and high level of C5aR1+ TAMs infiltration could predict poor prognosis and inferior chemotherapeutic response. The flow cytometry (FCM) and single-cell RNA-seq (scRNA-seq) data revealed that C5aR1+ TAMs exhibited immunosuppressive property which might contribute to CD8+ T cell dysfunction. Blockade of C5aR1 could diminish the immunosuppressive function of TAMs and led to reinvigorated CD8+ T cells mediated antitumor immunity. Moreover, using in vitro intervention experiment based on fresh GC surgical specimens, we discovered that C5aR1 blockade exert a synergistic effect when combined with PD-1 inhibitor for tumor clearance. Our study demonstrated that C5aR1 is a critical myeloid checkpoint and plays a crucial role in regulating the immunosuppressive property of TAMs and CD8+ T cell immune tolerance. C5aR1 blockade reprograms TAMs and reinvigorated the cytotoxicity of CD8+ T cells, thus improving the efficacy of anti-PD-1 therapy for tumor eradication in GC.

Somatic ARID1A mutation stratifies patients with gastric cancer to PD-1 blockade and adjuvant chemotherapy.

BACKGROUND: AT-rich interaction domain 1A (ARID1A) encodes a vital component of switch/sucrose non-fermentable chromatin-remodeling complex. Given its association with genomic instability, we conducted this study to determine whether ARID1A mutation status had an impact on therapeutic responsiveness in gastric cancer (GC), especially combinatory chemo-immunotherapy. METHODS: We retrospectively enrolled a total of 1162 patients from five independent cohorts. ZSHS Cohort and TCGA Cohort were designed to inform chemotherapeutic relevance and immunobiology of ARID1A-mutant GC based on tissue samples and sequencing data, respectively. MSKCC Cohort, mGC Cohort, and Melanoma Cohort were utilized to interrogate the predictive efficacy of ARID1A mutation to programmed cell death protein 1 (PD-1) blockade. RESULTS: ARID1A mutation was enriched in EBV-positive, hypermutated-single nucleotide variant and microsatellite-unstable subtype GC, and was predictive of responsiveness to both fluorouracil-based chemotherapy and PD-1 blockade. Specifically, ARID1A mutation score was a highly sensitive indicator (91%) of response to pembrolizumab. Mechanistically, ARID1A mutation correlated with extensive DNA damage repair deficiency and immunogenic tumor microenvironment (TME) featured by elevated activated subsets of CD8+ T cells, CD4+ T cells, and NK cells. Type 17T helper cells were typically abundant in ARID1A-mutant GC and might be a precondition for chemosensitivity conferred by ARID1A mutation. Furthermore, ARID1A mutation indicated elevated expression of VEGFA and CLDN18, as well as over-representation of ERBB2 and FGFR2 signaling pathway. CONCLUSIONS: ARID1A-mutant GC displayed immunogenic TME and might be a candidate for both monotherapy and the combination of frontline chemotherapy and PD-1 blockade.

Intratumoral PD-1+CD8+ T cells associate poor clinical outcomes and adjuvant chemotherapeutic benefit in gastric cancer.

BACKGROUND: Although PD-1 has been reported to be a marker of T-cell exhaustion in several malignancies, the biological role of PD-1+CD8+ T cells in gastric cancer (GC) remains unclear. Herein, we aimed to investigate the role of PD-1+CD8+ T cells in the tumour microenvironment and its clinical significance in GC. DESIGNS: This study included 441 tumour microarray specimens and 60 Flow cytometry specimens of GC patients from Zhongshan Hospital, and 250 GC patients from the Asian Cancer Research Group. RESULTS: Here, we demonstrated that PD-1+CD8+ T cells functioned as an independent adverse prognosticator in GC. In addition, an abundance of intratumoral PD-1+CD8+ T cells indicated worse chemotherapeutic responsiveness to fluorouracil in Stage III GC patients. Mechanistically, PD-1+CD8+ T cell high infiltration indicated an exhausted phenotype of global CD8+ T cells in GC tissues, which was characterised by elevated immune checkpoint expression including CTLA-4 and TIM-3, whereas decreased expression of perforin. Furthermore, PD-1+CD8+ T cell high-infiltration patients with Stage III GC held elevated activity of several therapeutic signal pathways. CONCLUSIONS: Our study highlighted that PD-1+CD8+ T cell abundance predicts inferior prognosis in GC, and may serve as a novel predictive biomarker to guide therapeutic option.

Intratumoral IL-1R1 expression delineates a distinctive molecular subset with therapeutic resistance in patients with gastric cancer.

BACKGROUND: With the essential role of interleukin-1 signaling in cancer-related inflammation, IL-1R1, the main receptor for both IL-1α and IL-1ß, demonstrated therapeutic potential in several types of cancer, which has been put into clinical trials. However, the expression profile and critical role of IL-1R1 in gastric cancer (GC) remain obscure. This study aimed to investigate the prognostic significance of IL-1R1 expression and its predictive value for chemotherapy and immunotherapy in GC. METHODS: The study enrolled three cohorts, consisting of 409 tumor microarray specimens of GC patients from Zhongshan Hospital, 341 transcriptional data from The Cancer Genome Atlas, and 45 transcriptional data from patients treated with pembrolizumab. IL-1R1 mRNA expression was directly acquired from public datasets, and we also detected IL-1R1 protein expression on tumor microarray by immunohistochemistry. Finally, the associations of IL-1R1 expression with clinical outcomes, immune contexture, and genomic features were analyzed. RESULTS: High IL-1R1 expression predicted poor prognosis and inferior responsiveness to both 5-fluorouracil-based adjuvant chemotherapy (ACT) and immune checkpoint blockade (ICB). IL-1R1 fostered an immunosuppressive microenvironment characterized by upregulated M2 macrophages and exhausted CD8+ T cells infiltration. Moreover, the expression of IL-1R1 was intrinsically linked to genomic alterations associated with targeted therapies in GC. CONCLUSIONS: IL-1R1 served as an independent prognosticator and predictive biomarker for ACT and ICB in GC. Furthermore, IL-1R1 antagonists could be a novel agent alone or combined with current therapeutic strategies in GC.