High levels of immune suppression are a common intrinsic mechanism of resistance in metastatic breast cancer that calls for developing immunotherapeutic combinations to broaden treatment responses. Histone deacetylase (HDAC) inhibitors can sensitize tumors to dual checkpoint inhibition in patients. Here, we investigated the tumor microenvironment (TME) of breast metastases by combining experimental and clinical data with theory to elucidate the mechanism of response to treatment with the HDAC inhibitor entinostat combined with anti-PD-1 and anti-CTLA-4. Knowledge-guided subclustering of single-cell RNA-sequencing (scRNA-seq) data and cell circuit analyses from murine breast-to-lung metastases identified 39 cell states and salient interactions, of which myeloid, T cell, and B cell subpopulations were most affected. Analyses of patient biopsies and blood via spatial proteomics and flow cytometry corroborated the preclinical findings, showing increased T cell and B cell activation, mature tertiary lymphoid structures, and increased CD8+ T cell-macrophage distances in responders to entinostat + nivolumab + ipilimumab. Combination treatment increased immunoglobulin production in patients and mice, and murine studies demonstrated increased tumor-targeting IgG and implicated B cells as necessary for treatment response. Inhibition of the ICAM1 and IFNγ pathways in myeloid cells partially recapitulated treatment effects on CD8+ T cells observed via scRNA-seq. Mathematical modeling of tumor-immune dynamics implicated simultaneous modulation of multiple TME interactions as required for response to the combination treatment. Overall, this study identifies lymphoid and myeloid cell contributions to response to treatment with HDAC inhibitors and immune checkpoint blockade, providing a framework for discovering interactions driving responses in complex TMEs.
E. Gonzalez, J. Kreger, Yingtong Liu et al.· Cancer Research· 0 citations
Background Pancreatic adenocarcinoma (PDAC) is an abysmal disease with poor clinical outcomes, largely due to limited life-extending treatments. Notably, PDAC displays a T cell-suppressive tumor microenvironment, and the underlying molecular mechanisms that lead to this phenotype remain poorly understood. Methods Utilizing the TCGA-PAAD dataset, tumor samples were separated by PLEC expression to evaluate patient survival, and pathway analyses associated with increased tumorigenesis. Evaluation of immune infiltration and subsequent immune deconvolution was performed using tidyestimate and CIBERSORTx R packages and immunohistochemistry (IHC) from human PDAC samples was performed to analyze PLEC expression and immune cell infiltration. Single-cell RNA-seq (scRNA-seq) analysis from 229 PDAC patients was analyzed to investigate signaling dynamics and immune cell infiltration in PLECHigh patients. Functional validation was provided using a monoclonal antibody (mAb) against cell surface plectin (CSP) in two murine PDAC models to examine changes in tumor growth and immune cell subset abundance. Results Our studies revealed that high plectin expression results in an overall worse survival associated with activation of pro-tumorigenic pathways and decreased anti-tumor immune signature in PDAC patients. Analysis via GSEA indicates PLECHigh patients display an aggressive phenotype and suppressed pro-inflammatory signaling pathways. Immune ESTIMATE scores were significantly decreased in PLECHigh patients, and IHC and scRNA-seq analysis revealed that PLECHigh tumors display a decrease in anti-tumor CD8+ T cells. In vivo analyses using an anti-CSP mAb revealed a reduction in tumor growth kinetics compared to IgG control corresponding with a significant increase in proliferating and activated cytotoxic CD8+ T cells. Anti-CSP-mediated tumor suppression was inhibited when CD8+ T cells were depleted, indicating that anti-CSP treatment is contingent on cytotoxic T cell functionality. Discussion Our findings identify plectin as a biomarker of aggressive disease in PDAC, with high plectin expression associated with decreased T cell infiltration, and anti-CSP treatment reinstates antitumor immunity and decreases tumor volume in vivo. These findings suggest that plectin is a novel therapeutic target with the potential to enhance immune responses in PDAC and improve patient outcomes.
Cody L. Wolf, Roxanne K. Ruiz, Sokchea Khou et al.· Frontiers in Immunology· 0 citations
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