ABSTRACT Background Immunotherapy has significantly improved outcomes for cancer patients; however, its clinical benefits vary among patients and its effectiveness across breast cancer subtypes remains uncertain. To enhance its efficacy, it is important to gain more insight into tumor-intrinsic immunomodulatory factors that could be used as therapeutic targets. We previously identified Lactate Dehydrogenase C (LDHC) to be a promising anti-cancer target due to its role in regulating cancer cell genomic integrity. In this study, we investigated the effects of tumor LDHC expression on immune responses. Methods TIMER AND TIDE deconvolution methods were used to investigate the relationship between tumor LDHC expression, immune cell infiltration and T cell dysfunction. Multiplex cytokine assays and flow cytometry analyses of breast cancer cell monocultures, and direct and indirect cancer cell-immune cell co-culture models were performed to assess the effect of LDHC knockdown on the secretion of inflammatory mediators and the expression of immune checkpoint molecules. T cell activity was determined by IFN-γ ELISPot assays and 7-AAD viability flow cytometry of cancer cells in direct co-culture. Results TIMER and TIDE analyses revealed that tumor LDHC expression is associated with T cell dysfunction in breast cancer and worse post-immunotherapy survival in melanoma. Depletion of LDHC in three breast cancer cell lines (MDA-MB-468, BT-549, HCC-1954) enhanced T cell activation and cytolytic function (4-hour direct co-culture). Analysis of cancer cell monocultures revealed an increase in secreted pro-inflammatory cytokines (IFN-γ, GM- CSF, MCP-1, CXCL1), a decrease in immunosuppressive factors (IL-6, Gal-9) and a reduction in tumor cell surface PD-L1 expression following LDHC knockdown. Using 72-hour direct co- cultures with LDHC-silenced cancer cells, we observed a decrease in tumor-promoting cytokines (IL-1β, IL-4 and IL-6) and an increase in the tumor-inhibiting cytokine CXCL1. Furthermore, LDHC knockdown reduced the number of CD8+ T cells expressing PD-1 and CTLA-4, as well as the cell surface expression of CTLA-4, TIGIT, TIM3, and VISTA. Conclusions Our findings suggest that targeting LDHC may improve anti-tumor immune responses by modulating the secretion of pro- and anti-tumorigenic cytokines and impairing immune checkpoint signaling. Further studies are needed to elucidate the molecular mechanisms by which LDHC modulates these responses in breast cancer.

Limited activation and infiltration of CD8+ T cells are major challenges facing T cell-based immunotherapy for most solid tumors, of which the mechanism is multilayered and not yet fully understood.
Levels of CD93 expression on monocytes from paired non-tumor, peritumor and tumor tissues of human hepatocellular carcinoma (HCC) were evaluated. The underlying mechanisms mediating effects of CD93+ monocytes on the inhibition and tumor exclusion of CD8+ T cells were studied through both in vitro and in vivo experiments.
In this study, we found that monocytes in the peritumoral tissues of HCC significantly increased levels of CD93 expression, and these CD93+ monocytes collocated with CD8+ T cells, whose density was much higher in peritumor than intratumor areas. In vitro experiments showed that glycolytic switch mediated tumor-induced CD93 upregulation in monocytes via the Erk signaling pathway. CD93 on the one hand could enhance PD-L1 expression through the AKT-GSK3β axis, while on the other hand inducing monocytes to produce versican, a type of matrix component which interacted with hyaluronan and collagens to inhibit CD8+ T cell migration. Consistently, levels of CD93+ monocytes positively correlated with the density of peritumoral CD8+ T cells while negatively correlated with that of intratumoral CD8+ T cells. Targeting CD93 on monocytes not only increased the infiltration and activation of CD8+ T cells but also enhanced tumor sensitivity to anti-PD-1 treatment in mice in vivo.
This study identified an important mechanism contributing to the activation and limited infiltration of CD8+ T cells in solid tumors, and CD93+ monocytes might represent a plausible immunotherapeutic target for the treatment of HCC.
© Author(s) (or their employer(s)) 2024. Re-use permitted under CC BY-NC. No commercial re-use. See rights and permissions. Published by BMJ.

Human bone marrow-derived mesenchymal stromal cells (BM-MSCs) have been proposed as a treatment for graft-versus-host disease (GVHD), which is a major complication following allogeneic hematopoietic cell transplantation. However, clinical trials have not yielded good results, and human decidua-derived mesenchymal stromal cells (DSCs) have been proposed as an alternative. In addition, the mechanism by which DSCs exert their immunomodulatory effects is still unknown. We found that knockdown of IL-6 in DSCs reduced the expression of PD-L1 and PD-L2, which are known as classical immune checkpoint inhibitors. Expression of PD-L1 and PD-L2 was restored by adding recombinant IL-6 to the DSCs. When DSCs and IL-6-knockdown DSCs were administered as treatment in a murine GVHD model, the group receiving IL-6-knockdown DSCs had significantly higher mortality and clinical scores compared to the group receiving DSCs. Taken together, these data suggest that the IL-6 signaling pathway is a crucial contributor to the immunosuppressive capacity of DSCs.
© 2024 The Authors.

The human dendritic cell (DC) family has recently been expanded by CD1c+CD14+CD163+ DCs, introduced as DC3s. DC3s are found in tumors and peripheral blood of cancer patients. Here, we report elevated frequencies of CD14+ cDC2s, which restore to normal frequencies after tumor resection, in non-small cell lung cancer patients. These CD14+ cDC2s phenotypically resemble DC3s and exhibit increased PD-L1, MERTK, IL-10, and IDO expression, consistent with inferior T cell activation ability compared with CD14- cDC2s. In melanoma patients undergoing CD1c+ DC vaccinations, increased CD1c+CD14+ DC frequencies correlate with reduced survival. We demonstrate conversion of CD5+/-CD1c+CD14- cDC2s to CD14+ cDC2s by tumor-associated factors, whereas monocytes failed to express CD1c under similar conditions. Targeted proteomics identified IL-6 and M-CSF as dominant drivers, and we show that IL-6R and CSF1R inhibition prevents tumor-induced CD14+ cDC2s. Together, this indicates cDC2s as direct pre-cursors of DC3-like CD1c+CD14+ DCs and provides insights into the importance and modulation of CD14+ DC3s in anti-tumor immune responses.
Copyright © 2024 The Authors. Published by Elsevier Inc. All rights reserved.

Neutrophils are innate immune cells that display multiple immunomodulatory properties. Using a mouse model of retroviral infection, we previously uncovered their key immunomodulatory function in promoting protective immunity during antiviral antibody therapy, which occurs through Fc-FcγR interactions. Here, we investigated the immunomodulatory properties of neutrophils in the context of HIV-1 infection and therapy. We conducted a thorough examination of the functional activation and modulation of Fcγ receptors (FcγRs) expression on neutrophils isolated from healthy donors (HD) and people living with HIV-1 (PLWH). Upon stimulation with virions, either free or in the form of immune complexes (ICs) formed with broadly neutralizing antibodies (bNAbs), neutrophils from HD secreted cytokines and chemokines in modest quantities. Interestingly, priming HD neutrophils with pro-inflammatory cytokines augmented their chemokine production upon exposure to HIV-1 and ICs, underscoring the pivotal role of the inflammatory milieu in eliciting a functional response from neutrophils to these stimuli. Noteworthy, under inflammatory conditions, IC-activated neutrophils showed higher secretion of CXCL1 and CCL4 than HIV-1-stimulated neutrophils. Highlighting the critical influence of the inflammatory environment on their functional properties, neutrophils from PLWH displayed increased release of cytokines (IFNγ) and chemokines (CXCL1, CCL2, CCL3 and CCL4) when stimulated with danger signals associated with HIV-1 infection. In addition, PLWH’s neutrophils exhibited higher expression of two activating FcgRs (FcgRI and FcgRIII) than neutrophils from HD. Our study provides new insights into the immunomodulatory properties of neutrophils during HIV-1 infection and therapy. These findings hold potential for optimizing antiviral antibody therapies by harnessing the immunomodulatory properties of neutrophils.