Rapid recruitment and IFN-I-mediated activation of monocytes dictate focal radiotherapy efficacy

CD301b+ monocyte-derived dendritic cells mediate resistance to radiotherapy

Monocytes infiltrating tumors acquire various states that distinctly impact cancer treatment. Here, we show that resistance of tumors to radiotherapy (RT) is controlled by the accumulation of monocyte-derived dendritic cells (moDCs). These moDCs are characterized by the expression of CD301b and have a superior capacity to generate regulatory T cells (Tregs). Accordingly, moDC depletion limits Treg generation and improves the therapeutic outcome of RT. Mechanistically, we demonstrate that granulocyte-macrophage colony-stimulating factor (GM-CSF) derived from radioresistant tumor cells following RT is necessary for the accumulation of moDCs. Our results unravel the immunosuppressive function of moDCs and identify GM-CSF as an immunotherapeutic target during RT.

Distinct immune responses to proton and photon radiotherapy: implications for anti-PD-L1 combination therapy in colorectal cancer

BACKGROUND

Ionizing radiation can influence the antitumor immune response, either activating or suppressing the immune system depending on the tumor type and radiotherapy modality. While photon radiation (RT) combined with immunotherapy (IT) is widely studied in clinical trials, proton radiation (PT) combined with IT has not been thoroughly investigated in clinical or preclinical studies despite its radiobiological advantages. This study aims to explore the immune effects of a hypofractionated PT scheme compared to RT and its efficacy with anti-PD-L1 immunotherapy.

METHODS

Balb/c mice bearing subcutaneous CT26 colon tumors were treated with RT or PT, delivered with 3 × 8 Gy. Seven days post-treatment, transcriptomic analysis and immune response assessments to characterize lymphoid cells, myeloid cells, and PD-L1 expression were performed. Tumor growth was monitored to evaluate the efficacy of combining RT or PT with anti-PD-L1 IT.

RESULTS

The RNA sequencing analysis demonstrated an overexpression of genes involved in the interferon type I pathway after both RT and PT. Tumor microenvironment analysis showed enhanced immune cell infiltration in tumors after both treatments. Immunoactivating cells infiltration was observed, with LT CD8 + cells infiltration after both RT and PT, more significantly after RT. NK and TAM1 cells infiltrated only after RT. Immunosuppressive cell populations were induced by PT, including MDSCs, while Tregs infiltrated both RT and PT treated tumors. PD-L1 expression was significantly induced only by RT. The combination of anti-PD-L1 with RT or PT resulted in tumor growth delay compared to RT or PT alone, with a significant survival benefit observed only after the combination of RT and IT.

CONCLUSIONS

This study demonstrates that hypofractionated RT and PT induced both similar and significantly distinct immune responses. PT triggers a stronger immunosuppressive response than RT. Optimizing the combination of PT with IT, including dose, fractionation, and sequencing is crucial for improving treatment efficacy.

Monocyte-lineage tumor infiltration predicts immunoradiotherapy response in advanced pretreated soft-tissue sarcoma: phase 2 trial results

Immunoradiotherapy holds promise for improving outcomes in patients with advanced solid tumors, including in soft-tissue sarcoma (STS). However, the ideal combination of treatment modalities remains to be determined, and reliable biomarkers to predict which patients will benefit are lacking. Here, we report the results of the STS cohort of the SABR-PDL1 phase II trial that evaluated the anti-PDL1 atezolizumab combined with stereotactic body radiation therapy (SBRT) delivered concurrently with the 2nd cycle to at least one tumor site. Eligible patients received atezolizumab until progression or unmanageable toxicity, with SBRT at 45 Gy in 3 fractions). The primary endpoint was one-year progression-free survival (PFS) rate with success defined as 13 patients achieving 1-year PFS. Sixty-one heavily pretreated patients with STS (median 5 prior lines; 52% men; median age 54 years; 28% leiomyosarcoma) were enrolled across two centers (France, Spain). SBRT was delivered to 55 patients (90%), with the lung being the most commonly irradiated site (50%). After a median follow-up of 45 months, the one-year PFS rate was 8.3% [95% CI: 3.6-18.1]. Median PFS and overall survival were 2.5 and 8.6 months, respectively. Best responses included partial responses (5%) and stable disease (60%). Immune profiling revealed increased immunosuppressive tumor-associated macrophages (e.g., IL4I1, HES1) and monocyte-recruiting chemokines in non-responders. Higher monocyte/lymphocyte ratios (MonoLR) in tumor and blood correlated with progression. PD-L1 status, lymphoid infiltration, and tertiary-lymphoid structures were not predictive. Although the primary endpoint was not met, this study highlights MonoLR imbalance as a potential biomarker to identify STS patients likely to benefit from immunoradiotherapy. EudraCT No. 2015-005464-42; Clinicaltrial.gov number: NCT02992912.

Low-dose irradiation of the gut improves the efficacy of PD-L1 blockade in metastatic cancer patients

The mechanisms governing the abscopal effects of local radiotherapy in cancer patients remain an open conundrum. Here, we show that off-target intestinal low-dose irradiation (ILDR) increases the clinical benefits of immune checkpoint inhibitors or chemotherapy in eight retrospective cohorts of cancer patients and in tumor-bearing mice. The abscopal effects of ILDR depend on dosimetry (≥1 and ≤3 Gy) and on the metabolic and immune host-microbiota interaction at baseline allowing CD8+ T cell activation without exhaustion. Various strains of Christensenella minuta selectively boost the anti-cancer efficacy of ILDR and PD-L1 blockade, allowing emigration of intestinal PD-L1-expressing dendritic cells to tumor-draining lymph nodes. An interventional phase 2 study provides the proof-of-concept that ILDR can circumvent resistance to first- or second-line immunotherapy in cancer patients. Prospective clinical trials are warranted to define optimal dosimetry and indications for ILDR to maximize its therapeutic potential.

A first evaluation of the efficacy of minibeam radiation therapy combined with an immune check point inhibitor in a model of glioma-bearing rats

Glioblastoma multiforme (GBM) continues to be a hopeless case today. Its treatment involves the use of multiple modalities. One of them is radiation therapy (RT), that is limited by normal tissue tolerances in GBM patients. GBM is widely recognized to induce local and systemic immunosuppression, which is a hindrance to the use of immune-modulating therapies. One possible strategy is to ally immunotherapy (IT) with novel RT approaches able to revert the immunosuppressive nature of GBM. One example is minibeam radiation therapy (MBRT). Preclinical experiments have shown that MBRT leads to a remarkable widening of the therapeutic window for GBM and elicits an effective immune priming. The main hypothesis of this study is that the activation of the immune system by MBRT would synergize with IT enhancing tumour control and minimizing toxicities. To validate it, in vivo experiments in a glioma rat model were performed. The goal was to assess the gain in survival of animals treated with MBRT, MBRT plus an immune check point inhibitor (ICI) versus conventional RT (CRT) or ICI alone. All treatments (ICI alone, CRT, CRT + ICI, MBRT and MBRT + ICI) increased survival with respect to the non-irradiated controls. However, the high radiation dose (30 Gy) delivered in one fraction in CRT is highly detrimental for normal tissues contrary to MBRT. The combination of CRT plus ICI appeared to be toxic. MBRT + ICI surpassed the survival rate with respect to ICI alone. When ICI was used with high-dose conventional irradiation, tumor eradication was observed in 6 out 8 animals. However, the survival was statistically equivalent to MBRT plus ICI, with a tendency to reduce survival in comparison with CRT alone, suggesting acute toxicity associated with this multimodal treatment. In conclusion, our results suggest some advantages for MBRT in combination with ICI. We need to conduct further work to determine the optimal RT-IT combination and schedule for ICI injection and MBRT irradiation.

Cancer cells impair monocyte-mediated T cell stimulation to evade immunity

The tumour microenvironment is programmed by cancer cells and substantially influences anti-tumour immune responses1,2. Within the tumour microenvironment, CD8+ T cells undergo full effector differentiation and acquire cytotoxic anti-tumour functions in specialized niches3-7. Although interactions with type 1 conventional dendritic cells have been implicated in this process3-5,8-10, the underlying cellular players and molecular mechanisms remain incompletely understood. Here we show that inflammatory monocytes can adopt a pivotal role in intratumoral T cell stimulation. These cells express Cxcl9, Cxcl10 and Il15, but in contrast to type 1 conventional dendritic cells, which cross-present antigens, inflammatory monocytes obtain and present peptide-major histocompatibility complex class I complexes from tumour cells through 'cross-dressing'. Hyperactivation of MAPK signalling in cancer cells hampers this process by coordinately blunting the production of type I interferon (IFN-I) cytokines and inducing the secretion of prostaglandin E2 (PGE2), which impairs the inflammatory monocyte state and intratumoral T cell stimulation. Enhancing IFN-I cytokine production and blocking PGE2 secretion restores this process and re-sensitizes tumours to T cell-mediated immunity. Together, our work uncovers a central role of inflammatory monocytes in intratumoral T cell stimulation, elucidates how oncogenic signalling disrupts T cell responses through counter-regulation of PGE2 and IFN-I, and proposes rational combination therapies to enhance immunotherapies.

Discovering mechanisms of macrophage tissue infiltration with Drosophila

Much is known about the importance of macrophages for regulating diverse aspects of organismal physiology, alongside their essential roles in inflammation. Relatively unexplored are the processes influencing macrophages' and monocytes' ability to invade into the tissues where they carry out these functions. Drosophila plasmatocytes, also called hemocytes, show similarities to vertebrate macrophages in their function and their molecular specification; they have recently been shown to also infiltrate into tissues during development and inflammation. Extravasation across vasculature, into tumors, the brain, and adipose tissue have all been observed. We discuss the striking parallels in some of these systems to vertebrate immune responses, including a requirement for tumor necrosis factor. Finally, we highlight the new pathways regulating infiltration found in the fly that remain as yet unexamined in a vertebrate context.

Tumor-targeted therapy with BRAF-inhibitor recruits activated dendritic cells to promote tumor immunity in melanoma

BACKGROUND

Tumor-targeted therapy causes impressive tumor regression, but the emergence of resistance limits long-term survival benefits in patients. Little information is available on the role of the myeloid cell network, especially dendritic cells (DC) during tumor-targeted therapy.

METHODS

Here, we investigated therapy-mediated immunological alterations in the tumor microenvironment (TME) and tumor-draining lymph nodes (LN) in the D4M.3A preclinical melanoma mouse model (harboring the V-Raf murine sarcoma viral oncogene homolog B (BRAF)V600E mutation) by using high-dimensional multicolor flow cytometry in combination with multiplex immunohistochemistry. This was complemented with RNA sequencing and cytokine quantification to characterize the immune status of the tumors. The importance of T cells during tumor-targeted therapy was investigated by depleting CD4+ or CD8+ T cells in tumor-bearing mice. Tumor antigen-specific T-cell responses were characterized by performing in vivo T-cell proliferation assays and the contribution of conventional type 1 DC (cDC1) to T-cell immunity during tumor-targeted therapy was assessed using Batf3-/- mice lacking cDC1.

RESULTS

Our findings reveal that BRAF-inhibitor therapy increased tumor immunogenicity, reflected by an upregulation of genes associated with immune activation. The T cell-inflamed TME contained higher numbers of activated cDC1 and cDC2 but also inflammatory CCR2-expressing monocytes. At the same time, tumor-targeted therapy enhanced the frequency of migratory, activated DC subsets in tumor-draining LN. Even more, we identified a cDC2 population expressing the Fc gamma receptor I (FcγRI)/CD64 in tumors and LN that displayed high levels of CD40 and CCR7 indicating involvement in T cell-mediated tumor immunity. The importance of cDC2 is underlined by just a partial loss of therapy response in a cDC1-deficient mouse model. Both CD4+ and CD8+ T cells were essential for therapy response as their respective depletion impaired therapy success. On resistance development, the tumors reverted to an immunologically inert state with a loss of DC and inflammatory monocytes together with the accumulation of regulatory T cells. Moreover, tumor antigen-specific CD8+ T cells were compromised in proliferation and interferon-γ-production.

CONCLUSION

Our results give novel insights into the remodeling of the myeloid landscape by tumor-targeted therapy. We demonstrate that the transient immunogenic tumor milieu contains more activated DC. This knowledge has important implications for the development of future combinatorial therapies.

Analysis of long non-coding RNAs associated with disulfidptosis for prognostic signature and immunotherapy response in uterine corpus endometrial carcinoma

Disulfidptosis, the demise of cells caused by the abnormal breakdown of disulfide bonds and actin in the cytoprotein backbone, has attracted attention in studies concerning disulfide-related cell death and its potential implications in cancer treatment. This study utilized bioinformatics to detect disulfidptosis associated lncRNA prognostic markers (DALPMs) with Uterine Corpus Endometrial Carcinoma (UCEC)-related to investigate the correlation between these indicators and the tumor immune microenvironment. The RNA sequencing data and somatic mutation information of patients with UCEC were obtained from the Cancer Genome Atlas (TCGA) database. Patients were randomly divided into Train and Test groups. The findings revealed a potential prognostic model comprising 14 DALPMs. Both univariate and multivariate Cox analyses demonstrated that the model-derived risk score functioned as a standalone prognostic indicator for patients. Significant disparities in survival outcomes were observed between the high- and low-risk groups as defined by the model. Differences in tumor mutational burden (TMB), tumor immune dysfunction and exclusion (TIDE), and tumor microenvironment (TME) stromal cells between patients of the high- and low-risk groups were also observed. The forecast model comprising long non-coding RNAs (lncRNAs) associated with disulfidptosis can effectively anticipate patients' prognoses.