Neutrophils, long appreciated for their central role in host defences, have largely pro-tumorigenic effects in cancer owing to their sensitivity to signals in the tumour environment. Cancers regularly co-opt the functions of neutrophils to promote angiogenesis, immunosuppression, tumour growth and metastasis. However, depending on context, many of the same neutrophil-derived factors involved in these processes can mediate tumour cell killing. In this Review, we examine the functions of neutrophils and their impact on cancer, drawing parallels between their roles in cancer and non-cancer contexts, and highlighting their remarkable sensitivity to environmental cues. We call attention to promising strategies for targeting and manipulating neutrophils for the treatment of cancer. Neutrophils exhibit context-dependent pro-tumour and antitumour functions in cancer. In this Review, Diehl, Basto et al. examine neutrophil roles in tumour progression and metastasis, drawing parallels with non-cancer contexts and highlight emerging strategies to therapeutically target and reprogramme neutrophil biology in cancer.

Primary B-ALL-derived TR-APCs activate T cells in an MHC-restricted manner according to the inflammatory milieu

In vivo doxycycline administration results in significant TR-APC induction throughout tumors

Primary B-ALL TR-APCs can be generated via exogenous cytokine stimulation

TR-APC induction in solid tumor models attenuates tumor growth kinetics and prolongs survival

In vivo TR-APC induction results in expansion of activated and memory T cells, and decreased frequency of Tregs

Summary of clinical features of primary B-ALL specimens

In vivo TR-APC induction results in no observable off-target toxicity

In vivo TR-APC induction drives oligoclonal T cell expansion

In vitro re-exposure of T cells from surviving mice demonstrates TR-APC-mediated generation of tumor-specific memory.

TR-APC induction results in inflammatory rewiring of the tumor microenvironment.

Benchmarking antigen presentation by TR-APCs

Type 1 conventional dendritic cells (cDC1s) are unique in their efferocytosis1 and cross-presenting abilities2, resulting in antigen-specific T cell immunity3 or tolerance4-8. However, the mechanisms that underlie cDC1 tolerogenic function remain largely unknown. Here we show that the erythropoietin receptor (EPOR) acts as a critical switch that determines the tolerogenic function of cDC1s and the threshold of antigen-specific T cell responses. In total lymphoid irradiation-induced allograft tolerance9,10, cDC1s upregulate EPOR expression, and conditional knockout of EPOR in cDC1s diminishes antigen-specific induction and expansion of FOXP3+ regulatory T (Treg) cells, resulting in allograft rejection. Mechanistically, EPOR promotes efferocytosis-induced tolerogenic maturation7,11 of splenic cDC1s towards late-stage CCR7+ cDC1s characterized by increased expression of the integrin β8 gene12 (Itgb8), and conditional knockout of Itgb8 in cDC1s impairs tolerance induced by total lymphoid irradiation plus anti-thymocyte serum. Migratory cDC1s in peripheral lymph nodes preferentially express EPOR, and their FOXP3+ Treg cell-inducing capacity is enhanced by erythropoietin. Reciprocally, loss of EPOR enables immunogenic maturation of peripheral lymph node migratory and splenic CCR7+ cDC1s by upregulating genes involved in MHC class II- and class I-mediated antigen presentation, cross-presentation and costimulation. EPOR deficiency in cDC1s reduces tumour growth by enhancing anti-tumour T cell immunity, particularly increasing the generation of precursor exhausted tumour antigen-specific CD8+ T cells13 in tumour-draining lymph nodes and supporting their maintenance within tumours, while concurrently reducing intratumoural Treg cells. Targeting EPOR on cDC1s to induce or inhibit T cell immune tolerance could have potential for treating a variety of diseases.

The period between "successful" treatment of localized breast cancer and the onset of distant metastasis can last many years, representing an unexploited window to eradicate disseminated disease and prevent metastases. We find that the source of recurrence-disseminated tumor cells (DTCs) -evade endogenous immunity directed against tumor neoantigens. Although DTCs downregulate major histocompatibility complex I, this does not preclude recognition by conventional T cells. Instead, the scarcity of interactions between two relatively rare populations-DTCs and endogenous antigen-specific T cells-underlies DTC persistence. This scarcity is overcome by any one of three immunotherapies that increase the number of tumor-specific T cells: T cell-based vaccination, or adoptive transfer of T cell receptor or chimeric antigen receptor T cells. Each approach achieves robust DTC elimination, motivating discovery of MHC-restricted and -unrestricted DTC antigens that can be targeted with T cell-based immunotherapies to eliminate the reservoir of metastasis-initiating cells in patients.

Therapeutic cancer vaccination seeks to elicit activation of tumor-reactive T cells capable of recognizing tumor-associated antigens (TAA) and eradicating malignant cells. Here, we present a cancer vaccination approach utilizing myeloid-lineage reprogramming to directly convert cancer cells into tumor-reprogrammed antigen-presenting cells (TR-APC). Using syngeneic murine leukemia models, we demonstrate that TR-APCs acquire both myeloid phenotype and function, process and present endogenous TAAs, and potently stimulate TAA-specific CD4+ and CD8+ T cells. In vivo TR-APC induction elicits clonal expansion of cancer-specific T cells, establishes cancer-specific immune memory, and ultimately promotes leukemia eradication. We further show that both hematologic cancers and solid tumors, including sarcomas and carcinomas, are amenable to myeloid-lineage reprogramming into TR-APCs. Finally, we demonstrate the clinical applicability of this approach by generating TR-APCs from primary clinical specimens and stimulating autologous patient-derived T cells. Thus, TR-APCs represent a cancer vaccination therapeutic strategy with broad implications for clinical immuno-oncology. SIGNIFICANCE:Despite recent advances, the clinical benefit provided by cancer vaccination remains limited. We present a cancer vaccination approach leveraging myeloid-lineage reprogramming of cancer cells into APCs, which subsequently activate anticancer immunity through presentation of self-derived cancer antigens. Both hematologic and solid malignancies derive significant therapeutic benefit from reprogramming-based immunotherapy. This article is highlighted in the In This Issue feature, p. 1027.

Tumor-infiltrating dendritic cells promote, in a contact-dependant manner, secretion of lytic granules by CD8+ T cells.

Despite their cytotoxic capacity, neutrophils are often co-opted by cancers to promote immunosuppression, tumor growth, and metastasis. Consequently, these cells have received little attention as potential cancer immunotherapeutic agents. Here, we demonstrate in mouse models that neutrophils can be harnessed to induce eradication of tumors and reduce metastatic seeding through the combined actions of tumor necrosis factor, CD40 agonist, and tumor-binding antibody. The same combination activates human neutrophils in vitro, enabling their lysis of human tumor cells. Mechanistically, this therapy induces rapid mobilization and tumor infiltration of neutrophils along with complement activation in tumors. Complement component C5a activates neutrophils to produce leukotriene B4, which stimulates reactive oxygen species production via xanthine oxidase, resulting in oxidative damage and T cell-independent clearance of multiple tumor types. These data establish neutrophils as potent anti-tumor immune mediators and define an inflammatory pathway that can be harnessed to drive neutrophil-mediated eradication of cancer.

Abstract Therapeutic cancer vaccination seeks to elicit activation of tumor-reactive T cells capable of recognizing tumor-associated antigens (TAA) and eradicating malignant cells. Here, we present a cancer vaccination approach utilizing myeloid-lineage reprogramming to directly convert cancer cells into tumor-reprogrammed antigen-presenting cells (TR-APC). Using syngeneic murine leukemia models, we demonstrate that TR-APCs acquire both myeloid phenotype and function, process and present endogenous TAAs, and potently stimulate TAA-specific CD4+ and CD8+ T cells. In vivo TR-APC induction elicits clonal expansion of cancer-specific T cells, establishes cancer-specific immune memory, and ultimately promotes leukemia eradication. We further show that both hematologic cancers and solid tumors, including sarcomas and carcinomas, are amenable to myeloid-lineage reprogramming into TR-APCs. Finally, we demonstrate the clinical applicability of this approach by generating TR-APCs from primary clinical specimens and stimulating autologous patient-derived T cells. Thus, TR-APCs represent a cancer vaccination therapeutic strategy with broad implications for clinical immuno-oncology. Significance: Despite recent advances, the clinical benefit provided by cancer vaccination remains limited. We present a cancer vaccination approach leveraging myeloid-lineage reprogramming of cancer cells into APCs, which subsequently activate anticancer immunity through presentation of self-derived cancer antigens. Both hematologic and solid malignancies derive significant therapeutic benefit from reprogramming-based immunotherapy.

Proteins associated with myeloid dendritic cells positively correlate with improved survival of melanoma patients

Cell numbers of multiple immune cell substes, and mainly dendritic cells, are decreased over time in melanoma tumors.