Definitive experimental evidence from mouse cancer models and strong correlative clinical data gave rise to the Cancer Immunoediting concept that explains the dual host-protective and tumor-promoting ...actions of immunity on developing cancers. Tumor-specific neoantigens can serve as targets of spontaneously arising adaptive immunity to cancer and thereby determine the ultimate fate of developing tumors. Tumor-specific neoantigens can also function as optimal targets of cancer immunotherapy against established tumors. These antigens are derived from nonsynonymous mutations that occur during cellular transformation and, because they are foreign to the host genome, are not subject to central tolerance. In this review, we summarize the experimental evidence indicating that cancer neoantigens are the source of both spontaneously occurring and therapeutically induced immune responses against cancer. We also review the advances in genomics, bioinformatics, and cancer immunotherapy that have facilitated identification of neoantigens and have moved personalized cancer immunotherapies into clinical trials, with the promise of providing more specific, safer, more effective, and perhaps even more generalizable treatments to cancer patients than current immunotherapies.
Although current immune-checkpoint therapy (ICT) mainly targets lymphoid cells, it is associated with a broader remodeling of the tumor micro-environment. Here, using complementary forms of ...high-dimensional profiling, we define differences across all hematopoietic cells from syngeneic mouse tumors during unrestrained tumor growth or effective ICT. Unbiased assessment of gene expression of tumor-infiltrating cells by single-cell RNA sequencing (scRNAseq) and longitudinal assessment of cellular protein expression by mass cytometry (CyTOF) revealed significant remodeling of both the lymphoid and myeloid intratumoral compartments. Surprisingly, we observed multiple subpopulations of monocytes/macrophages, distinguishable by the markers CD206, CX3CR1, CD1d, and iNOS, that change over time during ICT in a manner partially dependent on IFNγ. Our data support the hypothesis that this macrophage polarization/activation results from effects on circulatory monocytes and early macrophages entering tumors, rather than on pre-polarized mature intratumoral macrophages.
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•High-dimensional analyses of successful ICT in tumor-bearing mice•ICT induces changes in intratumoral myeloid and lymphoid cells•Tumor-associated monocytes/macrophages display complex cytokine-driven phenotypes•Different cytokines act on tumor-infiltrating monocytes to drive macrophage polarization
Comprehensive changes in the tumor microenvironment during successful immune-checkpoint therapy are profiled, implicating a key role for polarization of infiltrating macrophages in the anti-tumor immune milieu.
The ability of the immune system to eliminate and shape the immunogenicity of tumours defines the process of cancer immunoediting
. Immunotherapies such as those that target immune checkpoint ...molecules can be used to augment immune-mediated elimination of tumours and have resulted in durable responses in patients with cancer that did not respond to previous treatments. However, only a subset of patients benefit from immunotherapy and more knowledge about what is required for successful treatment is needed
. Although the role of tumour neoantigen-specific CD8
T cells in tumour rejection is well established
, the roles of other subsets of T cells have received less attention. Here we show that spontaneous and immunotherapy-induced anti-tumour responses require the activity of both tumour-antigen-specific CD8
and CD4
T cells, even in tumours that do not express major histocompatibility complex (MHC) class II molecules. In addition, the expression of MHC class II-restricted antigens by tumour cells is required at the site of successful rejection, indicating that activation of CD4
T cells must also occur in the tumour microenvironment. These findings suggest that MHC class II-restricted neoantigens have a key function in the anti-tumour response that is nonoverlapping with that of MHC class I-restricted neoantigens and therefore needs to be considered when identifying patients who will most benefit from immunotherapy.
Conventional type 1 dendritic cells (cDC1)
are thought to perform antigen cross-presentation, which is required to prime CD8
T cells
, whereas cDC2 are specialized for priming CD4
T cells
. CD4
T ...cells are also considered to help CD8
T cell responses through a variety of mechanisms
, including a process whereby CD4
T cells 'license' cDC1 for CD8
T cell priming
. However, this model has not been directly tested in vivo or in the setting of help-dependent tumour rejection. Here we generated an Xcr1
mouse strain to evaluate the cellular interactions that mediate tumour rejection in a model requiring CD4
and CD8
T cells. As expected, tumour rejection required cDC1 and CD8
T cell priming required the expression of major histocompatibility class I molecules by cDC1. Unexpectedly, early priming of CD4
T cells against tumour-derived antigens also required cDC1, and this was not simply because they transport antigens to lymph nodes for processing by cDC2, as selective deletion of major histocompatibility class II molecules in cDC1 also prevented early CD4
T cell priming. Furthermore, deletion of either major histocompatibility class II or CD40 in cDC1 impaired tumour rejection, consistent with a role for cognate CD4
T cell interactions and CD40 signalling in cDC1 licensing. Finally, CD40 signalling in cDC1 was critical not only for CD8
T cell priming, but also for initial CD4
T cell activation. Thus, in the setting of tumour-derived antigens, cDC1 function as an autonomous platform capable of antigen processing and priming for both CD4
and CD8
T cells and of the direct orchestration of their cross-talk that is required for optimal anti-tumour immunity.
Significance
Immune checkpoint therapy (ICT) has led to durable responses in a subset of cancer patients. Generally, patients who respond to ICT bear tumors with high mutational burden. Radiation is ...used for treatment of many types of cancers and has been shown to induce new mutations in treated tumor cells and to synergistically facilitate ICT. However, these latter actions have largely been explained by radiation-induced tumor cell death and/or effects on the host. Herein, we show that noncurative irradiation induces mutations in tumor cells lacking neoantigens and that these de novo-generated neoantigens function as targets for CD8
+
T cells, resulting in increased immunogenicity of nonimmunogenic tumor cells. This study thus identifies an additional mechanism that explains synergy between immunotherapy and radiation.
Immunotherapies are a promising advance in cancer treatment. However, because only a subset of cancer patients benefits from these treatments it is important to find mechanisms that will broaden the responding patient population. Generally, tumors with high mutational burdens have the potential to express greater numbers of mutant neoantigens. As neoantigens can be targets of protective adaptive immunity, highly mutated tumors are more responsive to immunotherapy. Given that external beam radiation 1) is a standard-of-care cancer therapy, 2) induces expression of mutant proteins and potentially mutant neoantigens in treated cells, and 3) has been shown to synergize clinically with immune checkpoint therapy (ICT), we hypothesized that at least one mechanism of this synergy was the generation of de novo mutant neoantigen targets in irradiated cells. Herein, we use Kras
G12D
x p53
−/−
sarcoma cell lines (KP sarcomas) that we and others have shown to be nearly devoid of mutations, are poorly antigenic, are not controlled by ICT, and do not induce a protective antitumor memory response. However, following one in vitro dose of 4- or 9-Gy irradiation, KP sarcoma cells acquire mutational neoantigens and become sensitive to ICT in vivo in a T cell-dependent manner. We further demonstrate that some of the radiation-induced mutations generate cytotoxic CD8
+
T cell responses, are protective in a vaccine model, and are sufficient to make the parental KP sarcoma line susceptible to ICT. These results provide a proof of concept that induction of new antigenic targets in irradiated tumor cells represents an additional mechanism explaining the clinical findings of the synergy between radiation and immunotherapy.
The immune system influences the fate of developing cancers by not only functioning as a tumour promoter that facilitates cellular transformation, promotes tumour growth and sculpts tumour cell ...immunogenicity, but also as an extrinsic tumour suppressor that either destroys developing tumours or restrains their expansion. Yet, clinically apparent cancers still arise in immunocompetent individuals in part as a consequence of cancer-induced immunosuppression. In many individuals, immunosuppression is mediated by cytotoxic T-lymphocyte associated antigen-4 (CTLA-4) and programmed death-1 (PD-1), two immunomodulatory receptors expressed on T cells. Monoclonal-antibody-based therapies targeting CTLA-4 and/or PD-1 (checkpoint blockade) have yielded significant clinical benefits-including durable responses--to patients with different malignancies. However, little is known about the identity of the tumour antigens that function as the targets of T cells activated by checkpoint blockade immunotherapy and whether these antigens can be used to generate vaccines that are highly tumour-specific. Here we use genomics and bioinformatics approaches to identify tumour-specific mutant proteins as a major class of T-cell rejection antigens following anti-PD-1 and/or anti-CTLA-4 therapy of mice bearing progressively growing sarcomas, and we show that therapeutic synthetic long-peptide vaccines incorporating these mutant epitopes induce tumour rejection comparably to checkpoint blockade immunotherapy. Although mutant tumour-antigen-specific T cells are present in progressively growing tumours, they are reactivated following treatment with anti-PD-1 and/or anti-CTLA-4 and display some overlapping but mostly treatment-specific transcriptional profiles, rendering them capable of mediating tumour rejection. These results reveal that tumour-specific mutant antigens are not only important targets of checkpoint blockade therapy, but they can also be used to develop personalized cancer-specific vaccines and to probe the mechanistic underpinnings of different checkpoint blockade treatments.
Patients with SCLC rarely undergo biopsies at relapse. When pursued, tissue obtained can be inadequate for molecular testing, posing a challenge in identifying potentially targetable alterations in a ...clinically meaningful time frame. We examined the feasibility of circulating tumor DNA (ctDNA) testing in identifying potentially targetable alterations in SCLC.
ctDNA test results were prospectively collected from patients with SCLC between 2014 and 2017 and analyzed. ctDNA profiles of SCLC at diagnosis and relapse were also compared.
A total of 609 samples collected from 564 patients between 2014 and 2017 were analyzed. The median turnaround time for test results was 14 days. Among patients with data on treatment status, there were 61 samples from 59 patients and 219 samples from 206 patients collected at diagnosis and relapse, respectively. The number of mutations or amplifications detected per sample did not differ by treatment status. Potentially targetable alterations in DNA repair, MAPK and PI3K pathways, and genes such as MYC and ARID1A were identifiable through ctDNA testing. Furthermore, our results support that it may be possible to reconstruct the clonal relationship between detected variants through ctDNA testing.
Patients with relapsed SCLC rarely undergo biopsies for molecular testing and often require prompt treatment initiation. ctDNA testing is less invasive and capable of identifying alterations in relapsed disease in a clinically meaningful timeframe. ctDNA testing on an expanded gene panel has the potential to advance our knowledge of the mechanisms underlying treatment resistance in SCLC and aid in the development of novel treatment strategies.
Protein methyltransferases (PMTs) comprise a major class of epigenetic regulatory enzymes with therapeutic relevance. Here we present a collection of chemical probes and associated reagents and data ...to elucidate the function of human and murine PMTs in cellular studies. Our collection provides inhibitors and antagonists that together modulate most of the key regulatory methylation marks on histones H3 and H4, providing an important resource for modulating cellular epigenomes. We describe a comprehensive and comparative characterization of the probe collection with respect to their potency, selectivity, and mode of inhibition. We demonstrate the utility of this collection in CD4
T cell differentiation assays revealing the potential of individual probes to alter multiple T cell subpopulations which may have implications for T cell-mediated processes such as inflammation and immuno-oncology. In particular, we demonstrate a role for DOT1L in limiting Th1 cell differentiation and maintaining lineage integrity. This chemical probe collection and associated data form a resource for the study of methylation-mediated signaling in epigenetics, inflammation and beyond.
•The options for patients with previously treated NSCLC are limited.•Immune checkpoint inhibitors and anti-VEGF drugs are synergistic.•The combination of ramucirumab with atezolizumab was well ...tolerated.•Despite the low response rate, the overall survival was promising.
The treatment options for patients with stage IV non-small cell lung cancer (NSCLC) who develop tumor progression after platinum-based chemotherapy and immune checkpoint inhibitors (ICIs) are limited. The combination of ICI with inhibitors of vascular endothelial growth receptor (VEGFR) signaling has shown promising results in previously untreated patients.
In this single institution phase II study, patients with advanced stage NSCLC previously treated with at least one line including ICI received ramucirumab 10 mg/kg and atezolizumab 1,200 mg intravenously every 21 days until tumor progression or intolerable toxicity. The primary endpoint was overall response rate (ORR) by the RECIST 1.1 criteria according to the investigator assessment. Secondary endpoints included clinical benefit rate (CBR), overall survival (OS), progression-free survival (PFS) and tolerability.
Twenty-one patients were enrolled between June 2019 and April 2021. The median age was 67 (range 42–82), 17 (81 %) were female, and 15 (71 %) had non-squamous histology. The median number of prior systemic treatment lines and prior ICI lines were 3 (range 2–8) and 1 (range 1–3), respectively. One patient achieved a complete response for an ORR of 4.8 % while 16 (76.2 %) had stable disease with a CBR of 80.9 %. The median PFS was 3.4 months, and the median OS was 16.5 months. The most common adverse events included hypertension (86 %), proteinuria (67 %), and nausea (52 %). Grade 3 or 4 events were seen in 9 (43 %) of patients, with hypertension being the most common (33 %) of the grade 3 or 4 events.
Although the primary endpoint of ORR was not met, the combination of ramucirumab plus atezolizumab was associated with a high CBR and the OS was better than expected in heavily pretreated patients. Therefore, further investigation with ICI plus VEGF inhibition is warranted.
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