Current mRNA approaches in immuno-oncology lack specificity for optimal T cell mRNA expression, necessitating tailored mRNA expression systems. In this study, we developed novel mRNA constructs in which the standard α-globin (HBA1) 5' UTR is replaced with sequences derived from genes highly expressed in effector T cells. Using primary human T cells, expression levels of UTR-modified reporter genes were evaluated, revealing significant variability based on the substituted UTR. For instance, interferon gamma (IFN-γ) UTRs facilitated enhanced and sustained protein expression, whereas TNF UTRs showed diminished expression. Unexpectedly, the in silico-predicted RNA stability of the various UTR-modified constructs did not correlate with the altered expression. These UTR-mediated differences in protein expression were unique to T cells, as HEK cells introduced with the same constructs showed distinct expression profiles. CD19-CAR constructs expressed in T cells using various 5' UTRs demonstrated different protein expression and function toward antigen-positive target cells, as well as tonic signaling, manifested by the immune output in the absence of antigen. Specifically, for CD19-CAR, using the TIGIT 5' UTR proved optimal for achieving maximal reactivity while minimizing tonic signaling. These findings provide proof of concept for the pivotal role of T cell-specific UTRs in optimizing CAR-T cell functionality by fine-tuning expression, reducing tonic signaling, and minimizing off-target effects, thus emphasizing their potential in advancing the therapeutic potential of mRNA-based CAR-T cell therapies.

Melanoma cells secrete melanosomes, large extracellular vesicles that reinforce tumor growth and survival signaling. To determine whether these vesicles elicit functional humoral immunity, we immunized mice with melanoma-derived melanosomes and analyzed the resulting antibody responses. This approach induced B cell expansion and generated antibodies directed against heat shock protein 70 (HSP70) present on the surface of melanosomes. Functionally, anti-HSP70 monoclonal antibodies inhibited growth in murine B16 and human MNT-1 melanoma cells independently of immune effector cells while suppressing key transcriptional programs involved in proliferation. In vivo, passive administration of anti-HSP70 antibodies delayed tumor onset and improved survival in a prophylactic B16 model. Moreover, in patients with metastatic melanoma treated with immune checkpoint blockade, higher serum anti-HSP70 immunoglobulin G (IgG) levels were associated with complete response compared with progressive disease. Together, these findings identify an extracellular vesicle-antibody axis that constrains melanoma survival signaling and has biomarker and therapeutic implications.

Melanoma cells actively secrete melanosomes-large, extracellular vesicles (EVs) enriched with oncogenic factors that reprogram the tumor microenvironment, enhance self-signaling, and promote tumor growth. Despite their abundance and immunogenic potential, humoral responses to melanoma-derived melanosomes remain unexplored. Here, we identify a novel immune surveillance mechanism in which melanosome-elicited decoy antibodies target melanoma-derived melanosomes by binding to the extracellular form of heat shock protein 70 (HSP70), a chaperone broadly implicated in cancer cell survival and stress adaptation. Anti-HSP70 decoy antibodies potently and effector-independently inhibit growth and survival of both murine and human melanoma cells and suppress key transcriptional programs involved in proliferation, cytoskeletal dynamics, and metabolism. In a preclinical B16 melanoma model, prophylactic administration of decoy monoclonal antibodies Mel322-34 and Mel321-35 conferred significant survival benefits of 27% and 48%, respectively. Strikingly, anti-HSP70 antibodies were enriched in the sera of melanoma patients achieving complete responses to immune checkpoint blockade, in contrast to non-responders with progressive disease. Collectively, our findings uncover a novel EV-antibody axis as a promising avenue to block cancer-promoting signaling pathways. Decoy autoantibodies targeting the extracellular form of HSP70 advance the understanding of tumor-intrinsic vulnerability and promote biomarker-driven immunotherapy in melanoma. ### Competing Interest Statement The authors have declared no competing interest. Israel Science Foundation, https://ror.org/04sazxf24, 3136/22, 638/23 United States-Israel Binational Science Foundation, https://ror.org/00j8z2m73, 01031771

e14593 Background: Tumor necrosis factor-alpha (TNF) has well-established anti-tumor effects including cytotoxicity against tumor vasculature. Past use of recombinant TNF to treat solid tumors resulted in unacceptable toxicities when given systemically but is successfully used in localized limb perfusion to treat melanoma and sarcomas. An alternative to promote endogenous TNF-mediated anticancer activity involves therapeutic apheresis to reduce the high concentrations of soluble TNF receptors (sTNF-Rs) produced by tumors, which sequester TNF and inhibit its tumoricidal effects. Methods: The LW-02 Column contains recombinant single-chain TNF, a capture ligand that selectively removes sTNF-Rs from plasma, covalently linked to a bead matrix. LW-02 Column Immunopheresis was evaluated in heavily pretreated patients with metastatic melanoma, renal cell carcinoma or triple negative breast cancer [NCT04142931]. LW-02 Column Immunopheresis was performed 3x/week, processing up to two plasma volumes for approximately 12 weeks as monotherapy (Cohort A, n = 6) or combined with nivolumab (Cohort B, n = 5). The study evaluated column performance, safety, clinical efficacy, and immunological biomarkers in the tumor microenvironment and blood. Results: The LW-02 Column effectively reduced sTNF-R plasma concentrations with capture efficiencies of 95.6% and 82.8% for sTNF-R1 and sTNF-R2, respectively, at the 30-minute procedural time point. At the data cut-off (Sept 30, 2022), median overall survival (OS) was 34.7 and 44.4 weeks for all patients (n = 11) and patients treated for ≥4 weeks (n = 8) (the latter group was prespecified in the protocol), respectively. For Cohorts A and B, median OS was 34.7 weeks and 45.4 weeks, respectively, for patients treated for ≥4 weeks. Evaluation of safety showed that only 2 adverse events (AEs) of 95 total AEs (including 7 SAEs) were deemed possibly related to LW-02 Column treatment. Immunohistochemical evaluation of tumor biopsies obtained 10-14 weeks after initiating LW-02 Column Immunopheresis revealed increased tumor-infiltrating lymphocytes (CD8+, HLA-DR+, and/or PD-1+ cells; 5/5 patients examined), and a reduced presence of tumor-associated macrophages (CD68+; 4/5 patients) compared to pretreatment biopsies. Preliminary immune profiling of peripheral blood mononuclear cells (5 patients) revealed increased expression levels of transmembrane TNF-R1 and TNF-R2, suggestive of increased cellular TNF responsiveness, and increased expression of activation molecules HLA-DR and CD86 after 4 weeks of LW-02 Column monotherapy compared to pretreatment levels. Conclusions: LW-02 Column Immunopheresis achieved safe and effective depletion of sTNF-Rs from plasma of patients with solid tumors. Further studies will assess the clinical benefit profile of the LW-02 Column for resensitizing tumors to respond to immunotherapy. Clinical trial information: NCT04142931 .

In vitro killing assay movies. Co-culture of 12T melanoma cells with irrelevant 108TILs

Our understanding of how the microbiota affects the balance between response to and failure of cancer treatment by modulating the tumour microenvironment and systemic immune system has advanced rapidly in recent years. Microbiota-targeting interventions in patients with cancer are an area of intensive investigation. Promisingly, phase I–II clinical trials have shown that interventions such as faecal microbiota transplantation can overcome resistance to immune checkpoint blockade in patients with melanoma, improve therapeutic outcomes in treatment-naive patients and reduce therapy-induced immunotoxicities. Here, we synthesize the evidence showing that the microbiota is an important determinant of both cancer treatment efficacy and treatment-induced acute and long-term toxicity, and we discuss the complex and inter-related mechanisms involved. We also assess the potential of microbiota-targeting interventions, including bacterial engineering and phage therapy, to optimize the response to and recovery from cancer therapy.

The remarkable capacity of immunotherapies to induce durable regression in some patients with metastatic cancer relies heavily on T cell recognition of tumor-presented antigens. As checkpoint-blockade therapy has limited efficacy, tumor antigens have the potential to be exploited for complementary treatments, many of which are already in clinical trials. The surge of interest in this topic has led to the expansion of the tumor antigen landscape with the emergence of new antigen categories. Nonetheless, how different antigens compare in their ability to elicit efficient and safe clinical responses remains largely unknown. Here, we review known cancer peptide antigens, their attributes and the relevant clinical data and discuss future directions.

Supplementary Tables 3, 6, 7, 9, 11, 12

Supplementary Tables 1, 2, 4, 5, 8, 10, 13, 14, 15

Traditional immunotherapies provide clinical benefits to only a few patients with solid tumors, highlighting the urgent need for more effective approaches. Traditional immunotherapies rely on the presentation of cancer antigens, with neoantigens being highly important in this context as they are specific to malignant tissue but not healthy tissue. The quantity of neoantigens is often associated with clinical benefit, but it cannot fully explain or predict patient response. In this Viewpoint, we highlight several qualitative aspects that should be considered in neoantigen‐based therapy. We emphasize the distinction between private and recurrent neoantigens, discuss the importance of neoantigen clonality, and describe new subtypes of neopeptides that further diversify the potential of neoantigens in immunotherapy.

Abstract For decades, cancer research and treatment focused on the cellular level, viewing cancer as a genetic disease of cell transformation. In the era of chemotherapy and radiotherapy, studies from the second half of the 19th century suggesting an association between the microbiota and cancer were almost neglected. The main focus of the field was limited to identification of specific viruses and bacteria that may serve as direct carcinogens leading to the recognition of 7 viruses (i.e., human papillomavirus, hepatitis B virus, and Kaposi sarcoma–associated herpesvirus) and 1 bacterium (Helicobacter pylori) as human carcinogens by the International Agency for Research on Cancer (https://monographs.iarc.who.int/agents-classified-by-the-iarc/). Shortly after the publication of the first draft of the human genome project in February 2001, the Nobel laureate microbiologist Joshua Lederberg raised the question: “Is human identity all in the genes?” It took more than a decade later and the development of multiomic techniques to confirm that his answer “each one of us is a small ecological community” was correct (Lederberg J. Keynote Address: Beyond the Genome. Brooklyn Law Rev 67). This ecological notion became relevant to cancer prevention, prediction, and treatment following the immunotherapy revolution and the understanding of the metabolic and immunologic roles of the microbiota in health and disease. Recently, the microbiota was recognized as an emerging hallmark of cancer following a large body of research showing its role in tumorigenesis, treatment efficacy and toxicity, and initial data regarding the role of microbial modulation in cancer therapy (Cancer Discov 2022;12(1):31–46). In the current review, we will focus on the role of fecal microbiota transplantation, the first microbial modulation technique that is used mainly in low-complexity conditions such as recurrent Clostridium difficile infections (Aliment Pharmacol Ther 2017;46(5):479–493), as a possible cancer therapeutic. However, to better understand the suggested roles of fecal microbiota transplantation in medical oncology, we first need to understand cancer as an ecological niche and the role of the microbiota in tumorigenesis and cancer treatment, specifically immunotherapy.

Abstract Over the last decade, it has become clear that the genomic landscapes of tumors profoundly impact their immunogenicity and how tumor cells interact with immune cells. Whereas past discoveries mainly focused on the interplay between tumor immunogenicity and tumor mutational burden (TMB), under the assumption that a higher mutation load would give rise to a better patient response to immune checkpoint blockade therapies, we and others have underlined intratumor heterogeneity (ITH) as an important determinant of the magnitude of the antitumor response and the nature of the tumor microenvironment. In this review, we define TMB versus ITH and how the two factors are being inferred from data, examine key findings in the cancer immunogenomics literature deciphering the complex cross-talk between TMB, ITH, and antitumor immunity in human cancers and in vivo models, and discuss the mutual influence of ITH and immunity—how the antitumor response can give rise to tumors with higher ITH, and how higher ITH can put shackles on the antitumor response.

Recent success in the use of immunotherapy for a broad range of cancers has propelled the field of cancer immunology to the forefront of cancer research. As more and more young investigators join the community of cancer immunologists, the Arthur L. Irving Family Foundation Cancer Immunology Symposium provided a platform to bring this expanding and vibrant community together and support the development of the future leaders in the field. This commentary outlines the lessons that emerged from the inaugural symposium highlighting the areas of scientific and career development that are essential for professional growth in the field of cancer immunology and beyond. Leading scientists and clinicians in the field provided their experience on the topics of scientific trajectory, career trajectory, publishing, fundraising, leadership, mentoring, and collaboration. Herein, we provide a conceptual and practical framework for career development to the broader scientific community.

Abstract Little is known regarding the relationship between intra-tumor heterogeneity (ITH) and immune response in melanoma. Here, we explored the role of ITH in tumor rejection by establishing a melanoma mouse model and inducing UVB-derived mutations that increase both ITH and mutational load. This induction gives rise to highly aggressive tumors and decreased cytotoxic activity of tumor infiltrating lymphocytes (TILs). Conversely, single cell-derived melanoma clones with reduced ITH are swiftly rejected. Tumor rejection is accompanied by increased TIL reactivity and increased infiltration into the tumor core. Using phylogenetic tree analyses and mixing experiments of 20 single cell clones that lie along the phylogenetic tee we show that tumor rejection is strongly affected by number of injected clones and genetic diversity. We have, thus set up a novel, highly controlled system that enables us to study the interphase between the immune system and different layers of intra-tumor heterogeneity. Finally, the analysis of melanoma patient data identifies parallel observations, supporting the importance of ITH in determining patient survival and response to checkpoint blockade. Citation Format: Osnat Bartok, Sushant Patkar, Sapir Cohen, Kevin Litchfield, Hiren Karathia, Joo Sang Lee, Alejandro Jiménez-Sánchez, Chi-Ping Day, Lea Eisenbach, Martin Miller, Glenn Merlino, Eli Pikarsky, Arie Admon, Charles Swanton, Eytan Ruppin, Yardena Samuels, Yochai Wolf. UVB-induced tumor heterogeneity directs immune response in melanoma [abstract]. In: Proceedings of the AACR Virtual Special Conference on Tumor Heterogeneity: From Single Cells to Clinical Impact; 2020 Sep 17-18. Philadelphia (PA): AACR; Cancer Res 2020;80(21 Suppl):Abstract nr IA07.

Chronic lymphocytic leukemia (CLL) is a malignancy of mature B lymphocytes. The microenvironment of the CLL cells is a vital element in the regulation of the survival of these malignant cells. CLL cell longevity is dependent on external signals, originating from cells in their microenvironment including secreted and surface-bound factors. Dendritic cells (DCs) play an important part in tumor microenvironment, but their role in the CLL bone marrow (BM) niche has not been studied. We show here that CLL cells induce accumulation of bone marrow dendritic cells (BMDCs). Depletion of this population attenuates disease expansion. Our results show that the support of the microenvironment is partly dependent on CD84, a cell surface molecule belonging to the Signaling Lymphocyte Activating Molecule (SLAM) family of immunoreceptors. Our results suggest a novel therapeutic strategy whereby eliminating BMDCs or blocking the CD84 expressed on these cells may reduce the tumor load.

Although clonal neo-antigen burden is associated with improved response to immune therapy, the functional basis for this remains unclear. Here we study this question in a novel controlled mouse melanoma model that enables us to explore the effects of intra-tumor heterogeneity (ITH) on tumor aggressiveness and immunity independent of tumor mutational burden. Induction of UVB-derived mutations yields highly aggressive tumors with decreased anti-tumor activity. However, single-cell-derived tumors with reduced ITH are swiftly rejected. Their rejection is accompanied by increased T cell reactivity and a less suppressive microenvironment. Using phylogenetic analyses and mixing experiments of single-cell clones, we dissect two characteristics of ITH: the number of clones forming the tumor and their clonal diversity. Our analysis of melanoma patient tumor data recapitulates our results in terms of overall survival and response to immune checkpoint therapy. These findings highlight the importance of clonal mutations in robust immune surveillance and the need to quantify patient ITH to determine the response to checkpoint blockade.

T cell immunoglobulin and mucin domain-containing protein 3 (TIM3), a member of the TIM family, was originally identified as a receptor expressed on interferon-γ-producing CD4 + and CD8 + T cells. Initial data indicated that TIM3 functioned as a ‘co-inhibitory’ or ‘checkpoint’ receptor, but due to the lack of a definable inhibitory signalling motif, it was also suggested that TIM3 might act as a co-stimulatory receptor. Recent studies have shown that TIM3 is part of a module that contains multiple co-inhibitory receptors (checkpoint receptors), which are co-expressed and co-regulated on dysfunctional or ‘exhausted’ T cells in chronic viral infections and cancer. Furthermore, co-blockade of TIM3 and programmed cell death 1 (PD1) can result in tumour regression in preclinical models and can improve anticancer T cell responses in patients with advanced cancers. Here, we highlight the developments in understanding TIM3 biology, including novel ligand identification and the discovery of loss-of-function mutations associated with human disease. In addition, we summarize emerging data from human clinical trials showing that TIM3 indeed acts as a ‘checkpoint’ receptor and that inhibition of TIM3 enhances the antitumour effect of PD1 blockade.