Cancer Immunology Research

BackgroundResistance to immune checkpoint inhibitors represents a major therapeutic challenge, as less than 50% of patients with melanoma achieve long-term response to immune checkpoint inhibitor therapy. One mechanism of acquired resistance involves somatic mutations, such as loss of beta-2 microglobulin (B2m), that enable tumor cells to evade T cell-mediated killing. MethodsThis study used single-cell RNA-seq, flow cytometry, and ex vivo functional assays to characterize tumor-infiltrating immune cells in antigen presentation-deficient tumors. Tumor-bearing mice were treated with anti-PD-1 or CD40 agonist antibodies and cell depletion or cytokine blocking antibodies to define mechanisms of action. Analysis of published human RNA-seq datasets was performed to dissect the contributions of inflammatory monocytes to patient outcomes. ResultsWe found an increase in immunosuppressive macrophages in B2m-null tumors. We hypothesized that repolarizing myeloid cells may restore control of tumor growth. Treatment with CD40 agonist antibody, which promotes differentiation of monocytes and macrophages towards a proinflammatory phenotype, reduced tumor growth and improved survival in B2m-null melanoma and colorectal cancer models. Unexpectedly, both CD8+ T cells and NK cells, but not CD4+ T cells, were required for the efficacy of CD40 agonist, even though CD8+ T cells cannot directly recognize antigen presentation-deficient tumor cells. Instead, these lymphocytes control tumor growth via secretion of IFN{gamma}, as depletion of IFN{gamma} inhibited the therapeutic effect of CD40 agonist. IFN{gamma} receptor (Ifngr1) expression was required on host cells, not tumor cells, for CD40 agonist-mediated tumor control. Single-cell analysis identified a distinct population of inflammatory monocytes that were enriched for an IFN{gamma} response signature in CD40 agonist-treated tumors, suggesting that these cells may be important for tumor control. Analysis of human bulk and single-cell RNA-seq datasets demonstrated that an inflammatory monocyte signature derived from our data was associated with improved patient outcomes and response to immune checkpoint inhibitors. ConclusionsThese data demonstrate that CD8+ T cells contribute to tumor control even in the absence of direct antigen presentation by tumor cells. More broadly, our work suggests that strategies to activate the effector functions of inflammatory monocytes may limit tumor growth and overcome acquired resistance to immune checkpoint inhibitors.

Despite the clinical success of immunotherapy, long-lasting benefit remains restricted to a subset of patients. Tumor metabolic adaptation is emerging as a key factor limiting immunotherapy efficacy. We previously found that glycolysis-low tumor variants, compared to the parental glycolytic tumors, better respond to neoadjuvant CTLA-4 immune checkpoint blockade (ICB) therapy. Here, we investigated new rational modalities to restore immune sensitivity of glycolytic tumors by studying how lowering the tumor-cell glycolytic capacity reshapes the tumor microenvironment (TME) to favor long-lasting systemic anti-tumor responses upon immunotherapy. We found that lowering glycolysis in cancer cells through LDHA-knock down (KD) results in TME displaying normalized vasculature, reduced angiogenic markers, increased high endothelial venules (HEVs), and enhanced recirculation of CD8+ T cells both in and out of the tumor. By leveraging public transcriptomic data sets from human solid cancers, we confirmed that glycolysis positively correlates with neo-angiogenesis and inversely correlates with features of vascular normalization and immune cytolytic activity. Moreover, a tumor signature that incorporates glycolysis- and angiogenesis-related genes as positive features, and normal vasculature, HEV, and immune cytolytic activity genes as negative features predicted poor outcomes better than the individual features across most human solid tumor types in the TCGA. To determine the therapeutic implication of these interrelated processes, we asked if targeting the vasculature would restore immunotherapy responses in glycolytic tumors. We found that combining low-dose anti-VEGFR2 with CTLA-4 blockade induces tumor regressions and protection from metastases in glycolytic tumors. These therapeutic effects were associated with vasculature normalization and increased abundance of HEVs and concentrations of lymphangiogenic factors in the TME of glycolytic tumors. Moreover, anti-VEGFR2 with anti-CTLA-4 restored recirculation of anti-tumor CD8+ T cells in and out of the TME in glycolytic tumors, with specific increases in intratumoral recruitment and activation of cytolytic CD62LCD44CD8 T cells expressing VEGFR2 and low levels of CTLA-4, suggesting potential novel direct synergistic effects of anti-VEGFR2 and anti-CTLA-4 on CD8+ T cells. Conversely, this combination opposed the beneficial immune and vascular TME features of LDHA-KD tumors, indicating tumor-metabolic-dependent effects. Accordingly, we found that standard combined regimens of anti-VEGF and ICB therapy improve survival with respect to ICB alone in patients with glycolysis-high but not glycolysis-low tumors. Together, these findings indicate that tumor cell glycolysis "primes" the TME for aberrant vascular architecture and T-cell exclusion, and that modulating the tumor vasculature can unravel these mechanisms restoring immune responsiveness. This suggests that tailoring anti-angiogenic and immunotherapy combinations to the tumor glycolytic state and associated vasculature profiles may restore immune surveillance and overcome therapy resistance.

Reactive neutrophil infiltration can restrain CD8+ T cell expansion in lymph nodes during adoptive T cell therapy (ACT), yet its spatiotemporal regulation remains incompletely understood. Levaraging flow cytometry and multiplex immunofluorescence data, we performed a time-resolved quantitative assessment of immune cell dynamics in tumor-draining lymph node (tdLN) and non-tumor-draining lymph node (non-tdLN) in a melanoma mouse model receiving ACT. Transferred tumor-reactive CD8+ T cells accumulated and expanded early after treatment initiation, showing the highest frequency of a favorable central memory CD8+ T cell phenotype in the tdLN. Enhancing innate immune signaling in melanomas increased neutrophil influx into lymph nodes, particularly the non-tdLN; however, within the tdLN, neutrophils were enriched in the T cell zone, which also contained the largest absolute reservoir of transferred CD8+ T cells. Together, these findings indicate that tdLN and non-tdLN differ in early neutrophil dynamics and compartmentalization during ACT, influenced by the strength of innate immune signaling in the tumor.

1IntroductionTumor infiltrating lymphocytes (TIL) drive the anti-tumor activity of a broad class of immunotherapies. In situ TIL are composed of T cells that recognize tumor antigens (Tumor Reactive T cells, or TRTs) as well as bystander T cells with specificity for other antigens. TRT clonotypes are associated with a unique and tumor-driven exhausted transcriptional state, enabling single-cell RNA sequencing (scRNA-seq)-based predictive models for TRTs using experimentally validated clone labels. MethodsIn this study, a clonotype-level CD8+ TRT classifier (TRACE) was built using an aggregated dataset of validated tumor reactive clonotypes and associated scRNA-seq data from multiple publications that overcomes the limitations of training on a single dataset, donor, or indication. TRACE does not require dataset manipulation for training or prediction, enabling it to be easily applied to new test datasets as they emerge. ResultsTRACE exhibited robust performance on held-out TIL and PBMC clones - achieving a mean Matthews correlation coefficient of 0.84 and F1-score of 0.85 - comparable to or outperforming other TRT prediction methods. We experimentally confirmed the reactivity of TRACE-identified TRT clones by co-culturing engineered, ex vivo expanded TIL with autologous melanoma tumor cell lines. Finally, we applied TRACE to evaluate the frequency of TRT across hundreds of patient samples from multiple tumor atlases spanning lung, colorectal, and pancreatic cancer. TRACE scores were observed to be significantly higher in exhausted CD8 T cells in tumors but not in exhausted cells in normal adjacent or non-cancer samples, suggesting specificity towards identifying tumor-antigen experienced T cells. ConclusionTRACE is a tumor reactivity scoring algorithm released with open model weights that can be applied to tissue or blood single-cell RNAseq datasets. Its application should be of general interest for characterizing the fraction of TRTs in TIL and for establishing correlations with clinical response to immunotherapies.

Type 1 conventional dendritic cells (cDC1s) are important for generating and sustaining antitumor immunity. Accordingly, the abundance of cDC1s in human tumors correlates with improved outcomes in cancer. Capitalizing on this role, we previously demonstrated that vaccination with in vitro-derived murine cDC1s elicits durable tumor control in multiple preclinical models; however, the immunological mechanisms underlying the efficacy of cDC1 vaccination remain unclear. Here, we examined whether in vitro-derived cDC1s resemble tumor-infiltrating DC populations and whether MHC-I and MHC-II antigen presentation contribute to cDC1-mediated tumor control following vaccination in melanoma. As expected, MHC-I- or MHC-II-deficiency had minimal impact on the transcriptional state of cDC1s in homeostasis or following stimulation with the adjuvant poly dI:dC. Moreover, in vitro-derived cDC1s cultured under steady-state conditions closely resembled tumor-infiltrating cDC1s, whereas their poly dI:dC-stimulated counterparts resembled CCR7+ tumor-infiltrating DC populations, also referred to as mregDCs or LAMP3+ DCs. Our data further show that both MHC-I and MHC-II contribute to tumor control upon cDC1 vaccination, and coexpression of MHC-I and MHC-II on the same cDC1 is necessary for a robust vaccine response. We also identified an important function for host cDC1s in supporting the efficacy of vaccination with in vitro-derived cDC1s, as judged by impaired tumor control in Irf8+32-/- mice, which lack endogenous cDC1s. Overall, these results indicate that effective antitumor responses depend on MHC-I and MHC-II antigen presentation by vaccine-delivered cDC1s, with additional contributions from host cDC1s. Key pointsO_LIIn vitro-generated cDC1s resemble intratumoral DC populations found in mice and humans. C_LIO_LIMHC-I and MHC-II antigen presentation by vaccine-delivered cDC1s contribute to antitumor efficacy. C_LIO_LICoexpression of MHC-I and MHC-II on the same cDC1 enhances vaccine responses. C_LIO_LIAntitumor responses reflect the activity of vaccine and endogenous cDC1s. C_LI

Immune mobilizing monoclonal TCR against cancer (ImmTAC) are cancer therapeutics that activate T cells through recognition of a tumor-associated antigenic MHC/peptide complex. A first-in-class ImmTAC, Tebentafusp, is approved for the treatment of metastatic uveal melanoma. While clinical efficacy is thus established, the cellular mechanisms underpinning ImmTAC action are not fully resolved. Using a recently established experimental strategy to generate suppressed human primary cytotoxic T lymphocytes (CTL), we have investigated an ImmTAC that recognizes a peptide derived from the tumor associated antigen NY-ESO-1 in comparison to direct engagement of a TCR recognizing the same MHC/peptide complex. In response to endogenous antigen presentation, ImmTACs could elicit tumor cell cytolysis by suppressed CTL, but not IFN{gamma} secretion, in a manner dependent on the engager affinity for CD3{varepsilon}. ImmTACs enhanced the efficient execution of subcellular CTL polarization steps required for effective cytolysis and could trigger calcium signaling. These data establish that ImmTACs activate CTL similarly to direct engagement of a TCR by MHC/peptide and are likely to retain this capability under suppressive conditions such as in the tumor microenvironment.

Cytotoxic T cells (CTL) are crucial for adaptive immunity that leads to prolonged survival and potential cures for cancer. Recent clinical data has shown that pharmacological inhibition of SUMOylation (SUMOi) profoundly modifies tumor microenvironment (TME) and activates CTL, although the mechanism is not well described. In this study, we found that T cell specific knock out (KO) of the most dominant SUMO paralog, Sumo2/SUMO2, in both mouse and human CD8+ T cells significantly enhanced CD8+ T cell activation that is independent of the known mechanism - inducing type I IFN (IFN-I) expression by myeloid cells. Sumo2/SUMO2 KO in CD8+ T cells increased chromatin accessibility for transcription factors BATF, JunB, ATF3, FRA1, FRA2, and AP1 that are known to promote T cell activation and proliferation. Using antigen-specific T cell models, OT1 and Chimeric Antigen Receptor (CAR)-T cells, we found that Sumo2 KO CD8+ T cells had significantly higher tumor infiltration as revealed by flow cytometry, immuno-fluorescence (IF) staining, and single nuclei RNA-sequencing (snRNA-seq) and conferred greater tumor growth inhibition than wildtype (WT) control T cells. snRNA-seq also revealed Sumo2 KO CD8+ T cells increased the expression of Tumor Necrosis Factor-Related Apoptosis-inducing Ligand (TRAIL), induced apoptosis genes in tumor cells and activated IFN-I and IFN-{gamma} responsive genes in all cell types in the TME. These findings elucidate a novel mechanism regarding how SUMOylation can directly control CTL activation and tumor infiltration that activate anti-tumor immunity in the TME. SUMO2 KO can also be a potential strategy to enhance adoptive T cell therapies of solid tumors by enhancing their activity, tumor infiltration and their ability to after the TME.

Abstract/SummaryImmune checkpoint blockade can produce long-lasting responses in patients with metastatic melanoma; notably, combined CTLA-4/PD-1 blockade has been associated with approximately 52% melanoma specific 10-year survival (1). Yet, nearly half of patients experience minimal clinical benefit, and intensified regimens come with substantial risk of severe immune-related toxicity. The precise determinants of immunotherapy response are incompletely defined, reflecting a complex interplay between tumor biology and host immunity. This is especially consequential for patients whose disease progresses on checkpoint blockade, for whom effective salvage options are limited. In a series of patients with NRAS-mutated melanoma refractory to checkpoint inhibitors, we found that intratumoral administration of talimogene laherparepvec (T-VEC) combined with MEK inhibitor binimetinib induced exceptional clinical responses by amplification of pre-existing T cell responses and induction of de novo tumor-reactive immunity.

Immune checkpoint blockade (ICB) has demonstrated clinical efficacy in several cancers, including melanoma, lung, colorectal, and liver malignancies. However, a substantial proportion of patients fail to respond, underscoring the need for alternative immunotherapeutic strategies capable of overcoming resistance to conventional checkpoint inhibition. One such strategy involves targeting intracellular inhibitory immune checkpoints that regulate effector lymphocyte function. Rasal1, a Ras GTPase-activating protein, has been shown to negatively regulate T cell-mediated antitumor immunity. In this study, we further characterized the impact of Rasal1 impairment on tumor progression, T cell stemness, and effector function. Using an endonuclease-mediated mutation targeting the C2 domain of Rasal1, we demonstrate that Rasal1-impaired (Rasal1i) mice exhibit significantly reduced tumor growth across multiple murine cancer models. Rasal1i mice displayed increased intratumoral CD8+ T cell accumulation, activation, cytolytic capacity, and enhanced Wnt signaling. Tumor-infiltrating lymphocytes additionally exhibited increased progenitor and stem-like memory phenotypes. Notably, Rasal1 inhibition prolonged survival and potentiated PD-1 therapy in a resistant PD-L1-expressing B16F10 melanoma model. Collectively, these findings identify Rasal1 as an intracellular inhibitory immune checkpoint that constrains T cell stemness and antitumor function, and support its further evaluation as a therapeutic target for cancer immunotherapy.

Downregulation of major histocompatibility complex class I (MHC-I) molecules is a frequent mechanism of tumor immune evasion, impairing recognition and elimination of cancer cells by cytotoxic CD8+ T lymphocytes. This phenotype, associated with poor prognosis and resistance to immune checkpoint blockade, is often driven by oncogenic pathways that reversibly suppress MHC-I. The MAPK ERK5 and its only upstream activating kinase MEK5 configure a unique intracellular signaling that regulates cell proliferation, differentiation and survival, and it has emerged as an oncogenic driver of different tumors. In this work, we investigated whether the ERK5 pathway contributes to cellular immunity. We used a panel of human cancer cell lines representing three well-established oncogenic contexts linked to reversible MHC-I downregulation (MYCN amplification, PTEN/PIK3CA mutations, and androgen receptor signaling), together with control cellular models exhibiting constitutively high MHC-I expression. We found that MEK5 or ERK5 pharmacologic inhibition or ERK5 targeted degradation increased MHC-I surface and total expression in low-MHC-I cells, without affecting PD-L1 levels. Conversely, ERK5 overexpression impaired MHC-I levels. Moreover, systemic administration of an ERK5 inhibitor also enhanced MHC-I expression in tumor xenografts. Mechanistically, RT-qPCR analysis showed that ERK5 or MEK5 inhibition did not significantly modify transcription of classical HLA-I genes or antigen-processing machinery components, and RNA-seq analysis did not render enrichment of MHC-I transcriptional programs in response to ERK5 inhibition. In contrast, trafficking experiments implicated the ERK5 pathway in the regulation of MHC-I lysosomal degradation, suggesting that ERK5 controls surface MHC-I through post-translational mechanisms. Notably, functional assays were carried out in co-cultures of cancer cells with tumor-specific human CD8+ T cells, where ERK5 inhibition sensitized MYCN-amplified or PTEN/PI3KCA-mutated cancer cells to CD8+ T cell-mediated apoptosis. These results identify ERK5 as a novel regulator of MHC-I expression in cancer cells, by regulating antigen presentation across diverse oncogenic contexts, and support a rationale for the use of ERK5 inhibitors as a strategy to improve the efficacy of immune checkpoint blockade-based immunotherapy.

The solid tumor microenvironment inhibits the functionality of tumor infiltrating T cells recognizing cognate tumor antigen, driving their differentiation towards terminal exhaustion. Interventions are sought to enhance the anti-tumor functionality of tumor-reactive T cells for clinical benefit. The functional genome regulating CD8+ T cell function against solid tumors was mapped by performing genome-wide, focused, and combination in vivo CRISPR/Cas9 screens using OT1 and PMEL TCR transgenic T cells in B16-OVA, MC38-gp100 and EG7-OVA syngeneic tumor models. The ability of the top single hits and combinations, which include Regnase-1 and SOCS1, to enhance CD8+ T cell anti-tumor function was evaluated in the OT1/B16-OVA model with large and established tumors, the disseminated PMEL/B16F10 tumor model, and in a novel murine TIL syngeneic model. The impact of Regnase-1 and SOCS1 single and dual-inactivation on the differentiation of exhausted CD8+ T cell subsets and on long-term persistent memory following tumor clearance was evaluated in OT1 CD8+ T cells in the B16-OVA model. The impact of single and dual-inactivation of Regnase-1 and SOCS1 on the anti-tumor function of experimental human T cell therapeutics was characterized in CRISPR/Cas9-engineered human TIL derived in vitro and in mesothelin-targeting CAR-Ts in vivo. NF-{kappa}B and cytokine signaling were identified as the top pathways regulating CD8+ T cell anti-tumor function, with Regnase-1 and Suppressor of Cytokine Signaling 1 (SOCS1) the top single and combination edits regulating the accumulation of tumor-specific TCR transgenic CD8+ T cells in syngeneic tumor models. Dual-inactivation of Regnase-1 and SOCS1 cooperated through non-redundant mechanisms to strongly expand intermediate (Texint) and effector (Texeff) exhausted CD8+ T cells within lymphoid tissues and tumor, with CD8+ T cells rewired to display an enhanced effector state and suppressed expression of TOX. Dual-edited persistent T effector memory cells (Tem) were formed following tumor clearance. Lastly, Regnase-1 and SOCS1 inactivation enhanced human Tumor Infiltrating Lymphocyte (TIL) and chimeric antigen receptor T cells (CAR-T) therapy functionality. Collectively, this study systematically mapped pathways regulating CD8+ T cell anti-tumor functionality, with Regnase-1 and SOCS1 dual-inactivation found to maximize anti-tumor function through non-redundant mechanisms.

BackgroundThe efficacy of immune checkpoint blockade relies on the robust priming of T cells by immunostimulatory dendritic cells (DCs). However, the tumor microenvironment (TME) frequently drives DCs into a dysfunctional, pro-tolerogenic state governed by aberrant metabolic rewiring, creating a barrier to durable antitumor immunity. While tumor-derived extracellular vesicles (EVs) are abundant in the TME, their specific role in orchestrating this immunosuppressive metabolic reprogramming remains poorly understood. This study provides insight into the signaling axes through which tumor-derived EVs alter DC function and evaluates the therapeutic potential of targeting these pathways to overcome immunotherapy resistance. MethodsTumor models were engineered to express EV fluorescent markers to track tumor EV uptake in vivo. Bulk and single-cell RNA sequencing was integrated with multi-parameter flow cytometry to characterize the reprogramming of tumor EV-educated DCs both in vitro and in vivo. Western blotting, quantitative real-time polymerase chain reaction assays, various cellular metabolic assays, as well as T cell-based immunologic studies were utilized to characterize the underlying mechanisms of tumor EV-mediated DC reprogramming. DC-specific Ppara-deficient mice were developed to verify these mechanisms in vivo. PPAR- targeted inhibitors were evaluated based on their ability to overcome checkpoint inhibitor resistance in an autochthonous model of melanoma. ResultsTumor-derived EVs were found to promote tumor progression by suppressing host immunity. Further studies reveal that tumor-derived EVs induce a tolerogenic mregDC transcriptional signature characterized by the upregulation of immunoregulatory molecules in DCs both in vitro and in vivo. These tumor EV-educated DCs exhibit an impaired capacity for CD8+ T cell priming, while demonstrating a proficiency for promoting CD4+FoxP3+ regulatory T cell differentiation. Mechanistically, tumor EVs concurrently trigger the unfolded protein response (UPR) via the PERK-ATF4 and IRE1-XBP1s signaling axes, subsequently activating the SREBP2 and PPAR- transcription factors, respectively. This process drives both aberrant lipid accumulation and fatty acid oxidation (FAO) in DCs residing within the TME. DC-restricted ablation of PPAR- significantly reversed the pro-tolerogenic effect of tumor EVs in vivo while pharmacologic targeting of PPAR- overcomes anti-PD-1 resistance and augments CD8+ T cell infiltration in an autochthonous model of melanoma. ConclusionsTumor EVs contribute to the development and pro-tolerogenic function of mregDCs in the TME by triggering the UPR pathway. Aberrant lipid metabolism involving enhanced FAO are common characteristics associated with DC dysfunction in the TME. Strategies to interrupt these pathways represent promising approaches for reversing immune tolerance and enhancing tumor-targeted CD8+ T cell responses.

The phase 1b TICIMEL clinical trial evaluated the safety, tolerability, and anti-tumor activity of combining the immune checkpoint inhibitors (ICI), ipilimumab and nivolumab, with tumor necrosis factor (TNF) blockers, certolizumab or infliximab, to treat advanced melanoma patients. A higher proportion of responses was observed in patients receiving ICI and certolizumab, while patients treated with ICI and infliximab demonstrated superior tolerability. Moreover, CITE-Seq analyses of circulating CD8 T cells showed that ICI plus certolizumab promoted an IFN signature, whereas ICI plus infliximab reduced the induction of genes associated with T cell activation. In preclinical models, ICI and TNF blockade with certolizumab increased IFN-{gamma}+ CD8 T cells and reduced regulatory T cells in tumors. The IgG1 Fc fragment of infliximab was identified as counteracting the benefits of TNF blockade. These findings underscore the importance of selecting the optimal TNF blocker to combine with ICI to enhance therapy efficacy in melanoma patients. ClinicalTrials.gov identifiers: NCT03293784; NCT05867004.

BackgroundCross-presentation of tumor antigens by antigen-presenting cells (APCs) is essential for initiating effective anti-tumor T cell immunity. The presence of cross-presenting immune cells across multiple solid tumors correlates with improved clinical outcomes. Despite the importance of this process, the identities and characteristics of tumor-derived MHC-I antigens that are cross-presented by APCs remain largely undefined, limiting rational design of targeted immunotherapies. MethodsWe performed an immunopeptidomic analysis of cross-presented glioblastoma (GBM) antigens on APCs, including bone marrow-derived macrophages, bone marrow-derived dendritic cells, and splenic dendritic cells, using SILAC labeling and in vitro co-culture systems. Additionally, we also profiled endogenous APC and tumor antigen repertoires. We made selected cross-presented antigen targets into mRNA vaccines and evaluated their immunogenicity in comparison to tumor endogenous antigens in vivo. ResultsWe identified over one thousand putative cross-presented GBM antigens. Comparative analysis of endogenous APC and tumor antigen repertoires revealed that cross-presented antigens possess distinct features and are predominantly shaped by intrinsic antigen processing and presentation pathways within APCs, resulting in limited cross-presentation of tumor-specific epitopes. Two doses of mRNA encoding cross-presented tumor-specific epitopes delayed tumor growth and elicited robust antigen-specific T cell responses. ConclusionOur findings define the landscape and constraints of tumor antigen cross-presentation in GBM and establish a framework for improved antigen selection in the development of next-generation GBM immunotherapies.

Chimeric antigen receptor (CAR) T cells have transformed cancer immunotherapy, yet their truncated or suboptimal intracellular signaling can limit therapeutic efficacy. To enhance proximal signaling of a CD19-targeted CAR, we systematically inserted short Lck-recruiting motifs derived from Lck-adaptor proteins into the CAR intracellular tail. Six candidate sequences from four adaptor molecules (SH2D2A, SKAP1, LAT, LIME), with a sequence from CD3{varepsilon}, known to affect CAR functionality, as a positive control, were tested for expression and functional impact. Three CAR constructs (containing SH2D2A, LAT and LIME1 sequences respectively) displayed reduced surface expression, but only SH2D2A elicited a pronounced rewiring of CAR T cell phenotype following co-culture with CD19+ tumor lines. SH2D2A CAR T cells showed increased CD27 and CD56 expression and reduced expression of effector-associated mediators including granzyme B, IL-2, TNF, and IFN{gamma}. Through systematic mutagenesis and comparative phenotyping of SH2D2A CAR variants, we identified SH2D2A tyrosine 290 (Tyr290) as the critical residue mediating both the altered signaling phenotype and the low surface expression. Additionally, mutation of Tyr254 in the LIME1 CAR restored surface expression in Jurkat T cells, indicating insert- and context-dependent effects on receptor surface expression. Collectively, these results demonstrate that short, intrinsically disordered adaptor-derived sequences -- and single tyrosine residues within them -- can profoundly reprogram CAR signaling and expression.

Myeloid derived suppressor cells (MDSCs) are key players in the immune-suppressed tumor microenvironment (TME) and significantly contribute to immune checkpoint inhibition (ICI) resistance, making them favorable targets for cancer immunotherapy. Epigenetic reprogramming of MDSCs using histone deacetylase (HDAC) inhibitors shows promise to sensitize the TME to ICIs. However, the molecular mechanism of HDAC inhibition in MDSCs has yet to be elucidated. Murine and human MDSC models treated with Entinostat revealed that the long non-coding RNA Malat1 downregulates pSTAT3 and decreases MDSC-mediated suppression of T cell proliferation. Through HDAC inhibitor screens, we identified HDAC1 as preferentially regulating Malat1 expression, STAT3 activation, and MDSC suppression. We also show that HDAC1 inhibition increases MDSC apoptosis by shifting pro-vs. anti-apoptotic signals and increases G0/G1 cell cycle arrest via decreasing G1-S transition cyclin-CDK complexes. Collectively, our findings provide a multi-pronged mechanism of HDAC inhibition in MDSCs that inform the development of future rational combination therapies. One Sentence SummaryHDAC1 inhibition in MDSCs increases Malat1, decreases pSTAT3, induces apoptosis/cell cycle arrest, and decreases suppression of T cells

The JAK-STAT pathway (JSP) is a well-known oncogenic cascade; however, recent clinical trials have detected JSP upregulation in breast cancer following anti-PD1 immunotherapy. This paradoxical observation warrants further investigation into JSPs intercellular heterogeneity, tumor dynamics, molecular mechanisms, and clinical implications for immunotherapy. JSP expression showed dynamic shifts during breast cancer progression, with higher levels in T cells and para-cancerous epithelial cells. In tumor cells, elevated JSP highly correlated with malignant phenotypes. JSP-high tumor cells overexpressed oncogenic pathways, while exhibiting increased immunosuppressive signaling via MIF-CD74 signaling axis. In T cells, higher JSP levels were associated with enhanced cytotoxic activity, improved differentiation, and reduced exhaustion, reflecting robust anti-tumor immunity. Analysis of immunotherapy datasets revealed that higher JSP levels were associated with improved responses towards PD-1 inhibitors, particularly in triple-negative breast cancer (TNBC) patients, with JSP serving as a predictive biomarker for immunotherapy sensitivity. As a key JSP component, STAT4 exerts dual roles in breast cancer: it drives tumorigenesis in malignant cells, sustains breast epithelial cell proliferation, and bolsters T cell anti-tumor functionality--while also acting as a highly accurate biomarker for predicting immunotherapy response. This indicates that JSP targeting demands a nuanced approach: broad inhibition may impair anti-tumor immunity, and optimized therapeutic strategies paired with precise biomarkers are critical to maximize JSPs utility in breast cancer immunotherapy. Our findings highlight JSPs functional heterogeneity in epithelial, tumor, and T cells, with high JSP activity correlating with enhanced immunotherapy efficacy in breast cancer. Graphic Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=117 SRC="FIGDIR/small/703506v1_ufig1.gif" ALT="Figure 1"> View larger version (30K): org.highwire.dtl.DTLVardef@17f041corg.highwire.dtl.DTLVardef@1e6f724org.highwire.dtl.DTLVardef@6b8784org.highwire.dtl.DTLVardef@18e1c90_HPS_FORMAT_FIGEXP M_FIG C_FIG

Despite vaccination, cervical tumors remain a health issue and require treatment improvement. In 2023, Pembrolizumab, an anti-PD-1 immune checkpoint blockade (ICB), was introduced in the case of advanced or metastatic cervical tumors. This treatment significantly increased progression free survival from 20% to 50%. However, some patients remain resistant to anti-PD-1 treatment, which calls for new targets. In our study, we highlighted poliovirus receptor (PVR) and Nectin-2 as potential ICB targets. Indeed, PVR and Nectin-2 are TIGIT ligands, an immunomodulatory checkpoint expressed by regulatory T cells or exhausted T cells. The binding of PVR or Nectin-2 to TIGIT maintains the immunosuppressive signal in the immune cells allowing tumor progression. Furthermore, we observed that PVR and Nectin-2 were highly expressed on tumor cells and tumor associated macrophages (TAMs) accross the different histological subsets of cervical tumors. Therefore, we hypothesized that using anti-PVR and anti-Nectin-2 anti-bodies would lift immunosuppression in cervical tumors. To that end, we used CyTOF to asses precise immunophenotyping of the targets ex vivo, high throughput confocal microscopy to assess phagocytosis, monocyte derived macrophages (MDM) coupled with 3D cell culture models to assess the impact of our treatment on MDM and TAM repolarization and tumor growth. We could demonstrate that our treatment repolarized macrophages towards an inflammatory profile and that this was followed by a reactivation of macrophage cytotoxic function such as phagocytosis. We also demonstrated that anti-PVR and Nectin-2 treatment allowed the control of tumor growth in 2D and 3D cell culture models. We could also develop a pre-clinical model of autologous cell culture from cervical cancer patients. Using the MIVO technology, which combine organotypic culture and fluidics, we could assess peripheral blood mononuclear cells recruitment towards tumor cells in the presence or absence of anti-PVR and anti-Nectin-2. In conclusion we could demonstrate that targeting macrophages via the PVR/Nectin-2 couple reactivates cervical tumor growth control and improves immune cell recruitment.

Cytotoxic CD8+ T cell responses targeting tumor neoantigens are critical for immunotherapy efficacy and are widely studied across different preclinical mouse tumor models. Defined neoantigens are commonly introduced to enable tracking of tumor-specific T cells; however, variation in neoantigen choice may yield immune phenotypes attributable to differences in neoantigen immunogenicity, complicating interpretation of tumor-intrinsic mechanisms. Here, we determined the relative immunogenicity of a set of 25 commonly used mouse tumor-derived and model neoantigens to facilitate comparison of neoantigens across studies. We found that in silico predicted major histocompatibility complex (MHC) binding affinity poorly stratified in vivo immunogenicity. In contrast, experimental measurement of peptide-MHC complex stability (Koff), more so than measured affinity (KD), closely correlated with the relative magnitude of neoantigen-targeted vaccine responses in vivo. Thus, we report the relative stability of a known set of commonly used neoantigens as a reference and provide a simple method to benchmark novel neoantigens against this library. This framework will allow contextualization of the level of immunogenicity of newly identified neoantigens and aid in comparative interpretation of tumor-immune phenotypes across studies.

Peripheral T-cell lymphomas (PTCL) are heterogeneous entities whose tumoral microenvironment (TME) may influence disease phenotype and outcome. To dissect their immune and stromal composition, we used two complementary algorithms, CIBERSORTx and MCP-counter, on Affymetrix data from 255 patients whole-tissue biopsies, including 78 systemic anaplastic large cell lymphomas (ALCL). Clustering based on inferred cell proportions revealed a clear separation between ALCL and other PTCL subtypes, including angioimmunoblastic T-cell lymphoma (AITL) and PTCL-not otherwise specified (PTCL-NOS). ALCL-enriched clusters were characterised by granulocytes and macrophages lineages, mast cells, NK cells, memory CD4+ T-cells, as well as fibroblast and endothelial signatures, whereas as expected, AITL cluster was enriched for T-follicular helper cells, B-cells and macrophages. Finally, we focused on 66 ALCL cases with relapse risk and morphological subtype clinical annotations. Distinct TME features enriched in M1 macrophages and monocytes were associated with adverse outcomes and non-common morphological variants. Transcriptomic analyses of mononuclear phagocytes across Affymetrix and RNAseq datasets confirmed distinct clustering according to cell morphology. These analyses identified potential biomarkers associated with uncommon variants and absent from ALK+ ALCL cell lines, confirming their TME origin. Macrophage- and monocyte-related signatures emerged as key contributors in ALK+ ALCL patients heterogeneity, linking TME patterns to tumor morphology and prognosis. These signatures may serve as biomarkers for patient risk stratification and guide the development of targeted therapies.