Potential Immune Evasion Mechanism Research Articles

Abstract B011: MTA-cooperative PRMT5 inhibition (BMS-986504) induces MTAP del tumor cell-intrinsic immune evasion and regulation

Abstract Homozygous deletion of MTAP gene (MTAP del) occurs in ∼10% of all cancers. BMS- 986504 is a second-generation MTA-cooperative PRMT5 inhibitor designed to preferentially bind to the PRMT5-MTA complex which accumulates in MTAP del cancer cells and has demonstrated clinical proof-of-concept (POC) for selectively inhibiting PRMT5 activity in MTAP del patients as monotherapy. While immunotherapy (IO) has increased patient survival in many cancers and is now the standard of care in first and later lines, most patients ultimately relapse. Thus, there remains an unmet need to improve response for these patients receiving IO. BMS-986504 in combination with anti- PD1 has the potential to increase efficacy, but there is a limited understanding of the interaction between MTAP/PRMT5 biology and PD-1 blockade. Here, we evaluated the BMS-986504-induced immunological and cell killing effects on MTAP del tumor cells and T cells to understand potential mechanisms to support BMS-986504 combination opportunities with anti-PD1 therapy. Using a panel of human PBMC-derived T cells, we first demonstrate that non-activated T cells and T cells activated via anti-CD3/CD28 are insensitive to BMS-986504-induced cell killing at in vitro concentrations equivalent to clinical exposure, supporting the significantly improved selectivity margin of BMS- 986504 relative to first-generation PRMT5 inhibitors that showed T cell toxicity in vitro and on-target dose-limiting hematological toxicity in the clinic. Since previous studies have suggested that MTAP wild-type cells may be affected by MTA secreted from surrounding MTAP del tumors, we assessed T cell viability in the presence of MTA. We found that inactivated T cells maintain insensitivity to BMS-986504 treatment with or without extracellular MTA, but T cells activated via anti-CD3/CD28 are partially sensitive to BMS-986504-induced killing in the presence of MTA only. Using flow cytometry, we characterized the surface expression of immune-related markers on tumor cells treated with BMS-986504 and identified that BMS-986504 dose-dependently increases PD-L1 expression on MTAP del tumor cells, suggesting a potential immune evasion mechanism. Next, using human PBMC-derived T cell and tumor cell co-culture assays, we evaluated the ability of BMS-986504 and anti-PD1 combination to mediate both tumor-intrinsic killing and anti-tumor immune activation in MTAP del cancer cell lines. Taken together, we provide translational proof-of-concept data demonstrating that BMS- 986504 induces tumor cell-intrinsic immunological effects in MTAP del tumors, while having limited impact on T cell viability. This data supports the rationale for BMS- 986504 and IO combination, which may potentially lead to anti-tumor immune activation and improved outcome for MTAP del patients. Citation Format: Josephine Hai, Stephanie Xavier, Sangeeth George, Lars Engstrom, Pete Olson, Tyler Simpson, Ming Lei, Benjamin Chen. MTA-cooperative PRMT5 inhibition (BMS-986504) induces MTAP del tumor cell-intrinsic immune evasion and regulation [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: Tumor Immunology and Immunotherapy; 2024 Oct 18-21; Boston, MA. Philadelphia (PA): AACR; Cancer Immunol Res 2024;12(10 Suppl):Abstract nr B011.

Abstract 5656: Longitudinal spatial profiling reveals chemoresistance mechanisms and characteristics of minimal residual disease in high-grade serous ovarian cancer

Abstract High-grade serous ovarian cancer (HGSOC) is the most lethal gynecologic malignancy globally. Despite an initial response to upfront surgery and platinum-based chemotherapy in most cases, over 70% will relapse. A critical source of recurrence is minimal residual disease (MRD), which persists after upfront treatment yet is clinically undetectable. In this study, we performed second look laparoscopy (SLL) on advanced stage HGSOC patients who had received neoadjuvant chemotherapy (NACT) followed by interval debulking surgery and adjuvant chemotherapy and were in complete clinical remission by imaging and CA-125 tumor marker. Surgical MRD status was determined by pathological review of SLL biopsies. Matched samples from pre-treatment biopsy, interval debulking surgery and SLL in 4 MRD+ and 3 MRD- cases were analyzed using GeoMx Digital Spatial Profiling. Among them, samples from 1 MRD+ and 1 MRD- case were also profiled with Visium. The tumor cells of MRD+ cases exhibited stronger signaling related to hypoxia, angiogenesis, and epithelial-mesenchymal transition at baseline as well as diminished apoptosis signaling after NACT. In addition, progressively upregulated expressions of ATP binding cassette transporters were also observed over time in the tumor compartment of MRD+ cases, potentially contributing to chemoresistance. In the tumor microenvironment, MRD- cases displayed increased abundance of plasma cells, conventional dendritic cells and lymphocytes in both pre-treatment and interval debulking samples compared to MRD+ cases. Notably, Visium data of the MRD- case revealed tertiary lymphoid structures (TLS) in the pre-treatment sample, which became better organized following NACT, with plasma cells disseminating into adjacent tumor areas. Conversely, TLS were fewer and poorly organized in the MRD+ case. Longitudinal comparison of the 3 timepoints in MRD+ cases revealed more regulatory T cells in the stromal compartments of the MRD lesions. Furthermore, from Visium data, exclusion of CD8 T and plasma cells from the tumor core was evident in the MRD lesion. In line with this, strong TGF-β, IL-1β, IL6 and FGF2 signaling surrounding the tumor were noted, likely contributing to immune exclusion. The spatial distribution of multiple immune checkpoint molecules highly overlapped with that of CD8 T cells, indicating T cell exhaustion in the MRD lesion. In summary, these data suggested distinct cancer phenotypic states and immune features in surgically detected MRD+ HGSOC, shedding light on potential chemoresistance and immune evasion mechanisms that contribute to the MRD phase of disease. This study represents the first systemic characterization of ovarian cancer MRD by leveraging SLL, providing insights for designing personalized therapies aimed at eradicating these chemoresistant lesions and ultimately preventing disease recurrence. Citation Format: Yibo Dai, Anne Knisely, Barrett Craig Lawson, Sanghoon Lee, Khalida M. Wani, Rossana N. Lazcano Segura, Brenda Melendez, Jianfeng Chen, Yunhe Liu, Manoj Chelvanambi, Laura A. Gibson, Sarah B. Johnson, Chih-Chen Yeh, Davis R. Ingram, Courtney W. Hudgens, Kyung Serk Cho, Guangsheng Pei, Jiahui Jiang, Yanshuo Chu, Alexander J. Lazar, Jianjun Gao, Jennifer Wargo, Linghua Wang, Amir A. Jazaeri. Longitudinal spatial profiling reveals chemoresistance mechanisms and characteristics of minimal residual disease in high-grade serous ovarian cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 5656.

Tegument protein UL3 of bovine herpesvirus 1 suppresses antiviral IFN-I signaling by targeting STING for autophagic degradation

Bovine herpesvirus 1 (BoHV-1) is a highly contagious pathogen which causes infectious bovine rhinotracheitis in cattle worldwide. Although it has the ability to evade the host's antiviral innate immune response and establish persistent latent infections, the mechanisms are not fully understood, especially the function of the tegument protein to escape innate immunity and participate in viral replication. In this study, we showed that overexpression of tegument protein UL3 facilitates BoHV-1 replication and suppresses the expression of type-I interferon (IFN-I) and IFN-stimulated genes. Then, STING was identified as the target by which UL3 inhibits the IFN-I signaling pathway, and STING was degraded through the UL3-induced autophagy pathway. Furthermore, overexpression of UL3 promotes the expression of the autophagy-related protein ATG101, thereby inducing autophagy. Further study showed that UL3 enhances the interaction between ATG101 and STING, and then the degradation of STING was reversed following ATG101 silencing in UL3-overexpressing cells during BoHV-1 infection. Our research results demonstrate a novel function of UL3 in regulating host's antiviral response and provide a potential mechanism for BoHV-1 immune evasion.

Divergent immune microenvironments in two tumor nodules from a patient with mismatch repair-deficient prostate cancer

Patients with prostate cancer (PC) generally do not respond favorably to immune checkpoint inhibitors, which may be due to a low abundance of tumor-infiltrating lymphocytes even when mutational load is high. Here, we identified a patient who presented with high-grade primary prostate cancer with two adjacent tumor nodules. While both nodules were mismatch repair-deficient (MMRd), exhibited pathogenic MSH2 and MSH6 alterations, had a high tumor mutational burden (TMB), and demonstrated high microsatellite instability (MSI), they had markedly distinct immune phenotypes. The first displayed a dense infiltrate of lymphocytes (“hot nodule”), while the second displayed significantly fewer infiltrating lymphocytes (“cold nodule”). Whole-exome DNA analysis found that both nodules shared many identical mutations, indicating that they were derived from a single clone. However, the cold nodule appeared to be sub-clonal relative to the hot nodule, suggesting divergent evolution of the cold nodule from the hot nodule. Whole-transcriptome RNA analysis found that the cold nodule demonstrated lower expression of genes related to antigen presentation (HLA) and, paradoxically, classical tumor immune tolerance markers such as PD-L1 (CD274) and CTLA-4. Immune cell deconvolution suggested that the hot nodule was enriched not only in CD8+ and CD4 + T lymphocytes, but also in M1 macrophages, activated NK cells, and γδ T cells compared to the cold nodule. This case highlights that MMRd/TMB-high PC can evolve to minimize an anti-tumor immune response, and nominates downregulation of antigen presentation machinery (HLA loss) as a potential mechanism of adaptive immune evasion in PC.

Toxin-neutralizing Abs are associated with improved T cell function following recovery from Staphylococcus aureus infection.

BACKGROUNDT cell responses are impaired in Staphylococcus aureus-infected children, highlighting a potential mechanism of immune evasion. This study tested the hypotheses that toxin-specific antibodies protect immune cells from bacterial killing and are associated with improved T cell function following infection.METHODSS. aureus-infected and healthy children (N = 33 each) were prospectively enrolled. During acute infection and convalescence, we quantified toxin-specific IgG levels by ELISA, antibody function using a cell killing assay, and functional T cell responses by ELISPOT.RESULTSThere were no differences in toxin-specific IgG levels or ability to neutralize toxin-mediated immune cell killing between healthy and acutely infected children, but antibody levels and function increased following infection. Similarly, T cell function, which was impaired during acute infection, improved following infection. However, the response to infection was highly variable; up to half of children did not have improved antibody or T cell function. Serum from children with higher α-hemolysin-specific IgG levels more strongly protected immune cells against toxin-mediated killing. Importantly, children whose serum more strongly protected against toxin-mediated killing also had stronger immune responses to infection, characterized by more elicited antibodies and greater improvement in T cell function following infection.CONCLUSIONThis study demonstrates that, despite T cell impairment during acute infection, S. aureus elicits toxin-neutralizing antibodies. Individual antibody responses and T cell recovery are variable. These findings also suggest that toxin-neutralizing antibodies protect antigen-presenting cells and T cells, thereby promoting immune recovery. Finally, failure to elicit toxin-neutralizing antibodies may identify children at risk for prolonged T cell suppression.FUNDINGNIH National Institute of Allergy and Infectious Diseases R01AI125489 and Nationwide Children's Hospital.

A novel computational tool for tracking cancer energy hijacking from immune cells.

Recent studies revealed a new biological process that malignant cancer cells hijack mitochondria from nearby T cells, providing another potential mechanism for immune evasion. We further confirmed this process at the single-cell genomic level through MERCI, a novel algorithm for tracking mitochondrial (MT) transfer. Applied to human cancer samples, MERCI identified a new cancer phenotype linked to MT hijacking, correlating with rapid tumour proliferation and poor patient survival. This discovery offers insights into the limitations of current cancer immunotherapies and suggests new therapeutic avenues targeting MT transfer to enhance cancer treatment efficacy.

Abstract B037: Single-cell analysis reveals immune characteristics linked to poor prognosis in Fusobacterium nucleatum-infected colorectal cancer

Abstract Fusobacterium nucleatum (Fn) is commonly detected in colorectal cancer (CRC) and worsens patient survival. Fn appears to play a role in colorectal cancer carcinogenesis through suppression of the antitumor immune response. Aiming to uncover the underlying mechanisms, we collected 42 samples of surgically removed colon tissues from patients newly diagnosed with colon cancer. To analyze the bacterial community composition within these tissues, we utilized amplicon sequencing, targeting the V4 variable region of the 16S rRNA. We performed single-cell RNA sequencing (scRNA-seq) analysis of tumor-infiltrating immune cells from Fn-infected [Fn (+)] and Fn-uninfected [Fn (−)] patients. By utilizing gene expression signature derived from scRNA-seq data and bulk transcriptome profiles of the TCGA cohort, we identified immune cell types associated with Fn infection in CRC. Using RNA velocity and cell-cell interaction analysis of single-cell transcriptome data, we unraveled immune cell subtypes modulated by Fn infection. Furthermore, trajectory-based differential expression analysis and single-cell gene network analysis shed light on how the intratumor immune system is disturbed by Fn infection. A novel gene signature had a poor prognostic impact in patients with Fn-infected tumors, compared with Fn-uninfected patients in the TCGA cohort. Overall, this study identified a novel potential Fn-related immune evasion mechanism, beyond suppression of T cell-mediated immune response. Novel gene signatures with a poor prognostic impact can be used for patient stratification and developing targeted strategies in patients with Fn infection. Citation Format: Ilseok Choi, Kyung-A Kim, Yoon Dae Han, Sang Cheol Kim, Han Sang Kim, Insuk Lee. Single-cell analysis reveals immune characteristics linked to poor prognosis in Fusobacterium nucleatum-infected colorectal cancer [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: Tumor Immunology and Immunotherapy; 2023 Oct 1-4; Toronto, Ontario, Canada. Philadelphia (PA): AACR; Cancer Immunol Res 2023;11(12 Suppl):Abstract nr B037.

Importance of metabolic and immune profile as a prognostic indicator in patients with diabetic clear cell renal cell carcinoma.

ccRCC, also known as clear cell renal cell carcinoma, is a cancer that is highly metabolically active and has a strong connection with the immune system. The objective of this research was to investigate the correlation between pathways associated with metabolism, diabetes, immune infiltration, and their impact on the prognosis of ccRCC. We conducted an extensive examination utilizing ssGSEA, ESTIMATE algorithm, WGCNA, and GSVA for gene set enrichment analysis, gene co-expression network analysis, and gene set variation analysis. An established prognostic model, utilizing immune-related WGCNA findings, was evaluated for its association with clinical characteristics and the tumor microenvironment (TME). The ssGSEA effectively categorized ccRCC into groups based on low and high metabolism. Strong associations were observed between scores related to metabolism and immune scores, ESTIMATE scores, stromal scores, and gene expression related to HLA. The analysis conducted by WGCNA revealed a module called the 'yellow module' that exhibited a significant correlation with the infiltration of immune cells and the survival rates of patients. A risk model was developed, demonstrating reliable predictive performance for patient survival outcomes. The risk model also correlated significantly with immune scores and HLA-related gene expressions, suggesting potential immune evasion mechanisms. The analysis of mutations in TCGA data revealed the mutational patterns of ccRCC, and there was a significant correlation between the risk score and clinical characteristics. The GSVA analysis revealed a notable enrichment of pathways associated with cancer in patients at high risk. Finally, in order to evaluate the role of CX3CL1 in renal cell carcinoma cells, we then performed the cell proliferation assays. The results demonstrated that the over expression of CXCL1 could promote the cell proliferation ability in renal cell carcinoma cells. Our findings provide a novel perspective on the interactions between diabetes, metabolic pathways, and the immune landscape in ccRCC. The predictive value of the prognostic model established in this research has the potential to guide the development of new therapeutic and prognostic approaches for patients with ccRCC.

Could Immune Checkpoint Disorders and EBV Reactivation Be Connected in the Development of Hematological Malignancies in Immunodeficient Patients?

Primary immunodeficiencies (PIDs) and secondary immunodeficiencies (SIDs) are characterized by compromised immune function, rendering individuals susceptible to infections and potentially influencing cancer development. Epstein-Barr virus (EBV), a widespread herpesvirus, has been linked to cancer, particularly in those with weakened immune systems. This study aims to compare selected immune parameters, focusing on immune checkpoint molecules (PD-1/PD-L1, CTLA-4/CD86, CD200R/CD200), and EBV reactivation in patients with chronic lymphocytic leukemia (CLL, a representative of SIDs) and common variable immunodeficiency (CVID, a representative of PIDs). We performed a correlation analysis involving patients diagnosed with CLL, CVID, and a healthy control group. EBV reactivation was assessed using specific antibody serology and viral load quantification. Peripheral blood morphology, biochemistry, and immunophenotyping were performed, with emphasis on T and B lymphocytes expressing immune checkpoints and their serum concentrations. Our findings revealed elevated EBV reactivation markers in both CLL and CVID patients compared with healthy controls, indicating increased viral activity in immunodeficient individuals. Furthermore, immune checkpoint expression analysis demonstrated significantly altered percentages of T and B lymphocytes expressing PD-1/PD-L1, CTLA-4/CD86, and CD200R/CD200 in CLL and CVID patients. This suggests a potential interplay between immune checkpoint dysregulation and EBV reactivation in the context of immunodeficiency. In conclusion, our study underscores the intricate relationship between immune dysfunction, EBV reactivation, and immune checkpoint modulation in the context of immunodeficiency-associated cancers. The altered expression of immune checkpoints, along with heightened EBV reactivation, suggests a potential mechanism for immune evasion and tumor progression. These findings provide insights into the complex interactions that contribute to cancer development in immunocompromised individuals, shedding light on potential therapeutic targets for improved management and treatment outcomes. Further investigations are warranted to elucidate the underlying mechanisms and to explore potential interventions to mitigate cancer risk in these patient populations.

Treponema pallidum promoted microglia apoptosis and prevented itself from clearing by human microglia via blocking autophagic flux.

Treponema pallidum (Tp) has a well-known ability to evade the immune system and can cause neurosyphilis by invading the central nervous system (CNS). Microglia are resident macrophages of the CNS that are essential for host defense against pathogens, this study aims to investigate the interaction between Tp and microglia and the potential mechanism. Here, we found that Tp can exert significant toxic effects on microglia in vivo in Tg (mpeg1: EGFP) transgenic zebrafish embryos. Single-cell RNA sequencing results showed that Tp downregulated autophagy-related genes in human HMC3 microglial cells, which is negatively associated with apoptotic gene expression. Biochemical and cell biology assays further established that Tp inhibits microglial autophagy by interfering with the autophagosome-lysosome fusion process. Transcription factor EB (TFEB) is a master regulator of lysosome biogenesis, Tp activates the mechanistic target of rapamycin complex 1 (mTORC1) signaling to inhibit the nuclear translocation of TFEB, leading to decreased lysosomal biogenesis and accumulated autophagosome. Importantly, the inhibition of autophagosome formation reversed Tp-induced apoptosis and promoted microglial clearance of Tp. Taken together, these findings show that Tp blocks autophagic flux by inhibiting TFEB-mediated lysosomal biosynthesis in human microglia. Autophagosome accumulation was demonstrated to be a key mechanism underlying the effects of Tp in promoting apoptosis and preventing itself from clearing by human microglia. This study offers novel perspectives on the potential mechanism of immune evasion employed by Tp within CNS. The results not only establish the pivotal role of autophagy dysregulation in the detrimental effects of Tp on microglial cells but also bear considerable implications for the development of therapeutic strategies against Tp, specifically involving mTORC1 inhibitors and autophagosome formation inhibitors, in the context of neurosyphilis patients.

Exosomes mediate the antibody-resistant intercellular transmission of porcine epidemic diarrhea virus

Porcine epidemic diarrhea virus (PEDV) is a highly pathogenic enteric coronavirus that causes severe enteritis and lethal watery diarrhea in suckling piglets, leading to tremendous economic losses. Exosomes have been reported to participate in intercellular communication by the transportation of a variety of biological materials, including RNAs, lipids, and proteins. However, PEDV transmission routes have not yet been fully elucidated, and whether exosomes function in PEDV transmission remains unclear. In this study, we extracted and purified exosomes from PEDV-infected Vero cells using a stringent isolation method with a combination of chemical precipitation, ultracentrifugation, and incubation with CD63-labeled magnetic beads. We found that exosomes from PEDV-infected Vero cells contain viral genomic RNA and viral nucleocapsid protein. Furthermore, we demonstrated that the purified exosomes from PEDV-infected cells are capable of transmitting the virus to both PEDV-susceptible and non-susceptible cells. Importantly, exosome-mediated PEDV infection was resistant to neutralization by PEDV-specific neutralizing antibodies that potently neutralized free PEDV. Our study reveals a potential immune evasion mechanism utilized by PEDV and provides new insight into the transmission and infection of this important pathogen.

Single cell analysis in head and neck cancer reveals potential immune evasion mechanisms during early metastasis

Profiling tumors at single-cell resolution provides an opportunity to understand complexities underpinning lymph-node metastases in head and neck squamous-cell carcinoma. Single-cell RNAseq (scRNAseq) analysis of cancer-cell trajectories identifies a subpopulation of pre-metastatic cells, driven by actionable pathways including AXL and AURK. Blocking these two proteins blunts tumor invasion in patient-derived cultures. Furthermore, scRNAseq analyses of tumor-infiltrating CD8 + T-lymphocytes show two distinct trajectories to T-cell dysfunction, corroborated by their clonal architecture based on single-cell T-cell receptor sequencing. By determining key modulators of these trajectories, followed by validation using external datasets and functional experiments, we uncover a role for SOX4 in mediating T-cell exhaustion. Finally, interactome analyses between pre-metastatic tumor cells and CD8 + T-lymphocytes uncover a putative role for the Midkine pathway in immune-modulation and this is confirmed by scRNAseq of tumors from humanized mice. Aside from specific findings, this study demonstrates the importance of tumor heterogeneity analyses in identifying key vulnerabilities during early metastasis.

Singapore grouper iridovirus infection counteracts poly I:C induced antiviral immune response in vitro

Groupers are important mariculture fish in South China and Southeast Asian countries. However, the increasing frequency of infectious disease outbreaks has caused great economic losses in the grouper industry. Among these pathogens, Singapore grouper iridovirus (SGIV) infection causes high mortality in larval and juvenile stages of grouper. However, the mechanism underlying the action of viral manipulation on cellular immune response still remained largely uncertain. Here, using RNA-seq technology, we investigated the regulatory roles of SGIV infection on synthetic RNA duplex poly I:C induced immune response in vitro. Using reporter gene assays, we found that SGIV infection decreased poly I:C induced interferon promoter activation. Transcriptomic analysis showed that the mRNA expression levels of 2238 genes were up-regulated, while 1247 genes were down-regulated in poly I:C transfected grouper spleen (GS) cells. Interestingly, SGIV infection decreased the expression of 1479 up-regulated genes and increased the expression of 297 down-regulated genes in poly I:C transfected cells. The differentially expressed genes (DEGs) down-regulated by SGIV were directly related to immune, inflammation and viral infection, and JUN, STAT1, NFKB1, MAPK14A, TGFB1 and MX were the 6 top hub genes in the down-regulated DEGs’ protein-protein interaction (PPI) network. Furthermore, quantitative real-time PCR (qPCR) analysis confirmed that the interferon signaling and inflammatory-related genes, including cGAS, STING, TBK1, MAVS, TNF, IRAK4 and NOD2 were up-regulated by poly I:C stimulation, but all significantly down-regulated after SGIV infection. Thus, we speculated that SGIV infection counteracted poly I:C induced antiviral immune response and this ability helped itself to escape host immune surveillance. Together, our data will contribute greatly to understanding the potential immune evasion mechanism of iridovirus infection in vitro.

Clinical Significance of Glycolytic Metabolic Activity in Hepatocellular Carcinoma.

High metabolic activity is a hallmark of cancers, including hepatocellular carcinoma (HCC). However, the molecular features of HCC with high metabolic activity contributing to clinical outcomes and the therapeutic implications of these characteristics are poorly understood. We aimed to define the features of HCC with high metabolic activity and uncover its association with response to current therapies. By integrating gene expression data from mouse liver tissues and tumor tissues from HCC patients (n = 1038), we uncovered three metabolically distinct HCC subtypes that differ in clinical outcomes and underlying molecular biology. The high metabolic subtype is characterized by poor survival, the strongest stem cell signature, high genomic instability, activation of EPCAM and SALL4, and low potential for benefitting from immunotherapy. Interestingly, immune cell analysis showed that regulatory T cells (Tregs) are highly enriched in high metabolic HCC tumors, suggesting that high metabolic activity of cancer cells may trigger activation or infiltration of Tregs, leading to cancer cells' evasion of anti-cancer immune cells. In summary, we identified clinically and metabolically distinct subtypes of HCC, potential biomarkers associated with these subtypes, and a potential mechanism of metabolism-mediated immune evasion by HCC cells.

Abstract 3142: BRMS1 alters the tumor inflammatory signature and immune infiltration in lung adenocarcinoma

Abstract Background: Lung adenocarcinoma (LUAD) is the leading cause of cancer-related deaths. Metastatic cancer is highly fatal which contributes to at least 90% of cancer-associated morbidities and mortalities. During metastasis, tumor cells alter their signaling cascade and interact with the immune cells in the tumor microenvironment Therefore, it is necessary to characterize and understand how these cancer cells influence tumor-infiltrating immune cells to facilitate and even enhance their ability to metastasize. BRMS1 is a metastasis suppressor gene which is frequently downregulated in LUAD. We, and others, have shown that loss of BRMS1 results in distant metastatic disease. Given the strong correlation between immune suppression, metastasis, and therapy resistance we sought to elucidate if BRMS1 contributes to these processes. Specifically, we hypothesized that LUAD cells downregulate BRMS1 which influences the immune cell composition in the tumor. This creates an immune-suppressive tumor microenvironment aiding in metastasis. Methods: To test our hypothesis, we generated KrasG12D P53fl/fl Brms1-/- mice which spontaneously develop tumors with Ad-Cre intratracheal inoculation. To elucidate the role of BRMS1 in the context of cancer, we performed RNA sequencing on tumors from Brms1 wild type and knockout background. We used MCP counter, an in silico cellular deconvolution algorithm on our bulk RNA seq data to identify various subsets of tumor-infiltrating immune cells. Furthermore, our observations were validated by immunofluorescence and flow cytometry. Results: Differential gene expression analysis using RNA seq data revealed a reduction in CXCL9, CCL5, CLEC1B, CCL9, CCL7 and other proinflammatory molecules in the Brms1-/- tumors. Gene ontology and gene set enrichment analysis highlighted a diminished immune response signature in Brms1-/- tumors. Hallmarks like interferon and IL6 signaling, complement and inflammation are highly enriched in Brms1+/+ tumors. MCP counter also suggested a significant increase in NK cells and reduction in CD8+ T cell population in the Brms1-/- tumors. To validate our observation, we performed immunofluorescence and flow cytometry to assess the number of infiltrating immune cells in the tumor microenvironment. Immunofluorescence data showed reduced cytotoxic T cells (CD8+ T cells) in Brms1-/- mice. The flow cytometric analysis also revealed a reduction in the proliferative potential of these CD8+ T cells along with the increased presence of myeloid-derived suppressor cells in the Brms1-/- mice. Conclusion: Our data suggest for the first time that reduced BRMS1 expression which is generally observed in multiple tumors not only influences metastasis but also alters tumor-infiltrating immune cell composition. Thus, BRMS1 downregulation presents as one of the potential immune evasion mechanisms that could be targeted for an improved therapy outcome in LAUD. Citation Format: Manendra B. Lankadasari, Yuan Liu, Di He, Samhita Bapat, Brooke Mastrogiacomo, Harry B. Lengel, David R. Jones. BRMS1 alters the tumor inflammatory signature and immune infiltration in lung adenocarcinoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 3142.

The genomic and transcriptional landscape of primary central nervous system lymphoma

Primary lymphomas of the central nervous system (PCNSL) are mainly diffuse large B-cell lymphomas (DLBCLs) confined to the central nervous system (CNS). Molecular drivers of PCNSL have not been fully elucidated. Here, we profile and compare the whole-genome and transcriptome landscape of 51 CNS lymphomas (CNSL) to 39 follicular lymphoma and 36 DLBCL cases outside the CNS. We find recurrent mutations in JAK-STAT, NFkB, and B-cell receptor signaling pathways, including hallmark mutations in MYD88 L265P (67%) and CD79B (63%), and CDKN2A deletions (83%). PCNSLs exhibit significantly more focal deletions of HLA-D (6p21) locus as a potential mechanism of immune evasion. Mutational signatures correlating with DNA replication and mitosis are significantly enriched in PCNSL. TERT gene expression is significantly higher in PCNSL compared to activated B-cell (ABC)-DLBCL. Transcriptome analysis clearly distinguishes PCNSL and systemic DLBCL into distinct molecular subtypes. Epstein-Barr virus (EBV)+ CNSL cases lack recurrent mutational hotspots apart from IG and HLA-DRB loci. We show that PCNSL can be clearly distinguished from DLBCL, having distinct expression profiles, IG expression and translocation patterns, as well as specific combinations of genetic alterations.

Sugar Coating: Utilisation of Host Serum Sialoglycoproteins by Schistosoma mansoni as a Potential Immune Evasion Mechanism.

Parasitic helminths resort to various mechanisms to evade and modulate their host’s immune response, several of which have been described for Schistosoma mansoni. We recently reported the presence of sialic acid residues on the surface of adult S. mansoni extracellular vesicles (EVs). We now report that these sialylated molecules are mammalian serum proteins. In addition, our data suggest that most sialylated EV-associated proteins do not elicit a humoral response upon injection into mice, or in sera obtained from infected animals. Sialic acids frequently terminate glycans on the surface of vertebrate cells, where they serve important functions in physiological processes such as cell adhesion and signalling. Interestingly, several pathogens have evolved ways to mimic or utilise host sialic acid beneficially by coating their own proteins, thereby facilitating cell invasion and providing protection from host immune effectors. Together, our results indicate that S. mansoni EVs are coated with host glycoproteins, which may contribute to immune evasion by masking antigenic sites, protecting EVs from removal from serum and aiding in cell adhesion and entry to exert their functions.

CD47-SIRPα-targeted therapeutics: status and prospects.

CD47 is a “don’t eat me” signal to phagocytes that is overexpressed on many tumor cells as a potential mechanism for immune surveillance evasion. CD47 and its interaction with signal-regulating protein alpha (SIRPα) on phagocytes is therefore a promising cancer target. Therapeutic antibodies and fusion proteins that block CD47 or SIRPα have been developed and have shown activity in preclinical models of hematologic and solid tumors. Anemia is a common adverse event associated with anti-CD47 treatment, but mitigation strategies—including use of a low ‘priming’ dose—have substantially reduced this risk in clinical studies. While efficacy in single-agent clinical studies is lacking, findings from studies of CD47–SIRPα blockade in combination with agents that increase ‘eat me’ signals or with antitumor antibodies are promising. Magrolimab, an anti-CD47 antibody, is the furthest along in clinical development among agents in this class. Magrolimab combination therapy in phase Ib/II studies has been well tolerated with encouraging response rates in hematologic and solid malignancies. Similar combination therapy studies with other anti-CD47–SIRPα agents are beginning to report. Based on these early clinical successes, many trials have been initiated in hematologic and solid tumors testing combinations of CD47–SIRPα blockade with standard therapies. The results of these studies will help determine the role of this novel approach in clinical practice and are eagerly awaited.

Potential IFNγ Modulation of Inflammasome Pathway in Chlamydia trachomatis Infected Synovial Cells.

Following a Chlamydia trachomatis infection, the host immune response is characterized by its recognition via Toll-like and Nod-like Receptors, and the subsequent activation of interferon (IFN)-γ-mediated signaling pathways. Recently, the inflammasome-mediated host cell response has emerged to play a role in the physiopathology of C. trachomatis infection. Here we investigated, for the first time, the interaction of IFN-γ and inflammasome in an in vitro model of C. trachomatis-infected primary human synovial cells. Chlamydial replication as well as the expression of caspase-1, IL-1β, as well as IL-18 and IL-6, were assayed. Our results demonstrated the inhibitory activity of IFN-γ by interfering with the inflammasome network through the downregulation of caspase-1 mRNA expression. In addition, the ability of C. trachomatis to hinder the inflammasome pathway favoring its intracellular survival within synovial cells, was observed. Overall, our data suggest a potential mechanism of immune evasion by C. trachomatis in synovial cells, that may be contested by IFN-γ.

Impending disaster: rise of the epsilon variant in Pakistan and the way forward.

The constantly mutating severe acute respiratory syndrome coronavirus 2 (SARS-COV-2) does not appear to be slowing down any time soon. All countries, particularly developing countries, must adapt and strategically plan their way of life around the pandemic, while doing everything possible to keep the mortality rate and spread of the newly emerging variants as low as possible, in order to avoid a further blow to the economy and way of life. Pakistan is one such developing country that is currently battling the dangerous delta strain of SARS-COV-2 with limited resources and has recently seen the emergence of an equally transmissible and highly infectious epsilon strain. This is a concerning situation considering that Pakistan's already overburdened health system and faltering economy cannot withstand another dangerous SARS-COV-2 variant attack. This article highlights some strategies for the country to fortify its defences to prevent the epsilon variant from spreading before it is too late, and emphasises that while identifying potential immune evasion mechanisms in SARS-COV-2 variants is critical in the fight against COVID-19, it is also critical to develop methods of efficient and cost-effective detection to identify an early outbreak and then vigilantly and systematically plan area lockdowns before any hope of conquering this pandemic is lost.