Location, location, location: CD103 demarcates intraepithelial, prognostically favorable CD8+ tumor-infiltrating lymphocytes in ovarian cancer

PD-1 and TIGIT coexpressing CD8 + CD103 + tissue-resident memory cells in endometrial cancer as potential targets for immunotherapy

BACKGROUND

Immunotherapy has shown promise in treating various cancers; however, its efficacy in endometrial cancer (EC) remains suboptimal owing to the complex dynamics of the tumour immune microenvironment. This study focuses on exploring the potential of targeting the programmed cell death protein 1 gene (PD-1) and the T cell Immunoreceptor with Ig and ITIM domains gene (TIGIT) coexpressing tissue-resident memory cells in EC.

METHODS

A comprehensive approach, utilizing RNA sequencing, single-cell RNA sequencing, mass cytometry, and flow cytometry, was employed to analyse the expression patterns of PD-1 and TIGIT in the EC tumor environment and to characterize the phenotypic properties of tumor-infiltrating lymphocytes (TILs), particularly tissue-resident memory (TRM) cells. Additionally, in vitro cell experiments were conducted to assess the functional impact of PD-1 and TIGIT blockade on T-cell activity.

RESULTS

Our analysis identified a significant co-expression of PD-1 and TIGIT in TRM cells within the EC tumor microenvironment. These TRM cells displayed an exhausted phenotype with impaired cytotoxicity, enhanced proliferative capacity, and diminished cytotoxic activity. In vitro T-cell assays showed that a dual blockade of PD-1 and TIGIT more effectively restored T-cell functionality compared to single blockade, suggesting enhanced therapeutic potential.

CONCLUSIONS

TRM cells co-expressing PD-1 and TIGIT represent potential targets for EC immunotherapy. Dual immune checkpoint blockade targeting PD-1 and TIGIT may offer an effective therapeutic strategy for EC, providing valuable insights for the development of immunotherapeutic approaches.

Improved overall survival in patients with high-grade serous ovarian cancer is associated with CD16a+ immunologic neighborhoods containing NK cells, T cells and macrophages

Background

For patients with high grade serous carcinoma of the ovary (HGSC), survival rates have remained static for the last half century. Despite the presence of tumor mutations and infiltration of immune cells, existing immunotherapies have achieved little success against HGSC. These observations highlight a gap in the understanding of how the immune system functions and interacts within HGSC tumors.

Methods

We analyzed duplicate core samples from 939 patients with HGSC to understand patterns of immune cell infiltration, localization, and associations with clinical features. We used high-parameter immunohistochemical/Opal multiplex, digital pathology, computational biology, and multivariate analysis to identify immune cell subsets and their associations with HGSC tumors.

Results

We defined six patterns of cellular infiltration by spatially restricted unsupervised clustering of cell subsets. Each pattern was represented to some extent in most patient samples, but their specific distributions differed. Overall (OS) and progression-free survival (PFS) corresponded with higher infiltration of CD16a+ cells, and their co-localization with macrophages, T cells, NK cells, in one of six cellular neighborhoods that we defined with our spatial assessment.

Conclusions

Immune cell neighborhoods containing CD16a+ cells are associated with improved OS and PFS for patients with HGSC. Patterns of immunologic neighborhoods differentiate patient outcomes, and could inform future, more precise approaches to treatment.

Methods behind oncolytic virus-based DC vaccines in cancer: Toward a multiphase combined treatment strategy for Glioblastoma (GBM) patients

Glioblastoma (GBM) remains an orphan cancer disease with poor outcome. Novel treatment strategies are needed. Immunotherapy has several modes of action. The addition of active specific immunotherapy with dendritic cell vaccines resulted in improved overall survival of patients. Integration of DC vaccination within the first-line combined treatment became a challenge, and immunogenic cell death immunotherapy during chemotherapy was introduced. We used a retrospective analysis using real world data to evaluate the complex combined treatment, which included individualized multimodal immunotherapy during and after standard of care, and which required adaptations during treatment, and found a further improvement of overall survival. We also discuss the use of real world data as evidence. Novel strategies to move the field of individualized multimodal immunotherapy forward for GBM patients are reviewed.

Single-cell profiling of T cells uncovers a tissue-resident memory-like T-cell subset associated with bidirectional prognosis for B-cell acute lymphoblastic leukemia

Introduction

The character and composition of leukemia-related T cells are closely related to the treatment response and prognosis for patients. Though B cell-acute lymphoblastic leukemia (B-ALL) patients have benefited from immune-based approaches, such as chimeric antigen receptor T cells therapy, some of them still end with poor prognosis, especially for adult patients. Therefore, deep understanding of the developmental relationship between T cell subtypes in relation to B-ALL patient prognosis is urgently needed.

Methods

We analyzed the peripheral blood T cell single-cell RNA sequencing data of three B-ALL patients, using data from 11 healthy individuals as controls. In total, 16,143 and 53,701 T cells from B-ALL patients and healthy adults, respectively, were objectively analyzed for detailed delineation of 13 distinct T cell clusters. Cluster-specific genes were used as marker genes to annotate each T cell subtype.

Results

Unbiased analysis enabled the discovery of circulating CD103+ T cell (CD3+CD103+MKI67+), also defined as tissue-resident memory-like T (Trm-like) cell, populations were elevated in B-ALL patients, which expressed high level of cell proliferation and exhaustion related genes. In addition, cell fate trajectory analysis showed these Trm-like cells, which shared T-cell receptor (TCR) clonotypes with exhausted T (Tex) cells and effector T (Teff) cells, were supposed to transition into Teff cells; however, mainly transformed into Tex cells in leukemia environment. More importantly, Trm-like cells transformation into Teff cells and Tex cells potentially led to favorable or poor prognosis for B-ALL patients, respectively.

Conclusion

In sum, a circulating Trm-like cell subset with high level expression of cell proliferation and exhaustion related genes was elevated in B-ALL patients. The bidirectional developmental potential of these T cells into Teff or Tex is closely associated with favorable or poor prognosis, respectively. Together, our study provided a unique insight of alteration of leukemia related T cells, also showed a potential immunotherapy direction and prognosis assessment model for B-ALL patients.

Tumor-Infiltrating Lymphocytes (TILs) in Epithelial Ovarian Cancer: Heterogeneity, Prognostic Impact, and Relationship with Immune Checkpoints

Epithelial ovarian cancers (EOC) are often diagnosed at an advanced stage with carcinomatosis and a poor prognosis. First-line treatment is based on a chemotherapy regimen combining a platinum-based drug and a taxane-based drug along with surgery. More than half of the patients will have concern about a recurrence. To improve the outcomes, new therapeutics are needed, and diverse strategies, such as immunotherapy, are currently being tested in EOC. To better understand the global immune contexture in EOC, several studies have been performed to decipher the landscape of tumor-infiltrating lymphocytes (TILs). CD8+ TILs are usually considered effective antitumor immune effectors that immune checkpoint inhibitors can potentially activate to reject tumor cells. To synthesize the knowledge of TILs in EOC, we conducted a review of studies published in MEDLINE or EMBASE in the last 10 years according to the PRISMA guidelines. The description and role of TILs in EOC prognosis are reviewed from the published data. The links between TILs, DNA repair deficiency, and ICs have been studied. Finally, this review describes the role of TILs in future immunotherapy for EOC.

The Abundance of Tumor-Infiltrating CD8+ Tissue Resident Memory T Lymphocytes Correlates with Patient Survival in Glioblastoma

Glial tumors alone account for 40% of all CNS tumors and present a low survival rate. The tumor microenvironment is a critical regulator of tumor progression and therapeutic effectiveness in glioma. Growing evidence from numerous studies of human solid tumor-infiltrating CD8⁺ T cells indicates that tissue-resident memory T cells (TRM) represent a substantial subpopulation of tumor-infiltrating lymphocytes (TILs). Although it is reported that some types of cancer patients with high immune infiltration tend to have better outcomes than patients with low immune infiltration, it seems this does not happen in gliomas. This study aimed to characterize TRMs cells in the glioma tumor microenvironment to identify their potential predictive and prognostic role and the possible therapeutic applications. Fluorescence activated cell sorting (FACS) analysis and immunofluorescence staining highlighted a statistically significant increase in CD8⁺ TRM cells (CD103⁺ and CD69⁺ CD8⁺ T cells) in gliomas compared to control samples (meningioma). In-silico analysis of a dataset of n = 153 stage IV glioma patients confirmed our data. Moreover, the gene expression analysis showed an increase in the expression of TRM-related genes in tumor tissues compared to normal tissues. This analysis also highlighted the positive correlation between genes associated with CD8⁺ TRM and TILs, indicating that CD8⁺ TRMs cells are present among the infiltrating T cells. Finally, high expression of Integrin subunit alpha E (ITGAE), the gene coding for the integrin CD103, and high CD8⁺ TILs abundance were associated with more prolonged survival, whereas high ITGAE expression but low CD8⁺ TILs abundance were associated with lower survival.

Prognostic Significance of Lymphocyte Infiltrate Localization in Triple-Negative Breast Cancer

High infiltration by tumor-infiltrating lymphocytes (TILs) is associated with favorable prognosis in different tumor types, but the clinical significance of their spatial localization within the tumor microenvironment is debated. To address this issue, we evaluated the accumulation of intratumoral TILs (itTILs) and stromal TILs (sTILs) in samples from 97 patients with early triple-negative breast cancer (TNBC) in the center (sTIL central) and periphery (sTIL peripheral) of tumor tissues. Moreover, the presence of primary and secondary lymphoid aggregates (LAs) and the expression levels of the cancer testis antigen (CTA), NY-ESO-1, and PD-L1 were explored. High infiltration by itTILs was observed in 12/97 samples (12.3%), unrelated to age, Ki67 expression, tumor size, histologic type and grade, and LA presence. NY-ESO-1 was expressed in tumor cells in 37 samples (38%), with a trend suggesting a correlation with itTIL infiltration (p = 0.0531). PD-L1 expression was detected in immune cells in 47 samples (49%) and was correlated with histologic grade, sTILs, and LA formation. The presence of primary LAs was significantly correlated with better disease-free survival (DFS) (p = 0.027). Moreover, no tumor progression was observed during >40 months of clinical follow up in the 12 patients with high itTILs or in the 14 patients with secondary LAs. Thus, careful evaluation of lymphoid infiltrate intratumoral localization might provide important prognostic information.

SAR131675, a VEGRF3 Inhibitor, Modulates the Immune Response and Reduces the Growth of Colorectal Cancer Liver Metastasis

Simple Summary

Colorectal cancer most often metastasizes to the liver, and in most cases, it is unresectable at diagnosis. New treatment options targeting specific cancer characteristics are needed and are currently being explored. Herein we looked at the use of a selective VEGFR-3 tyrosine kinase inhibitor, SAR131675, as an anti-tumor agent in a mouse model of colorectal liver metastasis. We found that SAR131675 dramatically reduced tumor growth and changed the immune response within the tumor and the surrounding liver, suggesting the use of SAR131675 as an adjuvant therapy for colorectal liver metastasis.

Abstract

Most patients with colorectal cancer (CRC) develop metastases, predominantly in the liver (CLM). Targeted therapies are being investigated to improve current CLM treatments. This study tested the effectiveness of SAR131675, a selective VEGFR-3 tyrosine kinase inhibitor, to inhibit CLM in a murine model. Following intrasplenic induction of CLM, mice were treated daily with SAR131675. Tumor growth and immune infiltrates into tumor and liver tissues were assessed at 10-, 16- and 22-days post tumor induction by stereology, IHC and flow cytometry. SAR151675 treatment significantly reduced tumor burden and F4/80⁺ macrophages in the liver tissues. Analysis of immune cell infiltrates in liver showed tissue that at day 22, had the proportion of CD45⁺ leukocytes significantly reduced, particularly myeloid cells. Analysis of myeloid cells (CD11b⁺ CD45⁺) indicated that the proportion of F4/80⁻ Ly6C^low was significantly reduced, including a predominate PD-L1⁺ subset, while CD3⁺ T cells increased, particularly CD8⁺ PD1⁺, reflected by an increase in the CD8⁺:CD4⁺ T cell ratio. In the tumor tissue SAR11675 treatment reduced the predominant population of F4/80⁺ Ly6C^lo and increased CD4⁺ T cells. These results suggest that SAR131675 alters the immune composition within tumor and the surrounding liver in the later stages of development, resulting in a less immunosuppressive environment. This immunomodulation effect may contribute to the suppression of tumor growth.

Tissue-resident immunity in the female and male reproductive tract

The conception of how the immune system is organized has been significantly challenged over the last years. It became evident that not all lymphocytes are mobile and recirculate through secondary lymphoid organs. Instead, subsets of immune cells continuously reside in tissues until being reactivated, e.g., by a recurring pathogen or other stimuli. Consequently, the concept of tissue-resident immunity has emerged, and substantial evidence is now available to support its pivotal function in maintaining tissue homeostasis, sensing challenges and providing antimicrobial protection. Surprisingly, insights on tissue-resident immunity in the barrier tissues of the female reproductive tract are sparse and only slowly emerging. The need for protection from vaginal and amniotic infections, the uniqueness of periodic tissue shedding and renewal of the endometrial barrier tissue, and the demand for a tailored decidual immune adaptation during pregnancy highlight that tissue-resident immunity may play a crucial role in distinct compartments of the female reproductive tract. This review accentuates the characteristics of tissue-resident immune cells in the vagina, endometrium, and the decidua during pregnancy and discusses their functional role in modulating the risk for infertility, pregnancy complications, infections, or cancer. We here also review data published to date on tissue-resident immunity in the male reproductive organs, which is still a largely uncharted territory.

Cell by cell immuno- and cancer marker profiling of non-small cell lung cancer tissue: Checkpoint marker expression on CD103+, CD4+ T-cells predicts circulating tumor cells

Non-small cell lung cancer (NSCLC) has a poor prognosis. Targeted therapy and immunotherapy in recent years has significantly improved NSCLC patient outcome. In this study, we employed cell-by-cell immune and cancer marker profiling of the primary tumor cells to investigate possible signatures that might predict the presence or absence of circulating tumor cells (CTCs). We performed a comprehensive study on 10 NSCLC patient tissue samples with paired blood samples. The solid tissue biopsy samples were dissociated into single cells by non-enzymatic tissue homogenization and stained with a total 25 immune, cancer markers and DNA content dye and analyzed with high-parameter flow cytometry. CTCs were isolated and analyzed from the paired peripheral blood. We investigated a total of 74 biomarkers for their correlation with CTC number. Strong correlations were observed between CTC number and the frequency of immune checkpoint marker expressing lymphocytes (CTLA-4, LAG3, TIM3, PD-1), within the CD103⁺CD4⁺ T lymphocyte subset. CTC number is also correlated with the frequency of PD-L1 expressing cancer cells and cancer cell DNA content. In contrast, CTC number inversely correlated to the frequency of CD44⁺E-cadherin^- cancer cells. Unsupervised clustering analysis based on the biomarker analysis separated the CTC negative patients from the CTC positive patients. Profiling multiple immune and cancer markers on cancer samples with multi-parametric flow cytometry allowed us to obtain protein expression information at the single cell level. Clustering analysis of the proteomic data revealed a signature driven by checkpoint marker expression on CD103⁺CD4⁺ T cells that could potentially be predictive of CTCs and targets of therapy.

Epithelial Ovarian Cancer and the Immune System: Biology, Interactions, Challenges and Potential Advances for Immunotherapy

Recent advances in the understanding of immune function and the interactions with tumour cells have led to the development of various cancer immunotherapies and strategies for specific cancer types. However, despite some stunning successes with some malignancies such as melanomas and lung cancer, most patients receive little or no benefit from immunotherapy, which has been attributed to the tumour microenvironment and immune evasion. Although the US Food and Drug Administration have approved immunotherapies for some cancers, to date, only the anti-angiogenic antibody bevacizumab is approved for the treatment of epithelial ovarian cancer. Immunotherapeutic strategies for ovarian cancer are still under development and being tested in numerous clinical trials. A detailed understanding of the interactions between cancer and the immune system is vital for optimisation of immunotherapies either alone or when combined with chemotherapy and other therapies. This article, in two main parts, provides an overview of: (1) components of the normal immune system and current knowledge regarding tumour immunology, biology and their interactions; (2) strategies, and targets, together with challenges and potential innovative approaches for cancer immunotherapy, with attention given to epithelial ovarian cancer.

Intratumoral CD103-positive tumour-infiltrating lymphocytes are associated with favourable prognosis in patients with triple-negative breast cancer

AIMS

Cluster of differentiation 103 (CD103), a marker of tissue resident memory T cells, is expressed on subsets of CD8⁺ T lymphocytes. We investigated the prognostic significance of CD103⁺ intra-epithelial tumour-infiltrating lymphocytes (iTILs) in invasive breast cancer (IBC).

METHODS AND RESULTS

Immunohistochemistry was performed for CD103, CD8 and TGF-β isoforms (1, 2 and 3) on tissue microarrays of 1187 IBC samples. CD103⁺ and CD8⁺ iTILs were present in 904 (76.2%) and 854 (74%) cases with an overall mean ± standard deviation of 38.2 ± 100.2/mm² and 30.4 ± 89.7/mm² , respectively. The numbers of CD103⁺ and CD8⁺ iTILs were positively correlated, and CD103⁺ iTILs outnumbered CD8⁺ iTILs in HER2-positive and triple-negative breast cancer (TNBC). CD103⁺ and CD8⁺ iTIL densities were significantly higher in tumours of histological grade 3, absence of lymphovascular invasion, high Ki-67 index, high stromal TIL density or TGF-β3 expression. High CD103⁺ iTIL density was associated with better disease-free survival (DFS, P = 0.007), but no significant association was observed for overall survival (OS). Subgroup analysis by cancer molecular subtype showed that CD103⁺ iTIL count was prognostic only for TNBC (OS, P = 0.035; DFS, P = 0.009). CD8⁺ iTIL density was significant for DFS, but not for OS, in the entire cohort and TNBC. In multivariate analysis, CD103⁺ iTIL density was an independent prognostic factor of OS (P = 0.02) and DFS (P = 0.007) in TNBC, while CD8⁺ iTIL density was not significant for survival.

CONCLUSIONS

CD103 iTIL density can serve as a predictor of good prognosis in patients with TNBC.

The Perfect Combination: Enhancing Patient Response to PD-1-Based Therapies in Epithelial Ovarian Cancer

Epithelial ovarian cancer (EOC) is the most lethal gynecologic malignancy, with an overall 5-year survival of only 47%. As the development of novel targeted therapies is drastically necessary in order to improve patient survival, current EOC clinical trials have heavily focused on immunotherapeutic approaches, centered upon programmed cell death 1 (PD-1) inhibitors. While PD-1 monotherapies have only exhibited modest responses for patients, it has been theorized that in order to enhance EOC patient response to immunotherapy, combinatorial regimens must be investigated. In this review, unique challenges to EOC PD-1 response will be discussed, along with a comprehensive description of both preclinical and clinical studies evaluating PD-1-based combinatorial therapies. Promising aspects of PD-1-based combinatorial approaches are highlighted, while also discussing specific preclinical and clinical areas of research that need to be addressed, in order to optimize EOC patient immunotherapy response.

Integrated Analysis of Prognostic and Immune Associated Integrin Family in Ovarian Cancer

Human integrin receptors are important for cell-cell and cell-matrix adhesion in normal epithelial cells. Emerging evidences have indicated integrin members are involved in cancer development and progression as well. However, the expression patterns and clinical significance of the whole integrin family in ovarian cancer (OC) have not yet been well understood. In the present study, we utilized the public datasets including GEPIA, GEO, ONCOMINE, cBioPortal, Kaplan-Meier Plotter, TIMER databases, to analyze the expression and prognostic value of integrin members in OC. We found ITGA3/B4/B6/B7/B8 were abnormally overexpressed in OC; ITGA6 was good prognosis predictor in OC; ITGA3/ B4/B8 were poor prognosis predictor specially in advanced OC patients; elevated ITGA3/B4 might promote metastasis and elevated ITGA3/B8 might promote platinum resistance of OC; ITGA3 and ITGB4 might synergistically or independently regulate cell adhesion and proliferation; ITGA4/AL/AM/AX/B2/B7 showed strong correlations with various tumor immune infiltrates (TILs), especially with pro-tumor immunes cell types like monocyte, M2 macrophage and exhaustion T cells infiltration; ITGAL/AM/B2/B7 and residing memory CD8+ T cells marker ITGAE were specially associated with early OC patients outcome. Our results implied that ITGA3/B4 were important prognostic markers of advanced OC, ITGAL/AM/ B2/B7 were immune associated prognosis markers of early OC, together they might render important therapeutic targets for OC.

Characterization of CD103+ CD8+ tissue-resident T cells in esophageal squamous cell carcinoma: may be tumor reactive and resurrected by anti-PD-1 blockade

Though therapy that promotes anti-tumor response about CD8⁺ tumor-infiltrating lymphocytes (TILs) has shown great potential, clinical responses to CD8⁺ TILs immunotherapy vary considerably, largely because of different subpopulation of CD8⁺ TILs exhibiting different biological characters. To define the relationship between subpopulation of CD8⁺ TILs and the outcome of antitumor reaction, the phenotype and function of CD103⁺ CD8⁺ TILs in esophageal squamous cell carcinoma (ESCC) were investigated. CD103⁺ CD8⁺ TILs were presented in ESCC, which displayed phenotype of tissue-resident memory T cells and exhibited high expression of immune checkpoints (PD-1, TIM-3). CD103⁺ CD8⁺ TILs were positively associated with the overall survivals of ESCC patients. This population of cells elicited potent proliferation and cytotoxic cytokine secretion potential. In addition, CD103⁺ CD8⁺ TILs were elicited potent anti-tumor immunity after anti-PD-1 blockade and were not affected by chemotherapy. This study emphasized the feature of CD103⁺ CD8⁺ TILs in immune response and identified potentially new targets in ESCC patients.

Local heroes or villains: tissue-resident memory T cells in human health and disease

Tissue-resident memory T (T_RM) cells are increasingly associated with the outcomes of health and disease. T_RM cells can mediate local immune protection against infections and cancer, which has led to interest in T_RM cells as targets for vaccination and immunotherapies. However, these cells have also been implicated in mediating detrimental pro-inflammatory responses in autoimmune skin diseases such as psoriasis, alopecia areata, and vitiligo. Here, we summarize the biology of T_RM cells established in animal models and in translational human studies. We review the beneficial effects of T_RM cells in mediating protective responses against infection and cancer and the adverse role of T_RM cells in driving pathology in autoimmunity. A further understanding of the breadth and mechanisms of T_RM cell activity is essential for the safe design of strategies that manipulate T_RM cells, such that protective responses can be enhanced without unwanted tissue damage, and pathogenic T_RM cells can be eliminated without losing local immunity.

Accumulation of CD103+ CD8+ T cells in a cutaneous melanoma micrometastasis

Objective

The immune system can halt cancer progression by suppressing outgrowth of clinically occult micrometastases in a state of cancer-immune equilibrium. Cutaneous melanoma provides a unique opportunity to study the immune contexture of such lesions, as miniscule skin metastases are accessible to clinical inspection and diagnostic biopsy.

Methods

Here, we analysed by multiplex immunofluorescence microscopy samples from a melanoma patient presenting with an overt and an occult in-transit metastasis (ITM), the latter of which appeared as a small erythematous papule.

Results

Microarchitecture and immune composition in the two lesions were vastly different. CD4⁺ and CD8⁺ T cells accumulated around the margin of the overt SOX10⁺ Melan A⁺ ITM but were largely excluded from the tumor centre. By contrast, the occult micrometastasis contained only few SOX10⁺ Melan A^- melanoma cells which were scattered within a dense infiltrate of T cells, including a prominent population of CD103⁺ CD8⁺ T cells resembling tissue-resident memory T (T_RM) cells. Notably, almost every single melanoma cell in the micrometastasis was in close proximity to these T_RM-like cells.

Conclusion

Such results support the emerging concept that CD103⁺ CD8⁺ T_RM cells are key mediators of cancer surveillance and imply an important function of these cells in controlling clinically occult micrometastases in humans.

Promising Cytomegalovirus-Based Vaccine Vector Induces Robust CD8+ T-Cell Response

Vaccination has had great success in combating diseases, especially infectious diseases. However, traditional vaccination strategies are ineffective for several life-threatening diseases, including acquired immunodeficiency syndrome (AIDS), tuberculosis, malaria, and cancer. Viral vaccine vectors represent a promising strategy because they can efficiently deliver foreign genes and enhance antigen presentation in vivo. However, several limitations, including pre-existing immunity and packaging capacity, block the application of viral vectors. Cytomegalovirus (CMV) has been demonstrated as a new type of viral vector with additional advantages. CMV could systematically elicit and maintain high frequencies of effector memory T cells through the "memory inflation" mechanism. Studies have shown that CMV can be genetically modified to induce distinct patterns of CD8+ T-cell responses, while some unconventional CD8+ T-cell responses are rarely induced through conventional vaccine strategies. CMV has been used as a vaccine vector to deliver many disease-specific antigens, and the efficacy of these vaccines was tested in different animal models. Promising results demonstrated that the robust and unconventional T-cell responses elicited by the CMV-based vaccine vector are essential to control these diseases. These accumulated data and evidence strongly suggest that a CMV-based vaccine vector represents a promising approach to develop novel prophylactic and therapeutic vaccines against some epidemic pathogens and tumors.

Prognostic significance of resident CD103+CD8+T cells in human colorectal cancer tissues

The prognostic significance and clinical implications of resident CD103⁺CD8⁺T cells in human colorectal cancer tissues still remains largely unexplored. In our present study, we aimed to characterize the resident CD8⁺T cells in human colorectal cancer tissues by using double staining of CD103 and CD8, and further evaluated the prognostic significance of resident CD8⁺T cells in colorectal cancer. We found that the OS rate of the colorectal cancer patients with higher infiltration of CD8⁺T cells, or with higher numbers of resident CD103⁺CD8⁺T cells, or with higher ratio of CD103⁺CD8⁺T cells over total CD8⁺T cells in cancer tissues was significantly better than that of the patients with lower infiltration of CD8⁺T cells, or with lower numbers of resident CD103⁺CD8⁺T cells, or with higher ratio of CD103⁺CD8⁺T cells over total CD8⁺T cells in cancer tissues, respectively. Moreover, higher infiltration of CD8⁺T cells in colorectal cancer tissues was significantly and inversely correlated with advanced TNM stage. Higher numbers of resident CD103⁺CD8⁺T cells in colorectal cancer tissues were significantly and inversely correlated with distant metastasis status. Higher ratio of CD103⁺CD8⁺T cells over total CD8⁺T cells in colorectal cancer tissues was significantly and inversely correlated with age status. The COX model analysis demonstrated that higher infiltration of CD8⁺T cells, higher numbers of resident CD103⁺CD8⁺T cells, or higher ratio of CD103⁺CD8⁺T cells over total CD8⁺T cells in colorectal cancer tissues, could serve as independent prognostic predictors for colorectal cancer patients. Taken together, our present study demonstrated the density of tumor infiltrating CD8⁺T cells or the numbers of resident CD103⁺CD8⁺T cells in colorectal tissues could be used as an important prognostic predictor for this malignancy.

Parallel worlds of the adaptive and innate immune cell networks

Adaptive and innate immune cells have typically been functionally and temporally segregated even though they share a number of salient features. Over the past decade, significant advances have been made in understanding the composition and diversity of both innate and adaptive cell populations. This has shed light on how cells from two distinct pathways are so highly complementary. Innate lymphoid cells (ILCs) are pivotally positioned in tissues to form a stable population akin to tissue-resident T cells that protects the body. Nevertheless, the pathway by which different lymphocytes enter tissues, terminally differentiate and are replenished to maintain populations remains incompletely understood. Recent evidence challenges our assumptions about the sedentary lifestyles of so called 'tissue-resident cells' and pushes us to consider their roles in orchestrating protection of the immune system beyond the classical models.

NKG2A Blockade Potentiates CD8 T Cell Immunity Induced by Cancer Vaccines

Tumor-infiltrating CD8 T cells were found to frequently express the inhibitory receptor NKG2A, particularly in immune-reactive environments and after therapeutic cancer vaccination. High-dimensional cluster analysis demonstrated that NKG2A marks a unique immune effector subset preferentially co-expressing the tissue-resident CD103 molecule, but not immune checkpoint inhibitors. To examine whether NKG2A represented an adaptive resistance mechanism to cancer vaccination, we blocked the receptor with an antibody and knocked out its ligand Qa-1b, the conserved ortholog of HLA-E, in four mouse tumor models. The impact of therapeutic vaccines was greatly potentiated by disruption of the NKG2A/Qa-1b axis even in a PD-1 refractory mouse model. NKG2A blockade therapy operated through CD8 T cells, but not NK cells. These findings indicate that NKG2A-blocking antibodies might improve clinical responses to therapeutic cancer vaccines.

Resident Memory-Like Tumor-Infiltrating Lymphocytes (TILRM): Latest Players in the Immuno-Oncology Repertoire

Resident memory T cells (TRM) are a recently identified subset of long-lived memory T cells that are characterized in terms of their unique surface phenotype combined with a non-recirculating pattern of localization to non-lymphoid, peripheral tissues. TRM have quickly become a key area of focus in understanding immune responses to microbial infection in so-called "barrier" tissues, and appear to be particularly critical for protection against repeat exposure at the same site. More recently, tumor-infiltrating T cells with canonical TRM features are being identified in human cancers, in particular cancers of epithelial origin, and their presence is broadly found to be associated with favorable long-term prognosis. Moreover, recent studies have shown that these "resident memory-like" tumor-infiltrating lymphocytes (referred to herein as TILRM) are uniquely activated in melanoma patients undergoing PD-1 directed checkpoint blockade therapy. Accordingly, there is much interest at present regarding the biology of these cells and their precise role in anti-cancer immunity. Herein, we review the current state of the literature regarding TILRM with a specific emphasis on their specificity, origins, and relationship to conventional pathogen-specific TRM and speculate upon the way(s) in which they might contribute to improved prognosis for cancer patients. We discuss the growing body of evidence that suggests TILRM may represent a population of bona-fide tumor-reactive T cells and the attractive possibility of leveraging this cell population for future immunotherapy.

Role of Tissue-Resident Memory in Intra-Tumor Heterogeneity and Response to Immune Checkpoint Blockade

Tissue-resident memory T (T_RM) cells are a distinct subset of memory T cells that reside in non-lymphoid tissues for prolonged periods of time without significant recirculation providing continued immune surveillance at these sites. Recent studies suggest that T_RM cells are also enriched within tumor tissue. Expression of inhibitory immune checkpoints (ICPs) is particularly enriched on this subset of tumor-infiltrating T cells, suggesting that they are major targets for newer therapies targeting ICPs such as the programmed death-1 pathway. Recent studies suggest that tissue restriction of these cells without recirculation may also lead to heterogeneity of T_RM cells within individual metastatic lesions, ultimately leading to inter-lesional diversity. Thus, individual metastatic lesions may contain genomically distinct immune microenvironments that impact both evolution of tumors as well as the mechanisms underlying response and resistance to immune therapies. Understanding the biology of T_RM cells infiltrating tumors will be essential to improving immune-based approaches in diverse settings.

Immune Curbing of Cancer Stem Cells by CTLs Directed to NANOG

Cancer stem cells (CSCs) have been identified as the source of tumor growth and disease recurrence. Eradication of CSCs is thus essential to achieve durable responses, but CSCs are resistant to current anti-tumor therapies. Novel therapeutic approaches that specifically target CSCs will, therefore, be crucial to improve patient outcome. Immunotherapies, which boost the body's own immune system to eliminate cancerous cells, could be an alternative approach to target CSCs. Vaccines of dendritic cells (DCs) loaded with tumor antigens can evoke highly specific anti-tumor T cell responses. Importantly, DC vaccination also promotes immunological memory formation, paving the way for long-term cancer control. Here, we propose a DC vaccination that specifically targets CSCs. DCs loaded with NANOG peptides, a protein required for maintaining stem cell properties, could evoke a potent anti-tumor immune response against CSCs. We hypothesize that the resulting immunological memory will also control newly formed CSCs, thereby preventing disease recurrence.

Prognostic and therapeutic value of CD103+ cells in renal cell carcinoma

Immune checkpoint blockade therapy (ICBT) uses drugs to interrupt signaling pathways that inhibit antitumor immune responses. Although ICBT has provided clinical benefits in certain cancer patients, a large number of patients do not respond to ICBT. Therefore, it is necessary to find other efficient targets to promote the effects of ICBT. Renal cell carcinoma (RCC) is one of the leading causes of cancer-associated mortality worldwide. To date, there is no efficient treatment for patients with advanced RCC. The present study aimed to evaluate the prognostic value of CD103⁺ cells in patients with RCC and their potential role in enhancing the effect of ICBT in RCC. A total of 200 tumor tissue samples were collected from patients with RCC. The CD103⁺ cell count and survival of these patients was assessed, and the role of CD103⁺ cells in combination with ICBT was evaluated in an RCC mouse model. It was identified that a high CD103⁺ cell count was an independent favorable prognosticator in patients with RCC. The expansion of CD103⁺ cells promoted the effects of ICBT in the RCC xenograft mouse model, while depletion of CD103⁺ cells had the opposite effect. Furthermore, the expansion of CD103⁺ cells enhanced the count and activation of tumor infiltrating CD8⁺ T cells in RCC tumor tissue. These results indicate that a high CD103⁺ cell count is an independent favorable prognosticator in RCC patients. Thus, the expansion of CD103⁺ cells may increase the efficacy of ICBT in patients with RCC.

The tumor microenvironment: Thousand obstacles for effector T cells

The immune system is endowed with the capability to recognize and destroy transformed cells, but even in the presence of an immune infiltrate many tumors do progress. In the last decades new discoveries have shed light into (some of) the underlying mechanisms. Immune effector cells are not only under the influence of immune suppressive cell subsets, but also intrinsically regulated by immune check point molecules that under physiological condition avoid attach of healthy tissue. Moreover, tumor cells are modifying the surrounding microenvironment through secretion of immune modulators as well as via their own metabolism, thus further impairing the development of immune effector functions. Different approaches are currently being evaluated in the clinic to overcome those regulatory mechanisms and to unleash effector T cells.

Prognostic implications of intratumoral CD103+ tumor-infiltrating lymphocytes in pulmonary squamous cell carcinoma

CD103 is the α_E subunit of α_Eβ₇ integrin that is expressed in tissue-resident memory T cells, where it promotes cytotoxic T cell responses against tumors. However, little is known about its expression or clinicopathological implications in non-small cell lung cancer (NSCLC). This study investigated the prognostic implications of CD103⁺ tumor-infiltrating lymphocytes (TILs) in NSCLC. We established two cohorts: patients with resected NSCLC (n = 132) and patients with pulmonary squamous cell carcinoma (pSCC), a subset of NSCLC (n = 378), to estimate the prognostic significance of CD103⁺ TILs. The numbers of CD103⁺ TILs in the intratumoral (i.e., intraepithelial) and stromal regions of NSCLC were estimated using immunohistochemistry and automated image analysis. In the NSCLC cohort, high numbers of intratumoral CD103⁺ TILs were significantly associated with prolonged disease-free survival (DFS) and overall survival (OS) in patients with pSCC but not in those with pulmonary adenocarcinoma. In the pSCC cohort, a positive correlation was observed between the numbers of intratumoral CD103⁺ and CD8⁺ TILs (correlation coefficient = 0.736, P < 0.001). The ratio of intratumoral/stromal CD103⁺ TILs was higher in pSCC with high compared to low E-cadherin expression (P = 0.021). According to Kaplan-Meier analysis, high intratumoral but not stromal CD103⁺ TILs were associated with prolonged DFS and OS in patients with resected pSCC (P = 0.021 and 0.002, respectively). Multivariate analysis revealed that a high number of intratumoral CD103⁺ TILs is an independent predictor of a more favorable DFS (P = 0.021). Thus, a high number of intratumoral CD103⁺ TILs is a favorable prognostic indicator in patients with pSCC.

Tissue-resident memory features are linked to the magnitude of cytotoxic T cell responses in human lung cancer

Therapies that boost the anti-tumor responses of cytotoxic T lymphocytes (CTLs) have shown promise; however, clinical responses to the immunotherapeutic agents currently available vary considerably, and the molecular basis of this is unclear. We performed transcriptomic profiling of tumor-infiltrating CTLs from treatment-naive patients with lung cancer to define the molecular features associated with the robustness of anti-tumor immune responses. We observed considerable heterogeneity in the expression of molecules associated with activation of the T cell antigen receptor (TCR) and of immunological-checkpoint molecules such as 4-1BB, PD-1 and TIM-3. Tumors with a high density of CTLs showed enrichment for transcripts linked to tissue-resident memory cells (TRM cells), such as CD103, and CTLs from CD103hi tumors displayed features of enhanced cytotoxicity. A greater density of TRM cells in tumors was predictive of a better survival outcome in lung cancer, and this effect was independent of that conferred by CTL density. Here we define the 'molecular fingerprint' of tumor-infiltrating CTLs and identify potentially new targets for immunotherapy.

Combined Immunoscore of CD103 and CD3 Identifies Long-Term Survivors in High-Grade Serous Ovarian Cancer

OBJECTIVE

Increased numbers of tumor-infiltrating lymphocytes (TILs) in high-grade serous ovarian cancer (HGSC) are associated with improved clinical outcome. Intraepithelial localization of TILs might be regulated by specific homing receptors, such as CD103, which is widely expressed by intraepithelial lymphocytes. Given the emerging role of CD103 TILs, we aimed to assess their contribution to the prognostic value of immunoscoring in HGSC.

METHODS

The density of intratumoral CD3 and CD103 lymphocytes was examined by immunohistochemistry on a tissue microarray of a series of 135 patients with advanced HGSC and correlated with CD4, CD8, CD56, FoxP3, and TCRγ T-cell counts, as well as E-cadherin staining and conventional prognostic parameters and clinical outcome.

RESULTS

Both the presence of CD103 cells, as well as high numbers of intraepithelial CD3 lymphocytes (CD3E), showed a significant correlation with overall survival, in the complete series, as well as in patients with optimal debulking and/or platinum sensitivity. Combining CD3 and CD103 counts improved prognostication and identified 3 major subgroups with respect to overall survival. The most pronounced effect was demonstrated for patients with optimally resected and platinum-sensitive tumors. Patients with CD3/CD103 tumors showed a 5-year survival rate at 90%, CD3/CD103 at 63%, and CD3/CD103 at 0% (P < 0.001).

CONCLUSIONS

These results suggest that combined assessment of CD103 and CD3 counts improves the prognostic value of TIL counts in HGSC and might identify patients with early relapse or long-term survival based on the type and extent of the immune response.

Dasatinib Changes Immune Cell Profiles Concomitant with Reduced Tumor Growth in Several Murine Solid Tumor Models

Dasatinib, a broad-range tyrosine kinase inhibitor, induces rapid mobilization of lymphocytes and clonal expansion of cytotoxic cells in leukemia patients. Here, we investigated whether dasatinib could induce beneficial immunomodulatory effects in solid tumor models. The effects on tumor growth and on the immune system were studied in four different syngeneic mouse models (B16.OVA melanoma, 1956 sarcoma, MC38 colon, and 4T1 breast carcinoma). Both peripheral blood (PB) and tumor samples were immunophenotyped during treatment. Although in vitro dasatinib displayed no direct cytotoxicity to B16 melanoma cells, a significant decrease in tumor growth was observed in dasatinib-treated mice compared with vehicle-treated group. Further, dasatinib-treated melanoma-bearing mice had an increased proportion of CD8⁺ T cells in PB, together with a higher amount of tumor-infiltrating CD8⁺ T cells. Dasatinib-mediated antitumor efficacy was abolished when CD4⁺ and CD8⁺ T cells were depleted with antibodies. Results were confirmed in sarcoma, colon, and breast cancer models, and in all cases mice treated daily with dasatinib had a significant decrease in tumor growth. Detailed immunophenotyping of tumor tissues with CyTOF indicated that dasatinib had reduced the number of intratumoral regulatory T cells in all tumor types. To conclude, dasatinib is able to slow down the tumor growth of various solid tumor models, which is associated with the favorable blood/tumor T-cell immunomodulation. The assessment of synergistic combinatorial therapies with other immunomodulatory drugs or targeted small-molecule oncokinase inhibitors is warranted in future clinical trials. Cancer Immunol Res; 5(2); 157-69. ©2017 AACR.

IL-27 induces the expression of IDO and PD-L1 in human cancer cells

IL-27 is a member of the IL-12 family that is produced by macrophages and dendritic cells. IL-27 inhibits the growth and invasiveness of different cancers and therefore represents a potential anti-tumor agent. By contrast, it may exert immune-regulatory properties in different biological systems. We reported that IL-27 induces the expression of the IL-18 inhibitor IL-18BP, in human Epithelial Ovarian Cancer (EOC) cells, thus potentially limiting the immune response. Here, we tested whether IL-27 may modulate other immune-regulatory molecules involved in EOC progression, including Indoleamine 2,3-dioxygenase (IDO) and Programmed Death-Ligand (PD-L)1. IDO and PD-L1 were not constitutively expressed by EOC cells in vitro, but IL-27 increased their expression through STAT1 and STAT3 tyrosine phosphorylation. Differently, cells isolated from EOC ascites showed constitutive activation of STAT1 and STAT3 and IDO expression. These findings, together with the expression of IL-27 in scattered leukocytes in EOC ascites and tissues, suggest a potential role of IL-27 in immune-regulatory networks of EOC. In addition, IL-27 induced IDO or PD-L1 expression in monocytes and in human PC3 prostate and A549 lung cancer cells. A current paradigm in tumor immunology is that tumor cells may escape from immune control due to “adaptive resistance” mediated by T cell-secreted IFN-γ, which induces PD-L1 and IDO expression in tumor cells. Our present data indicate that also IL-27 has similar activities and suggest that the therapeutic use of IL-27 as anti-cancer agent may have dual effects, in some tumors.

[Immunological aspects of ovarian cancer: Therapeutic perspectives]

Ovarian cancer is recognized by the immunological system of its host. Initially, it is effective to destroy and eliminate the cancer. But gradually, resistant tumor cells more aggressive and those able to protect themselves by inducing immune tolerance will be selected. Immunotherapy to be effective should consider both components of immune response with an action on cytotoxic immune effectors and action on tolerance mechanisms. The manipulations of the immune system should be cautious, because the immune effects are not isolated. A theoretically efficient handling may simultaneously cause an adverse effect which was not envisaged and could neutralize the benefits of treatment. Knowledge of tolerance mechanisms set up by the tumor is for the clinician a prerequisite before they prescribe these treatments. For each cancer, the knowledge of its immunological status is a prerequisite to propose adapted immunological therapies.

CD103 and Intratumoral Immune Response in Breast Cancer

PURPOSE

CD103 is expressed in several immune cell types but in the context of the intratumoral immune response may be most important as a marker of antigen-activated CD8 T cells.

METHODS

We have examined the prognostic significance of CD103 TILs in breast cancer by IHC in a cohort of 424 breast cancer patients.

RESULTS

CD103 TILs were present in all subtypes but were more abundant in ER-negative tumors where CD103 TILs were preferentially localized to the intraepithelial compartment. CD103 was associated with tumor size, tumor grade, and ER/PR status (P < 0.05). CD103 TIL density and the epithelial to stromal ratio was highest in the basal-like tumors. Intraepithelial CD103 but not intrastromal CD103 was associated with better relapse-free and overall survival in basal-like subtype tumors [HR = 0.28; 95% confidence interval (CI), 0.17-0.72; P = 0.0047 and HR = 0.25; 95% CI, 0.17-0.66; P = 0.0017, respectively). CD8 status showed similar but less significant associations, but the combination of dual CD103⁺CD8⁺ TIL status was the most strongly prognostic combination for relapse-free and overall survival (HR = 0.10; 95% CI, 0.07-0.62; P = 0.006 and HR = 0.09; 95% CI, 0.07-0.57; P = 0.003, respectively).

CONCLUSIONS

CD103 TILs are indicative of a good prognosis specifically within the basal-like subtype of breast cancer. Clin Cancer Res; 22(24); 6290-7. ©2016 AACR.

Bone Marrow T Cells and the Integrated Functions of Recirculating and Tissue-Resident Memory T Cells

Changes in T cell trafficking accompany the naive to memory T cell antigen-driven differentiation, which remains an incompletely defined developmental step. Upon priming, each naive T cell encounters essential signals – i.e., antigen, co-stimuli and cytokines – in a secondary lymphoid organ; nevertheless, its daughter effector and memory T cells recirculate and receive further signals during their migration through various lymphoid and non-lymphoid organs. These additional signals from tissue microenvironments have an impact on immune response features, including T cell effector function, expansion and contraction, memory differentiation, long-term maintenance, and recruitment upon antigenic rechallenge into local and/or systemic responses. The critical role of T cell trafficking in providing efficient T cell memory has long been a focus of interest. It is now well recognized that naive and memory T cells have different migratory pathways, and that memory T cells are heterogeneous with respect to their trafficking. We and others have observed that, long time after priming, memory T cells are preferentially found in certain niches such as the bone marrow (BM) or at the skin/mucosal site of pathogen entry, even in the absence of residual antigen. The different underlying mechanisms and peculiarities of resulting immunity are currently under study. In this review, we summarize key findings on BM and tissue-resident memory (TRM) T cells and revisit some issues in memory T cell maintenance within such niches. Moreover, we discuss BM seeding by memory T cells in the context of migration patterns and protective functions of either recirculating or TRM T cells.

Prognosis after recurrence of hepatocellular carcinoma in liver transplantation: predictors for successful treatment and survival

There are no established prognostic factors or standardized therapies for hepatocellular carcinoma (HCC) recurrence in liver transplantation (LT). The aim of this study was to investigate impact of underlying patient condition on treatment and outcomes of recurrence of HCC after LT. The medical records of 268 LT patients with HCC were evaluated. Potential prognostic factors for survival after recurrence were evaluated, including recurrent tumor characteristics, medical/radiological/surgical therapies for recurrence, and an inflammatory marker (neutrophil/lymphocyte ratio). Laboratory tests at recurrence, including albumin, absolute lymphocyte count (ALC), prognostic nutritional index (PNI: ALC(/μL) × 0.005 + Albumin(g/dL) × 10), were evaluated as surrogate markers for underlying patient conditions. A total of 51 (19%) patients developed HCC recurrence. The use of sirolimus and sorafenib significantly improved outcome (p = 0.007 and 0.04), and better nutritional status (PNI ≥ 40) enhanced their efficacy. On multivariate analysis, low ALC (<500/μL) and albumin (<2.8 g/L) remained independent prognostic factors (p = 0.03 and 0.02; hazard ratio = 3.61 [Ref. >1000/μL] and 4.97 [Ref. >3.5 g/dL], respectively). Low PNI (<40) showed significantly lower survival rate after adjusting the risk (p = 0.006, hazard ratio = 3.29). Underlying patient conditions and nutritional status, represented by ALC and albumin, are important to successful cancer treatment and strong prognostic markers for survival after HCC recurrence.

The emerging role of resident memory T cells in protective immunity and inflammatory disease

Over the past decade, it has become clear that there is an important subset of memory T cells that resides in tissues-tissue-resident memory T (TRM) cells. There is an emerging understanding that TRM cells have a role in human tissue-specific immune and inflammatory diseases. Furthermore, the nature of the molecular signals that maintain TRM cells in tissues is the subject of much investigation. In addition, whereas it is logical for TRM cells to be located in barrier tissues at interfaces with the environment, these cells have also been found in brain, kidney, joint and other non-barrier tissues in humans and mice. Given the biology and behavior of these cells, it is likely that they have a role in chronic relapsing and remitting diseases of both barrier and non-barrier tissues. In this Review we discuss recent insights into the biology of TRM cells with a particular focus on their roles in disease, both proven and putative.

Repeated intratumoral administration of ONCOS-102 leads to systemic antitumor CD8+ T-cell response and robust cellular and transcriptional immune activation at tumor site in a patient with ovarian cancer

Adenoviruses are excellent immunotherapeutic agents with a unique ability to prime and boost immune responses. Recombinant adenoviruses cause immunogenic cancer cell death and subsequent release of tumor antigens for antigen presenting cells, resulting in the priming of potent tumor-specific immunity. This effect may be further enhanced by immune-stimulating transgenes expressed by the virus. We report a case of a 38-year-old female with Stage 3 metastatic micropapillary serous carcinoma of the ovary. She was treated in a Phase I study with a granulocyte-macrophage colony stimulating factor (GMCSF)-expressing oncolytic adenovirus, Ad5/3-D24-GMCSF (ONCOS-102). The treatment resulted in progressive infiltration of CD8⁺ lymphocytes into the tumor and concomitant systemic induction of several tumor-specific CD8⁺ T-cell populations. The patient was alive at the latest follow up more than 20 months after initiation of the study.

Cytomegalovirus-Based Vaccine Expressing a Modified Tumor Antigen Induces Potent Tumor-Specific CD8(+) T-cell Response and Protects Mice from Melanoma

The presence of tumor-infiltrating CD8(+) T cells is associated with tumor regression and better prognosis. Cytomegalovirus (CMV) infection elicits a robust and long-lasting CD8(+) T-cell response, which makes CMV a potentially promising vaccine vector against cancer. In the current study, we used recombinant murine CMV (MCMV) strains as prophylactic and therapeutic vaccines in an aggressive B16 lung metastatic melanoma model. Immunization with MCMV-expressing ovalbumin (OVA) induced a potent OVA-specific CD8(+) T-cell response and was effective in protecting mice from OVA-expressing B16 melanoma in an antigen-dependent manner. We engineered MCMV to express a modified B16 melanoma antigen gp100 (MCMV-gp100KGP). Immunization with MCMV-gp100KGP was highly effective in overcoming immune tolerance to self-antigen and induced a strong, long-lasting gp100-specific CD8(+) T-cell response even in the presence of preexisting anti-CMV immunity. Furthermore, both prophylactic and therapeutic vaccinations of mice with MCMV-gp100KGP effectively protected mice from highly aggressive lung B16-F10 melanoma, and the protection was mediated by gp100-specific CD8(+) T cells. We showed that MCMV is a superior vaccine vector compared with a commonly used vesicular stomatitis virus vector. Collectively, our studies demonstrate that CMV is a promising vaccine vector to prevent and treat tumors.