Induction of resident memory T cells enhances the efficacy of cancer vaccine

Tissue-Resident Memory CD8+ T Cells: From Phenotype to Function

Tissue-resident memory CD8⁺ T cells are an important first line of defense from infection in peripheral non-lymphoid tissues, such as the mucosal tissues of the respiratory, digestive, and urogenital tracts. This memory T cell subset is established late during resolution of primary infection of those tissues, has a distinct genetic signature, and is often defined by the cell surface expression of CD69, CD103, CD49a, and CD44 in both mouse and human studies. The stimuli that program or imprint the unique gene expression and cell surface phenotypes on T_RM are beginning to be defined, but much work remains to be done. It is not clear, for example, when and where the T_RM precursors receive these signals, and there is evidence that supports imprinting in both the lymph node and the peripheral tissue sites. In most studies, expression of CD49a, CD103, and CD69 on T cells in the tissues appears relatively late in the response, suggesting there are precise environmental cues that are not present at the height of the acute response. CD49a and CD103 are not merely biomarkers of T_RM, they confer substrate specificities for cell adhesion to collagen and E-cadherin, respectively. Yet, little attention has been paid to how expression affects the positioning of T_RM in the peripheral tissues. CD103 and CD49a are not mutually exclusive, and not always co-expressed, although whether they can compensate for one another is unknown. In fact, they may define different subsets of T_RM in certain tissues. For instance, while CD49a⁺CD8⁺ memory T cells can be found in almost all peripheral tissues, CD103 appears to be more restricted. In this review, we discuss the evidence for how these hallmarks of T_RM affect positioning of T cells in peripheral sites, how CD49a and CD103 differ in expression and function, and why they are important for immune protection conferred by T_RM in mucosal tissues such as the respiratory tract.

[Tim-3: a novel biomarker and therapeutic target in oncology]

T cells harboring multiple co-inhibitory molecules lose their anti-tumoral functionality. PD-1 is a clinically approved target in cancer therapy, but its expression alone does not mean dysfunctionality. The expression of Tim-3 on numerous cell types (T cell, Treg, dendritic cell, myeloid cells) favors tumor escape to immune cells. Within many tumors, PD-1/Tim-3 coexpressing CD8-T cells lose their ability to secrete cytokines (IFNγ, IL-2, TNFα) and their intratumoral infiltration correlates with a bad prognosis. Tim-3 recently appeared as a potential biomarker of anti-PD-1 resistance. Combined blockade of PD-1 and Tim-3 axis demonstrated potent clinical efficacy in preclinical models and reinforced the rationale of using an anti-Tim-3 to override tumor resistance.

Immunotherapy in head and neck cancers: A new challenge for immunologists, pathologists and clinicians

Cancer occurrence can be understood as the result of dysfunctions in immune tumoral microenvironment. Here we review the recent understandings of those microenvironment changes, regarding their causes and prognostic significance in head and neck (HN) carcinoma. We will focus on HN squamous cell cancer (SCC) and nasopharyngeal carcinomas (NPC). Their overall poor prognosis may be improved with immunotherapy in a subset of patients, as supported by current clinical trials. However, finding reliable markers of therapeutic response is crucial for patient selection, due to potential severe adverse reactions and high costs. Half of HNSCC exhibit PD-L1 expression, this expression being higher in HPV-positive tumors. In recent clinical trials, a better therapeutic response to anti-PD-1 was obtained in patients with higher PD-L1 expression. The Food and Drug Administration (FDA) approved the use of these therapeutics without stating a need for patient selection regarding PD-L1 status. Activation status, density and localization of TIL as well as PD-L2, γ-interferon, inflammatory cytokines, epithelial-mesenchymal transition phenotype and mutational burden may all be potential therapeutic response markers. In Epstein-Barr Virus (EBV)-induced nasopharyngeal non-keratinizing cancer, PD-L1 is over-expressed compared to EBV-negative tumors. A 22% response rate has been observed under anti-PD-1 treatment among PD-L1-positive NPC patients. A better understanding of immune checkpoint regulation processes may allow patients to benefit from these promising immunotherapies.

Multiplexed Immunofluorescence Analysis and Quantification of Intratumoral PD-1+ Tim-3+ CD8+ T Cells

Immune cells are important components of the tumor microenvironment and influence tumor growth and evolution at all stages of carcinogenesis. Notably, it is now well established that the immune infiltrate in human tumors can correlate with prognosis and response to therapy. The analysis of the immune infiltrate in the tumor microenvironment has become a major challenge for the classification of patients and the response to treatment. The co-expression of inhibitory receptors such as Program Cell Death Protein 1 (PD1; also known as CD279), Cytotoxic T Lymphocyte Associated Protein 4 (CTLA-4), T-Cell Immunoglobulin and Mucin Containing Protein-3 (Tim-3; also known as CD366), and Lymphocyte Activation Gene 3 (Lag-3; also known as CD223), is a hallmark of T cell exhaustion. We developed a multiparametric in situ immunofluorescence staining to identify and quantify at the cellular level the co-expression of these inhibitory receptors. On a retrospective series of frozen tissue of renal cell carcinomas (RCC), using a fluorescence multispectral imaging technology coupled with an image analysis software, it was found that co-expression of PD-1 and Tim-3 on tumor infiltrating CD8⁺ T cells is correlated with a poor prognosis in RCC. To our knowledge, this represents the first study demonstrating that this automated multiplex in situ technology may have some clinical relevance.

[Anti-cancer vaccines: What future in anti-cancer immunotherapy strategies?]

Tumor cells can be recognized by the immune system and in particular by cytotoxic CD8⁺T cells. From this observation was derived the concept that vaccination targeting these tumor-associated molecules was feasible. Preventive cancer vaccines targeting oncogenic papillomavirus or hepatitis B virus do exist and are efficient. They aim at preventing the introduction into the body of viruses that play a role in oncogenesis. To date, in the case of an already grown cancer, the anti-tumor vaccines have had no impact on the care of patients. These vaccines are gaining renewed interest, as new antigenic targets have emerged and have been incorporated into the design of vaccines, such as mutated antigens which appeared to be more immunogenic. Less editing cells than tumor cells in the tumor microenvironment, such as protumor endothelial cells or fibroblasts, could also be eliminated by cancer vaccines. New vaccine efficacy criteria have been identified, such as the need to induce intratumoral resident T lymphocytes thanks to the development of mucosal vaccination to amplify them. Finally, because of the immunosuppression of the tumor microenvironment and the expression of inhibitory receptors on CD8⁺T cells in the tumor, various therapeutic association strategies between the anti-cancer vaccines and molecules supporting these inhibitions are currently used in clinical development. Especially, the efficacy of antibodies against costimulatory inhibitory molecules (PD-1, PD-L1…) relies on the presence of pre-existing CD8⁺T cells occurring in 25-30% of cancer patients. For the 70% resistant patients, cancer vaccine may reprogram this tumor environment via the induction of intratumoral CD8⁺T cells which will very likely counteract this resistance to anti-PD-1/PD-L1 antibodies.

Lack of MHC class II molecules favors CD8+ T-cell infiltration into tumors associated with an increased control of tumor growth

Regulatory T-cells (Tregs) are crucial for the maintenance of immune tolerance and homeostasis as well as for preventing autoimmune diseases, but their impact on the survival of cancer patients remains controversial. In the TC-1 mouse model of human papillomavirus (HPV)-related carcinoma, we have previously demonstrated that the therapeutic efficacy of the CyaA-E7-vaccine, targeting the HPV-E7 antigen, progressively declines with tumor growth, in correlation with increased intratumoral recruitment of Tregs. In the present study, we demonstrated that these TC-1 tumor-infiltrating Tregs were highly activated, with increased expression of immunosuppressive molecules. Both intratumoral effector CD4⁺ T-cells (Teffs) and Tregs expressed high levels of PD-1, but anti-PD-1 antibody treatment did not impact the growth of the TC-1 tumor nor restore the therapeutic effect of the CyaA-E7 vaccine. To analyze the mechanisms by which Tregs are recruited to the tumor site, we used MHC-II KO mice with drastically reduced numbers of CD4⁺ effector T-cells. We demonstrated that these mice still had significant numbers of Tregs in their lymphoid organs which were recruited to the tumor. In MHC-II KO mice, the growth of the TC-1 tumor was delayed in correlation with a strong increase in the intratumoral recruitment of CD8⁺ T-cells. In addition, in mice that spontaneously rejected their tumors, the infiltration of E7-specific CD8⁺ T-cells was significantly higher than in MHC-II KO mice with a growing tumor. These results demonstrate that tumor-specific CD8⁺ T-cells can be efficiently activated and recruited in the absence of MHC class II molecules and of CD4⁺ T-cell help.

Tissue-resident memory T cells play a key role in the efficacy of cancer vaccines

Resident memory CD8⁺T cells (T_RM) usually defined by the CD103 marker represent a new subset of long-lived memory T cells that remain in the tissues. We directly demonstrate their specific role in cancer vaccine-induced tumor regression. In human, they also seem to play a major role in tumor immunosurveillance.

TNF-receptor superfamily agonists as molecular adjuvants for cancer vaccines

Cancer vaccines have offered unrequited hope as a mechanism for rapidly and potently eliciting a patient's immune system to counter tumors. Initial results from preclinical mouse models have not translated to substantial benefit to patients, suggesting that either the targets or the vaccination approach were inadequate. Recent innovations in antigen identification have spiked renewed interest vaccination technologies. This has coincided with a detailed molecular understanding of the coordinated steps in postactivation support of T cell proliferation, differentiation and survival, leading to the development of novel targets and combinations that are substantially more effective than first and second generation cancer vaccines in preclinical models. Within this cluster of developments, the TNF-receptor superfamily members have emerged as attractive candidates for clinical implementation. Here we review recent developments in the mechanisms of action of TNFRSF agonists, and how their activity is potentiated by integration co-targeting pattern recognition receptors.

Mechanisms of action and rationale for the use of checkpoint inhibitors in cancer

The large family of costimulatory molecules plays a crucial role in regulation of the immune response. These molecules modulate TCR signalling via phosphorylation cascades. Some of the coinhibitory members of this family, such as PD-1 and CTLA-4, already constitute approved targets in cancer therapy and, since 2011, have opened a new area of antitumour immunotherapy. Many antibodies targeting other inhibitory receptors (Tim-3, VISTA, Lag-3 and so on) or activating costimulatory molecules (OX40, GITR and so on) are under evaluation. These antibodies have multiple mechanisms of action. At the cellular level, these antibodies restore the activation signalling pathway and reprogram T cell metabolism. Tumour cells become resistant to apoptosis when an intracellular PD-L1 signalling is blocked. CD8⁺ T cells are considered to be the main effectors of the blockade of inhibitory receptors. Certain CD8⁺ T cell subsets, such as non-hyperexhausted (CD28⁺, T-bet^high, PD-1^int), follicular-like (CXCR-5⁺) or resident memory CD8⁺ T cells, are more prone to be reactivated by anti-PD-1/PD-L1 monoclonal antibody (mAb). In the future, the challenge will be to rationally combine drugs able to make the tumour microenvironment more permissive to immunotherapy in order to potentiate its clinical activity.