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

ImmunoPET provides a novel way to visualize the CD103+ tissue-resident memory T cell to predict the response of immune checkpoint inhibitors

BACKGROUND

Immune checkpoint inhibitors (ICIs) have made significant progress in oncotherapy improving survival of patients. However, the benefits are limited to only a small subgroup of patients who could achieve durable responses. Early prediction of response may enable treatment optimization and patient stratification. Therefore, developing appropriate biomarkers is critical to monitoring efficacy and assessing patient response to ICIs.

MAIN BODY

Herein, we first introduce a new potential biomarker, CD103, expressed on tissue-resident memory T cells, and discuss the potential application of CD103 PET imaging in predicting immune checkpoint inhibitor treatment. In addition, we describe the current targets of ImmunoPET and compare these targets with CD103. To assess the benefit of PET imaging, a comparative analysis between ImmunoPET and other imaging techniques commonly employed for tumor diagnosis was performed. Additionally, we compare ImmunoPET and immunohistochemistry (IHC), a widely utilized clinical method for biomarker identification with respect to visualizing the immune targets.

CONCLUSION

CD103 ImmunoPET is a promising method for determining tumor-infiltrating lymphocytes (TILs) load and response to ICIs, thereby addressing the lack of reliable biomarkers in cancer immunotherapy. Compared to general T cell markers, CD103 is a specific marker for tissue-resident memory T cells, which number increases during successful ICI therapy. ImmunoPET offers noninvasive, dynamic imaging of specific markers, complemented by detailed molecular information from immunohistochemistry (IHC). Radiomics can extract quantitative features from traditional imaging methods, while near-infrared fluorescence (NIRF) imaging aids tumor detection during surgery. In the era of precision medicine, combining such methods will offer a more comprehensive approach to cancer diagnosis and treatment.

Development of [89Zr]Zr-hCD103.Fab01A and [68Ga]Ga-hCD103.Fab01A for PET imaging to noninvasively assess cancer reactive T cell infiltration: Fab-based CD103 immunoPET

BACKGROUND

CD103 is an integrin specifically expressed on the surface of cancer-reactive T cells. The number of CD103+ T cells significantly increases during successful immunotherapy and might therefore be an attractive biomarker for noninvasive PET imaging of immunotherapy response. Since the long half-life of antibodies preclude repeat imaging of CD103+ T cell dynamics early in therapy, we therefore here explored PET imaging with CD103 Fab fragments radiolabeled with a longer (89Zr) and shorter-lived radionuclide (68Ga).

METHODS

Antihuman CD103 Fab fragment Fab01A was radiolabeled with 89Zr or 68Ga, generating [89Zr]Zr-hCD103.Fab01A and [68Ga]Ga-hCD103.Fab01A, respectively. In vivo evaluation of these tracers was performed in male nude mice (BALB/cOlaHsd-Foxn1nu) with established CD103-expressing CHO (CHO.CD103) or CHO-wildtype (CHO.K1) xenografts, followed by serial PET imaging and ex vivo bio-distribution.

RESULTS

[89Zr]Zr-hCD103.Fab01A showed high tracer uptake in CD103+ xenografts as early as 3 h post-injection. However, the background signal remained high in the 3- and 6-h scans. The background was relatively low at 24 h after injection with sufficient tumor uptake. [68Ga]Ga-hCD103.Fab01Ashowed acceptable uptake and signal-to-noise ratio in CD103+ xenografts after 3 h, which decreased at subsequent time points.

CONCLUSION

[89Zr]Zr-hCD103.Fab01A demonstrated a relatively low background and high xenograft uptake in scans as early as 6 h post-injection and could be explored for repeat imaging during immunotherapy in clinical trials. 18F or 64Cu could be explored as alternative to 68Ga in optimizing half-life and radiation burden of the tracer.

Mouse Memory CD8 T Cell Subsets Defined by Tissue-Resident Memory Integrin Expression Exhibit Distinct Metabolic Profiles

Tissue-resident memory CD8 T cells (TRM) principally reside in peripheral nonlymphoid tissues, such as lung and skin, and confer protection against a variety of illnesses ranging from infections to cancers. The functions of different memory CD8 T cell subsets have been linked with distinct metabolic pathways and differ from other CD8 T cell subsets. For example, skin-derived memory T cells undergo fatty acid oxidation and oxidative phosphorylation to a greater degree than circulating memory and naive cells. Lung TRMs defined by the cell-surface expression of integrins exist as distinct subsets that differ in gene expression and function. We hypothesize that TRM subsets with different integrin profiles will use unique metabolic programs. To test this, differential expression and pathway analysis were conducted on RNA sequencing datasets from mouse lung TRMs yielding significant differences related to metabolism. Next, metabolic models were constructed, and the predictions were interrogated using functional metabolite uptake assays. The levels of oxidative phosphorylation, mitochondrial mass, and neutral lipids were measured. Furthermore, to investigate the potential relationships to TRM development, T cell differentiation studies were conducted in vitro with varying concentrations of metabolites. These demonstrated that lipid conditions impact T cell survival, and that glucose concentration impacts the expression of canonical TRM marker CD49a, with no effect on central memory-like T cell marker CCR7. In summary, it is demonstrated that mouse resident memory T cell subsets defined by integrin expression in the lung have unique metabolic profiles, and that nutrient abundance can alter differentiation.

Mechanisms of response and resistance to combined decitabine and ipilimumab for advanced myeloid disease

The challenge of eradicating leukemia in patients with acute myelogenous leukemia (AML) after initial cytoreduction has motivated modern efforts to combine synergistic active modalities including immunotherapy. Recently, the ETCTN/CTEP 10026 study tested the combination of the DNA methyltransferase inhibitor decitabine together with the immune checkpoint inhibitor ipilimumab for AML/myelodysplastic syndrome (MDS) either after allogeneic hematopoietic stem cell transplantation (HSCT) or in the HSCT-naïve setting. Integrative transcriptome-based analysis of 304 961 individual marrow-infiltrating cells for 18 of 48 subjects treated on study revealed the strong association of response with a high baseline ratio of T to AML cells. Clinical responses were predominantly driven by decitabine-induced cytoreduction. Evidence of immune activation was only apparent after ipilimumab exposure, which altered CD4+ T-cell gene expression, in line with ongoing T-cell differentiation and increased frequency of marrow-infiltrating regulatory T cells. For post-HSCT samples, relapse could be attributed to insufficient clearing of malignant clones in progenitor cell populations. In contrast to AML/MDS bone marrow, the transcriptomes of leukemia cutis samples from patients with durable remission after ipilimumab monotherapy showed evidence of increased infiltration with antigen-experienced resident memory T cells and higher expression of CTLA-4 and FOXP3. Altogether, activity of combined decitabine and ipilimumab is impacted by cellular expression states within the microenvironmental niche of leukemic cells. The inadequate elimination of leukemic progenitors mandates urgent development of novel approaches for targeting these cell populations to generate long-lasting responses. This trial was registered at www.clinicaltrials.gov as #NCT02890329.

CagA-specific Gastric CD8+ Tissue-Resident T Cells Control Helicobacter pylori During the Early Infection Phase

BACKGROUND & AIMS

Infection with Helicobacter pylori strongly affects global health by causing chronic gastritis, ulcer disease, and gastric cancer. Although extensive research into the strong immune response against this persistently colonizing bacterium exists, the specific role of CD8⁺ T cells remains elusive.

METHODS

We comprehensively characterize gastric H pylori-specific CD8⁺ T-cell responses in mice and humans by flow cytometry, RNA-sequencing, immunohistochemistry, and ChipCytometry, applying functional analyses including T-cell depletion, H pylori eradication, and ex vivo restimulation.

RESULTS

We define CD8⁺ T-cell populations bearing a tissue-resident memory (T_RM) phenotype, which infiltrate the gastric mucosa shortly after infection and mediate pathogen control by executing antigen-specific effector properties. These induced CD8⁺ tissue-resident memory T cells (T_RM cells) show a skewed T-cell receptor beta chain usage and are mostly specific for cytotoxin-associated gene A, the distinctive oncoprotein injected by H pylori into host cells. As the infection progresses, we observe a loss of the T_RM phenotype and replacement of CD8⁺ by CD4⁺ T cells, indicating a shift in the immune response during the chronic infection phase.

CONCLUSIONS

Our results point toward a hitherto unknown role of CD8⁺ T-cell response in this bacterial infection, which may have important clinical implications for treatment and vaccination strategies against H pylori.

[Tumor-infiltrating natural killer and T cells in melanoma]

Melanoma is a highly immunogenic cancer with an increased infiltration of lymphocytes (TIL). TIL are a very heterogeneous population which consists among others of CD8+ T cells, CD4+ T cells, regulatory T cells, B cells, and natural killer (NK) cells and may differ highly between melanoma patients. Distribution, concentration, phenotype, and activation status of the infiltrating lymphocytes vary greatly and impact the prognosis. Different subpopulations of CD8+ T cells, CD4+ T cells, and NK cells have been identified and have been associated with both the course of the disease and the therapeutic response to different therapies. Increased knowledge of the different functions, interactions, activation, and possibilities of actively influencing relevant subgroups may lead to novel, innovative, and promising therapeutic options.

Altered immunity to microbiota, B cell activation and depleted γδ/resident memory T cells in colorectal cancer

The role of microbiota:immune system dysregulation in the etiology of colorectal cancer (CRC) is poorly understood. CRC develops in gut epithelium, accompanied by low level inflammatory signaling, intestinal microbial dysbiosis and immune dysfunction. We examined populations of intraepithelial lymphocytes in non-affected colonic mucosa of CRC and healthy donors and circulating immune memory to commensal bacterial species and yeasts. γδ T cells and resident memory T cells, populations with a regulatory CD39-expressing phenotype, were found at lower frequencies in the colonic tissue of CRC donors compared to healthy controls. Patterns of T cell proliferative responses to a panel of commensal bacteria were distinct in CRC, while B cell memory responses to several bacteria/yeast were significantly increased, accompanied by increased proportions of effector memory B cells, transitional B cells and plasmablasts in blood. IgA responses to mucosal microbes were unchanged. Our data describe a novel immune signature with similarities to and differences from that of inflammatory bowel disease. They implicate B cell dysregulation as a potential contributor to parainflammation and identify pathways of weakened barrier function and tumor surveillance in CRC-susceptible individuals.

Altered immunity to microbiota, B cell activation and depleted γδ/resident memory T cells in colorectal cancer

The role of microbiota:immune system dysregulation in the etiology of colorectal cancer (CRC) is poorly understood. CRC develops in gut epithelium, accompanied by low level inflammatory signaling, intestinal microbial dysbiosis and immune dysfunction. We examined populations of intraepithelial lymphocytes in non-affected colonic mucosa of CRC and healthy donors and circulating immune memory to commensal bacterial species and yeasts. γδ T cells and resident memory T cells, populations with a regulatory CD39-expressing phenotype, were found at lower frequencies in the colonic tissue of CRC donors compared to healthy controls. Patterns of T cell proliferative responses to a panel of commensal bacteria were distinct in CRC, while B cell memory responses to several bacteria/yeast were significantly increased, accompanied by increased proportions of effector memory B cells, transitional B cells and plasmablasts in blood. IgA responses to mucosal microbes were unchanged. Our data describe a novel immune signature with similarities to and differences from that of inflammatory bowel disease. They implicate B cell dysregulation as a potential contributor to parainflammation and identify pathways of weakened barrier function and tumor surveillance in CRC-susceptible individuals.

Changes in the Immune Cell Repertoire for the Treatment of Malignant Melanoma

Immune checkpoint inhibitors (ICIs) have been used for the treatment of various types of cancers, including malignant melanoma. Mechanistic exploration of tumor immune responses is essential to improve the therapeutic efficacy of ICIs. Since tumor immune responses are based on antigen-specific immune responses, investigators have focused on T cell receptors (TCRs) and have analyzed changes in the TCR repertoire. The proliferation of T cell clones against tumor antigens is detected in patients who respond to treatment with ICIs. The proliferation of these T cell clones is observed within tumors as well as in the peripheral blood. Clonal proliferation has been detected not only in CD8-positive T cells but also in CD4-positive T cells, resident memory T cells, and B cells. Moreover, changes in the repertoire at an early stage of treatment seem to be useful for predicting the therapeutic efficacy of ICIs. Further analyses of the repertoire of immune cells are desirable to improve and predict the therapeutic efficacy of ICIs.

Why do tumor-infiltrating lymphocytes have variable efficacy in the treatment of solid tumors?

Lymphocytes in tumor tissue are called tumor-infiltrating lymphocytes (TILs), and they play a key role in the control and treatment of tumor diseases. Since the discovery in 1987 that cultured TILs can kill tumor cells more than 100 times more effectively than T-cells cultured from peripheral blood in melanoma, it has been confirmed that cultured TILs can successfully cure clinical patients with melanoma. Since 1989, after we investigated TIL isolation performance from solid tumors, we modified some procedures to increase efficacy, and thus successfully established new TIL isolation and culture methods in 1994. Moreover, our laboratory and clinicians using our cultured TILs have published more than 30 papers. To improve the efficacy of TILs, we have been carrying out studies of TIL efficacy to treat solid tumor diseases for approximately 30 years. The three main questions of TIL study have been "How do TILs remain silent in solid tumor tissue?", "How do TILs attack homologous and heterologous antigens from tumor cells of solid tumors?", and "How do TILs infiltrate solid tumor tissue from a distance into tumor sites to kill tumor cells?". Research on these three issues has increasingly answered these questions. In this review I summarize the main issues surrounding TILs in treating solid tumors. This review aims to study the killing function of TILs from solid tumor tissues, thereby ultimately introducing the optimal strategy for patients suffering from solid tumors through personalized immunotherapy in the near future.

Tumor microenvironment shows an immunological abscopal effect in patients with NSCLC treated with pembrolizumab-radiotherapy combination

Background

Immunotherapy is currently part of the standard of care for patients with advanced-stage non-small cell lung cancer (NSCLC). However, many patients do not respond to this treatment, therefore combination strategies are being explored to increase clinical benefit. The PEMBRO-RT trial combined the therapeutic programmed cell death 1 (PD-1) antibody pembrolizumab with stereotactic body radiation therapy (SBRT) to increase the overall response rate and study the effects on the tumor microenvironment (TME).

Methods

Here, immune infiltrates in the TME of patients included in the PEMBRO-RT trial were investigated. Tumor biopsies of patients treated with pembrolizumab alone or combined with SBRT (a biopsy of the non-irradiated site) at baseline and during treatment were stained with multiplex immunofluorescence for CD3, CD8, CD20, CD103 and FoxP3 for lymphocytes, pan-cytokeratin for tumors, and HLA-ABC expression was determined.

Results

The total number of lymphocytes increased significantly after 6 weeks of treatment in the anti-PD-1 group (fold change: 1.87, 95% CI: 1.06 to 3.29) and the anti-PD-1+SBRT group (fold change: 2.29, 95% CI: 1.46 to 3.60). The combination of SBRT and anti-PD-1 induced a 4.87-fold increase (95% CI: 2.45 to 9.68) in CD103⁺ cytotoxic T-cells 6 weeks on treatment and a 2.56-fold increase (95% CI: 1.03 to 6.36) after anti-PD-1 therapy alone. Responders had a significantly higher number of lymphocytes at baseline than non-responders (fold difference 1.85, 95% CI: 1.04 to 3.29 for anti-PD-1 and fold change 1.93, 95% CI: 1.08 to 3.44 for anti-PD-1+SBRT).

Conclusion

This explorative study shows that that lymphocyte infiltration in general, instead of the infiltration of a specific lymphocyte subset, is associated with response to therapy in patients with NSCLC.

Furthermore, anti-PD-1+SBRT combination therapy induces an immunological abscopal effect in the TME represented by a superior infiltration of cytotoxic T cells as compared with anti-PD-1 monotherapy.

Tumor infiltrating lymphocytes (TILs) as a predictive biomarker of response to checkpoint blockers in solid tumors: a systematic review

Immunotherapy is a standard of care in many solid tumors but many patients derive limited benefit from it. There is increasing interest toward tumor infiltrating lymphocytes (TILs) since their presence may be related with good outcomes from treatment with immune checkpoint blockers. We aimed at systematically reviewing existing evidence about the role of TILs as possible predictors of response to immunotherapy in solid tumors. We reviewed 1193 records published from January 2010 until December 2021. Associations between TILs and outcomes were observed mainly in melanoma and breast cancer. Overall survival and overall response rate for advanced disease and pathological complete response for early-phase tumors were the most commonly assessed endpoints. No definitive conclusion can be drawn on the predictive role of TILs. Additional studies, exploiting data from prospective, randomized clinical trials should further evaluate TILs also with the aim of identifying standard cut-off to differentiate between high and low TILs.

Mucosal-associated invariant T-cell tumor infiltration predicts long-term survival in cholangiocarcinoma

BACKGROUND AND AIMS

Cholangiocarcinoma (CCA) is a malignancy arising from biliary epithelial cells of intra- and extrahepatic bile ducts with dismal prognosis and few nonsurgical treatments available. Despite recent success in the immunotherapy-based treatment of many tumor types, this has not been successfully translated to CCA. Mucosal-associated invariant T (MAIT) cells are cytotoxic innate-like T cells highly enriched in the human liver, where they are located in close proximity to the biliary epithelium. Here, we aimed to comprehensively characterize MAIT cells in intrahepatic (iCCA) and perihilar CCA (pCCA).

APPROACH AND RESULTS

Liver tissue from patients with CCA was used to study immune cells, including MAIT cells, in tumor-affected and surrounding tissue by immunohistochemistry, RNA-sequencing, and multicolor flow cytometry. The iCCA and pCCA tumor microenvironment was characterized by the presence of both cytotoxic T cells and high numbers of regulatory T cells. In contrast, MAIT cells were heterogenously lost from tumors compared to the surrounding liver tissue. This loss possibly occurred in response to increased bacterial burden within tumors. The residual intratumoral MAIT cell population exhibited phenotypic and transcriptomic alterations, but a preserved receptor repertoire for interaction with tumor cells. Finally, the high presence of MAIT cells in livers of iCCA patients predicted long-term survival in two independent cohorts and was associated with a favorable antitumor immune signature.

CONCLUSIONS

MAIT cell tumor infiltration associates with favorable immunological fitness and predicts survival in CCA.

The SKI proto-oncogene restrains the resident CD103+CD8+ T cell response in viral clearance

Acute viral infection causes illness and death. In addition, an infection often results in increased susceptibility to a secondary infection, but the mechanisms behind this susceptibility are poorly understood. Since its initial identification as a marker for resident memory CD8⁺ T cells in barrier tissues, the function and regulation of CD103 integrin (encoded by ITGAE gene) have been extensively investigated. Nonetheless, the function and regulation of the resident CD103⁺CD8⁺ T cell response to acute viral infection remain unclear. Although TGFβ signaling is essential for CD103 expression, the precise molecular mechanism behind this regulation is elusive. Here, we reveal a TGFβ-SKI-Smad4 pathway that critically and specifically directs resident CD103⁺CD8⁺ T cell generation for protective immunity against primary and secondary viral infection. We found that resident CD103⁺CD8⁺ T cells are abundant in both lymphoid and nonlymphoid tissues from uninfected mice. CD103 acts as a costimulation signal to produce an optimal antigenic CD8⁺ T cell response to acute viral infection. There is a reduction in resident CD103⁺CD8⁺ T cells following primary infection that results in increased susceptibility of the host to secondary infection. Intriguingly, CD103 expression inversely and specifically correlates with SKI proto-oncogene (SKI) expression but not R-Smad2/3 activation. Ectopic expression of SKI restricts CD103 expression in CD8⁺ T cells in vitro and in vivo to hamper viral clearance. Mechanistically, SKI is recruited to the Itgae loci to directly suppress CD103 transcription by regulating histone acetylation in a Smad4-dependent manner. Our study therefore reveals that resident CD103⁺CD8⁺ T cells dictate protective immunity during primary and secondary infection. Interfering with SKI function may amplify the resident CD103⁺CD8⁺ T cell response to promote protective immunity.

Severity of Sepsis Determines the Degree of Impairment Observed in Circulatory and Tissue-Resident Memory CD8 T Cell Populations

Sepsis reduces the number and function of memory CD8 T cells within the host, contributing to the long-lasting state of immunoparalysis. Interestingly, the relative susceptibility of memory CD8 T cell subsets to quantitative/qualitative changes differ after cecal ligation and puncture (CLP)-induced sepsis. Compared with circulatory memory CD8 T cells (T_CIRCM), moderate sepsis (0-10% mortality) does not result in numerical decline of CD8 tissue-resident memory T cells (T_RM), which retain their "sensing and alarm" IFN-γ-mediated effector function. To interrogate this biologically important dichotomy, vaccinia virus-immune C57BL/6 (B6) mice containing CD8 T_CIRCM and skin T_RM underwent moderate or severe (∼50% mortality) sepsis. Severe sepsis led to increased morbidity and mortality characterized by increased inflammation compared with moderate CLP or sham controls. Severe CLP mice also displayed increased vascular permeability in the ears. Interestingly, skin CD103⁺ CD8 T_RM, detected by i.v. exclusion or two-photon microscopy, underwent apoptosis and subsequent numerical loss following severe sepsis, which was not observed in mice that experienced moderate CLP or sham surgeries. Consequently, severe septic mice showed diminished CD8 T cell-mediated protection to localized skin reinfection. Finally, the relationship between severity of sepsis and demise in circulatory versus tissue-embedded memory CD8 T cell populations was confirmed by examining tumor-infiltrating and nonspecific CD8 T cells in B16 melanoma tumors. Thus, sepsis can differentially affect the presence and function of Ag-specific CD8 T cells that reside inside tissues/tumors depending on the severity of the insult, a notion with direct relevance to sepsis survivors and their ability to mount protective memory CD8 T cell-dependent responses to localized Ag re-encounter.

Phenotypic Differences of CD103+ Tissue-Resident Memory T Cells Associated with Various Cancers

BACKGROUND/AIMS

The presence and clinical importance of tissue-resident memory T (TRM) cells have been recently described in association with various cancer types. However, the frequency and the traditional naïve-effector-memory phenotypic characteristics of TRM cells are largely unknown.

METHODS

We analyzed single-cell populations of colorectal cancer (CC, n = 18), stomach cancer (SC, n = 13), renal cell carcinoma (RCC, n = 19), and breast cancer (BC, n = 16) by dissociation of tumor tissue with collagenase/hyaluronidase. We investigated populations of naïve, effector, and memory T and TRM cells by flow cytometry.

RESULTS

Among CD8- cells, CC was associated with a significantly higher proportion of CD103+ T cells than other tumor types (p < 0.001). Among CD8+ cells, CC and SC were associated with higher CD103+ T-cell proportions than RCC and BC (p < 0.001). Significantly more CD8+ than CD8- cells expressed CD103 (p < 0.001). In association with SC, RCC, and BC, CD8+ T cells had a similar T-cell phenotype composition pattern: fewer effector T cells and more memory-type T cells among CD103+ cells compared with CD103- cells (p < 0.05). Tumors with higher proportion of CD103+ cells had no specific clinicopathologic characteristics than those with lower proportion of CD103+ cells.

CONCLUSION

TRM cell abundance and phenotypes varied among CC, SC, RCC, and BC. Further studies regarding the functional differences of TRM associated with various tumors are warranted.

CD163+ cytokine-producing cDC2 stimulate intratumoral type 1 T cell responses in HPV16-induced oropharyngeal cancer

Background

Human papillomavirus (HPV)-associated oropharyngeal squamous cell carcinoma (OPSCC) is a distinct clinical entity with a much better prognosis after (chemo)radiotherapy than HPV-negative OPSCC, especially in patients with a concomitant intratumoral HPV-specific and type-1 cytokine-oriented T cell response. However, knowledge on the type of myeloid cells and their coordination with intratumoral T cells and influence on patient outcome in OPSCC is lacking.

Methods

We analyzed the presence of intratumoral myeloid cells and their relationship to tumor-infiltrating T cells and patient outcome in a well-described cohort of HPV16⁺ patients with OPSCC using multispectral immunofluorescence, flow cytometry and functional analyses.

Results

We show that the tumor microenvironment of HPV16⁺ OPSCC tumors with such an ongoing HPV16-specific T cell response is highly infiltrated with a newly defined CD163⁺ cytokine-producing subset of conventional dendritic cell type 2 (cDC2), called DC3. These CD163⁺ cDC2 predominantly stimulated type 1 T cell polarization and produced high levels of interleukin-12 (IL-12) and IL-18, required for IFNγ and IL-22 production by T cells after cognate antigen stimulation. Tumor-infiltration with these CD163⁺ cDC2 positively correlated with the infiltration by Tbet⁺ and tumor-specific T cells, and with prolonged survival.

Conclusions

These data suggest an important role for intratumoral CD163⁺ cDC2 in stimulating tumor-infiltrating T cells to exert their antitumor effects.

Hypoxia acts as an environmental cue for the human tissue-resident memory T cell differentiation program

Tissue-resident memory T cells (T_RM) provide frontline defense against infectious diseases and contribute to antitumor immunity; however, aside from the necessity of TGF-β, knowledge regarding T_RM-inductive cues remains incomplete, particularly for human cells. Oxygen tension is an environmental cue that distinguishes peripheral tissues from the circulation, and here, we demonstrate that differentiation of human CD8⁺ T cells in the presence of hypoxia and TGF-β1 led to the development of a T_RM phenotype, characterized by a greater than 5-fold increase in CD69⁺CD103⁺ cells expressing human T_RM hallmarks and enrichment for endogenous human T_RM gene signatures, including increased adhesion molecule expression and decreased expression of genes involved in recirculation. Hypoxia and TGF-β1 synergized to produce a significantly larger population of T_RM phenotype cells than either condition alone, and comparison of these cells from the individual and combination conditions revealed distinct phenotypic and transcriptional profiles, indicating a programming response to milieu rather than a mere expansion. Our findings identify a likely previously unreported cue for the T_RM differentiation program and can enable facile generation of human T_RM phenotype cells in vitro for basic studies and translational applications such as adoptive cellular therapy.

Single-cell Profiles and Prognostic Impact of Tumor-Infiltrating Lymphocytes Coexpressing CD39, CD103, and PD-1 in Ovarian Cancer

PURPOSE

Tumor-infiltrating lymphocytes (TIL) are strongly associated with survival in most cancers; however, the tumor-reactive subset that drives this prognostic effect remains poorly defined. CD39, CD103, and PD-1 have been independently proposed as markers of tumor-reactive CD8⁺ TIL in various cancers. We evaluated the phenotype, clonality, and prognostic significance of TIL expressing various combinations of these markers in high-grade serous ovarian cancer (HGSC), a malignancy in need of more effective immunotherapeutic approaches.

EXPERIMENTAL DESIGN

Expression of CD39, CD103, PD-1, and other immune markers was assessed by high-dimensional flow cytometry, single-cell sequencing, and multiplex immunofluorescence of primary and matched pre/post-chemotherapy HGSC specimens.

RESULTS

Coexpression of CD39, CD103, and PD-1 ("triple-positive" phenotype) demarcated subsets of CD8⁺ TIL and CD4⁺ regulatory T cells (Treg) with a highly activated/exhausted phenotype. Triple-positive CD8⁺ TIL exhibited reduced T-cell receptor (TCR) diversity and expressed genes involved in both cytolytic and humoral immunity. Triple-positive Tregs exhibited higher TCR diversity and a tumor-resident phenotype. Triple-positive TIL showed superior prognostic impact relative to TIL expressing other combinations of these markers. TIGIT was uniquely upregulated on triple-positive CD8⁺ effector cells relative to their CD4⁺ Treg counterparts.

CONCLUSIONS

Coexpression of CD39, CD103, and PD-1 demarcates highly activated CD8⁺ and CD4⁺ TIL with inferred roles in cytolytic, humoral, and regulatory immune functions. Triple-positive TIL demonstrate exceptional prognostic significance and express compelling targets for combination immunotherapy, including PD-1, CD39, and TIGIT.

Ptpn2 and KLRG1 regulate the generation and function of tissue-resident memory CD8+ T cells in skin

Tissue-resident memory T cells (T_RM cells) are key elements of tissue immunity. Here, we investigated the role of the regulator of T cell receptor and cytokine signaling, Ptpn2, in the formation and function of T_RM cells in skin. Ptpn2-deficient CD8⁺ T cells displayed a marked defect in generating CD69⁺ CD103⁺ T_RM cells in response to herpes simplex virus type 1 (HSV-1) skin infection. This was accompanied by a reduction in the proportion of KLRG1⁻ memory precursor cells and a transcriptional bias toward terminal differentiation. Of note, forced expression of KLRG1 was sufficient to impede T_RM cell formation. Normalizing memory precursor frequencies by transferring equal numbers of KLRG1⁻ cells restored T_RM generation, demonstrating that Ptpn2 impacted skin seeding with precursors rather than downstream T_RM cell differentiation. Importantly, Ptpn2-deficient T_RM cells augmented skin autoimmunity but also afforded superior protection from HSV-1 infection. Our results emphasize that KLRG1 repression is required for optimal T_RM cell formation in skin and reveal an important role of Ptpn2 in regulating T_RM cell functionality.

Cytotoxic CD8+ T cells and tissue resident memory cells in colorectal cancer based on microsatellite instability and BRAF status

BACKGROUND

Recent studies in non-colorectal malignancy have associated T resident memory (T_RM) cells with improved patient survival. It is unknown if T_RM plays a role in colorectal cancer (CRC).

AIM

To examine the potential role of T_RM cells in providing immunogenicity in CRC stratified by microsatellite instability (MSI) and BRAF status.

METHODS

Patients with known MSI and BRAF mutation status were eligible for inclusion in this study. CRC tumour sections stained with haematoxylin and eosin were microscopically reviewed and the images scanned prior to assessment for location of invading edge and core of tumour. Sequential sections were prepared for quantitative multiplex immunohistochemistry (IHC) staining. Opal Multiplex IHC staining was performed with appropriate positive and negative controls and imaged using a standard fluorescent microscope fitted with a spectral scanning camera (Mantra) in conjunction with Mantra snap software. Images were unmixed and annotated in inForm 2.2.0. Statistical analysis was performed using Graphpad Prism Version 7 and Stata Version 15.

RESULTS

Seventy-two patients with known MSI and BRAF status were included in the study. All patients were assessed for MSI by IHC and high resolution capillary electrophoresis testing and 44 of these patients successfully underwent quantitative multiplex IHC staining. Overall, there was a statistically significant increase in CD8+ T_RM cells in the MSI (BRAF mutant and wild type) group over the microsatellite stable (MSS) group. There was a statistically significant difference in CD8+ T_RM between high level MSI (MSI-H):BRAF mutant [22.57, 95% confidence interval (CI): 14.31-30.84] vs MSS [8.031 (95%CI: 4.698-11.36)], P = 0.0076 andMSI-H:BRAF wild type [16.18 (95%CI: 10.44-21.93)] vs MSS [8.031 (95%CI: 4.698-11.36)], P = 0.0279. There was no statistically significant difference in CD8 T cells (both CD8+CD103- and CD8+CD103+T_RM) between MSI-H: BRAF mutant and wild type CRC.

CONCLUSION

This study has shown that CD8+ T_RM are found in greater abundance in MSI-H CRC, both BRAF mutant and MSI-H:BRAF wild type, when compared with their MSS counterpart. CD8+ T_RM may play a role in the immunogenicity in MSI-H CRC (BRAF mutant and BRAF wild type). Further studies should focus on the potential immunogenic qualities of T_RM cells and investigate potential immunotherapeutic approaches to improve treatment and survival associated with CRC.

Intratumoral CD103+ CD8+ T cells predict response to PD-L1 blockade

BACKGROUND

CD8+ tissue-resident memory T (T_RM) cells, marked by CD103 (ITGAE) expression, are thought to actively suppress cancer progression, leading to the hypothesis that their presence in tumors may predict response to immunotherapy.

METHODS

Here, we test this by combining high-dimensional single-cell modalities with bulk tumor transcriptomics from 1868 patients enrolled in lung and bladder cancer clinical trials of atezolizumab (anti-programmed cell death ligand 1 (PD-L1)).

RESULTS

ITGAE was identified as the most significantly upregulated gene in inflamed tumors. Tumor CD103+ CD8+ T_RM cells exhibited a complex phenotype defined by the expression of checkpoint regulators, cytotoxic proteins, and increased clonal expansion.

CONCLUSIONS

Our analyses indeed demonstrate that the presence of CD103+ CD8+ T_RM cells, quantified by tracking intratumoral CD103 expression, can predict treatment outcome, suggesting that patients who respond to PD-1/PD-L1 blockade are those who exhibit an ongoing antitumor T-cell response.

Hypoxia-inducible factor activity promotes antitumor effector function and tissue residency by CD8+ T cells

Adoptive T cell therapies (ACTs) hold great promise in cancer treatment, but low overall response rates in patients with solid tumors underscore remaining challenges in realizing the potential of this cellular immunotherapy approach. Promoting CD8+ T cell adaptation to tissue residency represents an underutilized but promising strategy to improve tumor-infiltrating lymphocyte (TIL) function. Here, we report that deletion of the HIF negative regulator von Hippel-Lindau (VHL) in CD8+ T cells induced HIF-1α/HIF-2α-dependent differentiation of tissue-resident memory-like (Trm-like) TILs in mouse models of malignancy. VHL-deficient TILs accumulated in tumors and exhibited a core Trm signature despite an exhaustion-associated phenotype, which led to retained polyfunctionality and response to αPD-1 immunotherapy, resulting in tumor eradication and protective tissue-resident memory. VHL deficiency similarly facilitated enhanced accumulation of chimeric antigen receptor (CAR) T cells with a Trm-like phenotype in tumors. Thus, HIF activity in CD8+ TILs promotes accumulation and antitumor activity, providing a new strategy to enhance the efficacy of ACTs.

Tissue-resident memory T cells in tumor immunity and immunotherapy

Tissue-resident memory T cells (T_RM) represent a heterogeneous T cell population with the functionality of both effector and memory T cells. T_RM express residence gene signatures. This feature allows them to traffic to, reside in, and potentially patrol peripheral tissues, thereby enforcing an efficient long-term immune-protective role. Recent studies have revealed T_RM involvement in tumor immune responses. T_RM tumor infiltration correlates with enhanced response to current immunotherapy and is often associated with favorable clinical outcome in patients with cancer. Thus, targeting T_RM may lead to enhanced cancer immunotherapy efficacy. Here, we review and discuss recent advances on the nature of T_RM in the context of tumor immunity and immunotherapy.

Development of a CD8 co-receptor independent T-cell receptor specific for tumor-associated antigen MAGE-A4 for next generation T-cell-based immunotherapy

BACKGROUND

The cancer-testis antigen MAGE-A4 is an attractive target for T-cell-based immunotherapy, especially for indications with unmet clinical need like non-small cell lung or triple-negative breast cancer.

METHODS

An unbiased CD137-based sorting approach was first used to identify an immunogenic MAGE-A4-derived epitope (GVYDGREHTV) that was properly processed and presented on human leukocyte antigen (HLA)-A2 molecules encoded by the HLA-A*02:01 allele. To isolate high-avidity T cells via subsequent multimer sorting, an in vitro priming approach using HLA-A2-negative donors was conducted to bypass central tolerance to this self-antigen. Pre-clinical parameters of safety and activity were assessed in a comprehensive set of in vitro and in vivo studies.

RESULTS

A MAGE-A4-reactive, HLA-A2-restricted T-cell receptor (TCR) was isolated from primed T cells of an HLA-A2-negative donor. The respective TCR-T-cell (TCR-T) product bbT485 was demonstrated pre-clinically to have a favorable safety profile and superior in vivo potency compared with TCR-Ts expressing a TCR derived from a tolerized T-cell repertoire to self-antigens. This natural high-avidity TCR was found to be CD8 co-receptor independent, allowing effector functions to be elicited in transgenic CD4+ T helper cells. These CD4+ TCR-Ts supported an anti-tumor response by direct killing of MAGE-A4-positive tumor cells and upregulated hallmarks associated with helper function, such as CD154 expression and release of key cytokines on tumor-specific stimulation.

CONCLUSION

The extensive pre-clinical assessment of safety and in vivo potency of bbT485 provide the basis for its use in TCR-T immunotherapy studies. The ability of this non-mutated high-avidity, co-receptor-independent TCR to activate CD8+ and CD4+ T cells could potentially provide enhanced cellular responses in the clinical setting through the induction of functionally diverse T-cell subsets that goes beyond what is currently tested in the clinic.

The Whole Body as the System in Systems Immunology

The human immune system is comprised of a diverse and interactive network of specialized cells localized in diverse tissues throughout the body, where they mediate protection against pathogens and environmental insults while maintaining tissue homeostasis. Although much of our understanding of human immunology has derived from studies of peripheral blood, recent work utilizing human tissue resources and innovative computational methods have employed a whole-body, systems-based approach, revealing tremendous complexity and heterogeneity of the immune system within individuals and across the population. In this review, we discuss how tissue localization, developmental and age-associated changes, and conditions of health and disease shape the immune response, as well as how improved understanding of interindividual and tissue-specific immunity can be leveraged for developing targeted therapeutics.

To Remember or to Forget: The Role of Good and Bad Memories in Adoptive T Cell Therapy for Tumors

The generation of immunological memory is a hallmark of adaptive immunity by which the immune system “remembers” a previous encounter with an antigen expressed by pathogens, tumors, or normal tissues; and, upon secondary encounters, mounts faster and more effective recall responses. The establishment of T cell memory is influenced by both cell-intrinsic and cell-extrinsic factors, including genetic, epigenetic and environmental triggers. Our current knowledge of the mechanisms involved in memory T cell differentiation has instructed new opportunities to engineer T cells with enhanced anti-tumor activity. The development of adoptive T cell therapy has emerged as a powerful approach to cure a subset of patients with advanced cancers. Efficacy of this approach often requires long-term persistence of transferred T cell products, which can vary according to their origin and manufacturing conditions. Host preconditioning and post-transfer supporting strategies have shown to promote their engraftment and survival by limiting the competition with a hostile tumor microenvironment and between pre-existing immune cell subsets. Although in the general view pre-existing memory can confer a selective advantage to adoptive T cell therapy, here we propose that also “bad memories”—in the form of antigen-experienced T cell subsets—co-evolve with consequences on newly transferred lymphocytes. In this review, we will first provide an overview of selected features of memory T cell subsets and, then, discuss their putative implications for adoptive T cell therapy.

Modulation of Determinant Factors to Improve Therapeutic Combinations with Immune Checkpoint Inhibitors

Immune checkpoint inhibitors (ICPi) have shown their superiority over conventional therapies to treat some cancers. ICPi are effective against immunogenic tumors. However, patients with tumors poorly infiltrated with immune cells do not respond to ICPi. Combining ICPi with other anticancer therapies such as chemotherapy, radiation, or vaccines, which can stimulate the immune system and recruit antitumor T cells into the tumor bed, may be a relevant strategy to increase the proportion of responding patients. Such an approach still raises the following questions: What are the immunological features modulated by immunogenic therapies that can be critical to ensure not only immediate but also long-lasting tumor protection? How must the combined treatments be administered to the patients to harness their full potential while limiting adverse immunological events? Here, we address these points by reviewing how immunogenic anticancer therapies can provide novel therapeutic opportunities upon combination with ICPi. We discuss their ability to create a permissive tumor microenvironment through the generation of inflamed tumors and stimulation of memory T cells such as resident (T_RM) and stem-cell like (T_SCM) cells. We eventually underscore the importance of sequence, dose, and duration of the combined anticancer therapies to design optimal and successful cancer immunotherapy strategies.

Modeling Cancer Dynamics

Cancer is a complex disease that continues to pose formidable challenges to therapeutic interventions. An increased understanding of cancer complexity and in particular tumor growth dynamics is critical to the development of more effective therapies. In this respect, an agent-based model of tumor growth is explored with the consideration of cancer reprograming of metabolism and the immune response, to seek insight about the coupling between these two key determinants of tumor growth dynamics. Ultimately, this exploration is intended to inform the development of therapies that can induce a more effective immune response despite the metabolic constraints of the tumor microenvironment.

Characterization of tumour-infiltrating lymphocytes in a tumour rejection cynomolgus macaque model

Immunotherapy has emerged as a promising and effective treatment for cancer, yet the clinical benefit is still variable, in part due to insufficient accumulation of immune effector cells in the tumour microenvironment. Better understanding of tumour-infiltrating lymphocytes (TILs) from nonhuman primate tumours could provide insights into improving effector cell accumulation in tumour tissues during immunotherapy. Here, we characterize TILs in a cynomolgus macaque tumour model in which the tumours were infiltrated with CD4⁺ and CD8⁺ T cells and were eventually rejected. The majority of CD4⁺ and CD8⁺ TILs exhibited a CD45RA⁻CCR7⁻ effector memory phenotype, but unlike circulating T cells, they expressed CD69, a marker for tissue-resident memory T (T_RM) cells. CD69-expressing CD8⁺ TILs expressed high levels of the cytotoxic molecule granzyme B and the co-inhibitory receptor PD-1. Consistent with the T_RM cell phenotype, CD8⁺ TILs minimally expressed CX3CR1 but expressed CXCR3 at higher levels than circulating CD8⁺ T cells. Meanwhile, CXCL9, CXCL10 and CXCL11, chemokine ligands for CXCR3, were expressed at high levels in the tumours, thus attracting CXCR3⁺CD8⁺ T cells. These results indicate that tumour-transplanted macaques can be a useful preclinical model for studying and optimizing T cell accumulation in tumours for the development of new immunotherapies.

CD103+ T and Dendritic Cells Indicate a Favorable Prognosis in Oral Cancer

T cells and dendritic cells (DCs) that are positive for the tissue-resident marker CD103 play a vital role in antitumor immunity. In this study, multiplexed immunohistochemistry was applied to stain CD103 and the T-cell marker CD8 as well as the DC marker CD11c on formalin-fixed, paraffin-embedded oral squamous cell carcinoma (OSCC) tissues. Then, the density of CD103⁺CD8⁺ and CD103⁺CD11c⁺ tumor-infiltrating lymphocytes (TILs) in the intratumoral and stromal regions was calculated, and the correlation of CD103⁺CD8⁺ TIL and CD103⁺CD11c⁺ TIL density with OSCC patient prognosis was analyzed. The results revealed that CD103⁺CD8⁺ TILs and CD103⁺CD11c⁺ TILs were abundant in the stromal region and that increased stromal CD103⁺CD8⁺ TIL and intratumoral CD103⁺CD11c⁺ TIL density indicated a favorable prognosis. Moreover, we freshly isolated TILs from OSCC samples and performed flow cytometry to verify that CD103⁺CD8⁺ TILs display a tissue-resident memory T-cell (Trm) phenotype, and we discriminated CD103⁺CD11c⁺ TILs from tumor-associated macrophages.

Precursor exhausted T cells: key to successful immunotherapy?

Cytotoxic T cell immunity in response to chronic infections and tumours is maintained by a specialized population of CD8⁺ T cells that exhibit hallmarks of both exhausted and memory cells and give rise to terminally differentiated exhausted effector cells that contribute to viral or tumour control. Importantly, recent work suggests these cells, which we refer to as 'precursor exhausted' T (T_PEX) cells, are responsible for the proliferative burst that generates effector T cells in response to immune checkpoint blockade targeting programmed cell death 1 (PD1), and increased T_PEX cell frequencies have recently been linked to increased patient survival. We believe the recent discovery of T_PEX cells not only represents a paradigm shift in our understanding of the mechanisms that maintain CD8⁺ T cell responses in chronic infections and tumours but also opens up unexpected avenues for the development of new and innovative therapeutic approaches. In this Opinion article, we discuss the differentiation and function of T_PEX cells and suggest that targeting these cells may be key for successful immunotherapy.

Dendritic Cells and CD8 T Cell Immunity in Tumor Microenvironment

Dendritic cells (DCs) play a central role in the regulation of the balance between CD8 T cell immunity vs. tolerance to tumor antigens. Cross-priming, a process which DCs activate CD8 T cells by cross-presenting exogenous antigens, plays a critical role in generating anti-tumor CD8 T cell immunity. However, there are compelling evidences now that the tumor microenvironment (TME)-mediated suppression and modulation of tumor-infiltrated DCs (TIDCs) impair their function in initiating potent anti-tumor immunity and even promote tumor progression. Thus, DC-mediated cross-presentation of tumor antigens in tumor-bearing hosts often induces T cell tolerance instead of immunity. As tumor-induced immunosuppression remains one of the major hurdles for cancer immunotherapy, understanding how DCs regulate anti-tumor CD8 T cell immunity in particular within TME has been under intensive investigation. Recent reports on the Batf3-dependent type 1 conventional DCs (cDC1s) in anti-tumor immunity have greatly advanced our understanding on the interplay of DCs and CD8 T cells in the TME, highlighted by the critical role of CD103⁺ cDC1s in the cross-priming of tumor antigen-specific CD8 T cells. In this review, we will discuss recent advances in anti-tumor CD8 T cell cross-priming by CD103⁺ cDC1s in TME, and share perspective on future directions including therapeutic applications and memory CD8 T cell responses.