Immunotherapies have revolutionized cancer treatment. In particular, immune checkpoint therapy (ICT) leads to durable responses in some patients with some cancers. However, the majority of treated ...patients do not respond. Understanding immune mechanisms that underlie responsiveness to ICT will help identify predictive biomarkers of response and develop treatments to convert non-responding patients to responding ones. ICT primarily acts at the level of adaptive immunity. The specificity of adaptive immune cells, such as T and B cells, is determined by antigen-specific receptors. T cell repertoires can be comprehensively profiled by high-throughput sequencing at the bulk and single-cell level. T cell receptor (TCR) sequencing allows for sensitive tracking of dynamic changes in antigen-specific T cells at the clonal level, giving unprecedented insight into the mechanisms by which ICT alters T cell responses. Here, we review how the repertoire influences response to ICT and conversely how ICT affects repertoire diversity. We will also explore how changes to the repertoire in different anatomical locations can better correlate and perhaps predict treatment outcome. We discuss the advantages and limitations of current metrics used to characterize and represent TCR repertoire diversity. Discovery of predictive biomarkers could lie in novel analysis approaches, such as network analysis of amino acids similarities between TCR sequences. Single-cell sequencing is a breakthrough technology that can link phenotype with specificity, identifying T cell clones that are crucial for successful ICT. The field of immuno-sequencing is rapidly developing and cross-disciplinary efforts are required to maximize the analysis, application, and validation of sequencing data. Unravelling the dynamic behavior of the TCR repertoire during ICT will be highly valuable for tracking and understanding anti-tumor immunity, biomarker discovery, and ultimately for the development of novel strategies to improve patient outcomes.
Mesothelioma is an aggressive asbestos induced cancer with extremely poor prognosis and limited treatment options. Immune checkpoint blockade (ICPB) has demonstrated effective therapy in melanoma and ...is now being applied to other cancers, including mesothelioma. However, the efficacy of ICPB and which immune checkpoint combinations constitute the best therapeutic option for mesothelioma have yet to be fully elucidated. Here, we used our well characterised mesothelioma tumour model to investigate the efficacy of different ICBP treatments to generate effective therapy for mesothelioma. We show that tumour resident regulatory T cell co-express high levels of CTLA-4, OX40 and GITR relative to T effector subsets and that these receptors are co-expressed on a large proportion of cells. Targeting any of CTLA-4, OX40 or GITR individually generated effective responses against mesothelioma. Furthermore, the combination of αCTLA-4 and αOX40 was synergistic, with an increase in complete tumour regressions from 20% to 80%. Other combinations did not synergise to enhance treatment outcomes. Finally, an early pattern in T cell response was predictive of response, with activation status and ICP receptor expression profile of T effector cells harvested from tumour and dLN correlating with response to immunotherapy. Taken together, these data demonstrate that combination ICPB can work synergistically to induce strong, durable immunity against mesothelioma in an animal model.
Immune checkpoint therapy (ICT) results in durable responses in individuals with some cancers, but not all patients respond to treatment. ICT improves CD8
cytotoxic T lymphocyte (CTL) function, but ...changes in tumor antigen-specific CTLs post-ICT that correlate with successful responses have not been well characterized. Here, we studied murine tumor models with dichotomous responses to ICT. We tracked tumor antigen-specific CTL frequencies and phenotype before and after ICT in responding and non-responding animals. Tumor antigen-specific CTLs increased within tumor and draining lymph nodes after ICT, and exhibited an effector memory-like phenotype, expressing IL-7R (CD127), KLRG1, T-bet, and granzyme B. Responding tumors exhibited higher infiltration of effector memory tumor antigen-specific CTLs, but lower frequencies of regulatory T cells compared to non-responders. Tumor antigen-specific CTLs persisted in responding animals and formed memory responses against tumor antigens. Our results suggest that increased effector memory tumor antigen-specific CTLs, in the presence of reduced immunosuppression within tumors is part of a successful ICT response. Temporal and nuanced analysis of T cell subsets provides a potential new source of immune based biomarkers for response to ICT.
With immune checkpoint therapy (ICT) having reshaped the treatment of many cancers, the next frontier is to identify and develop novel combination therapies to improve efficacy. Previously, we and ...others identified beneficial immunological effects of the vitamin A derivative tretinoin on anti-tumour immunity. Although it is known that tretinoin preferentially depletes myeloid derived suppressor cells in blood, little is known about the effects of tretinoin on the tumour microenvironment, hampering the rational design of clinical trials using tretinoin in combination with ICT. Here, we aimed to identify how tretinoin changed the tumour microenvironment in mouse tumour models, using flow cytometry and RNAseq, and we sought to use that information to establish optimal dosing and scheduling of tretinoin in combination with several ICT antibodies in multiple cancer models. We found that tretinoin rapidly induced an interferon dominated inflammatory tumour microenvironment, characterised by increased CD8+ T cell infiltration. This phenotype completely overlapped with the phenotype that was induced by ICT itself, and we confirmed that the combination further amplified this inflammatory milieu. The addition of tretinoin significantly improved the efficacy of anti-CTLA4/anti-PD-L1 combination therapy, and staggered scheduling was more efficacious than concomitant scheduling, in a dose-dependent manner. The positive effects of tretinoin could be extended to ICT antibodies targeting OX40, GITR and CTLA4 monotherapy in multiple cancer models. These data show that tretinoin induces an interferon driven, CD8+ T cell tumour microenvironment that is responsive to ICT.
The success of immunotherapy that targets inhibitory T cell receptors for the treatment of multiple cancers has seen the anti-tumor immune response re-emerge as a promising biomarker of response to ...therapy. Longitudinal characterization of T cells in the tumor microenvironment (TME) helps us understand how to promote effective anti-tumor immunity. However, serial analyses at the tumor site are rarely feasible in clinical practice. Malignant pleural effusions (MPE) associated with thoracic cancers are an abnormal accumulation of fluid in the pleural space that is routinely drained for patient symptom control. This fluid contains tumor cells and immune cells, including lymphocytes, macrophages and dendritic cells, providing a window into the local tumor microenvironment. Recurrent MPE is common, and provides an opportunity for longitudinal analysis of the tumor site in a clinical setting. Here, we review the phenotype of MPE-derived T cells, comparing them to tumor and blood T cells. We discuss the benefits and limitations of their use as potential dynamic biomarkers of response to therapy.
IntroductionThere is a strong theoretical rationale for combining checkpoint blockade with cytotoxic chemotherapy in pleural mesothelioma and other cancers. Two recent single-arm, phase 2 trials ...DuRvalumab with chEmotherapy as first-line treAtment in advanced pleural Mesothelioma (DREAM) and Phase II multicenter study of anti-PD-L1, durvalumab, in combination with cisplatin and pemetrexed for the first-line treatment of unresectable malignant pleural mesothelioma (PrE0505) combining the programmed death ligand-1 (PD-L1) inhibitor durvalumab with standard first-line chemotherapy exceeded prespecified safety and activity criteria to proceed to a phase 3 confirmatory trial to assess this combination. We present the protocol of the DREAM3R trial.Methods and analysisThis multicentre open-label randomised trial will recruit 480 treatment-naïve adults with advanced pleural mesothelioma, randomised (2:1) to either 3-weekly durvalumab 1500 mg plus 3-weekly doublet chemotherapy (cisplatin 75 mg/m2 or carboplatin, Area Under the Curve,AUC 5 and pemetrexed 500 mg/m2) 4–6 cycles, followed by 4-weekly durvalumab 1500 mg until disease progression, unacceptable toxicity or patient withdrawal; OR doublet chemotherapy alone for 4–6 cycles, followed by observation. The target accrual time is 27 months, with follow-up for an additional 24 months. This provides over 85% power if the true HR for overall survival (OS) is 0.70, with two-sided alpha of 0.05, assuming a median OS of 15 months in the control group. Randomisation is stratified by age (18–70 years vs >70), sex, histology (epithelioid vs non-epithelioid), platinum agent (cisplatin vs carboplatin) and region (USA vs Australia/New Zealand vs Other). The primary endpoint is OS. Secondary endpoints include progression-free survival, objective tumour response (by mRECIST V.1.1 and iRECIST), adverse events, health-related quality of life and healthcare resource use. Tertiary correlative objectives are to explore and validate potential prognostic and/or predictive biomarkers (including features identified in the DuRvalumab with chEmotherapy as first-line treAtment in advanced pleural Mesothelioma (DREAM) and PrE0505 studies, PD-L1 expression, tumour mutational burden, genomic characteristics and human leukocyte antigen subtypes) in tissue and serial blood samples. An imaging databank will be assembled for validation of radiological measures of response, and studies of possible radiomic biomarkers in mesothelioma.Ethics and disseminationThe protocol was approved by human research ethics review committees for all participating sites. Results will be disseminated in peer-reviewed journals and at scientific conferences.Drug SupplyAstraZeneca.Protocol versionCTC 0231 / TOGA 18/001 / PrE0506 3.0, 29 July 2021.Trial registration numberClinicalTrials.gov Identifier: NCT04334759 ACTRN 12620001199909.
Antibodies that target immune checkpoints such as cytotoxic T lymphocyte antigen 4 (CTLA-4) and the programmed cell death protein 1/ligand 1 (PD-1/PD-L1) are now a treatment option for multiple ...cancer types. However, as a monotherapy, objective responses only occur in a minority of patients. Chemotherapy is widely used in combination with immune checkpoint blockade (ICB). Although a variety of isolated immunostimulatory effects have been reported for several classes of chemotherapeutics, it is unclear which chemotherapeutics provide the most benefit when combined with ICB. We investigated 10 chemotherapies from the main canonical classes dosed at the clinically relevant maximum tolerated dose in combination with anti-CTLA-4/anti-PD-L1 ICB. We screened these chemo-immunotherapy combinations in two murine mesothelioma models from two different genetic backgrounds, and identified chemotherapies that produced additive, neutral or antagonistic effects when combined with ICB. Using flow cytometry and bulk RNAseq, we characterized the tumor immune milieu in additive chemo-immunotherapy combinations. 5-fluorouracil (5-FU) or cisplatin were additive when combined with ICB while vinorelbine and etoposide provided no additional benefit when combined with ICB. The combination of 5-FU with ICB augmented an inflammatory tumor microenvironment with markedly increased CD8
T cell activation and upregulation of IFNγ, TNFα and IL-1β signaling. The effective anti-tumor immune response of 5-FU chemo-immunotherapy was dependent on CD8
T cells but was unaffected when TNFα or IL-1β cytokine signaling pathways were blocked. Our study identified additive and non-additive chemotherapy/ICB combinations and suggests a possible role for increased inflammation in the tumor microenvironment as a basis for effective combination therapy.
Pre-clinical studies developing novel therapies to prevent cancer recurrence require appropriate surgical models. Here, we present a protocol for surgical debulking of subcutaneous tumors in mice, ...which allows for intraoperative application of immunotherapy-loaded biomaterials. We describe steps for inoculating tumor cells, anesthetizing mice, and performing surgery. We then detail procedures for applying biomaterial, bandaging mice, and data collection and analysis. The optimized bandaging regimen resolves the issue of wound dehiscence after surgery, for C57BL/6 mice, which interfere with surgical sites.
For complete details on the use and execution of this protocol, please refer to Rwandamuriye et al.1
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•Steps for intraoperative application of therapy-loaded biomaterials during surgery•Instructions for bandaging to prevent post-operative wound interference•Guidance on assessing therapeutic efficacy and disease recurrence post-surgery
Publisher’s note: Undertaking any experimental protocol requires adherence to local institutional guidelines for laboratory safety and ethics.
Pre-clinical studies developing novel therapies to prevent cancer recurrence require appropriate surgical models. Here, we present a protocol for surgical debulking of subcutaneous tumors in mice, which allows for intraoperative application of immunotherapy-loaded biomaterials. We describe steps for inoculating tumor cells, anesthetizing mice, and performing surgery. We then detail procedures for applying biomaterial, bandaging mice, and data collection and analysis. The optimized bandaging regimen resolves the issue of wound dehiscence after surgery, for C57BL/6 mice, which interfere with surgical sites.
Cross‐presentation defines the unique capacity of an APC to present exogenous Ag via MHC class I molecules to CD8+ T cells. DCs are specialized cross‐presenting cells and as such have a critical role ...in antitumor immunity. DCs are routinely found within the tumor microenvironment, but their capacity for endogenous or therapeutically enhanced cross‐presentation is not well characterized. In this study, we examined the tumor and lymph node DC cross‐presentation of a nominal marker tumor Ag, HA, expressed by the murine mesothelioma tumor AB1‐HA. We found that tumors were infiltrated by predominantly CD11b+ DCs with a semimature phenotype that could not cross‐present tumor Ag, and therefore, were unable to induce tumor‐specific T‐cell activation or proliferation. Although tumor‐infiltrating DCs were able to take up, process, and cross‐present exogenous cell‐bound and soluble Ags, this was significantly impaired relative to lymph node DCs. Importantly, however, systemic chemotherapy using gemcitabine reversed the defect in Ag cross‐presentation of tumor DCs. These data demonstrate that DC cross‐presentation within the tumor microenvironment is defective, but can be reversed by chemotherapy. These results have important implications for anticancer therapy, particularly regarding the use of immunotherapy in conjunction with cytotoxic chemotherapy.
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