Immune checkpoint therapy responders display early clonal expansion of tumor infiltrating lymphocytes

Immune checkpoint therapy (ICT) causes durable tumour responses in a subgroup of patients, but it is not well known how T cell receptor beta (TCRβ) repertoire dynamics contribute to the therapeutic response. Using murine models that exclude variation in host genetics, environmental factors and tumour mutation burden, limiting variation between animals to naturally diverse TCRβ repertoires, we applied TCRseq, single cell RNAseq and flow cytometry to study TCRβ repertoire dynamics in ICT responders and non-responders. Increased oligoclonal expansion of TCRβ clonotypes was observed in responding tumours. Machine learning identified TCRβ CDR3 signatures unique to each tumour model, and signatures associated with ICT response at various timepoints before or during ICT. Clonally expanded CD8+ T cells in responding tumours post ICT displayed effector T cell gene signatures and phenotype. An early burst of clonal expansion during ICT is associated with response, and we report unique dynamics in TCRβ signatures associated with ICT response.

What is Kindness in Science and why does it matter?

Kindness in Science is a grassroots initiative to establish a scientific community built on diversity, respect and well-being, which would ultimately lead to happier scientists and better scientific outcomes. We believe that the key areas that we can become kinder as scientists include yourself, each other, the environment and the wider community. Here, we discuss the key barriers to kindness in each of these areas, and ways we can overcome these issues to create kinder, more sustainable and harmonious research teams.

Diabetes induced by checkpoint inhibition in nonobese diabetic mice can be prevented or reversed by a JAK1/JAK2 inhibitor

OBJECTIVES

Immune checkpoint inhibitors have achieved clinical success in cancer treatment, but this treatment causes immune-related adverse events, including type 1 diabetes (T1D). Our aim was to test whether a JAK1/JAK2 inhibitor, effective at treating spontaneous autoimmune diabetes in nonobese diabetic (NOD) mice, can prevent diabetes secondary to PD-L1 blockade.

METHODS

Anti-PD-L1 antibody was injected into NOD mice to induce diabetes, and JAK1/JAK2 inhibitor LN3103801 was administered by oral gavage to prevent diabetes. Flow cytometry was used to study T cells and beta cells. Mesothelioma cells were inoculated into BALB/c mice to induce a transplantable tumour model.

RESULTS

Anti-PD-L1-induced diabetes was associated with increased immune cell infiltration in the islets and upregulated MHC class I on islet cells. Anti-PD-L1 administration significantly increased islet T cell proliferation and islet-specific CD8⁺ T cell numbers in peripheral lymphoid organs. JAK1/JAK2 inhibitor treatment blocked IFNγ-mediated MHC class I upregulation on beta cells and T cell proliferation mediated by cytokines that use the common γ chain receptor. As a result, anti-PD-L1-induced diabetes was prevented by JAK1/JAK2 inhibitor administered before or after checkpoint inhibitor therapy. Diabetes was also reversed when the JAK1/JAK2 inhibitor was administered after the onset of anti-PD-L1-induced hyperglycaemia. Furthermore, JAK1/JAK2 inhibitor intervention after checkpoint inhibitors did not reverse or abrogate the antitumour effects in a transplantable tumour model.

CONCLUSION

A JAK1/JAK2 inhibitor can prevent and reverse anti-PD-L1-induced diabetes by blocking IFNγ and γc cytokine activities. Our study provides preclinical validation of JAK1/JAK2 inhibitor use in checkpoint inhibitor-induced diabetes.

Comprehensive Testing of Chemotherapy and Immune Checkpoint Blockade in Preclinical Cancer Models Identifies Additive Combinations

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.

Interferons limit autoantigen-specific CD8+ T-cell expansion in the non-obese diabetic mouse

Interferon gamma (IFNγ) is a proinflammatory cytokine implicated in autoimmune diseases. However, deficiency or neutralization of IFNγ is ineffective in reducing disease. We characterize islet antigen-specific T cells in non-obese diabetic (NOD) mice lacking all three IFN receptor genes. Diabetes is minimally affected, but at 125 days of age, antigen-specific CD8⁺ T cells, quantified using major histocompatibility complex class I tetramers, are present in 10-fold greater numbers in Ifngr-mutant NOD mice. T cells from Ifngr-mutant mice have increased proliferative responses to interleukin-2 (IL-2). They also have reduced phosphorylated STAT1 and its target gene, suppressor of cytokine signaling 1 (SOCS-1). IFNγ controls the expansion of antigen-specific CD8⁺ T cells by mechanisms which include increased SOCS-1 expression that regulates IL-2 signaling. The expanded CD8⁺ T cells are likely to contribute to normal diabetes progression despite reduced inflammation in Ifngr-mutant mice.

Malignant Pleural Effusions-A Window Into Local Anti-Tumor T Cell Immunity?

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.

Tumor Infiltrating Effector Memory Antigen-Specific CD8+ T Cells Predict Response to Immune Checkpoint Therapy

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.

Characteristics of TCR Repertoire Associated With Successful Immune Checkpoint Therapy Responses

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.

Impaired T cell proliferation by ex vivo BET-inhibition impedes adoptive immunotherapy in a murine melanoma model

Activation of naïve CD8+ T cells stimulates proliferation and differentiation into cytotoxic T-lymphocytes (CTLs). Adoptive T Cell Therapy (ACT) involves multiple rounds of ex vivo activation to generate enough CTLs for reinfusion into patients, but this drives differentiation into terminal effector T cells. Less differentiated CTL populations, such as stem cell memory T cells, are more ideal candidates for ACT because of increased self-renewal and persistent properties. Ex vivo targeting of T cell differentiation with epigenetic modifiers is a potential strategy to improve cytotoxic T-lymphocyte (CTL) generation for ACT. We established a pipeline to assess the effects of epigenetic modifiers on CD8+ T cell proliferation, differentiation, and efficacy in a preclinical melanoma model. Single treatment with epigenetic modifiers inhibited T cell proliferation in vitro, producing CD44hiCD62Lhi effector-like T cells rather than a stem cell memory T cell phenotype. Most epigenetic modifying agents had no significant effect on ACT efficacy with the notable exception of the bromodomain and extraterminal (BET)-inhibitor JQ1 which was associated with a decrease in efficacy compared to unmodified T cells. These findings reveal the complexity of epigenetic targeting of T cell differentiation, highlighting the need to precisely define the epigenetic targeting strategies to improve CTL generation for ACT.

Age-dependent defect in vascular endothelial growth factor expression is associated with reduced hypoxia-inducible factor 1 activity

Previous studies have indicated that advanced age is associated with impaired angiogenesis in part because of reduced levels of vascular endothelial growth factor (VEGF) expression. To investigate potential mechanisms responsible for this age-dependent defect in VEGF expression, aortic smooth muscle cells isolated from young rabbits (ages 6-8 months) or old rabbits (ages 4-5 years) were exposed to normoxic (21% oxygen) or hypoxic (0.1% oxygen) conditions. Hypoxia-induced VEGF expression was significantly lower in old versus young cells. VEGF mRNA stability in hypoxic conditions was similar in both young and old cells. However, transient transfection with a luciferase reporter gene that was transcriptionally regulated by the VEGF promoter revealed a significant defect in VEGF up-regulation following hypoxia in old versus young cells (a 43 versus 117% increase in luciferase activity, p < 0.05); this difference was not seen when a deletion construct lacking the hypoxia-inducible 1 (HIF-1) binding site was used. Moreover, although HIF-1 alpha-mRNA expression was shown to be similar in young and old smooth muscle cells, HIF-1 alpha protein and DNA binding activity were significantly reduced in old versus young smooth muscle cells that were exposed to hypoxia. We propose that age-dependent reduction in hypoxia-induced VEGF expression results from reduced HIF-1 activity and may explain the previously described age-dependent impairment of angiogenesis in response to ischemia.

Age-dependent increase in c-fos activity and cyclin A expression in vascular smooth muscle cells. A potential link between aging, smooth muscle cell proliferation and atherosclerosis

OBJECTIVE

Aging can be defined as a progressive deterioration of biological functions after the organism has attained its maximal reproductive competence, which is usually associated with a decrease in proliferative ability in most cell types. However, in certain pathological situations such as atherosclerosis and restenosis, aging has been shown to be associated with a higher level of vascular smooth muscle cell (VSMC) proliferation and neointimal lesion formation after angioplasty. In the present study, we investigated potential mechanisms involved in the age-dependent increase in VSMC proliferation.

METHODS AND RESULTS

Primary cultures of VSMCs were isolated from young (6-8-month-old) and old (4-5-year-old) New Zealand rabbits. Results from cell counting assays and FACS analysis were consistent with a shortening of the cell cycle in old VSMCs. Western blot analysis in serum stimulated cells showed a significant increase in the level of cyclin A and cyclin-dependent kinase 2 proteins in the old vs. young VSMCs. In marked contrast, expression of cyclin E in VSMCs was not influenced by aging. Transient transfection assays showed an age-dependent increase in transcription from the human cyclin A promoter. Parallel studies demonstrated that the expression of the AP1 transcription factor c-fos, which interacts with the cyclin A promoter and stimulates VSMC proliferation, was also increased in old VSMCs. Consistent with this notion, electrophoretic mobility shift assays demonstrated an increase in AP1 DNA-binding activity in old VSMCs.

CONCLUSIONS

These studies suggest that age-associated increase in c-fos activity contributes to augmented cyclin A expression and VSMC proliferation in old animals. These mechanisms might contribute to the higher prevalence and severity of atherosclerosis in the elderly.

Restoration of E2F expression rescues vascular endothelial cells from tumor necrosis factor-alpha-induced apoptosis

BACKGROUND

Normally, quiescent endothelial cells (EC) line the inner surface of arteries and protect against thrombosis and neointimal growth. A variety of noxious stimuli, including balloon angioplasty, may compromise EC integrity, thereby initiating proliferation and triggering the local release of cytokines, including tumor necrosis factor-alpha (TNF-alpha).

METHODS AND RESULTS

In vivo blockade of TNF-alpha using a soluble receptor molecule results in accelerated reendothelialization at sites of balloon angioplasty, suggesting an important physiological role of TNF-alpha in attenuating regrowth of endothelium after balloon angioplasty. Our studies reveal that TNF-alpha, an apoptosis-inducing cytokine, induces G1 cell-cycle arrest in proliferating EC. Quiescent EC are relatively immune to TNF-induced apoptosis versus proliferating EC, which display repression of the E2F transcription factor coincident with TNF-induced apoptosis and cell-cycle arrest. We also show that in this setting, E2F overexpression exerts a survival effect in proliferating EC and restores cell-cycle progression, in direct contrast to results of prior reports, which revealed that deregulated expression of E2F in normally cycling cells induces apoptosis.

CONCLUSIONS

These data demonstrate that TNF-induced apoptosis is highly dependent on cell-cycle activity and that E2F can function as survival factor under certain conditions.

Vascular endothelial growth factor-C (VEGF-C/VEGF-2) promotes angiogenesis in the setting of tissue ischemia

Recently, vascular endothelial growth factor-C (VEGF-C or VEGF-2) was described as a specific ligand for the endothelial receptor tyrosine kinases VEGFR-2 and VEGFR-3. In vivo data, limited to constitutive overexpression in transgenic mice, have been interpreted as evidence that the growth-promoting effects of VEGF-C are restricted to development of the lymphatic vasculature. The current studies were designed to test the hypothesis that constitutive expression of VEGF-C in adult animals promotes angiogenesis. In vitro, VEGF-C exhibited a dose-dependent mitogenic and chemotactic effect on endothelial cells, particularly for microvascular endothelial cells (72% and 95% potency, respectively, compared with VEGF-A/VEGF-1). VEGF-C stimulated release of nitric oxide from endothelial cells and increased vascular permeability in the Miles assay; the latter effect was attenuated by pretreatment with the nitric oxide synthase inhibitor N(omega)-nitro-L-arginine methyl ester. Both VEGFR-2 and VEGFR-3 receptors were shown to be expressed in human saphenous vein and internal mammary artery. The potential for VEGF-C to promote angiogenesis in vivo was then tested in a rabbit ischemic hindlimb model. Ten days after ligation of the external iliac artery, VEGF-C was administered as naked plasmid DNA (pcVEGF-C; 500 microg) from the polymer coating of an angioplasty balloon (n = 8 each) or as recombinant human protein (rhVEGF-C; 500 microg) by direct intra-arterial infusion. Physiological and anatomical assessments of angiogenesis 30 days later showed evidence of therapeutic angiogenesis for both pcVEGF-C and rhVEGF-C. Hindlimb blood pressure ratio (ischemic/normal) after pcVEGF-C increased to 0.83 +/- 0.03 after pcVEGF-C versus 0.59 +/- 0.04 (P < 0.005) in pGSVLacZ controls and to 0.76 +/- 0.04 after rhVEGF-C versus 0.58 +/- 0.03 (P < 0.01) in control rabbits receiving rabbit serum albumin. Doppler-derived iliac flow reserve was 2.7 +/- 0.1 versus 2.0 +/- 0.2 (P < 0.05) for pcVEGF-C versus LacZ controls and 2.9 +/- 0.3 versus 2.1 +/- 0.2 (P < 0.05) for rhVEGF-C versus albumin controls. Neovascularity was documented by angiography in vivo (angiographic scores: 0.85 +/- 0.05 versus 0.51 +/- 0.02 (P < 0.001) for plasmid DNA and 0.74 +/- 0.08 versus 0.53 +/- 0.03 (P < 0.05) for protein), and capillary density (per mm2) was measured at necropsy (252 +/- 12 versus 183 +/- 10 (P < 0.005) for plasmid DNA and 229 +/- 20 versus 164 +/- 20 (P < 0.05) for protein). In contrast to the results of gene targeting experiments, constitutive expression of VEGF-C in adult animals promotes angiogenesis in the setting of limb ischemia. VEGF-C and its receptors thus constitute an apparently redundant pathway for postnatal angiogenesis and may represent an alternative to VEGF-A for strategies of therapeutic angiogenesis in patients with limb and/or myocardial ischemia.