Scientific Highlights for Friday, Nov. 11, 2022
CD8+ FOXP3+ CELLS PREDICT RESPONSE TO IMMUNOTHERAPY FOR NSCLC
- CD8+FoxP3+ cells represent early, effector T-cells and predict outcomes in patients with resectable non-small cell lung carcinoma (NSCLC) receiving neoadjuvant anti-PD-1-based therapy
Tricia Cottrell (Queen’s University, Canada) presented a study to identify biomarkers of therapeutic response in patients with non-small cell lung carcinoma (NSCLC) receiving neoadjuvant anti-PD-1 therapy. Pre-treatment tumor specimens from patients in the clinical trial of neoadjuvant nivolumab +/- ipilimumab were stained with markers for PD-1, PD-L1, CD8, CD163, FoxP3, and cytokeratin. Eight specimens were from patients who exhibited a major pathologic response (MPR), and 17 samples were from patients who did not exhibit an MPR. Densities of immune cell populations were analyzed with the AstroPath platform, and CD8+ FoxP3+ cells correlated with response to neoadjuvant immune checkpoint blockade (ICB). CD8+ FoxP3+ cells were also associated with improved event free survival and overall survival. Single cell RNA sequencing indicated the transcriptome of CD8+ FoxP3+ T cells as being highly activated and cytotoxic providing a potential mechanism for the association of CD8+ FoxP3+ T cells with response to neoadjuvant ICB for NSCLC.
COMBINING AN ONCOLYTIC VIRUS WITH IMMUNE CHECKPOINT BLOCKADE FOR GLIOMA
- First efficacy and multi-omic analysis data from phase 1 clinical trial of oncolytic viral immunotherapy with CAN-2409 + valacyclovir in combination with nivolumab and standard of care in newly diagnosed high-grade glioma
Patrick Wen (Dana-Farber Cancer Institute, United States) presented results from an ongoing phase I study of nivolumab (nivo) and standard of care chemoradiation with valacyclovir + CAN-2409 for patients with newly diagnosed high-grade glioma (HGG). CAN-2409, a replication-defective adenovirus, delivers thymidine kinase to cancer cells, sensitizing cancer cells to valacyclovir and stimulating an immune response. CAN-2490 was injected into the resection bed during surgery, followed by valacyclovir, chemoradiation, and nivo. 41 patients participated in the study. Treatment was tolerated, and no dose-limiting toxities were observed. Median overall survival was 15.1 months, comparable to the current standard of care. Immunoprofiling and longitudinal analyses of tumor and peripheral blood indicate that CAN-2409 elicits activation of the effector immune response. Proteomic analyses of patient samples indicate an increase in expression of CXCL9, CXCL10, CXCL11, granzymes, and gamma interferon post-treatment. After the first dose of nivo, CD4+ and CD8+ T cell levels were upregulated, and levels of exhausted T cells were decreased. This study suggests that CAN-2409 causes substantial immunological changes in the tumor microenvironment of HGG, and early survival data are encouraging. Some patient responses may have been altered due to no limits on steroid administration to patients prior to surgery, and more subjects should be included in studies to draw further conclusions.
COMBINING IMMUNE CHECKPOINT BLOCKADE WITH RADIOTHERAPY FOR HPV-POSITIVE OROPHARYNGEAL CANCER
- Phase 2 trial of induction and concomitant CTLA-4 (ipilimumab) and PD-1 (nivolumab) immune checkpoint blockade and intensity modulated radiation therapy (IMRT) in HPV-positive oropharyngeal squamous cell carcinoma (HPV-OPSCC)
Maura Gillison (The University of Texas MD Anderson Cancer Center, United States) presented a phase II investigation of the safety and efficacy of induction and concomitant combination immune checkpoint blockade (ICB) with ipilimumab and nivolumab with intensity modulated radiation therapy (IMRT) for HPV-positive oropharyngeal squamous cell carcinoma (HPV-OPSCC). 35 patients were treated in this single-arm trial. The six-month complete response rate was 94%, and two-year progression free survival was 86%. At a median follow-up of 14.9 months, all patients were alive. Although the response rate to induction ICB was 14%, plasma cfHPV clearance was 30% after induction ICB and 100% four weeks after IMRT. IMRT doses to the neck and spinal cord were reduced by 21 to 50%. Induction and concurrent ICB with IMRT resulted in similar clinical efficacies and fewer toxicities compared to the current standard of care of high-dose cisplatin and IMRT. ICB also caused a reduction in radiation doses and in cfHPV clearance.
EXPLORING THE RELATIONSHIP BETWEEN THE GUT MICROBIOME, TERTIARY LYMPHOID STRUCTURES, AND RESPONSE TO IMMUNOTHERAPY
- Metagenomic sequencing reveals unique gut microbial features associated with tertiary lymphoid structures in response to immune checkpoint blockade in solid cancers
Manog Chelvanambi (University of Texas MD Anderson Cancer Center, United States) presented a study of a multi-cancer cohort of patients to characterize the relationship between the gut microbiome and the presence of tertiary lymphoid structures (TLSs) and their influences on patient response to immune checkpoint blockade therapy (ICT). The study included patients from three clinical trials who had received neoadjuvant IT for melanoma, non-small cell lung cancer, and sarcoma. Patient samples included baseline stool samples and paired tumor samples pre- and post-ICT. Tumors from each patient cohort were transcriptionally profiled and scored for TLS signature. Metagenomic analysis of gut microbiota from stool samples. Various taxa were enriched in different cancer cohorts, but Clostridium species were identified in all three TLS-high groups. Network analyses of TLS-high-associated microbiomes centered around Ruminococcus torques and the carbohydrate L-rahmnose, whereas analyses of TLS-low-associated microbiomes identified mostly orphan clusters. These data indicate many species in the gut microbiome influence anti-tumor immunity, TLS formation, and B cell infiltration in tumors. This study is expanding to include other ICT cohorts in order to further identify and characterize mechanisms behind the microbiome’s effect on TLS formation and B cell infiltration.
INTRATUMORAL CELLULAR INTERACTIONS PROMOTE RESPONSE TO IMMUNE CHECKPOINT BLOCKADE
- mregDC/T helper niches enable local reactivation of CD8 T cells upon PD-1 blockade
Assef Magen (Icahn School of Medicine at Mount Sinai, United States) presented a study to identify factors correlating with response to neoadjuvant anti-PD-1 therapy for hepatocellular carcinoma (HCC). Paired single cell RNA and TCR sequencing of patient immune cells indicate that response to immune checkpoint blockade is associated with clonal expansion of CSCL13+ CD4 T helper (CXCL13+ Th) cells and granzyme-expressing PD-1+ CD8 effector-like T cells. Terminally exhausted T cells were prevalent in tumors of non-responders, and PD-1+ TCF-1+ CD8 T cells with features of progenitor-exhausted cells (progenitor CD8 T cells) were observed in tumors of both responders and non-responders. T cell clonotypes that expanded after treatment were also found in pre-treatment tumor samples, suggesting anti-PD-1 therapy reactivates antigen-experienced T cells. Tumors from responders also exhibited elevated levels of mature dendritic cells enriched in immunoregulatory molecules (mreg DCs), which were observed to interact with CXCL13+ Th cells and with progenitor CD8 T cells. These data support a model in which triads of mregDCs, CXCL13+ Th cells, and progenitor CD8 cells form immunogenic niches in the tumors of responding patients, and during PD-1 blockade, mregDCs and CXCL13+ Th cells promote differentiation of progenitor CD8 cells into effector T cells.
CHARACTERIZING THE EFFECTS OF CLONAL HEMATOPOIESIS ON SOLID TUMORS AND RESPONSE TO IMMUNOTHERAPY
- Impact of Tet2-mutant clonal hematopoiesis on solid tumor immunology and response to checkpoint blockade
Shelly Herbrich (University of Texas MD Anderson Cancer Center, United States) reported on a study to determine the impact of clonal hematopoiesis (CH) on solid tumors and response to immune checkpoint blockade (ICB) therapy. CH is characterized by overrepresentation of blood cells arising from a single mutant clone and is more prevalent among individuals over 70 years old. Data from the MSKCC-IMPACT study indicated that patients with detectable CH clones were ten times more likely to develop meyoid malignancies and had poor survival rates for non-hematologic cancers. Models of pancreatic ductal adenocarcinoma (PDAC) were developed in wild type and CH mice and received immune checkpoint blockade (ICB) therapy. Tumors grew more and exhibited less response to ICB in CH mice compared to wild type. Myeloid cells from tumors from both types of mice were sorted and subjected to single cell RNA sequencing. Tumor-associated myeloid cells from CH mice were enriched for type I and type II interferon (IFN) signaling, and while IFN+ myeloid cells were no longer present in the tumors of wild type mice after ICB, these cells persisted after ICB in CH mice. ICB was associated with the expansion of CD8 effector cells in the tumors of wild type mice but not in CH mice. The data support a novel mechanism of immunotherapy resistance in which CH alters the tumor microenvironment through IFN signaling to become immunosuppressive, promoting tumor growth and suppressing a response to ICB.
METABOLIC REPROGRAMMING GENERATES MEMORY-LIKE T CELLS
965 Deficiency of metabolic regulator PKM2 activates the pentose phosphate pathway to generate TCF1+ progenitor CD8 T cells to improve efficacy of PD-1 checkpoint blockade
Geoffrey Markowitz (Weill Cornell Medicine, United States) reported a study to identify mechanisms that support the generation of TCF1-high progenitor CD8+ T cells. Bulk RNA sequencing of tumor-infiltrating lymphocytes (TILs) of lung tumors from mice indicated increased expression of glycolytic enzymes. A screen targeting glycolytic enzymes indicated that knockdown of PKM2 affected differentiation of T cells, causing a more memory-like phenotype. Wild type PKM2 and PKM2 knockout CD8+ t cells were transferred to tumor-bearing mice, which were then treated with treat with PD-1 blockade. PKM2 knockout T cells combined with immune checkpoint blockade blocked tumor growth and provided a significant survival advantage. PKM2 knockout T cells are enriched for glycolytic intermediates and for metabolites from the pentose phosphate pathway (PPP). T cells treated with a small molecule agonist of PPP exhibit reduced cytokine expression and increased TCF1 expression when co-cultured with tumor cells. Preliminary results suggest that PPP agonist T cells transferred to mouse tumors exhibit enhanced TCF-1 expression and improved tumor control compared to wild type T cells.
A PRE-CLINICAL MODEL OF ONCOLYTIC VIRUS RESISTANCE
1133 Remodeling the immunosuppressive tumor microenvironment with oncolytic virus-mediated delivery of a potent TGF-beta inhibitor
Kristin DePeaux (University of Pittsburgh, United States) reported the development of derivatives of the murine head and neck cancer line MEER that are resistant to oncolytic vaccinia virus (VV; MEER-VVR) and sensitive to VV (MEER-VVS) to study resistance to oncolytic viruses. MEER-VVR and MEER-VVS tumors were implanted in mice, treated with VV, and harvested seven days after treatment. Resistant tumors were associated with increased levels of suppressive cytokines and TGF-beta. A VV expressing a dominant-negative TGF-beta inhibitor (VV-TRFbi) that outcompetes wild type TGF-beta for receptor binding was generated and administered to mice with MEER-VVR tumors. VV-TRFbi stimulated increased cytokine production and anti-tumor immunity. VV-TRFbi had a synergistic effect with PD-1 blockade, with a 70% response rate. These data indicate that TGF-beta is a main driver of VV resistance and provide proof-of-concept that combining engineered oncolytic viruses with other immunotherapies can potentially stimulate the immune system to overcome resistance to single immunotherapies.
CONNECTING MICROBIOME METABOLITES TO ANTI-TUMOR IMMUNITY
1307 The microbiome-derived metabolite TMAO drives immune activation and boosts response to immune checkpoint blockade in pancreatic cancer
Gaudi Mirji (Wistar Institute, Philadelphia, United States) presented data providing insights to a mechanism behind the role of the gut microbiome in anti-tumor immunity. TMAO was identified in a screen for microbiome-derived metabolites that promoted anti-tumor immunity in a mouse model of pancreatic ductal adenocarcinoma (PDAC). Both treating mice with exogenous TMAO and providing a choline rich diet to promote TMAO production reduced PDAC tumor burden. TMAO supplementation was associated with upregulation of immunostimulatory tumor-associated macrophages (TAMs), increased activation and proliferation of CD8 cells, and increased levels of TNF-alpha. The anti-tumor effects of TMAO were dependent on the type-1 interferon (IFN) pathway. TMAO had a synergistic anti-tumor effect with anti-PD-1 and anti-PD-1 combined with anti-TIM-3, reducing tumor burden and increasing survival. Bacteria that express the CutC/D gene that encodes the enzyme that generates trimethylamine (TMA), the precursor of TMAO is associated with response to anti-PD-1 therapy and with long-term survival of cancer. These data suggest that strategies targeting the microbiome and/or TMAO levels could potentially increase the efficacy of treatments for PDAC and other cancers.
MECHANISMS UNDERLYING RESISTANCE TO IMMUNE CHECKPOINT INHIBITORS
- Acquired resistance to PD-(L)1 blockade in patients with non-small cell lung cancer (NSCLC)
Biagio Ricciuti (Dana-Farber Cancer Institute, United States) presented an investigation of the mechanisms underlying acquired resistance to immune checkpoint inhibition (ICI) in patients with non-small cell lung cancer (NSCLC). Matched pre- and post-ICI tissue samples from 80 patients with NSCLC who developed acquired resistance to ICI treatment were analyzed. Genomic profiling of samples acquired at the time of resistance identified acquired loss of function mutations in a variety of genes, including STK11, KEAP1, B2M, and SMARCA4. Copy number variations in CDKN2A, MDM2, and MYC and driver mutations in MAPK were also identified. When comparing acquired mutations of the ICI cohort with independent cohorts that developed resistance to chemotherapy or targeted inhibitors, acquired mutations occurred in distinct spectra of genes. Acquired resistance to ICI was associated with decreases in tumor infiltrating CD8 cells and in HLA class I expression by H score. HLA-I expression was not altered in the cohorts resistant to chemotherapy or targeted therapy. Mechanisms of acquired resistance to ICI are heterogeneous, and a deeper understanding of the mechanisms surrounding ICI resistance can inform the development of treatments for individual patients and the design of new clinical trials.
BLOCKADE OF PVIRG REMODELS THE MICROENVIRONMENT OF COLD TUMORS
- PVIRG, a novel T cell checkpoint, is preferentially expressed in TLS on stem-like memory cells, potentially inhibiting their expansion
Eran Ophir (Compugen Ltd, Israel) presented an investigation of DNAM-1 axis genes, PVIRG, TIGIT, DNAM-1, PVRL2, and PVR, and their effects on the tumor microenvironment and tertiary lymphoid structures (TLSs). The DNAM1 axis regulates adaptive and innate immunity. PVIRG expression clusters with CD8+ stem-like memory T cells (Tscms), which differentiate into effector or exhausted T cells. PVRL2, the PVIRG ligand, is expressed on dendritic cells (DCs), and binding of PVIRG with PVRL2 facilitates interaction of DCs with Tscms. Spatial transcriptomic analyses indicate that TLSs and lymph nodes are enriched for Tscms and DCs. These findings support a model in which blocking PVIRG with anti-PVRIG antibody COM701 disrupts PCIRG-PVRL2 interaction, promoting memory T cell activation, expansion and activation. COM701 monotherapy increased IFN gamma expression and immune activation in peripheral blood and increased T cell infiltration colorectal and ovarian tumors. Combining COM701 with nivolumab extensively modulated the tumor microenvironment by increasing TCR clonality, T cell infiltration, and T cell activation in a patient with microsatellite-stable colorectal cancer. COM701 + nivolumab also induced markers of DC activation in three patients. Translational studies of triplet blockade of PVIRG, PD-1, and TIGIT and clinical studies of PVIRG blockade are ongoing.