A herpesvirus transactivator and cellular POU proteins extensively regulate DNA binding of the host Notch signaling protein RBP-Jκ to the virus genome.

Reactivation of Kaposi's sarcoma-associated herpesvirus (KSHV) from latency requires the viral transactivator Rta to contact the host protein Jκ recombination signal-binding protein (RBP-Jκ or CSL). RBP-Jκ normally binds DNA sequence-specifically to determine the transcriptional targets of the Notch-signaling pathway, yet Notch alone cannot reactivate KSHV. We previously showed that Rta stimulates RBP-Jκ DNA binding to the viral genome. On a model viral promoter, this function requires Rta to bind to multiple copies of an Rta DNA motif (called "CANT" or Rta-c) proximal to an RBP-Jκ motif. Here, high-resolution ChIP/deep sequencing from infected primary effusion lymphoma cells revealed that RBP-Jκ binds nearly exclusively to different sets of viral genome sites during latency and reactivation. RBP-Jκ bound DNA frequently, but not exclusively, proximal to Rta bound to single, but not multiple, Rta-c motifs. To discover additional regulators of RBP-Jκ DNA binding, we used bioinformatics to identify cellular DNA-binding protein motifs adjacent to either latent or reactivation-specific RBP-Jκ-binding sites. Many of these cellular factors, including POU class homeobox (POU) proteins, have known Notch or herpesvirus phenotypes. Among a set of Rta- and RBP-Jκ-bound promoters, Rta transactivated only those that also contained POU motifs in conserved positions. On some promoters, POU factors appeared to inhibit RBP-Jκ DNA binding unless Rta bound to a proximal Rta-c motif. Moreover, POU2F1/Oct-1 expression was induced during KSHV reactivation, and POU2F1 knockdown diminished infectious virus production. Our results suggest that Rta and POU proteins broadly regulate DNA binding of RBP-Jκ during KSHV reactivation.

Multiplex Quantitative Analysis of Tumor-Infiltrating Lymphocytes, Cancer-Associated Fibroblasts, and CD200 in Pancreatic Cancer.

Pancreatic cancer is marked by a desmoplastic tumor microenvironment and low tumor immunogenicity, making it difficult for immunotherapy drugs to improve outcomes for patients. Tumor-infiltrating lymphocytes (TILs) and cancer-associated fibroblasts (CAFs) are seen in the tumor microenvironment of patients with pancreatic ductal adenocarcinoma (PDAC). In this work, we sought to characterize the expression levels and potential prognostic value of TILs (CD4, CD8, and CD20) and CAFs (Thy-1, FAP, and SMA) in a large retrospective cohort of PDAC patients. Additionally, we investigated the expression levels and prognostic significance of CD200, an immunoinhibitory protein that has shown interest as a potential target for immune checkpoint blockade. We measured the expression levels of these seven proteins with multiplexed immunofluorescence staining and quantitative immunofluorescence (QIF). We found CD8 and FAP to be independent predictors of progression-free survival and overall survival. CD200 was found to be heterogeneously expressed in both the tumor and stromal compartments of PDAC, with the majority of patients having positive stromal expression and negative tumor expression. This work demonstrates the potential clinical utility of CD8 and FAP in PDAC patients, and it sheds light on the expression patterns of CD200 in pancreatic cancer as the protein is being tested as a target for immune checkpoint blockade.

Quantitative Assessment of CD200 and CD200R Expression in Lung Cancer.

CD200/CD200R is an immune checkpoint with broad expression patterns and a potential target for immune therapy. In this study, we assess both CD200 and CD200R expression in solid tumors, with a focus on lung cancer, and evaluate their association with clinicopathologic characteristics, mutation status, outcome, and programmed death-ligand 1 (PD-L1) expression. We used multiplexed quantitative immunofluorescence (QIF) to measure the expression of CD200 and CD200R in a total of 455 patients from three lung cancer cohorts. Using carefully validated antibodies, we performed target measurement with tyramide-based QIF panels and analyzed the data using the PM2000 microscope and AQUA software. CD200 tumor positivity was found in 29.7% of non-small cell lung cancer (NSCLC) patients and 33.3% of lung large cell neuroendocrine carcinoma (LCNEC) patients. CD200 demonstrated notable intratumoral heterogeneity. CD200R was expressed in immune cells in 25% of NSCLC and 41.3% of LCNEC patients. While CD200R is predominantly expressed in immune cells, rare tumor cell staining was seen in a highly heterogeneous pattern. CD200R expression in the stromal compartment was significantly higher in patients with squamous differentiation (p < 0.0001). Neither CD200 nor CD200R were associated with other clinicopathologic characteristics or mutation status. Both biomarkers were not prognostic for disease-free or overall survival in NSCLC. CD200 showed moderate correlation with PD-L1. CD200/CD200R pathway is frequently expressed in lung cancer patients. Differential expression patterns of CD200 and CD200R with PD-L1 suggest a potential role for targeting this pathway alone in patients with NSCLC.

Autocrine TGFß Is a Survival Factor for Monocytes and Drives Immunosuppressive Lineage Commitment.

Transforming growth factor ß (TGFß) is an effector of immune suppression and contributes to a permissive tumor microenvironment that compromises effective immunotherapy. We identified a correlation between TGFB1 and genes expressed by myeloid cells, but not granulocytes, in The Cancer Genome Atlas lung adenocarcinoma data, in which high TGFB1 expression was associated with poor survival. To determine whether TGFß affected cell fate decisions and lineage commitment, we studied primary cultures of CD14+ monocytes isolated from peripheral blood of healthy donors. We discovered that TGFß was a survival factor for CD14+ monocytes, which rapidly executed an apoptotic program in its absence. Continued exposure to TGFß in combination with granulocyte-macrophage colony stimulating factor (GM-CSF) and interleukin 6 (IL6) amplified HLA-DRlowCD14+CD11b+CD33+ myeloid-derived suppressor cells (MDSCs) at the expense of macrophage and dendritic cell (DC) differentiation. MDSCs generated in the presence of TGFß were more effective in suppressing T-cell proliferation and promoted the T regulatory cell phenotype. In contrast, inhibition of TGFß signaling using a small-molecule inhibitor of receptor kinase activity in CD14+ monocytes treated with GM-CSF and IL6 decreased MDSC differentiation and increased differentiation to proinflammatory macrophages and antigen-presenting DCs. The effect of autocrine and paracrine TGFß on myeloid cell survival and lineage commitment suggests that pharmacologic inhibition of TGFß-dependent signaling in cancer would favor antitumor immunity.

Targeting TGFßR2-mutant tumors exposes vulnerabilities to stromal TGFß blockade in pancreatic cancer.

TGFß is important during pancreatic ductal adenocarcinoma (PDA) progression. Canonical TGFß signaling suppresses epithelial pancreatic cancer cell proliferation; as a result, inhibiting TGFß has not been successful in PDA. In contrast, we demonstrate that inhibition of stromal TGFßR2 reduces IL-6 production from cancer-associated fibroblasts, resulting in a reduction of STAT3 activation in tumor cells and reversion of the immunosuppressive landscape. Up to 7% of human PDA have tumor cell-specific deficiency in canonical TGFß signaling via loss of TGFßR2. We demonstrate that in PDA that harbors epithelial loss of TGFßR2, inhibition of TGFß signaling is selective for stromal cells and results in a therapeutic benefit. Our study highlights the potential benefit of TGFß blockade in PDA and the importance of stratifying PDA patients who might benefit from such therapy.

TGFß receptor inhibitor galunisertib is linked to inflammation- and remodeling-related proteins in patients with pancreatic cancer.

PURPOSE: Galunisertib, the first small molecule transforming growth factor beta (TGFß) receptor inhibitor, plus gemcitabine resulted in the improvement of survival in patients with unresectable pancreatic cancer, but markers to identify patients likely to respond are lacking. METHODS: In the Phase 1b/2 JBAJ study, 156 patients were randomized 2:1 to galunisertib + gemcitabine (N = 104) or placebo + gemcitabine (N = 52). Clinical outcome data were integrated with baseline markers and pharmacodynamic markers while patients were on treatment, including circulating proteins using a multi-analyte panel, T cell subset evaluation, and miRNA profiling. RESULTS: Baseline biomarkers associated with overall prognosis regardless of treatment included CA19-9 and TGF-ß1. In addition, IP-10, FSH, MIP-1α, and PAI-1 were potential predictive proteins. Baseline proteins that were changed during treatment included amphiregulin, CA15-3, cathepsin D, P-selectin, RAGE, sortilin, COMP, eotaxin-2, N-BNP, osteopontin, and thrombospondin-4. Plasma miRNA with potential prognostic value included miR-21-5p, miR-301a-3p, miR-210-3p, and miR-141-3p, while those with potential predictive value included miR-424-5p, miR-483-3p, and miR-10b-5p. CONCLUSIONS: Galunisertib + gemcitabine resulted in improvement of overall survival, and 4 proteins (IP-10, FSH, MIP-1α, PAI-1) were potentially predictive for this combination treatment. Future studies should also include baseline evaluation of miR-424-5p, miR-483-3p, and miR-10b-5p. TRIAL REGISTRATION: Clinicaltrials.gov NCT01373164.

FcγRIIIa-dependent IFN-γ release in whole blood assay is predictive of therapeutic IgG1 antibodies safety.

Immunomodulatory monoclonal IgG1 antibodies developed for cancer and autoimmune disease have an inherent risk of systemic release of pro-inflammatory cytokines. In vitro cytokine release assays are currently used to predict cytokine release syndrome (CRS) risk, but the validation of these preclinical tools suffers from the limited number of characterized CRS-inducing IgG1 antibodies and the poor understanding of the mechanisms regulating cytokine release. Here, we incubated human whole blood from naïve healthy volunteers with four monoclonal IgG1 antibodies with different proven or predicted capacity to elicit CRS in clinic and measured cytokine release using a multiplex assay. We found that, in contrast to anti-CD52 antibodies (Campath-1H homolog) that elicited high level of multiple inflammatory cytokines from human blood cells in vitro, other IgG1 antibodies with CRS-inducing potential consistently induced release of a single tested cytokine, interferon (IFN)-γ, with a smaller magnitude than Campath. IFN-γ expression was observed as early as 2-4 h after incubation, mediated by natural killer cells, and dependent upon tumor necrosis factor and FcγRIII. Importantly, the magnitude of the IFN-γ response elicited by IgG1 antibodies with CRS-inducing potential was determined by donor FcγRIIIa-V158F polymorphism. Overall, our results highlight the importance of FcγRIIIa-dependent IFN-γ release in preclinical cytokine release assay for the prediction of CRS risk associated with therapeutic IgG1 antibodies.

Targeting the TGFß pathway with galunisertib, a TGFßRI small molecule inhibitor, promotes anti-tumor immunity leading to durable, complete responses, as monotherapy and in combination with checkpoint blockade.

BACKGROUND: TGFß signaling plays a pleotropic role in tumor biology, promoting tumor proliferation, invasion and metastasis, and escape from immune surveillance. Inhibiting TGFß's immune suppressive effects has become of particular interest as a way to increase the benefit of cancer immunotherapy. Here we utilized preclinical models to explore the impact of the clinical stage TGFß pathway inhibitor, galunisertib, on anti-tumor immunity at clinically relevant doses. RESULTS: In vitro treatment with galunisertib reversed TGFß and regulatory T cell mediated suppression of human T cell proliferation. In vivo treatment of mice with established 4T1-LP tumors resulted in strong dose-dependent anti-tumor activity with close to 100% inhibition of tumor growth and complete regressions upon cessation of treatment in 50% of animals. This effect was CD8+ T cell dependent, and led to increased T cell numbers in treated tumors. Mice with durable regressions rejected tumor rechallenge, demonstrating the establishment of immunological memory. Consequently, mice that rejected immunogenic 4T1-LP tumors were able to resist rechallenge with poorly immunogenic 4 T1 parental cells, suggesting the development of a secondary immune response via antigen spreading as a consequence of effective tumor targeting. Combination of galunisertib with PD-L1 blockade resulted in improved tumor growth inhibition and complete regressions in colon carcinoma models, demonstrating the potential synergy when cotargeting TGFß and PD-1/PD-L1 pathways. Combination therapy was associated with enhanced anti-tumor immune related gene expression profile that was accelerated compared to anti-PD-L1 monotherapy. CONCLUSIONS: Together these data highlight the ability of galunisertib to modulate T cell immunity and the therapeutic potential of combining galunisertib with current PD-1/L1 immunotherapy.

Preclinical assessment of galunisertib (LY2157299 monohydrate), a first-in-class transforming growth factor-ß receptor type I inhibitor.

Transforming growth factor-ß (TGFß) is an important driver of tumor growth via intrinsic and extrinsic mechanisms, and is therefore an attractive target for developing cancer therapeutics. Using preclinical models, we characterized the anti-tumor activity of a small molecule inhibitor of TGFß receptor I (TGFßRI), galunisertib (LY2157299 monohydrate). Galunisertib demonstrated potent and selective inhibition of TGFßRI with corresponding inhibition of downstream signaling via inhibition of SMAD phosphorylation (pSMAD). Galunisertib also inhibited TGFß-induced pSMAD in vivo, which enabled a pharmacokinetic/pharmacodynamic profile in Calu6 and EMT6-LM2 tumors. Galunisertib demonstrated anti-tumor activity including inhibition of tumor cell migration and mesenchymal phenotype, reversal of TGFß-mediated immune-suppression, and tumor growth delay. A concentration-effect relationship was established with a dosing schedule to achieve the optimal level of target modulation. Finally, a rat model demonstrated a correlation between galunisertib-dependent inhibition of pSMAD in tumor tissues and in PBMCs, supporting the use of PBMCs for assessing pharmacodynamic effects. Galunisertib has been tested in several clinical studies with evidence of anti-tumor activity observed in subsets of patients. Here, we demonstrate that galunisertib inhibits a number of TGFß-dependent functions leading to anti-tumor activity. The enhanced understanding of galunisertib provides rationale for further informed clinical development of TGFß pathway inhibitors.

A phase 1 study of anti-TGFß receptor type-II monoclonal antibody LY3022859 in patients with advanced solid tumors.

PURPOSE: LY3022859 is an anti-TGFßRII IgG1 monoclonal antibody that inhibits receptor-mediated signaling activation. The primary objective of this phase I study was to determine a phase II dose in patients with advanced solid tumors. Secondary objectives were to assess safety and pharmacokinetics (PK). METHODS: LY3022859 was infused intravenously (IV) at 1.25 mg/kg over 1 h every 2 weeks (Q2W) (cohort 1A) and at flat doses of 12.5 mg (cohort 1B) and 25 mg (cohort 2) over 3 h Q2W. RESULTS: Fourteen patients were enrolled in cohorts 1A (n = 2), 1B (n = 5), and 2 (n = 7). DLTs were experienced by both patients in cohort 1A (infusion-related reaction) and 2 patients in cohort 2 (cytokine release syndrome and infusion-related reaction). No MTD was determined. At the 25 mg dose level (cohort 2), after fifth infusion, LY3022859 had a short t1/2 (4.37-7.80 h) and rapid clearance (CLss, 0.412 L/h). Exposure increased twofold (from 28.5 to 60.2 µg·h/mL) with increase in dose from 12.5 to 25 mg. No accumulation was observed after repeat administration. CONCLUSIONS: The MTD for LY3022859 was not determined. Dose escalation beyond 25 mg was considered unsafe due to worsening symptoms (uncontrolled cytokine release) despite prophylaxis (corticosteroids and antihistamines). TRIAL REGISTRATION: clinicaltrials.gov Identifier: NCT01646203.

Clinical development of galunisertib (LY2157299 monohydrate), a small molecule inhibitor of transforming growth factor-beta signaling pathway.

Transforming growth factor-beta (TGF-ß) signaling regulates a wide range of biological processes. TGF-ß plays an important role in tumorigenesis and contributes to the hallmarks of cancer, including tumor proliferation, invasion and metastasis, inflammation, angiogenesis, and escape of immune surveillance. There are several pharmacological approaches to block TGF-ß signaling, such as monoclonal antibodies, vaccines, antisense oligonucleotides, and small molecule inhibitors. Galunisertib (LY2157299 monohydrate) is an oral small molecule inhibitor of the TGF-ß receptor I kinase that specifically downregulates the phosphorylation of SMAD2, abrogating activation of the canonical pathway. Furthermore, galunisertib has antitumor activity in tumor-bearing animal models such as breast, colon, lung cancers, and hepatocellular carcinoma. Continuous long-term exposure to galunisertib caused cardiac toxicities in animals requiring adoption of a pharmacokinetic/pharmacodynamic-based dosing strategy to allow further development. The use of such a pharmacokinetic/pharmacodynamic model defined a therapeutic window with an appropriate safety profile that enabled the clinical investigation of galunisertib. These efforts resulted in an intermittent dosing regimen (14 days on/14 days off, on a 28-day cycle) of galunisertib for all ongoing trials. Galunisertib is being investigated either as monotherapy or in combination with standard antitumor regimens (including nivolumab) in patients with cancer with high unmet medical needs such as glioblastoma, pancreatic cancer, and hepatocellular carcinoma. The present review summarizes the past and current experiences with different pharmacological treatments that enabled galunisertib to be investigated in patients.