Tumor Interferon Signaling Regulates a Multigenic Resistance Program to Immune Checkpoint Blockade.

Therapeutic blocking of the PD1 pathway results in significant tumor responses, but resistance is common. We demonstrate that prolonged interferon signaling orchestrates PDL1-dependent and PDL1-independent resistance to immune checkpoint blockade (ICB) and to combinations such as radiation plus anti-CTLA4. Persistent type II interferon signaling allows tumors to acquire STAT1-related epigenomic changes and augments expression of interferon-stimulated genes and ligands for multiple T cell inhibitory receptors. Both type I and II interferons maintain this resistance program. Crippling the program genetically or pharmacologically interferes with multiple inhibitory pathways and expands distinct T cell populations with improved function despite expressing markers of severe exhaustion. Consequently, tumors resistant to multi-agent ICB are rendered responsive to ICB monotherapy. Finally, we observe that biomarkers for interferon-driven resistance associate with clinical progression after anti-PD1 therapy. Thus, the duration of tumor interferon signaling augments adaptive resistance and inhibition of the interferon response bypasses requirements for combinatorial ICB therapies.

Exosome transfer from stromal to breast cancer cells regulates therapy resistance pathways.

Stromal communication with cancer cells can influence treatment response. We show that stromal and breast cancer (BrCa) cells utilize paracrine and juxtacrine signaling to drive chemotherapy and radiation resistance. Upon heterotypic interaction, exosomes are transferred from stromal to BrCa cells. RNA within exosomes, which are largely noncoding transcripts and transposable elements, stimulates the pattern recognition receptor RIG-I to activate STAT1-dependent antiviral signaling. In parallel, stromal cells also activate NOTCH3 on BrCa cells. The paracrine antiviral and juxtacrine NOTCH3 pathways converge as STAT1 facilitates transcriptional responses to NOTCH3 and expands therapy-resistant tumor-initiating cells. Primary human and/or mouse BrCa analysis support the role of antiviral/NOTCH3 pathways in NOTCH signaling and stroma-mediated resistance, which is abrogated by combination therapy with gamma secretase inhibitors. Thus, stromal cells orchestrate an intricate crosstalk with BrCa cells by utilizing exosomes to instigate antiviral signaling. This expands BrCa subpopulations adept at resisting therapy and reinitiating tumor growth.

Radiation and dual checkpoint blockade activate non-redundant immune mechanisms in cancer.

Immune checkpoint inhibitors result in impressive clinical responses, but optimal results will require combination with each other and other therapies. This raises fundamental questions about mechanisms of non-redundancy and resistance. Here we report major tumour regressions in a subset of patients with metastatic melanoma treated with an anti-CTLA4 antibody (anti-CTLA4) and radiation, and reproduced this effect in mouse models. Although combined treatment improved responses in irradiated and unirradiated tumours, resistance was common. Unbiased analyses of mice revealed that resistance was due to upregulation of PD-L1 on melanoma cells and associated with T-cell exhaustion. Accordingly, optimal response in melanoma and other cancer types requires radiation, anti-CTLA4 and anti-PD-L1/PD-1. Anti-CTLA4 predominantly inhibits T-regulatory cells (Treg cells), thereby increasing the CD8 T-cell to Treg (CD8/Treg) ratio. Radiation enhances the diversity of the T-cell receptor (TCR) repertoire of intratumoral T cells. Together, anti-CTLA4 promotes expansion of T cells, while radiation shapes the TCR repertoire of the expanded peripheral clones. Addition of PD-L1 blockade reverses T-cell exhaustion to mitigate depression in the CD8/Treg ratio and further encourages oligoclonal T-cell expansion. Similarly to results from mice, patients on our clinical trial with melanoma showing high PD-L1 did not respond to radiation plus anti-CTLA4, demonstrated persistent T-cell exhaustion, and rapidly progressed. Thus, PD-L1 on melanoma cells allows tumours to escape anti-CTLA4-based therapy, and the combination of radiation, anti-CTLA4 and anti-PD-L1 promotes response and immunity through distinct mechanisms.

Esophageal Expression of Active IκB Kinase-ß in Mice Up-Regulates Tumor Necrosis Factor and Granulocyte-Macrophage Colony-Stimulating Factor, Promoting Inflammation and Angiogenesis.

BACKGROUND & AIMS: IκB kinase-ß (IKKß) mediates activation of the nuclear factor-κB, which regulates immune and inflammatory responses. Although nuclear factor-κB is activated in cells from patients with inflammatory diseases or cancer, little is known about its roles in the development and progression of esophageal diseases. We investigated whether mice that express an activated form of IKKß in the esophageal epithelia develop esophageal disorders. METHODS: We generated ED-L2-Cre/Rosa26-IKK2caSFL mice, in which the ED-L2 promoter activates expression of Cre in the esophageal epithelia, leading to expression of a constitutively active form of IKKß (IKKßca) in epithelial cells but not in inflammatory cells or the surrounding stroma (IKKßca mice). Mice lacking the Cre transgene served as controls. Some mice were given intraperitoneal injections of neutralizing antibodies against granulocyte-macrophage colony-stimulating factor (GM-CSF) or tumor necrosis factor (TNF), or immunoglobulin G1 (control), starting at 1 month of age. Epithelial tissues were collected and analyzed by immunofluorescence, immunohistochemical, and quantitative real-time polymerase chain reaction assays. Transgenes were overexpressed from retroviral vectors in primary human keratinocytes. RESULTS: IKKßca mice developed esophagitis and had increased numbers of blood vessels in the esophageal stroma, compared with controls. Esophageal tissues from IKKßca mice had increased levels of GM-CSF. Expression of IKKßca in primary human esophageal keratinocytes led to 11-fold overexpression of GM-CSF and 200-fold overexpression of TNF. Incubation of human umbilical vein endothelial cells with conditioned media from these keratinocytes increased endothelial cell migration by 42% and promoted formation of capillary tubes; these effects were blocked by a neutralizing antibody against GM-CSF. Injections of anti-GM-CSF reduced angiogenesis and numbers of CD31+ blood vessels in esophageal tissues of IKKßca mice, but did not alter the esophageal vasculature of control mice and did not alter recruitment of intraepithelial leukocytes to esophageal tissues of IKKßca mice. Injections of anti-TNF prevented the development of esophagitis in IKKßca mice. CONCLUSIONS: Constitutive activation of IKKß in the esophageal epithelia of mice leads to inflammation and angiogenesis, mediated by TNF and GM-CSF, respectively.

CCR2/CCR5 inhibitor permits the radiation-induced effector T cell infiltration in pancreatic adenocarcinoma.

The resistance of pancreatic ductal adenocarcinoma (PDAC) to immune checkpoint inhibitors (ICIs) is attributed to the immune-quiescent and -suppressive tumor microenvironment (TME). We recently found that CCR2 and CCR5 were induced in PDAC following treatment with anti-PD-1 antibody (αPD-1); thus, we examined PDAC vaccine or radiation therapy (RT) as T cell priming mechanisms together with BMS-687681, a dual antagonist of CCR2 and CCR5 (CCR2/5i), in combination with αPD-1 as new treatment strategies. Using PDAC mouse models, we demonstrated that RT followed by αPD-1 and prolonged treatment with CCR2/5i conferred better antitumor efficacy than other combination treatments tested. The combination of RT + αPD-1 + CCR2/5i enhanced intratumoral effector and memory T cell infiltration but suppressed regulatory T cell, M2-like tumor-associated macrophage, and myeloid-derived suppressive cell infiltration. RNA sequencing showed that CCR2/5i partially inhibited RT-induced TLR2/4 and RAGE signaling, leading to decreased expression of immunosuppressive cytokines including CCL2/CCL5, but increased expression of effector T cell chemokines such as CCL17/CCL22. This study thus supports the clinical development of CCR2/5i in combination with RT and ICIs for PDAC treatment.

Radiotherapy and CD40 Activation Separately Augment Immunity to Checkpoint Blockade in Cancer.

Immunotherapy in pancreatic ductal adenocarcinoma (PDA) remains a difficult clinical problem despite success in other disease types with immune checkpoint blockade (ICB) and chimeric antigen receptor T-cell therapy. Mechanisms driving immunosuppression and poor T-cell infiltration in PDA are incompletely understood. Here, we use genetically engineered mouse models of PDA that recapitulate hallmarks of human disease to demonstrate that CD40 pathway activation is required for clinical response to radiotherapy and ICB with αCTLA-4 and αPD-1. The combination of an agonist αCD40 antibody, radiotherapy, and dual ICB eradicated irradiated and unirradiated (i.e., abscopal) tumors, generating long-term immunity. Response required T cells and also short-lived myeloid cells and was dependent on the long noncoding RNA myeloid regulator Morrbid Using unbiased random forest machine learning, we built unique, contextual signatures for each therapeutic component, revealing that (i) radiotherapy triggers an early proinflammatory stimulus, ablating existing intratumoral T cells and upregulating MHC class I and CD86 on antigen-presenting cells, (ii) αCD40 causes a systemic and intratumoral reorganization of the myeloid compartment, and (iii) ICB increases intratumoral T-cell infiltration and improves the CD8 T-cell:regulatory T-cell ratio. Thus, αCD40 and radiotherapy nonredundantly augment antitumor immunity in PDA, which is otherwise refractory to ICB, providing a clear rationale for clinical evaluation.Significance: Radiotherapy and αCD40 disrupt key links between innate and adaptive immunity, ameliorating resistance to immune checkpoint blockade in pancreatic cancer via multiple cellular mechanisms. Cancer Res; 78(15); 4282-91. ©2018 AACR.