Janus kinase-signal transducer and activator of transcription (JAK-STAT) signaling mediates almost all immune regulatory processes, including those that are involved in tumor cell recognition and tumor-driven immune escape. Antitumor immune responses are largely driven by STAT1 and STAT2 induction of type I and II interferons (IFNs) and the downstream programs IFNs potentiate. Conversely, STAT3 has been widely linked to cancer cell survival, immunosuppression, and sustained inflammation in the tumor microenvironment. The discovery of JAK-STAT cross-regulatory mechanisms, post-translational control, and non-canonical signal transduction has added a new level of complexity to JAK-STAT governance over tumor initiation and progression. Endeavors to better understand the vast effects of JAK-STAT signaling on antitumor immunity have unearthed a wide range of targets, including oncogenes, miRNAs, and other co-regulatory factors, which direct specific phenotypical outcomes subsequent to JAK-STAT stimulation. Yet, the rapidly expanding field of therapeutic developments aimed to resolve JAK-STAT aberrations commonly reported in a multitude of cancers has been marred by off-target effects. Here, we discuss JAK-STAT biology in the context of immunity and cancer, the consequences of pathway perturbations and current therapeutic interventions, to provide insight and consideration for future targeting innovations.2 of 26 role in pathogenesis [3]. Yet, despite the seemingly linear order of events, the impact of mutations, selective dimerization, negative pathway regulation, and post-translational modifications of pathway members has branded the JAK-STAT axis a complex signaling cascade, of which many regulatory processes are still poorly understood.STATs have emerged as somewhat of a double-edged sword, being widely explored in the context of cancer. While several members of the STAT family, which encompasses STAT1, STAT2, STAT3, STAT4, STAT5A, STAT5B, and STAT6 as a whole, have been linked to tumor initiation and progression (STAT3 and STAT5), others are integral in antitumor defense and the maintenance of an effective and long-term immune response (STAT1 and STAT2) through evolutionarily conserved programs [1]. With increasing emphasis on immune-based agents as important therapeutics in the fight against solid tumor growth and spread, understanding the function of STAT specificity, redundancy, and connectedness in cancer is a critical component of achieving immunotherapeutic augmentation and success.Here, we investigate the good and the bad of STAT signaling in the context of immune regulation and cancer, and discuss how STATs can be targeted to bolster antitumor immune defense. JAK-STAT Signaling and InterferonsThe presence of stimulatory or inhibitory signals governs the innate and adaptive immune activity that controls both effective immune surveillance and facilitates escape. Such signals determine the fate of plastic immune cells, such as T lymphocytes, and regulate their recruitment, survival, status, and eventual death ...

The lack of targeted therapies available for triple-negative breast cancer (TNBC) patients who fail to respond to first-line chemotherapy has sparked interest in immunotherapeutic approaches. However, trials utilizing checkpoint inhibitors targeting the PD-1/PD-L1 axis in TNBC have had underwhelming responses. Here, we investigated the interplay between type I IFN signaling and the PD-1/PD-L1 axis and tested the impact of combining IFN inducers, as immune activators, with anti-PD-1, to induce an antimetastatic immune response. Using models of TNBC, we demonstrated an interplay between type I IFN signaling and tumor cell PD-L1 expression that affected therapeutic response. The data revealed that the type I IFN-inducer poly(I:C) was an effective immune activator and antimetastatic agent, functioning better than anti-PD-1, which was ineffective as a single agent. Poly(I:C) treatment induced PD-L1 expression on TNBC cells, and combined poly(I:C) and anti-PD-1 treatment prolonged metastasis-free survival in a neoadjuvant setting via the induction of a tumor-specific T-cell response. Use of this combination in a late treatment setting did not impact metastasis-free survival, indicating that timing was critical for immunotherapeutic benefit. Together, these data demonstrated anti-PD-1 as an ineffective single agent in preclinical models of TNBC. However, type I IFN inducers were effective immune activators, and neoadjuvant trials combining them with anti-PD-1 to induce a sustained antitumor immune response are warranted. .

Mammography screening has increased the detection of early pre-invasive breast cancers, termed ductal carcinoma in situ (DCIS), increasing the urgency of identifying molecular regulators of invasion as prognostic markers to predict local relapse. Using the MMTV-PyMT breast cancer model and pharmacological protease inhibitors, we reveal that cysteine cathepsins have important roles in early-stage tumorigenesis. To characterize the cell-specific roles of cathepsins in early invasion, we developed a DCIS-like model, incorporating an immortalized myoepithelial cell line (N1ME) that restrained tumor cell invasion in 3D culture. Using this model, we identified an important myoepithelial-specific function of the cysteine cathepsin inhibitor stefin A in suppressing invasion, whereby targeted stefin A loss in N1ME cells blocked myoepithelial-induced suppression of breast cancer cell invasion. Enhanced invasion observed in 3D cultures with N1ME stefin A-low cells was reliant on cathepsin B activation, as addition of the small molecule inhibitor CA-074 rescued the DCIS-like non-invasive phenotype. Importantly, we confirmed that stefin A was indeed abundant in myoepithelial cells in breast tissue. Use of a 138-patient cohort confirmed that myoepithelial stefin A (cystatin A) is abundant in normal breast ducts and low-grade DCIS but reduced in high-grade DCIS, supporting myoepithelial stefin A as a candidate marker of lower risk of invasive relapse. We have therefore identified myoepithelial cell stefin A as a suppressor of early tumor invasion and a candidate marker to distinguish patients who are at low risk of developing invasive breast cancer, and can therefore be spared further treatment. Copyright © 2017 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

The latency associated with bone metastasis emergence in castrate‐resistant prostate cancer is attributed to dormancy, a state in which cancer cells persist prior to overt lesion formation. Using single‐cell transcriptomics and ex vivo profiling, we have uncovered the critical role of tumor‐intrinsic immune signaling in the retention of cancer cell dormancy. We demonstrate that loss of tumor‐intrinsic type I IFN occurs in proliferating prostate cancer cells in bone. This loss suppresses tumor immunogenicity and therapeutic response and promotes bone cell activation to drive cancer progression. Restoration of tumor‐intrinsic IFN signaling by HDAC inhibition increased tumor cell visibility, promoted long‐term antitumor immunity, and blocked cancer growth in bone. Key findings were validated in patients, including loss of tumor‐intrinsic IFN signaling and immunogenicity in bone metastases compared to primary tumors. Data herein provide a rationale as to why current immunotherapeutics fail in bone‐metastatic prostate cancer, and provide a new therapeutic strategy to overcome the inefficacy of immune‐based therapies in solid cancers.

Objectives. Loss of tumor-inherent type I interferon (IFN) signalling has been closely linked to accelerated metastatic progression via decreased immunogenicity and antitumor immunity. Previous studies in murine models of triple-negative breast cancer (TNBC) demonstrate that systemic IFN inducers are effective antimetastatic agents, via sustained antitumor CD8 + T-cell responses. Repeated systemic dosing with recombinant IFNs or IFN inducers is associated with significant toxicities; hence, the use of alternate intratumoral agents is an active area of investigation. It is critical to investigate the impact of intratumoral agents on subsequent metastatic spread to predict clinical impact. Methods. In this study, the local and systemic impact of the intratumoral Toll-like receptor (TLR) 7/8 agonist 3M-052 alone or in combination with anti-PD1 was evaluated in metastatic TNBC models. The IFN-α receptor (IFNAR1) blocking antibody, MAR1-5A3, along with immune-deficient mice and ex vivo assays are utilised to examine the key targets of this agent that are critical for an antimetastatic response. Results. Single intratumoral administration of 3M-052 reduced mammary tumor growth, induced a T-cell-inflamed tumor microenvironment (TME) and reduced metastatic spread to lung. Metastasis suppression was reliant on IFN signalling and an antitumor immune response, in contrast to primary tumor growth inhibition, which was retained in NSG and CD8 + T-cell-depleted mice. 3M-052 action was demonstrated via dendritic cell activation and production of type I IFN and other pro-inflammatory cytokines to initiate a T-cellinflamed TME and promote tumor cell antigen presentation. Conclusion. This work supports neoadjuvant TLR agonist-based

Patients diagnosed with triple negative breast cancer (TNBC) have an increased risk of rapid metastasis compared to other subtypes. Predicting long-term survival post-chemotherapy in patients with TNBC is difficult, yet enhanced infiltration of tumor infiltrating lymphocytes (TILs) has been associated with therapeutic response and reduced risk of metastatic relapse. Immune biomarkers that predict the immune state of a tumor and risk of metastatic relapse pre- or mid-neoadjuvant chemotherapy are urgently needed to allow earlier implementation of alternate therapies that may reduce TNBC patient mortality. Utilizing a neoadjuvant chemotherapy trial where TNBC patients had sequential biopsies taken, we demonstrate that measurement of T-cell subsets and effector function, specifically CD45RO expression, throughout chemotherapy predicts risk of metastatic relapse. Furthermore, we identified the tumor inherent interferon regulatory factor IRF9 as a marker of active intratumoral type I and II interferon (IFN) signaling and reduced risk of distant relapse. Functional implications of tumor intrinsic IFN signaling were demonstrated using an immunocompetent mouse model of TNBC, where enhanced type I IFN signaling increased anti-tumor immunity and metastasis-free survival post-chemotherapy. Using two independent adjuvant cohorts we were able to validate loss of IRF9 as a poor prognostic biomarker pre-chemotherapy. Thus, IRF9 expression may offer early insight into TNBC patient prognosis and tumor heat, allowing for identification of patients that are unlikely to respond to chemotherapy alone and could benefit from further immune-based therapeutic intervention.

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Background: Malignant pleural mesothelioma (MPM) is well known as an aggressive disease with poor survival. This has sparked trials of alternate immune-based therapies in MPM. While up to a quarter of MPM patients respond to immune checkpoint inhibitors (ICIs), predicting response remains challenging and PD-L1 expression alone has been deemed insufficient. Additionally, patients with sarcomatoid MPM are often excluded from trials utilizing ICIs due to their rapid progression. Here, we analyze the association of T lymphocytes with response to ICI-based immunotherapy to uncover predictive immune markers across subtypes.Methods: Retrospective analysis of immunotherapy treated mesothelioma patient cohorts from two sites were pooled. Patient characteristics, including age, sex, subtype and previous treatment were captured.Multiplex immunohistochemistry was used to assess proportions of CD4, CD8, CD45RO and FOXP3 positive infiltrates in MPM and their association with progression free (PFS) and overall (OS) survival post immunotherapy.Results: Samples derived from 22 patients were analyzed; 13 (59%) had epithelioid MPM, 6 (27%) sarcomatoid and 3 (14%) biphasic. The overall ICI response rate was 40%, with a median PFS (mPFS) and OS (mOS) of 3.8 and 11.17 months, respectively. Of the subtypes, sarcomatoid patients displayed the greatest median PFS and OS (>28 months) post ICI compared to the epithelioid subtype (3 and 11 months respectively), which correlated with higher proportions of infiltrating CD8 + , CD45RO + and CD8 + CD45RO + cells. Patients who received ICIs as first-line therapy had greater PFS than those who received it as second or third line post-chemotherapy.Conclusions: High proportions of T lymphocytes and CD45RO + cells were associated with prolonged mPFS and mOS in sarcomatoid patients treated with ICI immunotherapy. These data support the expansion of trials utilizing single and combination ICIs as first-line therapy in sarcomatoid MPM and warrants further studies testing the impact or detriment of chemotherapy pre-ICI.