Metabolic reprogramming of tumor-associated macrophages using glutamine antagonist JHU083 drives tumor immunity in myeloid-rich prostate and bladder cancer tumors

Glutamine metabolism in tumor microenvironments critically regulates anti-tumor immunity. Using glutamine-antagonist prodrug JHU083, we report potent tumor growth inhibition in urologic tumors by JHU083-reprogrammed tumor-associated macrophages (TAMs) and tumor-infiltrating monocytes (TIMs). We show JHU083-mediated glutamine antagonism in tumor microenvironments induces TNF, pro-inflammatory, and mTORC1 signaling in intratumoral TAM clusters. JHU083-reprogrammed TAMs also exhibit increased tumor cell phagocytosis and diminished pro-angiogenic capacities. In vivo inhibition of TAM glutamine consumption resulted in increased glycolysis, a broken TCA cycle, and purine metabolism disruption. Although the anti-tumor effect of glutamine antagonism on tumor-infiltrating T cells was moderate, JHU083 promoted a stem cell-like phenotype in CD8+ T cells and decreased Treg abundance. Finally, JHU083 caused a ubiquitous shutdown in glutamine utilizing metabolic pathways in tumor cells, leading to reduced HIF-1alpha, c-MYC phosphorylation, and induction of tumor cell apoptosis, all key anti-tumor features.

NCOG-05. MANAGEMENT OF BRAIN METASTASIS IN TRIPLE NEGATIVE BREAST CANCER

Brain metastasis is common in patients with breast cancer, and those with triple negative status have an even higher risk. Stereotactic radiosurgery (SRS) is preferred to whole brain radiation therapy (WBRT) in most patients. However, triple negative status is currently not considered when determining optimal radiation therapy. Given the aggressive nature of triple negative breast cancer, we evaluated a role for WBRT for all patients in this cohort. We conducted a single-institution retrospective cohort study to determine whether triple negative patients with brain metastases have a higher burden of intracranial disease and whether type of initial radiation therapy affects overall survival for this cohort of patients. 85 patients met the inclusion criteria for this study. 25% of patients had triple negative breast cancer, of which 91% received SRS and 53% of patients received WBRT. The average number of new brain metastases from time of initial brain imaging to radiation therapy was 0.67 (St.Dev:1.1) in the non-triple negative status patients and 2.6 (St. Dev:3.7) in the triple negative status patients (p=0.001). Using a cox proportional hazards model, it was found that whole brain radiotherapy does not significantly affect overall survival in patients with triple negative breast cancer (p = 0.96). Our findings highlight the highly aggressive intracranial nature of triple negative breast cancer. Indeed, the rate of increase in brain metastases is significantly higher for triple negative patients compared to non-triple negative patients. As a result, we evaluated whether triple negative patients would benefit from whole brain radiation regardless of findings on initial brain imaging. Despite 53% of patients receiving WBRT, our investigation found that there is no additional benefit to WBRT in triple negative breast cancer patients. These results suggest a need to re-evaluate the role of WBRT in the management of triple negative breast cancer.

High-dimensional Cytometry (ExCYT) and Mass Spectrometry of Myeloid Infiltrate in Clinically Localized Clear Cell Renal Cell Carcinoma Identifies Novel Potential Myeloid Targets for Immunotherapy

Although the focus of the role of cancer immunotherapy has been in advanced disease states, we sought to investigate changes to the immune infiltrate of early, clinically localized clear cell Renal Cell Carcinoma (ccRCC). Using orthogonal approaches including Mass Spectrometry on immune cell infiltrates, we report numerous alterations that provide new insight into the biology of treatment-naïve ccRCC and identification of novel targets that may prove to be clinically impactful.

Renal Cell Carcinoma (RCC) is one of the most commonly diagnosed cancers worldwide with research efforts dramatically improving understanding of the biology of the disease. To investigate the role of the immune system in treatment-naïve clear cell Renal Cell Carcinoma (ccRCC), we interrogated the immune infiltrate in patient-matched ccRCC tumor samples, benign normal adjacent tissue (NAT) and peripheral blood mononuclear cells (PBMCs isolated from whole blood, focusing our attention on the myeloid cell infiltrate. Using flow cytometric, MS, and ExCYT analysis, we discovered unique myeloid populations in PBMCs across patient samples. Furthermore, normal adjacent tissues and ccRCC tissues contained numerous myeloid populations with a unique signature for both tissues. Enrichment of the immune cell (CD45⁺) fraction and subsequent gene expression analysis revealed a number of myeloid-related genes that were differentially expressed. These data provide evidence, for the first time, of an immunosuppressive and pro-tumorigenic role of myeloid cells in early, clinically localized ccRCC. The identification of a number of immune proteins for therapeutic targeting provides a rationale for investigation into the potential efficacy of earlier intervention with single-agent or combination immunotherapy for ccRCC.

Asporin Restricts Mesenchymal Stromal Cell Differentiation, Alters the Tumor Microenvironment, and Drives Metastatic Progression

Tumor progression to metastasis is not cancer cell autonomous, but rather involves the interplay of multiple cell types within the tumor microenvironment. Here we identify asporin (ASPN) as a novel, secreted mesenchymal stromal cell (MSC) factor in the tumor microenvironment that regulates metastatic development. MSCs expressed high levels of ASPN, which decreased following lineage differentiation. ASPN loss impaired MSC self-renewal and promoted terminal cell differentiation. Mechanistically, secreted ASPN bound to BMP-4 and restricted BMP-4-induced MSC differentiation prior to lineage commitment. ASPN expression was distinctly conserved between MSC and cancer-associated fibroblasts (CAF). ASPN expression in the tumor microenvironment broadly impacted multiple cell types. Prostate tumor allografts in ASPN-null mice had a reduced number of tumor-associated MSCs, fewer cancer stem cells, decreased tumor vasculature, and an increased percentage of infiltrating CD8⁺ T cells. ASPN-null mice also demonstrated a significant reduction in lung metastases compared with wild-type mice. These data establish a role for ASPN as a critical MSC factor that extensively affects the tumor microenvironment and induces metastatic progression. SIGNIFICANCE: These findings show that asporin regulates key properties of mesenchymal stromal cells, including self-renewal and multipotency, and asporin expression by reactive stromal cells alters the tumor microenvironment and promotes metastatic progression.

ExCYT: A Graphical User Interface for Streamlining Analysis of High-Dimensional Cytometry Data

With the advent of flow cytometers capable of measuring an increasing number of parameters, scientists continue to develop larger panels to phenotypically explore characteristics of their cellular samples. However, these technological advancements yield high-dimensional data sets that have become increasingly difficult to analyze objectively within traditional manual-based gating programs. In order to better analyze and present data, scientists partner with bioinformaticians with expertise in analyzing high-dimensional data to parse their flow cytometry data. While these methods have been shown to be highly valuable in studying flow cytometry, they have yet to be incorporated in a straightforward and easy-to-use package for scientists who lack computational or programming expertise. To address this need, we have developed ExCYT, a MATLAB-based Graphical User Interface (GUI) that streamlines the analysis of high-dimensional flow cytometry data by implementing commonly employed analytical techniques for high-dimensional data including dimensionality reduction by t-SNE, a variety of automated and manual clustering methods, heatmaps, and novel high-dimensional flow plots. Additionally, ExCYT provides traditional gating options of select populations of interest for further t-SNE and clustering analysis as well as the ability to apply gates directly on t-SNE plots. The software provides the additional advantage of working with either compensated or uncompensated FCS files. In the event that post-acquisition compensation is required, the user can choose to provide the program a directory of single stains and an unstained sample. The program detects positive events in all channels and uses this select data to more objectively calculate the compensation matrix. In summary, ExCYT provides a comprehensive analysis pipeline to take flow cytometry data in the form of FCS files and allow any individual, regardless of computational training, to use the latest algorithmic approaches in understanding their data.

A mouse model for the study of transplanted bone marrow mesenchymal stem cell survival and proliferation in lumbar spinal fusion

PURPOSE

Bone marrow aspirate has been successfully used alongside a variety of grafting materials to clinically augment spinal fusion. However, little is known about the fate of these transplanted cells. Herein, we develop a novel murine model for the in vivo monitoring of implanted bone marrow cells (BMCs) following spinal fusion.

METHODS

A clinical-grade scaffold was implanted into immune-intact mice undergoing spinal fusion with or without freshly isolated BMCs from either transgenic mice which constitutively express the firefly luciferase gene or syngeneic controls. The in vivo survival, distribution and proliferation of these luciferase-expressing cells was monitored via bioluminescence imaging over a period of 8 weeks and confirmed via immunohistochemistry. MicroCT imaging was performed 8 weeks to assess fusion.

RESULTS

Bioluminescence imaging indicated transplanted cell survival and proliferation over the first 2 weeks, followed by a decrease in cell numbers, with transplanted cell survival still evident at the end of the study. New bone formation and increased fusion mass volume were observed in mice implanted with cell-seeded scaffolds.

CONCLUSIONS

By enabling the tracking of transplanted bone marrow-derived cells during spinal fusion in vivo, this mouse model will be integral to developing a deeper understanding of the biological processes underlying spinal fusion in future studies. These slides can be retrieved under Electronic Supplementary Material.

Expression of LAG-3 and efficacy of combination treatment with anti-LAG-3 and anti-PD-1 monoclonal antibodies in glioblastoma

Like in many tumor types, immunotherapy is currently under investigation to assess its potential efficacy in glioblastoma patients. Trials are under way to assess the efficacy of new immune checkpoint inhibitors including anti-PD-1 or CTLA4. We here investigate the expression and efficacy of a novel immune-checkpoint inhibitor, called LAG-3. We show that LAG-3 is expressed in human glioblastoma samples and in a mouse glioblastoma model we show that knock out or LAG-3 inhibition with a blocking antibody is efficacious against glioblastoma and can be used in combination with other immune checkpoint inhibitors toward complete eradication of the model glioblastoma tumors. From a mechanistic standpoint we show that LAG-3 expression is an early marker of T cell exhaustion and therefore early treatment with LAG-3 blocking antibody is more efficacious than later treatment. These data provide insight and support the design of trials that incorporate LAG-3 in the treatment of glioblastoma.

Contrasting impact of corticosteroids on anti-PD-1 immunotherapy efficacy for tumor histologies located within or outside the central nervous system

Immune checkpoint blockade targeting programmed cell death protein 1 (PD-1) is emerging as an important treatment strategy in a growing list of cancers, yet its clinical benefits are limited to a subset of patients. Further investigation of tumor-intrinsic predictors of response and how extrinsic factors, such as iatrogenic immunosuppression caused by conventional therapies, impact the efficacy of anti-PD-1 therapy are paramount. Given the widespread use of corticosteroids in cancer management and their immunosuppressive nature, this study sought to determine how corticosteroids influence anti-PD-1 responses and whether their effects were dependent on tumor location within the periphery versus central nervous system (CNS), which may have a more limiting immune environment. In well-established anti-PD-1-responsive murine tumor models, corticosteroid therapy resulted in systemic immune effects, including severe and persistent reductions in peripheral CD4+ and CD8 + T cells. Corticosteroid treatment was found to diminish the efficacy of anti-PD-1 therapy in mice bearing peripheral tumors with responses correlating with peripheral CD8/Treg ratio changes. In contrast, in mice bearing intracranial tumors, corticosteroids did not abrogate the benefits conferred by anti-PD-1 therapy. Despite systemic immune changes, anti-PD-1-mediated antitumor immune responses remained intact during corticosteroid treatment in mice bearing intracranial tumors. These findings suggest that anti-PD-1 responses may be differentially impacted by concomitant corticosteroid use depending on tumor location within or outside the CNS. As an immune-specialized site, the CNS may potentially play a protective role against the immunosuppressive effects of corticosteroids, thus sustaining antitumor immune responses mediated by PD-1 blockade.

Contrast-Enhanced CISS Imaging for Evaluation of Neurovascular Compression in Trigeminal Neuralgia: Improved Correlation with Symptoms and Prediction of Surgical Outcomes

BACKGROUND AND PURPOSE

Thin-section MR imaging through the posterior fossa is frequently used for trigeminal neuralgia. Typical heavily T2-weighted imaging methods yield high anatomic detail and contrast between CSF and neurovascular structures, but poor contrast between vessels and nerves. We hypothesized that the addition of gadolinium-based contrast material to 3D-constructive interference in steady-state imaging would improve the characterization of trigeminal compression.

MATERIALS AND METHODS

Retrospective review of high-resolution MRIs was performed in patients without prior microvascular decompression. 3D-CISS imaging without contrast and with contrast for 81 patients with trigeminal neuralgia and 15 controls was intermixed and independently reviewed in a blinded fashion. Cisternal segments of both trigeminal nerves were assessed for the grade of neurovascular conflict, cross-sectional area, and degree of flattening. Data were correlated with symptom side and pain relief after microvascular decompression using the Fisher exact test, receiver operating curve analysis, and a paired t test.

RESULTS

Contrast-enhanced CISS more than doubled the prevalence of the highest grade of neurovascular conflict (14.8% versus 33.3%, P = .001) and yielded significantly lower cross-sectional area (P = 8.6 × 10^-6) and greater degree of flattening (P = .02) for advanced-grade neurovascular conflict on the symptoms side compared with non-contrast-enhanced CISS. Patients with complete pain relief after microvascular decompression had significantly lower cross-sectional area on contrast-enhanced CISS compared with non-contrast-enhanced CISS on preoperative imaging (P = 2.0 × 10^-7). Performance based on receiver operating curve analysis was significantly improved for contrast-enhanced CISS compared with non-contrast-enhanced CISS.

CONCLUSIONS

The addition of contrast material to 3D-CISS imaging improves the performance of identifying unilateral neurovascular compression for symptomatic trigeminal neuralgia and predicting outcomes after microvascular decompression.

Elective Nodal Irradiation Attenuates the Combinatorial Efficacy of Stereotactic Radiation Therapy and Immunotherapy

Purpose: In the proper context, radiotherapy can promote antitumor immunity. It is unknown if elective nodal irradiation (ENI), a strategy that irradiates tumor-associated draining lymph nodes (DLN), affects adaptive immune responses and combinatorial efficacy of radiotherapy with immune checkpoint blockade (ICB).Experimental Design: We developed a preclinical model to compare stereotactic radiotherapy (Tumor RT) with or without ENI to examine immunologic differences between radiotherapy techniques that spare or irradiate the DLN.Results: Tumor RT was associated with upregulation of an intratumoral T-cell chemoattractant chemokine signature (CXCR3, CCR5-related) that resulted in robust infiltration of antigen-specific CD8⁺ effector T cells as well as FoxP3⁺ regulatory T cells (Tregs). The addition of ENI attenuated chemokine expression, restrained immune infiltration, and adversely affected survival when combined with ICB, especially with anti-CLTA4 therapy. The combination of stereotactic radiotherapy and ICB led to long-term survival in a subset of mice and was associated with favorable CD8 effector-to-Treg ratios and increased intratumoral density of antigen-specific CD8⁺ T cells. Although radiotherapy technique (Tumor RT vs. ENI) affected initial tumor control and survival, the ability to reject tumor upon rechallenge was partially dependent upon the mechanism of action of ICB; as radiotherapy/anti-CTLA4 was superior to radiotherapy/anti-PD-1.Conclusions: Our results highlight that irradiation of the DLN restrains adaptive immune responses through altered chemokine expression and CD8⁺ T-cell trafficking. These data have implications for combining radiotherapy and ICB, long-term survival, and induction of immunologic memory. Clinically, the immunomodulatory effect of the radiotherapy strategy should be considered when combining stereotactic radiotherapy with immunotherapy. Clin Cancer Res; 24(20); 5058-71. ©2018 AACR.

TIGIT and PD-1 dual checkpoint blockade enhances antitumor immunity and survival in GBM

The use of inhibitory checkpoint blockade in the management of glioblastoma has been studied in both preclinical and clinical settings. TIGIT is a novel checkpoint inhibitor recently discovered to play a role in cancer immunity. In this study, we sought to determine the effect of anti-PD-1 and anti-TIGIT combination therapy on survival in a murine glioblastoma (GBM) model, and to elucidate the underlying immune mechanisms. Using mice with intracranial GL261-luc⁺ tumors, we found that TIGIT expression was upregulated on CD8⁺ and regulatory T cells (Tregs) in the brain compared to draining cervical lymph nodes (CLN) and spleen. We then demonstrated that treatment using anti-PD-1 and anti-TIGIT dual therapy significantly improved survival compared to control and monotherapy groups. The therapeutic effect was correlated with both increased effector T cell function and downregulation of suppressive Tregs and tumor-infiltrating dendritic cells (TIDCs). Clinically, TIGIT expression on tumor-infiltrating lymphocytes was shown to be elevated in patient GBM samples, suggesting that the TIGIT pathway may be a valuable therapeutic target. Expression of the TIGIT ligand, PVR, further portended a poor survival outcome in patients with low-grade glioma. We conclude that anti-TIGIT is an effective treatment strategy against murine GBM when used in combination with anti-PD-1, improving overall survival via modifications of both the T cell and myeloid compartments. Given evidence of PVR expression on human GBM cells, TIGIT presents as a promising immune therapeutic target in the management of these patients.

TNFα and Radioresistant Stromal Cells Are Essential for Therapeutic Efficacy of Cyclic Dinucleotide STING Agonists in Nonimmunogenic Tumors

The cGAS-STING cytosolic DNA sensing pathway may play an integral role in the initiation of antitumor immune responses. Studies evaluating the immunogenicity of various cyclic dinucleotide (CDN) STING agonists administered by intratumoral (i.t.) injection showed potent induction of inflammation, tumor necrosis, and, in some cases, durable tumor-specific adaptive immunity. However, the specific immune mechanisms underlying these responses remain incompletely defined. The majority of these studies have focused on the effect of CDNs on immune cells but have not conclusively interrogated the role of stromal cells in the acute rejection of the CDN-injected tumor. Here, we revealed a mechanism of STING agonist-mediated tumor response that relied on both stromal and immune cells to achieve tumor regression and clearance. Using knockout and bone marrow chimeric mice, we showed that although bone marrow-derived TNFα was necessary for CDN-induced necrosis, STING signaling in radioresistant stromal cells was also essential for CDN-mediated tumor rejection. These results provide evidence for crosstalk between stromal and hematopoietic cells during CDN-mediated tumor collapse after i.t. administration. These mechanistic insights may prove critical in the clinical development of STING agonists. Cancer Immunol Res; 6(4); 422-33. ©2018 AACR.

Anti-PD-1 antitumor immunity is enhanced by local and abrogated by systemic chemotherapy in GBM

The immunosuppressive effects of chemotherapy present a challenge for designing effective cancer immunotherapy strategies. We hypothesized that although systemic chemotherapy (SC) exhibits negative immunologic effects, local chemotherapy (LC) can potentiate an antitumor immune response. We show that LC combined with anti-programmed cell death protein 1 (PD-1) facilitates an antitumor immune response and improves survival (P < 0.001) in glioblastoma. LC-treated mice had increased infiltration of tumor-associated dendritic cells and clonal expansion of antigen-specific T effector cells. In comparison, SC resulted in systemic and intratumoral lymphodepletion, with decreased immune memory in long-term survivors. Furthermore, adoptive transfer of CD8⁺ cells from LC-treated mice partially rescued SC-treated mice after tumor rechallenge. Last, the timing of chemo- and immunotherapy had differential effects on anti-PD-1 efficacy. This study suggests that both mode of delivery and timing have distinct effects on the efficacy of anti-PD-1. The results of this work could help guide the selection and scheduling of combination treatment for patients with glioblastoma and other tumor types.

Stereotactic Radiotherapy Increases Functionally Suppressive Regulatory T Cells in the Tumor Microenvironment

Radiotherapy (RT) enhances innate and adaptive antitumor immunity; however, the effects of radiation on suppressive immune cells, such as regulatory T cells (Treg), in the tumor microenvironment (TME) are not fully elucidated. Although previous reports suggest an increased Treg infiltration after radiation, whether these Tregs are functionally suppressive remains undetermined. To test the hypothesis that RT enhances the suppressive function of Treg in the TME, we selectively irradiated implanted tumors using the small animal radiation research platform (SARRP), which models stereotactic radiotherapy in human patients. We then analyzed tumor-infiltrating lymphocytes (TIL) with flow-cytometry and functional assays. Our data showed that RT significantly increased tumor-infiltrating Tregs (TIL-Treg), which had higher expression of CTLA-4, 4-1BB, and Helios compared with Tregs in nonirradiated tumors. This observation held true across several tumor models (B16/F10, RENCA, and MC38). We found that TIL-Tregs from irradiated tumors had equal or improved suppressive capacity compared with nonirradiated tumors. Our data also indicated that after RT, Tregs proliferated more robustly than other T-cell subsets in the TME. In addition, after RT, expansion of Tregs occurred when T-cell migration was inhibited using Fingolimod, suggesting that the increased Treg frequency was likely due to preferential proliferation of intratumoral Treg after radiation. Our data also suggested that Treg expansion after irradiation was independent of TGFβ and IL33 signaling. These data demonstrate that RT increased phenotypically and functionally suppressive Tregs in the TME. Our results suggest that RT might be combined effectively with Treg-targeting agents to maximize antitumor efficacy. Cancer Immunol Res; 5(11); 992-1004. ©2017 AACR.

Ultrasound for the assessment of distal shunt malfunction in adults with internal ventricular shunts

Shunts that are used for the treatment of hydrocephalus have a propensity towards malfunction, however, diagnosing a shunt malfunction can sometimes be a challenge. The purpose of this study was to investigate whether ultrasound technology can be safely and effectively used to assess for distal shunt malfunction. This was a prospective cohort study at a single institution. Eighteen adult patients that received a radionuclide shunt patency study also underwent an ultrasound shunt patency study. Ultrasound with Doppler technology was used to visualize flow through the shunt tubing following manual compression of the shunt reservoir. A peak flow speed was recorded and the results were compared to the results of the radionuclide shunt patency study. A Receiver Operating Characteristic (ROC) curve comparing the ultrasound to the radionuclide shunt patency study was generated, revealing an Area Under the Curve (AUC) of 0.95 (95% CI: 0.84-1.00). The ultrasound test performed maximally with a cutoff speed of ≤10cm/s as the criteria for malfunction, with a sensitivity of 100.00%, specificity of 90.91%, accuracy of 94.44%, positive likelihood ratio of 11.000 and negative likelihood ratio of 0.000 using the radionuclide study results as criteria for comparison. Overall, ultrasound has the potential to be a safe, quick, available and cost-effective screening test for patients with suspected distal shunt malfunction. The high sensitivity of the test makes it an attractive option for use as a screening method that could potentially reduce the number of cases requiring radionuclide shunt patency study.

Stereotactic radiotherapy increases functionally suppressive regulatory T cells in the tumor microenvironment

Radiotherapy (RT) enhances innate and adaptive anti-tumor immunity; however, the effects of RT on immune-suppressive regulatory T cells (Tregs), in the tumor microenvironment (TME) have not yet been fully elucidated. Although previous reports suggest a post-RT increase in Tregs, whether these Tregs are functionally suppressive has not been determined. To test the hypothesis that RT enhances the suppressive function of Tregs in the TME, we selectively irradiated implanted tumors using the Small Animal Radiation Research Platform (SARRP), which models stereotactic RT in human patients– followed by flow-cytometric and functional analyses of tumor-infiltrating lymphocytes (TIL). Our data showed that RT significantly increased tumor-infiltrating Tregs (TIL-Tegs), and that these cells have higher expression of CTLA-4, 4-1BB, and Helios, consistent with activated/suppressive phenotype. This observation held true across several tumor models (B16/F10, RENCA, MC38). Notably, we found that post-RT, TIL-Tregs had equal or improved suppressive capacity compared with non-irradiated tumors. Our data also indicated that Tregs proliferate post-RT, more robustly than the other T cell subsets in the TME. In addition, the post-RT Treg expansion occurred when T cell migration was inhibited by Fingolimod - suggesting that the post-RT Treg increase is likely due to preferential proliferation of intratumoral Tregs. Our data also suggest that post-RT Treg expansion is independent of TGF-β and IL-33. Collectively, these data demonstrate that RT increases the phenotypically and functionally suppressive Tregs in the TME, and provide a rationale for treatment regimens that combine RT with Treg-targeting agents to maximize anti-tumor efficacy.

Abstract PR03: Prophylactic nodal irradiation abrogates the synergy of tumor radiotherapy and immune checkpoint blockade

Background: Prophylactic nodal irradiation (PNI) is a strategy used to treat early stage cancers with the potential to enhance local control and prevent metastatic spread. It remains unclear whether irradiation of tumor-associated draining lymph nodes (LN) influences anti-tumor T cell responses. Our aim was to investigate the in vivo effects of nodal irradiation on the phenotype and function of tumor infiltrating lymphocytes (TIL) and the impact of PNI on the anti-tumor effects of immunotherapy.

Methods: The Small Animal Radiation Research Platform (SARRP) delivered imaged-guided stereotactic radiation (RT) to tumor (T-only) or tumor and LN (T+LN). Syngeneic tumors (MC38 colon, B16 melanoma) were implanted in C57BL/6 mice and irradiated (12Gy x1) and/or treated with immune checkpoint blockade with αCTLA-4 IgG2a (depleting) or αPD-1 IgG1. The composition of the tumor microenvironment (TME) was assayed by flow cytometry. To query tumor-antigen specific T cell responses, adoptive transfer experiments were performed using OVA-specific CD8+ T-cells from Rag-/- OT-1 mice and OVA-MHC class I tetramer (SIINFEKL). Tumor lysate was also collected for chemokine analysis, and tumor outgrowth was quantified over time.

Results: T-only RT resulted in a significant increase (P&lt;0.01) in the proportion and absolute number of tumor infiltrating CD8+ effector T cells in comparison with T+LN RT. Immunosuppressive subsets (CD11b+ Gr-1hi MDSCs and FoxP3+ CD4+ Tregs) were also significantly increased in the T-only group. Ultimately, T-only RT significantly enhanced the CD8 effector:Treg ratio relative to untreated and T+LN treated tumors. Using the OVA-MHC class I tetramer to identify tumor-antigen specific CD8 T-cells, we observed that T-only RT significantly increased (P&lt;0.05) the number of tumor-specific CD8-T cells in the TME compared with T+LN RT. Interestingly, T-only RT resulted in a a significant expansion of non-OVA specific CD8 T cells which was not observed with T+LN RT, suggesting a polyclonal anti-tumor immune response. Functionally, a significant increase (P&lt;0.01) in the absolute number of IFNγ+ and TNFα+ antigen-specific TIL were noted with T-only RT. Mechanistically, a distinct chemokine signature correlated with robust TME immune infiltration and significantly elevated levels of CCL3/4/5 and CXCL10 (P&lt;0.05) were observed in tumor lysate collected from T-only RT tumors relative to T+LN RT samples. In an effort to understand the implications of the RT target on potential synergy with immune checkpoint blockade we performed survival experiments with T-only and T+LN RT in combination with αPD-1 or αCTLA-4. T-only RT in combination with αCTLA-4 yielded the best outcome with a 86% long-term survival (day 90 post-RT) compared with 30-36% long-term survival in mice treated with other combinations of RT + immune checkpoint blockade. Intriguingly, favorable CD8 effector:Treg ratio was able to predict treatment response and was dramatically higher (P&lt;0.001) among mice treated with T-only RT in combination with αCTLA-4.

Conclusions: We have successfully developed a SARRP-based early stage cancer model with the ability to target or spare the tumor-associated LN. Results to date demonstrate significant immunological differences that are contingent upon inclusion/exclusion of the LN. Long-term survival experiments suggest response and survival advantages with T-only RT, particularly in combination with αCTLA-4 blockade. Taken together, these data suggest that PNI may dampen anti-tumor immune responses and that Tumor-only RT might be a better strategy in combination immunotherapy regimens, although these results should be explored in carefully designed clinical trials.

This abstract is also being presented as Poster B41.

Citation Format: Ariel E. Marciscano, Ali Ghasemzadeh, Thomas R. Nirschl, Brian J. Francica, Debebe Theodros, Esteban Velarde, J Wong, Daniel LJ Thorek, Theodore L. DeWeese, Charles G. Drake. Prophylactic nodal irradiation abrogates the synergy of tumor radiotherapy and immune checkpoint blockade. [abstract]. In: Proceedings of the AACR Special Conference on Tumor Immunology and Immunotherapy; 2016 Oct 20-23; Boston, MA. Philadelphia (PA): AACR; Cancer Immunol Res 2017;5(3 Suppl):Abstract nr PR03.

Efficacy of primary microvascular decompression versus subsequent microvascular decompression for trigeminal neuralgia

OBJECTIVE Trigeminal neuralgia (TN) is characterized by intermittent, paroxysmal, and lancinating pain along the distribution of the trigeminal nerve. Microvascular decompression (MVD) directly addresses compression of the trigeminal nerve. The purpose of this study was to determine whether patients undergoing MVD as their first surgical intervention experience greater pain control than patients who undergo subsequent MVD. METHODS A retrospective review of patient records from 1998 to 2015 identified a total of 942 patients with TN and 500 patients who underwent MVD. After excluding several cases, 306 patients underwent MVD as their first surgical intervention and 175 patients underwent subsequent MVD. Demographics and clinicopathological data and outcomes were obtained for analysis. RESULTS In patients who underwent subsequent MVD, surgical intervention was performed at an older age (55.22 vs 49.98 years old, p < 0.0001) and the duration of symptoms was greater (7.22 vs 4.45 years, p < 0.0001) than for patients in whom MVD was their first surgical intervention. Patients who underwent initial MVD had improved pain relief and no improvement in pain rates compared with those who had subsequent MVD (95.8% and 4.2% vs 90.3% and 9.7%, respectively, p = 0.0041). Patients who underwent initial MVD had significantly lower rates of facial numbness in the pre- and postoperative periods compared with patients who underwent subsequent MVD (p < 0.0001). The number of complications in both groups was similar (p = 0.4572). CONCLUSIONS The results demonstrate that patients who underwent other procedures prior to MVD had less pain relief and a higher incidence of facial numbness despite rates of complications similar to patients who underwent MVD as their first surgical intervention.

High-Resolution MRI Findings following Trigeminal Rhizotomy

BACKGROUND AND PURPOSE

Patients with trigeminal neuralgia often undergo trigeminal rhizotomy via radiofrequency thermocoagulation or glycerol injection for treatment of symptoms. To date, radiologic changes in patients with trigeminal neuralgia post-rhizotomy have not been described, to our knowledge. The aim of this study was to evaluate patients after trigeminal rhizotomy to characterize post-rhizotomy changes on 3D high-resolution MR imaging.

MATERIALS AND METHODS

A retrospective review of trigeminal neuralgia protocol studies was performed in 26 patients after rhizotomy compared with 54 treatment-naïve subjects with trigeminal neuralgia. Examinations were reviewed independently by 2 neuroradiologists blinded to the side of symptoms and treatment history. The symmetry of Meckel's cave on constructive interference in steady-state and the presence of contrast enhancement within the trigeminal nerves on volumetric interpolated breath-hold examination images were assessed subjectively. The signal intensity of Meckel's cave was measured on coronal noncontrast constructive interference in steady-state imaging on each side.

RESULTS

Post-rhizotomy changes included subjective clumping of nerve roots and/or decreased constructive interference in steady-state signal intensity within Meckel's cave, which was identified in 17/26 (65%) patients after rhizotomy and 3/54 (6%) treatment-naïve patients (P < .001). Constructive interference in steady-state signal intensity within Meckel's cave was, on average, 13% lower on the side of the rhizotomy in patients posttreatment compared with a 1% difference in controls (P < .001). Small regions of temporal encephalomalacia were noted in 8/26 (31%) patients after rhizotomy and 0/54 (0%) treatment-naïve patients (P < .001).

CONCLUSIONS

Post-trigeminal rhizotomy findings frequently include nerve clumping and decreased constructive interference in steady-state signal intensity in Meckel's cave. Small areas of temporal lobe encephalomalacia are encountered less frequently.

Combination Therapy with Anti-PD-1, Anti-TIM-3, and Focal Radiation Results in Regression of Murine Gliomas

PURPOSE

Checkpoint molecules like programmed death-1 (PD-1) and T-cell immunoglobulin mucin-3 (TIM-3) are negative immune regulators that may be upregulated in the setting of glioblastoma multiforme. Combined PD-1 blockade and stereotactic radiosurgery (SRS) have been shown to improve antitumor immunity and produce long-term survivors in a murine glioma model. However, tumor-infiltrating lymphocytes (TIL) can express multiple checkpoints, and expression of ≥2 checkpoints corresponds to a more exhausted T-cell phenotype. We investigate TIM-3 expression in a glioma model and the antitumor efficacy of TIM-3 blockade alone and in combination with anti-PD-1 and SRS.

EXPERIMENTAL DESIGN

C57BL/6 mice were implanted with murine glioma cell line GL261-luc2 and randomized into 8 treatment arms: (i) control, (ii) SRS, (iii) anti-PD-1 antibody, (iv) anti-TIM-3 antibody, (v) anti-PD-1 + SRS, (vi) anti-TIM-3 + SRS, (vii) anti-PD-1 + anti-TIM-3, and (viii) anti-PD-1 + anti-TIM-3 + SRS. Survival and immune activation were assessed.

RESULTS

Dual therapy with anti-TIM-3 antibody + SRS or anti-TIM-3 + anti-PD-1 improved survival compared with anti-TIM-3 antibody alone. Triple therapy resulted in 100% overall survival (P < 0.05), a significant improvement compared with other arms. Long-term survivors demonstrated increased immune cell infiltration and activity and immune memory. Finally, positive staining for TIM-3 was detected in 7 of 8 human GBM samples.

CONCLUSIONS

This is the first preclinical investigation on the effects of dual PD-1 and TIM-3 blockade with radiation. We also demonstrate the presence of TIM-3 in human glioblastoma multiforme and provide preclinical evidence for a novel treatment combination that can potentially result in long-term glioma survival and constitutes a novel immunotherapeutic strategy for the treatment of glioblastoma multiforme. Clin Cancer Res; 23(1); 124-36. ©2016 AACR.

Agonist anti-GITR monoclonal antibody and stereotactic radiation induce immune-mediated survival advantage in murine intracranial glioma

Background

Glioblastoma (GBM) is a poorly immunogenic neoplasm treated with focused radiation. Immunotherapy has demonstrated synergistic survival effects with stereotactic radiosurgery (SRS) in murine GBM. GITR is a co-stimulatory molecule expressed constitutively on regulatory T-cells and by effector T-cells upon activation. We tested the hypothesis that anti-GITR monoclonal antibody (mAb) and SRS together would confer an immune-mediated survival benefit in glioma using the orthotopic GL261 glioma model.

Methods

Mice received SRS and anti-GITR 10 days after implantation. The anti-GITR mAbs tested were formatted as mouse IgG1 D265A (anti-GITR (1)) and IgG2a (anti-GITR (2a)) isotypes. Mice were randomized to four treatment groups: (1) control; (2) SRS; (3) anti-GITR; (4) anti-GITR/SRS. SRS was delivered to the tumor in one fraction, and mice were treated with mAb thrice. Mice were euthanized on day 21 to analyze the immunologic profile of tumor, spleen, and tumor draining lymph nodes.

Results

Anti-GITR (1)/SRS significantly improved survival over either treatment alone (p < .0001) with a cure rate of 24 % versus 0 % in a T-lymphocyte-dependent manner. There was elevated intratumoral CD4+ effector cell infiltration relative to Treg infiltration in mice treated with anti-GITR (1)/SRS, as well as significantly elevated IFNγ and IL-2 production by CD4+ T-cells and elevated IFNγ and TNFα production by CD8+ T-cells. There was increased mRNA expression of M1 markers and decreased expression of M2 markers in tumor infiltrating mononuclear cells. The anti-GITR (2a)/SRS combination did not improve survival, induce tumor regression, or result in Treg depletion.

Conclusions

These findings provide preclinical evidence for the use of anti-GITR (1) non-depleting antibodies in combination with SRS in GBM.

Electronic supplementary material

The online version of this article (doi:10.1186/s40425-016-0132-2) contains supplementary material, which is available to authorized users.

Pituitary adenomas: historical perspective, surgical management and future directions

Pituitary adenomas are among the most common central nervous system tumors. They represent a diverse group of neoplasms that may or may not secrete hormones based on their cell of origin. Epidemiologic studies have documented the incidence of pituitary adenomas within the general population to be as high as 16.7%. A growing body of work has helped to elucidate the pathogenesis of these tumors. Each subtype has been shown to demonstrate unique cellular changes potentially leading to tumorigenesis. Surgical advancements over several decades have included microsurgery and the employment of the endoscope for surgical resection. These advancements increase the likelihood of gross-total resection and have resulted in decreased patient morbidity.

Reduced CSF leak in complete calvarial reconstructions of microvascular decompression craniectomies using calcium phosphate cement

OBJECT

Calcium phosphate cement provides a biomaterial that can be used for calvarial reconstruction in a retrosigmoid craniectomy for microvascular decompression (MVD). This study evaluates the outcomes of postoperative CSF leak and wound infection for patients undergoing a complete cranioplasty using calcium phosphate cement versus incomplete cranioplasty using polyethylene titanium mesh following a retrosigmoid craniectomy for MVD.

METHODS

The authors evaluated 211 cases involving patients who underwent first-time retrosigmoid craniectomies performed by a single attending surgeon fortrigeminal neuralgia from October 2008 to June 2014. From this patient population, 111 patients underwent calvarial reconstruction after retrosigmoid craniectomy using polyethylene titanium mesh, and 100 patients had reconstructions using calcium phosphate cement. A Pearson's chi-square test was used to compare postoperative complications of CSF leak and wound infection in these 2 types of cranioplasties.

RESULTS

The polyethylene titanium mesh group included 5 patients (4.5%) with postoperative CSF leak or pseudomeningocele and 3 patients (2.7%) with wound infections. In the calcium phosphate cement group, no patients had a CSF leak, and 2 patients (2%) had wound infections. This represented a statistically significant reduction of postoperative CSF leak in patients who underwent calcium phosphate reconstructions of their calvarial defect compared with those who underwent polyethylene titanium mesh reconstructions (p = 0.03). No significant difference was seen between the 2 groups in the number of patients with postoperative wound infections.

CONCLUSIONS

Calcium phosphate cement provides a viable alternative biomaterial for calvarial reconstruction of retrosigmoid craniectomy defects in patients who have an MVD. The application of this material provides a biocompatible barrier that reduces the incidence of postoperative CSF leaks.