Expression of arginase I in myeloid cells limits control of residual disease after radiation therapy of tumors in mice

An accumulating body of evidence demonstrates that radiation therapy can generate adaptive immune responses that contribute to tumor control. However, in the absence of additional immune therapy, the adaptive immune response is insufficient to prevent tumor recurrence or affect distant disease. It has been shown in multiple models that tumor-infiltrating myeloid cells exhibit alternative activation phenotypes and are able to suppress adaptive immune responses, and recent data suggests that the myeloid response in tumors treated with cytotoxic therapy limits tumor control. We hypothesized that tumor myeloid cells inhibit the adaptive immune response after radiation therapy through expression of the enzyme arginase I. Using a myeloid cell-specific deletion of arginase I in mice, we demonstrate an improved tumor control after radiation therapy. However, tumors still recurred despite the conditional knockdown of arginase I. Since multiple alternative factors may combine to inhibit adaptive immunity, we propose that targeting macrophage differentiation may be a more effective strategy than targeting individual suppressive pathways

Transcriptional and immunohistological assessment of immune infiltration in pancreatic cancer.

Pancreatic adenocarcinoma is characterized by a complex tumor environment with a wide diversity of infiltrating stromal and immune cell types that impact the tumor response to conventional treatments. However, even in this poorly responsive tumor the extent of T cell infiltration as determined by quantitative immunohistology is a candidate prognostic factor for patient outcome. As such, even more comprehensive immunophenotyping of the tumor environment, such as immune cell type deconvolution via inference models based on gene expression profiling, holds significant promise. We hypothesized that RNA-Seq can provide a comprehensive alternative to quantitative immunohistology for immunophenotyping pancreatic cancer. We performed RNA-Seq on a prospective cohort of pancreatic tumor specimens and compared multiple approaches for gene expression-based immunophenotyping analysis compared to quantitative immunohistology. Our analyses demonstrated that while gene expression analyses provide additional information on the complexity of the tumor immune environment, they are limited in sensitivity by the low overall immune infiltrate in pancreatic cancer. As an alternative approach, we identified a set of genes that were enriched in highly T cell infiltrated pancreatic tumors, and demonstrate that these can identify patients with improved outcome in a reference population. These data demonstrate that the poor immune infiltrate in pancreatic cancer can present problems for analyses that use gene expression-based tools; however, there remains enormous potential in using these approaches to understand the relationships between diverse patterns of infiltrating cells and their impact on patient treatment outcomes

Expression of NF-κB p50 in Tumor Stroma Limits the Control of Tumors by Radiation Therapy

Radiation therapy aims to kill cancer cells with a minimum of normal tissue toxicity. Dying cancer cells have been proposed to be a source of tumor antigens and may release endogenous immune adjuvants into the tumor environment. For these reasons, radiation therapy may be an effective modality to initiate new anti-tumor adaptive immune responses that can target residual disease and distant metastases. However, tumors engender an environment dominated by M2 differentiated tumor macrophages that support tumor invasion, metastases and escape from immune control. In this study, we demonstrate that following radiation therapy of tumors in mice, there is an influx of tumor macrophages that ultimately polarize towards immune suppression. We demonstrate using in vitro models that this polarization is mediated by transcriptional regulation by NFκB p50, and that in mice lacking NFκB p50, radiation therapy is more effective. We propose that despite the opportunity for increased antigen-specific adaptive immune responses, the intrinsic processes of repair following radiation therapy may limit the ability to control residual disease

Analysis of 340 Patients with Solid Pseudopapillary Tumors of the Pancreas: A Closer Look at Patients with Metastatic Disease.

INTRODUCTION: Current literature addressing the treatment of solid pseudopapillary neoplasms (SPNs) of the pancreas is limited, particularly for patients with distant metastases. We aimed to define predictive indicators of survival in a large series of patients and assess the outcome of patients with distant metastases. METHODS: The National Cancer Database was queried for patients diagnosed with SPNs of the pancreas between 1998 and 2011. Single predictor univariate analyses were performed on variables including demographics, tumor characteristics, and surgery outcomes, and multivariate Cox proportional hazards survival analysis was then completed with backward elimination. RESULTS: Overall, 340 patients were identified: 82% were female, median age was 39 years, and 84% had no comorbidities. Patients undergoing any type of surgical resection experienced long-term survival (85% 8-year survival). Patients undergoing surgical resection (n = 296) had superior survival (hazard ratio [HR] 21 for no surgery, p \u3c 0.0001), as did patients treated at academic centers and those with private insurance (HR 3.9, p = 0.009; HR 4.9, p = 0.007). Sex, age, tumor size, presence of lymph node metastases, positive surgical margins, and presence of distant metastases were not significant predictors of survival in multivariate analysis. Of 24 patients with distant metastases, seven were treated surgically and experienced long-term survival similar to that of patients without metastases treated surgically (HR 2, p = 0.48). CONCLUSION: SPNs of the pancreas are rare neoplasms with excellent overall survival; however, in a low number of patients they metastasize. Of the few patients with metastatic disease selected for resection, most experienced long-term survival

Radiation therapy of tumors.

<p>a) C57BL/6 mice were challenged with 2×10⁵ Panc02 <i>s.c.</i> in the right leg and mice received 3 daily doses of 20 Gy focal radiation to the leg beginning on day 14 (RT) or were left untreated (NT). i-ii) 1 day or iii-iv) 7 days following the final radiation dose, tumors were harvested, digested and clonogenic assays performed. b) One and seven days following the final radiation dose, tumors were harvested and tumor-infiltrating cells determined by FACS analysis. Graphs show the mean and standard error of tumor infiltrating CD11b⁺ cells in Panc02 tumors, and include data from two replicate experiments. c) Panc02 tumors were harvested for histology 7 days following the final radiation dose. Images show representative regions of neighboring sections from tumors receiving NT (i & iii) or RT (ii & iv) that were i-ii) H&E stained or iii-iv) underwent immunofluorescence staining with antibodies specific for VWF and F4/80, and detected with antibodies conjugated to AF488 (Green) and AF568 (Red), respectively. Nuclear material was counterstained with DAPI (Blue) and sections were imaged by confocal microscopy.</p