PD-L1 blockade enhances response of pancreatic ductal adenocarcinoma to radiotherapy

Pancreatic ductal adenocarcinoma (PDAC) is considered a non‐immunogenic tumor, and immune checkpoint inhibitor monotherapy lacks efficacy in this disease. Radiotherapy (RT) can stimulate the immune system. Here, we show that treatment of KPC and Pan02 murine PDAC cells with RT and gemcitabine upregulated PD‐L1 expression in a JAK/Stat1‐dependent manner. In vitro, PD‐L1 inhibition did not alter radio‐ and chemosensitivity. In vivo, addition of anti‐PD‐L1 to high (12, 5 × 3, 20 Gy) but not low (6, 5 × 2 Gy) RT doses significantly improved tumor response in KPC and Pan02 allografts. Radiosensitization after PD‐L1 blockade was associated with reduced CD11b+Gr1+ myeloid cell infiltration and enhanced CD45+CD8+ T‐cell infiltration with concomitant upregulation of T‐cell activation markers including CD69, CD44, and FasL, and increased CD8:Treg ratio. Depletion of CD8+ T cells abrogated radiosensitization by anti‐PD‐L1. Blockade of PD‐L1 further augmented the effect of high RT doses (12 Gy) in preventing development of liver metastases. Exploring multiple mathematical models reveals a mechanism able to explain the observed synergy between RT and anti‐PD‐L1 therapy. Our findings provide a rationale for testing the use of immune checkpoint inhibitors with RT in PDAC

Improving Colorectal Cancer Screening Rates in Patients Referred to a Gastroenterology Clinic

Colorectal cancer (CRC) is the third most common cancer and the second leading cause of cancer-related death in the United States. Colonoscopy and fecal immunochemistry testing (FIT) are the primary recommended CRC screening modalities. The purpose of this study is to improve rates of CRC screening in Veterans and County hospital patients referred to gastroenterology fellow's clinics. A total of 717 patients between ages of 49 and 75 years were seen. Previous CRC screening was not performed in 109 patients (15.2%) because of not being offered (73.4%) or declining (26.6%) screening. Patients who received previous CRC screening compared with no previous screening were older (mean age 62.3 years vs. 60.3 years, p < .003), white (88.6% vs. 78.3%, p < .027), and more likely to be Veterans patients (90.8% vs. 77.5%, p < .001). After systematically discussing options for screening with 78 of the 109 unscreened patients, 56 of them (71.8%) underwent screening with either colonoscopy (32) or FIT (24). Patients seen by fellows in their last year of training agreed to undergo screening more often than those seen by other fellows (100% vs. 66.2%, p < .033). Systematic discussions about both colonoscopy and FIT can improve the overall rates of CRC screening

Racial Disparities in Liver Transplantation for Hepatocellular Carcinoma Are Not Explained by Differences in Comorbidities, Liver Disease Severity, or Tumor Burden

Black patients have higher mortality and are less likely to receive liver transplantation for hepatocellular carcinoma (HCC) than white patients. Reasons for these disparities have not been fully elucidated. Comorbid disease, liver disease severity, cirrhosis etiologies, and tumor characteristics were compared between black and white patients with HCC seen at the Indiana University Academic Medical Center from January 2000 to June 2014. Logistic regression was used to investigate the primary outcome, which was liver transplantation. Log-rank testing was used to compare survival between the two groups. Subgroup analysis explored reasons for failure to undergo liver transplantation in patients within Milan criteria. The cohort included 1,032 (86%) white and 164 (14%) black patients. Black and white patients had similar Model for End-Stage Liver Disease (MELD) and Child-Pugh scores (CPSs). There was a trend toward larger tumor size (5.3 cm versus 4.7 cm; P = 0.05) in black patients; however, Barcelona Clinic Liver Cancer (BCLC) staging and Milan criteria were similar. Black patients were less likely to undergo liver transplantation than white patients; this was a disparity that was not attenuated (odds ratio [OR], 0.43; 95% confidence interval [CI], 0.21-0.90) on multivariable analysis. Substance abuse was more frequently cited as the reason black patients within Milan criteria failed to undergo transplantation compared to white patients. Survival was similar between the two groups. Conclusion: Racial differences in patient and tumor characteristics were small and did not explain the disparity in liver transplantation. Higher rates of substance abuse in black patients within Milan criteria who failed to undergo transplantation suggest social factors contribute to this disparity in this cohort

Older Age and Disease Duration Are Highly Associated with Hepatocellular Carcinoma in Patients with Autoimmune Hepatitis

Background: Hepatocellular carcinoma (HCC) is rare in patients with autoimmune hepatitis (AIH). However, the overall burden of AIH cirrhosis in causing HCC and patients' risk factors are not well understood. Aims: To characterize the proportion of HCC linked to AIH at a large academic health center, and to identify variables associated with HCC in patients with AIH in a case-control study design. Methods: Over a 14.5-year period, medical records of all patients with HCC were reviewed. Cases are AIH patients identified from the cohort, and controls are patients with AIH without HCC. Three controls were randomly chosen from the Genetic Repository of Autoimmune Liver Disease and Coexisting Exposures database for each eligible case. Results: Out of 1250 eligible patients, 20 were linked to AIH (1.6%). Their median age was 64 years, 40% men and 100% Caucasian. Ten percent of AIH patients did not have evidence of cirrhosis at HCC diagnosis. The proportion of HCCs due to AIH decreased during the time intervals of the study. Compared to controls, cases were more likely men (40.0% vs. 18%, p = 0.049), with longer AIH duration (median 16 years vs. 5 years, p = 0.004). Prolonged AIH duration (OR 1.68, p = 0.006) and older age (OR 1.15, p = 0.049) were risk factors for HCC. Conclusions: AIH is a rare cause (1.6%) for HCC in Midwestern USA with a decreasing trend over 14.5 years. Ten percent of AIH-HCC patients did not have cirrhosis at time of HCC diagnosis. Patients with prolonged duration of the disease and older age are at high risk to develop HCC

Gemcitabine-induced TIMP1 attenuates therapy response and promotes tumor growth and liver metastasis in pancreatic cancer

Gemcitabine constitutes one of the backbones for chemotherapy treatment in pancreatic ductal adenocarcinoma (PDAC), but patients often respond poorly to this agent. Molecular markers downstream of gemcitabine treatment in preclinical models may provide an insight into resistance mechanisms. Using cytokine arrays, we identified potential secretory biomarkers of gemcitabine resistance (response) in the transgenic KRasG12D; Trp53R172H; Pdx-1 Cre (KPC) mouse model of PDAC. We verified the oncogenic role of the cytokine tissue inhibitor of matrix metalloproteinases 1 (TIMP1) in primary pancreatic tumors and metastases using both in vitro techniques and animal models. We identified potential pathways affected downstream of TIMP1 using the Illumina Human H12 array. Our findings were validated in both primary and metastatic models of pancreatic cancer. Gemcitabine increased inflammatory cytokines including TIMP1 in the KPC mouse model. TIMP1 was upregulated in patients with pancreatic intraepithelial neoplasias grade 3 and PDAC lesions relative to matched normal pancreatic tissue. In addition, TIMP1 played a role in tumor clonogenic survival and vascular density, while TIMP1 inhibition resensitized tumors to gemcitabine and radiotherapy. We observed a linear relationship between TIMP-1 expression, liver metastatic burden, and infiltration by CD11b+Gr1+ myeloid cells and CD4+CD25+FOXP3+ Tregs, whereas the presence of tumor cells was required for immune cell infiltration. Overall, our results identify TIMP1 upregulation as a resistance mechanism to gemcitabine and provide a rationale for combining chemo/radiotherapy with TIMP1 inhibitors in PDAC

Radiation combined with macrophage depletion promotes adaptive immunity and potentiates checkpoint blockade

Emerging evidence suggests a role for radiation in eliciting anti-tumour immunity. We aimed to investigate the role of macrophages in modulating the immune response to radiation. Irradiation to murine tumours generated from colorectal (MC38) and pancreatic (KPC) cell lines induced colony-stimulating factor 1 (CSF-1). Coincident with the elevation in CSF-1, macrophages increased in tumours, peaking 5 days following irradiation. These tumour-associated macrophages (TAMs) were skewed towards an immunosuppressive phenotype. Macrophage depletion via anti-CSF (aCSF) reduced macrophage numbers, yet only achieved tumour growth delay when combined with radiation. The tumour growth delay from aCSF after radiation was abrogated by depletion of CD8 T cells. There was enhanced recognition of tumour cell antigens by T cells isolated from irradiated tumours, consistent with increased antigen priming. The addition of anti-PD-L1 (aPD-L1) resulted in improved tumour suppression and even regression in some tumours. In summary, we show that adaptive immunity induced by radiation is limited by the recruitment of highly immunosuppressive macrophages. Macrophage depletion partly reduced immunosuppression, but additional treatment with anti-PD-L1 was required to achieve tumour regression

Targeted irradiation in an autochthonous mouse model of pancreatic cancer

The value of radiotherapy in the treatment of pancreatic cancer has been the subject of much debate but limited preclinical research. We hypothesise that the poor translation of radiation research into clinical trials of radiotherapy in pancreatic cancer is due, in part, to inadequate preclinical study models. Here, we have developed and refined methods for targeted irradiation in autochthonous mouse models of pancreatic cancer, using a small animal radiotherapy research platform. We tested and optimised strategies for administration of contrast agents, iohexol and the liver imaging agent Fenestra LC, to enable the use of computed tomography imaging in tumour localisation. We demonstrate accurate tumour-targeting, negligible off-target effects, and therapeutic efficacy, depending on dose, number of fractions and tumour size, and provide proof-of-concept that precise radiation can be delivered effectively to mouse pancreatic tumours with a clinically relevant microenvironment. This advance will allow investigation of the radiation response in murine pancreatic cancer, discovery of mechanisms and biomarkers of radiosensitivity or resistance, and development of radiosensitising strategies to inform clinical trials for precision radiotherapy in this disease