Induction of cancer neoantigens facilitates development of clinically relevant models for the study of pancreatic cancer immunobiology.

Neoantigen burden and CD8 T cell infiltrate are associated with clinical outcome in pancreatic ductal adenocarcinoma (PDAC). A shortcoming of many genetic models of PDAC is the lack of neoantigen burden and limited T cell infiltrate. The goal of the present study was to develop clinically relevant models of PDAC by inducing cancer neoantigens in KP2, a cell line derived from the KPC model of PDAC. KP2 was treated with oxaliplatin and olaparib (OXPARPi), and a resistant cell line was subsequently cloned to generate multiple genetically distinct cell lines (KP2-OXPARPi clones). Clones A and E are sensitive to immune checkpoint inhibition (ICI), exhibit relatively high T cell infiltration, and have significant upregulation of genes involved in antigen presentation, T cell differentiation, and chemokine signaling pathways. Clone B is resistant to ICI and is similar to the parental KP2 cell line in terms of relatively low T cell infiltration and no upregulation of genes involved in the pathways noted above. Tumor/normal exome sequencing and in silico neoantigen prediction confirms successful generation of cancer neoantigens in the KP2-OXPARPi clones and the relative lack of cancer neoantigens in the parental KP2 cell line. Neoantigen vaccine experiments demonstrate that a subset of candidate neoantigens are immunogenic and neoantigen synthetic long peptide vaccines can restrain Clone E tumor growth. Compared to existing models, the KP2-OXPARPi clones better capture the diverse immunobiology of human PDAC and may serve as models for future investigations in cancer immunotherapies and strategies targeting cancer neoantigens in PDAC.

Cause and outcome of aborting a difficult laparoscopic cholecystectomy due to severe inflammation: a study of operative notes.

BACKGROUND: Upon encountering a difficult cholecystectomy in which, after a reasonable trial of dissection, anatomical identification has not been attained due to severe inflammation, and the risk of additional dissection is deemed to be hazardous, "bail-out" strategies are encouraged safety valves. One strategy is to abort the cholecystectomy and refer the patient to a HPB center for further management. METHODS: A retrospective review was conducted of cholecystectomies performed by HPB surgeons at our center between 2005 and 2019. We identified 63 patients who had an aborted cholecystectomy because of acute or chronic cholecystitis and were referred for additional care. Of these, operative notes and other clinical records were available for 43 patients who were included in this study. RESULTS: 42 cholecystectomies (98%) were started laparoscopically. 25 patients (58%) had chronic cholecystitis, and 18 (42%) had acute cholecystitis. 40 cases (93%) fell into the highest level of difficulty on the Nassar scale (Grade 4). Procedures were aborted at the following stages of dissection: in 10 patients (23%), none of the gallbladder was identified; in another 11 (26%), only the dome of gallbladder was identified; the body of the gallbladder was exposed in 13 (30%); and dissection of the hepatocystic triangle was attempted unsuccessfully in 9 (21%). Following referral to our center, 30 patients (70%) were managed with total cholecystectomy while in 13 cases (30%), subtotal cholecystectomy was performed. CONCLUSION: Aborting cholecystectomy and referring the patient to an HPB center is rarely needed but is an effective bail-out strategy for general surgeons encountering highly difficult operative conditions due to inflammation.

Re-defining a high volume center for pancreaticoduodenectomy.

BACKGROUND: The purpose of this study was to re-evaluate the previously utilized definitions of high volume center for pancreaticoduodenectomy to determine/establish an objective, evidence based threshold of hospital volume associated with improvement in perioperative mortality. METHODS: Patients who underwent pancreaticoduodenectomy were identified using the National Cancer Database from 2004 to 2015. The relationship between hospital volume and 90-day mortality was assessed using a logistic regression model. Receiver Operator Characteristic analysis was performed and Youden's statistic was utilized to calculate the optimal cut offs. RESULTS: 42,402 patients underwent elective Pancreaticoduodenectomy at 1238 unique hospitals. A logistic regression was performed which showed a significant inverse linear association between institutional volume and overall 90 day mortality. The maximum improvement in 90 day mortality is seen if the average annual hospital volume was greater than 9 (OR = 0.647 (0.595-0.702), p < 0.0001). When analysis is limited to hospitals that performed >9 cases per year, the maximum improvement in 90 day mortality was noticed at 36 cases per year (OR = 0.458 (0.399-0.525), p < 0.0001). CONCLUSIONS: Based on our results, we recommend defining low, medium, and high volume centers for pancreaticoduodenectomy as hospitals with average annual volume less than 9, 9 to 35, and more than 35 cases per year, respectively.

Sequential histologic evolution of gallbladder inflammation in acute cholecystitis over the first 10 days after onset of symptoms.

BACKGROUND: The timing of cholecystectomy during acute cholecystitis (AC) is controversial, especially whether it is advisable to perform in patients with duration of symptoms between 3 and 10 days. The purpose of this study is to define clearly the sequential evolution of histological changes following symptoms onset to guide recommendations regarding timing of cholecystectomy. METHODS: We identified patients with AC (2005-2018) who had cholecystectomy within 10 days of symptom onset of a first attack of AC. Histologic features of gallbladder injury including cellular and exudative inflammatory response to injury were determined on blinded pathologic slides. RESULTS: One hundred and forty-nine patients were divided into three groups; early-who underwent cholecystectomy 1-3 days after symptom-onset, intermediate-4-6 days, and late-7-10 days. Key features of injury were necrosis and hemorrhage. A subgroup of patients in the early phase developed severe necrosis and hemorrhage of an extent associated with difficult cholecystectomy. Large spikes in extent of necrosis and hemorrhage occurred at 7-10 days. Major inflammatory responses to injury were eosinophilic and lymphocytic infiltration and early fibrosis. CONCLUSIONS: Severe necrosis may develop rapidly and be present in the early period after symptom onset of AC. Cholecystectomy may be reasonable in some patients but by day 7-10, severe necrosis and hemorrhage may be expected to be present in most patients.

Systemic Alterations in Type-2 Conventional Dendritic Cells Lead to Impaired Tumor Immunity in Pancreatic Cancer.

Intratumoral T-cell dysfunction is a hallmark of pancreatic tumors, and efforts to improve dendritic cell (DC)-mediated T-cell activation may be critical in treating these immune therapy unresponsive tumors. Recent evidence indicates that mechanisms that induce dysfunction of type 1 conventional DCs (cDC1) in pancreatic adenocarcinomas (PDAC) are drivers of the lack of responsiveness to checkpoint immunotherapy. However, the impact of PDAC on systemic type 2 cDC2 development and function has not been well studied. Herein, we report the analysis of 3 cohorts, totaling 106 samples, of human blood and bone marrow (BM) from patients with PDAC for changes in cDCs. We found that circulating cDC2s and their progenitors were significantly decreased in the blood of patients with PDAC, and repressed numbers of cDC2s were associated with poor prognosis. Serum cytokine analyses identified IL6 as significantly elevated in patients with PDAC and negatively correlated with cDC numbers. In vitro, IL6 impaired the differentiation of cDC1s and cDC2s from BM progenitors. Single-cell RNA sequencing analysis of human cDC progenitors in the BM and blood of patients with PDAC showed an upregulation of the IL6/STAT3 pathway and a corresponding impairment of antigen processing and presentation. These results suggested that cDC2s were systemically suppressed by inflammatory cytokines, which was linked to impaired antitumor immunity.