Unsupervised class discovery in pancreatic ductal adenocarcinoma reveals cell-intrinsic mesenchymal features and high concordance between existing classification systems

Pancreatic ductal adenocarcinoma (PDAC) has the worst prognosis of all common cancers. However, divergent outcomes exist between patients, suggesting distinct underlying tumor biology. Here, we delineated this heterogeneity, compared interconnectivity between classification systems, and experimentally addressed the tumor biology that drives poor outcome. RNA-sequencing of 90 resected specimens and unsupervised classification revealed four subgroups associated with distinct outcomes. The worst-prognosis subtype was characterized by mesenchymal gene signatures. Comparative (network) analysis showed high interconnectivity with previously identified classification schemes and high robustness of the mesenchymal subtype. From species-specific transcript analysis of matching patient-derived xenografts we constructed dedicated classifiers for experimental models. Detailed assessments of tumor growth in subtyped experimental models revealed that a highly invasive growth pattern of mesenchymal subtype tumor cells is responsible for its poor outcome. Concluding, by developing a classification system tailored to experimental models, we have uncovered subtype-specific biology that should be further explored to improve treatment of a group of PDAC patients that currently has little therapeutic benefit from surgical treatment.

Recent Advances in Pancreatic Cancer Surgery of Relevance to the Practicing Pathologist

Recent advances in pancreatic surgery have the potential to improve outcomes for patients with pancreatic cancer. We address 3 new, trending topics in pancreatic surgery that are of relevance to the pathologist. First, increasing awareness of the prognostic impact of intraoperatively detected extraregional and regional lymph node metastases and the international consensus definition on lymph node sampling and reporting. Second, neoadjuvant chemotherapy, which is capable of changing 10% to 20% of initially unresectable, to resectable disease. Third, in patients who remain unresectable following neoadjuvant chemotherapy, local ablative therapies may change indications for treatment and improve outcomes.

Skeletal Muscle Quality is Associated with Worse Survival After Pancreatoduodenectomy for Periampullary, Nonpancreatic Cancer

BACKGROUND

Body composition measures may predict outcomes of cancer surgery. Whereas low muscle mass shown on preoperative computed tomography (CT) scans has been associated with worse outcomes after surgery for pancreatic cancer, less consideration has been given to low muscle attenuation, reflecting poor muscle quality. Studies relating muscle mass and muscle attenuation with outcomes for patients with periampullary, nonpancreatic cancer are lacking.

METHODS

Skeletal muscle mass and attenuation were assessed in 166 consecutive patients undergoing pancreatoduodenectomy (PD) for periampullary, nonpancreatic cancer at a single center between 2000 and 2012. The skeletal muscle index (SMI) was calculated from cross-sectional muscle area on preoperative CT imaging at the third lumbar vertebra level (L3) and normalized for height. The skeletal muscle attenuation index (MAI) was calculated by measuring the average Hounsfield units of the total muscle area at the L3 level. Overall survival (OS) and the rate of major postoperative complications (Clavien-Dindo ≥3) were extracted from prospectively maintained databases.

RESULTS

Low SMI was present in 78.3 % and low MAI in 48.8 % of the patients. The multivariate analysis showed lymph node metastasis [hazard ratio (HR) 1.8; 95 % confidence interval (CI) 1.1-2.9], microscopic radicality (HR 2.0; 95 % CI 1.2-3.4), and low MAI (HR 2.0; 95 % CI 1.2-3.3), but not low SMI to be significantly associated with decreased OS. Low MAI (HR 1.9; 95 % CI 1.0-3.8) was the only independent risk factor for major postoperative complications.

CONCLUSION

Skeletal muscle quality, but not muscle mass, predicted survival and major complications after PD for periampullary, nonpancreatic cancer. Preoperative CT-derived body composition measures may stratify patients into risk categories and support shared decision making.

Outcomes of Distal Pancreatectomy for Pancreatic Ductal Adenocarcinoma in the Netherlands: A Nationwide Retrospective Analysis

BACKGROUND

Large multicenter series on outcomes and predictors of survival after distal pancreatectomy (DP) for pancreatic ductal adenocarcinoma (PDAC) are scarce.

METHODS

Adults who underwent DP for PDAC in 17 Dutch pancreatic centers between January 2005 and September 2013 were analyzed retrospectively. The primary outcome was survival, and predictors of survival were identified using Cox regression analysis.

RESULTS

In total, 761 consecutive patients after DP were assessed, of whom 620 patients were excluded because of non-PDAC histopathology (n = 616) or a lack of data (n = 4), leaving a total of 141 patients included in the study [45 % (n = 63) male, mean age 64 years (SD = 10)]. Multivisceral resection was performed in 43 patients (30 %) and laparoscopic resection was performed in 7 patients (5 %). A major complication (Clavien-Dindo score of III or higher) occurred in 46 patients (33 %). Mean tumor size was 44 mm (SD 23), and histopathological examination showed 70 R0 resections (50 %), while 30-day and 90-day mortality was 3 and 6 %, respectively. Overall, 63 patients (45 %) received adjuvant chemotherapy. Median survival was 17 months [interquartile range (IQR) 13-21], with a median follow-up of 17 months (IQR 8-29). Cumulative survival at 1, 3 and 5 years was 64, 29, and 22 %, respectively. Independent predictors of worse postoperative survival were R1/R2 resection [hazard ratio (HR) 1.6, 95 % confidence interval (CI) 1.1-2.4], pT3/pT4 stage (HR 1.9, 95 % CI 1.3-2.9), a major complication (HR 1.7, 95 % CI 1.1-2.5), and not receiving adjuvant chemotherapy (HR 1.5, 95 % CI 1.0-2.3).

CONCLUSION

Survival after DP for PDAC is poor and is related to resection margin, tumor stage, surgical complications, and adjuvant chemotherapy. Further studies should assess to what extent prevention of surgical complications and more extensive use of adjuvant chemotherapy can improve survival.

Establishment of patient-derived xenograft models and cell lines for malignancies of the upper gastrointestinal tract

Background

The upper gastrointestinal tract is home to some of most notorious cancers like esophagogastric and pancreatic cancer. Several factors contribute to the lethality of these tumors, but one that stands out for both tumor types is the strong inter- as well as intratumor heterogeneity. Unfortunately, genetic tumor models do not match this heterogeneity, and for esophageal cancer no adequate genetic models exist. To allow for an improved understanding of these diseases, tissue banks with sufficient amount of samples to cover the extent of diversity of human cancers are required. Additionally, xenograft models that faithfully mimic and span the breadth of human disease are essential to perform meaningful functional experiments.

Methods

We describe here the establishment of a tissue biobank, patient derived xenografts (PDXs) and cell line models of esophagogastric and pancreatic cancer patients. Biopsy material was grafted into immunocompromised mice and PDXs were used to establish primary cell cultures to perform functional studies. Expression of Hedgehog ligands in patient tumor and matching PDX was assessed by immunohistochemical staining, and quantitative real-time PCR as well as flow cytometry was used for cultured cells. Cocultures with Hedgehog reporter cells were performed to study paracrine signaling potency. Furthermore, SHH expression was modulated in primary cultures using lentiviral mediated knockdown.

Results

We have established a panel of 29 PDXs from esophagogastric and pancreatic cancers, and demonstrate that these PDXs mirror several of the (immuno)histological and biochemical characteristics of the original tumors. Derived cell lines can be genetically manipulated and used to further study tumor biology and signaling capacity. In addition, we demonstrate an active (paracrine) Hedgehog signaling mode by both tumor types, the magnitude of which has not been compared directly in previous studies.

Conclusions

Our established PDXs and their matching primary cell lines retain important characteristics seen in the original tumors, and this should enable future studies to address the responses of these tumors to different treatment modalities, but also help in gaining mechanistic insight in how some tumors respond to certain regimens and others do not.

Electronic supplementary material

The online version of this article (doi:10.1186/s12967-015-0469-1) contains supplementary material, which is available to authorized users.