Pancreatic ductal adenocarcinoma (PDA) is a common and lethal malignancy resulting in more than 250,000 deaths per year worldwide. Despite extensive efforts, cytotoxic and targeted therapies have provided only limited efficacy for patients with PDA to date. One contributing factor to the failure of systemic therapies may be the abundant tumor stromal content that is the characteristic of PDA. The PDA stroma, aptly termed the tumor microenvironment, occupies the majority of the tumor mass, and consists of a dynamic assortment of extracellular matrix components and nonneoplastic cells including fibroblastic, vascular, and immune cells. Recent work has revealed that the PDA stroma supports tumor growth and promotes metastasis and simultaneously serves as a physical barrier to drug delivery. Accordingly, methods that alter stromal composition or function, for instance interference with the vasculature via Notch/Hedgehog pathway inhibition or relief of vascular compression by hyaluronidase, are under active investigation. Here, we will review our current understanding of the PDA tumor microenvironment, and highlight opportunities for further exploration that may benefit patients. Clin Cancer Res; 18(16); 4266–76. ©2012 AACR.

Objective Pancreatic ductal adenocarcinoma (PDA) is characterised by stromal desmoplasia and vascular dysfunction, which critically impair drug delivery. This study examines the role of an abundant extracellular matrix component, the megadalton glycosaminoglycan hyaluronan (HA), as a novel therapeutic target in PDA. Methods Using a genetically engineered mouse model of PDA, the authors enzymatically depleted HA by a clinically formulated PEGylated human recombinant PH20 hyaluronidase (PEGPH20) and examined tumour perfusion, vascular permeability and drug delivery. The preclinical utility of PEGPH20 in combination with gemcitabine was assessed by short-term and survival studies. Results PEGPH20 rapidly and sustainably depleted HA, inducing the re-expansion of PDA blood vessels and increasing the intratumoral delivery of two chemotherapeutic agents, doxorubicin and gemcitabine. Moreover, PEGPH20 triggered fenestrations and interendothelial junctional gaps in PDA tumour endothelia and promoted a tumour-specific increase in macromolecular permeability. Finally, combination therapy with PEGPH20 and gemcitabine led to inhibition of PDA tumour growth and prolonged survival over gemcitabine monotherapy, suggesting immediate clinical utility. Conclusions The authors demonstrate that HA impedes the intratumoral vasculature in PDA and propose that its enzymatic depletion be explored as a means to improve drug delivery and response in patients with pancreatic cancer.

Pancreatic ductal adenocarcinoma (PDA) is an almost uniformly lethal disease. One explanation for the devastating prognosis is the failure of many chemotherapies, including the current standard of care therapy gemcitabine. Although our knowledge of the molecular events underlying multistep carcinogenesis in PDA has steadily increased, translation into more effective therapeutic approaches has been inefficient over the last several decades. Evidence for this innate resistance to systemic therapies was recently provided in an accurate mouse model of PDA by the demonstration that chemotherapies are poorly delivered to PDA tissues because of a deficient vasculature. This vascular deficiency correlated with the presence of a dense stromal matrix that is a prominent histological hallmark of PDA tumours. Therapeutic targeting of stromal cells decreased the stroma from pancreatic tumours, resulting in increased intratumoral perfusion and therapeutic delivery of gemcitabine. Stromal cells contained within the PDA tumour microenvironment therefore represent an additional constituent to neoplastic cells that should be critically evaluated for optimal therapeutic development in preclinical models and early clinical trials.

Second-line chemotherapy for patients with oesophagogastric adenocarcinoma refractory to platinum and fluoropyrimidines has not shown benefits in health-related quality of life (HRQoL). We assessed whether the addition of docetaxel to active symptom control alone can improve survival and HRQoL for patients. For this open-labelled, multicentre trial, we recruited patients aged 18 years or older from 30 UK centres. Patients were eligible if they had an advanced, histologically confirmed adenocarcinoma of the oesophagus, oesophagogastric junction, or stomach that had progressed on or within 6 months of treatment with a platinum-fluoropyrimidine combination. Patients could have an Eastern Cooperative Oncology Group performance status of 0-2. We randomly assigned patients using a central, computerised minimisation procedure to receive docetaxel plus active symptom control, or active symptom control alone (1:1; stratified by disease status, disease site, duration of response to previous chemotherapy, and performance status). Docetaxel was given at a dose of 75 mg/m(2) by intravenous infusion every 3 weeks for up to six cycles. The primary endpoint was overall survival, analysed by intention to treat. This is the report of the planned final analysis. This study is an International Standardised Randomised Controlled Trial, number ISRCTN13366390. Between April 21, 2008, and April 26, 2012, we recruited 168 patients, allocating 84 to each treatment group. After a median follow-up of 12 months [IQR 10-21]) and 161 (96%) deaths (80 in the docetaxel group, 81 in the active symptom control group), median overall survival in the docetaxel group was 5.2 months (95% CI 4.1-5.9) versus 3.6 months (3.3-4.4) in the active symptom control group (hazard ratio 0.67, 95% CI 0.49-0.92; p=0.01). Docetaxel was associated with higher incidence of grade 3-4 neutropenia (12 [15%] patients vs no patients), infection (15 [19%] patients vs two [3%] patients), and febrile neutropenia (six [7%] patients vs no patients). Patients receiving docetaxel reported less pain (p=0.0008) and less nausea and vomiting (p=0.02) and constipation (p=0.02). Global HRQoL was similar between the groups (p=0.53). Disease specific HRQoL measures also showed benefits for docetaxel in reducing dysphagia (p=0.02) and abdominal pain (p=0.01). Our findings suggest that docetaxel can be recommended as an appropriate second-line treatment for patients with oesophagogastric adenocarcinoma that is refractory to treatment with platinum and fluoropyrimidine. Cancer Research UK.

Nanoparticle albumin-bound (nab)-paclitaxel, an albumin-stabilized paclitaxel formulation, demonstrates clinical activity when administered in combination with gemcitabine in patients with metastatic pancreatic ductal adenocarcinoma (PDA). The limited availability of patient tissue and exquisite sensitivity of xenografts to chemotherapeutics have limited our ability to address the mechanistic basis of this treatment regimen. Here, we used a mouse model of PDA to show that the coadministration of nab-paclitaxel and gemcitabine uniquely demonstrates evidence of tumor regression. Combination treatment increases intratumoral gemcitabine levels attributable to a marked decrease in the primary gemcitabine metabolizing enzyme, cytidine deaminase. Correspondingly, paclitaxel reduced the levels of cytidine deaminase protein in cultured cells through reactive oxygen species–mediated degradation, resulting in the increased stabilization of gemcitabine. Our findings support the concept that suboptimal intratumoral concentrations of gemcitabine represent a crucial mechanism of therapeutic resistance in PDA and highlight the advantages of genetically engineered mouse models in preclinical therapeutic trials. Significance: This study provides mechanistic insight into the clinical cooperation observed between gemcitabine and nab-paclitaxel in the treatment of pancreatic cancer. Cancer Discovery; 2(3); 260–9. ©2012 AACR. Read the Commentary on this article by Clark, p. 208 This article is highlighted in the In This Issue feature, p. 193