Hyaluronan impairs vascular function and drug delivery in a mouse model of pancreatic cancer

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.

Cellular features of senescence during the evolution of human and murine ductal pancreatic cancer

During tumor initiation, oncogene-induced senescence (OIS) is proposed to limit the progression of preneoplasms to invasive carcinoma unless circumvented by the acquisition of certain tumor suppressor mutations. Using a variety of biomarkers, OIS has been previously reported in a wide range of human and murine precursor lesions, including the pancreas, lung, colon and skin. Here, we have characterized a panel of potential OIS biomarkers in human and murine pancreatic intraepithelial neoplasia (PanIN), and found that only senescence-associated β-galactosidase (SAβgal) activity is specifically enriched in these precursors, compared with pancreatic ductal adenocarcinoma (PDA). Indeed, many of the other proposed OIS biomarkers are detected in actively proliferating PanIN epithelium and in cells within the microenvironment. Surprisingly, acinar to ductal metaplasia (ADM), a distinct preneoplasm that is potentially a precursor for PanIN, also exhibits SAβgal activity and contains a higher content of p21 and p53 than PanIN. Therefore, SAβgal activity is the only biomarker that accurately identifies a small and heterogeneous population of non-proliferating premalignant cells in the pancreas, and the concomitant expression of p53 and p21 in ADM supports the possibility that PanIN and ADM each exhibit discrete senescence blocks.

Inhibition of Hedgehog signaling enhances delivery of chemotherapy in a mouse model of pancreatic cancer

Pancreatic ductal adenocarcinoma (PDA) is among the most lethal human cancers in part because it is insensitive to many chemotherapeutic drugs. Studying a mouse model of PDA that is refractory to the clinically used drug gemcitabine, we found that the tumors in this model were poorly perfused and poorly vascularized, properties that are shared with human PDA. We tested whether the delivery and efficacy of gemcitabine in the mice could be improved by coadministration of IPI-926, a drug that depletes tumor-associated stromal tissue by inhibition of the Hedgehog cellular signaling pathway. The combination therapy produced a transient increase in intratumoral vascular density and intratumoral concentration of gemcitabine, leading to transient stabilization of disease. Thus, inefficient drug delivery may be an important contributor to chemoresistance in pancreatic cancer.

Inhibition of Hedgehog signaling enhances delivery of chemotherapy in a mouse model of pancreatic cancer

Pancreatic ductal adenocarcinoma (PDA) is among the most lethal human cancers in part because it is insensitive to many chemotherapeutic drugs. Studying a mouse model of PDA that is refractory to the clinically used drug gemcitabine, we found that the tumors in this model were poorly perfused and poorly vascularized, properties that are shared with human PDA. We tested whether the delivery and efficacy of gemcitabine in the mice could be improved by coadministration of IPI-926, a drug that depletes tumor-associated stromal tissue by inhibition of the Hedgehog cellular signaling pathway. The combination therapy produced a transient increase in intratumoral vascular density and intratumoral concentration of gemcitabine, leading to transient stabilization of disease. Thus, inefficient drug delivery may be an important contributor to chemoresistance in pancreatic cancer.

Inhibition of Hedgehog signaling enhances delivery of chemotherapy in a mouse model of pancreatic cancer

Pancreatic ductal adenocarcinoma (PDA) is among the most lethal human cancers in part because it is insensitive to many chemotherapeutic drugs. Studying a mouse model of PDA that is refractory to the clinically used drug gemcitabine, we found that the tumors in this model were poorly perfused and poorly vascularized, properties that are shared with human PDA. We tested whether the delivery and efficacy of gemcitabine in the mice could be improved by coadministration of IPI-926, a drug that depletes tumor-associated stromal tissue by inhibition of the Hedgehog cellular signaling pathway. The combination therapy produced a transient increase in intratumoral vascular density and intratumoral concentration of gemcitabine, leading to transient stabilization of disease. Thus, inefficient drug delivery may be an important contributor to chemoresistance in pancreatic cancer.

Expression and shifting subcellular localization of the transcription factor, Foxd3, in embryonic and adult pancreas

Multipotent progenitor cells self renew throughout an animal's lifetime and can differentiate to give rise to different cell types. Before we can fully understand the developmental potential of progenitor cells and control their differentiation both in vivo and in vitro as stem cells, identification and characterization of the genes that control stem cell fate must first be obtained. Foxd3, a member of the forkhead family of transcriptional regulators, is required for the maintenance of embryonic stem cells and trophoblast stem cells of the early mouse embryo. We describe here the expression of this protein in the developing pancreas. Foxd3 is expressed in most beta cells and infrequently in alpha and PP cells but is not expressed in somatostatin cells. The subcellular localization of Foxd3 varies with fat content in the diet; with a high fat diet the protein is found primarily in the cytoplasm while a low fat diet results in nuclear localization. Foxd3 is differentially localized in a rat model of diabetes: it is nuclear in ZDF rats but cytoplasmic in their lean counterparts. Foxd3 is nuclear in Lep(Ob/Ob) mice.

Surface-plasmon spatial light modulators based on liquid crystal

The development of a new class of spatial light modulator (SLM), which uses modulation of lossy guided waves generated by surface-plasmon resonance, is described. The potential advantages of this technique are explained, including increased response uniformity and enhanced sensitivity and speed. An optically addressed SLM that is based on a nematic liquid crystal with a spatial resolution better than 10 line pairs/mm (at 50% modulation transfer function) is demonstrated. For the design of devices that are based on newer smectic liquid crystals the use of anisotropy-induced polarization mixing and the so-called pseudoplasmon modes are described. Such modes offer controllable sensitivity-spatial resolution characteristics in simple liquid-crystal SLM structures. Within a typical SLM resolution requirement of 10 line pairs/mm, for example, the sensitivity can be optimized to obtain a theoretical reflectivity modulation from 0 to 0.7 for a liquid-crystal director modulation of 5 degrees .

Percutaneous alternatives in nutritional support: a radiologic perspective

As alternatives to per os feeding and nutritional support increase in number and complexity, the interventional radiologist has come to play a more significant role in the creation and maintenance of nutritional access. In very difficult access cases, the concerted effort of the nutritional surgeon and the radiologist is often required. We describe several such situations which have been successfully managed at our institution. The indications for and techniques of percutaneous reestablishment of surgically placed jejunostomy tubes, the percutaneous conversion of gastrostomy to jejunostomy tubes with retention of the gastrostomy tube, and percutaneous placement of an inferior vena caval Hickman catheter are all described in detail.

Plants with potential to enhance significant tumor growth

Of 20,000 plant extracts submitted to the National Cancer Institute antitumor screens from 1960 to 1980, over 95% exhibited inadequate tumor-inhibiting activity or promoted tumor growth. Of these, 50 extracts representing 42 species showed significant levels of tumor growth enhancement compared to controls on the basis of tumor weights when the extracts were administered to test and control animals dosed equally on the basis of implanted tumor weights. Because of the continuing threat of environmentally induced or promoted cancer in the human population, the species identified in this report are deemed worthy of studies designed to quantitate the risks of contact by botanists, hikers, plant hobbyists, and field workers. Even more fundamental, studies of these plants could provide knowledge of new compounds under the influence of which tumor growth is enhanced. Further studies might also reveal the mechanisms of this tumor enhancement.