Reprogrammed Schwann Cells Organize into Dynamic Tracks that Promote Pancreatic Cancer Invasion

Nerves are a component of the tumor microenvironment contributing to cancer progression, but the role of cells from nerves in facilitating cancer invasion remains poorly understood. Here we show that Schwann cells (SC) activated by cancer cells collectively function as tumor-activated Schwann cell tracks (TAST) that promote cancer cell migration and invasion. Nonmyelinating SCs form TASTs and have cell gene expression signatures that correlate with diminished survival in patients with pancreatic ductal adenocarcinoma. In TASTs, dynamic SCs form tracks that serve as cancer pathways and apply forces on cancer cells to enhance cancer motility. These SCs are activated by c-Jun, analogous to their reprogramming during nerve repair. This study reveals a mechanism of cancer cell invasion that co-opts a wound repair process and exploits the ability of SCs to collectively organize into tracks. These findings establish a novel paradigm of how cancer cells spread and reveal therapeutic opportunities.

SIGNIFICANCE

How the tumor microenvironment participates in pancreatic cancer progression is not fully understood. Here, we show that SCs are activated by cancer cells and collectively organize into tracks that dynamically enable cancer invasion in a c-Jun-dependent manner. See related commentary by Amit and Maitra, p. 2240. This article is highlighted in the In This Issue feature, p. 2221.

An In Vivo Murine Sciatic Nerve Model of Perineural Invasion

Cancer cells invade nerves through a process termed perineural invasion (PNI), in which cancer cells proliferate and migrate in the nerve microenvironment. This type of invasion is exhibited by a variety of cancer types, and very frequently is found in pancreatic cancer. The microscopic size of nerve fibers within mouse pancreas renders the study of PNI difficult in orthotopic murine models. Here, we describe a heterotopic in vivo model of PNI, where we inject syngeneic pancreatic cancer cell line Panc02-H7 into the murine sciatic nerve. In this model, sciatic nerves of anesthetized mice are exposed and injected with cancer cells. The cancer cells invade in the nerves proximally toward the spinal cord from the point of injection. The invaded sciatic nerves are then extracted and processed with OCT for frozen sectioning. H&E and immunofluorescence staining of these sections allow quantification of both the degree of invasion and changes in protein expression. This model can be applied to a variety of studies on PNI given its versatility. Using mice with different genetic modifications and/or different types of cancer cells allows for investigation of the cellular and molecular mechanisms of PNI and for different cancer types. Furthermore, the effects of therapeutic agents on nerve invasion can be studied by applying treatment to these mice.

Uncovering the truth about covered stents: is there a difference between covered versus uncovered stents with transjugular intrahepatic portosystemic shunts?

INTRODUCTION

Polytetrafluoroethylene (PTFE)-covered transjugular intrahepatic portosystemic shunt (TIPS) stents purportedly provide superior patency. This study was undertaken to determine whether covered stents provide better long-term patency and outcomes after TIPSs.

METHODS

Patients with portal hypertension undergoing TIPS at a large teaching hospital from 2001 to 2010 were studied. Median data are presented.

RESULTS

Two hundred forty-six patients underwent TIPS; 70 received uncovered stents, and 176 received covered stents. Patients who received uncovered stents had more severely impaired liver function (41% were Child class C cirrhotics). The follow-up was longer with uncovered stents (48 vs 24 months, P < .01). Reinterventions for stenosis were undertaken in 33% with uncovered stents versus 19% with covered stents (P = .01). Shunt dysfunction occurred in 57% with uncovered stents versus 21% covered (P = .05). A deterioration of hepatic function occurred in 31% with uncovered stents versus 30% with covered (P = .32). Survival with uncovered stents was 31 months versus 33 months with covered stents (P = .55, Kaplan-Meier).

CONCLUSIONS

Covered stents may improve patency but do not mitigate postshunt hepatic dysfunction and do not improve survival.

Pancreaticoduodenectomy for suspected periampullary cancers: the mimes of malignancy

BACKGROUND

Pancreaticoduodenectomies are often undertaken with suspicion of malignancy. We undertook this study to determine if and how unnecessary pancreaticoduodenectomies can be avoided.

METHODS

Data from patients undergoing pancreaticoduodenectomy were prospectively collected. Operative indications, including presenting symptoms and results with imaging, with or without biopsy, were reviewed.

RESULTS

From 1996 through to 2007, 551 patients underwent pancreaticoduodenectomy at our institution. Chronic pancreatitis was the operative indication in 3% of patients; premalignant/malignant lesions were present in 86% of patients. Eleven per cent of patients underwent 'unnecessary' pancreaticoduodenectomies with presumptive diagnoses of cancer but were without premalignant/malignant disease on final report by Pathology [pancreatitis in 63%, serous cystadenomas (<4 cm) in 14%]. Of the unnecessary resections, 20% had histories and imaging sufficient to diagnose pancreatitis, 18% had inaccurate preoperative brushings/biopsies 'documenting' cancer, 11% had clear misinterpretations of their imaging studies and 7% had inadequate preoperative evaluations. However, 45% had signs/symptoms of cancer with a pancreatic head mass/biliary stricture.

CONCLUSION

Only a small minority of patients undergoing pancreaticoduodenectomy for suspicion of periampullary cancer do so unnecessarily. Preoperative review of biopsies, better considerations of pancreatitis and careful evaluation of imaging, particularly for cystic masses, will decrease unnecessary pancreaticoduodenectomies.

Aesthetic considerations of the medial gastrocnemius myocutaneous flap

A technique for the repair of a high anterior tibial defect is described in three clinical cases using a modified medial gastrocnemius myocutaneous island flap. The repair was done in such a way as to preserve as much of the normal contour as possible, after the fashion of the muscle flap alone, while retaining the advantages of full-thickness myocutaneous coverage of the defect. The result was an aesthetically improved reconstruction that we feel justifies further use of the gastrocnemius myocutaneous flap in selected patients.