Neural invasion in pancreatic cancer: the past, present and future

Axon Guidance Molecules Promote Perineural Invasion and Metastasis of Orthotopic Pancreatic Tumors in Mice

BACKGROUND & AIMS

Little is known about mechanisms of perineural invasion (PNI) by pancreatic ductal adenocarcinomas (PDAs) or other tumors. Annexin A2 (ANXA2) regulates secretion of SEMA3D, an axon guidance molecule, which binds and activates the receptor PLXND1 to promote PDA invasion and metastasis. We investigated whether axon guidance molecules promote PNI and metastasis by PDA cells in mice.

METHODS

We performed studies in a dorsal root ganglion (DRG) invasion system, wild-type C57BL/6 mice (controls), mice with peripheral sensory neuron-specific disruption of PlxnD1 (PLAC mice), LSL-KRASG12D/+;LSL-TP53R172H/+;PDX-1-CRE+/+ (KPC) mice, and KPC mice crossed with ANXA2-knockout mice (KPCA mice). PDA cells were isolated from KPC mice and DRG cells were isolated from control mice. Levels of SEMA3D or ANXA2 were knocked down in PDA cells with small hairpin and interfering RNAs and cells were analyzed by immunoblots in migration assays, with DRGs and with or without antibodies against PLXND1. PDA cells were injected into the pancreas of control and PLAC mice, growth of tumors was assessed, and tumor samples were analyzed by histology. DRG cells were incubated with SEMA3D and analyzed by live imaging. We measured levels of SEMA3D and PLXND1 in PDA specimens from patients with PNI and calculated distances between tumor cells and nerves.

RESULTS

DRG cells increase the migration of PDC cells in invasion assays; knockdown of SEMA3D in PDA cells or antibody blockade of PLXND1 on DRG cells reduced this invasive activity. In mice, orthotopic tumors grown from PDA cells with knockdown of SEMA3D, and in PLAC mice, orthotopic tumors grown from PDA cells, had reduced innervation and formed fewer metastases than orthotopic tumors grown from PDA cells in control mice. Increased levels of SEMA3D and PLXND1 in human PDA specimens associated with PNI.

CONCLUSIONS

DRG cells increase the migratory and invasive activities of pancreatic cancer cells, via secretion of SEMA3D by pancreatic cells and activation of PLXND1 on DRGs. Knockdown of SEMA3D and loss of neural PLXND1 reduces innervation of orthotopic PDAs and metastasis in mice. Increased levels of SEMA3D and PLXND1 in human PDA specimens associated with PNI. Strategies to disrupt the axon guidance pathway mediated by SEMA3D and PLXND1 might be developed to slow progression of PDA.

Nerves and Pancreatic Cancer: New Insights into a Dangerous Relationship

Perineural invasion (PNI) is defined as the presence of neoplastic cells along nerves and/or within the different layers of nervous fibers: epineural, perineural and endoneural spaces. In pancreatic cancer-particularly in pancreatic ductal adenocarcinoma (PDAC)-PNI has a prevalence between 70 and 100%, surpassing any other solid tumor. PNI has been detected in the early stages of pancreatic cancer and has been associated with pain, increased tumor recurrence and diminished overall survival. Such an early, invasive and recurrent phenomenon is probably crucial for tumor growth and metastasis. PNI is a still not a uniformly characterized event; usually it is described only dichotomously ("present" or "absent"). Recently, a more detailed scoring system for PNI has been proposed, though not specific for pancreatic cancer. Previous studies have implicated several molecules and pathways in PNI, among which are secreted neurotrophins, chemokines and inflammatory cells. However, the mechanisms underlying PNI are poorly understood and several aspects are actively being investigated. In this review, we will discuss the main molecules and signaling pathways implicated in PNI and their roles in the PDAC.

Netrin-1 promotes cell neural invasion in gastric cancer via its receptor neogenin

Neural invasion (NI) is one of the important routes for local spread of gastric cancer (GC) correlated with poor prognosis. However, the exact cellular characteristics and molecular mechanisms of NI in GC are still unclear. Netrin-1(NTN1) as an axon guidance molecule was firstly found during neural system development. Importantly, NTN1 has an essential role in the progression of malignant tumor and specifically mediates the induction of invasion. In this study, we found NTN1 expression was significantly increased in 97 tumor tissues from GC patients and positively correlated with NI (p<0.05). In addition, we detected NTN1 knockdown significantly suppressed GC cells migration and invasion. Moreover, our results showed that reciprocity was observed between GC cells and neurites colonies in dorsal root ganglia (DRG)-GC cells co-culture vitro model. GC cells with NTN1 silencing could suppress their abilities to navigate along surrounding neuritis and this effect was depended on its receptor neogenin. In vivo, NTN1 inhibition also decreased GC cells sciatic nerve invasion. Taken together, our findings argue that NTN1 and its receptor neogenin might act synergistically in promoting GC cells neural invasion. Inhibiting the activity of NTN1 could be a potential strategy targeting NI in GC therapy.

Perineural invasion in pancreatic cancer: proteomic analysis and in vitro modelling

Perineural invasion (PNI) is a common and characteristic feature of pancreatic ductal adenocarcinoma (PDAC) that is associated with poor prognosis, tumor recurrence, and generation of pain. However, the molecular alterations in cancer cells and nerves within PNI have not previously been comprehensively analyzed. Here, we describe our proteomic analysis of the molecular changes underlying neuro-epithelial interactions in PNI using liquid chromatography-mass spectrometry (LC-MS/MS) in microdissected PNI and non-PNI cancer, as well as in invaded and noninvaded nerves from formalin-fixed, paraffin-embedded PDAC tissues. In addition, an in vitro model of PNI was developed using a co-culture system comprising PDAC cell lines and PC12 cells as the neuronal element. The overall proteomic profiles of PNI and non-PNI cancer appeared largely similar. In contrast, upon invasion by cancer cells, nerves demonstrated widespread plasticity with a pattern consistent with neuronal injury. The up-regulation of SCG2 (secretogranin II) and neurosecretory protein VGF (nonacronymic) in invaded nerves in PDAC tissues was further validated using immunohistochemistry. The tested PDAC cell lines were found to be able to induce neuronal plasticity in PC12 cells in our in vitro established co-culture model. Changes in expression levels of VGF, as well as of two additional proteins previously reported to be overexpressed in PNI, Nestin and Neuromodulin (GAP43), closely recapitulated our proteomic findings in PDAC tissues. Furthermore, induction of VGF, while not necessary for PC12 survival, mediated neurite extension induced by PDAC cell lines. In summary, here we report the proteomic alterations underlying PNI in PDAC and confirm that PDAC cells are able to induce neuronal plasticity. In addition, we describe a novel, simple, and easily adaptable co-culture model for in vitro study of neuro-epithelial interactions.

L1CAM induces perineural invasion of pancreas cancer cells by upregulation of metalloproteinase expression

Pancreas cancer cells have a tendency to invade along nerves. Such cancerous nerve invasion (CNI) is associated with poor outcome; however, the exact mechanism that drives cancer cells to disseminate along nerves is unknown. Immunohistochemical analysis of human pancreatic ductal adenocarcinoma (PDAC) specimens showed overexpression of the L1 cell adhesion molecule (L1CAM) in cancer cells and in adjacent Schwann cells (SC) in invaded nerves. By modeling the neural microenvironment, we found that L1CAM secreted from SCs acts as a strong chemoattractant to cancer cells, through activation of MAP kinase signaling. L1CAM also upregulated expression of metalloproteinase-2 (MMP-2) and MMP-9 by PDAC cells, through STAT3 activation. Using a transgenic Pdx-1-Cre/KrasG12D /p53R172H (KPC) mouse model, we show that treatment with anti-L1CAM Ab significantly reduces CNI in vivo. We provide evidence of a paracrine response between SCs and cancer cells in the neural niche, which promotes cancer invasion via L1CAM secretion.

A mouse model for pain and neuroplastic changes associated with pancreatic ductal adenocarcinoma

Pancreatic ductal adenocarcinoma (PDAC) continues to be one of the deadliest human malignancies and is associated with excruciating pain, which is a serious complication and severely impacts the quality of life in patients. In human patients, poor survival prognosis is linked to remarkable remodeling of intrapancreatic nerves, which, in turn, is correlated to increased pain intensity. Understanding mechanisms underlying pain associated with PDAC has been hampered by the lack of animal models which replicate all germane aspects of the disease and importantly, enable analyses of pain associated with PDAC. In this study, we describe an immunocompetent orthotopic mouse model of PDAC involving intrapancreatic growth of K8484 mouse PDAC cells, which reliably exhibits a large number of key characteristics of human PDAC, including its unique histopathology and neuroplastic changes. We observed that tumor-bearing mice demonstrated significant abdominal mechanical hypersensitivity to von Frey stimuli as well as on-going pain in the conditioned place preference paradigm. Moreover, a myriad of other behavioral tests revealed that indicators of overall well-being were significantly reduced in tumor-bearing mice as compared to sham mice. Morphological and immunohistochemical analyses revealed structural remodeling in several different types of sensory and autonomic nerve fibers. Finally, perineural invasion of tumor cells, a cardinal manifestation in human PDAC, was also observed in our orthotopic mouse model. Thus, we describe a validated tumor model for quantitatively testing hypersensitivity and pain in PDAC, which lays a crucial basis for interrogating tumor-nerve interactions and the molecular and cellular mechanisms underlying pain in PDAC.

Extrapancreatic perineural invasion in pancreatic adenocarcinoma

Pancreatic ductal adenocarcinoma continues to be a highly lethal disease, despite advances in modern medicine. Curative surgical options continue to carry significant morbidity and offer little improvement in overall 5-year survival. Currently, imaging plays an essential role in the pre-operative evaluation of patients who are undergoing evaluation for resection. However, some pancreatic cancers have particularly aggressive biology, despite appearing resectable by conventional imaging criteria. Imaging biomarkers that serve as surrogates for tumors with such aggressive phenotype have been recently described, namely duodenal invasion and extrapancreatic perineural invasion. In this pictorial review, we will summarize key concepts of extrapancreatic perineural invasion, describe its association with a poor prognosis, and highlight the role of imaging in its detection.

LIF Drives Neural Remodeling in Pancreatic Cancer and Offers a New Candidate Biomarker

Pancreatic ductal adenocarcinoma (PDAC) is characterized by extensive stroma and pathogenic modifications to the peripheral nervous system that elevate metastatic capacity. In this study, we show that the IL6-related stem cell-promoting factor LIF supports PDAC-associated neural remodeling (PANR). LIF was overexpressed in tumor tissue compared with healthy pancreas, but its receptors LIFR and gp130 were expressed only in intratumoral nerves. Cancer cells and stromal cells in PDAC tissues both expressed LIF, but only stromal cells could secrete it. Biological investigations showed that LIF promoted the differentiation of glial nerve sheath Schwann cells and induced their migration by activating JAK/STAT3/AKT signaling. LIF also induced neuronal plasticity in dorsal root ganglia neurons by increasing the number of neurites and the soma area. Notably, injection of LIF-blocking antibody into PDAC-bearing mice reduced intratumoral nerve density, supporting a critical role for LIF function in PANR. In serum from human PDAC patients and mouse models of PDAC, we found that LIF titers positively correlated with intratumoral nerve density. Taken together, our findings suggest LIF as a candidate serum biomarker and diagnostic tool and a possible therapeutic target for limiting the impact of PANR in PDAC pathophysiology and metastatic progression.Significance: This study suggests a target to limit neural remodeling in pancreatic cancer, which contributes to poorer quality of life and heightened metastatic progression in patients. Cancer Res; 78(4); 909-21. ©2017 AACR.

Prospective Evaluation of Associations between Cancer-Related Pain and Perineural Invasion in Patients with Resectable Pancreatic Adenocarcinoma

INTRODUCTION

Perineural invasion is a unique characteristic of pancreatic adenocarcinoma biology and is present in the majority of resected pathologic specimens. The purpose of this study was to understand the relationships between preoperative pain and perineural invasion in patients with pancreatic adenocarcinoma.

METHODS

Fifty-two chemotherapy naive patients undergoing resection for pancreatic adenocarcinoma from 2012 to 2014 completed a previously validated Brief Pain Inventory survey for preoperative clinical pain scoring. Preoperative pain was correlated with multiple clinicopathologic features.

RESULTS

Preoperative pain was not associated with pathologic cancer stage, lymph node status, lymph node positivity ratio, resection margin status, or tumor location within the pancreas. In the subgroup of pancreatic head cancers, pain interference with affect was associated with the absence of perineural invasion (p = 0.02). Patients with stage I cancer had higher pain interference scores than those with stage II cancer (p = 0.02).

CONCLUSIONS

Preoperative pain does not predict the presence of perineural invasion or other pathologic prognostic factors in patients with resectable pancreatic adenocarcinoma. Higher pain scores in pancreatic head cancers correlated with absence of perineural invasion and early cancer stage. The effects of preoperative pain on quality and interference of daily life deserve further investigation in larger prospective studies involving patients with pancreatic cancer.

How Schwann cells facilitate cancer progression in nerves

Recent studies have demonstrated a critical role for nerves in enabling tumor progression. The association of nerves with cancer cells is well established for a variety of malignant tumors, including pancreatic, prostate and the head and neck cancers. This association is often correlated with poor prognosis. A strong partnership between cancer cells and nerve cells leads to both cancer progression and expansion of the nerve network. This relationship is supported by molecular pathways related to nerve growth and repair. Peripheral nerves form complex tumor microenvironments, which are made of several cell types including Schwann cells. Recent studies have revealed that Schwann cells enable cancer progression by adopting a de-differentiated phenotype, similar to the Schwann cell response to nerve trauma. A detailed understanding of the molecular and cellular mechanisms involved in the regulation of cancer progression by the nerves is essential to design strategies to inhibit tumor progression.

Pleiotrophin and N-syndecan promote perineural invasion and tumor progression in an orthotopic mouse model of pancreatic cancer

AIM

To detect the expression of pleiotrophin (PTN) and N-syndecan in pancreatic cancer and analyze their association with tumor progression and perineural invasion (PNI).

METHODS

An orthotopic mouse model of pancreatic cancer was created by injecting tumor cells subcapsularly in a root region of the pancreas beneath the spleen. Pancreatic cancer tissues were taken from 36 mice that survived for more than 90 d. PTN and N-syndecan proteins were detected by immunohistochemistry and analyzed for their correlation with pathological features, PNI, and prognosis.

RESULTS

The expression rates of PTN and N-syndecan proteins were 66.7% and 61.1%, respectively, in cancer tissue. PTN and N-syndecan expression was associated with PNI (P = 0.019 and P = 0.032, respectively). High PTN expression was closely associated with large bloody ascites (P = 0.009), liver metastasis (P = 0.035), and decreased survival time (P = 0.022). N-syndecan expression was significantly associated with tumor size (P = 0.025), but not with survival time (P = 0.539).

CONCLUSION

High PTN and N-syndecan expression was closely associated with metastasis and poor prognosis, suggesting that they may promote tumor progression and PNI in the orthotopic mouse model of pancreatic cancer.

Upregulation of RET induces perineurial invasion of pancreatic adenocarcinoma

Tumor spread along nerves, a phenomenon known as perineurial invasion, is common in various cancers including pancreatic ductal adenocarcinoma (PDAC). Neural invasion is associated with poor outcome, yet its mechanism remains unclear. Using the transgenic Pdx-1-Cre/KrasG12D /p53R172H (KPC) mouse model, we investigated the mechanism of neural invasion in PDAC. To detect tissue-specific factors that influence neural invasion by cancer cells, we characterized the perineurial microenvironment using a series of bone marrow transplantation (BMT) experiments in transgenic mice expressing single mutations in the Cx3cr1, GDNF and CCR2 genes. Immunolabeling of tumors in KPC mice of different ages and analysis of human cancer specimens revealed that RET expression is upregulated during PDAC tumorigenesis. BMT experiments revealed that BM-derived macrophages expressing the RET ligand GDNF are highly abundant around nerves invaded by cancer. Inhibition of perineurial macrophage recruitment, using the CSF-1R antagonist GW2580 or BMT from CCR2-deficient donors, reduced perineurial invasion. Deletion of GDNF expression by perineurial macrophages, or inhibition of RET with shRNA or a small-molecule inhibitor, reduced perineurial invasion in KPC mice with PDAC. Taken together, our findings show that RET is upregulated during pancreas tumorigenesis and its activation induces cancer perineurial invasion. Trafficking of BM-derived macrophages to the perineurial microenvironment and secretion of GDNF are essential for pancreatic cancer neural spread.

High expression of muscarinic acetylcholine receptor 3 predicts poor prognosis in patients with pancreatic ductal adenocarcinoma

Aims

Recent studies showed that muscarinic acetylcholine receptor 3 (M3), as a muscarinic acetylcholine receptor family member that plays an important role in normal physiological function, is engaged in cancer progression. However, the role of M3 in pancreatic ductal adenocarcinoma (PDAC) is not known. The aim of this study is to investigate the expression and prognostic value of M3 in patients with PDAC.

Materials and methods

The localization and expression of M3 in PDAC were examined by immunohistochemistry. VAChT was employed to detect parasympathetic nerve fibers in the corresponding M3 PDAC tissues. The correlation between M3 expression and patients’ survival was assessed by Kaplan–Meier analysis.

Results

M3 was discovered predominantly localized in the cell cytoplasm and expressed in all specimens of PDAC patients. Significant correlation was noted between increased M3 intensity and high grade of PDAC (P<0.01), more lymph node metastasis (P<0.01) as well as shorter patient overall survival (P<0.01). Morphologically, cells with high M3 expression were more frequently located at the invasive tumor front/tumor budding cells, metastatic lymph nodes and parasympathetic nerve fibers.

Conclusion

High expression of M3 is a prognostic marker for PDAC.

MUC4-promoted neural invasion is mediated by the axon guidance factor Netrin-1 in PDAC

Neuralinvasion (NI) is an important oncological feature of pancreatic ductal adenocarcinoma (PDAC). However, the underlying mechanism of NI in PDAC remains unclear. In this study, we found that MUC4 was overexpressed in PDAC tissues and high expression of MUC4 indicated a higher NI incidencethan low expression. In vitro, MUC4 knockdown inhibited the migration and invasion of PDAC cells and impaired the migration of PDAC cells along nerve in dorsal root ganglia (DRG)-PDAC cell co-culture assay. In vivo, MUC4 knockdown suppressed the NI of PDAC cells in a murine NI model. Mechanistically, our data revealed that MUC4 silencing resulted in decreased netrin-1 expression and re-expression of netrin-1 in MUC4-silenced cells rescued the capability of NI. Furthermore, we identified that decreased netrin-1 expression was owed to the downregulation of HER2/AKT/NF-κB pathway in MUC4-silenced cells. Additionally, MUC4 knockdown also resulted in the downregulation of pFAK, pSrc, pJNK and MMP9. Taken together, our findings revealed a novelrole of MUC4 in potentiating NI via netrin-1 through the HER2/AKT/NF-κBpathway in PDAC.

Evaluation of the association between perineural invasion and clinical and histopathological features of cervical cancer

Perineural invasion (PNI) has been investigated as a new prognostic factor in a number of carcinomas. However, studies on PNI in cervical cancer are limited, and inconsistent conclusions have been reported by different groups. The aim of the present study was to analyze the relationship between perineural invasion (PNI) and clinical and histopathological features of cervical cancer, and to evaluate the clinical significance of PNI of cervical cancer. Retrospective review identified 206 patients with cervical cancer who underwent radical hysterectomy plus pelvic lymphadenectomy between December 2012 and August 2014. The association between PNI and clinical and histopathological features of cervical cancer and post-operative radiotherapy was evaluated based on univariate and multivariate analyses. PNI of cervical cancer was identified in 33 of 206 (16%) cervical cancer patients. Univariate analysis demonstrated that PNI was associated with clinical stage, tumor grade, tumor size, depth of invasion, lymphovascular space invasion (LVSI), and lymph node metastasis (P<0.05), but not associated with age and histopathological types (P>0.05). Multivariate analysis suggests that LVSI and lymph node metastasis were associated with PNI of cervical cancer (P<0.05). In addition, post-operative radiotherapy was significantly more recommended for patients with PNI than those without PNI (P<0.001). In conclusion, PNI of cervical cancer is associated with LVSI and lymph node metastasis and can be used as an index for the determination of post-operative radiotherapy for cervical cancer patients.

Nerve growth factor & TrkA as novel therapeutic targets in cancer

In the past 20years, nerve growth factor (NGF) and its receptors TrkA & p75NTR were recognized to be overexpressed in the overwhelming majority of human solid cancers. Recent studies discovered the presence of overactive TrkA signaling due to TrkA rearrangements or TrkA fusion products in frequent cancers like colorectal cancer, thyroid cancer, or acute myeloid leukemia. Thus, targeting TrkA/NGF via selective small-molecule-inhibitors or antibodies has gained enormous attention in the drug discovery sector. Clinical studies on the anti-cancer impact of NGF-blocking antibodies are likely to be accelerated after the recent removal of clinical holds on these agents by regulatory authorities. Based on these current developments, the present review provides not only a broad overview of the biological effects of NGF-TrkA-p75NTR on cancer cells and their microenvironment, but also explains why NGF and its receptors are going to evoke major interest as promising therapeutic anti-cancer targets in the coming decade.

Mechanisms of cancer dissemination along nerves

The local extension of cancer cells along nerves is a frequent clinical finding for various tumours. Traditionally, nerve invasion was assumed to occur via the path of least resistance; however, recent animal models and human studies have revealed that cancer cells have an innate ability to actively migrate along axons in a mechanism called neural tracking. The tendency of cancer cells to track along nerves is supported by various cell types in the perineural niche that secrete multiple growth factors and chemokines. We propose that the perineural niche should be considered part of the tumour microenvironment, describe the molecular cues that facilitate neural tracking and suggest methods for its inhibition.

Targeted tumor delivery and controlled release of neuronal drugs with ferritin nanoparticles to regulate pancreatic cancer progression

Pancreatic cancer is a lethal malignancy whose progression is highly dependent on the nervous microenvironment. This study develops neural drug-loaded ferritin nanoparticles (Ft NPs) to regulate the nervous microenvironment, in order to control the pancreatic cancer progression. The drug-loaded Ft NPs can target pancreatic tumors via passive targeting of EPR effects of tumors and active targeting via transferrin receptor 1 (TfR1) binding on cancer cells, with a triggered drug release in acidic tumor environment. Two drugs, one activates neural activity (carbachol), the other impairs neural activity (atropine), are encapsulated into the Ft NPs to form two kinds of nano drugs, Nano-Cab NPs and Nano-Ato NPs, respectively. The activation of the nervous microenvironment by Nano-Cab NPs significantly promotes the pancreatic tumor progression, whereas the blockage of neural niche by Nano-Ato NPs remarkably impairs the neurogenesis in tumors and the progression of pancreatic cancer. The Ft-based nanoparticles thus comprise an effective and safe route of delivery of neural drugs for novel anti-cancer therapy.

New insights into perineural invasion of pancreatic cancer: More than pain

Pancreatic cancer is one of the most malignant human tumors. Perineural invasion, whereby a cancer cell invades the perineural spaces surrounding nerves, is acknowledged as a gradual contributor to cancer aggressiveness. Furthermore, perineural invasion is considered one of the root causes of the recurrence and metastasis observed after pancreatic resection, and it is also an independent predictor of prognosis. Advanced research has demonstrated that the neural microenvironment is closely associated with perineural invasion in pancreatic cancer. Therapy targeting the molecular mechanism of perineural invasion may enable the durable clinical treatment of this formidable disease. This review provides an overview of the present status of perineural invasion, the relevant molecular mechanisms of perineural invasion, pain and hyperglycemia associated with perineural invasion in pancreatic cancer, and the targeted therapeutics based on these studies.

Hypothyroidism in Pancreatic Cancer: Role of Exogenous Thyroid Hormone in Tumor Invasion-Preliminary Observations

According to the epidemiological studies, about 4.4% of American general elderly population has a pronounced hypothyroidism and relies on thyroid hormone supplements daily. The prevalence of hypothyroidism in our patients with pancreatic cancer was much higher, 14.1%. A retrospective analysis was performed on patients who underwent pancreaticoduodenectomy (Whipple procedure) or distal pancreatectomy and splenectomy (DPS) at Thomas Jefferson University Hospital, Philadelphia, from 2005 to 2012. The diagnosis of hypothyroidism was correlated with clinicopathologic parameters including tumor stage, grade, and survival. To further understand how thyroid hormone affects pancreatic cancer behavior, functional studies including wound-induced cell migration, proliferation, and invasion were performed on pancreatic cancer cell lines, MiaPaCa-2 and AsPC-1. We found that hypothyroid patients taking exogenous thyroid hormone were more than three times likely to have perineural invasion, and about twice as likely to have higher T stage, nodal spread, and overall poorer prognostic stage (P < 0.05). Pancreatic cancer cell line studies demonstrated that exogenous thyroid hormone treatment increased cell proliferation, migration, and invasion (P < 0.05). We conclude that exogenous thyroid hormone may contribute to the progression of pancreatic cancer.

Neural plasticity in pancreatitis and pancreatic cancer

Pancreatic nerves undergo prominent alterations during the evolution and progression of human chronic pancreatitis and pancreatic cancer. Intrapancreatic nerves increase in size (neural hypertrophy) and number (increased neural density). The proportion of autonomic and sensory fibres (neural remodelling) is switched, and are infiltrated by perineural inflammatory cells (pancreatic neuritis) or invaded by pancreatic cancer cells (neural invasion). These neuropathic alterations also correlate with neuropathic pain. Instead of being mere histopathological manifestations of disease progression, pancreatic neural plasticity synergizes with the enhanced excitability of sensory neurons, with Schwann cell recruitment toward cancer and with central nervous system alterations. These alterations maintain a bidirectional interaction between nerves and non-neural pancreatic cells, as demonstrated by tissue and neural damage inducing neuropathic pain, and activated neurons releasing mediators that modulate inflammation and cancer growth. Owing to the prognostic effects of pain and neural invasion in pancreatic cancer, dissecting the mechanism of pancreatic neuroplasticity holds major translational relevance. However, current in vivo models of pancreatic cancer and chronic pancreatitis contain many discrepancies from human disease that overshadow their translational value. The present Review discusses novel possibilities for mechanistically uncovering the role of the nervous system in pancreatic disease progression.

Back pain as a potential indicator of local recurrence in pancreatic cancer

Neural invasion (NI) and severe pain are common features in patients with pancreatic cancer (PCa). Here, we present the case of a 67-year-old patient with PCa whose pre- and postoperative physical situation was clearly dominated by severe pain sensation. The resected pancreas specimen revealed severe and frequent NI by cancer cells. Seven months after R1 resection and additive chemotherapy, the patient presented with severe lumbar back pain. The CT scan showed liver metastasis and local recurrence around the celiac trunk. Yet 1 month after palliative chemotherapy, the patient presented again in poor general condition and lumbar pain requiring constant morphine intake, and died 2 days after hospitalization. Postmortem histological analysis showed local recurrence with an extensive invasion by cancer cells along almost all nerves of the celiac plexus. Hence, new-onset or recurrent back and/or abdominal pain, as in this case, should raise the clinician's suspicion for local recurrence in PCa.

[Delayed complications after pancreatic surgery: Pancreatic insufficiency, malabsorption syndrome, pancreoprivic diabetes mellitus and pseudocysts]

BACKGROUND

Benign and malignant pathologies of the pancreas can result in a relevant chronic disease burden. This is aggravated by morbidities resulting from surgical resections as well as from progression of the underlying condition.

OBJECTIVE

The aim was to summarize the current evidence regarding epidemiology, pathophysiology, diagnosis and treatment of endocrine and exocrine pancreatic insufficiency, as well as of pancreatic pseudocysts.

MATERIAL AND METHODS

A selective literature search was performed and a summary of the currently available data on the surgical sequelae after pancreatic resection is given.

RESULTS

Reduction of healthy pancreatic parenchyma down to 10-15 % leads to exocrine insufficiency with malabsorption and gastrointestinal complaints. Orally substituted pancreatic enzymes are the therapy of choice. Loss of pancreatic islets and/or islet function leads to endocrine insufficiency and pancreoprivic diabetes mellitus. Inflammatory, traumatic and iatrogenic injuries of the pancreas can lead to pancreatic pseudocysts, which require endoscopic, interventional or surgical drainage if symptomatic. Finally, pancreatic surgery harbors the long-term risk of gastrointestinal anastomotic ulcers, bile duct stenosis, portal vein thrombosis and chronic pain syndrome.

CONCLUSION

As the evidence is limited, an interdisciplinary and individually tailored approach for delayed pancreatic morbidity is recommended.

Perineural invasion: a potential reason of hepatocellular carcinoma bone metastasis

The nervous system plays an important role in the regulation of epithelial homeostasis and has also been postulated to play a role in tumorigenesis. Perineural invasion (PNI) is the only interaction between cancer cells and nerves studied to date. It is a symbiotic relationship between cancer cells and nerves that result in growth advantage for both. The potential association between HCC bone metastases and PNI is unknown. In this study, we investigate the nerve density in HCC and paired bone metastases to reveal the potential association of HCC bone metastases and PNI. The nerve density was evaluated by immunohistochemistry in formalin-fixed paraffin embedded (FFPE) hepatocellular carcinoma (HCC) and paired bone metastases tissues from 13 HCC patients with synchronous or metachronous bone metastases that underwent surgical resection. FFPE specimens of HCC bone metastases tissues express higher perineural density than HCC tissues, pointing to a potential role of the PNI in bone metastases from HCC. This is the first description of the potential association of PNI and HCC bone metastases.

Factors influencing survival after pancreatoduodenectomy for ductal adenocarcinoma depend on patients' age

BACKGROUND

It is supposed that a prolonged lifetime will be associated with increased incidence of PDAC among the elderly. Some studies show a tendency toward decreased survival in the elderly patients following pancreatoduodenectomy for PDAC. The aim of this study was to evaluate factors, influencing survival following pancreatoduodenectomy for PDAC in different age groups.

METHODS

Data of 251 patients after pancreatoduodenectomy for PDAC between 1999 and 2012 were analyzed. The Kaplan-Meier method and log-rank test were used to calculate survival and to compare differences between groups. The Cox proportional hazard model was applied to indentify independent prognosticators.

RESULTS

The overall median survival was 14.9 months. Postoperative morbidity was 25.5% with a 5.1% mortality rate. No significant differences in the overall morbidity (22.4 vs. 29.6%) or mortality (2.8 vs. 8.3%) rates were observed between different patients' age groups (<70 years and >70 years). Multivariate analysis revealed R1 resection (HR 1.76) and poor tumor differentiation (G3-G4) (HR 1.48) were independent negative factors for survival in patients <70 years. Lymph-node metastases (N1) - HR 4.89 and perineural invasion - HR 2.73 were independent prognosticators in the elderly.

CONCLUSIONS

Our study highlighted different factors influencing long-term survival after pancreatoduodenectomy: R1 resection and poor tumor differentiation (G3-G4) were independent negative factors for survival in patients <70 years, while perineural invasion and lymph-node metastases result in worse survival among the elderly.

The outcome of cryoablation in treating advanced pancreatic cancer: a comparison with palliative bypass surgery alone

OBJECTIVE

This study aimed to investigate the efficacy and safety of palliative bypass surgery combined with cryoablation in treating patients with advanced pancreatic cancer and compare this combination therapy with palliative bypass surgery alone.

METHODS

Medical records of 118 patients with advanced pancreatic cancer who received palliative bypass surgery combined with cryoablation (the combination treatment group) or bypass surgery alone (the bypass surgery alone group) at the Department of Pancreatic Cancer, Tianjin Medical University Cancer Institute and Hospital (Tianjin, China) were retrospectively reviewed. Their baseline and peri-operative parameters were collected and compared.

RESULTS

In both groups abdominal distension and pain was significantly ameliorated after treatment. Preoperative jaundice was more common in the bypass surgery group while backache was more frequent in the combination treatment group, which were both relieved by treatment. The pre-operative serum bilirubin level was higher in the bypass surgery group and was decreased significantly after treatment. However, a significant reduction in tumor size and serum carbohydrate antigen 19-9 level was found only in the combination treatment group. There was no significant difference in the incidence of postoperative complications and prognosis between the two groups.

CONCLUSIONS

Cryoablation can reduce tumor size and relieve the patients' symptoms and signs such as abdominal discomfort and backache, although it could not improve the patients' prognosis significantly. It is a safe and efficient modality when combined with bypass surgery for patients with advanced pancreatic cancer.

Investigation of Schwann cells at neoplastic cell sites before the onset of cancer invasion

BACKGROUND

In neural invasion (NI), cancer cells are classically assumed to actively invade nerves and to cause local recurrence and pain. However, the opposite possibility, that nerves may reach cancer cells even in their preinvasive stage and thereby promote cancer spread, has not yet been genuinely considered. The present study analyzes the reaction of Schwann cells of peripheral nerves to carcinogenesis in pancreatic cancer and colon cancer.

METHODS

Two novel 3D migration and Schwann cell outgrowth assays were developed to monitor the timing and the specificity of Schwann cell migration and cancer invasion toward peripheral neurons through digital-time-lapse microscopy and after blockade of nerve growth factor (NGF) signalling via siRNA or a small-molecule inhibitor of the p75(NTR) receptor. The frequency and emergence of the Schwann cell markers Sox10, S100, ALDH1L1, and glial-fibrillary-acidic-protein (GFAP) around cancer precursor lesions were studied in human and conditional murine pancreatic and colon cancer specimens using multiple immunolabeling.

RESULTS

Schwann cells migrated toward pancreatic and colon cancer cells, but not toward benign cells, before the onset of cancer migration toward peripheral neurons. This chemoattraction was inhibited after blockade of p75(NTR)-signaling on Schwann and pancreatic cancer cells. Schwann cells were specifically detected around murine and human pancreatic intraepithelial neoplasias (PanINs) (mean percent of murine PanINs surrounded by Schwann cells = 78.9%, 95% CI = 70.9 to 86.8%, and mean percent of human PanINs surrounded by Schwann cells = 52.5%, 95% CI = 14.7 to 90.4%; human: n = 44, murine: n = 14) and intestinal adenomas (mean percent of murine adenomas surrounded by Schwann cells = 64.2%, 95% CI = 28.6 to 99.8%, and mean percent of human adenomas surrounded by Schwann cells = 17.2%, 95% CI = -126.9 to 161.4; human: n = 36, murine: n = 12). The Schwann cell presence in this premalignant stage was associated with the frequency of NI in the malignant phase.

CONCLUSIONS

Schwann cells have particular and specific affinity to cancer cells. Emergence of Schwann cells in the premalignant phase of pancreatic and colon cancer implies that, in contrast with the traditional assumption, nerves-and not cancer cells-migrate first during NI.

Simulating pancreatic neuroplasticity: in vitro dual-neuron plasticity assay

Neuroplasticity is an inherent feature of the enteric nervous system and gastrointestinal (GI) innervation under pathological conditions. However, the pathophysiological role of neuroplasticity in GI disorders remains unknown. Novel experimental models which allow simulation and modulation of GI neuroplasticity may enable enhanced appreciation of the contribution of neuroplasticity in particular GI diseases such as pancreatic cancer (PCa) and chronic pancreatitis (CP). Here, we present a protocol for simulation of pancreatic neuroplasticity under in vitro conditions using newborn rat dorsal root ganglia (DRG) and myenteric plexus (MP) neurons. This dual-neuron approach not only permits monitoring of both organ-intrinsic and -extrinsic neuroplasticity, but also represents a valuable tool to assess neuronal and glial morphology and electrophysiology. Moreover, it allows functional modulation of supplied microenvironmental contents for studying their impact on neuroplasticity. Once established, the present neuroplasticity assay bears the potential of being applicable to the study of neuroplasticity in any GI organ.

RAN GTPase and Osteopontin in Pancreatic Cancer

INTRODUCTION

Pancreatic ductal adenocarcinoma (PDA) has the worst prognosis among cancers, mainly due to the high incidence of early metastases. RAN small GTPase (RAN) is a protein that plays physiological roles in the regulation of nuclear transport and microtubule spindle assembly. RAN was recently shown to mediate the invasive functions of the prometastatic protein osteopontin (OPN) in breast cancer cells. We and others have shown previously that high levels of OPN are present in PDA. In this study, we analyzed the expression and correlation of RAN with OPN in human pancreatic lesions, and explored their regulation in PDA cell lines.

METHODS

Real time PCR was used to analyze RAN and OPN mRNA levels in PDA, adjacent non-malignant, and benign pancreatic tissues. Expression levels were correlated with survival and different clinicopathological parameters using different statistical methods. Transient transfection studies using OPN and RAN plasmids, and knockdown experiments using siRNA were used to examine their mutual regulation.

RESULTS

OPN and RAN levels highly correlated with each other (p<0.0001). OPN or RAN levels did not correlate with venous lymphatic invasion, diabetes, obesity, T stage, BMI, or survival. However, we found a significant association between RAN levels and perineural invasion (HR=0.79, 95% CI 0.59, 1.07; p=0.0378.). OPN and RAN colocalized in PDA tissues and cell lines. Increasing RAN expression in PDA cells induced OPN transcription and RAN silencing reduced total OPN levels. OPN did not have any significant effect on RAN transcription.

CONCLUSIONS

The high levels of RAN in PDA and its correlation with OPN and with perineural invasion suggest that RAN may contribute to PDA metastasis and progression through the induction of OPN. RAN's role in the regulation of OPN in PDA is unique and could provide potential novel therapeutic strategies to combat PDA aggressiveness.

Neural plasticity in the gastrointestinal tract: chronic inflammation, neurotrophic signals, and hypersensitivity

Neural plasticity is not only the adaptive response of the central nervous system to learning, structural damage or sensory deprivation, but also an increasingly recognized common feature of the gastrointestinal (GI) nervous system during pathological states. Indeed, nearly all chronic GI disorders exhibit a disease-stage-dependent, structural and functional neuroplasticity. At structural level, GI neuroplasticity usually comprises local tissue hyperinnervation (neural sprouting, neural, and ganglionic hypertrophy) next to hypoinnervated areas, a switch in the neurochemical (neurotransmitter/neuropeptide) code toward preferential expression of neuropeptides which are frequently present in nociceptive neurons (e.g., substance P/SP, calcitonin-gene-related-peptide/CGRP) and of ion channels (TRPV1, TRPA1, PAR2), and concomitant activation of peripheral neural glia. The functional counterpart of these structural alterations is altered neuronal electric activity, leading to organ dysfunction (e.g., impaired motility and secretion), together with reduced sensory thresholds, resulting in hypersensitivity and pain. The present review underlines that neural plasticity in all GI organs, starting from esophagus, stomach, small and large intestine to liver, gallbladder, and pancreas, actually exhibits common phenotypes and mechanisms. Careful appraisal of these GI neuroplastic alterations reveals that--no matter which etiology, i.e., inflammatory, infectious, neoplastic/malignant, or degenerative--neural plasticity in the GI tract primarily occurs in the presence of chronic tissue- and neuro-inflammation. It seems that studying the abundant trophic and activating signals which are generated during this neuro-immune-crosstalk represents the key to understand the remarkable neuroplasticity of the GI tract.

Perineural mast cells are specifically enriched in pancreatic neuritis and neuropathic pain in pancreatic cancer and chronic pancreatitis

BACKGROUND

Pancreatic neuritis is a histopathological hallmark of pancreatic neuropathy and correlates to abdominal neuropathic pain sensation in pancreatic adenocarcinoma (PCa) and chronic pancreatitis (CP). However, inflammatory cell subtypes that compose pancreatic neuritis and their correlation to the neuropathic pain syndrome in PCa and CP are yet unknown.

METHODS

Inflammatory cells within pancreatic neuritis lesions of patients with PCa (n = 20) and CP (n = 20) were immunolabeled and colorimetrically quantified with the pan-leukocyte marker CD45, with CD68 (macrophages), CD8 (cytotoxic T-lymphocytes), CD4 (T-helper cells), CD20 (B-lymphocytes), NCL-PC (plasma cells), neutrophil elastase, PRG2 (eosinophils), anti-mast cell (MC) tryptase and correlated to pain sensation. Perineural mast cell subtypes were analyzed by double immunolabeling with MC chymase. Expression and neural immunoreactivity of protease-activated receptor type 1 (PAR-1) and type 2 (PAR-2) were analyzed in PCa and CP and correlated to pain status of the patients.

RESULTS

In PCa and CP, nerves were predominantly infiltrated by cytotoxic T-lymphocytes (PCa: 35% of all perineural inflammatory cells, CP: 33%), macrophages (PCa: 39%, CP: 33%) and MC (PCa: 21%, CP: 27%). In both entities, neuropathic pain sensation was associated with a specific increase of perineural MC (PCa without pain: 14% vs. PCa with pain: 31%; CP without pain: 19% vs. CP with pain: 34%), not affecting the frequency of other inflammatory cell subtypes. The vast majority of these MC contained MC chymase. PAR-1 and PAR-2 expression did not correlate to the pain sensation of PCa and CP patients.

CONCLUSION

Pancreatic neuritis in PC and CP is composed of cytotoxic T-lymphocytes, macrophages and MC. The specific enrichment of MC around intrapancreatic nerves in neuropathic pain due to PCa and CP suggests the presence of MC-induced visceral hypersensitivity in the pancreas. Therefore, pancreatic and enteric neuropathies seem to share a similar type of neuro-immune interaction in the generation of visceral pain.

Interaction of the sympathetic nerve with pancreatic cancer cells promotes perineural invasion through the activation of STAT3 signaling

Perineural invasion (PNI) is one of the most important causes of local recurrence and poor survival in pancreatic cancer. However, the exact mechanism of PNI is still not clear. In this study, we sought to identify the reciprocal signaling interactions between sympathetic nerves and pancreatic cancer cells and the underlying mechanisms. We used mouse dorsal root ganglia and pancreatic cancer cells cocultured in vitro, cellular and molecular biology, and animal models to evaluate the function of the sympathetic neurotransmitter norepinephrine (NE) in PNI progression and pathogenesis. NE promoted PNI of pancreatic cancer cells and increased levels of phosphorylated STAT3 in a concentration-dependent manner. NE-mediated activation of STAT3 was inhibited by blocking β-adrenergic receptors (AR) and by blocking protein kinase A, but not through blocking α-AR. Blocking STAT3 could inhibit NE-induced NGF, MMP2, and MMP9 expression and attenuate the migratory, invasive ability and PNI of pancreatic cancer cells. Furthermore, PNI of pancreatic cancer cells was blocked by treatment with a STAT3 phosphorylation inhibitor in vivo. These studies show that NE plays a critical role in pancreatic cancer PNI development and progression through the β-AR/PKA/STAT3 signaling pathway. Reciprocal signaling interactions between the sympathetic nerves and pancreatic cancer cells critically contribute to pancreatic cancer PNI pathogenesis. Inhibition of the activity of sympathetic nerves or STAT3 may be potential strategies for pancreatic cancer PNI therapy.

Analysis of tumor-induced lymphangiogenesis and lymphatic vessel invasion of pancreatic carcinoma in the peripheral nerve plexus

Cancer cells can metastasize throughout the body by various mechanisms, including the lymphatic system, resulting in tumor-induced lymphangiogenesis that can profoundly affect patient survival. The aim of the present study was to examine the role of lymphangiogenesis in the metastasis of pancreatic cancer to the peripheral nerve plexus. Immunohistochemistry was performed to analyze specimens obtained from 70 ductal adenocarcinoma patients. The markers used included lymphangiogenic factor vascular endothelial growth factor (VEGF)-C, the lymphatic-specific marker D2-40, and cytokeratin 19, an independent prognostic factor for pancreatic tumors. The relationship between survival rate and invasion of both the lymphatic vessels and peripancreatic nerve plexus (PNP) was evaluated, with clearly elevated lymphatic vessel density (LVD) in tissues adjacent to the cancer tissues. In fact, LVD levels were higher in adjacent tissues than in localized cancer tissues, and lymphatic vessel invasion into tissues adjacent to the tumor was significantly correlated with both PNP invasion (P = 0.005) and lymph node metastasis (P = 0.010). Correspondingly, LVD in tissues adjacent to the tumor was correlated with both invasion of lymphatic vessels surrounding the tumor (P = 0.024) and VEGF-C expression (P = 0.031); in addition, VEGF-C expression was correlated with invasion of lymphatic vessels around the tumor (P = 0.004). Survival rates were significantly lower in patients in whom there was peritumor lymphatic vessel invasion (P < 0.001), extrapancreatic nerve plexus invasion (P = 0.001), and/or lymph node metastasis (P < 0.001). Based on these results, lymphatic invasion associated with adjacent tumor growth likely contributes to the development of metastatic tumors that invade the PNP.

Nerve-cancer interactions in the stromal biology of pancreatic cancer

Interaction of cancer cells with diverse cell types in the tumor stroma is today recognized to have a fate-determining role for the progression and outcome of human cancers. Despite the well-described interactions of cancer cells with several stromal components, i.e., inflammatory cells, cancer-associated fibroblasts, endothelial cells, and pericytes, the investigation of their peculiar relationship with neural cells is still at its first footsteps. Pancreatic cancer (PCa) with its abundant stroma represents one of the best-studied examples of a malignant tumor with a mutually trophic interaction between cancer cells and the intratumoral nerves embedded in the desmoplastic stroma. Nerves in PCa are a rich source of neurotrophic factors like nerve growth factor (NGF), glial-cell-derived neurotrophic factor (GDNF), artemin; of neuronal chemokines like fractalkine; and of autonomic neurotransmitters like norepinephrine which can all enhance the invasiveness of PCa cells via matrix-metalloproteinase (MMP) upregulation, trigger neural invasion (NI), and activate pro-survival signaling pathways. Similarly, PCa cells themselves provide intrapancreatic nerves with abundant trophic agents which entail a remarkable neuroplasticity, leading to emergence of more routes for NI and cancer spread, to augmented local neuro-surveillance, neural sensitization, and neuropathic pain. The strong correlation of NI with PCa-associated desmoplasia suggests the potential presence of a triangular relationship between nerves, PCa cells, and other stromal partners like myofibroblasts and pancreatic stellate cells which generate tumor desmoplasia. Hence, although not a classical hallmark of human cancers, nerve-cancer interactions can be considered as an indispensable sub-class of cancer-stroma interactions in PCa. The present article provides an overview of the so far known nerve-cancer interactions in PCa and illustrates their ominous role in the stromal biology of human PCa.

Perineural invasion and associated pain in pancreatic cancer

Perineural invasion (PNI) is a prominent characteristic of pancreatic cancer. PNI is a process whereby cancer cells invade the surrounding nerves, thus providing an alternative route for metastatic spread and pain generation. PNI is thought to be an indicator of aggressive tumour behaviour and has been shown to correlate with poor prognosis of patients with pancreatic cancer. Recent studies demonstrated that some signalling molecules and pathways that are involved in PNI are also involved in pain generation. Targeting these signalling pathways has shown some promise in alleviating pain and reducing PNI, which could potentially improve treatment outcomes for patients with pancreatic cancer.