Enhanced survival in perineural invasion of pancreatic cancer: an in vitro approach

Three-Dimensional Gastrointestinal Organoid Culture in Combination with Nerves or Fibroblasts: A Method to Characterize the Gastrointestinal Stem Cell Niche

The gastrointestinal epithelium is characterized by a high turnover of cells and intestinal stem cells predominantly reside at the bottom of crypts and their progeny serve to maintain normal intestinal homeostasis. Accumulating evidence demonstrates the pivotal role of a niche surrounding intestinal stem cells in crypts, which consists of cellular and soluble components and creates an environment constantly influencing the fate of stem cells. Here we describe different 3D culture systems to culture gastrointestinal epithelium that should enable us to study the stem cell niche in vitro in the future: organoid culture and multilayered systems such as organotypic cell culture and culture of intestinal tissue fragments ex vivo. These methods mimic the in vivo situation in vitro by creating 3D culture conditions that reflect the physiological situation of intestinal crypts. Modifications of the composition of the culture media as well as coculturing epithelial organoids with previously described cellular components such as myofibroblasts, collagen, and neurons show the impact of the methods applied to investigate niche interactions in vitro. We further present a novel method to isolate labeled nerves from the enteric nervous system using Dclk1-CreGFP mice.

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.

Interaction Between Gastric Carcinoma Cells and Neural Cells Promotes Perineural Invasion by a Pathway Involving VCAM1

BACKGROUND

Perineural invasion (PNI) is one of the important routes for local spread of gastric carcinoma associated with poor prognosis. However, the exact cellular characteristics and molecular mechanisms of PNI are still unclear.

AIM

To identify the interaction between gastric carcinoma cells and neural cells, and whether vascular cell adhesion molecule-1 (VCAM1) is involved in this process.

METHODS

We adopted in vitro cell coculture assays to investigate the cellular and molecular interaction between gastric cancer cells and neural cells.

RESULTS

We find upregulation of VCAM1 in clinical gastric cancer tissue samples. In in vitro tumor-neural cell coculture system, gastric cancer cells with high level of VCAM1 promote proliferation of neural progenitor cells and induce the process outgrowth and branching of neural cells. Reciprocally, neural cells enhance neurotropic migration and mobility of tumor cells. Repressing VCAM1 function through VCAM1 blocking antibody can attenuate these effects.

CONCLUSIONS

Our study indicates that VCAM1 is significantly involved in tumor invasion via mediating nerve-tumor interaction, which is a mutually beneficial process. It is possible that interaction between neural cells and tumor cells might contribute to PNI of gastric carcinoma. Inhibiting the activity of VCAM1 could be a potential strategy targeting PNI in gastric carcinoma therapy.

Role of the autonomic nervous system in tumorigenesis and metastasis

Convergence of multiple stromal cell types is required to develop a tumorigenic niche that nurtures the initial development of cancer and its dissemination. Although the immune and vascular systems have been shown to have strong influences on cancer, a growing body of evidence points to a role of the nervous system in promoting cancer development. This review discusses past and current research that shows the intriguing role of autonomic nerves, aided by neurotrophic growth factors and axon cues, in creating a favorable environment for the promotion of tumor formation and metastasis.

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.

Depletion of RhoGDI2 expression inhibits the ability of invasion and migration in pancreatic carcinoma

Rho GDP dissociation inhibitor 2 (RhoGDI2) has been identified as a regulator of tumor metastasis, although its role in tumor progression remains controversial. In this study, we examined the expression of RhoGDI2 in PC tissues and cell lines. To investigate the function of RhoGDI2 in PC cells, RhoGDI2 expression was depleted in PANC-1 and Patu8988 cells by small interfering RNA (siRNA). RhoGDI2 was found to be overexpressed in pancreatic carcinoma (PC) tissues and PC cell lines. Additionally, the results showed that depletion of RhoGDI2 significantly inhibited cell motility and invasion in vitro, but did not affect cell proliferation. The clinical study together with the experimental data confirmed that RhoGDI2 modulated the expression of matrix metalloproteinase 2 (MMP2). Taken together, findings of the present study indicated that RhoGDI2 is involved in pancreatic tumor malignancy and metastasis. Thus, RhoGDI2 is a potential target for the gene therapy of PC.

Prognostic impact of M2 macrophages at neural invasion in patients with invasive ductal carcinoma of the pancreas

BACKGROUND

Neural invasion is a characteristic pattern of invasion and an important prognostic factor for invasive ductal carcinoma (IDC) of the pancreas. M2 macrophages have reportedly been associated with poor prognosis in various cancers. The aim of the present study was to investigate the prognostic impact of M2 macrophages at extrapancreatic nerve plexus invasion (plx-inv) of pancreatic IDC.

METHODS

Participants comprised 170 patients who underwent curative pancreaticoduodenectomy for pancreatic IDC. Immunohistochemical examination of surgical specimens was performed by using CD204 as an M2 macrophage marker, and the area of immunopositive cells was calculated automatically. Prognostic analyses of clinicopathological factors including CD204-positive cells at plx-inv were performed.

RESULTS

Plx-inv was observed in 91 patients (53.5%). Forty-eight patients showed a high percentage of CD204-positive cell area at plx-inv (plx-inv CD204%(high)). Plx-inv CD204%(high) was an independent predictor of poor outcomes for overall survival (OS) (P<0.001) and disease-free survival (DFS) (P<0.001). Patients with plx-inv CD204%(high) showed a shorter time to peritoneal dissemination (P<0.001) and locoregonal recurrence (P<0.001). In patients who underwent adjuvant chemotherapy, plx-inv CD204%(high) was correlated with shorter OS (P=0.011) and DFS (P=0.038) in multivariate analysis.

CONCLUSIONS

Plx-inv CD204%(high) was associated with shortened OS and DFS and early recurrence in the peritoneal cavity and locoregional space. The prognostic value of plx-inv CD204%(high) was also applicable to patients who received adjuvant chemotherapy. High accumulation of M2 macrophages at plx-inv represents an important predictor of poor prognosis.

Biological correlates of prostate cancer perineural invasion diameter

Perineural invasion is a symbiotic relationship between cancer cells and nerves and is most frequently seen in "neurotropic" cancers such as prostate cancer. It results in increased perineural space cancer cell growth and decreased apoptosis and induces nerve growth. Tissue microarrays were constructed from 640 radical prostatectomy specimens with prostate cancer. The perineural diameter was measured as previously described. Multiple biomarkers have been previously performed on this tissue microarray cohort, and all data were kept in the same database. The biomarker results database was queried for correlations between perineural invasion diameter and tissue biomarkers. Increased perineural invasion diameter correlated with increased proliferation of prostate cancer cells and with apoptosis. It also correlated with proteins involved in survival pathways such as nuclear factor κB, c-Myc, phosphorylated AKT, and its downstream effector FHKR, but not with GSK. Unlike nerve density, it did not correlate with decreased PTEN expression. Increased perineural invasion diameter was associated with higher levels of hormonal receptors such as androgen receptor, but not estrogen receptor. Also associated with perineural invasion diameter were coregulators and corepressors including SRC1 and TIF2. Perineural invasion diameter had the strongest correlation with tumor volume (ρ = 0.579, P = .000), not identified with nerve density. These data demonstrate that perineural invasion has the same biologic correlations as neural density. However, we found a distinct and very strong correlation with increased tumor volume. These data confirm that perineural invasion is the ultimate and most successful interaction between cancer cells and nerve fibers, resulting in increased tumor growth.

IB4(+) and TRPV1(+) sensory neurons mediate pain but not proliferation in a mouse model of squamous cell carcinoma

Background

Cancer pain severely limits function and significantly reduces quality of life. Subtypes of sensory neurons involved in cancer pain and proliferation are not clear.

Methods

We produced a cancer model by inoculating human oral squamous cell carcinoma (SCC) cells into the hind paw of athymic mice. We quantified mechanical and thermal nociception using the paw withdrawal assays. Neurotoxins isolectin B4-saporin (IB4-SAP), or capsaicin was injected intrathecally to selectively ablate IB4(+) neurons or TRPV1(+) neurons, respectively. JNJ-17203212, a TRPV1 antagonist, was also injected intrathecally. TRPV1 protein expression in the spinal cord was quantified with western blot. Paw volume was measured by a plethysmometer and was used as an index for tumor size. Ki-67 immunostaining in mouse paw sections was performed to evaluate cancer proliferation in situ.

Results

We showed that mice with SCC exhibited both mechanical and thermal hypersensitivity. Selective ablation of IB4(+) neurons by IB4-SAP decreased mechanical allodynia in mice with SCC. Selective ablation of TRPV1(+) neurons by intrathecal capsaicin injection, or TRPV1 antagonism by JNJ-17203212 in the IB4-SAP treated mice completely reversed SCC-induced thermal hyperalgesia, without affecting mechanical allodynia. Furthermore, TRPV1 protein expression was increased in the spinal cord of SCC mice compared to normal mice. Neither removal of IB4(+) or TRPV1(+) neurons affected SCC proliferation.

Conclusions

We show in a mouse model that IB4(+) neurons play an important role in cancer-induced mechanical allodynia, while TRPV1 mediates cancer-induced thermal hyperalgesia. Characterization of the sensory fiber subtypes responsible for cancer pain could lead to the development of targeted therapeutics.

Recombinant lentivirus targeting the pleotrophin gene reduces pleotrophin protein expression in pancreatic cancer cells and inhibits neurite outgrowth of dorsal root ganglion neurons

The objectives of the present study were to construct the recombinant primate lentivirus‑short hairpin RNA-pleiotrophin (pLV-shRNA-PTN) vector, to investigate the silencing effect of pLV-shRNA-PTN on PTN expression in MIA PaCa-2 cells and to observe the inhibition efficiency of pLV-shRNA‑PTN on neurite outgrowth from dorsal root ganglion (DRG) neurons in vitro. The construction procedure for recombinant lentivirus pLV-shRNA-PTN has been described previously. In the present study, pLV-shRNA‑PTN was used to infect MIA PaCa-2 pancreatic cancer cells and the efficiency of the knockdown of the PTN gene on day 7 following infection was analyzed using western blotting. The morphological changes in the cultured DRG neurons were observed by monoculture of DRG neurons and co-culture with MIA PaCa-2 cells in vitro. The recombinant lentivirus pLV-shRNA‑PTN was successfully constructed. The western blot analysis showed that the inhibition rates of PTN expression were 46, 80, 20 and 21%, respectively, following pLV-shRNA‑PTN-A, B, C and D infection. pLV-shRNA-PTN‑B showed the highest knockdown efficiency. DRG neurons co-cultured with infected MIA PaCa-2 cells were decreased in size when compared with the control, and there was a significant decrease in the number and length of neurites. The results suggest that efficient and specific knockdown of PTN in MIA PaCa-2 pancreatic cancer cells and the subsequent reduction in PTN expression results in the inhibition of neurite outgrowth from DRG neurons.

Perineural invasion of head and neck skin cancer: diagnostic and therapeutic implications

Perineural invasion of head and neck skin cancer is a poorly understood and often misdiagnosed pathological entity. Incidental or microscopic perineural invasion is identified by the pathologist and often leads to confusion as to how the patient should be further treated. The less common but more aggressive clinical perineural spread presents with a clinical deficit, which is too commonly misinterpreted by the clinician. This review will try to clarify the terminology that exists in the literature and explore the mechanisms of invasion and spread. It will look at the recent advances in diagnosis and comment on the limitations inherent in current classification schemes. A review of outcomes will be included and current treatment strategies utilized discussed.

Therapeutic potential of perineural invasion, hypoxia and desmoplasia in pancreatic cancer

Pancreatic cancer is one of the most fatal human malignancies. Though a relatively rare malignancy, it remains one of the deadliest tumors, with an extremely high mortality rate. The prognosis of patients with pancreatic cancer remains poor; only patients with small tumors and complete resection have a chance of a complete cure. Pancreatic cancer responds poorly to conventional therapies, including chemotherapy and irradiation. Tumor-specific targeted therapy is a relatively recent addition to the arsenal of anti-cancer therapies. It is important to find novel targets to distinguish tumor cells from their normal counterparts in therapeutic approaches. In the past few decades, studies have revealed the molecular mechanisms of pancreatic tumorigenesis, growth, invasion and metastasis. The proteins that participate in the pathophysiological processes of pancreatic cancer might be potential targets for therapy. This review describes the main players in perineural invasion, hypoxia and desmoplasia and the molecular mechanisms of these pathophysiological processes.

Targeting the cancer-stroma interaction: a potential approach for pancreatic cancer treatment

Recent studies have demonstrated that the interaction between the cancer and the stroma, play a key role in the development of pancreatic cancer. The desmoplasia, which consists of fibroblasts, pancreatic stellate cells, lymphatic and vascular endothelial cells, immune cells, pathologic increased nerves, and the extracellular matrix (ECM), creates a complex tumor microenvironment that promotes pancreatic cancer development, invasion, metastasis, and resistance to chemotherapy. Thus, the potential approach for targeting the components of this desmoplastic reaction or the pancreatic tumor microenvironment might represent a novel therapeutic approach to advanced pancreatic carcinoma. Novel therapies that target on the pancreatic tumor microenvironment should become one of the more effective treatments for pancreatic cancer.

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.

Syndecan-2 promotes perineural invasion and cooperates with K-ras to induce an invasive pancreatic cancer cell phenotype

Background

We have identified syndecan-2 as a protein potentially involved in perineural invasion of pancreatic adenocarcinoma (PDAC) cells.

Methods

Syndecan-2 (SDC-2) expression was analyzed in human normal pancreas, chronic pancreatitis and PDAC tissues. Functional in vitro assays were carried out to determine its role in invasion, migration and signaling.

Results

SDC-2 was expressed in the majority of the tested pancreatic cancer cell lines while it was upregulated in nerve-invasive PDAC cell clones. There were 2 distinct expression patterns of SDC-2 in PDAC tissue samples: SDC-2 positivity in the cancer cell cytoplasm and a peritumoral expression. Though SDC-2 silencing (using specific siRNA oligonucleotides) did not affect anchorage-dependent growth, it significantly reduced cell motility and invasiveness in the pancreatic cancer cell lines T3M4 and Su8686. On the transcriptional level, migration-and invasion-associated genes were down-regulated following SDC-2 RNAi. Furthermore, SDC-2 silencing reduced K-ras activity, phosphorylation of Src and - further downstream - phosphorylation of ERK2 while levels of the putative SDC-2 signal transducer p120GAP remained unaltered.

Conclusion

SDC-2 is a novel (perineural) invasion-associated gene in PDAC which cooperates with K-ras to induce a more invasive phenotype.

Extrahepatic bile duct cancer: invasion of the posterior hepatic plexuses--evaluation using multidetector CT

PURPOSE

To assess the utility of axial and coronal reformatted multidetector computed tomographic (CT) images in the evaluation of the invasion of posterior hepatic plexuses by extrahepatic bile duct cancer.

MATERIALS AND METHODS

This retrospective study was approved by the institutional review board, and informed consent was waived. Forty-three patients (22 men, 21 women; age range, 40-80 years; mean age, 65 years) with surgically resected cancer involving the extrahepatic bile duct between December 2004 and September 2010 were included. Posterior hepatic plexus 1 runs from the superior and middle bile duct to the right celiac ganglion, and posterior hepatic plexus 2 runs between the lower bile duct and right celiac ganglion behind the portal vein. Invasion of the posterior hepatic plexuses was elucidated by using pathologic and postoperative multidetector CT findings. Three radiologists independently evaluated the preoperative axial and coronal reformatted images with a separate viewing session for the invasion of posterior hepatic plexuses that was detected on the basis of the presence of increased attenuation of fat tissue along the nerve routes. Receiver operating characteristic analysis was performed to compare the diagnostic performance of the two image interpretations.

RESULTS

Invasion of posterior hepatic plexus 1 and of posterior hepatic plexus 2 was recognized in 10 (23%) and nine (21%) of 43 patients, respectively. The diagnostic performance of coronal reformatted image interpretation was significantly greater than that for axial image interpretation (mean area under the curve, 0.99 vs 0.89, P = .04; mean accuracy, 95% vs 82%, P = .003). In all reviewers, one false-positive diagnosis of the invasion of posterior hepatic plexus occurred on axial and/or coronal image display types because of fibrosis and inflammatory cell infiltration along these plexus routes.

CONCLUSION

Coronal reformatted images can be useful for accurate diagnosis of the invasion of posterior hepatic plexuses and may facilitate surgical decision making in regard to the resection of celiac ganglion.

Elevated lysosome-associated protein transmembrane-4β-35 is an independent prognostic marker in pancreatic carcinoma

OBJECTIVES

To investigate the relationship between lysosome-associated protein transmembrane-4β-35 (LAPTM4B-35) and the clinicopathological features and prognosis of pancreatic carcinoma.

METHODS

The level of LAPTM4B-35 protein was determined by semi quantitative immunohistochemistry in pancreatic carcinoma specimens. The relationship between LAPTM4B-35 level and prognosis was determined using univariate and multivariate analyses.

RESULTS

A total of 98 patient samples were included. The presence of LAPTM4B-35 protein was confirmed in 77/98 (78.6%) patients and was significantly associated with tumour stage, degree of differentiation and pathological staging of pancreatic carcinoma after primary surgery. Patients with high LAPTM4B-35 levels had a poorer overall survival compared with patients with lower levels. Multivariate analysis showed that LAPTM4B-35 was an independent prognostic factor for overall survival.

CONCLUSIONS

LAPTM4B-35 was found to be present at high levels in a large proportion of patients with pancreatic carcinoma, and was closely related to disease progression and poor prognosis. LAPTM4B-35 may represent a new molecular target for the clinical evaluation and treatment of pancreatic carcinoma.

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.

PAd-shRNA-PTN reduces pleiotrophin of pancreatic cancer cells and inhibits neurite outgrowth of DRG

AIM: To investigate the silencing effects of pAd-shRNA-pleiotrophin (PTN) on PTN in pancreatic cancer cells, and to observe the inhibition of pAd-shRNA-PTN on neurite outgrowth from dorsal root ganglion (DRG) neurons in vitro.

METHODS: PAd-shRNA-PTN was used to infect pancreatic cancer BxPC-3 cells; assays were conducted for knockdown of the PTN gene on the 0th, 1st, 3rd, 5th, 7th and 9th d after infection using immunocytochemistry, real-time quantitative polymerase chain reaction (PCR), and Western blotting analysis. The morphologic changes of cultured DRG neurons were observed by mono-culture of DRG neurons and co-culture with BXPC-3 cells in vitro.

RESULTS: The real-time quantitative PCR showed that the inhibition rates of PTN mRNA expression in the BxPC-3 cells were 20%, 80%, 50% and 25% on the 1st, 3rd, 5th and 7th d after infection. Immunocytochemistry and Western blotting analysis also revealed the same tendency. In contrast to the control, the DRG neurons co-cultured with the infected BxPC-3 cells shrunk; the number and length of neurites were significantly decreased.

CONCLUSION: Efficient and specific knockdown of PTN in pancreatic cancer cells and the reduction in PTN expression resulted in the inhibition of neurite outgrowth from DRG neurons.

The neuronal influence on tumor progression

Nerve fibers accompany blood and lymphatic vessels all over the body. An extensive amount of knowledge has been obtained with regard to tumor angiogenesis and tumor lymphangiogenesis, yet little is known about the potential biological effects of "neoneurogenesis". Cancer cells can exploit the advantage of the factors released by the nerve fibers to generate a positive microenvironment for cell survival and proliferation. At the same time, they can stimulate the formation of neurites by secreting neurotrophic factors and axon guidance molecules. The neuronal influence on the biology of a neoplasm was initially described several decades ago. Since then, an increasing amount of experimental evidence strongly suggests the existence of reciprocal interactions between cancer cells and nerves in humans. Moreover, researchers have been able to demonstrate a crosstalk between cancer cells and nerve fibers as a strategy for survival. Despite all these evidence, a lot remains to be done in order to clarify the role of neurotransmitters, neuropeptides, and their associated receptor-initiated signaling pathways in the development and progression of cancer, and response to therapy. A global-wide characterization of the neurotransmitters or neuropeptides present in the tumor microenvironment would provide insights into the real biological influences of the neuronal tissue on tumor progression. This review is intended to discuss our current understanding of neurosignaling in cancer and its potential implications on cancer prevention and therapy. The review will focus on the soluble factors released by cancer cells and nerve endings, their biological effects and their potential relevance in the treatment of cancer.

Relationship between neural alteration and perineural invasion in pancreatic cancer patients with hyperglycemia

BACKGROUND

Patients with higher levels of fasting serum glucose have higher death rates from pancreatic cancer compared to patients with lower levels of fasting serum glucose. However, the reasons have not been studied. The goal of the current study was to examine the neural alterations in pancreatic cancer patients with hyperglycemia and to identify the relationship between the neural alterations and perineural invasion.

METHODOLOGY/PRINCIPAL FINDINGS

The clinical and pathological features of 61 formalin-fixed pancreatic cancer specimens and 10 normal pancreases as controls were analyzed. Furthermore, the expression of Protein Gene Product 9.5 (PGP9.5), Myelin P0 protein (MPP), NGF, TrkA, and p75 were examined by immunohistochemistry. The median number of nerves, the median area of neural tissue, and the median nerve diameter per 10 mm(2) were larger in the hyperglycemia group than those in the euglycemia group (p = 0.007, p = 0.009, and p = 0.004, respectively). The integrated optical density (IOD) of MPP staining was lower in the hyperglycemia group than those in the euglycemia group (p = 0.019), while the expression levels of NGF and p75 were higher in the hyperglycemia group than those in the euglycemia group (p = 0.002, and p = 0.026, respectively). The nerve bundle invasion of pancreatic cancer was more frequent in the hyperglycemia group than in the euglycemia group (p = 0.000).

CONCLUSIONS/SIGNIFICANCE

Nerve damage and regeneration occur simultaneously in the tumor microenvironment of pancreatic cancer patients with hyperglycemia; the simultaneous occurrence may aggravate the process of perineural invasion. The abnormal expression of NGF and p75 may also be involved in this process and subsequently lead to a lower rate of curative surgery.

Arterial anatomy of the pancreas. Part 3: segmented computed tomography-angiography mapping of perineural invasion

This is the third in a series of medical graphics articles featuring the arterial anatomy of the pancreas as depicted on segmented computed tomography-angiography. These segmented computed tomography-angiography displays serve as a road map of the routes of tumor spread by ductal adenocarcinoma of the pancreas because perineural tumor invasion parallels the pancreatic arteries.

High glucose promotes cell proliferation and enhances GDNF and RET expression in pancreatic cancer cells

Hyperglycemia promotes pancreatic cancer progression, while the underlying mechanism is uncertain. We investigated the cell proliferation, glial cell line-derived neurotrophic factor (GDNF) and its tyrosine kinase receptor RET expression in BxPC-3 and MIA PaCa-2 cells when exposed to different concentrations of glucose. Proliferation of both cells was effected by glucose in a concentration-dependent manner. Definite expression of GDNF and RET was detected in both cells. Glucose concentrations could alter the expression of GDNF and RET in a concentration-dependent manner, correspondingly with the alterations of cell proliferation. Up-regulation of GDNF and RET ligand-receptor interaction might participate in the glucose-induced cancer progression.

Nerve invasion distance is dependent on laminin gamma2 in tumors of pancreatic cancer

The distance of nerve invasion is an important prognostic factor in pancreatic cancer. The extracellular matrix (ECM) of nerve, mainly composed of laminin, collagen IV and anchoring fibrils, might affect nerve invasion. However, this relationship has not been demonstrated. Our study aimed at discovering the promoting factor of nerve invasion within the tumoral ECM. An animal model was established to evaluate the distance of nerve invasion in murine sciatic nerves by intraneural injection of 6 human pancreatic cancer cell lines. mRNA expression of laminins and anchoring fibrils was compared to the distance of nerve invasion for each cancer cell line. A target molecule provided the strong association between mRNA expression and the distance of nerve invasion. To evaluate the role of a target molecule in nerve invasion, protein expression and function were examined using an animal model and surgical cases. Cancer cells with high laminin gamma2 mRNA and protein expression in their basement membranes were associated with long nerve invasion. Knockdown of laminin gamma2 in cancer cells significantly shortened nerve invasion in the animal model. In 75 patients with pancreatic cancer, a large distance of nerve invasion was associated with high expression levels of laminin gamma2 mRNA and basement membranous deposition of laminin gamma2 protein. Our results indicate that laminin gamma2 plays an important role in nerve invasion. The measurement of the nerve invasion distance in our mouse nerve invasion model is useful for evaluating the molecular mechanisms of nerve invasion.

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

In the past 15 years, invasion of nerves by cancer cells has escaped from its role as a mere bystander in cancer biology and turned into an attractive niche to study the heterotypic interaction between cancer cells and neurons. Today, neural invasion (NI) in pancreatic cancer (PCa) stands out due to the recent demonstration of its association with tumor progression, local recurrence and neuropathic pain. Accordingly, recent research on NI in PCa revealed the critical involvement of numerous nerve- or cancer cell-derived molecules in several novel in vitro and in vivo models of NI, which, however, still need further major improvement.

The laminin binding integrin alpha6beta1 in prostate cancer perineural invasion

Metastasizing prostate tumor cells invade along nerves innervating the encapsulated human prostate gland in a process known as perineural invasion. The extracellular matrix laminin class of proteins line the neural route and tumor cells escaping from the gland express the laminin binding integrin alpha6beta1 as a prominent cell surface receptor. Integrin alpha6beta1 promotes aggressive disease and supports prostate tumor cell metastasis to bone. Laminins and their integrin receptors are necessary for the development and maintenance of the peripheral nervous system, indicating the potential role for integrin receptors in directing prostate tumor cell invasion on nerves during perineural invasion.

Molecular mechanisms of perineural invasion, a forgotten pathway of dissemination and metastasis

Invasion and metastasis are key components of cancer progression. Inflammatory mediators, including cytokines and chemokines, can facilitate tumor dissemination. A distinct and largely forgotten path is perineural invasion (PNI), defined as the presence of cancer cells in the perinerium space. PNI is frequently used by many human carcinomas, in particular by pancreas and prostate cancer, and is associated with tumor recurrence and pain in advanced patients. Neurotrophic factors have been identified as molecular determinants of PNI. A role for chemokines in this process has been proposed; the chemokine CX3CL1/Fractalkine attracts receptor positive pancreatic tumor cells to disseminate along peripheral nerves. Better understanding of the neurotropism of malignant cells and of the clinical significance of PNI would help the design of innovative strategies for the control of tumor dissemination and pain in cancer patients.

Consensus transcriptome signature of perineural invasion in pancreatic carcinoma

Perineural invasion, the growth of tumor cells along nerves, is a key feature of pancreatic cancer. The cardinal symptom of pancreatic cancer, abdominal pain often radiating to the back, as well as the high frequency of local tumor recurrence following resection are both attributed to the unique ability of pancreatic tumor cells to invade the neuronal system. The molecular mechanisms underlying the neuroaffinity of pancreatic tumors are not completely understood. In this study, we developed a novel method to monitor ex vivo perineural invasion into surgically resected rat vagal nerves by different human pancreatic tumor cell lines. Genome-wide transcriptional analyses were employed to identify the consensus set of genes differentially regulated in all highly nerve-invasive (nerve invasion passage 3) versus less invasive (nerve invasion passage 0) pancreatic tumor cells. The critical involvement of kinesin family member 14 (KIF14) and Rho-GDP dissociation inhibitor beta (ARHGDIbeta) in perineural invasion was confirmed on RNA and protein levels in human pancreatic tumor specimens. We found significant up-regulation of KIF14 and ARHGDIbeta mRNA levels in patients with pancreatic cancer, and both proteins were differentially expressed in tumor cells invading the perineural niche of pancreatic cancer patients as detected by immunohistochemistry. Moreover, functional knockdown of KIF14 and ARHGDIbeta using small interfering RNA resulted in altered basal and/or perineural invasion of pancreatic tumor cells. Our work provides novel insights into the molecular determinants of perineural invasion in pancreatic cancer. The established nerve invasion model and the consensus signature of perineural invasion could be instrumental in the identification of novel therapeutic targets of pancreatic cancer as exemplified by KIF14 and ARHGDIbeta.

Expression of nerve growth factor and tyrosine kinase receptor A and correlation with perineural invasion in pancreatic cancer

BACKGROUND AND AIM

Perineural invasion (PNI) is one of the most common routes of invasion in pancreatic cancer and the exact mechanism is still not clear. The aim of the present study was to investigate the effect of nerve growth factor (NGF) and tyrosine kinase receptor A (TrkA) on PNI and to clarify the possible mechanism of PNI in pancreatic cancer.

METHODS

Expressions of NGF/TrkA were examined in 51 human primary pancreatic cancer using immunohistochemistry (IHC) and reverse transcription polymerase chain reaction (RT-PCR). The molecular findings were correlated with PNI, clinicopathological parameters and expression of Ki-67.

RESULTS

Immunohistochemical analysis indicated that the presence and kind of PNI are prognostic parameters (P = 0.002,, P = 0.004). Tumors with high NGF expression exhibited more frequent presence of PNI (P = 0.033). NGF expression was significantly correlated with metastasis of lymph nodes and involvement of surgical margins (P = 0.006, 0.015). TrkA expression was significantly correlated with degree of PNI (P = 0.017). Negative correlations were found between expression of NGF/TrkA and Ki-67. As shown by RT-PCR, mRNA levels of NGF/TrkA with PNI were significantly higher than that without PNI.

CONCLUSIONS

In pancreatic cancer, overexpression of NGF may contribute to PNI by prompting the hyperplasia of nerves, restraining the apoptosis of tumor cells and specifically combining NGF and TrkA.

Stimulation of dorsal root ganglion neurons activity by pancreatic cancer cell lines

Stimulation of mice dorsal root ganglion neurons (DRGNs) activity by human pancreatic cancer (PanCa) cell line Mia PaCa-2 and its potential molecule mechanism has been investaged. DRGNs were cultured alone or along with the MIA PaCa-2. The effects of MIA PaCa-2 to DRGNs were determined by neurofilament (NF) immunocytochemical and Nissl staining. ELISA was used to detect the concentration of insulin-like growth factor-1 (IGF-1) in the culture supernatant. Cyton size, neurite outgrowth and neuronal activity in the experimental group were greater than in the control groups. However, the concentration of IGF-1 in the supernatants was not significantly different from those in the blank and non-cultured medium groups. In the presence of MIA PaCa-2 cell line, cyton size, neurite outgrowth and neuronal activity were enhanced, which may provide more routes for the invasion of cancer cells along nerves.

Results of pancreaticoduodenectomy in patients with periampullary adenocarcinoma: perineural growth more important prognostic factor than tumor localization

OBJECTIVE

To study the impact of perineural growth as a prognostic factor in periampullary adenocarcinoma (pancreatic head, ampulla of Vater, distal bile duct, and duodenal carcinoma).

SUMMARY BACKGROUND DATA

Pancreatic head carcinoma is considered to have the worst prognosis of the periampullary carcinomas. Several other prognostic factors for periampullary tumors have been identified, eg, lymph node status, free resection margins, tumor size and differentiation, and vascular invasion. The impact of perineural growth as a prognostic factor in relation to the site of origin of periampullary carcinomas is unknown.

METHODS

Data of 205 patients with periampullary carcinomas were retrieved from our prospective database. Pancreaticoduodenectomy was performed in 121 patients. Their clinicopathological data were reviewed and analyzed in a multivariate analysis.

RESULTS

Perineural growth was present in 49% of the cases (37 of the 51 patients with pancreatic head carcinoma; 7 of the 30 patients with ampulla of Vater carcinoma; 7 of the 19 with distal bile duct carcinoma; and 8 of the 21 with duodenal carcinoma). Overall 5-year survival was 32.6% with a median survival of 20.7 months. Median survival in tumors with perineural growth was 13.1 months compared with 36.0 months in tumors without perineural growth (P < 0.0001) Using multivariate analysis, the following unfavorable prognostic factors were identified: perineural growth (RR = 2.90, 95% CI 1.62-5.22), nonradical resection (RR = 2.28, 95% CI 1.19-4.36), positive lymph nodes (RR = 1.96, 95% CI 1.11-3.45), and angioinvasion (RR = 1.79, 95% CI 1.05-3.06). Portal or superior mesenteric vein reconstruction and tumor localization were not of statistical significance.

CONCLUSION

Perineural growth is a more important risk factor for survival than the primary site of periampullary carcinomas.

Neural invasion in pancreatic cancer: a mutual tropism between neurons and cancer cells

Neural invasion by pancreatic cancer cells (PCC) worsens the prognosis and frequently limits curative resection. We established a novel in-vitro model in which T3M4-PCCs were co-cultured with either isolated myenteric plexus cells (MP) or dorsal root ganglia (DRG) of newborn rats within a three-dimensional extracellular matrix gel. The close vicinity of MP or DRG to T3M4-PCCs induced early morphologic changes on T3M4-PCCs at the migration front prior to the migration process with elongated and neurite-targeting PCCs, compared to round and non-grouping at the non-migrating front. T3M4-PCCs built cancer-cell clusters around the DRG or MP, a process which was accelerated by increasing number of T3M4-PCCs or neurons. These findings indicate that neuro-cancer interactions start prior to PCC migration and induce evident changes in cancer and nerve biology. These findings can be reproduced within the introduced 3D in-vitro migration assay which allows investigation in the early pathogenesis of neural PCC invasion.

The effect of perineural invasion on overall survival in patients with gastric carcinoma

AIMS

The availability of different treatment options for gastric carcinoma has reopened the question of correct definition of high-risk categories, which may help in identifying patients with high risk for poor prognosis who would benefit more from adjuvant therapy after operation. Perineural invasion (PNI) seems to provide useful information for management. Therefore, we examined the effect of PNI on overall survival (OS) in patients with gastric carcinoma and the association between PNI and other clinical and pathological factors.

PATIENTS AND METHODS

A total of 1,632 patients with gastric carcinoma from 2000 to 2005 were analyzed retrospectively. Paraffin sections of surgical specimens from all patients who underwent gastric resection were stained with laminin. If carcinoma cells infiltrated into the perineurium or neural fascicles, PNI was assessed as positive. Survival analysis was done in 1,372 patients with T1-T4 tumors who underwent curative resection.

RESULT

PNI was positive in 518 of the 1,632 patients (31.7%). The size of tumors, T stage, differentiation of tumor, and clinical stage were significantly related to PNI positivity. The proportion of large tumors was significantly higher in PNI-positive patients than in PNI-negative patients (P < 0.01). As the depth of gastric mural invasion or clinical stage increased, the positive rate of PNI also increased. The OS of the PNI-positive patients was significantly shorter than that of the PNI-negative patients in the univariate analysis (P < 0.01). At multivariate Cox proportional hazards model of OS analysis, the positivity of PNI appeared to be an independent prognostic factor for OS (hazards ratio [HR] = 3.23, 95%CI = 2.6-8.11, P < 0.01), which was also influenced by tumor differentiation, T stage, and clinical stage (P < 0.01).

CONCLUSION

Our results suggested that the incidence of PNI was high in gastric carcinoma and that it corresponded to the progression of disease. It could provide additional information for identifying patients who are at high risk for poor prognosis. PNI can be a candidate for a new kind of prognostic parameters.

Cell adhesion molecule 1 is a novel pancreatic-islet cell adhesion molecule that mediates nerve-islet cell interactions

BACKGROUND & AIMS

Cell adhesion molecule 1 (CADM1), mediates nerve-mast cell attachment and communication through homophilic binding. An immunohistochemical screen showed that CADM1 is expressed in pancreatic islets. Here, we determined the cell types expressing CADM1 and examined its role in nerve-islet cell interactions.

METHODS

Immunohistochemistry and double-staining immunofluorescence were performed on murine and human pancreases and on islet cell tumors (ICTs). alphaTC6 cells, a murine alpha cell line, were cultured on neurite networks of superior cervical ganglia. Neurite-alphaTC6 cell attachment and communication were examined after nerves were activated specifically by scorpion venom.

RESULTS

CADM1 was expressed on the plasma membrane in all 4 major types of islet cells, alpha, beta, D, and pancreatic polypeptide in human beings, but primarily in alpha cells in mice. In cocultures, alphaTC6 cell to neurite attachment was inhibited dose-dependently by an anti-CADM1 function-blocking antibody. In response to scorpion venom-evoked nerve activation, 36% of the alphaTC6 cells mobilized Ca(2+), and introduction of a CADM1-targeting small interfering RNA reduced the fraction of responding cells to 7%. In 21 human ICTs, CADM1 was present in the plasma membrane of 7, and the others were negative for CADM1. Six of the CADM1-expressing tumors were functional hormonally, whereas all but 2 of the CADM1-negative tumors were nonfunctional (P = .0032).

CONCLUSIONS

CADM1 is a novel islet cell adhesion molecule mediating nerve-islet cell interactions. The strong correlation between CADM1 expression and hormonally functional phenotypes suggests that CADM1 is involved in hormone secretion from ICTs.