Alteration of integrin expression by glial cell line-derived neurotrophic factor (GDNF) in human pancreatic cancer cells

Predictive Value of MUC5AC Signature in Pancreatic Ductal Adenocarcinoma: A Hypothesis Based on Preclinical Evidence

Mucin 5AC (MUC5AC) glycoprotein plays a crucial role in carcinogenesis and drug sensitivity in pancreatic ductal adenocarcinoma (PDAC), both individually and in combination with other mucins. Its function and localization are glycoform-specific. The immature isoform (detected by the CLH2 monoclonal antibody, or mab) is usually in the perinuclear (cytoplasmic) region, while the mature (45 M1, 2-11, Nd2) variants are in apical and extracellular regions. There is preclinical evidence suggesting that mature MUC5AC has prognostic and predictive (response to treatment) value. However, these findings were not validated in clinical studies. We propose a MUC5AC signature with three components of MUC5AC-localization, variant composition, and intensity-suggesting a reliable marker in combination of variants than with individual MUC5AC variants alone. We also postulate a theory to explain the occurrence of different MUC5AC variants in abnormal pancreatic lesions (benign, precancerous, and cancerous). We also analyzed the effect of mature MUC5AC on sensitivity to drugs often used in PDAC management, such as gemcitabine, 5-fluorouracil, oxaliplatin, irinotecan, cisplatin, and paclitaxel. We found preliminary evidence of its predictive value, but there is a need for large-scale studies to validate them.

Important Cells and Factors from Tumor Microenvironment Participated in Perineural Invasion

Perineural invasion (PNI) as the fourth way for solid tumors metastasis and invasion has attracted a lot of attention, recent research reported a new point that PNI starts to include axon growth and possible nerve "invasion" to tumors as the component. More and more tumor-nerve crosstalk has been explored to explain the internal mechanism for tumor microenvironment (TME) of some types of tumors tends to observe nerve infiltration. As is well known, the interaction of tumor cells, peripheral blood vessels, extracellular matrix, other non-malignant cells, and signal molecules in TME plays a key role in the occurrence, development, and metastasis of cancer, as to the occurrence and development of PNI. We aim to summarize the current theories on the molecular mediators and pathogenesis of PNI, add the latest scientific research progress, and explore the use of single-cell spatial transcriptomics in this invasion way. A better understanding of PNI may help to understand tumor metastasis and recurrence and will be beneficial for improving staging strategies, new treatment methods, and even paradigm shifts in our treatment of patients.

GDNF Promotes Astrocyte Abnormal Proliferation and Migration Through the GFRα1/RET/MAPK/pCREB/LOXL2 Signaling Axis

Glial cell-line derived neurotrophic factor (GDNF) is a powerful astroglioma (AG) proliferation and migration factor that is highly expressed in AG cells derived from astrocytes. However, it is still unclear whether high levels of GDNF promote AG occurrence or if they are secondary to AG formation. We previously reported that high concentrations of GDNF (200 and 500 ng/mL) can inhibit DNA damage-induced rat primary astrocytes (RA) apoptosis, suggesting that high concentrations of GDNF may be involved in the malignant transformation of astrocytes to AG cells. Here we show that 200 ng/mL GDNF significantly increased the proliferation and migration ability of RA cells and human primary astrocytes (HA). This treatment also induced RA cells to highly express Pgf, Itgb2, Ibsp, Loxl2, Lif, Cxcl10, Serpine1, and other genes that enhance AG proliferation and migration. LOXL2 is an important AG occurrence and development promotion factor and was highly expressed in AG tissues and cells. High concentrations of GDNF promote LOXL2 expression and secretion in RA cells through GDNF family receptor alpha-1(GFRα1)/rearranged during transfection proto-oncogene (RET)/mitogen-activated protein kinase (MAPK)/phosphorylated cyclic AMP response element binding protein (pCREB) signaling. GDNF-induced LOXL2 significantly promotes RA and HA cell proliferation and migration, and increases the expression of Ccl2, Gbp5, MMP11, TNN, and other genes that regulate the extracellular microenvironment in RA cells. Our results demonstrate that high concentrations of GDNF activate LOXL2 expression and secretion via the GFRα1/RET/MAPK/pCREB signal axis, which leads to remodeling of the astrocyte extracellular microenvironment through molecules such as Ccl2, Gbp5, MMP11, TNN. This ultimately results in abnormal astrocyte proliferation and migration. Collectively, these findings suggest that high GDNF concentrations may promote the malignant transformation of astrocytes to AG cells.

Cancer-Associated Neurogenesis and Nerve-Cancer Cross-talk

In this review, we highlight recent discoveries regarding mechanisms contributing to nerve-cancer cross-talk and the effects of nerve-cancer cross-talk on tumor progression and dissemination. High intratumoral nerve density correlates with poor prognosis and high recurrence across multiple solid tumor types. Recent research has shown that cancer cells express neurotrophic markers such as nerve growth factor, brain-derived neurotrophic factor, and glial cell-derived neurotrophic factor and release axon-guidance molecules such as ephrin B1 to promote axonogenesis. Tumor cells recruit new neural progenitors to the tumor milieu and facilitate their maturation into adrenergic infiltrating nerves. Tumors also rewire established nerves to adrenergic phenotypes via exosome-induced neural reprogramming by p53-deficient tumors. In turn, infiltrating sympathetic nerves facilitate cancer progression. Intratumoral adrenergic nerves release noradrenaline to stimulate angiogenesis via VEGF signaling and enhance the rate of tumor growth. Intratumoral parasympathetic nerves may have a dichotomous role in cancer progression and may induce Wnt-β-catenin signals that expand cancer stem cells. Importantly, infiltrating nerves not only influence the tumor cells themselves but also impact other cells of the tumor stroma. This leads to enhanced sympathetic signaling and glucocorticoid production, which influences neutrophil and macrophage differentiation, lymphocyte phenotype, and potentially lymphocyte function. Although much remains unexplored within this field, fundamental discoveries underscore the importance of nerve-cancer cross-talk to tumor progression and may provide the foundation for developing effective targets for the inhibition of tumor-induced neurogenesis and tumor progression.

Systemic Depletion of Nerve Growth Factor Inhibits Disease Progression in a Genetically Engineered Model of Pancreatic Ductal Adenocarcinoma

OBJECTIVES

In patients with pancreatic ductal adenocarcinoma (PDAC), increased expression of proinflammatory neurotrophic growth factors (eg, nerve growth factor [NGF]) correlates with a poorer prognosis, perineural invasion, and, with regard to NGF, pain severity. We hypothesized that NGF sequestration would reduce inflammation and disease in the KPC mouse model of PDAC.

METHODS

Following biweekly injections of NGF antibody or control immunoglobulin G, beginning at 4 or 8 weeks of age, inflammation and disease stage were assessed using histological, protein expression, and quantitative polymerase chain reaction analyses.

RESULTS

In the 8-week anti-NGF group, indicators of neurogenic inflammation in the dorsal root ganglia (substance P and calcitonin gene-related peptide) and spinal cord (glial fibrillary acidic protein) were significantly reduced. In the 4-week anti-NGF group, TRPA1 mRNA in dorsal root ganglia and spinal phosphorylated ERK protein were elevated, but glial fibrillary acidic protein expression was unaffected. In the 8-week anti-NGF group, there was a 40% reduction in the proportion of mice with microscopic perineural invasion, and no macrometastases were observed.

CONCLUSIONS

Anti-NGF treatment beginning at 4 weeks may increase inflammation and negatively impact disease. Treatment starting at 8 weeks (after disease onset), however, reduces neural inflammation, neural invasion, and metastasis. These data indicate that NGF impacts PDAC progression and metastasis in a temporally dependent manner.

The GDNF Family: A Role in Cancer?

The glial cell line-derived neurotrophic factor (GDNF) family of ligands (GFLs) comprising of GDNF, neurturin, artemin, and persephin plays an important role in the development and maintenance of the central and peripheral nervous system, renal morphogenesis, and spermatogenesis. Here we review our current understanding of GFL biology, and supported by recent progress in the area, we examine their emerging role in endocrine-related and other non-hormone-dependent solid neoplasms. The ability of GFLs to elicit actions that resemble those perturbed in an oncogenic phenotype, alongside mounting evidence of GFL involvement in tumor progression, presents novel opportunities for therapeutic intervention.

Involvement of N-cadherin in the protective effect of glial cell line-derived neurotrophic factor on dopaminergic neuron damage

The aim of this study was to further confirm that glial cell line-derived neurotrophic factor (GDNF) exerts a neuro-protective effect on dopaminergic neurons (DAs) and to investigate the protective mechanism. Cadherins are calcium-dependent adhesion proteins, and N-cadherins are found in neurons. Our study attempted to ascertain whether GDNF activates the PI3K/Akt signaling pathway through the mediation of N-cadherin to confer a protective effect on DAs. Flow cytometry and Hoechst 33258 staining results indicated that the apoptosis rate of damaged neurocytes increased following interference of N-cadherin expression. Immunoblotting results demonstrated that the amount of phosphorylated Akt (p-Akt) in the cytoplasm decreased, while the total Akt quantity remained unchanged following interference of N-cadherin expression. The immunohistochemical staining results demonstrated that the levels of total N-cadherin, phosphorylated N-cadherin (Tyr860) and p-Akt decreased; however, the amount of total Akt remained unchanged. In addition, we also demonstrated that Tyr860 and p-Akt levels were reduced in a GDNF dose-dependent manner with the phosphorylation level peaking at GDNF dose of 50 ng/ml (in vitro) and 50 ng/4 µl (in vivo), and also in a time-dependent manner with the phosphorylation level peaking at 15 min (in vitro) and 30 min (in vivo). Statistical analysis also showed that changes in the phosphorylation levels of Tyr860 and p-Akt demonstrated a positive correlation. Collectively, GDNF activates the PI3K/Akt pathway via N-cadherin to protect DAs.

Specificity of peripheral nerve regeneration: interactions at the axon level

Peripheral nerves injuries result in paralysis, anesthesia and lack of autonomic control of the affected body areas. After injury, axons distal to the lesion are disconnected from the neuronal body and degenerate, leading to denervation of the peripheral organs. Wallerian degeneration creates a microenvironment distal to the injury site that supports axonal regrowth, while the neuron body changes in phenotype to promote axonal regeneration. The significance of axonal regeneration is to replace the degenerated distal nerve segment, and achieve reinnervation of target organs and restitution of their functions. However, axonal regeneration does not always allows for adequate functional recovery, so that after a peripheral nerve injury, patients do not recover normal motor control and fine sensibility. The lack of specificity of nerve regeneration, in terms of motor and sensory axons regrowth, pathfinding and target reinnervation, is one the main shortcomings for recovery. Key factors for successful axonal regeneration include the intrinsic changes that neurons suffer to switch their transmitter state to a pro-regenerative state and the environment that the axons find distal to the lesion site. The molecular mechanisms implicated in axonal regeneration and pathfinding after injury are complex, and take into account the cross-talk between axons and glial cells, neurotrophic factors, extracellular matrix molecules and their receptors. The aim of this review is to look at those interactions, trying to understand if some of these molecular factors are specific for motor and sensory neuron growth, and provide the basic knowledge for potential strategies to enhance and guide axonal regeneration and reinnervation of adequate target organs.

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.

Role of glial cell line-derived neurotrophic factor in perineural invasion of pancreatic cancer

Perineural invasion (PNI) is the initial infiltration of tumor cells into the retroperitoneal nerve plexus and along the nerves. It precludes curative resection, is thought to be the major cause of local recurrence following resection, and is a special metastatic route in pancreatic cancer. Glial cell line-derived neurotrophic factor (GDNF) was recently recognized as a key player in the PNI process. This review covers the most recently published studies on the role of GDNF in pancreatic cancer. We introduce the players in PNI, summarize the distribution of GDNF and its receptors in pancreatic cancer, and discuss the effects and underlying mechanism of GDNF in the PNI process. Finally, we also review some potential inhibitors for GDNF-targeted therapy.

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 growth factor and artemin are paracrine mediators of pancreatic neuropathy in pancreatic adenocarcinoma

OBJECTIVE

To further characterize the neurotrophic attributes of pancreatic cancer (PCa).

SUMMARY BACKGROUND DATA

PCa is characterized by neuropathic alterations which are resulting in pancreatic pain. To further characterize pancreatic neuropathy, we aimed: to analyze whether neuropathic alterations in PCa are only limited to the tumor-core or whether they are similarly encountered in neural structures in the noncancerous pancreas, to demonstrate whether PCa features neurotrophic attributes and finally to identify responsible neurotrophic molecules.

METHODS

Nerve density and area were quantified in normal pancreas (NP, n=45), histologically "normal" pancreas next to pancreatic cancer (NNPCa, n=61) and PCa (n=97). Growth-associated protein-43, nerve growth factor (NGF), and Artemin expressions were assessed by Immunohistochemistry, Western-Blot, and quantitative real time polymerase chain reaction-analyses. Isolated myenteric plexus of newborn rats were exposed to NP, NNPCa, and PCa tissue extracts and supernatants of Panc1 and T3M4 cancer cells with or without Artemin and NGF depletion, followed by neurite density analysis.

RESULTS

Dense neural networks and enlarged nerves were not only detected in PCa but were also present in NNPCa. Growth-associated protein-43, NGF, and Artemin expressions were absent/weak in NP, but increased in both NNPCa and PCa and were closely associated with intrapancreatic neuropathy. PCa and NNPCa tissue extracts and Panc1/T3M4 supernatants noticeably increased neurite density in myenteric plexus-cultures, which were attenuated by depletion of NGF and Artemin.

CONCLUSIONS

The neurotrophic effects of PCa extend into the peritumoral "normal" pancreatic areas without neuro-cancer interactions. The neurotrophic characteristics of PCa can be mimicked by in vitro analyses and reveal NGF and Artemin as potential key players in the generation of pancreatic neuropathy in PCa.

Phenotype and genotype of pancreatic cancer cell lines

The dismal prognosis of pancreatic adenocarcinoma is due in part to a lack of molecular information regarding disease development. Established cell lines remain a useful tool for investigating these molecular events. Here we present a review of available information on commonly used pancreatic adenocarcinoma cell lines as a resource to help investigators select the cell lines most appropriate for their particular research needs. Information on clinical history; in vitro and in vivo growth characteristics; phenotypic characteristics, such as adhesion, invasion, migration, and tumorigenesis; and genotypic status of commonly altered genes (KRAS, p53, p16, and SMAD4) was evaluated. Identification of both consensus and discrepant information in the literature suggests careful evaluation before selection of cell lines and attention be given to cell line authentication.

Paracrine regulation of pancreatic cancer cell invasion by peripheral nerves

BACKGROUND

The ability of cancer to infiltrate along nerves is a common clinical observation in pancreas, head and neck, prostate, breast, and gastrointestinal carcinomas. For these tumors, nerves may provide a conduit for local cancer progression into the central nervous system. Although neural invasion is associated with poor outcome, the mechanism that triggers it is unknown.

METHODS

We used an in vitro Matrigel dorsal root ganglion and pancreatic cancer cell coculture model to assess the dynamic interactions between nerves and cancer cell migration and the role of glial cell-derived neurotrophic factor (GDNF). An in vivo murine sciatic nerve model was used to study how nerve invasion affects sciatic nerve function.

RESULTS

Nerves induced a polarized neurotrophic migration of cancer cells (PNMCs) along their axons, which was more efficient than in the absence of nerves (migration distance: mean = 187.1 microm, 95% confidence interval [CI] = 148 to 226 microm vs 14.4 microm, 95% CI = 9.58 to 19.22 microm, difference = 143 microm; P < .001; n = 20). PNMC was induced by secretion of GDNF, via phosphorylation of the RET-Ras-mitogen-activated protein kinase pathway. Nerves from mice deficient in GDNF had reduced ability to attract cancer cells (nerve invasion index: wild type vs gdnf+/-, mean = 0.76, 95% CI = 0.75 to 0.77 vs 0.43, 95% CI = 0.42 to 0.44; P < .001; n = 60-66). Tumor specimens excised from patients with neuroinvasive pancreatic carcinoma had higher expression of the GDNF receptors RET and GRFalpha1 as compared with normal tissue. Finally, systemic therapy with pyrazolopyrimidine-1, a tyrosine kinase inhibitor targeting the RET pathway, suppressed nerve invasion toward the spinal cord and prevented paralysis in mice.

CONCLUSION

These data provide evidence for paracrine regulation of pancreatic cancer invasion by nerves, which may have important implications for potential therapy directed against nerve invasion by cancer.

Ape1/Ref-1 induces glial cell-derived neurotropic factor (GDNF) responsiveness by upregulating GDNF receptor alpha1 expression

Apurinic/apyrimidinic endonuclease 1 (Ape1/Ref-1) dysregulation has been identified in several human tumors and in patients with a variety of neurodegenerative diseases. However, the function of Ape1/Ref-1 is unclear. We show here that Ape1/Ref-1 increases the expression of glial cell-derived neurotropic factor (GDNF) receptor alpha1 (GFRalpha1), a key receptor for GDNF. Expression of Ape1/Ref-1 led to an increase in the GDNF responsiveness in human fibroblast. Ape1/Ref-1 induced GFRalpha1 transcription through enhanced binding of NF-kappaB complexes to the GFRalpha1 promoter. GFRalpha1 levels correlate proportionally with Ape1/Ref-1 in cancer cells. The knockdown of endogenous Ape1/Ref-1 in pancreatic cancer cells markedly suppressed GFRalpha1 expression and invasion in response to GNDF, while overexpression of GFRalpha1 restored invasion. In neuronal cells, the Ape1/Ref-1-mediated increase in GDNF responsiveness not only stimulated neurite outgrowth but also protected the cells from beta-amyloid peptide and oxidative stress. Our results show that Ape1/Ref-1 is a novel physiological regulator of GDNF responsiveness, and they also suggest that Ape1/Ref-1-induced GFRalpha1 expression may play important roles in pancreatic cancer progression and neuronal cell survival.

Pancreatic pain

Abdominal pain is an important clinical symptom in pancreatic diseases. There is increasing evidence that pain in chronic pancreatitis and pancreatic cancer is triggered by pancreatic neuropathy. Damage to intrapancreatic nerves seems to support the maintenance and exacerbation of neuropathic pain. In chronic pancreatitis, intrapancreatic nerves are invaded by immune cells. This observation led to the hypothesis that neuro-immune interactions play a role in the pathogenesis of chronic pancreatitis and the accompanying abdominal pain syndrome. Similarly, pancreatic cancer cells infiltrate the perineurium of local nerves, which may in part explain the severe pain experienced by the patients. Furthermore, perineural invasion extending into extrapancreatic nerves may preclude curative resection and thus often leads to local recurrence. In recent years, the involvement of a variety of neurotrophins and neuropeptides in the pathogenesis of pancreatic pain was discovered. This review summarises recent data on the mechanisms of neuropathy and pain generation in pancreatic disorders.

Vascular endothelial growth factor-C secreted by pancreatic cancer cell line promotes lymphatic endothelial cell migration in an in vitro model of tumor lymphangiogenesis

OBJECTIVES

To investigate mechanisms underlying lymphatic node metastasis in pancreatic cancer, we examined roles of vascular endothelial growth factor-C (VEGF-C) in tumor lymphangiogenesis.

METHODS

We measured VEGF-C secretion by pancreatic cancer cell lines using enzyme-linked immunosorbent assay and examined effects of different cell lines on lymphatic endothelial cells (LECs) in vitro.

RESULTS

We identified VEGF-C high-secretion (MIA PaCa-2) and low-secretion cell lines (BxPC-3). The trend of enhancement of LEC proliferation by recombinant human VEGF-C (rVEGF-C) was not statistically significant. Numbers of migrating cells were increased by rVEGF-C treatment in a dose-dependent manner. The MIA PaCa-2 cell culture supernatant caused greater LEC migration than the BxPC-3 supernatant. The VEGF-C effects were significantly inhibited by rVEGF receptor 3 (rVEGF R3)/Fc chimera. In LEC/fibroblast coculture on collagen gel, LEC capillary formation was significantly enhanced by coculture with MIA PaCa-2 cells compared with BxPC-3 cells. Enhanced capillary formation with MIA PaCa-2 cells was inhibited by rVEGF R3/Fc chimera, implying VEGF-C involvement in progression of LEC sprouting in a tumor microenvironment.

CONCLUSIONS

Because VEGF-C secreted by pancreatic cancer cells plays an important role in LEC migration in pancreatic cancer lymphangiogenesis, it is possible that rVEGF R3/Fc chimera might have a role in controlling lymph node metastasis.

Roles of integrins in pancreatic adenocarcinoma

Integrins, serving as transmembrane proteins, play major roles in cell-extracellular matrix adhesions, and they can introduce extracellular signals into the cells, alter cellular morphology and influence cell motility as well as contribute to tumor invasion and metastasis. One of the major causes of low resection rates and extremely poor survival rates is its extraordinary local tumor progression and early systemic dissemination. Being a kind of adhesion molecules associating cells with extracellular matrix, integrins play a variety of roles in the process of invasion and metastasis in pancreatic adenocarcinoma.

The neurotrophic factor artemin promotes pancreatic cancer invasion

OBJECTIVE

To analyze the role of Artemin in pancreatic ductal adenocarcinoma (PDAC) in terms of expression, influence on cancer cell behavior, and pain correlation.

SUMMARY BACKGROUND DATA

PDAC is characterized by prominent local nerve alterations and perineural invasion, which frequently affects the extrapancreatic nerve plexus, causing severe pain and precluding curative resection. Artemin, a neurotrophic protein controlling growth, regeneration, and survival of neurons was analyzed to highlight the neuro-cancer interactions in PDAC.

METHODS

Artemin and its receptors (GFRalpha3/RET) were studied in PDAC tissues and normal pancreas by Western blot analysis and immunohistochemistry. RNA expression was analyzed in pancreatic tissues (normal, cancer) and pancreatic cancer cell lines by QRT-PCR. To evaluate whether Artemin influences cancer cell proliferation and invasion, MTT-growth and Matrigel-invasion assays were used. In addition, the tissue expression of Artemin was correlated with pain in PDAC.

RESULTS

Artemin and GFRalpha3/RET were both detected at enhanced levels in PDAC compared with normal pancreas, localizing predominantly in hypertrophic nerves and arterial walls, as well as in cancer cells of primary and metastatic lesions. The levels of Artemin and GFRalpha3 did not correlate with pain in PDAC patients. However, Artemin promoted pancreatic cancer cell invasion up to 5-fold, without affecting cancer cell proliferation.

CONCLUSION

Artemin expression was not associated with pain in PDAC. However by increasing cancer cell invasion, Artemin seems to influence neural invasion and thereby contribute to cancer cell spreading along pancreatic nerves.

Cholecystokinin-2 receptor modulates cell adhesion through beta 1-integrin in human pancreatic cancer cells

Several lines of evidence suggest that gastrin and the CCK-2 receptor (CCK2R) could contribute to pancreatic carcinogenesis by modulating processes such as proliferation, cell adhesion or migration. In the current study, we used a 'cancer gene array' and identified beta1-integrin subunit as a new gastrin-regulated gene in human pancreatic cancer cells. We also demonstrated that Src family kinases and the phosphatidylinositol-3-kinase (PI-3-kinase) pathway play a crucial role in the expression of beta1-integrin induced by gastrin. Our results also showed that gastrin modulates cell-substrate adhesion via beta1-integrin. Indeed, using blocking anti-beta1-integrin monoclonal antibodies, we completely reversed the increase in cell-substrate adhesion induced by gastrin. In addition, we observed that in response to gastrin, beta1-integrin is tyrosine phosphorylated by Src family kinases and associates with paxillin, a scaffold protein involved in focal adhesion and integrin signalling. This mechanism might be involved in gastrin-induced cell adhesion. Moreover, we showed in vivo that targeted CCK2R expression in the pancreas of Elas-CCK2 mice leads to the overexpression of beta1-integrin. This process may contribute to pancreatic tumour development observed in these transgenic animals.

Biomarker discovery from pancreatic cancer secretome using a differential proteomic approach

Quantitative proteomics can be used as a screening tool for identification of differentially expressed proteins as potential biomarkers for cancers. Candidate biomarkers from such studies can subsequently be tested using other techniques for use in early detection of cancers. Here we demonstrate the use of stable isotope labeling with amino acids in cell culture (SILAC) method to compare the secreted proteins (secretome) from pancreatic cancer-derived cells with that from non-neoplastic pancreatic ductal cells. We identified 145 differentially secreted proteins (>1.5-fold change), several of which were previously reported as either up-regulated (e.g. cathepsin D, macrophage colony stimulation factor, and fibronectin receptor) or down-regulated (e.g. profilin 1 and IGFBP-7) proteins in pancreatic cancer, confirming the validity of our approach. In addition, we identified several proteins that have not been correlated previously with pancreatic cancer including perlecan (HSPG2), CD9 antigen, fibronectin receptor (integrin beta1), and a novel cytokine designated as predicted osteoblast protein (FAM3C). The differential expression of a subset of these novel proteins was validated by Western blot analysis. In addition, overexpression of several proteins not described previously to be elevated in human pancreatic cancer (CD9, perlecan, SDF4, apoE, and fibronectin receptor) was confirmed by immunohistochemical labeling using pancreatic cancer tissue microarrays suggesting that these could be further pursued as potential biomarkers. Lastly the protein expression data from SILAC were compared with mRNA expression data obtained using gene expression microarrays for the two cell lines (Panc1 and human pancreatic duct epithelial), and a correlation coefficient (r) of 0.28 was obtained, confirming previously reported poor associations between RNA and protein expression studies.

Glial cell line-derived neurotrophic factor enhances nuclear factor-kappaB activity and invasive potential in human pancreatic cancer cells

OBJECTIVES

The invasive potential is increased by glial cell line-derived neurotrophic factor (GDNF) in human pancreatic cancer cell lines. We researched whether the signaling pathway activated by GDNF correlates with the nuclear factor-kappaB (NF-kappaB) in human pancreatic cancer cell lines and whether the inhibition of NF-kappaB activity is associated with suppression of invasive potential.

METHODS

Proliferation of human pancreatic cancer cell lines (BxPC-3 and MIA PaCa-2) was measured by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assays (MTT assay). NF-kappaB activity was examined by dual luciferase assay and electrophoretic mobility shift assay. In addition, to investigate the invasive potential, an in vitro invasion assay was performed.

RESULTS

Proliferation of both cell lines was decreased by a proteasome inhibitor, MG132, in a dose-dependent manner, but proliferation of control and IkappaBalphaM vector-transfected BxPC-3 cells was similar. The invasion cell number and the NF-kappaB activity were increased by GDNF stimulation. However, in the presence of MG132 or IkappaBalphaM, which blocks the nuclear localization of NF-kappaB, both were significantly suppressed. Furthermore, reduced activity of both remained unchanged by GDNF stimulation.

CONCLUSION

These results indicate that GDNF promotes NF-kappaB activation and that the latter is involved in the invasive potential of human pancreatic cancer cells.