The chemokine receptor CX3CR1 is involved in the neural tropism and malignant behavior of pancreatic ductal adenocarcinoma.

Tumor perineural dissemination is a hallmark of human pancreatic ductal adenocarcinoma (PDAC) and represents a major source of local tumor recurrence after surgery. In this study, we provide in vitro and in vivo evidence that the chemokine receptor CX3CR1 may be involved in the neurotropism of PDAC cells to local peripheral nerves. Neoplastic cells from PDAC cell lines and surgical specimens express the chemokine receptor CX3CR1, absent in normal pancreatic ducts. Its unique ligand, the transmembrane chemokine CX3CL1, is expressed by neurons and nerve fibers. CX3CR1 + PDAC cell lines migrated in response to human recombinant CX3CL1 and specifically adhered to CX3CL1-expressing cells of neural origin via mechanisms involving activation of G proteins, beta1 integrins, and focal adhesion kinase. In vivo experiments with transplanted PDAC showed that only CX3CR1-transfected tumor cells infiltrated the local peripheral nerves. Immunohistochemistry of CX3CR1 in PDAC specimens revealed that 90% of the samples were positive with a heterogeneous pattern of expression. High receptor score was significantly associated with more prominent tumor perineural infiltration evaluated histologically (P = 0.026). Regression analyses (univariate and multivariate) showed that high CX3CR1 expression and perineural invasion were strongly associated with local and earlier tumor recurrence (P = 0.007). Collectively, this study shows that the CX3CR1 receptor may be involved in PDAC tumor neurotropism and is a relevant and independent risk factor to predict an early local tumor relapse in resected patients. Thus, the CX3CR1-CX3CL1 axis could represent a valuable therapeutic target to prevent tumor perineural dissemination in pancreatic cancer.

Monoclonal antibody 76F distinguishes IA-2 from IA-2beta and overlaps an autoantibody epitope.

IA-2 and IA-2beta are highly related proteins that are autoantigens in type 1 diabetes, and provide a model for developing reagents and assays that distinguish similar proteins with unique autoantibody epitopes. Monoclonal antibodies (mAb) to IA-2 and IA-2beta were prepared and tested for their ability to bind to the related proteins and their ability to compete for specific autoantibody epitope binding by sera from patients with type 1 diabetes. Monoclonal antibodies that specifically bound IA-2 (76F) or bound both IA-2 and IA-2beta (A9) were isolated and characterized. 76F mAb recognized IA-2 of human, rat and mouse origin in native and denatured forms and had an epitope specificity for residues 626-630 (FEYQD) which are found in the juxtamembrane (JM) region of human and mouse IA-2, but not IA-2beta. This region overlaps with the autoantibody epitope JM2. Binding to the 76F monoclonal antibody was specifically inhibited by sera with antibodies to the JM2 epitope but not with antibodies to the adjacent JM1 epitope, indicating that unique epitopes can be distinguished by this approach. 76F mAb has the unique property to distinguish between the two closely related autoantigens IA-2 and IA-2beta by targeting an IA-2 specific epitope of the juxtamembrane region. The findings define an approach to develop assays for specific antibody epitope measurements which may be relevant for disease prognosis and monitoring intervention therapies.