In our previous investigations, mitogen-activated protein kinase kinase 2 (MEK2)/extracellular signal-regulated kinase 2 (ERK2) signaling pathway was found to be correlated with the cell dissociation induced by dissociation factor (DF) in pancreatic cancer cells. In this study, the expressions of epidermal growth factor receptor (EGFR), phosphorylated EGFR (p-EGFR), and its downstream kinases MEK1/2 and ERK1/2, were analyzed to clarify the regulatory mechanism of cell dissociation in pancreatic cancer cells. Two hamster (PC-1.0 and PC-1) and two human (AsPC-1 and Capan-2) pancreatic cancer cell lines were used. Immunocytochemical study was performed using anti-EGFR, p-EGFR, phosphorylated MEK1/2 (p-MEK1/2), and phosphorylated ERK1/2 (p-ERK1/2) antibodies. DF-treatment markedly induced the expressions of EGFR, p-EGFR, p-MEK1/2, p-ERK1/2, as well as the dissociation of cell colonies in PC-1 and Capan-2 cells. In contrast, AG1478 (an EGFR inhibitor) treatment significantly induced the cell aggregation in PC-1.0 and AsPC-1 cells which usually grew as single cells, but strongly suppressed the expressions of EGFR, p-EGFR, p-MEK1/2, and p-ERK1/2. These observations demonstrate that activation of EGFR is closely involved in cell dissociation in pancreatic cancer through activating MEK/ERK signaling pathway.
[Show abstract][Hide abstract] ABSTRACT: Epidermal Growth Factor Receptor (EGFR or HER1) is considered a tumor associated antigen. HER1 is overexpressed in many human epithelial tumors and involved in crucial cellular functions for tumor development. For this reason HER1 is considered a good target for cancer immunotherapy and some passive agents are being evaluated in clinical trials. However, HER1-based active immunotherapy has not been clinically explored. To develop an active immunotherapy approach based on HER1 for the treatment of HER1+ cancer patients, we cloned and expressed in mammalian cells the HER1 extracellular domain protein (HER1-ECD), which was specifically recognized by an anti- EGFR monoclonal antibody. HER1-ECD was purified by affinity chromatography and adjuvated in Very Small Size Proteoliposomes (VSSP) or Complete Freund adjuvant to immunize C57BL/6 mice. Immunization elicited specific humoral and cellular immune response. The polyclonal antibodies induced by immunization recognized the full length HER1 on the surface of a lung tumor cell line. These results suggest that HER1-ECD could be an appropriated antigen to induce specific immune response in patients with HER1+ tumors.
[Show abstract][Hide abstract] ABSTRACT: To clarify the involvement of matrix metalloproteinase-7 (MMP-7) in cell dissociation and the subsequent invasion of pancreatic cancer cells.
Western blotting, in vitro invasion assay, immunocytochemistry, and immunohistochemistry were performed in pancreatic cancer cell lines or pancreatic cancer tissue.
The active form of the MMP-7 protein was expressed exclusively in the conditioned medium of dissociated (PC-1.0 and AsPC-1) pancreatic cancer cells, whereas proMMP-7 protein was only detected in the conditioned medium of non-dissociated (PC-1 and Capan-2) cells. Both intracellular and conditioned medium localised MMP-7 was greatly reduced by treatment with the epidermal growth factor receptor (EGFR) inhibitor AG1478 and the mitogen activated protein kinase kinase (MEK) inhibitor U0126 in pancreatic cancer cells. MMP-7 treatment significantly induced the disruption of tight junction (TJ) structures and subsequent cell dissociation, and activation of the EGFR mediated MEK- ERK (extracellular signal regulated protein kinase) signalling pathway in the non-dissociated pancreatic cancer cells. Moreover, the strong in vitro invasiveness of dissociated cells was inhibited by AG1478 and U0126 treatment, whereas the weak invasiveness of non-dissociated cells was apparently induced by MMP-7 treatment. In addition, MMP-7 expression was stronger at the invasive front than at the centre of human pancreatic tumours.
MMP-7 is involved in cell dissociation and the subsequent invasion of pancreatic cancer cells. It induces the disruption of TJ structures and forms a positive feedback loop with activation of the EGFR mediated MEK-ERK signalling pathway.
[Show abstract][Hide abstract] ABSTRACT: Long-term survival of surgically resectable pancreatic cancer patients is uncommon. The epidermal growth factor receptor (EGFR) and the phosphoinositol-3-kinase pathways are often activated in pancreatic cancer, and an understanding of their role in resected cases may help refine adjuvant therapy.
We investigated the expression of EGFR, Erk, Akt, and their phosphoforms (p-) in pancreatectomy specimens and correlated these with survival. Thirty-nine consecutive surgically resected pancreatic adenocarcinoma cases were included. Immunohistochemical staining of paraffin-embedded blocks was performed by using monoclonal antibodies against EGFR, Erk, p-Erk, Akt, and p-Akt. A standard immunoperoxidase technique was used to detect the avidin-biotin peroxidase complex. Immunostaining was visually scored with the histoscore method by two surgical pathologists.
Patient characteristics were as follows: 17 men and 22 women; median age, 66 years; and American Joint Committee on Cancer stage I, 5 patients; stage II, 4 patients; stage III, 27 patients; and stage IV, 3 patients. The tumor was World Health Organization grade 1 in 4, grade 2 in 17, and grade 3 in 18 cases. Adjuvant therapies were chemotherapy (n = 6), radiotherapy (n = 1), and chemoradiotherapy (n = 17). Immunohistochemistry revealed positive expression of EGFR in 30.8%, Erk in 92.3%, p-Erk in 45.9%, Akt in 71.8%, and p-Akt in 20.5% of cases. On univariate analyses, tumor grade (P = .0098), p-Akt (P = .0003), and p-Erk (P = .0052) expression correlated with survival. On multivariate analyses, age (P = .0002; hazard ratio [HR], 1.8), grade (P = .00318; HR, 3.0), Akt (P = .0433; HR, .4), p-Akt (P = .0002; HR, .2), and p-Erk (P = .0003; HR, 3.5) expression correlated significantly with survival.
p-Erk and p-Akt expression may have prognostic and therapeutic implications in pancreatic cancer.
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