Laser Microdissection and Two-Dimensional Difference Gel Electrophoresis Reveal the Role of a Novel Macrophage-Capping Protein in Lymph Node Metastasis in Gastric Cancer

To
reveal the proteomic background of lymph node metastasis (LNM)
in gastric cancer, we performed a proteomic study of tumor and matched
nontumor tissues obtained from surgically resected specimens of 22
patients with or without LNM. Using laser microdissection, we recovered
specific populations of tumor and nontumor cells. We used two-dimensional
difference gel electrophoresis with a large format electrophoresis
apparatus to obtain protein expression profiles consisting of 3228
protein spots, and we classified them according to their expression
pattern. We found that macrophage-capping protein (CapG) was up-regulated
in the tumor tissues of patients with LNM, whereas it showed an equivalent
expression level between nontumor and tumor tissues of patients without
LNM. It was reported that CapG associated with invasion and metastasis
in various malignancies. However, CapG was not investigated in gastric
cancer until our study. Western blotting of the laser microdissected
tissue samples confirmed up-regulation of CapG in the tumor tissues
of patients with LNM. Functional assays demonstrated that CapG promoted
tumor cell invasion, but not cell proliferation. The association between
CapG expression and LNM is a novel finding in gastric cancer. Further
investigation for a prognostic utility of CapG may lead to a risk
stratification therapy for gastric cancer.