Yoshio Tsunezuka

Expression of vascular endothelial growth factor (VEGF)-C and that of its receptors were assessed in non-small cell lung cancer. Immunohistochemistry revealed positive VEGF-C expression in 38.7% (24/62) of the patients studied. A significant positive correlation was found between VEGF-C in cancer cells and VEGF receptor-3 (VEGFR-3) in vascular endothelial cells, but not between VEGF-C in cancer cells and VEGFR-2 in endothelial cells. In this cohort of lung cancer patients, VEGF-C expression was significantly associated with lymph node metastasis, lymphatic vessel invasion, and worse outcomes after the operation. Although the independent prognostic impact of VEGF-C and VEGFR-3 was not clear, VEGFR-2 expression in endothelial cells retained the independency as the prognostic indicator. In light of these findings, we conclude that VEGF-C plays an important role in lymphatic invasion/metastasis and tumour progression in non-small cell lung cancer.

Matrix metalloproteinases (MMPs), which degrade the components of the extracellular matrix, are key enzymes involved in the tissue remodeling of multicellular organisms. Since MMPs are secreted as inactive zymogens (pro-MMPs), they have to be activated to function. We identified a membrane-type MMP (MT-MMP) that activated proMMP-2 (pro-gelatinase A = 72 kDa type IV pro-collagenase) and described its expression on the invasive tumor cell surface. In this study we further examined the expression and role of MT-MMP in the activation of proMMP-2 during mouse embryogenesis. Northern blotting demonstrated that MT-MMP expression was increased together with that of MMP-2 and its inhibitor gene, TIMP-2, in embryos depending upon the number of days after gestation, and decreased with maturation after birth. In situ hybridization and immunohistochemistry localized MT-MMP mRNA and protein in the cells of ossifying tissues where both MMP-2 and TIMP-2 were expressed. Activated MMP-2 was detected by gelatin zymography in the lysates prepared from the micro dissected tissues that expressed the three genes. The activation rate of proMMP-2 was proportional to the expression of MMP-2 and MT-MMP. These results indicated that proMMP-2 activation through its activator, MT-MMP, is a physiological system used by organisms to initiate tissue remodeling on the cell surface.

Membrane-type matrix metalloproteinase 1 (MT1-MMP) is a member of the recently identified unique membrane-type subgroup in the matrix metalloproteinase (MMP) family. MT1-MMP has proteolytic activity against components in the extracellular matrix and activates progelatinase A (72-kDa type IV procollagenase/proMMP-2) on the cell surface. Because MT1-MMP is frequently expressed in a variety of tumors, we examined its contribution to their metastatic potential. The mouse lung carcinoma cell line Madison 109 was transiently transfected with a MT1-MMP expression plasmid and inoculated into the tail vein of BALB/c mouse. Fate of the transfected cells was monitored by the neo(r) gene in the plasmid using the quantitative PCR method. The survival rate of the parental cells in lung was 0.7% of the inoculated cells. It was increased by 3-fold with the MT1-MMP transfected cells and the number of the lung nodules increased accordingly. Immunostaining of the consecutive tissue sections revealed that lung nodules expressing MT1-MMP were positive for gelatinase A as well, whereas MT1-MMP-negative cells were not stained for gelatinase A at all. Thus, MT1-MMP-expressing cells acquire specific ability to bind exogenous progelatinase A.