PLGF inhibition impairs metastasis of larynx carcinoma through MMP3 downregulation.

Cancer neovascularization plays a key role in the metastasis of larynx carcinoma. However, the molecular mechanism for the neovascularization control in larynx carcinoma is poorly understood. Since placental growth factor (PLGF) has been reported to be involved in pathological angiogenesis, and since matrix metalloproteinases (MMPs) are essential for extracellular matrix degradation during neovascularization, here we were prompted to examine whether PLGF and MMPs may play a coordinate role in the metastasis of larynx carcinoma. Our data showed that the expression of PLGF and MMP3 strongly correlated in the larynx carcinoma in the patients, and significant higher levels of PLGF and MMP3 were detected in the larynx carcinoma from the patients with metastasis of the primary cancer. Thus, we used a human larynx carcinoma cell line, Hep-2, to examine whether expression of PLGF and MMP3 may affect each other. We found that overexpression of PLGF in Hep-2 cells increased expression of MMP3, while inhibition of PLGF in Hep-2 cells decreased expression of MMP3. However, neither overexpression, nor inhibition of MMP3 in Hep-2 cells affected the expression level of PLGF. These data suggest that PLGF may function upstream of MMP3 in larynx carcinoma cells. We then analyzed how PLGF affected MMP3. Application of a specific ERK1/2 inhibitor to PLGF-overexpressing Hep-2 cells substantially abolished the effect of PLGF on MMP3 activation, suggesting that PLGF may increase expression of MMP3 via ERK/MAPK signaling pathway. Since anti-PLGF was recently applied in clinical trials to inhibit cancer-related angiogenesis, here our data further demonstrate that inhibition of cancer neovascularization by anti-PLGF is mediated not only by direct effect on endothelial growth and capillary permeability, but also by indirect effect via MMP3 on the extracellular matrix degradation in larynx carcinoma.