Functions of peptides involved in cancer metastasis

We retrospectively investigated sera, obtained from 47 patients after the complete cure of liver cancer, using follow-up proteome analysis for 8 years, and found a protein, whose expression increased over time, peaked at the definitive diagnosis of bone metastases by bone scintigraphy, and tapered after the start of subsequent treatment. Fractions obtained by the reverse-phase HPLC of this protein were digested with trypsin and examined by LC-MS/MS analysis. The data were analyzed with a Mascot database search. As a result, the mass of fragment 576-628 of the C-terminal region of alpha-fibrinogen precursor was 5,805, which corresponded to that of the target peak. On the other hand, the mass of region 576-629 (with Val at the C-terminal) was 5,904, a mass value 99 higher than the target peak. This corresponds to a peak detected in the serum sample at a mass value 100 higher than the target peak. This peak with a mass value 100 higher was the same as the target peak in terms of chromatographic behavior, indicating that this peak had a protein sequence similar to that of the target peak. The isoelectric point (pI) of the fragment of region 576-628 was 8.07. This is consistent with the fact that the target peak indicates the behavior of a basic material in ion exchange. Thus, we concluded that the target peak 5,813 was a fragment of C-terminal region 576-628 of the alpha-fibrinogen precursor. Vascular endothelial cells inherently control platelet functions and the coagulation and fibrinolytic system, and do not cause thrombus. A mixture of human lung cancer H460 cells and the target peptide was cultured, with normal human lung microvascular endothelial cells cultured on the 8.0-μm pore membrane of the upper layer and 3D Matrigel polymerized on the lower layer. Twenty-four hours later, the culture was examined by SEM electron microscopy to demonstrate that cancer cells grew on the 8.0-μm pore membrane and reached the normal human lung microvascular endothelial cells. Forty-eight hours later, neovessels were formed, around which platelet-containing thrombi were observed.