Preparation and Structure of a New Coagulation Factor XI Catalytic Domain for Drug Discovery

Human blood coagulation factor XI （FXI） is a key enzyme in the amplification phase of blood coagulation cascade, and is recognized as an important target for anti-coagulant development in recent years. We designed a new mutant form of FXIa catalytic domain rhFXI370-607 （N73Q-N113Q-C123S）, and report here the facile preparation, protein crystallization, and crystal structure of this protein. We highlight a few unique structural features of FXIa after comparison with the trypsin family serine proteases at sequence and structural levels. This work provides a foundation to develop new small molecular FXIa inhibitors with increased potency and specificity.

Extrahepatic synthesis of coagulation factor Ⅶ by colorectal cancer cells promotes tumor invasion and metastasis

Background Blood coagulation factor Ⅶ （FⅦ） is physiologically synthesized in the liver and released into the blood. Binding of FⅦ to tissue factor （TF） is related to the metastatic potential of tumor cells, also a significant risk factor in the development of hepatic metastasis in patients with colorectal cancer （CRC）. It has been found that some cancer cells can produce FⅦ extrahepatically. However, litte is known about FⅦ and CRC. We therefore hypothesized that CRC cells may synthese FⅦ, leading to tumor invasion and metastasis.Methods We detected the expression of FⅦ protein in 55 CRC specimens by immunohistochemical staining. The FⅦ mRNA in 45 of 55 CRC cases, 6 colon cancer cell lines and one hepatoma cell line was measured by real-time reverse transcription-PCR （RT-PCR）. Transwell invasion assays were performed to evaluate the changes of cell migration and invasion of LoVo cancer cells in vitro. We further observed the likely effectors regulated by the TF/FⅦa complex Western blotting assay.Results Extrahepatic synthesis of FⅦ was detected in the cytoplasm of 32 （58.2%） CRC specimens byimmunohistochemistry, but not in normal mucosa. Liver metastasis （P=0.003） and TNM staging （P=0.005） were significantly correlated with FⅦ antigen expression. The positive ratios in stages Ⅰ, Ⅱ, Ⅲ and Ⅳ were 33.3%, 40.0%,52.4% and 87.5%, respectively. The expression of FⅦ mRNA in CRC with hepatic metastasis was significantly higher than CRC without hepatic metastasis （5.33±2.88 vs. 1.47±0.51, P=0.03）. Ectopic FⅦa induced a slight increase （1.34-fold） in the number of migrating cells, which was inhibited by the specific TF antibody. The formation of TF/FⅦacomplex resulted in a marked increase in the expression of matrix metalloproteinases （MMP）-2 （3.5-fold） and MMP-9（4.7-fold） in a time-dependent and dose-dependent manner.Conclusions Extrahepatic synthesis of FⅦ by CRC cells may promote tumor invasion and metastasis. MMPs, as downstream effectors of TF/FⅦa signaling, facilitate the development of metastasis in colon cancer.