Tissue factor (TF) is the primary cellular initiator of blood coagulation and a modulator of angiogenesis and metastasis in cancer. Indeed, systemic hypercoagulability in patients with cancer and TF overexpression by cancer cells are both closely associated with tumor progression, but their causes have been elusive. We now report that in human colorectal cancer cells, TF expression is under control of 2 major transforming events driving disease progression (activation of K-ras oncogene and inactivation of the p53 tumor suppressor), in a manner dependent on MEK/mitogen-activated protein kinase (MAPK) and phosphatidylinositol 3-kinase (PI3K). Furthermore, the levels of cell-associated as well as circulating (microvesicle-associated) TF activity are linked to the genetic status of cancer cells. Finally, RNA interference experiments suggest that TF expression is an important effector of the K-ras-dependent tumorigenic and angiogenic phenotype in vivo. Thus, this study establishes a causal link between cancer coagulopathy, angiogenesis, and genetic tumor progression. ( IntroductionCancer is believed to arise and progress toward increasing malignancy as a result of cumulative genetic "hits" sustained by the tumor cell genome. Paradigmatic in this regard is the development of colorectal carcinoma (CRC), where sequential transition through clinical stages of the disease is paralleled by a series of well-characterized alterations in proto-oncogenes and tumor suppressor genes. 1 In this tumor type, activation of mutant K-ras and subsequent inactivation/loss of p53 are key changes, which drive many interrelated aspects of the malignant phenotype including aberrant mitogenesis and survival. 2 Moreover, both of these genetic alterations are thought to contribute to proangiogenic properties of affected cancer cells, 3,4 and thereby enable them to exploit the host vascular system to advance malignant growth and metastasize in vivo. 5 The involvement of the vascular system in malignancy encompasses not only angiogenesis but also systemic hypercoagulability. Blood clotting abnormalities are detected in up to 90% of patients with metastatic disease, and thrombosis represents the second most frequent cause of cancer-related mortality. 6 Cancer coagulopathy is often linked to up-regulation of tissue factor (TF), the primary cellular initiator of the blood coagulation cascade. 7,8 Interaction of coagulation factor VIIa with TF on the cell surface leads to activation of factor X and generation of thrombin, with subsequent involvement of platelets and formation of a fibrin clot. 9 Remarkably, as a member of the class II cytokine receptor family, TF is also capable of transducing intracellular signals and regulating gene expression. 10,11 Interestingly, elements of the coagulation/fibrinolytic system in general, 12 and TF in particular, have been implicated in regulation of angiogenesis, 13,14 as well as tumor growth 15 and metastasis 16 in various experimental settings. This is consistent with the observed up-regulation of TF in huma...

Gallic acid (GA), a food component that is especially abundant in tea, is an antimutagenic, anticarcinogenic and anti-inflammatory agent. We conducted a study using acidum gallicum tablets that contained 10% GA and 90% glucose and a black tea brew that contained 93% of its GA in free form to determine the pharmacokinetics and relative bioavailability of GA in healthy humans. After the administration of a single oral dose of acidum gallicum tablets or tea (each containing 0.3 mmol GA) to 10 volunteers, plasma and urine samples were collected over various time intervals. Concentrations of GA and its metabolite, 4-O-methylgallic acid (4OMGA), were determined, and the pharmacokinetic parameters were calculated. GA from both the tablets and tea was rapidly absorbed and eliminated with mean half-lives of 1.19 +/- 0.07 and 1.06 +/- 0.06 h and mean maximum concentrations of 1.83 +/- 0.16 and 2.09 +/- 0.22 micromol/L (plasma), respectively. After oral administration of the tablets and black tea, 36.4 +/- 4.5 and 39.6 +/- 5.1% of the GA dose were extracted in urine as GA and 4OMGA, respectively. The relative bioavailability of GA from tea compared with that from the tablets was 1.06 +/- 0.26, showing that GA is as available from drinking tea as it is from swallowing tablets of GA.

In cancer, the extensive methylation found in the bulk of chromatin is reduced, while the normally unmethylated CpG islands become hypermethylated. Regions of solid tumors are transiently and/or chronically exposed to ischemia (hypoxia) and reperfusion, conditions known to contribute to cancer progression. We hypothesized that hypoxic microenvironment may influence local epigenetic alterations, leading to inappropriate silencing and re-awakening of genes involved in cancer. We cultured human colorectal and melanoma cancer cell lines under severe hypoxic conditions, and examined their levels of global methylation using HPLC to quantify 5-methylcytosine (5-mC), and found that hypoxia induced losses of global methylation. This was more extensive in normal human fibroblasts than cancer cell lines. Cell lines from metastatic colorectal carcinoma or malignant melanoma were found to be markedly more hypomethylated than cell lines from their respective primary lesions, but they did not show further reduction of 5-mC levels under hypoxic conditions. To explore these epigenetic changes in vivo, we established xenografts of the same cancer cells in immune deficient mice. We used Hypoxyprobe to assess the magnitude of tissue hypoxia, and immunostaining for 5-mC to evaluate DNA methylation status in cells from different regions of tumors. We found an inverse relationship between the presence of extensive tumor hypoxia and the incidence of methylation, and a reduction of 5-mC in xenografts compared to the levels seen in the same cancer cell lines in vitro, verifying that methylation patterns are also modulated by hypoxia in vivo. This suggests that epigenetic events in solid tumors may be modulated by microenvironmental conditions such as hypoxia.