Potential Coagulation Factor-Driven Pro-Inflammatory Responses in Ovarian Cancer Tissues Associated with Insufficient O₂ and Plasma Supply

Abstract

Tissue factor (TF) is a cell surface receptor for coagulation factor VII (fVII). The TF-activated fVII (fVIIa) complex is an essential initiator of the extrinsic blood coagulation process. Interactions between cancer cells and immune cells via coagulation factors and adhesion molecules can promote progression of cancer, including epithelial ovarian cancer (EOC). This process is not necessarily advantageous, as tumor tissues generally undergo hypoxia due to aberrant vasculature, followed by reduced access to plasma components such as coagulation factors. However, hypoxia can activate TF expression. Expression of fVII, intercellular adhesion molecule-1 (ICAM-1), and multiple pro-inflammatory cytokines can be synergistically induced in EOC cells in response to hypoxia along with serum deprivation. Thus, pro-inflammatory responses associated with the TF-fVIIa-ICAM-1 interaction are expected within hypoxic tissues. Tumor tissue consists of multiple components such as stromal cells, interstitial fluid, albumin, and other micro-factors such as proton and metal ions. These factors, together with metabolism reprogramming in response to hypoxia and followed by functional modification of TF, may contribute to coagulation factor-driven inflammatory responses in EOC tissues. The aim of this review was to describe potential coagulation factor-driven inflammatory responses in hypoxic EOC tissues. Arguments were extended to clinical issues targeting this characteristic tumor environment.

Keywords: coagulation; hypoxia; inflammation; ovarian cancer.

Figure 1

Extrinsic coagulation cascade initiated by tissue factor (TF)-activated coagulation factor VII (fVIIa) dimer formation on the surface of extravascular cells. The TF-fVIIa complex triggers calcium ion-dependent sequential enzymatic reactions in response to injury of blood vessels composed of endothelial cells and the vessel wall. Formation of fibrin polymers together with platelets and red blood cells leads to clot formation to halt bleeding. This fibrin deposition process is supported by von Willebrand factors (vWFs). Blood coagulation completes by clot formation with other factors, such as platelets and red blood cells. Schematics of fibrin(ogen) with characteristic domains D and E are also shown. fXa: activated factor X; flXa: activated fIX; : cleavage; : conversion.

Figure 2

Activation pathways of PAR1 associated with the plasma membrane. In addition to thrombin, the TF-fVIIa-fXa complex can also cleave and activate the G protein-coupled receptor PAR1 to transmit cellular signals. PAR1 can couple multiple G-proteins to activate various signaling mechanisms. PAR: protease-activated receptor; ERK: extracellular signal-regulated kinase; PKC: protein kinase C; : cleavage; : conversion; : binding; : intracellular signaling.

Figure 3

Interaction between receptor molecules on the cancer cell surface and inflammatory cells. (A) Schematics of intercellular adhesion molecule-1 (ICAM-1) and integrin structures. Dotted lines in the ICAM-1 structure show disulfide bond formation; (B) A schematic of interaction between cancer cells and inflammatory cells, leading to malignancy. ICAM-1 and a heterodimer of integrins on the surface of cancer cells can associate with integrin dimers on the surface of platelets and leukocytes via fibrin(ogen). Dotted lines indicate non-covalent association.

Figure 4

Potential contribution of protein disulfide isomerase (PDI) and various environmental factors in regulation of the TF-fVIIa complex on the surface of epithelial ovarian cancer (EOC) cells. Due to hypoxia, followed by acidification of tumor microenvironment (TME) by lactate production, the cell surface PDI is expected to be inhibited. In this case, TF shifts to its reduced inactive form (designated with the bold black arrow), although encrypted TF may still transmit signals [94]. Additionally, TF-fVIIa activity can be affected by various hypoxia-related cellular and environmental factors such as regulation of the PDIA2 gene, lipid metabolism, endoplasmic reticulum (ER) stress, proton exchanger molecules, phosphatidylserine, and metal ions. Dashed arrows and T-bars indicate the activation process and suppression process, respectively. LD: lipid droplet; TFPI: tissue factor pathway inhibitor-1; LCFAs: long chain fatty acids; HIF: hypoxia inducible factor. See text for numbers (1–17).

Figure 5

cDNA microarray analysis [34] revealed that interleukins (CXCLs) are upregulated at the highest levels in OVSAYO cells when cells are simultaneously exposed to hypoxia and serum starvation conditions. Cells were cultured under normoxia (N) and hypoxia (H) for 16 h in the presence (+) or absence (‒) of fetal calf serum (FCS), and then total RNA was isolated for transcriptome analysis. (A) Line graph representation of gene expression levels under four different culture conditions. Genes synergistically and most activated under “H/FCS‒” condition (688 total measurements) are shown as red lines. Among them, nine genes correspond to CXCLs, as highlighted in black. (B) Scatter plot representation of genes shown in (A). Expression levels (processed signal) under “H/FCS‒” conditions were plotted as a function of raw signal according to the heat map on the right. Highly expressed CXCLs were assigned to each dot.

Figure 6

Potential coagulation factor-driven inflammatory responses within TME of EOC exposed to hypoxia. The coagulation factors derived from circulation, stromal cells, and cancer cells can connect EOC cells to platelets and leukocytes. Cell surface receptors and protease can also be activated under hypoxia, potentially transmitting cellular signaling. These molecular events are expected to facilitate survival and metastatic potential of EOC cells. Fb: fibroblast; CAF: cancer-associated fibroblast; TAM: tumor-associated macrophage; Mph: macrophage; Col: collagen; Hln: hyaluronan; PT: prothrombin: Fng; fibrinogen; VEGF: vascular endothelial growth factor; TIF: tissue interstitial fluid; EVs: extracellular vesicles; TNF-α: tumor necrosis factor-α. Dashed lines are indicative of non-covalent association. T-bars indicate suppression process. : secretion; : interaction; : intracellular signaling.