Abstract 3001: Alternatively spliced tissue factor promotes pancreatic cancer progression via carbonic anhydrase IX
Authors: Ramchandani Divya , Unruh Dusten , Bogdanov Vladimir Y. , Weber Georg F. 
Published: August 2015

Purpose: Here we study the mechanisms by which alternatively spliced Tissue Factor (asTF) contributes to pancreatic cancer progression in an advanced tumor micro-environment.

Background: There is a well-established association of the hemostatic system with cancer. Molecules of the coagulation pathway predispose patients to cancer-associated thrombosis and also trigger intracellular signaling pathways that promote cancer progression. The primary transcript of Tissue Factor, the main trigger of coagulation, undergoes alternative splicing yielding a secreted variant, termed asTF (alternatively spliced Tissue Factor). asTF does not have a physiologic function in hemostasis, but its expression positively correlates with advanced tumor stages, including pancreatic adenocarcinoma; asTF acts as a cell agonist by binding beta-1 intregrins. The hypoxia-inducible enzyme carbonic anhydrase IX (CAIX) may be overexpressed by cancer cells as a result of increased glycolysis and acidic pH. While it increases cancer cell survival by maintaining intracellular pH, carbonic anhydrase IX decreases the extracellular pH, making the extracellular space more acidic, which can increase cancer cell motility.

Methods: asTF-overexpressing pancreatic ductal adenocarcinoma cell line Pt45P1/asTF+ and the parent cell line Pt45P1 were tested for growth and mobility under normoxic conditions (5% CO2, ambient O2, 1000 mg/ml glucose) that model early stage tumors, and in the hypoxic environment of advanced-stage cancers (20% CO2, 1% O2 and 5 mM lactate).

Results: asTF overexpression in Pt45P1 cells conveyed higher proliferative ability. According to propidium iodide staining and flow cytometry, the major fraction of Pt45P1/asTF+ cells resides in the dividing G2/M phase of the cell cycle, while control Pt45P1 cells are mostly confined to the quiescent G0/G1 phase. asTF overexpression is also associated with significantly higher cell mobility. These observations were similar for cells plated under both normoxia and hypoxia. While normoxic cell culture conditions have been traditionally designed to maximize cell growth, an aggressive phenotype that may arise in an advanced-stage micro-environment prompted us to study the mechanisms that might promote invasive behavior under hypoxic tumor conditions. In a hypoxic environment, we observed an upregulation of carbonic anhydrase IX which was more pronounced in Pt45P1/asTF+ cells. Inhibition of carbonic anhydrase IX by the compound U-104 significantly decreased cell growth and mobility of Pt45P1/asTF+ cells in hypoxia, but not in normoxia.

Conclusion: Carbonic anhydrase IX is a novel downstream mediator of the asTF's effects in pancreatic cancer progression under hypoxic conditions that model advanced stage tumor micro-environment.

Citation Format: Divya Ramchandani, Dusten Unruh, Vladimir Y. Bogdanov, Georg F. Weber. Alternatively spliced tissue factor promotes pancreatic cancer progression via carbonic anhydrase IX. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 3001. doi:10.1158/1538-7445.AM2015-3001