PO-52 - Effect of tissue factor expression by colorectal cancer on cancer stem cell activity

Abstract

Abnormal Tissue factor (TF) expression occurs in many cancers including colorectal and is associated with a poor prognosis. TF expression promotes cancer stem cell (CSC) activity in breast and squamous cell carcinoma (SCC). The aim of the research is to determine the effect of TF expression by colorectal cancer cell lines on colorectal CSC activity. Colorectal cancer cell lines with high (DLD-1) and low (SW620) TF expression were stably transduced to knock down (TF-ve) and over express (TF+ve) TF. CSC activity was assessed using the cancer sphere assay (sphere forming efficiency (SFE)=spheres formed / cells plated) and by ALDH1 expression (by florescent activated cell sorting). When comparing transduced cells to their control the ALDH1 expression was normalised to their control. The naturally high TF expressing cell line (DLD-1) compared to the low TF expressing cell line (SW620) had a reduced SFE (0.7 (SD 0.39) vs 1.38 (SD 0.68), p<0.05) and less cells expressed ALDH1 (15.3% (SD 1.2) vs 26.9% (SD 2.1), p=0.02). DLD-1 TF+ve compared to its control had a reduced SFE (0.33 (SD 0.14) vs 0.66 (SD 0.42), p<0.01) and less cells expressed ALDH1 (0.72 (SD 0.069) p=0.001) (normalised to negative control). There was no difference in SFE (1.21 (SD 0.56) vs 1.29 (SD 0.50) p=0.4) and ALDH1 expression (0.81 (SD 1.00) p=0.5) between SW620 TF+ve and its control. DLD-1 TF-ve and SW620 TF-ve had increased SFE compared to their controls (DLD-1: 0.63 (SD 0.27) vs 0.41 (SD 0.35) p<0.01; SW620: 2.03 (SD 0.86) vs 1.21 (SD 0.70) p<0.01), and increased ALDH expression (DLD-1: TF-ve 1.23 (SD 0.74)p=0.04 and SW620: TF-ve 1.31 (SD 0.08) p<0.001 normalised to controls). Unlike in breast and SCC, in colorectal cancer cell lines TF inhibits CSC activity. This has significance if anti-tissue factor treatments are considered as an anti-cancer treatment as this may increase the cancer stem cell activity.