Abstract P6-08-30: The thrombin clotting pathway is upregulated in the stroma of pre-invasive breast cancer and further upregulated in aggressive invasive breast cancer phenotypes

Abstract

Abstract BACKGROUND Components of the thrombin (extrinsic) clotting pathway are upregulated in cancer. The clotting pathway factors tissue factor (TF) and Thrombin promote tumour progression through protease activated receptors PAR2 and PAR1 respectively. AIMS To determine if tumour expression (epithelial and stromal) of a procoagulant phenotype is associated with aggressive breast cancer phenotypes and reduced survival. METHODS Tumour expression of TF, thrombin, PAR1 and PAR2 was determined by immunohistochemistry in two cohorts. PROSPECTIVE STUDY Early invasive breast cancer (n=199), ductal carcinoma in situ (DCIS, n=42) and normal breast tissue samples (n=121). RETROSPECTIVE STUDY Early invasive breast cancer patients (n=144) with median follow-up of 69 (range 4 to 91) months. Procoagulant phenotype expression was correlated with tumour grade, proliferation (Ki67), ER and HER2 status (both cohorts), survival and recurrence (retrospective cohort). RESULTS PROSPECTIVE STUDY Epithelium Thrombin (p<0.01) but not TF, PAR1 or PAR2 was increased in invasive cancer compared to DCIS and normal breast tissue. Stroma TF, Thrombin, PAR1 and PAR2 were increased in the stroma of DCIS compared to normal breast stroma (p<0.05, all). In invasive breast cancer, TF was increased in invasive cancer compared to DCIS and compared to normal breast tissue (p<0.01, both). Thrombin, PAR1 and PAR2 were increased in invasive cancer compared to normal breast tissue (p<0.01, all). TF, thrombin, PAR1 and PAR2 were increased in high proliferating (p<0.01, all) and high grade cancer (p<0.01, all). TF (p=0.02) and PAR1 (p<0.01) were increased in ER negative cancer. TF, thrombin and PAR2 was increased in HER2 positive cancer (p<0.01, all). RETROSPECTIVE STUDY Stroma As with the prospective study, thrombin and PAR2 expression was increased in high proliferating cancer (p<0.05, both) and thrombin was increased in high grade cancer (p<0.05). PAR1, TF and thrombin expression was increased in ER negative cancer (p<0.05, all) and PAR2 was increased in HER2 positive cancer (p=0.05). Overall (OS) and disease-free survival (DFS) PAR1 stromal expression was an independent predictor of reduced OS (HR 3.3, 95% CI 1.3-8.3, p=0.01) but did not correlate with DFS. There was no association between epithelial PAR1 expression or epithelial or stromal TF, thrombin or PAR2 expression and DFS or OS. CONCLUSION Stromal upregulation of the thrombin pathway occurs in in-situ cancer, implying cancer-stromal communication at the pre-invasive stage. Stromal thrombin pathway components may have a role in the transition of pre-invasive to invasive cancer. Stromal (but not epithelial) thrombin pathway upregulation is associated with aggressive invasive breast cancer phenotypes and reduced survival. The thrombin pathway may provide a novel therapeutic target, particularly in ER negative, HER2 positive breast cancer. Citation Format: Hudhaifah Shaker, Nigel J Bundred, Harith Albadry, Sarah L Nicholson, Susan Pritchard, Karin Jirström, Goran Landberg, Cliona C Kirwan. The thrombin clotting pathway is upregulated in the stroma of pre-invasive breast cancer and further upregulated in aggressive invasive breast cancer phenotypes [abstract]. In: Proceedings of the Thirty-Seventh Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2014 Dec 9-13; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2015;75(9 Suppl):Abstract nr P6-08-30.