A pilot study to compare FXR expression in normal and malignant tissue in receptor-positive early-stage breast cancer

Abstract

e14645 Background: Farnesoid X receptor (FXR), a nuclear receptor, is a ligand dependent transcriptional factor regulating cholesterol and carbohydrate metabolism. Recently, FXR was shown to have a contributing role in colorectal cancer. We hypothesize that FXR expression changes from normal to premalignant to malignant tissue in patients with breast cancer. Methods: We identified 16 paired formaldehyde fixed, paraffin embedded tissue (normal, premalignant, and malignant) from patients with receptor positive, early stage breast cancer. Clinical information was extracted from a prospective database initiated in 2006 under institutional approval. Immunohistochemical staining of FXR using a validated polyclonal antibody was completed with appropriate positive and negative controls. The slides were graded independently by two investigators using an agreed upon scale to detect the percentage of positively stained cells to the nearest 10th percentile. Statistical analysis was performed by ANOVA and Student's t-test. A p-value of 0.05 was considered significant in all analyses. Results: Normal tissue and invasive cancer was identified in all 16 patient specimens. Of the 16 invasive cancers, 12 were ductal and 4 were lobular. 8/16 (50%) of the specimens also contained non-invasive cancer. 5/16 patients (31%) had N1 disease. FXR expression did not correlate with grade, histology, stage, or lymph node status. However, FXR expression increases with malignant transformation of the breast cancer cell. The mean percentage of cells staining positive for FXR in normal breast tissue was 58%, non-invasive 72% and invasive 79%. FXR staining in normal breast tissue was significantly less when compared to both invasive and noninvasive cancer (p< 0.007). Conclusions: FXR expression is upregulated in breast cancer when compared with expression in normal tissue and appears to progressively increase along the continuum of malignancy. Our pilot study results warrant further evaluation into FXR as a predictive biomarker for breast cancer, given the ability to target FXR via development of non-toxic oral ligands. No significant financial relationships to disclose.