LGR5 is associated with tumor aggressiveness in papillary thyroid cancer

Abstract

// Gregory Michelotti 1 , Xiaoyin Jiang 2 , Julie Ann Sosa 3 , Anna Mae Diehl 1 , Brittany Bohinc Henderson 4 1 Division of Gastroenterology, Duke University Medical Center, Durham, North Carolina, USA 2 Department of Pathology, Duke University Medical Center, Durham, North Carolina, USA 3 Department of Surgery, Duke University Medical Center, Durham, North Carolina, USA 4 Division of Endocrinology, Diabetes and Metabolism, Wake Forest University, Winston-Salem, North Carolina, USA Correspondence to: Brittany Bohinc Henderson, e-mail: bbhender@wakehealth.edu Keywords: R-spondin, Wnt, β-catenin, metastasis, BRAFV600E Received: May 07, 2015      Accepted: September 14, 2015      Published: September 25, 2015 ABSTRACT PURPOSE: Leucine-rich repeat-containing G-protein-coupled receptor 5 (LGR5) is a cancer stem cell marker and a down-stream target in Wnt/β-catenin signaling. In human papillary thyroid cancer (PTC), over activation of Wnt/β-catenin has been associated with tumor aggressiveness. PATIENTS AND METHODS: Using established human cell lines (TPC-1, KTC-1, Nthy-ori-3–1), we report LGR5 and R-spondin (RSPO1–3) overexpression in PTC and manipulate LGR5 and Wnt/β-catenin signaling via both pharmacologic and genetic interventions. We test the association of LGR5 tumor expression with markers of PTC aggressiveness using a Discovery Cohort ( n = 26 patients) and a Validation Cohort ( n = 157 patients). Lastly, we explore the association between LGR5 and the BRAFV600E mutation ( n = 33 patients). RESULTS: Our results reveal that LGR5 and its ligand, RSPO, are overexpressed in human PTC, whereby Wnt/β-catenin signaling regulates LGR5 expression and promotes cellular migration. In two separate cohorts of patients, LGR5 and RSPO2 were associated with markers of tumor aggressiveness including: lymph node metastases, vascular invasion, increased tumor size, aggressive histology, advanced AJCC TNM stage, microscopic extra thyroidal extension, capsular invasion, and macroscopic invasion. As a biomarker, LGR5 positivity predicts lymph node metastasis with 95.5% sensitivity (95% CI 88.8%-98.7%) and 61% specificity (95% CI: 48.4%–72.4%) and has a negative predictive value (NPV) of 91.3% (95% CI 79.2%–97.5%) for lymph node metastatic disease. In human PTC, LGR5 is also strongly associated with the BRAFV600E mutation ( p = 0.005). CONCLUSION: We conclude that overexpression of LGR5 is associated with markers of tumor aggressiveness in human PTC. LGR5 may serve as a future potential biomarker for patient risk stratification and loco regional metastases in PTC.