Relationship of HER2/TOP2A Gene Aberrations with RASSF1A/APC Gene Methylation Status in Breast Cancer

Abstract

Introduction: Breast cancer (BC) is a heterogeneous and complex disease characterized by the combination of multiple genetic alterations. HER2 gene amplification have prognostic and therapeutic implications in invasive BC. TOP2A is an essential nuclear enzyme that changes DNA topology. RASSF1A /APC genes are putative tumor-suppressor genes that frequently inactivated epigenetically in BC. The purpose of this study was to investigate the relationship between the HER2/TOP2A gene aberrations and promoter methylation in RASSF1A/APC genes in patients with high-risk BC. Methods: Formalin-fixed paraffin-embedded (FFPE) sections of tissue from 60 high-risk BC patients were obtained. The inclusion criteria of samples were applied to include the BC patients with (1) tumor size ≥2 cm (2) lymphatic metastases and/or distant metastases (3) patients under 40 years. HER2/TOP2A aberrations were evaluated using Fluorescence In Situ Hybridization (FISH) method. We examined the promoter methylation status of RASSF1A, and APC genes by Methylation-sensitive high resolution melting (MS-HRM) analysis . Results: HER2 amplification and TOP2A aberration were observed in 15/60 (25%) and 18/60 (30%) cases, respectively. HER2 amplification was associated with higher tumor grade (p=0.001), PR status (p=0.025), and TOP2A aberrations (p=0.004). RASSF1A and APC methylation were 58/60 (96.6%) and 26/60 (43.3%), respectively. There was a significant correlation between APC gene methylation and TOP2A aberrations. APC gene methylation was significantly higher in tumors with TOP2A aberration (p=0.026). Conclusion: Our results suggested that APC gene promoter hypermethylation was associated with TOP2A gene aberrations in patients with high-risk BC. This may be significant for targeted individual therapy. Additionally, it was confirmed that there was significant relationship of TOP2A gene aberrations with the HER2 gene amplification.