Relative Factors And Serum MiRNAs For Endocrine Therapy Resistant Patients With Estrogen Receptor-Positive Breast Cancer

Backgroun d/AimsCurrent endocrine therapies have improved the quality of life and survival of millions of females with estrogen receptor(ER)-positive breast cancer worldwide in the past three decades. However the effectiveness of endocrine therapy is limited by occurrence of resistance. By now the mechanisms that lead to endocrine resistance are still not totally clear. Therefore, the purpose of the present study was to assess the clinical influencing factors on the resistance to the endocrine therapy in ER-positive patients. In this study, we have also identified the miRNAs expression profiles in the serum of the patients with endocrine therapy resistance or sensitivity, and attempted to assess the distinctive miRNAs as noninvasive biomarker for clinical diagnosis for endocrine therapy resistance.Methods1. Clinical and pathological data of 223 patients with ER-positive breast cancer treated in Nanjing General Hospital of Nanjing Military Command from Jan 1st 2006 to Nov 30th 2009 were collected. The onset of age (≤35、35～50、>50Y), menstrual status, tumor sizes (T1、T2、T3), tumor grades, lymph node ratio (≤0.20、0.20～ 0.65、>0.65), expression levels of PR and Her-2, neoadjuvant chemotherapy and radiotherapy were analyzed by Kaplan-Meier survival plots and multivariable Cox hazard regression analysis to identify influencing factors for endocrine therapy resistance.2. Serum samples were obtained from 20 ER-positive patients who had suffered from endocrine therapy resistance and 40 endocrine therapy sensitive controls with matched age and clinical stage. TaqMan low-density arrays (TLDAs) were used to perform an initial screening of miRNAs expression in the pooled samples from 5 endocrine resistant patients and 5controls. Among the markedly aberrant miRNAs those reported by other experts were validated using a stem-loop reverse transcription polymerase chain reaction (RT-PCR) and quantitative real-time polymerase chain reaction (qRT-PCR) assay in serum samples of the endocrine resistant patients and sensitive controls.Results1. The median follow-up period was 77 (12～106) months. Among the 223 cases,35 cases (15.70%) suffered from the endocrine therapy resistance. Totally 88.57% of endocrine therapy failures happened within 5 years. The univariate analysis and Cox multivatiate regression revealed that tumor size, lymph node ratio, expression levels of PR and Her-2 were independent influencing factors for endocrine therapy resistance (P<0.05).2. The data obtained from the TLDAs demonstrated that 5 serum miRNAs were significantly higher and 16 miRNAs were lower in the endocrine therapy resistant patients than in the controls. Based on the TLDA results and relevant literature, miRNA-222 and miRNA-146a were subsequently validated. Compared with sensitive controls, the expression of miRNA-222 in the serum of endocrine resistant patients was significantly increased (p=0.011). Although the serum miRNA-146a of resistant patients was downregulated, no significant difference was found between the resistant patients and sensitive controls (p=0.086).Conclusions1. Large size of tumor, high lymph node ratio, overexpression of Her-2 and loss of PR were risk factors for the endocrine therapy resistance of breast cancer with positive estrogen receptors.2. The serum miRNA-222 of endocrine resistant patients was significantly increased. The circulating miRNA-222 may provide a novel, non-invasive biomarker for the endocrine therapy resistance of ER-positive breast cancer.