Abstract 706: Ribonucleotide reductase small subunit M2 is a potential prognostic biomarker in human epidermal growth factor receptor 2- positive and triple negative breast cancers

Abstract

Abstract Human epidermal growth factor receptor 2 (HER2)-positive breast cancer and triple negative breast cancer (TNBC) are two subtypes with poor outcome of all breast carcinomas. However, among all the patients in these two subtypes some still yielded relatively better prognosis. Ribonucleotide reductase (RR) small subunits M2 was associated with cancer cell invasiveness and metastasis, which prognoses poor survival in many cancers. Here we investigated whether RRM2 could serve as a prognostic biomarker for breast cancers, especially HER2- positive and TNBC subgroups. One hundred seventy five assessable breast cancers (40 cases were HER2-positive or TNBC) were collected from affiliated hospital of Zhejiang University (ZJU set); and six published microarray data sets (total 1154 cases, 63 cases were identified as HER2- positive or TNBC) with pathoclinical and follow- up information were employed for validation. In the ZJU set, the protein level of RRM2 was determined by IHC. It was indicated that RRM2 was positively correlated with cell proliferative marker Ki-67 (trends P=0.018) and stem/progenitor cell marker CD44+/CD24-/low (P=0.044). Multivariate COX model revealed that RRM2 was an independent prognostic biomarker for both OS (Hazard Ratio, HR=2.79, 95%Cl 1.21-6.75) and PFS (Hazard Ratio, HR=1.82, 95%Cl 1.02-3.26) for all the breast cancers. Moreover, in HER2-positive or TNBC breast cancers, RRM2-high was significantly associated with poor survival (P=0.025). Consequently, none of the patients with RRM2-low died of breast cancer in HER2-positive or TNBC subgroups. Furthermore, above findings were validated in the published data sets. The mRNA level of RRM2 evaluated significantly in highly-invasive subtypes including Luminal B, HER2-positive and TNBC in comparison with Luminal A and unclassified subgroups (P<0.05). Overexpression of RRM2 was positively associated with poor differentiation (P<0.05), advanced AJCC stage (P<0.05) as well as poor survival (P<0.05) in a dose-dependent manner. It was also revealed that high expression of RRM2 prognosed poor survival (HR=5.56, 95% CI 1.14-99.9) in HER2-positive breast cancers or TNBC. Moreover, the RRM2-high (protein or mRNA levels) was associated with better response to chemotherapy comparing to RRM2-low. Taken together, the above findings suggested that RRM2 was a potential biomarker for poor survival in breast cancer, especially in HER2- positive breast cancer and TNBC. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 706. doi:1538-7445.AM2012-706