P1-06-14: Topoisomerase II alpha (Top2a) Protein Expression Is a Predictor for Response to Anthracycline-Based Chemotherapy (ATC-CT): Is It Due to Gene Amplification, HER2−Coamplification or a Summation of Pathways Leading to This Highly Proliferative Phenotype?

Abstract

Abstract Background: The evaluation of Top2a protein may be clinically more useful than gene alterations as a predictive marker for ATC-CT. In this study we assessed the association between gene copy number, gene and protein expressions of both TOP2A and HER2, and their effect on clinicopathological outcomes and management of breast cancer (BC). Methods: 1- To study the response to anthracycline based chemotherapy (ATC-CT): The associations between clinical outcomes and both gene copy number changes (using in-situ hybridization; CISH) and protein expression (using immunohistochemistry) were studied in the neoadjuvant and adjuvant settings: a) 250 locally advanced primary BC treated with Neoadjuvant ATC-CT with or without Taxane followed by surgery (S) + radiotherapy (RT); pathological complete response (pCR) was used as the primary end point (PEP), b) 245 BC in which all patients were treated with S + RT followed by Adjuvant ATC-CT; progression free survival (PFS) was used as PEP ii) 145 primary BC overexpressing HER-2 treated with S+ RT followed by sequential adjuvant ATC-CT+ trastuzumab; PFS was used as PEP. 2- To study the clinic-pathological association of TOP2A alterations, we evaluated TOP2A alterations detected by CISH and IHC in unselected series of 1650 consecutive cases of primary BC who treated with S + RT and received adjuvant CMF and/or endocrine therapies according to Nottingham prognostic index and ER status. 3- To study in details the molecular alterations of TOP2A/HER2, in 171 unselected series of primary BC, we evaluated a) gene copy number changes using both high resolution oligo array CGH and CISH, b) mRNA expression using Agilent gene expression array and c) protein expression using IHC. We analysed 48,000 gene transcripts using Artificial Neural Networks (ANN) and pathway analysis to identify genes and biological pathways that related to TOP2A gene alterations. Results: 1) In the ATC-CT neoadjuvant series, the pCR rate was 32/115 (28%) in tumours expressing high levels of Topo2A, compared to 5/74 (7%) in tumours expressing low levels of Topo2A (p<0.0001). In multivariate analysis, Top2A overexpression was an independent predictor for pCR (HR 5.1, CI 95%; 1.4−18.4, p<0.001). 2) TOP2A overexpression was strongly associated with mitotic index, histological grade, KIF2C, loss of p53 function and the absence of both BRCA1 and ATM inactivation (p<0.0001). 3) ANN and pathway analysis revealed that TOP2A-strongly correlated genes are involved in: mitotic cell cycle regulation especially M phase and cell division (AURKB, KIF2C, BRIC5, ASPM, CCNA2, BUB1, FBXO5, PTTG1, CDCA5, CDCA3 CDCA8), Kinesin and microtubules regulator genes (KIF2C, KIF11, KIF14, KIF20A, KIF23, and KIFC1), and metastases (BRIC5, BUB1B, CCNA2, CCNE, PRRG1, PRM2, STMN1). Conclusions: Top2A protein expression is an independent predictor for pCR after ATC-CT treatment. The high response rate of top2A protein overexpression supports the theory that Top2a protein is a direct target of ATC-CT in these highly proliferative tumour cells. Furthermore, evaluation of Top2A protein may lead to a clinically useful test. Citation Information: Cancer Res 2011;71(24 Suppl):Abstract nr P1-06-14.