DNA topoisomerase IIα expression and the response to primary chemotherapy in breast cancer

The a isoform of Topoisomerase IIalpha (Topo IIalpha) is a proliferation marker as well as a target for several chemotherapeutic agents such as anthracyclines. In vitro studies have demonstrated the relationship between the Topo IIalpha expression level and chemosensitivity of target cancer cells. To verify this effect in vivo, we selected 125 patients presenting with T-2 >3 cm and T-3 N0-1 M-0 breast tumours who were treated by six cycles of primary chemotherapy, including epirubicin before any surgery. Therapy response was assessed by clinical and X-ray mammogram measurements of tumour shrinkage. The pretherapeutic core biopsies were immunostained with a monoclonal antibody (Ki-S7) against Topo IIalpha. Ki-S7 positivity ranged from 0 to 50% ( median, 15%). A high percentage of Ki-S7-positive cells (>15%) was associated with tumour regression under chemotherapy (OR = 2.88, CI: 1.3-6.4, P = 0.004). Ki-S7 further emerged as an independent predictor of tumour regression (OR = 3.34, CI: 1.41-7.93, P = 0.006), together with tumour size of less than 40 mm (OR = 3.82, CI: 1.58-9.25, P = 0.002) and negative oestrogen receptor ( ER) status (OR = 3.35, CI: 1.43-7.86, P = 0.005), in a multivariate analysis including tumour size, SBR grade, ER and PR status, Ki-67, p53 and Her-2/neu. Our clinical results confirm in vitro data on the relationship between Topo IIalpha expression and tumour chemosensitivity and thus may have important practical implications.