Background: There is growing evidence that topoisomerase II-alpha (TOPOIIα) is a marker for anthracycline-, and microtubule-associated protein tau (MAPT) for taxane sensitivity. HER2 has been described as a marker of both anthracycline and taxane sensitivity.The goal of our study was to examine the predictive and prognostic value of TOPOIIα, MAPT and HER2 expression in breast cancer patients (pts) who received neoadjuvant chemotherapy (NAC) based on anthracycline-taxane regimens. We analyzed the relationship between these biomarkers and pathological complete response (pCR), disease-free survival (DFS) and overall survival (OS). Methods: Between November 1993-2009, 140 pts (mean age 52 years) with locally advanced breast cancer (T1-4, N0-3, M0) were retrospectively studied. The study contained 2 groups: group A included 85 pts who received NAC with an anthracycline-taxane regimen and group B included the last 55 pts who received NAC with only an anthracycline-based regimen. HER2 was tested by immunohistochemistry (IH) or FISH, TOPOIIα by CISH and MAPT by IH. Expression of these proteins was evaluated in core needle breast biopsy. Results: Overall, 12 pts (8.5%) had a pCR. TOPOIIα was amplified in 6 (4%) of the tumors. Among pts without amplification, 6 (4%) had deletion of the TOPOIIα, and 10 (7%) polysomia of chromosome 17. TOPOIIα gene aberrations (amplification, deletion, polysomia), which was present in 22 (25%) of the tumors, was a strong predictive factor for pCR (p=0.018) but showed no direct association with prognostic outcome in multivariate analysis. HER2 amplification, which was present in 16% (21) of the tumors, show no direct association with pCR, DFS or OS. Finally, differences by treatment arm or pCR in low versus high MAPT expression groups were not observed, indicating that MAPT is not a useful predictive marker for taxane-based chemotherapy. In multivariate analysis high MAPT expression was associated with longer DFS (p=0.002). Conclusions: TOPOIIα gene aberrations but not HER2 are highly predictive of pCR for anthracycline-based regimen. MAPT is not associated with response to taxanes but has a prognostic value.