Overexpression of topoisomerase II protein (topo 2α) is postulated to be more closely associated with responsiveness to anthracycline-containing chemotherapy than human epidermal growth factor receptor type 2 (HER2) gene amplification or alterations in the topoisomerase II alpha gene (TOP2A). The authors used tissue microarrays from 477 of 710 premenopausal women with node-positive breast cancer randomized to CEF or CMF adjuvant chemotherapy in the NCIC Clinical Trials Group Mammary 5 (MA.5) trial. No significant interaction was found between treatment and continuous topo 2α level in either relapse-free (RFS) or overall survival (OS). In 136 patients (28.5%) whose tumors showed topo 2α overexpression by immunohistochemistry based on a cut-off of 13%, CEF was superior to CMF for RFS (adjusted HR 0.45; 95% CI 0.25-0.82; P = 0.009) and OS (adjusted HR 0.50; 95% CI 0.26-0.96; P = 0.04). When tumors lacked topo 2α overexpression, CEF was not superior for RFS (adjusted HR 0.88; 95% CI 0.64-1.22; P = 0.46) or OS (adjusted HR 0.95; 95% CI 0.66-1.38; P = 0.80). Interaction between topo 2α and treatment was borderline significant for RFS (P = 0.04) and OS (P = 0.05) and not substantially more significant than between TOP2A gene alteration (P (interaction) = 0.09 for RFS and 0.02 for OS) or HER2 overexpression (P (interaction) = 0.002 for RFS and 0.009 for OS). Topo 2α protein overexpression based on the cut-off identified in this study, TOP2A gene alterations and HER2 protein overexpression were each associated with responsiveness to anthracycline-containing chemotherapy. The topo 2α protein analysis was exploratory and will require further validation.
"Major focus has been on human epidermal growth factor receptor 2 (HER2) and topo IIα expression based on their localization in chromosome 17 as well as determinants of sensitivity to trastuzumab and anthracyclines, respectively. Indeed several reports have established expression of topo IIα in predicting sensitivity to adjuvant anthracycline therapy (Oakman et al., 2009; Brase et al., 2010; Kawachi et al., 2010; Di Leo et al., 2011; Du et al., 2011; Nikolényi et al., 2011; O’Malley et al., 2011). The evaluation of tissue inhibitor of metalloproteinase (TIMP-1) with HER2 or topo IIα has also suggested that a HT profile (HER2 amplified and/or TIMP-1 negative) or 2T profile (topo IIα aberrant and/or TIMP-1 negative) with substantial reduction in mortality but not relapse free survival events following adjuvant anthracycline containing therapy (Ejlertsen et al., 2010; Hertel et al., 2012). "
[Show abstract][Hide abstract] ABSTRACT: Inhibitors of topoisomerase II (topo II) are clinically effective in the management of hematological malignancies and solid tumors. The efficacy of anti-tumor drugs targeting topo II is often limited by resistance and studies with in vitro cell culture models have provided several insights on potential mechanisms. Multidrug transporters that are involved in the efflux and consequently reduced cytotoxicity of diverse anti-tumor agents suggest that they play an important role in resistance to clinically active drugs. However, in clinical trials, modulating the multidrug-resistant phenotype with agents that inhibit the efflux pump has not had an impact. Since reduced drug accumulation per se is insufficient to explain tumor cell resistance to topo II inhibitors several studies have focused on characterizing mechanisms that impact on DNA damage mediated by drugs that target the enzyme. Mammalian topo IIα and topo IIβ isozymes exhibit similar catalytic, but different biologic, activities. Whereas topo IIα is associated with cell division, topo IIβ is involved in differentiation. In addition to site specific mutations that can affect drug-induced topo II-mediated DNA damage, post-translation modification of topo II primarily by phosphorylation can potentially affect enzyme-mediated DNA damage and the downstream cytotoxic response of drugs targeting topo II. Signaling pathways that can affect phosphorylation and changes in intracellular calcium levels/calcium dependent signaling that can regulate site-specific phosphorylation of topoisomerase have an impact on downstream cytotoxic effects of topo II inhibitors. Overall, tumor cell resistance to inhibitors of topo II is a complex process that is orchestrated not only by cellular pharmacokinetics but more importantly by enzymatic alterations that govern the intrinsic drug sensitivity.
Frontiers in Pharmacology 08/2013; 4:89. DOI:10.3389/fphar.2013.00089 · 3.80 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: HER2 gene amplification and topoisomerase IIα gene (TOP2A) alteration have been associated with increased benefit from anthracycline compared to non-anthracycline containing adjuvant breast cancer chemotherapy in some but not other studies. Chromosome 17 centromere (CEP17) duplication was measured on TMAs from formalin-fixed paraffin-embedded specimens obtained from 639 of 716 premenopausal women with node positive breast cancer who received cyclophosphamide, epirubicin and fluorouracil (CEF) or cyclophosphamide, methotrexate and fluorouracil (CMF) in the randomized controlled mammary 5 (MA.5) adjuvant trial. The prognostic impact of CEP17 duplication and its interactions with treatment were studied for relapse-free survival (RFS) and overall survival (OS). Overall, CEP17 duplication was not significantly associated with RFS or OS in multivariate analysis. For patients whose tumours had normal CEP17 copy number there were no apparent benefits for CEF compared to CMF for RFS (HR 0.98; 95% CI 0.68-1.42) or OS (HR 1.10; 95% CI 0.72-1.69). For patients whose tumours had CEP17 duplication, there was significant benefit for CEF compared to CMF for RFS (HR 0.54; CI 0.33-0.89) and a trend towards significance for OS (HR 0.64; CI 0.37-1.09). The adjusted P values for interaction between treatment and CEP17 duplication were 0.09 for RFS and 0.13 for OS. This study suggests that CEP17 duplication has a borderline association with clinical responsiveness to anthracycline containing chemotherapy similar to previous results seen with HER2 amplification and TOP2A alteration in MA.5. An appropriately powered meta-analysis is required to discriminate the predictive value of these three candidate markers.
Breast Cancer Research and Treatment 01/2012; 131(2):541-51. DOI:10.1007/s10549-011-1840-4 · 3.94 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Anthracyclines are frequently used in the adjuvant setting for breast cancer treatment since it is considered that anthracycline-based chemotherapy treatment benefits breast cancer patients. Nonetheless, these drugs are associated with severe side effects and predictive factors, for sensitivity to anthracyclines, are warranted in clinical practice. Topoisomerase 2 alpha (TOP2A) is considered to be the molecular target of these drugs. The potential predictive value of TOP2A amplification and overexpression has been extensively studied in breast cancer patients treated with anthracyclines. However, results are not conclusive. In this paper, we review some of the published studies addressing the predictive value of TOP2A as well as the cellular functions of this enzyme and its status in breast cancer tissue.
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