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Redox systems are often deregulated in cancer. To investigate whether altered expression predicted response to therapy, core biopsies from 80 locally advanced breast tumours (pre-six cycles of fluorouracil epidoxorubicin cyclophosphamide/fluorouracil adriamycin cyclophosphamide chemotherapy) were stained, using standard immunohistochemistry, to examine members of the Trx system (Trx1, TrxR and TxNIP), GST-π, GST-θ, catalase and MnSOD, and results were correlated with clinicopathological criteria. Significant results were obtained between TxNIP and progression-free survival (P = 0.008) and overall survival (P = 0.05), with low expression predicting a worse prognosis. A redox protein profile was developed, using an artificial neural network approach, with four of the proteins (catalase, GST-θ, GST-π and TxNIP), that stratifies patients into good/poor prognostic groups for overall survival with an 88% sensitivity and 87% specificity.
Conventional in vitro studies show that, using MCF-7 cells, targeting the Trx system by pretreatment with novel inhibitors (PMX464, PMX290 or IV-2) sensitises resistant cells to conventional C/T but that sensitivity of the parental line remains unchanged. Initial results, using single agents in novel three-dimensional (3D) systems, shows differential chemosensitivity, between normal and malignant cells, that is not apparent using conventional two-dimensional (2D) systems. Parental cell lines (MCF-7, MDA-MB-231) maintain or become more sensitive when exposed in 3D to conventional chemotherapy and Trx inhibitors (doxorubicin, PMX464/PMX290, IV-2 that is IC50 2D and 3D 0.01 μM, 0.5 μM, 25 μM - paclitaxel IC50 3D <0.01 μM, 2D 0.01 μM), assessed by clonogenic survival. Normal breast epithelial cells (MCF10As), however, show increased resistance to drugs (paclitaxel, doxorubicin, PMX464/PMX290, IV-2 IC50 3D 0.1 μM, 1 μM, >10 μM, 200 μM - IC50 2D 0.05 μM, 0.01 μM, 0.5 μM, 25 μM, respectively). The reasons for such altered chemosensitivity in 3D matrices are a focus of current work.
Results from the immunohistochemistry and in vitro studies suggest the suitability of targeting redox proteins, particularly the Trx system, in breast cancer to improve the efficacy of conventional therapies.