Abstract P2-11-09: A p53-based strategy for protecting normal breast tissue from chemotherapy-induced damage in breast conserving therapy
Authors: Long M , Huang Y , Liu R , Liu R , Su H 
Published: March 2017

Abstract
Introduction: Currently, the global rate of breast conserving therapy (BCT) increased steadily. Most patients with BCT are treated with chemotherapy. However, most chemotherapeutical drugs that kill cancer cells also cause undesirable injuries to normal breast tissues. Normal breast tissue damage will further cause destruction of female secondary sex characteristics, and ultimately affect the quality of patients' lives. Therefore, it is urgent to protect the normal breast tissues for BCT patients during chemotherapy. More and more evidence shows that chemotherapy-induced normal tissue damage is mainly caused by the activation of p53 pathway, which is separate from the tumor suppressor pathway of p53. Previous studies found that use of low-dose arsenic (LDA) could temporarily and reversibly suppresses p53 activation. There are recent studies showing LDA selectively protect bone marrow and gastrointestinal tract during cancer treatment. Therefore, we hypothesize that use of LDA to temporary inhibit p53 activity will be a new strategy to protect the breast normal tissues for breast conserving patients.
Methods: Human breast epithelial cell line, MCF-10A, and three breast cancer cell lines MCF-7 (estrogen receptor and E6 expressed), MDA-MB-231 (triple negative and p53 mutated) and BT-474 (HER2 overexpressed and p53 mutated), were tested in this study. All cells were pretreated with either PBS or 100nM sodium arsenite for 12 hours, followed by 375 μM 5-fluorouracil (5-FU) or DMSO for 24, 48 and 72 hours. Cellular viability was determined by MTT assay and cell morphology was recorded under a light microscope.
Results: Morphology changes after 5-FU treatment include: the cell density decreased, the cells became rounded in shape, the cell membrane atrophied, the cell nuclei underwent pyknosis, and the cells formed a globule with nuclear and cytoplasmic fragments surrounded by the cell membrane. LDA pretreated-MCF10A cells showed significant reduced growth inhibition by 5-FU at all detected time pointes as demonstrated by MTT assay and morphology observation. Interestingly, LDA treatment had negligible effect on survival in breast cancer cells.
Table 1. Cell growth evaluated by MTT assay.Time after 5-FU treatment(h)Cell lineControl (%)LDA (%)5-FU (%)LDA+5-FU (%)24MCF-10A10099.3051.3878.28 MCF-710097.3268.5165.64 MDA-MB-23110094.9669.5669.13 BT-47410098.7971.5071.5948MCF-10A10097.3729.1347.74 MCF-710091.7649.9148.95 MDA-MB-23110093.769.048.81 BT-47410092.0460.4361.0072MCF-10A10096.3418.3443.64 MCF-710091.0142.0039.40 MDA-MB-23110093.596.445.39 BT-47410091.4635.7636.95
Conclusion: Temporary LDA pretreatment selectively protected normal tissue cells, but not tumor cells from toxicity of 5-FU chemotherapy. Our findings indicated that LDA pretreatment is a potential strategy to protect normal breast tissue during chemotherapy for BCT patients.
RL and HS contributed equally to this work.
Citation Format: Long M, Huang Y, Liu R, Liu R, Su H. A p53-based strategy for protecting normal breast tissue from chemotherapy-induced damage in breast conserving therapy [abstract]. In: Proceedings of the 2016 San Antonio Breast Cancer Symposium; 2016 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2017;77(4 Suppl):Abstract nr P2-11-09.