Use of non-selective β-blockers is associated with decreased tumor proliferative indices in early stage breast cancer

// Alexa Montoya 1, 2, * , Clarissa N. Amaya 1, * , Andres Belmont 3, * , Nabih Diab 3 , Richard Trevino 3 , Geri Villanueva 3 , Steven Rains 1 , Luis A. Sanchez 4 , Nabeel Badri 4 , Salman Otoukesh 4 , Ali Khammanivong 5 , Danielle Liss 4 , Sarah T. Baca 6 , Renato J. Aguilera 6 , Erin B. Dickerson 5, 7 , Alireza Torabi 3, 8 , Alok K. Dwivedi 1, 3, 9 , Aamer Abbas 3, 4 , Karinn Chambers 3, 10 , Brad A. Bryan 1, 3 , Zeina Nahleh 3, 4 1 Department of Biomedical Sciences, Texas Tech University Health Sciences Center, El Paso, Texas, USA 2 Department of Biology, University of Texas, El Paso, Texas, USA 3 Paul L. Foster School of Medicine, Texas Tech University Health Sciences Center, El Paso, Texas, USA 4 Department of Hematology/Oncology, Loma Linda University Health Sciences Center, Loma Linda, California, USA 5 Department of Veterinary Clinical Sciences, University of Minnesota, Saint Paul, Minnesota, USA 6 Border Biomedical Research Center, University of Texas, El Paso, Texas, USA 7 Masonic Cancer Center, University of Minnesota, Minneapolis, Minnesota, USA 8 Department of Pathology, Texas Tech University Health Sciences Center, El Paso, Texas, USA 9 Division of Biostatistics and Epidemiology, Texas Tech University Health Sciences Center, El Paso, Texas, USA 10 Department of Surgery, Texas Tech University Health Sciences Center, El Paso, Texas, USA * These authors contributed equally to this work Correspondence to: Zeina Nahleh, email: zeina.nahleh@ttuhsc.edu Brad A. Bryan, email: brad.bryan@ttuhsc.edu Keywords: beta blocker, propranolol, breast cancer, proliferation, Ki-67 Received: September 07, 2016      Accepted: December 13, 2016      Published: December 23, 2016 ABSTRACT Previous studies suggest beta-adrenergic receptor (β-AR) antagonists (β-blockers) decrease breast cancer progression, tumor metastasis, and patient mortality; however the mechanism for this is unknown. Immunohistochemical analysis of normal and malignant breast tissue revealed overexpression of β1-AR and β3-AR in breast cancer. A retrospective cross-sectional study of 404 breast cancer patients was performed to determine the effect of β-blocker usage on tumor proliferation. Our analysis revealed that non-selective β-blockers, but not selective β-blockers, reduced tumor proliferation by 66% ( p < 0.0001) in early stage breast cancer compared to non-users. We tested the efficacy of propranolol on an early stage breast cancer patient, and quantified the tumor proliferative index before and after treatment, revealing a propranolol-mediated 23% reduction ( p = 0.02) in Ki67 positive tumor cells over a three-week period. The anti-proliferative effects of β-blockers were measured in a panel of breast cancer lines, demonstrating that mammary epithelial cells were resistant to propranolol, and that most breast cancer cell lines displayed dose dependent viability decreases following treatment. Selective β-blockers alone or in combination were not as effective as propranolol at reducing breast cancer cell proliferation. Molecular analysis revealed that propranolol treatment of the SK-BR-3 breast cancer line, which showed high sensitivity to beta blockade, led to a reduction in Ki67 protein expression, decreased phosphorylation of the mitogenic signaling regulators p44/42 MAPK, p38 MAPK, JNK, and CREB, increased phosphorylation of the cell survival/apoptosis regulators AKT, p53, and GSK3β. In conclusion, use of non-selective β-blockers in patients with early stage breast cancer may lead to decreased tumor proliferation.