Evidence of β-blockers drug repurposing for the treatment of triple negative breast cancer: A systematic review

Triple negative breast cancer (TNBC) is a particularly aggressive subtype of breast cancer (BC) for which limited therapeutic options are available. Recently, β-blockers (BBs) have been suggested to have favorable effects on the treatment of BC. The aim of this systematic review was to collect evidence from preclinical and clinical studies concerning the scientific evidence for the repurposing of BBs in TNBC treatment. PubMed database was searched to retrieve studies of interest published up to 30/01/2018. All preclinical studies using TNBC in vitro and in vivo models and assessing the effect of any molecule with sympatholytic or sympathomimetic activity on adrenergic receptors were included. Clinical studies concerning BB were considered eligible. The Newcastle-Ottawa scale was used for the quality assessment of clinical studies. A total of 614 study references were retrieved. Forty-six preclinical studies were included. In in vitro studies, propranolol, a non-selective BBs, significantly decreased proliferation, migration and invasion of TNBC cells. Consistently, in in vivo studies, propranolol inhibited metastasis, angiogenesis and tumor growth. Clinical studies, reporting evidence from a total of four distinct retrospective observational cohort studies, showed a beneficial effect of BBs in TNBC treatment. The overall quality of the clinical evidence collected was low. Preclinical evidence collected in this systematic review are in line with the results reported in the clinical studies retrieved, pointing towards a beneficial effect of BB in the treatment of TNBC. However, given the overall low quality of available evidence, no definite conclusion may be drawn.