Abrogating Metastatic Properties of Triple-Negative Breast Cancer Cells by EGFR and PI3K Dual Inhibitors

SIMPLE SUMMARY: Triple-negative breast cancer (TNBC) is an aggressive BC that highly metastasizes to the brain, constituting a major hurdle and with poor survival after diagnosis. This strongly contributes to the lack of well-defined molecular targets, limiting effective TNBC therapeutic options. Nevertheless, TNBC has been associated with epidermal growth factor receptor (EGFR) overexpression and downstream phosphoinositide 3-kinase (PI3K) signaling activation. We hypothesized that blood–brain barrier (BBB)-permeant molecules with the predicted ability to inhibit the EGFR/PI3Kp110β pathway could be strong candidates to tackle metastatic TNBC. A screening of EGFR, PI3Kp110β, and dual inhibitors was performed to validate their efficacy in biological assays. We used TNBC cells with brain tropism to test the drugs’ effects in downstream players of the EGFR/PI3Kp110β pathway, as well as in cell death, morphology, proliferation, and migration. We found that two dual inhibitors presented the strongest anti-tumor effects, pointing to their usefulness in abrogating TNBC cells’ tumorigenic properties. ABSTRACT: Triple-negative breast cancer (TNBC) is a devastating BC subtype. Its aggressiveness, allied to the lack of well-defined molecular targets, usually culminates in the appearance of metastases that account for poor prognosis, particularly when they develop in the brain. Nevertheless, TNBC has been associated with epidermal growth factor receptor (EGFR) overexpression, leading to downstream phosphoinositide 3-kinase (PI3K) signaling activation. We aimed to unravel novel drug candidates for TNBC treatment based on EGFR and/or PI3K inhibition. Using a highly metastatic TNBC cell line with brain tropism (MDA-MB-231 Br4) and a library of 27 drug candidates in silico predicted to inhibit EGFR, PI3K, or EGFR plus PI3K, and to cross the blood–brain barrier, we evaluated the effects on cell viability. The half maximal inhibitory concentration (IC(50)) of the most cytotoxic ones was established, and cell cycle and death, as well as migration and EGFR pathway intervenient, were further evaluated. Two dual inhibitors emerged as the most promising drugs, with the ability to modulate cell cycle, death, migration and proliferation, morphology, and PI3K/AKT cascade players such as myocyte enhancer factor 2C (MEF2C) and forkhead box P1 (FOXP1). This work revealed EGFR/PI3K dual inhibitors as strong candidates to tackle brain metastatic TNBC cells.