Figure 4.

Gefitinib in combination with AKT/PI3K inhibitors sensitizes Basal type Triple Negative Breast Cancer (TNBC). (A) HCC-70, MDA-MB-468, and MDA-MB-231 TNBC cells treated in the presence of NRG-1β (50 ng/ml) does not significantly decrease sensitivity to gefitinib (200 nM) after 96 h. (B) Viability assay of TNBC cells as in (A) treated with the small molecule inhibitors GDC0068 (1uM), GDC0077 (1uM), gefitinib (200 nM), or a combination of the drugs +/- NRG1β (50 ng/ml) for 96h. In the HCC-70 and MDA-MB-468 cell lines, combination therapy demonstrated decreased viability compared to the MDA-MB-231 cell line which showed no significant difference in response, regardless of treatment (C) Biochemical analysis of the p/EGFR and p/HER3 showing decreased but not abolished phosphorylated proteins indicating a potent and sustained signaling in presence of NRG1β in the Basal type TNBC cells, HCC-70, and MDA-MB-231; Cells were treated for 48h at the drug concentrations shown in (B). The Claudin type MDA-MB-231 cell line showed no HER3 phosphorylation. Drug response graphs show CellTiter-Glo luminescence viability measurements at the end of the experiments compared to untreated control and analyzed using two-way analysis of variance (ANOVA)/Tukey’s multiple comparison test, *<0.05, ***P<0.001]. Experiments were performed in triplicate. Data are means ± SD].