ERBB2 and breast cancer: Taking into account that quercetin is active against breast cancer cells [13,14,15] and that glucose deprivation potentiates the antiproliferative action of some anticancer drugs (such as paclitaxel and doxorubicin) in breast cancer cells [21], in the present study, we tested a combination of these two effects on six phenotypically different breast cancer cell lines, namely ER-positive MCF-7, HER2-positive SK-BR-3, and four triple-negative (TNBC) MDA-MB-231, MDA-MB-468, BT-20, and Hs 578T cells.