Why do tamoxifen and herceptin not work against basal-like breast cancer?

This is because basal-like breast cancers, do not express estrogen receptor (ER) or progesterone receptor (PR) and lacks human epidermal growth factor receptor 2 (HER2) overexpression or amplification. Due to the absence of molecular targets, they are unlikely to respond to medications such as tamoxifen and Herceptin that target the aforementioned receptors.