PIK3CD and breast cancer: A number of preclinical studies indicated that inhibition of PI3K/AKT/mTOR pathway can sensitize different types of cancer cells, including non-small cell lung cancer, breast cancer, nasopharyngeal carcinoma, oral squamous, and head and neck cancer, to radiotherapy (Yu et al., 2017; Chen et al., 2020b; Chen et al., 2020c; Glorieux et al., 2020; Schötz et al., 2020; Wanigasooriya et al., 2020).