In patients, high versus low HSP90‐dependent four gene signature score (AHR, DDA1, UBE4B, and GPATCH8) in brain metastatic tumors associate with worse patient prognosis and aggressive clinical disease (Figs 6G and EV4E–H) in an extended cohort (GSE184869) of a previously published dataset of breast cancer patients (Varešlija et al, 2019) and independently of the cancer subtype (Fig EV4I and J). This evidence concerns the gene HSP90AA1 and breast cancer.