DLD was the intersection gene of CRGs related to ER+ BC prognosis (DLD, DBT, DLAT, ATP7A), CRGs differentially expressed between LCC9 and MCF-7 cell lines (SLC31A1, DLST, ATP7B, DLD), and hub genes from the cuproptosis-related PPI network (DLD, LIPT1, DLST, GCSH). The gene discussed is DLST; the disease is breast cancer.