Together, these results suggest that EDNRB isoforms have differential potentials as biomarkers, that EDNRB-536 may be a specific biomarker for estrogen-receptor negative and triple-negative breast cancers, and that the utility of EDNRB as a potential biomarker may depend on the expression level of EDN3. The gene discussed is ESR1; the disease is triple-negative breast carcinoma.