Echinomycin (Quinomycin A) is an antitumor antibiotic secondary metabolite isolated from Streptomyces, a quinoxaline antibiotic, a DNA doubly intercalating peptide, and inhibits hypoxia-inducible factor-1 (HIF-1) DNA binding activity. Echinomycin has potential anticancer activity and can be used to study triple-negative breast cancer.

U251-HRE:∼1.2 nmol/L (EC50), CSCs:29.4 pM

Electrophoretic mobility shift assay experiments showed that Echinomycin inhibited binding of HIF-1α and HIF-1β proteins to a HRE sequence but not binding of the corresponding proteins to activator protein-1 (AP-1) or nuclear factor-κB (NF-κB) consensus sequences.
Echinomycin very potently inhibited hypoxic induction of luciferase expression in U251-HRE in a dose-dependent fashion with an EC50 of ∼1.2 nmol/L. [1]
Echinomycin abrogated the CSCs with an IC50 of 29.4 pM. Echinomycin selectively induces apoptosis of CSCs. The cultured lymphoma cells were treated with 20 pM echinomycin or vehicle in medium for 16 hr. [2]

Cultured lymphoma cells were injected i.p. into immune-competent B10.BR mice or BALB Rag2−/−/c mice. Fourteen days later, 10 μg/Kg/injection of echinomycin was injected at a 2-day interval for a total of five times. The untreated mice survived only 6–10 weeks, while all treated mice lived until euthanasia at 134 or 252 days after tumor-cell injection, with no sign of tumor development upon necropsy. [2]