Sterigmatocystine is a precursor of aflatoxins and a mycotoxin produced by common mold strains from Aspergillus versicolor. Sterigmatocystine, a inhibitor of G1 Phase and DNA synthesis, is used to inhibit p21 activity. Sterigmatocystine has teratogenic, and carcinogenic effects in animals. In Vitro: Sterigmatocystine-induced DNA damage activates the ATM/53-dependent signaling pathway, which contributes to the induction of G2 arrest in GES-1 cells. In Vivo: Sterigmatocystine (ip; 3 mg/kg once daily for 14 days) inhibits p21WAF1/CIP1.