The physiological estrogen metabolite 2-methoxyestradiol reduces tumor growth and induces apoptosis in human solid tumors

2-Methoxyestradiol (2-ME) is a physiological metabolite of estrogen, which is excreted with the urine. In contrast to most estrogens, tumor growth-inh ibiting effects were observed. Further studies have revealed that it may be an effective anticancer compound for many tumor types. Several different m echanisms have been attributed to 2-ME. Besides a strong antiangiogenic eff ect on endothelial cells and tumors, there is a tubulin-inhibiting mechanis m, causing cells to arrest in the G2/M phase of the cell cycle. In other tu mors, p53-dependent and p53-independent mechanisms with induction of apopto sis have been shown. The number of different tumors examined for a growth-i nhibiting effect is increasing, and new mechanisms are continuously describ ed. In vivo studies in mice, rats, and dogs show no or very little toxicity , even at high doses. Here, we discuss the antitumor activity and their mec hanisms. 2-ME appears to be a new anti-tumor compound with strong potential for clinical application.