Estrogens occurring naturally in the body are metabolized to catecholestrogens (2- and 4-hydroxyestradiol) by the cytochrome P450 enzymes. 2-Hydroxy catecholestrogens are further metabolized by catechol-O-methyltransferase to 2-methoxyestradiol, which is known to be protective against tumor formation. 2-Methoxyestradiol exhibits potent apoptotic activity against rapidly growing tumor cells. It also possesses antiangiogenic activity through a direct apoptotic effect on endothelial cells. Other molecular mechanisms, including microtubule stabilization by inhibition of the colchicine-binding site, have been reported. The exact mechanism of action of 2-methoxyestradiol is still unclear, but it has been shown to be effective in preventing tumor growth in a variety of cell lines. 2-Methoxyestradiol also possesses cardioprotective activity by inhibiting vascular smooth muscle cell growth in arteries. It has a lower binding affinity for estrogen receptor alpha compared with that of estradiol, and its affinity for estrogen receptor beta is even lower than that of estrogen receptor alpha, thus it has minimal estrogenic activity. 2-Methoxyestradiol is distinct because of its inability to engage estrogen receptors as an agonist, and its unique antiproliferative and apoptotic activities are mediated independently of estrogen receptors alpha and beta. A phase I clinical trial of 2-methoxyestradiol 200, 400, 600, 800, and 1,000 mg/day in 15 patients with breast cancer showed significant reduction in bone pain and analgesic intake in some patients, with no significant adverse effects. Another phase I study of 2-methoxyestradiol 200-1,000 mg/day in combination with docetaxel 35 mg/m2/week for 4-6 weeks performed in 15 patients with advanced refractory metastatic breast cancer showed no serious drug-related adverse effects. A phase II randomized, double-blind trial of 2-methoxyestradiol 400 and 1,200 mg/day in 33 patients with hormone-refractory prostate cancer showed that it was well tolerated and showed prostate specific antigen stabilizations and declines. We have started a phase I clinical trial to explore dosages greater than 1,000 mg/day.

The epigenome is defined by DNA methylation patterns and the associated post-translational modifications of histones. This histone code determines the expression status of individual genes dependent upon their localization on the chromatin. The histone deacetylases (HDACs) play a major role in keeping the balance between the acetylated and deacetylated states of chromatin and eventually regulate gene expression. Recent developments in understanding the cancer cell cycle, specifically the interplay with chromatin control, are providing opportunities for developing mechanism-based therapeutic drugs. Inhibitors of HDACs are under considerable exploration, in part because of their potential roles in reversing the silenced genes in transformed tumor cells by modulating transcriptional processes. This review is an effort to summarize the nonclinical and clinical status of HDAC inhibitors currently under development in anticancer therapy.In eukaryotic cells, DNA has been conserved over evolution in a condensed and densely packed higher order structure called chromatin. Chromatin, present in the interphase nucleus, is composed of regular repeating units of nucleosomes, which represent the principal protein-nucleic acid relationship. The major components of chromatin are nucleic acids (DNA and RNA), which are negatively charged; associated proteins, including histones, that are positively charged at neutral pH; and nonhistone chromosomal proteins, which are acidic at neutral pH. Within the nucleus, chromatin can exists in two different forms: heterochromatin, which is highly compact and transcriptionally inactive, or euchromatin, which is loosely packed and accessible to RNA polymerases for involvement in transcriptional processes and gene expression. A nucleosome is a complex of 146 nucleotide base pairs of DNA wrapped around the core histone octamer that helps organize chromatin. The histone octamer is composed of two copies each of H2A, H2B, H3, and H4 proteins, which are very basic, mainly because of positively charged amino-terminal side chains rich in the amino acid lysine. Post-translational and other changes in chromatin, such as acetylation/deacetylation at lysine residues, methylation at lysine or arginine residues, phosphorylation at serine resides, ubiquitylation at lysines, and/or ADP ribosylation, are mediated by chemical modification of various sites on N-terminal tail .The structural modification of histones is regulated mainly by acetylation/deacetylation of the N-terminal tail and is crucial in modulating gene expression, because it affects the interaction of DNA with transcription-regulatory non-nucleoArticle, publication date, and citation information can be found at

Angiogenesis is crucial for development and metastasis of tumors,