Enzymatic O-methylation of catechol estrogens in red blood cells: differences in animal species and strains

Recent Advances in chemistry and pharmacology of 2-methoxyestradiol: An anticancer investigational drug

2-Methoxyestradiol (2ME2), an estrogen hormone metabolite is a potential cancer chemotherapeutic agent. Presently, it is an investigational drug under various phases of clinical trials alone or in combination therapy. Its anticancer activity has been attributed to its antitubulin, antiangiogenic, pro-apoptotic and ROS induction properties. This anticancer drug candidate has been explored extensively in last twenty years for its detailed chemistry and pharmacology. Present review is an update of its chemistry and biological activity. It also extends an assessment of potential of 2ME2 and its analogues as possible anticancer drug in future.

2-Methoxyestradiol, an Endogenous Mammalian Metabolite, Radiosensitizes Colon Carcinoma Cells through c-Jun NH2-Terminal Kinase Activation

PURPOSE

2-Methoxyestradiol (2ME), an estrogen metabolite, induces apoptosis in various cell types. We investigated whether 2ME pretreatment can radiosensitize colon adenocarcinoma cells.

EXPERIMENTAL DESIGN

Radiosensitizing effects of 2ME were evaluated by cell death, clonogenic assay, nuclear fragmentation, and tumor progression of xenografts. Ionizing radiation-induced DNA damage was evaluated by histone H2AX phosphorylation and its foci. The c-Jun NH2-terminal kinase (JNK) activation was evaluated by anti-phosphorylated JNK antibody and inhibited by the JNK-specific inhibitor SP600125 or dominant-negative SEK1 expression.

RESULTS

Clonogenic assays revealed that 2ME, but not estradiol, radiosensitized three colon carcinoma cells, DLD-1, HCT-8, and HCT-15, and strongly suppressed tumor progression of DLD-1 xenografts. Gene transfer-mediated Bcl-xL overexpression largely abolished both augmented apoptosis and reduced survival fractions. Pretreatment with 2ME enhanced H2AX phosphorylation, its foci, and phosphorylation of ATM kinase and delayed re-entry of cell cycle progression after ionizing radiation. Augmentation of both radiosensitivity and H2AX phosphorylation was substantially reduced by SP600125 or overexpression of a dominant-negative mutant SEK1.

CONCLUSION

2ME radiosensitized colon carcinoma cells through enhanced DNA damage via JNK activation, thereby representing a novel radiosensitizing therapy against colon cancer.

Enzymic and chemical O-methylation of a 4-hydroxyestrone N-acetylcysteine conjugate

4-Hydroxyestrone N-acetylcysteine conjugate (4-OHE1-2SR) is considered to be an important compound for monitoring the in vivo formation of catechol estrogen quinones, an intermediary in estrogen carcinogenicity. This article describes the selective synthesis of isomeric monomethyl ethers of 4-OHE1-2SR utilizing the formation of a seven-membered ring lactone by dehydration with acetic anhydride. Using these authentic specimens, enzymic and chemical O-methylation were examined. Enzymic O-methylation, using a rat liver cytosolic fraction, of 4-OHE1-2SR gave its 3-methyl ether as the sole product, while preferential O-methylation of 4-hydroxyestrone (4-OHE1) at the C-4 position was confirmed under the same conditions. Methylation of 4-OHE1-2SR with diazomethane gave initially carboxylate methylation, then the corresponding 3-methyl ether almost exclusively, while methylation of 4-OHE1 also gave its 3-methyl ether preferentially. However, much more rapid formation of the 3-methyl ether was observed with 4-OHE1-2SR than with 4-OHE1 itself. These results show that the hydroxy group at the C-3 position of 4-OHE1-2SR is more reactive than that at the C-4 position, both chemically and enzymatically.

Exercise-induced changes in enzymatic O-methylation of catecholestrogens by erythrocytes of eumenorrheic women

The present study was designed to assess the effects of acute exercise and short-term intensive training on catechol-O-methyltransferase (COMT) activity. COMT inactivates catecholamines and converts primary catecholestrogens (CE) into their O-methylated form yielding the 2- (2-MeOE) and 4-methoxyestrogens (4-MeOE). Blood samples were obtained from 15 previously untrained eumenorrheic women (mean +/- SE, VO2max: 43.8 mL x kg-1 x min-1 +/- 0.6) before and after a 5-d intensive training period, at rest and during incremental exercise. COMT activity was determined in the erythrocytes (RBC-COMT) after incubation of blood lysate with primary CE. The formation of both 2- and 4-MeOE was significantly higher (P < 0.05) during the luteal (LPh) than during the follicular phase (FPh). The amount of 2-MeOE formed (FPh: 4.2 +/- 0.2%; LPh: 4.9 +/- 0.2%) was significantly greater than the produced amount of 4-MeOE (FPh: 1.4 +/- 0.1%; LPh: 1.5 +/- 0.1%) (P < 0.05). Both before and after training, incremental exercise did not significantly alter RBC-COMT activity although we observed a trend for RBC-COMT activity increasing proportionally with the exercise intensity. After a brief period of exhaustive training, during rest the formation of 2-MeOE (FPh: +16.7%, LPh: +15.7%) and 4-MeOE (FPh: +28.6%; LPh: +40%) was significantly (P < 0.05) increased. The results of the present study are consistent with earlier findings reporting increased plasma concentrations of O-methylated CE following training. It is concluded that RBC-COMT activity is increased by brief intensive training, but not by acute exercise. We speculate that an increase in COMT-catalyzed O-methylation of CE may indicate that less COMT is available to deactivate norepinephrine.