Tamoxifen

Tamoxifen (TAM) an antimicrobial agent is also a selective estrogen response modifier (SERM) that is used to prevent and treat breast cancer. It was first introduced by AstraZeneca as effective therapeutic and preventive agent against estrogen-positive breast cancer. As an antibiotic, TAM has shown a direct inhibitory action on the growth of Staphylococcus aureus, methicillin-resistant S. aureus (MRSA) strains, and M. tuberculosis.1 It is metabolized to active metabolites 4-hydroxytamoxifen (4-OHT) and endoxifen by cytochrome P450 isoforms CYP2D6 and CYP3A4. TAM is also a protein kinase C inhibitor and an anti-angiogenetic factor.

Contribution of metabolic effects of TAM in increasing drug resistance was studied in MCF-7 and MCF7-TAM cell lines. 4-hydroxytamoxifen was used to examine calcium influx in human-induced pluripotent stem cell-derived cardiomyocytes (iPSC-CMs) modeled on Duchenne Muscular Dystrophy (DMD).

Active metabolites of TAM act as estrogen antagonists inmammary glands and block VEGF production in breast cancer cells. TAM is known toinhibit mitochondrial function, causing increased glycolysis and lactateproduction. 4-hydroxytamoxifen treatment of iPSC-CMs increased cellsurvival, decreased beating rate and increased beating velocity.

As an antibiotic, TAM increases membrane permeabilityand is active against Gram-positive and Gram- negative bacterial strains. It actsas both bactericidal and bacteriostatic agent.

Estrogen antagonist in mammary gland. Blocks estradiol-stimulated VEGF production in breast tumor cells. Protein kinase C inhibitor.

Protein kinase C inhibitor. Induces apoptosis in human malignant glioma cell lines. Tamoxifen and its metabolite 4-hydroxytamoxifen are selective estrogen response modifiers (SERMs) that act as estrogen antagonists in mammary gland. Blocks estradiol-stimulated VEGF production in breast tumor cells.

Tamoxifen is soluble in chloroform at 50 mg/ml and yields a clear, colorless to faint yellow solution. Stock solutions of tamoxifen can also be prepared in DMSO at 10 mM and are stable when stored at -20° C in the dark. It is also soluble in methanol, ethanol, 2-propanol and propylene glycol. It is practically insoluble in water (solubility is <0.01%, 20° C). Solutions are sensitive to UV light.