Question

40-year-old woman with a history of breast cancer that was successfully treated with Tamoxifen for several months. Otherwise healthy, with no other issues at this time. She is a successful business woman in a high-profile career with much stress. Married to wife of four years; relationship is rocky at times. Denies any substance use; travels frequently.

Answer 1

Tamoxifen: It is an estrogen receptor modulator drug used in the chemotherapeutic treatment both pre-menopausal and post-menopausal women with particular types of breast cancer. Tamoxifen is a substituted triphenylethylene antiestrogen used in the adjuvant therapy and chemoprevention of breast cancer. It’s a type of hormone therapy (endocrine therapy). Preliminary trials suggest that the drug tamoxifen, an anti estrogen commonly used to treat breast cancer, is useful in treating bipolar disorder.

Mechanism: After the ligand bindsto the G-Protein Coupled Receptor on the cell membrane, there is a conformational change in the GPCR which causes the activation of the G-protein. The G-alpha subunit binds to a GTP & is dissociated from the G-beta & G-gamma subunits & is translocated along the cell membrane to activate Phospholipase C. Phospholipase C dissociates PhosphoInositol - 4,5- biphosphate to DAG ( Di Acyl Glycerol) & IP3 (Inositol-1,4,5 -triphosphate). IP3 then causes the release of Ca2+ from endoplasmic reticulum. These Ca2+ ions bind to the Protein Kinase C & activate it. However, Tamoxifen inhibits this Protein Kinase C & prevents downstream signaling cascade of G-protein signaling.