The rs1800716 variant in CYP2D6 is associated with an increased double endometrial thickness in postmenopausal women on tamoxifen

Research progress on tamoxifen and its analogs associated with nuclear receptors

Tamoxifen, a triphenylethylene-based selective estrogen-receptor modulator, is a landmark drug for the treatment of breast cancer and is also used for treating liver cancer and osteoporosis. Structural studies of tamoxifen have led to the synthesis of more than 20 novel tamoxifen analogs as receptor modulators, including 16 ERα modulators 2-17, an ERRβ inverse agonist 19 and six ERRγ inverse agonists 20-25. This paper summarizes the research progress and structure-activity relationships of tamoxifen analogs modulating these three nuclear receptors reported in the literature, and introduces the relationship between these three nuclear receptor-mediated diseases and tamoxifen analogs to guide the research of novel tamoxifen analogs.

Hormone Therapy Effects on the Uterus

The uterus and especially the endometrium are sensitive targets for steroid sex hormones, capable to modify structure and function with promptitude and versatility in order to secure reproductive functions. Hormone therapy is used to counteract deprivation, abnormal, and deleterious functions of "natural" hormones. It is widely prescribed, being used by millions of women all over the world. It seems that most women would use at least some hormone therapy at some point of their life, as contraceptives, ovarian stimulation, replacement therapy, or hormone antitumoral therapy. The diagnosis of uterine tissue, mostly of the frequently performed endometrial biopsies taken from women undergoing hormone therapy, is often confusing and difficult to interpret due to the complexity of histologic changes. Permanently changing hormonal pharmaceutical products, regimens, dosages, as well as new concepts of therapy are challenges for both users and medical prescribers. This chapter addresses the most commonly issues arising from the gynecological pathology interpretation of hormonal therapy effects on the uterus.

Endometrial Carcinoma and its Precursors

This chapter focuses on premalignant and malignant diseases of the endometrium (lining of the uterus). Endometrial carcinoma is the most common gynecologic cancer in the United States. Women have a 1 in 40 lifetime risk of being diagnosed with endometrial cancer, the fourth most common malignancy among women. An estimated 61,880 new diagnoses of uterine cancer and 12,160 deaths from the disease occurred in 2019 in the United States (American Cancer Society, Facts & Figures, https://www.cdc.gov/cancer/uterine/statistics/index.htm , 2019).

Effects of SULT1A1 Copy Number Variation on Estrogen Concentration and Tamoxifen-Associated Adverse Drug Reactions in Premenopausal Thai Breast Cancer Patients: A Preliminary Study

Tamoxifen is a pharmacological estrogen inhibitor that binds to the estrogen receptor (ER) in breast cells. However, it shows an estrogenic effect in other organs, which causes adverse drug reactions (ADRs). The sulfotransferase 1A1 (SULT1A1) enzyme encoded by the SULT1A1 gene is involved in estrogen metabolism. Previous research has suggested that the SULT1A1 copy number is linked with the plasma estradiol (E2) concentration. Here, a total of 34 premenopausal breast cancer patients, selected from the Thai Tamoxifen (TTAM) Project, were screened for their SULT1A1 copy number, plasma E2 concentration and ADRs. The mean age was 44.3±11.1 years, and they were subtyped as ER+/ progesterone receptor (PR) + (28 patients), ER+/ PR- (5 patients) and ER-/PR- (1 patient). Three patients reported ADRs, which were irregular menstruation (2 patients) and vaginal discharge (1 patient). Most (33) patients had two SULT1A1 copies, with one patient having three copies. The median plasma E2 concentration was 1,575.6 (IQR 865.4) pg/ml. Patients with ADRs had significantly higher plasma E2 concentrations than those patients without ADRs (p = 0.014). The plasma E2 concentration was numerically higher in the patient with three SULT1A1 copies, but this lacked statistical significance.

Therapeutic options for management of endometrial hyperplasia

Endometrial hyperplasia (EH) comprises a spectrum of changes in the endometrium ranging from a slightly disordered pattern that exaggerates the alterations seen in the late proliferative phase of the menstrual cycle to irregular, hyperchromatic lesions that are similar to endometrioid adenocarcinoma. Generally, EH is caused by continuous exposure of estrogen unopposed by progesterone, polycystic ovary syndrome, tamoxifen, or hormone replacement therapy. Since it can progress, or often occur coincidentally with endometrial carcinoma, EH is of clinical importance, and the reversion of hyperplasia to normal endometrium represents the key conservative treatment for prevention of the development of adenocarcinoma. Presently, cyclic progestin or hysterectomy constitutes the major treatment option for EH without or with atypia, respectively. However, clinical trials of hormonal therapies and definitive standard treatments remain to be established for the management of EH. Moreover, therapeutic options for EH patients who wish to preserve fertility are challenging and require nonsurgical management. Therefore, future studies should focus on evaluation of new treatment strategies and novel compounds that could simultaneously target pathways involved in the pathogenesis of estradiol-induced EH. Novel therapeutic agents precisely targeting the inhibition of estrogen receptor, growth factor receptors, and signal transduction pathways are likely to constitute an optimal approach for treatment of EH.

Evaluation of endometrial thickness and bone mineral density based on CYP2D6 polymorphisms in Turkish breast cancer patients receiving tamoxifen treatment

BACKGROUND

Several previous studies have examined the effect of CYP2D6 gene polymorphism on the efficacy and metabolism of tamoxifen (Tamoxifen Teva, Nolvadex) in the treatment of breast cancer. In the present study, the metabolic profiles associated with various CYP2D6 genotypes were evaluated.

METHOD

In the present study 92 Turkish breast cancer patients with early-stage hormone receptor-positive tumors treated with adjuvant tamoxifen (20 mg) were evaluated for CYP2D6 genotype and metabolic profiles. Known side effects of tamoxifen treatment, including endometrial thickening, changes in serum lipid levels and bone density, and hepatosteatosis, were evaluated according to the CYP2D6 polymorphism.

RESULT

The distribution of metabolic characteristics in the Turkish population was as follows: 77.1% normal metabolism, 11.5% intermediate metabolism, 5.2% ultrarapid metabolism, and 2.1% poor metabolism. The CYP2D6 genotypes associated with rapid metabolism were CYP2D6 3X*1/*1 duplication (DUP) and CYP2D6 2X*1/*2, while poor metabolism was associated with the genotypes CYP2D6 *3/*4 and CYP2D6 *6/*6. There was no statistically significant relationship between metabolic characteristics and bone density or hepatosteatosis. A statistically significant difference in total cholesterol and triglycerides was detected in lipid profile analysis (p = 0.003, p = 0.02). Assessment of endometrial thickness revealed a significant association of hyperplasia and poor metabolism, and an association between atrophy and ultrarapid metabolism (p = 0.01).

CONCLUSION

Significant development of endometrial hyperplasia was identified among individuals with poor tamoxifen metabolism. As a result, tamoxifen may be a significant predictor of endometrial thickening among individuals with poor metabolic characteristics.