MON-139 Effect of Pyrvinium Pamoate on Estradiol Synthesis Stably Expressing AIPB in Triple-Negative Breast Cancer Cells (Er-/Pr-/Her2-)

Abstract Disclosure: A.P. Jackson: None. H.S. Bose: None. In the United States a large number of women die due to breast cancer mostly because of environmental factors and genetic predispositions which cannot be avoided due to varying social issues. Breast cancer is usually hormonally regulated where receptors like Estrogen (Er+), Progesterone (Pr+), and Human Epidermal Growth Factor Receptor (Her2-) expression are associated with tumorigenesis. Triple-negative breast cancer (TNBC, Er-/Pr-/Her2-) minimally expresses these receptors or remains absent in these patients resulting in high mortality. TNBC patients are usually ineffective against chemotherapies. We identified and cloned a cDNA coding for a 22-kDa protein expressing in unaffected and affected breast tissue, Aromatase Interacting Partner in Breast (AIPB). Next, we subcloned AIPB in a vector under the control of Tet promoter and developed a stable MDA-MB-231-AIPB cells to have a uniform expression upon induction with tetracycline. Antihelminth drug Pyrvinium pamoate (PvR) is used to reduce various cancers including TNBC and its interaction with AIPB are of interest. AIPB expression is maximal in TNBC and minimal in unaffected breast tissue. We hypothesize that AIPB expression is directly proportional to Estradiol synthesis. Therefore, following induction of TNBC MDA-MB-231 stable cells with doxycycline, AIPB should decrease in Estradiol synthesis with a reduction in AIPB expression. We incubated these stable cells with and without doxycycline with 50,000-fold difference in concentrations of PvR (1.0 ng to 50,000 ng) for 48 hours and determined its effects by measuring a change in Estradiol synthesis by radioimmunoassay (RIA). We also determined AIPB expression by Immunoblotting with a cholesterol trafficker (CT) antibody, because 42 amino acids of AIPB have amino acid identity with the CT protein. We observed a decrease in Estradiol synthesis when the cells were induced with increasing concentrations of PvR in the presence of Doxycycline. Furthermore, we observed the lowest expression of Estradiol after induction with 10.0 microgram of PvR. Immunoblotting of the PvR induced cells in presence of doxycycline showed increased AIPB expression from 1.0 ng up to 20.0 microgram, followed by decrease in expression. We conclude AIPB expression and Estradiol synthesis is directly related in TNBC and AIPB is possibly a key role of aromatase independent Estradiol synthesis. Presentation: Monday, July 14, 2025