ODP433 An increased in AIPB expression in Triple Negative (ER-/PR-/Her2-) Breast Tumors reduces estradiol synthesis

Abstract

Abstract Aromatase (estrogen synthetase) is a p450 family of enzymes that catalyzes testosterone to estradiol in presence of a cofactor NADPH. Aromatase is central for its role in reproduction and reproductive diseases for catalyzing the conversion of testosterone to estradiol by aromatase. Since aromatase is responsible for the synthesis of estrogens, it is essentially a rate limiting enzyme. Aromatase is expressed mainly in the ovaries of premenopausal women and placentas of pregnant women. Therapeutic approaches for controlling breast cancer proliferation include reducing estrogen by interfering with its production via ovarian ablation in premenopausal women and/or use of aromatase inhibitors or inactivators in postmenopausal women. The use of aromatase inhibitors can lead to rapid drug resistance and refractory disease. In triple negative breast cancers (TNBC) aromatase expression remains undetectable. Therefore, treatment of TNBC remains a challenge to the patients resulting in premature and very early death. Our laboratory is investigating the role of Aromatase Interacting Partner in Breast (AIPB), in TNBC cells (MDA-MB-231 cells). AIPB is a 22 kDa protein, present partially in the MAM (Mitochondria Associated-ER Membrane) but mainly in the endoplasmic reticulum associated with aromatase in the unaffected human breast tissue. The AIPB localization in the organelle was determined biochemically and visualized through scanning electron microscopy (SEM). We have cloned AIPB in a tetracycline inducible expression system (pTETOneAIPB) and created on demand expression of AIPB in MDA-MB-231 cells. In pTETOneAIPB engineered MDA-MB-231 cells addition of doxycycline resulted in a several fold increase in AIPB expression as compared to uninduced or MDA-MB-231 cells by quantitative PCR analysis. The growth rate of pTETOneAIPB is almost five-fold slower than the MBA-MB-231 cells. Interestingly estradiol synthesis was also decreased following doxycycline addition measured through radioimmuno assay (RIA). Therefore, our results suggest that restoration of AIPB expression may potentially reduce estradiol synthesis in TNBC patients and provide an additional therapeutic approached to treatment. Presentation: No date and time listed