15P - The regulation of pregnenolone in breast cancer

Background

Estrogen plays a pivotal role in the development of breast cancer. Previous studies have shown that estrogen enhances cell proliferation via regulating its target gene expression in human breast cancer MCF-7 cell line. Although the effect of estrogen on the carcinogenesis in breast, the effects of pregnenolone (PG), an inactive precursor of estrogen, on MCF-7 cells or breast cancer have not been adequately explored. PG is a precursor in the biosynthesis of most of the steroid hormones containing estrogen. This investigation aimed to evaluate the effects of PG on cell proliferation and cell cycle-related protein expression.

Methods

We used Michigan Cancer Foundation-7 cell (MCF-7 cell) line, to assess the impact of PG on the carcinogenicity of breast cancer cells. We examined cell proliferation, survival rate and mobility using Bromodeoxyuridine, MTT assay and western blot. To reveal the mechanism of PG, we performed RNA seq after treatment of PG in the MCF-7 cells and transfection using siRNA of estrogen receptor and ERE luciferase vector.

Results

PG increased cell proliferation, viability, mobility, and the expression of proteins associated with the cell cycle, such as CDK2, CDK4, and Cyclin D1. We elucidated the carcinogenic mechanism of PG. Through protein-ligand docking energy analysis, we measured the affinity of PG for estrogen receptors (ERs), showing a high affinity for ERα similar to E2. When treated with cyanine 5-conjugated with PG (Cy5-PG), we observed that PG entered the cells within five minutes. Then, activated ERα entered the nucleus, bound to ERE-promoters, and significantly increased the expression of target genes associated with cell proliferation and carcinogenicity, such as pS2 and Ki-67. These results indicate that PG increases the expression of target genes through ERα and thereby affects the carcinogenicity of breast cancer cells.

Conclusions

Our results demonstrate that PG can have a significant impact on the proliferation and migration of ERα-positive breast cancer cells through ERα. Furthermore, the sustained high concentration of PG, unlike E2 which rapidly decreases after menopause, is strongly associated with the development of breast cancer. Therefore, PG has the potential to serve as a risk factor and diagnostic biomarker for breast cancer.

Clinical trial identification

Editorial acknowledgement

Legal entity responsible for the study

The authors.

Funding

Has not received any funding.

Disclosure

All authors have declared no conflicts of interest.