Retinoic Acid-Related Orphan Receptor alpha 1 (RORα1) Induction of AKR1C3 Promotes MCF-7 Breast Cancer Cell Proliferation and Tamoxifen-Resistance which is Suppressed by Melatonin
The retinoic acid-related orphan receptors alpha (RORa) are members of the steroid/thyroid nuclear receptor super-family and core components of the circadian timing system. In the present study, we continue to investigate the role of RORas in human breast cancer. Assays using the RORa response element (RORE)-tk-luciferase reporter demonstrate the functionality of the RORa1 in MCF-7 breast cancer cells and that over-expression of RORa1 stimulates MCF-7 human breast cancer cell proliferation.
... proliferation. Genomic analysis revealed that RORα1 over-expression regulated the transcription of numerous genes in MCF-7 breast cancer cells including increasing the expression of connexin 43 (CX43), aldo-keto reductases 1C1 (AKR1C1), and AKR1C3. Furthermore, administration of the pineal hormone melatonin represses RORa1 induction of CX43, AKR1C1, and AKR1C3 in MCF-7 cells. AKR1C3 has been reported to impact in intra-tumoral production of androgens and estrogens and thus, might promote Tamoxifen resistance in breast cancer. Over-expression of RORa1 and subsequently AKR1C3 does promote Tamoxifen resistance, which can be inhibited by melatonin administration.