Calcitriol and TO-901317 interact in human prostate cancer LNCaP cells

Area of Science:

• Molecular Endocrinology
• Prostate Cancer Biology
• Nuclear Receptor Signaling

Background:

• Vitamin D receptor (VDR) and liver X receptor (LXR) are key nuclear receptors regulating gene expression.
• VDR and LXR signaling pathways are implicated in prostate cancer cell proliferation.
• ATP-binding cassette transporter A1 (ABCA1) is an LXR target gene involved in LNCaP cell proliferation and is modulated by androgens.

Purpose of the Study:

• To investigate the interaction between calcitriol (active Vitamin D metabolite) and LXR signaling in prostate cancer cells.
• To determine the effect of calcitriol on ABCA1 expression and its role in LNCaP cell growth.
• To explore the potential interplay between VDR, LXR, and androgen pathways in prostate cancer.

Main Methods:

• Quantitative real-time PCR to measure mRNA expression of VDR, LXR alpha/beta, ABCA1, ABCG1, and CYP24.
• Treatment of LNCaP cells with calcitriol, LXR agonist (TO-901317), and 5 alpha-dihydrotestosterone (DHT).
• Cell growth assays using calcitriol, DHT, and ABCA1 blocker (glybenclamide).

Main Results:

• Calcitriol inhibited both basal and TO-901317-induced ABCA1 mRNA expression in an androgen-independent manner.
• Calcitriol did not affect mRNA levels of ABCG1, LXR alpha, or LXR beta.
• TO-901317 upregulated CYP24 mRNA and slightly inhibited VDR mRNA expression.
• Co-treatment with calcitriol or DHT and an ABCA1 blocker significantly decreased LNCaP cell growth compared to individual treatments.

Conclusions:

• Calcitriol's inhibition of ABCA1 may contribute to its effect on LNCaP cell growth, similar to DHT.
• There is a potential interaction between calcitriol and TO-901317 in LNCaP cells.
• These findings suggest a role for Vitamin D signaling in regulating prostate cancer cell growth via ABCA1 modulation.