Cholest-4-en-3-one attenuates TGF-β responsiveness by inducing TGF-β receptors degradation in Mv1Lu cells and colorectal adenocarcinoma cells

Abstract

Purpose: The transforming growth factor-beta (TGF-β) pathway is an important in the initiation and progression of cancer. Due to a strong association between an elevated colorectal cancer risk and increase fecal excretion of cholest-4-en-3-one, we aim to determine the effects of cholest-4-en-3-one on TGF-β signaling in the mink lung epithelial cells (Mv1Lu) and colorectal cancer cells (HT29) in vitro.

Methods: The inhibitory effects of cholest-4-en-3-one on TGF-β-induced Smad signaling, cell growth inhibition, and the subcellular localization of TGF-β receptors were investigated in epithelial cells using a Western blot analysis, luciferase reporter assays, DNA synthesis assay, confocal microscopy, and subcellular fractionation.

Results: Cholest-4-en-3-one attenuated TGF-β signaling in Mv1Lu cells and HT29 cells, as judged by a TGF-β-specific reporter gene assay of plasminogen activator inhibitor-1 (PAI-1), Smad2/3 phosphorylation and nuclear translocation. We also discovered that cholest-4-en-3-one suppresses TGF-β responsiveness by increasing lipid raft and/or caveolae accumulation of TGF-β receptors and facilitating rapid degradation of TGF-β and thus suppressing TGF-β-induced signaling.

Conclusions: Our results suggest that cholest-4-en-3-one inhibits TGF-β signaling may be due, in part to the translocation of TGF-β receptor from non-lipid raft to lipid raft microdomain in plasma membranes. Our findings also implicate that cholest-4-en-3-one may be further explored for its potential role in colorectal cancer correlate to TGF-β deficiency.

Keywords:

• Cholest-4-en-3-one
• colorectal cancer
• lipid raft
• TGF-beta

Acknowledgements

The authors thank Daniel B. Rafkin for providing Mv1Lu cells expressing the PAI-1 promoter-driven luciferase, Dr. Jung San Huang for critical review of the manuscript.

Disclosure statement

The authors declare that they have no competing interests.

Funding

This work is supported by the Ministry of Science and Technology of Taiwan (101-2320-B-110-003, 102-2320-B-110-007, 103-2314-B-037-064, and 103-2320-B-037-014), Kaohsiung Medical University “Aim for the Top Universities Grant, Grant nos. KMU-TP104G00, KMU-TP104G03, KMU-TP104G04”, and NSYSU-KMU Joint Research Project (NSYSUKMU104-I004).