Thyroid hormone suppresses cell growth by regulating CDK2 and cyclin E1 expression via Hepsin

Area of Science:

• Endocrinology
• Molecular Biology
• Oncology

Background:

• Thyroid hormone (T3) and its receptor (TR) are critical regulators of cell proliferation and cancer, particularly in hepatocellular carcinoma (HCC).
• The precise molecular mechanisms of T3/TR action in HCC development are not fully understood.
• Identifying T3/TR-regulated genes is essential for elucidating HCC progression.

Purpose of the Study:

• To identify novel target genes regulated by T3/TR in hepatocellular carcinoma (HCC).
• To investigate the role of hepsin (HPN) in T3/TR-mediated regulation of HCC cell proliferation.

Main Methods:

• Microarray profiling to identify potential T3/TR target genes.
• Quantitative reverse transcription-PCR (qRT-PCR) to validate gene expression.
• Promoter assays and chromatin immunoprecipitation (ChIP) to confirm TR binding to the HPN promoter.
• Functional studies involving ectopic HPN expression and analysis of cell cycle regulators (CDK2, cyclin E1).

Main Results:

• Hepsin (HPN) was identified as a T3/TR-upregulated gene in HCC.
• TR directly binds to the HPN promoter, activating its transcription.
• Ectopic HPN expression inhibited HCC cell proliferation.
• HPN modulates CDK2 and cyclin E1 expression, mediating T3/TR's effect on cell growth.
• Clinical HCC samples showed an inverse correlation between HPN and CDK2/cyclin E1 levels.

Conclusions:

• A novel regulatory pathway involving T3/TR, HPN, CDK2, and cyclin E1 in HCC proliferation was established.
• HPN acts as a tumor suppressor in HCC by inhibiting cell proliferation.
• This pathway represents a potential therapeutic target for liver cancer treatment.