TET1 inhibits cell proliferation by inducing RASSF5 expression

Area of Science:

• Epigenetics
• Cancer Biology
• Molecular Oncology

Background:

• Tet methylcytosine dioxygenases (TETs) oxidize 5-methylcytosine to 5-hydroxymethylcytosine (5hmC).
• The specific role of TET1 in ovarian cancer cell proliferation and growth remains largely unexplored.

Purpose of the Study:

• To investigate the function of TET1 in ovarian cancer.
• To identify downstream targets and mechanisms through which TET1 influences ovarian cancer progression.

Main Methods:

• Ovarian cancer cell lines were utilized for ectopic expression and depletion studies of TET1.
• In vitro and in vivo functional assays assessed proliferation and colony formation.
• RNA sequencing (RNA-seq) and quantitative reverse transcription PCR (qRT-PCR) identified downstream targets.
• DNA methylation analysis of the RASSF5 promoter was performed.

Main Results:

• Ectopic TET1 expression elevated 5hmC levels, inhibited ovarian cancer cell proliferation and colony formation.
• TET1 overexpression suppressed tumor growth in vitro and in vivo, while TET1 depletion promoted it.
• Ras association domain family member 5 (RASSF5) was identified as a key downstream target, with TET1 promoting its expression via demethylation of its promoter.
• Inhibition of the CUL4-DDB1 ubiquitin ligase complex reduced 5hmC levels in ovarian cancer cells.

Conclusions:

• TET1 functions as a tumor suppressor in ovarian cancer by increasing 5hmC and upregulating RASSF5 expression.
• TET1-mediated RASSF5 upregulation inhibits ovarian cancer cell growth.
• These findings elucidate a novel mechanism in ovarian cancer development and identify TET1 as a potential therapeutic target.