Induction of tumor apoptosis through a circular RNA enhancing Foxo3 activity

Area of Science:

• Oncology
• Molecular Biology
• Genetics

Background:

• Circular RNAs (circRNAs) are a novel class of non-coding RNAs with largely unknown functions.
• While some circRNAs act as miRNA sponges, their roles in cancer biology are under investigation.

Purpose of the Study:

• To investigate the role of circ-Foxo3 in cancer development and apoptosis.
• To elucidate the molecular mechanism by which circ-Foxo3 influences protein stability and cell fate.

Main Methods:

• Analysis of circ-Foxo3 expression in patient tumor samples and cancer cell lines.
• Manipulation of endogenous and ectopic circ-Foxo3 levels to assess effects on cell viability and apoptosis.
• Investigation of circ-Foxo3 interactions with Foxo3 and p53 proteins and their regulators (e.g., MDM2).

Main Results:

• Circ-Foxo3 expression is significantly increased during cancer cell apoptosis and minimally expressed in tumors.
• Silencing circ-Foxo3 enhances cancer cell viability, while its ectopic expression induces apoptosis and inhibits tumor xenograft growth.
• Circ-Foxo3 stabilizes Foxo3 protein by preventing MDM2-mediated degradation, leading to increased PUMA expression and apoptosis.
• Circ-Foxo3 promotes p53 degradation by facilitating MDM2-induced ubiquitination.

Conclusions:

• Circ-Foxo3 acts as a tumor suppressor by stabilizing Foxo3 protein and inducing apoptosis.
• The findings highlight circ-Foxo3 as a potential therapeutic target for cancer treatment.
• Circ-Foxo3's distinct regulatory effects on Foxo3 and p53 protein levels offer insights into its complex role in cancer progression.