Caspase 2-mediated tumor suppression involves survivin gene silencing.

Area of Science:

• Molecular biology
• Cancer research
• Cell death pathways

Background:

• Endogenous tumor suppression opposes aberrant cell survival.
• The molecular mechanisms underlying tumor suppression are not fully understood.
• Caspase 2, a death effector, has largely unknown functions.

Purpose of the Study:

• To elucidate the molecular mechanisms by which caspase 2 contributes to tumor suppression.
• To investigate the role of caspase 2 in regulating survivin gene transcription.
• To identify the pathway linking caspase 2 to NF-kappaB signaling and cell survival.

Main Methods:

• Investigated the effect of caspase 2 on survivin gene expression.
• Analyzed the interaction between caspase 2 and RIP1.
• Assessed the impact of RIP1 cleavage on NF-kappaB target genes.
• Evaluated tumor suppression in vivo.

Main Results:

• Caspase 2 represses survivin gene transcription.
• Caspase 2 cleaves the NF-kappaB activator RIP1.
• Loss of RIP1 abolishes NF-kappaB target gene transcription, including survivin.
• This leads to deregulated mitotic transitions, enhanced apoptosis, and suppressed tumorigenicity in vivo.

Conclusions:

• Caspase 2 acts as an endogenous inhibitor of NF-kappaB-dependent cell survival.
• The caspase 2-RIP1-NF-kappaB pathway is a novel mechanism of tumor suppression.
• This pathway may contribute to human tumor suppression.