An NF-κB pathway-mediated positive feedback loop amplifies Ras activity to pathological levels in mice

Area of Science:

• Oncology
• Molecular Biology
• Inflammation Research

Background:

• Ras mutations are oncogenic but not specific biomarkers.
• Elevated Ras activity, not just mutations, drives tumorigenesis.
• Mechanisms amplifying Ras activity to pathological levels are unclear.

Purpose of the Study:

• To investigate how inflammatory stimuli interact with oncogenic Ras.
• To elucidate the positive feedback mechanisms amplifying Ras activity.
• To explore potential cancer prevention strategies targeting this pathway.

Main Methods:

• Studied Ras activity and inflammatory responses in wild-type and oncogenic K-Ras expressing mice.
• Utilized genetic manipulations including deletion of inhibitor of NF-κB kinase 2 (IKK2).
• Assessed the role of Cyclooxygenase-2 (Cox-2) and lipopolysaccharide (LPS) in promoting inflammation and lesions.

Main Results:

• Inflammatory stimuli prolonged Ras signaling and induced chronic inflammation and precancerous pancreatic lesions (PanINs) in oncogenic K-Ras mice.
• These effects were dependent on NF-κB and Cox-2 activity.
• Genetic or pharmacological inhibition of IKK2 or Cox-2 disrupted the pathological outcomes.
• Constitutive activation of IKK2 or Cox-2 in oncogenic Ras-expressing mice recapitulated these findings.

Conclusions:

• Oncogenic Ras, in conjunction with inflammatory stimuli, activates an NF-κB-mediated positive feedback loop involving Cox-2.
• This feedback loop amplifies Ras activity to pathological levels, driving tumorigenesis.
• Targeting this Ras-NF-κB-Cox-2 axis offers a potential strategy for cancer prevention in susceptible populations.