Stromal-MDM2 Promotes Lung Cancer Cell Invasion through Tumor-Host Feedback Signaling

Area of Science:

• Oncology
• Molecular Biology
• Cancer Research

Background:

• Tumor-host interactions are critical in cancer progression.
• Cancer cells can interfere with signaling pathways in stromal cells.
• Previous work showed tumor cells suppress p53 activation in stroma.

Purpose of the Study:

• To investigate how lung cancer cells influence signaling within the tumor stroma.
• To identify specific molecular mechanisms involved in tumor-stroma communication.
• To explore the role of stromal-MDM2 in cancer cell invasion and growth.

Main Methods:

• Primary cancer-associated fibroblasts were cultured from human lung tumors.
• Conditioned medium (CM) and co-culture systems were used with lung cancer cell lines and ex vivo lung cancers.
• Invasiveness was assessed via transwell assays, and in vivo tumor growth was evaluated in Athymic nude mice.

Main Results:

• CM from various cancer cells rapidly increased stromal-MDM2 protein levels, unlike CM from normal cells.
• MDM2 induction was translation-dependent, reliant on mTORC1 signaling, and linked to AKT and p70 S6 Kinase activation.
• Fibroblast AKT or MDM2 knockdown reduced cancer cell invasion; MDM2 overexpression enhanced invasion and tumor growth in mice.

Conclusions:

• Lung cancer cells induce stromal-MDM2 via AKT/mTORC1 signaling, promoting cancer cell invasion and growth.
• Stromal-MDM2 is part of a p53-independent feedback loop in tumor-host interactions.
• This newly identified tumor-stroma signaling loop represents a potential therapeutic target for lung cancer.