Uncovering Tumor-Stroma Inter-relationships Using MALDI Mass Spectrometry Imaging

Area of Science:

• Oncology
• Proteomics
• Biochemistry

Background:

• Tumorigenesis involves complex interactions between cancer cells and the tumor microenvironment (stroma).
• Rho-associated protein kinase (ROCK) plays a role in mammary tumor progression by influencing stromal remodeling.

Purpose of the Study:

• To investigate the proteomic changes in the tumor stroma associated with ROCK activation in a mouse model of breast cancer.
• To identify key proteins involved in tumor-stroma interactions and their prognostic significance in human breast cancer.

Main Methods:

• Utilized a conditional ROCK activation mouse model for mammary tumorigenesis.
• Employed peptide matrix-assisted laser desorption/ionization mass spectrometry imaging (MALDI-MSI) for spatial proteomic quantification.
• Validated protein expression using liquid chromatography tandem mass spectrometry and quantitative immunofluorescence.
• Analyzed human breast cancer genomic data sets to correlate protein expression with patient outcomes.

Main Results:

• Identified and validated upregulation of collagen I, α-SMA, Rab14, and tubulin-β4 in ROCK-activated tumors.
• Collagen I and α-SMA were predominantly localized in the stroma, while Rab14 and tubulin-β4 were in tumor cells.
• High expression of COL1A and ACTA2 (encoding collagen I and α-SMA) correlated with poorer survival in estrogen receptor-negative breast cancer patients.
• Conditioned media from ROCK-activated tumor cells induced collagen I and α-SMA production in cancer-associated fibroblasts (CAFs).

Conclusions:

• ROCK activation drives tumor progression by altering the tumor stroma, particularly through collagen I and α-SMA production by CAFs.
• MALDI-MSI is a powerful tool for assessing tumor-stroma interactions and identifying prognostic biomarkers.
• Collagen I and α-SMA are potential prognostic factors for breast cancer progression.