Comparative Analysis of Tumours, Their Metastases and Derived Primary Cell Lines by Rapid Evaporative and Desorption Electrospray Ionization Mass Spectrometry

Importance of the Topic

The high mortality associated with breast cancer metastasis drives the need for robust chemical imaging methods to profile primary tumors, their metastases and derived cell lines.

Objectives and Study Overview

• Assess the chemical similarity between primary breast tumors and their metastases in tissue sections.
• Compare derived immortalized cell lines to their originating tumors and metastases.
• Identify characteristic lipid biomarkers and sensitivity profiles.
• Benchmark Laser-Assisted Rapid Evaporative Ionization Mass Spectrometry (LA-REIMS) against Desorption Electrospray Ionization (DESI).

Methodology and Used Instrumentation

• Sample preparation: spontaneous breast tumors and matched lung or skin metastases were sectioned; immortalized cell lines were established from the same tumors.
• Imaging techniques: DESI and LA-REIMS performed at 50 µm spatial resolution on a Xevo G2-XS TOF mass spectrometer (Waters) with dedicated DESI and REIMS sources.
• Acquisition settings: negative ion mode, m/z range 50–1200, data subjected to PCA/LDA for tissue and cell discrimination.

Main Results and Discussion

• Strong correlation observed between primary tumors and corresponding metastases based on PCA distances (0.6–1.5), indicating conserved chemical fingerprints.
• DESI and LA-REIMS both distinguished healthy, tumorous and necrotic regions in tissues with consistent lipid markers (PE, PS, PA species).
• Cell lines were clearly separable by origin and analytical platform, though they exhibited major differences from intact tissue profiles.
• Key lipid species (e.g., PE(P-38:4), CerP(36:2), PA(34:2)) were found in both cells and tissues, supporting targeted biomarker discovery.

Benefits and Practical Applications

These complementary imaging modalities enable rapid molecular profiling of tumors and metastases, offering potential for intraoperative guidance tools (e.g., iKnife) and quality control of cell line–based experiments. Identified lipid signatures may inform therapeutic strategies and dietary intervention studies.

Future Trends and Potential Applications

• Expansion of spectral databases to support diagnostic decision-making and real-time tissue classification.
• Integration of imaging mass spectrometry with in vivo models for therapeutic assessment.
• Development of standardized protocols for dietary modulation experiments using characterized cell lines.
• Advancement of orthogonal analytical platforms for comprehensive tumor phenotyping.

Conclusion

DESI and LA-REIMS imaging provide rich, complementary molecular profiles that reliably distinguish primary breast tumors from metastases and healthy tissue. While cell lines differ from tissue, they retain key lipid features justifying their use in further experimental studies and potential clinical applications.