Selective profiling of proteins in lung cancer cells from fine-needle aspirates by matrix-assisted laser desorption ionization time-of-flight mass spectrometry

Purpose: Matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF MS) has been used to analyze tumor sections and can determine tumor type, nodal involvement, and survival, and shows promise in predicting therapeutic response. Our purpose was to develop a method compatible with MALDI-TOF MS that allows selective analysis of cancer cells in mixed clinical samples such as fine-needle aspirates. Experimental Design: Lung cancer cell lines were cytocentrifuged onto metal-coated, transparent glass slides and used for optimization of fixation, staining, and RBC lysis protocols. Fine-needle aspirates from human tumors and mouse model tumors were used to provide fresh tissue samples for determining the feasibility of this method. Results: The MALDI-TOF MS compatible fixation and staining techniques provided high-resolution cellular morphology, which allowed identification and selective spotting of tumor cells. The RBC lysis step efficiently removed contaminating RBC yielding spectra nearly free from hemoglobin peaks. Protein profiles of fine-needle aspirates were found highly reproducible and similar to the profiles of the tissue from which they were obtained. Using this method, we were able to differentiate between xenograft tumors derived from two different human cell lines, A549 and H460. Conclusion: This procedure results in the production of high-quality, cancer cell-specific protein profiles. This highly reproducible technique could be applied to many other types of mixed clinical samples and has the potential to be very useful in the clinical diagnosis, classification, and, potentially, the individualized treatment of cancer patients.