Invetigating the potential of human leucocyte cell lines and primary cells for tumor prediction in colon cancer tissue by intact cell MALDI-ToF mass spectrometry

Abstract

Colorectal cancers are among the most common cancer types worldwide. It was found that the immune cell infiltration represents the best prognostic factor for patient survival. The type and location of immune cells in the tumor influence its progression. Tumor-infiltrating lymphocytes (TILs) and tumor-associated macrophages (TAMs) are important groups of immune cells present in the tumor. Not all subtypes of these groups can be identified immunohistochemically. Therefore, mass spectrometry imaging (MSI) can be used for identifying the type and location of immune cells in colon tumor sections. To locate certain cells in a tissue section, cell type specific protein peaks can be used. In this thesis, the potential of MALDI Intact Cell Mass Spectrometry (ICMS) to find such peaks was evaluated. Lymphocytic cell line Jurkat and monocytic cell line U937 were used for the development of a MALDI sample preparation method. Using unsupervised hierarchical cluster analysis and principle component analysis, both cell lines could be discriminated and via receiver operating characteristic analysis specific peaks could be identified. By utilizing the same methods for sample preparation and statistical analysis it was shown that primary human cells from healthy donors- monocytes (CD14+) and lymphocytes (CD14-) have distinct mass spectra. However, specific peaks were found only for monocytes, but not for lymphocytes opening a field for future investigation.