Imaging mass spectrometry: principles and potentials

Direct tissue profiling and imaging mass spectrometry (MS) allow for detailed mapping of the complex protein pattern across a tissue sample. Utilization of these tools provides spatial information across a tissue section for target protein expression and can be used to correlate changes in expression levels with specific disease states or drug response. Protein patterns can be directly correlated to known histological regions within the tissue, allowing for the direct monitoring of proteins specific for morphological regions within a tissue sample. Profiling and imaging MS have been used to characterize multiple tissues, including human gliomas and lung cancers, as well as tumor response to specific therapeutics, suggesting the use of proteomic information in assessing disease progression as well as predicting patient response to specific treatments. This article discusses both the technology and methods involved in analyzing proteins directly from tissue samples as well as several MS applications, including profiling human tumors, characterizing protein differences between tumor grades, and monitoring protein changes due to drug therapy.