Innovations in Analytical Oncology - Status quo of Mass Spectrometry-Based Diagnostics for Malignant Tumor

Recent innovations in mass spectrometry make it possible to diagnose malignant tumors through a rapid, non-destructive and less-expensive way. One of the important facets in this achievement lies in the development of several superior ionization techniques that are essentially derivatives of two authentic methods; matrix-assisted laser desorption ionization (MALDI) and electrospray ionization (ESI). In this review article, we introduce a novel cancer diagnostic system based on probe electrospray ionization (PESI) and logistic regression algorithm. This method uses a very fine needle with a tip diameter of several hundreds nm, which serves as a sampling as well as ionization device. Only a few picolitre (pL) of sample are sufficient to acquire mass spectra for making a diagnosis. Furthermore, as this method does not require any sample pre-treatments that often disorganize the original molecular composition of samples, it has a potential in delineating substances that have been missed by conventional analytical methods. By implementing this technology, we have successfully made in situ diagnosis of malignant tumors in human tissues and in living animals. On the other hand, there are two promising and competitive diagnostic methods; one is desorption ionization mass spectrometry (DESI-MS), and the other is rapid evaporation ionization mass spectrometry (REI-MS) coupled with electrical surgical knife. They are also promising technologies in the new era of analytical oncology. We compare these three methods briefly and attempt to give a new perspective in cancer diagnostics.