IDENTITY AND ORIGIN OF DISCRIMINATORY PEAKS
Immediately after publication of the first report of SELDI-TOF-based diagnostics for ovarian cancer (30), I urged the authors to positively identify the discriminatory peaks so that their serum elevation or decrease in cancer is better understood (36). Efforts to identify these discriminatory peaks have been minimal. Liotta et al. suggested that knowledge of peak identity should not be essential and that this technology represents a new diagnostic paradigm (56). To date, the identity of the five "discriminatory" peaks for ovarian cancer remains elusive (30). Fortunately, HUPO has currently identified as one of their goals to characterize the serum proteome. Also, newer instrumentation is now capable of identifying the discriminatory peaks by using tandem mass spectrometry. As more peaks are positively identified, we will be able to further understand what this technology really detects and if indeed the identified molecules can be confirmed independently to be potential cancer diagnostic markers by using other methodologies (e.g. ELISA). As mentioned, currently identified molecules by this technology are of very high abundance, are mostly produced by the liver, and many are acute-phase reactants (Table IV).