Identification of Serum Amyloid A Protein As a Potentially Useful Biomarker for Nasopharyngeal Carcinoma

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Abstract
After the publication of the first successful report for ovarian cancer (4) , I indicated that this method is biased towards identifying high abundance molecules that are likely not cancer derived (8) . I further proposed that the most likely source of such putative biomarkers is the liver and that most of these molecules are acute-phase reactants (8) . The report by Cho et al. fully confirms these predictions. First, SAA was found in serum at relatively huge concentrations (∼0.2–2 g/L), levels that are many thousand-fold higher than classical cancer biomarkers (such as carcinoembryonic antigen, prostate-specific antigen, CA125, etc.), which originate from tumor cells. Recently, I have compiled a list of positively identified putative cancer biomarkers by this technology. These molecules are present in serum at concentrations similar to those of SAA (in the gram-per-liter range); they are also derived from the liver, and many of them are acute-phase reactants (6 , 7) . I have also previously proposed that such biomarkers (acute-phase reactants) are not likely to be specific for any type of cancer and would be expected to be elevated in other malignant diseases and in inflammatory diseases (6 , 7) . To their credit, Cho et al. admit that SAA was previously reported to be elevated in many different malignancies, such as cancers of the kidney, colon, prostate, and so forth, and in leukemias and lymphomas (1) . Moreover, they have shown that this biomarker does not originate from the cancer cells but is released into the circulation by the liver (1) .