Using SELDI Mass Spectrometry to Identify Cancer Biomarkers in Saliva

Objectives: Technologies are now available enabling saliva to be used to diagnose disease and predict disease progression. The objective of this is pilot study was to determine the use of Surface-Enhanced Laser Desorption/Ionization Time-of-Flight (SELDI) to detect putative breast cancer markers in saliva. Methods: In this pilot study, eight salivary specimens were analyzed: two pooled saliva specimens (cancer & control), three healthy women and three women diagnosed with carcinoma of the breast. The specimens were analyzed on the SELDI using the H4, SAX, and the WCX protein chip arrays and washed at pH of 3.5 and pH 7.5 with each array having unique biochemical properties to separate proteins. Results: The results of the pilot study demonstrated that the WCX protein chip array when prepared and washed at pH3.5 yielded the most promising results. The analyses revealed 4 major protein peaks that were higher in concentration among the cancer subjects as compared to the controls. These protein peaks were 117 kDa, 170 kDa, 228 kDa, and 287 kDa in molecular weight. A 2D gel of the 170 kDa salivary protein was isolated, trypsinized, and analyzed for protein sequencing. The protein was tentatively identified as HER2/neu. Further research is being conducted to identify the 117 kDa, 228 kDa, and 287 kDa proteins. Conclusions: The investigators feel that that there are distinct proteins in saliva that may have diagnostic potential. The SELDI mass spectrometry may be a useful device in expediting the identification of cancer biomarkers in saliva.