Salivary Proteomic Comparison of Node Positive & Negative Breast Cancer

Objective: The objective of this study was to compare the salivary protein profiles of pooled saliva specimens from individuals diagnosed with ductal carcinoma of the breast with and without lymph node involvement.

Methods: Three pooled (n=10 subjects/pooled specimen) stimulated whole saliva specimens from women were analyzed. One pooled specimen was from healthy women, another pooled specimen was from women diagnosed with Stage IIa (T2N0M0) invasive ductal carcinoma (IDC) without lymph node involvement and one pooled specimen was from women diagnosed with Stage IIb (T2N1M0) with lymph node involvement. Isotopically tagging proteins in the tumor groups and comparing them to the healthy control group measured differential expression of proteins. Experimentally, saliva from each of the pooled samples was trypsinized and the peptide digests labeled with the appropriate iTRAQ reagent. Labeled peptides from each of the digests were combined and analyzed by reverse phase (C18) capillary chromatography on an LC-MS/MS mass spectrometer equipped with an LC-Packings HPLC.

Results: The results of the salivary analyses among the specimens yielded approximately 174 differentially expressed proteins in the saliva specimens. There were 55 proteins that were common to both cancer stages in comparison to each other and healthy controls while there were there were 20 proteins unique to Stage IIa and 28 proteins that were unique to Stage IIb.

Conclusions: The study suggests that saliva is a fluid suffused with solubilized by-products of oncogenic expression and that these proteins may be differently expressed in the presence of Stage IIa and Stage IIb IDC.