DRC Proteomics Reveals Lower Abundance Salivary Proteins in Breast Cancer

Objectives: Breast cancer remains one of the most significant causes of cancer-related death in women. Recent technologies aimed at earlier detection of breast cancer such as mammography screening, MRI, new chemotherapeutic treatment
and prevention agents, etc. have resulted in very little improvement in earlier detection, prognosis for recurrence or survival rates. The best case scenario of successful treatments for breast cancer unfortunately still allows up to 30 % rate of local recurrence or distant metastases. Our group has previously demonstrated a novel proteomics approach using Dynamic Range Compression( DRC) for analyzing lower abundance proteins in saliva. While we have previously reported alterations in certain higher abundance proteins, DRC allows for evaluation of potentially significant lower abundance salivary proteins. In this study, we aimed to determine abundance changes in specific proteins in saliva which may be useful in detection of recurrent breast cancer comparing DRC with regular iTRAC proteomics.

Methods: Whole saliva was collected from patients diagnosed with recurrent breast cancer as well as age-sex matched controls by standard methods. Using a multidimensional peptide fractionation-based workflow, samples were analyzed in parallel; one sample aliquot using DRC and another without. This technique differentiates proteins with higher or lower absolute abundance.

Results: Bioinformatics analysis revealed significant fold changes of known circulating breast cancer biomarkers in saliva of subjects with recurrent breast cancer vs. controls. Specifically, CD-59 and Mammaglobulins A and B were increased over 600 and 12 fold, respectively. We also identified increases in a number of other lower abundance proteins in saliva of subjects which have been associated with breast cancer including, carcinoembryonic antigen(CEA), and CD44( tumorigenesis).

Conclusions: Through proteomic analysis of saliva using novel methods of DRC, we
identify specific known circulating biomarkers for recurrent breast cancer in saliva which might have future utility as a non-invasive diagnostic/prognostic procedure which could improve earlier detection of recurrent disease and thereby intervention and overall survival.