Isolation, identification and quantification of differentially expressed proteins from cancerous and normal breast tissues.
BACKGROUND
Infiltrating ductal carcinoma (IDCA) is the most common type of breast cancer accounting for 85% of all invasive breast cancers.


METHODS
Forty tissue specimens comprising 20 pairs of normal and cancerous tissues were analysed. The tissues were homogenized and proteins were extracted using phosphate buffer. The protein extracts from each pair of cancerous and normal tissue were separated using sodium dodecyl sulphate-polyacrylamide gel electrophoresis in the same gel. The protein profiles of both the tissues were compared, and the differentially expressed proteins that were detected at >70% in one or both of the tissue types were selected for protein identification analysis. Target proteins were excised and digested in situ with trypsin prior to liquid chromatography/tandem mass spectrometry (LC/MS/MS) analysis. A protein that was present in both tissue types was further quantified using extracted ions chromatogram.


RESULTS
The proteins were grouped as down-regulated, up-regulated and unique proteins. Twenty-two proteins were identified and eight of the proteins were found unique to cancer. These proteins belong to various molecular classes, i.e. structural protein, hypothetical protein, cytoskeletal protein, enzyme, calcium binding protein and extracellular matrix protein. One extracellular matrix protein, namely collagen alpha-1(I) chain precursor was found unique to cancer. By virtue of its location on the cell surface and its function in cancer growth, this protein may be a biomarker candidate for breast cancer.


CONCLUSIONS
The proteins identified in this study were present in at least 70% of the tissues tested; therefore they should have significant roles in the development of IDCA.
Othman
Mohd Izani
MI
School of Pharmaceutical Sciences, Universiti Sains Malaysia, 11800 USM Penang, Malaysia.
Majid
M I A
MI
Singh
Manjit
M
Man
Che Nin
CN
Lay-Harn
Gam
G
D014408:Biomarkers, Tumor / Q000032:analysis / Q000302:isolation & purification / Q000378:metabolism*; D001940:Breast / Q000378:metabolism*; D001943:Breast Neoplasms / Q000175:diagnosis* / Q000378:metabolism; D018270:Carcinoma, Ductal, Breast / Q000175:diagnosis* / Q000378:metabolism; D024042:Collagen Type I / Q000032:analysis / Q000302:isolation & purification; D000090602:Collagen Type I, alpha 1 Chain; D004591:Electrophoresis, Polyacrylamide Gel; D005260:Female; D006801:Humans; D013058:Mass Spectrometry; D009363:Neoplasm Proteins / Q000032:analysis / Q000302:isolation & purification / Q000378:metabolism*; D040901:Proteomics
D014408:Biomarkers, Tumor; D024042:Collagen Type I; D000090602:Collagen Type I, alpha 1 Chain; D009363:Neoplasm Proteins