2D-PAGE of ovarian cancer: analysis of soluble and insoluble fractions using medium-range immobilized pH gradients.

Ovarian cancer remains a leading cause of cancer death. A comparative proteomic study was performed on normal ovarian tissue (n=5) and grade 3 ovarian tumours (n=5) to search for differentially expressed proteins. In contrast to other studies, here we extracted proteins in soluble and insoluble protein fractions using commercial kits and also utilised three medium-range IPG strips that encompassed the broad pH range of 3-10 (pH 3-6, 5-8 and 7-10). Protein fractions were compared by 2D-PAGE and MALDI-TOF/TOF-MS. Nineteen differentially expressed proteins were identified: HSP60, Grp78, CK19, EF-Tu, MRLC2, prohibitin, Stress-70 protein, TPI and tubulin α6 were up-regulated in grade 3 tumours whereas annexin A2 and A5, antithrombin-III precursor, CBR1, GSTM2, GSTM3, RALDH1, serum albumin precursor, transthyretin precursor and vimentin were found to be down-regulated in grade 3 ovarian tumours. These proteins are associated with cytoskeleton rearrangement, cell metabolism, tumour suppression function, apoptosis and induction of host response.