Protein profiling of microdomains purified from renal cell carcinoma and normal kidney tissue samples

Renal cell carcinoma (RCC) is representing about 3% of all adult cancers. A promising strategy for cancer biomarker discovery is subcellular comparative proteomics, allowing enriching specific cell compartments and assessing differences in protein expression patterns. We investigated the proteomic profile of a peculiar RCC subcellular compartment, plasma membrane microdomains (MD), involved in cell signalling, transport, proliferation and in many human diseases, such as cancer. Subcellular fractions were prepared by differential centrifugation from surgical samples of RCC and adjacent normal kidney (ANK). MD were isolated from plasma-membrane-enriched fractions after Triton X-100 treatment and sucrose density gradient ultracentrifugation. MD derived from RCC and ANK tissues were analyzed after SDS-PAGE separation by LC-ESI-MS/MS. We identified 93 proteins from MD isolated from RCC tissue, and 98 proteins from ANK MD. About 70% of the identified proteins are membrane-associated and about half of these are known as microdomain-associated. GRAVY scores assignment shows that most identified proteins (about 70%) are in the hydrophobic range. We chose a panel of proteins to validate their differential expression by WB. In conclusion, our work shows that RCC microdomain proteome is reproducibly different from ANK, and suggests that mining into such differences may support new biomarker discovery.