Profiling of cancer cells using protein microarrays: Discovery of novel radiation-regulated proteins

The advent of DNA microarray technology will likely have a major impact on the molecular classification and understanding of human cancer. Obtaining a global perspective of proteins expressed in cancer cells is considerably m ore challenging. Here we describe a microarray-based platform that can be u sed to measure protein levels and activities in a complex biological milieu such as a cellular lysate. Using a protein microarray made up of 1920 elem ents (146 distinct antibodies) we were able to monitor alterations of prote in levels in LoVo colon carcinoma cells treated with ionizing radiation. Th e protein microarray approach revealed radiation-induced up-regulation of a poptotic regulators including p53, DNA fragmentation factor 40/caspase acti vated DNase, DNA fragmentation factor 45/inhibitor of caspase activated DNa se, tumor necrosis factor-related apoptosis-inducing ligand, death receptor 5, decoy receptor 2, FLICE-like inhibitory protein, signal transducers and activators of transcription lot, and uncoupling protein 2, among others. C onsistent with this observation, an increased percentage of apoptosis was o bserved in irradiated LoVo cells. Interestingly, we also observed radiation -induced down-regulation of carcinoembryonic antigen, a prototypic cancer b iomarker. Selected proteins assessed by microarray were validated by tradit ional immunoblotting. Taken together, our work suggests that protein/antibo dy microarrays will facilitate high-throughput proteomic studies of human c ancer and carcinogenesis.