Proteomika. Biomarcadores para el diagnóstico no invasivo de enfermedades complejas.

NAPPA technology (Nucleic Acid Programmable Protein Array) is a revolutionary approach for preparing protein microarrays developed by Professor Joshua LaBaer, Director of the Virginia G. Piper Center for Personalized Diagnostics at the Biodesign Institute, Arizona State University. Originally developed by Professor LaBaer and colleagues at the Harvard Proteomics Institute, NAPPA technology allows the expression of up to 7,500 different human proteins at high concentrations and ina biologically active form1. Studies indicate that NAPPA provides up to 1,000 times more protein per spot than levels attainable with conventional protein microarrays. Most significantly, with NAPPA proteins are synthesized in situ on the array surface, thereby avoiding the need to individually express, purify and print, hundreds or thousands of individual proteins.

NAPPA has a wide variety of applications including the study of protein-protein interactions, protein-drug interactions and the identification of biomarkers². Proteomika hs been applying NAPPA technology to the identification of auto-antibodies present in cancer patients as potencial disease biomarkers. By identifying common cancer antigens that trigger antibody production, it is possible to establish characteristic autoimmune profiles allowing the identification of auto-antibodies that can be used as early markers for certain types of cancer.

NAPPA technology solves many of the problems commonly associated with the production of protein microarrays by avoiding the need to generate and purify recombinant proteins before arrays can be printed. NAPPA elegantly overcomes the need for large scale protein production and isolation by printing cDNA copies of the proteins it is wished to express directly to the array. These cDNA clones are designed such that the coding sequence of the protein to be expressed is positioned under the transcriptional control of a promoter sequence and cDNAs are additionally modified to express a "tag" at the carboxyl terminus of the encoded proteins. Incubation of the array with the reagents necessary for in vitro gene transcription and protein translation results in in situ protein expression at the array surface. Co-localizing the printed cDNAs with an antibody that binds the "tag" attached to each expressed protein results in capture of the newly synthesized proteins at discrete and addressable features on the array. Not only does this approach simplify enormously the array production process, it also favors correct protein folding and post-translational modification.

¹Ramachandran et al. Self assembling protein microarrays. Science. 2004, 305:86-90