Aptamers as an effective strategy for the identification of personalized cancer biomarkers

PERANDONES CLAUDIA; PASQUALINI RODOLFO S; RADRIZZANI MARTIN

San Francisco, EEUU

Congreso; ?Molecular Medicine Tri Conference?, 25-28 de marzo de 2008; 2008

Cambridge HealthTech Institute

Cancer diagnosis based on molecular features can be highly specific and extremely sensitive. However, identification of molecular signatures of a particular tumor remains a great challenge, a fact that is reflected by the very few cancer biomarkers available for effective cancer diagnosis, prevention and therapy. Despite the difficulties, a practical strategy that could differentiate cancer cells from normal cells and allow the design of personalized molecular profiling of any given tumor remains a desirable goal. In this paper, we report a new systematic approach that can circumvent the limitations of current technologies. A new class of molecular probes termed ?aptamers? have been generated to specifically detect target cancer cells based on molecular characteristics, leading to effective disease diagnosis and identification of potential targets for therapy. Aptamers are usually obtained through an in vitro selection process called SELEX (Systematic Evolution of Ligands by Exponential Enrichment), in which aptamers are selected from a library of random sequences of synthetic DNA. We have developed a new strategy to obtain aptamers, modifying the combinatorial libraries in order to allow aptamer selection in a single step, using proteins as targets. With this approach, we have optimized the selection procedure, since an increase in the number of copies of each component of the combinatory library tuned out to be more efficient and successful for selection purposes than the increase usually applied to the whole library. Applying this procedure, we obtained aptamers against pure proteins or a mixture of them. The use of these modified combinatorial libraries in which each component has been amplified before selection (named SIMPLEX, which stands for Selection Improvement by Ligand Excess) enabled us to obtain a great number of specific aptamers. Examples  of the efficency of the procedure are aptamers obtained through this approach that specifically recognized proteins with transient expression during different stages of cerebellum development. Also, this new strategy has proven effective to obtain aptamers that could differentiate cells of a primary tumor breast cancer line from metastatic cells located in the lung. In conclusion, a SELEX modified strategy has been developed -SIMPLEX- to generate a panel of aptamers as useful molecular probes to reveal molecular differences between any two types of cells. The process is simple, fast,  straightforward, reproducible  and usable without prior knowledge of target molecules. This aptamer selection strategy holds great promise in developing molecular probes for cancer diagnosis and personalized cancer biomarker discovery.