USING PROTEOMICS TO UNRAVEL THE MOLECULAR PATHWAY OF SPARC-MEDIATED TUMORIGENICITY

MARIA ROMINA GIROTTI; MARISOL FERNÁNDEZ; EMILIO CAMAFEITA; JUAN ANTONIO LÓPEZ; JUAN PABLO ALBAR; OSVALDO LUIS PODHAJCER; ANDREA SABINA LLERA

Pamplona, España

Congreso; Joint Congress of the Spanish Society and the Latin American Human Proteome Organization; 2009

SEPROT - LAHUPO

SPARC is a glycoprotein from the extracellular matrix normally expressed duringdevelopment and in wound healing. SPARC is also overexpressed in different tumors,in association with tumor progression. We have showed that downregulation of SPARCexpression by antisense and RNAi techniques in human melanoma cells abolishedtumorigenicity in an in vivo immunodeficient murine model, through still not clearmolecular mechanisms. In the pursuit of molecular mediators of SPARC activity thatmay explain its role in tumor progression, we have performed a proteomic analysisof proteins secreted by L2F6 clone cells (MEL-LES human melanoma cells withRNAi-mediated inhibition of SPARC expression) and compared it to its control cellline LBLAST. Overall, around 12% of detected spots in conditioned media weresignificantly up- or down-regulated by changes in expression levels of SPARC. Afteridentification of differential spots using MALDI-TOF/TOF, a selected group of theseproteins was chosen for technical, biological and functional validation. Differencesin these proteins were confirmed not only in the aforementioned cells but also usingtransient (i.e. adenoviral) restoration of SPARC expression on MEL-LES cells. Mostinterestingly, several of the validated proteins are well-known mediators of tumorprogression but were not previously related to SPARC. In particular, we have collectedexperimental evidence that confirm the role of SPARC as an important inductor ofproteins involved in tumor invasion. Our results constitute the first evidence thatSPARC and these proteins may participate in a single molecular network that leads totumor progression.