Unexpected tumor supressor roles for Vav3 in melanoma

NAHUEL CESATTI LALUCE; ANSELMINO LUCIANO; MALIZIA FLORENCIA; MAMBERTO MACARENA; MAURICIO MENACHO MÁRQUEZ

Mar del Plata

Congreso; LXV REUNIÓN ANUAL DE LA SOCIEDAD ARGENTINA DE INVESTIGACIÓN CLÍNICA (SAIC); 2020

Melanoma is the most dangerous form of skin cancer, accounting for the third highest number of lives lost among all cancers. Since in our country the mortality has doubled in last decades, finding prognostic and therapeutic targets appears a key task.Vav proteins are guanosine nucleotide exchange factors (GEFs) for the Rho GTPase family. They modulate processes highly associated to the development of cancer and metastasis. Classically the members of Vav family are considered proto-oncoproteins. However their involvement in melanoma is unknown. We previously characterized the role of Vav2 in melanoma; now we began to study the putative involvement of Vav3. First, by bioinformatic approaches with human patients databases, we found that Vav3 expression correlated with patient survival (p≤0.0001). Second, we modulated we modulated Vav3 expression in B16-F0 cells by transfection methods, generating cells with reduced and increased expression of Vav3. By MTT assays we explored proliferation, noting that decreased expression of Vav3 promotes proliferation (p≤0.001) whereas increased levels of this protein affected negatively cell growth (p≤0.001). By fluorescence studies with rhodamine-phalloidin staining we observed that Vav3 affected actin cytoskeleton and cell morphology. Cells with decreased Vav3 expression showed an improved migratory behavior as observed by wound healing assays (p ≤ 0.05). Finally, we injected cells subcutaneously in female 8-week old C57BL/6 mice (n=6/group). Tumor volume was measured biweekly for 3 weeks. Growth kinetics indicated that decreased Vav3 expression promoted increased tumor proliferation (p≤0.01) and lung metastasis development. Increased Vav3 expression affected negatively melanoma growth (p≤0.05). Altogether, our results suggest a tumor suppressor role for Vav3 in melanoma, in contraposition with the pro-tumoral function reported for Vav2 in this tumor type and the classical role reported previously for Vav3 in other tumors.