Hyaluronan induces migration of multidrug resistant murine lymphoma cell lines through Tiam1 activation

MARIANA GARCÍA; LAURA ALANIZ; ROSALÍA CORDO RUSSO; NATALIA SACCODOSSI; ELIDA ALAVREZ; SILVIA HAJOS

San Diego, CA. USA

Congreso; American Association for Cancer Research Annual Meeting; 2008

American Association for Cancer Research AACR

Migration and invasion of tumor cells are processes regulated by both adhesion mechanismsand proteolytic interactions with extracellular matrix components, such as hyaluronan (HA). Inlymphoid tumors, the migratory mechanisms related with cytoskeletal organization seem to bemore important than the proteolytic activity involved in cellular invasion. Tiam1, the guaninenucleotide exchange factor for Rac in vivo, has been found to be involved in cytoskeletalreorganization during tumor invasion. Therefore, the aim of this work was to determine the roleof HA and Tiam1 in cellular migration. For this purpose we used murine lymphoma cell linesresistant to doxorubicin (LBR-D160), vincristine (LBR-V160), as well as a sensitive line (LBR-)that presented dissimilar invasive behavior in vivo. We observed that the three cell linespresented different migratory capacity towards HA gradient in vitro, being LBR-D160 the onethat showed a significant increase in HA-dependent migration. However, the proteolytic activityof metalloproteinases (MMPs) determined by gelatin zymogram analysis revealed similar MMP-2 and MMP-9 activity in the three cell lines, suggesting that other mechanisms may be involvedin such process. Western blot analyses of membrane extracts demonstrated that Tiam1expression was higher in LBR-D160 than in the other cell lines. Moreover, treatment with HAinduced an increase in its expression and activity, since translocation to the plasma membranewas observed. Confocal microscopy of the cell lines transfected with Tiam1-GFP, also showedtranslocation of Tiam1 to the membrane after HA treatment, demonstrating that HA would beable to induce Tiam1 activation. We also analyzed the role of PI3K/Akt pathway in Tiam1activation. We observed by western blot that HA treatment activated this signaling pathway,increasing translocation of PI3K to the plasma membrane and inducing Akt phosphorylation.Inhibiton of this pathway by wortmannin modified the migratory capacity and alsodownregulated Tiam1 activity in these cell lines. In conclusion, we suggest that HA induces themigration of these lymphoma cell lines through Tiam1 activation and this effect is mediated byPI3K/Akt. Our data also demonstrated that differences in cell migration mediated by cytoskeletalreorganization seem to be more relevant in these tumor cells than proteolytic activity.