Osteosarcoma is the most common primary bone tumor. Approximately 80% of osteosarcoma gain metastatic potential. Understanding the molecular mechanisms and pathogenesis of cell motility leading to metastatic sarcomas is essential to improve treatment strategies that will result in a better therapeutic outcome.
Met Receptor Tyrosine is a member of the receptor tyrosine kinase (RTK) family that has a crucial role in oncogenesis. Met activation is a transient event under physiological conditions, whereas in cancer cells it is often constitutively activated. Met ligand, HGF/SF, is particularly active in the reactive stroma of tumors.
Osteosarcoma cell line (U2OS) have high level of activated Met. To better understand the correlation between cell signaling, alteration of the cytoskeleton and the morpho-kinetic alteration leading to motility and metastasis we performed wound healing assays on U2OS cells expressing YFP-tagged Actin. We used our newly developed analytical framework to study the effect of Met activation (HGF/SF) and inhibition (PHA) on cell morphokinetics. The results demonstrate the dependency of U2OS cells group motility on Met signaling. A dramatic effect of Met inhibition (4 folds p<0.001) on the mean square displacement (MSD) is demonstrated. Met expression induced small rounded cell structures with slow kinetics whereas HGF/GF treatment increased motility and displacement. PHA treatment dramatically decreased velocity and displacement and alters cell morphology. Met inhibition by PHA reduces the kinetic parameter and alters cell morphology. Taken together, alteration of the Met signal transduction has a dramatic effect on sarcoma group cell motility morpho-kinetic phenotype. Super resolution (STED) microscopic analysis of U2OS YFP-Actin demonstrate HGF/SF induced fast dynamic actin structures formation and increased edge ruffles could be observed
To study the effect of Met signaling modification on cell motility we over expressed Grb2 or Gab2 in U2OS cells. While Met and Gab1 overexpression increased the number and size of amoeboid blebs, Met and Grb2 formed stable amoeboid podia, similar results are demonstrated in HEK293T cells. Taken together these results demonstrate that HGF/SF-Met signaling plays a major role in sarcoma cells morphokinetic plasticity via alteration of the cytoskeleton.
