Purpose: Intensive proliferation and a high degree of migration and invasion are characteristic features of malignant glioblastomas, associated with a poor prognosis. Phosphatidylinositol-3-kinase (Pi3-K) and protein kinase C (PKC) are two phosphorylated proteins involved in glioblastoma cell progression. Phosphorylated focal adhesion protein kinase (FAK) has also been reported to be involved in tumour progression. In a recent study, we demonstrated a correlation between phosphorylated FAK, proliferation rate and 99mTc-(V)-dimercaptosuccinate [(V)-DMSA] uptake. We hypothesised that 99mTc-(V)-DMSA could be a potential imaging agent to evaluate glioblastoma aggressiveness. The aim of the present study was to assess the relationship between 99mTc-(V)-DMSA incorporation rate and modulation of Pi3-K and PKC activity.
Methods: Proliferation, migration and invasion capacities in the presence of protein kinase modulators-staurosporine (PKC inhibitor), 4-phorbol 12-myristate 13-acetate (PMA; PKC activator) and LY294002 (Pi3-K inhibitor)-were correlated with 99mTc-(V)-DMSA cell accumulation in an in vitro model of several malignant glioma cells: G111 (grade II), U-87-MG (grade III) and G152 (grade IV).
Results: In all cell lines tested, LY294002 and staurosporine treatment inhibited cell proliferation, migration and invasion. In contrast, treatment with PMA stimulated tumour aggressiveness. 99mTc-(V)-DMSA uptake was strongly correlated with the % of cellular proliferation (r=0.8462) and the % of cellular migration (r=0.9081), and to a lesser extent with the % of cellular invasion (r=0.7761).
Conclusion: Our results clearly demonstrated that 99mTc-(V)-DMSA reflects Pi3-K and PKC activity and is correlated with tumour aggressiveness. 99mTc-(V)-DMSA could be a reliable in vivo marker providing additional information on the biological status of malignant glioblastoma.