The protein phosphatase 2A (PP2A) inhibitor, LB100, has been shown in 
pre-clinical studies to be an effective chemo- and radio-sensitizer for 
treatment of various cancers. We investigated effects associated with LB100 
treatment alone and in combination with cisplatin for medulloblastoma (MB) in 
vitro and in vivo in an intracranial xenograft model. We demonstrated that LB100 
had a potent effect on MB cells. By itself, LB100 inhibited proliferation and 
induced significant apoptosis in a range of pediatric MB cell lines. It also 
attenuated MB cell migration, a pre-requirement for invasion. When used in 
combination, LB100 enhanced cisplatin-mediated cytotoxic effects. Cell viability 
in the presence of 1 uM cisplatin alone was 61% (DAOY), 100% (D341), and 58% 
(D283), but decreased with the addition of 2 μM of LB100 to 26% (DAOY), 67% 
(D341), and 27% (D283), (p < 0.005). LB100 suppressed phosphorylation of the 
STAT3 protein and several STAT3 downstream targets. Also, LB100 directly 
increased cisplatin uptake and overcame cisplatin-resistance in vitro. Finally, 
LB100 exhibited potent in vivo anti-neoplastic activity in combination with 
cisplatin in an intracranial xenograft model.