Abstract 2451: Insulin-like growth factor-1 receptor (IGF-1R) inhibitors downregulate p53 expression and upregulate the Warburg effect in paediatric glioblastoma cells
Authors: Fong Anne-Christine Wong Te , Andrejeva Gabriela , Bielen Aleksandra , Jones Chris , Griffiths John , Leach Martin O. , Chung Yuen-Li 
Published: May 2015

Abstract
Introduction: Previously we showed that Picropodophyllin (PPP) - an inhibitor of Insulin-Like Growth Factor-1 Receptor (IGF-1R) promotes the Warburg effect and this effect is associated with the downregulation of p53 after 24h of PPP-treatment. Activation of IKK-NF-κB, by loss of p53, has been reported to increase glycolysis in cancer (1).
Aims: To understand the molecular mechanism that links p53 downregulation with increased glycolysis after PPP treatment, we studied the changes in glucose metabolism in 3 different IGF-1R inhibitors - PPP, OSI906 and NVP-AEW541 (NVP) and related these changes to IKK-NF-κB expression and other molecular markers.
Methods: KNS42 cells were treated for 24 hours with 5xIC50 of either PPP (2.4µM), OSI906 (220µM) or NVP (40µM). Culture media from each treated group and controls were analyzed by 1H-MRS. Lactate dehydrogenase-A (LDH-A), p53, pAKT, pS6, MCT-1, MCT-4, Glut-1, pIKK and β-actin (loading control) were examined by western blot (WB). LDH enzyme activity was also measured in PPP- and NVP-treated cells.
Results: After 24 hours of OSI906, NVP and PPP treatment, decreases of 30% (p&lt;0.01), 30% (p&lt;0.01) and 50% (p&lt;0.001) in cell number were found respectively, when compared with their respective controls. 1H-MRS analysis showed increases in glucose uptake (p&lt;0.01) and lactate excretion (p&lt;0.0001) in cells treated with the 3 IGF-1R inhibitors when compared with their corresponding controls. Larger increases were observed in the PPP-treated group when compared to the other 2 groups. In all 3 treatments, WB showed decreases in p53 and pAkt, an increase in Glut-1 and no change in MCT-1 expression. PPP-treated cells showed an increase in pS6 but a decreased pS6 expression was shown in OSI906- and NVP-treated cells. MCT-4 and pIKK expressions were higher in OSI906- and NVP-treated cells, but unchanged in the PPP-treated cells. LDH enzymatic activities were found to be significantly increased in PPP (p&lt;0.01) and NVP (p&lt;0.0001) treated groups, when compared with controls.
Discussions and Conclusion: Our data indicated that the observed increased Warburg effect after IGF-1R inhibition is associated with increased Glut-1 expression, LDH activity and downregulation of p53 but the molecular mechanism is different in PPP when compared to OSI906 and NVP-treated cells. The increased Warburg effect after OSI906 and NVP treatment may be driven by the activation of the IKK-NF-κB pathway following the downregulation of p53, whereas upregulation of pS6 was seen in the PPP-treated cells. The activation of the mTOR-S6K pathway has been linked with the reduction of p53 expression (2). Further investigation is needed to examine why KNS42 cells have a different molecular response to PPP compared with OSI906 and NVP treatment.
1) Kawauchi et al., Nature Cell Biology 30(9): 1792-5, 2007.
2) Lai et al., EMBO 29: 2994-3006, 2010.
Citation Format: Anne-Christine Wong Te Fong, Gabriela Andrejeva, Aleksandra Bielen, Chris Jones, John Griffiths, Martin O. Leach, Yuen-Li Chung. Insulin-like growth factor-1 receptor (IGF-1R) inhibitors downregulate p53 expression and upregulate the Warburg effect in paediatric glioblastoma cells. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 2451. doi:10.1158/1538-7445.AM2014-2451