1 research outputs found
SUMOylation regulates LKB1 localization and its oncogenic activity in liver cancer
Background: Even though liver kinase B1 (LKB1) is usually described as a tumor suppressor in a wide variety of
tissues, it has been shown that LKB1 aberrant expression is associated with bad prognosis in Hepatocellular
Carcinoma (HCC).
Methods: Herein we have overexpressed LKB1 in human hepatoma cells and by using histidine pull-down assay
we have investigated the role of the hypoxia-related post-translational modification of Small Ubiquitin-related
Modifier (SUMO)ylation in the regulation of LKB1 oncogenic role. Molecular modelling between LKB1 and its
interactors, involved in regulation of LKB1 nucleocytoplasmic shuttling and LKB1 activity, was performed. Finally,
high affinity SUMO binding entities-based technology were used to validate our findings in a pre-clinical mouse
model and in clinical HCC.
Findings: We found that in human hepatoma cells under hypoxic stress, LKB1 overexpression increases cell viability and aggressiveness in association with changes in LKB1 cellular localization. Moreover, by using sitedirected mutagenesis, we have shown that LKB1 is SUMOylated by SUMO-2 at Lys178 hampering LKB1
nucleocytoplasmic shuttling and fueling hepatoma cell growth. Molecular modelling of SUMO modified LKB1 further confirmed steric impedance between SUMOylated LKB1 and the STe20-Related ADaptor cofactor (STRADα),
involved in LKB1 export from the nucleus. Finally, we provide evidence that endogenous LKB1 is modified by
SUMO in pre-clinical mouse models of HCC and clinical HCC, where LKB1 SUMOylation is higher in fast growing
tumors.
Interpretation: Overall, SUMO-2 modification of LKB1 at Lys178 mediates LKB1 cellular localization and its oncogenic role in liver cancer