Abstract
BACKGROUND
Glioblastomas are among the most malignant primary brain tumors. GBMs are highly angiogenic, exhibit invasive growth, and elevated glycolysis. Under glycolytic conditions, glucose from the blood is metabolized in astrocytes into lactate by LDHA, and exported by MCT4 into the extracellular compartment, inducing a concomitant acidification of the microenvironment. LDHB, generally expressed in oligodendrocytes or neurons, metabolizes lactate into pyruvate for generating ATP in mitochondria. LDH expression was reported to be linked to phenotypic modifications in vitro in GBMs but the mechanisms and the precise role in vivo have not yet been investigated.
MATERIAL AND METHODS
We designed LDHA and LDHB Crispr-Cas9 constructs for infecting glioblastoma stem-like cells. Results: In vitro tumor cell invasion was not significantly impaired in sgLDHA glioblastoma cells, even under extreme hypoxic conditions. Tumor development was moderately impacted in terms of invasion or vascular density. We then explored the role of LDHB in these processes. LDHB knock-out cells had decreased invasive properties in vitro but surprisingly tumors were highly hemorrhagic and angiogenic, supporting a role of tumor-derived LDHB in blood vessel development. We furthermore evaluated the consequences of a double LDHA and LDHB knock-out in the glioma cells. Under hypoxic conditions, sgLDHA/B cell invasion was dramatically decreased in comparison to control cells, and apoptosis was also increased. Tumor development was dramatically impaired for LDHA/LDHB knockout tumors.
CONCLUSION
These results indicate the complex role of LDH enzymes in glioblastoma development. It constitutes the basis for further mechanistical studies linking lactate metabolism to brain tumor development and perturbation of the neuro-vascular microenvironment.