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Press Release
Brussels, December 9th 2014
Brain tumor: progress at the ULB Neuroscience Institute
Scientists at ULB Neuroscience Institute, Université libre de Bruxelles, identify a key
factor that can suppress medulloblastoma, the most frequent child brain tumour. This
research is published in the journal Cancer Cell.
Medulloblastoma is the most common brain tumor in children, and its treatment remains
inefficient. The work of a team of researchers led by Luca Tiberi and Pierre
Vanderhaeghen (Université libre de Bruxelles (ULB), WELBIO, IRIBHM and ULB
Neuroscience Institute (UNI)) opens new perspectives on the diagnosis and treatment
of these brain tumors. They discovered a key factor called BCL6, able to suppress the
growth of medulloblastomas in mice and in human tumor cells in culture. This work is
in press in the journal Cancer Cell 1.
Researchers first discovered that BCL6, a factor controlling gene expression, controls the
conversion of neural stem cells into nerve cells in a part of the brain called cerebellum. The
researchers then investigated how BCL6 promotes neurogenesis in the cerebellum. They
found that BCL6 acts as an epigenetic "switch" by turning off the gene expression of a
major signaling pathway called "Sonic Hedgehog", which normally pushes the neural
stem cells to proliferate more and remain undifferentiated. These data provide important
information on the mechanisms of brain development, but have also led researchers to
examine the role of BCL6 in tumorigenesis of the brain.
Indeed, the signaling pathway "Sonic Hedgehog had previously been involved in the initiation
and growth of a tumor called medulloblastoma (the most common form of brain cancer in
children). In this contest the Sonic pathway is a therapeutic target, and Sonic antagonist
drugs have already been developed against these tumors, but the tumors quickly develop
resistance to these treatments. This led the researchers to test whether and how BCL6
could suppress gene expression in response to 'Sonic' signals also in tumours cells
such as medulloblastoma.
Firstly, they tested the effect of BCL6 on cells cultured from medulloblastomas: This
revealed a drastic suppression of the growth of these human tumor cells, through the
inhibition of the "Sonic Hedgehog" signals.
Next, the researchers tested the effects of BCL6 in a model of medulloblastoma in mice.
Remarkably, this revealed that the BCL6 overexpression in the cells at the origin of
these tumors was sufficient to block their tumor growth, and thus largely prolong the
survival of mice (Figure).
Furthermore, the researchers studied mice in which the BCL6 gene is disabled, and it this
case medulloblastomas appeared after a few months, indicating that BCL6 is a 'tumour
suppressor' gene.
Finally, the researchers studied the finer molecular mechanisms of action of BCL6 and
identified another factor acting with BCL6, called BCOR, which was previously found to be
mutated in many cases of human medulloblastomas.
These basic research findings, focusing initially on the normal development of the brain,
have important implications for the understanding, diagnosis and treatment of cancers. On
the one hand it identifies BCL6/BCOR as an attractive target to activate in order to
suppress the growth of medulloblastoma.
Furthermore, this work shows that BCL6 is a natural suppressor of medulloblastomas,
whereas earlier work showed that BCL6 is also a pro-cancer factor in many forms of blood
cancer (leukemia, lymphoma). Thus, the same factor can act as an an oncogene in the
blood, and an anti-oncogene in the brain, illustrating the complexity of the genetics of
cancer, which may have other clinical implications. Indeed, drugs have recently been
developed to inhibit BCL6 to slow the growth of some blood cell tumours. In light of the data
of Tiberi et al., the use of BCL6 inhibitors against blood cell tumours could result in the
initiation of medulloblastoma or other brain tumours.
This work was performed at the Université libre de Bruxelles (IRIBHM and UNI) thanks to
support of the Fonds National de la Recherche Scientifique, Télévie, the Fondation Médicale
Reine Elisabeth, the Région Wallonne (WELBIO et Programme d’Excellence CIBLES), the
Services Fédéraux belges de la Recherche (IUAP/SSTC), the la Fondation Roger de
Spoelberch, and EMBO.
1
Tiberi et al., A BCL6/BCOR/SIRT1 Complex Triggers Neurogenesis and Suppresses
Medulloblastoma by Repressing Sonic Hedgehog Signaling, Cancer Cell (2014),
http://dx.doi.org/10.1016/j.ccell.2014.10.021
Scientific contact :
Pierre Vanderhaeghen, IRIBHM, ULB
+ 32 (0)2 555 41 85 or 86
E mail : [email protected]
http://dev.ulb.ac.be/pvdhlab/