Identification of Novel Targets for Cancer Therapy
Identification of Novel Targets for Cancer Therapy
 |
Manuela Baccarini
Prof. Dr. Manuela Baccarini |
Specific aims of the project
Ras and Raf were among the first oncogenes discovered. Their role in
cellular transformation is well documented in the literature and
activating mutations in Ras or in B-Raf are frequently found in human
tumours. Ras and Raf reportedly impinge on the cell cycle via their
best-studied effector, the MEK/ERK pathway. However, the essential
physiological role of Raf in vivo in the context of the whole organism
and in disease is still unclear. Surprisingly, gene targeting of
either Raf-1 and B-Raf has revealed that both Raf-1 and B-Raf exert
essential anti-apoptotic functions that cannot be rescued by the other
Raf isoforms. The molecular targets through which B-Raf and Raf-1
exert their anti-apoptotic function have not yet been defined, but, at
least in the case of Raf-1, this function is independent of MEK/ERK
activation.
The aim of our project is to identify the molecular
mechanism(s) underlying the unique functions of Raf-1 and B-Raf in
apoptosis and to explore their connection to tumourigenesis. To this
end, we will use mouse strains and cell lines produced in the lab, or
obtained through collaboration (conditional B-Raf). Tumor models with
different etiology will be included in the study to test whether the
requirement for Raf is specific to a certain intervention type (e.g.
Ras-driven tumors) or whether it is a more general one. The
experimental design combines phenotype analysis in the context of the
whole organism (in vivo) as well as of explanted tumors (ex vivo) with
biochemical experiments carried out in ablated cells to elucidate the
molecular basis of the phenotype. In the second phase of the project,
we plan to validate the putative targets in vivo by using the
tet-inducible lentiviral knock-down system being developed by NKI1.
Finally, we intend to address the significance of the Raf kinases and
of the novel targets identified in the human system by designing
knock-down experiments in human tumor cell lines to be tested in the
mouse xenograft system being developed by ISREC2.
Background of the group
The MAPK cascade is among the first signaling pathways described and
certainly one of the best studied. Because of their suggested central
role in transformation, the kinases in the pathway are obvious
therapeutic targets. Major efforts are being made to design specific
inhibitors of these molecules, yet their essential biological
functions in the context of the adult animal are still unknown. The
Baccarini group has a long-standing interest in the regulation and in
the physiological role of the MAPK pathway, and specifically of Raf
kinases. Recently, the group has performed the conditional and
conventional knock-out of the Raf kinases and of their effector MEK-1.
The knock-out of Raf-1 has revealed an unexpected, essential and
selective anti-apoptotic role for this enzyme in embryos and in adult
animals with conditional Raf-1 ablation. This anti-apoptotic function
is independent of the activation of the MEK/ERK cascade, and appears
to be related to the ability of Raf-1 to restrain caspase activation.
The molecular basis of the apoptotic defect of Raf-1 knock-out cells
and animals is currently being investigated in detail. The broad focus
of the lab is the analysis of the role of Raf-1, B-Raf and MEK-1 in
organ development, remodeling, and neoplasia, investigated in the
mouse by conditional gene ablation.
References
Mikula, M., et al. EMBO J 20, 1952-1962 (2001).
Jesenberger, V. V. et al. J Exp Med 193, 353-364 (2001).
Baccarini, M. Cell Death Differ 9, 783-785 (2002).
Kubicek, M. et al. J Biol Chem 277, 7913-7919 (2002).
Kolbus, A. et al. J. Exp. Med. 196, 1347-1353 (2002).