Cancer Research in Switzerland - Krebsliga Schweiz

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Goal
Here we build on these observations to characterize the
cellular and molecular mechanism by which these two
proteins cooperate to promote invasion and metastasis.
The goal is then to interfere with their function as a novel
therapeutic strategy to prevent metastasis. Specifically,
we are studying the effects of CYR61/CCN1 on cancer
cell adhesion, invasion and metastasis by analyzing events
in the cancer cell and by studying how these proteins favour
cancer cell interactions with tumour vessels, the first
step toward metastasis. In addition, we will develop novel
small molecular inhibitors of the receptor based on computer­assisted
molecular modelling.
Methods
We use combined molecular biology, genomic, cell biology
and biochemical experiments to address the research
questions. These experiments will be largely performed in
vitro without the need of mice. Computer­assisted molecular
modelling will benefit from recent technical advances
at the Swiss Institute of Bioinformatics.
Results
We generated different normal and breast cancer cell lines
expressing high level of CYR61 and observed that these
cells become more invasive through a process called epithelial­to­mesenchymal
transition. We also identified cellular
signalling pathways associated with this effect. Their
pharmacological targeting prevented epithelial­to­mesenchymal
transition. These results demonstrated for the
first time that CYR61 induces epithelial­to­mesenchymal
transition. In the second part of the project we developed
a model of the receptor integrin a5b1 obtained by modelling
the experimental structures of homologous receptors
as templates. The model can reproduce the correct
ligand binding mode for a natural ligand. We then used
this model to design structurally diverse ligands, which
will be applied to generate novel inhibitors to test in competition
assays.
Benefits for patients
Results obtained from these experiments are of broad relevance
to both tumour biology and clinical oncology.
For one, they aid understanding of some aspects of the
mechanisms leading to metastasis, and for another, they
may open up new therapeutic perspectives to prevent or
treat metastases. Inhibitors of integrins are currently
in advanced clinical trials in brain cancer, with promising
results. We are now considering designing a clinical trial
to test the safety and activity of integrin inhibitors in preventing
metastasis in patients experiencing relapses after
radiotherapy.
Project coordinator
Prof. Dr Curzio Rüegg
Division de pathologie expérimentale
Université de Fribourg
1, rue Albert­Gockel
CH­1700 Fribourg
Phone +41 (0)26 300 87 66
Fax +41 (0)26 300 97 33
curzio.ruegg@unifr.ch
Rufer Nathalie | Defining molecular, structural and
functional T-cell receptor properties of melanoma-
specific human CD8 + T lymphocytes
(OCS­1995­02­2007)
Although tumour­reactive T lymphocytes can be detected
in cancer patients, these immune responses often fail to
control or eliminate the disease. It has been proposed that
T cells directed against tumour antigens express T­cell receptors
(TCR) of lower affinity/avidity for their antigenic
ligands than pathogen­specific T lymphocytes. Today, recent
progress unveiling the cellular and molecular basis of
the immune response allows the design of novel strategies
for tumour immunotherapy. Adoptive transfer of T cells
engineered with TCRs has been recently developed with
the aim to induce immune reactivity towards defined tumour­associated
antigens to which the endogenous T­cell
repertoire is non­responsive. An attractive approach to
improve this strategy is to optimize the TCR sequence to
increase its affinity for cognate tumour antigen. Olivier
Michielin’s group (at the Swiss Institute of Bioinformatics
in Lausanne) recently developed and applied a novel in
silico structure­based approach for rational design of sequence
mutations that preserve precise antigenic specificity
while increasing the affinity to the peptide­MHC complex.
The objectives of our study were: 1) to assess rigorously
the impact of each optimized TCR variant on T cell function;
and 2) to evaluate the potential usage of these TCRs
for therapeutic interventions by adoptive T cell therapy.
We generated a panel of T lymphocytes expressing tumour­specific
TCR variants of incremental affinities. Essentially,
TCR variants of increased affinity revealed enhanced
T cell responses, in terms of cytokine secretion and target
cell killing, correlating with upregulation of genes typically
involved in T cell activation. Importantly, our results also
allowed us, for the first time, to describe that optimal
T cell function is limited to a given window of TCR­pMHC
binding affinity, with a drastic reduction in cell responsiveness
of T cells expressing either lower or higher TCR
affinities.
In conclusion, we recently established novel experimental
strategies, allowing us to generate tumour­specific T lymphocytes
expressing sequence­optimized TCRs. Thanks
to this unique model we showed that T cell immune responses
against cancer cells can be specifically and drastically
improved. However, our study also revealed the
presence of an affinity window for optimal T cell function.
We are currently characterizing some of the parameters
involved in regulation of TCR function. We propose that
the rational optimization of TCR­pMHC binding above a
given affinity window not only has the potential to cause
cross­reactivity but also can result in drastic reduction
of optimal effector function towards cancer cells. These
results are of particular relevance for the treatment of
patients with cancer by adoptive transfer of T cells genetically
engineered to display affinity­optimized TCRs, as