Cancer Research in Switzerland - Krebsliga Schweiz

and Rac1 are frequently altered in cancer tissues, which
could account for their altered migratory properties.
Therefore, our studies are directly relevant to understanding
the molecular mechanisms of regulation of signalling
pathways that are altered in cancer. We further studied
the dynamics of cingulin and paracingulin in living cells
and clarified differences in their behaviour and localization,
which will help to clarify their redundant and non­redundant
functions. Using antibodies that we developed in
our laboratory, we studied the expression of cingulin in
different types of human lung tumours in collaboration
with the Department of Clinical Pathology at Geneva
University Medical School. These results, and results obtained
using several other antibodies against tight junction
proteins and reverse­transcription polymerase chain
reaction to assess gene expression, allowed us to propose
a new molecular classification of lung carcinomas based
on expression of specific tight junction proteins. Recently,
we identified a novel adherens junction protein, PLEKHA7,
against which we developed specific monoclonal antibodies,
and which we would like to use to examine its expression
in human cancer, which has not been done so far.
In summary, the results that we obtained have provided
new information on the function of certain tight junction
proteins, their role in the process of differentiation and
cancer formation and their possible use in cancer diagnosis.
In addition, our studies led to the discovery and preliminary
characterization of a new adherens junction protein.
Project coordinator
Dr Sandra Citi
Département de biologie moléculaire
Sciences III
Université de Genève
4, boulevard d’Ivoy
CH­1205 Genève
Phone +41 (0)22 379 61 82
Fax +41 (0)22 379 68 68
sandra.citi@unige.ch
Donda Alena | CD1d-antitumor bifunctional molecules
to redirect the innate and adaptive immune responses
to the tumor site (OCS 02248­08­2008)
When activated by the CD1d protein expressed by antigen­presenting
cells (APC), invariant natural killer T
(iNKT) cells are able to transactivate the innate and adaptive
immune system, and their antitumour activity is well
demonstrated. In the initial phase of this project, we
showed that repeated injections of a soluble recombinant
CD1d protein loaded with the glycolipid ligand a­galactosyl
ceramide (aGalCer) was able to induce sustained iNKT
cell activation, in contrast to the short­lived stimulation
obtained with the ligand alone. Importantly, when CD1d
was fused to an antitumour antibody fragment (CD1danti­HER2),
delayed tumour growth was obtained, associated
with tumour infiltration by iNKT, NK and T lymphocytes,
all able to kill cancer cells.
In order to get closer to a clinical application, the second
phase of this project included the following aspects: 1)
We extended the targeting of CD1d to different types
of cancer. In addition to the targeting of HER2 over­ex­
pressed in breast cancer, we developed a CD1d­anti­CEA
fusion protein specific of a tumour antigen over­expressed
in colon cancer, as well as a CD1d­anti­VEGFR3 fusion
protein targeting a marker of tumour neo­vascularization.
Sustained iNKT activation and inhibition of tumour
growth by these three CD1d bi­functional proteins were
evidenced in several tumour models. 2) At the cellular
level, in vivo and in vitro experiments demonstrated that
iNKT cell activation by soluble CD1d proteins prevented
the negative retro­control of PD­1/PD­L1 interaction that
normally occurs during cell­cell interaction between iNKT
and APCs, leading to their subsequent unresponsiveness.
The attenuated PD­1 upregulation largely explains the
sustained iNKT cells obtained with recombinant CD1d
proteins, which is optimal for a systemic treatment. 3)
Several in vivo experiments have shown that the adjuvant
effect of CD1d­mediated therapy on the adaptive immune
response remains limited by immunosuppressive
mechanisms developed in the periphery and at the tumour
site. In particular, the expansion of myeloid­derived
suppressor cells (MDSCs) induced by the tumour environment
is known to inhibit the antitumour immune response
and remains a challenge for cancer immunotherapy. MD­
SCs act by various mechanisms, among which are several
enzymatic activities such as arginase 1, which depletes arginine
essential for the activity of T lymphocytes. We
could demonstrate the inhibitory effect of arginase 1 on
CD1d­mediated therapy in a mouse model in which arginase
1 has been eliminated in the myeloid compartment.
In these mice, the antitumour effect of CD1d­antitumour
treatment was indeed far more potent than in mice with
active arginase 1.
In view of these results, we are testing chemotherapeutic
agents able to deplete preferentially MDSCs, such as
5­fluorouracil. The next step is to combine CD1d­mediated
immunotherapy with chemotherapy, and these
protocols will be tested in two transgenic mouse models
developing spontaneous tumours, representative of melanoma
tumours and prostate cancer in humans. Combination
of multiple anti­cancer therapies is more and more
considered, as it can result in a synergistic tumour inhibition
and limit tumour escape.
Project coordinator
Dr Alena Donda
Département de biochimie
Université de Lausanne
Chemin des Boveresses 155
CH­1066 Epalinges
Phone +41 (0)21 692 58 57
alena.donda@unil.ch
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