Abstract Book 2010 - CIMT Annual Meeting

041 Wittmann | Cellular therapy
Comparing genetically engineered T cells for chimeric TCR
versus CD16 + Trastuzumab for adoptive immunotherapy
against HER2 positive breast carcinomas
Sandrine Valsesia-Wittmann 1 , Béatrice Clémenceau 2 , Anne-Catherine Jallas 1 , Anne-Claire
Doffin 3 , Jenny Valladeau 3 , Raphaël Rousseauy, Christophe Caux 1,3 and Henri Vié 2
1 Centre Léon Bérard -plateforme d’Innovation en Immunomonitoring et Immunothérapie-
28 rue Laennec-69008 LYON, France
2 INSERM CRCNA U892 - Institut de Recherche Thérapeutique de l‘Université de Nantes-
44007 NANTES, France
3 CLB-INSERM U590, Cytokines et cancers, Lyon, France
4 Roche, Bale, Switzerland
The HER2 receptor is overexpressed in 25% of
breast cancers and is associated with poor prognosis.
Trastuzumab, a monoclonal antibody targeting
HER2 has been demonstrated to improve survival
of HER2 overexpressing metastatic breast cancer.
However, majority of patients who initially respond
to trastuzumab develop resistance within one year
of treatment initiation, and in the adjuvant setting
15% of patients still relapse despite trastuzumabbased
therapy.
The goal of this project is to develop and compare
efficiency of two adoptive immunotherapy approaches
by genetically engineered T cells to overcome
this resistance. For the first approach, we developed
T lymphocytes armed with an anti-HER2
chimaeric TCR (scFvanti-Her2(FRP5)-CD28TM-
CD3zeta) to directly kill HER2 positive cells. For
the second approach, we developed T lymphocytes
armed with a high affinity IgG FcR (FcgRIIIa, CD16)
linked to its transduction chain FceRIg (CD16/g).
In this latter case, the HER2 antigen is pre-targeted
by trastuzumab to induce a “two step killing”
through Antibodies Dependant Cellular Cytotoxicity
(ADCC).
Results obtained in vitro demonstrated the high
direct killing efficiency of anti-HER2 chimaeric
TCR CTL against HER2 amplified breast carcinoma
cells BT474 or SKBR3 (>75%). However, abnormal
reactivity of these CTL against undetectable HER2
expression was observed (15 to 30% of lysis). This
constitutive non specific activation of chimaeric
TCR might represent an important limitation point
for clinical use.
On the other hand, “two step killing” with CD16/g-
CTL demonstrated a low but very specific cytotoxicity
against HER2 positive cells through ADCC
only in the presence of Trastumumab (20% to
40% of lysis at 30:1 ET). The moderate efficiency
of specific lysis is linked to low levels of CD16/g
expression and uncorrelated to level of HER2 targeted
antigen expression. In order to improve our
strategy and before transfert in animal model, we
are developing new constructs with: (i) modification
of the transduction domain of chimaeric TCR
to block constitutive activation and limit non specific
lysis and (ii) increase the efficiency of CD16/g
expression at the surface of effectors to enhance
ADCC mechanism.
Furthermore, we are comparing in vivo efficacy
of both approaches (“one step” TCR vs “two
step”ADCC) to induce regression of HER2 + or -
breast carcinoma xenograft in immunodeficient
mice model NOD-SCID b2-/-.
Our last results will be presented. Because the
alteration of ADCC mechanisms during trastuzumab
treatment is one rational explanation for
the acquired resistance, improving effectors might
represent a safe adjuvant treatment to prevent resistance.
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