Abstracts for the 25th Annual Scientific Meeting of the International ...

J Immunother Volume 33, Number 8, October 2010
Abstracts
In 5 out of 6 evaluable patients continuing treatment, the response
to MVA was boosted, and in 4 out of 6 evaluable patients,
transgene responses increased either in magnitude and or in
breadth. Furthermore, continued treatment did not impact
regulatory T cell (Treg) levels, which predominantly remained
stable with a few patients showing reduced Treg levels upon
continued vaccination.
Overall, this analysis indicates that MVA-BN s -PRO can break
tolerance against PSA and/or PAP in cancer patients. It also
suggests that transgene-specific immunity can be achieved in
patients despite the pre-existence or co-induction of strong anti-
MVA responses. Based on this interim analysis and contingent
upon complete and confirmatory results, it appears that MVA-
BN s -PRO is a biologically active treatment for patients with nonmetastatic
CRPC.
In Vivo Modeling and Detection of Ovarian Cancer Vascular
Marker TEM1
Chunsheng Li*, Kosei Hasegawa*, Ann-Marie Chackow, Vladimir
Muzykantovw, Chaitanya Divgiz, Phyllis A. Gimottyy, Luigi
GrassoJ, George Coukos*. *Ovarian Cancer Research Center;
w Translational Medicine and Therapeutics, and Environmental
Medicine; Departments of zRadiology; yBiostatistics and Epidemiology,
Univ of Pennsylvania, Philadelphia; JMorphotek, Inc, Exton,
PA.
Rationale: Epithelial ovarian cancer (EOC) remains the most
deadly cancer without efficient detection and eradication methods.
TEM1 is overexpressed specifically in the vasculature of various
tumors and has been implicated in promoting adhesion, invasion
and metastasis. Since EOC responds well to vascular-targeted
therapy, we hypothesize that TEM1 is a tumor vascular marker
with diagnostic and therapeutic potential.
Specific Aims: (1) To characterize TEM1 expression in normal
tissues and EOC samples; (2) to establish huTEM1 murine tumor
vasculature model; (3) to develop a TEM1-specific PET imaging
strategy.
Methods: qPCR and IHC are used to characterize huTEM1
expression in normal and EOC samples. Luciferase positive
huTEM1 expressing murine endothelial cell (huTEM1+ EC) lines
were established and injected alone or with tumor cells onto nude
mice and monitored by bioluminescent imaging.
An antiTEM1 Ab, MORAb004, was radiolabeled with 124I and
injected venously. PET images were acquired at various time points
to visualize hTEM1+ECs in vivo and corresponding biodistribution
studies were performed.
Results: (1) High TEM1 mRNA level correlates with poor outcome
in 2 cohorts of EOC patients. (2) Positive TEM1 staining was
observed in most EOC tissues studied, while no positive staining
was seen in controls. (3) TEM1 expression in huTEM1+ ECs was
confirmed by qPCR, western and FACS analysis. (4) huTEM1+
and control ECs can be detected in nude mice 5 weeks p.i.5)
[124I]MORAb004 has been successfully labeled in high yield and
without loss of immunoreactivity. (6) PET images revealed specific
retention of [124I]MORAb004 in huTEM1+ xenografts and no
discernible uptake in control of the same animal. The radioactivity
in TEM1+ tumor lasted >6 days p.i. (7) Ex vivo biodistribution
study at 48 hours p.i. revealed hTEM1+ xenograft to nontarget
ratios (T/NT) upwards of 16, 84, and 9 for blood, muscle, and
control xenograft, respectively.
Conclusions: (1) Our data suggest that TEM1 is a rational
diagnostic and therapeutic target for EOC. (2) We developed
PET imaging strategy to visualize huTEM1+ cells in mouse model.
(3) Our murine vascular model allows quantitative and specific
monitoring of ECs by optical and PET imaging, therefore serves as
an unprecedented platform for studying the function of tumor
vascular markers, as well as testing new diagnostics and therapeutic
agents against tumor vasculature in vivo. (4) Further studies will
evaluate TEM1 as early detection marker and prognostic factor for
EOC.
Analysis of Intra-Tumor Immunological Changes Induced by
Immunization with Two-Component Messenger RNA-Based
Anti-Cancer Vaccines
Christina Lorenz, Mariola Fotin-Mleczek, Katharina M. Duchardt,
Karl-Josef Kallen. CureVac GmbH, Tübingen, Germany.
Two-component tumor mRNA-based vaccines exhibit two principle
activities: antigen expression and concomitant immune
stimulation. Thus, innate as well as adaptive immune responses
are induced. Intradermal vaccination of tumor-bearing mice with
the two-component mRNA vaccine mediates a strong anti-tumor
response under therapeutic conditions. Depletion experiments
demonstrate the requirement of CD8 T cells for the anti-tumor
effect and the necessity of CD4 T cell help for the induction of
antigen-specific CTLs. FACS analysis of tumor tissue revealed
increased infiltration of activated CD8 T cells and their prolonged
persistence at the tumor site in response to vaccination. Moreover,
therapeutic vaccination inhibited a tumor-induced increase of
myeloid derived suppressor cells (MDSCs) in the spleen and at the
tumor site.
To further elucidate the mechanism of our mRNA-based anticancer
vaccine, tumor-bearing mice were vaccinated repeatedly and
tumors were removed at different time points. Microarray analysis
of total mRNA extracted from removed tumors revealed clear
differences between vaccinated and control mice. Already after two
vaccinations, before the effect on tumor size became visible, a wide
variety of immune response related genes was upregulated in
vaccinated mice. A large proportion of these genes is associated
with activation and cytotoxicity of NK and T cells, Th1
polarization or chemotaxis.
Our findings conclusively demonstrate the comprehensive nature of
the immune response induced by our mRNA based vaccines and
the variety of pathways involved in the anti-tumor effect. Better
understanding of the mode of action allows further improvement of
our vaccine approach and the selection of potential targets for
combination therapies. Additionally, the approach opens new
possibilities for targeted monitoring of induced immune responses.
Targeting of Mortalin-Mutant p53 Interactions by Mortalin
shRNA Leads to Selective Apoptotic Death of Human
Hepatocellular Carcinoma
Wen Jing Lu*, Nikki P. Lee*, Ronnie T.P. Poon*, Sunil C. Kaulw,
Renu Wadhwaw, John M. Lukz. *Surgery, The University of
Hong Kong, Hong Kong; w National Institute of Advanced Industrial
Science & Technology (AIST), Tsukuba, Japan; zNational University
of Singapore, Singapore, Singapore.
Restoration of deregulated apoptotic pathway is one of the main
strategies for cancer therapeutics. Mortalin/mitochondria heat
shock protein 70 (mtHSP70) is a stress protein that is overexpressed
in cancer cells and tissues, which has been proposed to have a role
in human carcinogenesis. It was previously shown that mortalin
interacts with wild type tumor suppressor protein p53 resulting
in abrogation of its transcriptional activation and control of
centrosome duplication functions, both tightly related to cancer
development. Normal human fibroblasts were shown to lack
mortalin-wild type p53 interactions. It was also identified as a
marker for hepatocellular carcinoma (HCC) metastasis and
recurrence by proteomics analysis of matched tumor and nontumor
tissues. In this study, we examined mortalin expression in
100 HCC patients and found that its upregulation has strong
correlation with tumor stage and microsatellite formation. In order
to validate the critical role of mortalin in HCC development and
progression, we recruited its shRNA in eight HCC-derived cell lines
varying in p53 status (loss/mutant p53/wild type). MortalinshRNA
caused apoptosis in most, but not all, HCC cell lines. By
examination of mortalin-p53 interactions and molecular pathway
for apoptosis, we found that induction of apoptosis by mortalinshRNA
depended on occurrence of mortalin-mutant p53 interactions;
the cell lines that lacked these interactions escaped apoptosis.
Most importantly, mortalin-p53 interactions were induced by
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