INTERNATIONAL MYELOMA FOUNDATION
The Award in Aki's Memory 2006
Name:
Eishi ASHIHARA, MD, PhD
Institution: Department of Transfusion Medicine and Cell Therapy, Kyoto University Hospital
Address:
54 Shogoin Kawahara-cho, Sakyo-ku, Kyoto 606-8507, JAPAN
Research Appointments:
1991.4-1993.2
Research Fellow in Hematology, Kyoto Prefectural University of Medicine
(Prof. Chihiro Shimazaki)
1993.2-1994.3
Visiting research fellow in New York Blood Center (President John W. Adamson)
1994.4-1995.3
Research Fellow in Hematology, Kyoto Prefectural University of Medicine
(Prof. Chihiro Shimazaki)
1995.4-2003.8
Assistant Professor in Hematology, Kyoto Prefectural University of Medicine
2003.9-2005.3
Assistant Professor in Translational Research Center, Kyoto University Hosipital
2005.4-
Assistant Professor in Department of Transfusion Medicine and Cell Therapy,
Kyoto University Hospital (Prof. Taira Maekawa)
Subject:
Gene Targeting Therapy and Cell Therapy for Refractory Multiple Myeloma
Experimental plans:
Agents of molecular targeting therapy inhibit the proliferation of malignant-transformed
cells by blocking the signals for cell proliferation.
Several targeting agents developed to
counteract multiple myeloma (MM) have yielded promising results, however, it is still difficult to
achieve a definitive cure for myeloma.
Bisphosphnates (BPs), developed primarily to treat bone
diseases, may also act as anticancer drugs by inhibiting the activation of Ras and Ras-related
proteins through suppression of both geranylgeranylation and farnesylation.
We previously
demonstrated that YM529, a third-generation BP, inhibits the proliferation of MM cells.
This time,
we examined the effects of zoledronate (ZOL), another third-generation BP on MM cells.
ZOL
inhibited the proliferation of MM cells in a time- and dose-dependent manner similar to that of
YM529 and induced apoptosis by inhibiting the prenylaiton of Rap1-A, a Ras-related protein.
These effects were observed in l-pam-sensitive cell lines as well as in l-pam-resistant cell lines.
It
is suggested that ZOL may be a useful as a molecular targeting agent in myeloma cells.

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In addition to their direct antitumor activities, third-generation BPs expand T cells,
which exhibit major histocompatibility complex-unrestricted lytic activity.
After peripheral blood
mononuclear cells were stimulated with ZOL and interleukin-2 for 14 days, T cells were expanded
by up to about 800-fold.
These expanded T cells were V9V2 subsets, having cytotoxic activity.
We previously observed that pretreatment with ZOL enhanced the cytotoxicity of T cells on
non-small
cell
lung
cancer
cells.
Internalization of ZOL by cancer cells
Figure:C ytotoxicity of T cells
on m yelom a cells
rapidly led to the inhibition of farnesyl
80
pyrophosphate (FFP) synthase, resulting in
70
ty
intracellular
accumulation
of
60
isopentenylpyrophosphate that is situated
oxici 50
tc 40
upstream of FFP synthase in the mevalonate
fi
ZO L(-)
30
eci
ZO L(+)
pathway. We investigated the
p
in
vitro
20
%S
cytotoxicities of T cells on MM cells alone
10
or in combination with ZOL-pretreatment.
0
x1
x5
x10
x25
Expanded
T
cells
revealed
strong
E/T ratio
anti-myeloma effects either with or without ZOL-pretreatment (Figure).
It is suggested that cell
therapy using T cells could be a powerful strategy for blocking MM.
We are now investigating
the in vivo effects of T cells using a xenograft myeloma mouse model and searching for new
antigens on myeloma cells for presentation to T cells.
RNA interference is a newly discovered mechanism for silencing genes in a
sequence-specific manner at the mRNA level through the introduction of small cognate
double-stranded interfering RNA (siRNA) into cells, and has recently been introduced into cancer
therapy, primarily in vitro.
However, the therapeutic use of siRNA is largely dependent on the
development of a drug delivery system that efficiently delivers siRNA into target cells.
To deliver
siRNA into MM cells, we are creating a CD138 monoclonal antibody (mAb) combined siRNA
system.
CD138 (syndecan-1) is highly expressed on MM cells, but not on normal hematopoietic
cells.
As gene-silencing targets, we selected Polo-like kinase-1 (PLK-1) and -catenin.
PLK-1
is one of the most important regulators of mitotic progression in mammalian cells, and we reported
that the expression of PLK-1 in urinary bladder cancer cells correlates with the disease prognosis.
-catenin, a cytoplasmic protein of Wnt pathway, associates with the TCF/lymphocyte-enhancer
factor (TCF/LEF) family.
-catenin-TCF/LEF complexes migrate to the nucleus and activate the
transcription of c-myc and cyclin D1, resulting in cell proliferation. Preliminary data show that
PLK-1 and -catenin are overexpressed in myeloma cell lines.
We suggest that CD138 mAb
combined with PLK-1 siRNA or -catenin siRNA may have potential as a powerful tool for
molecular targeting therapy.
A novel therapy based on a combination of gene-targeting therapy
and cell therapy for MM is now under investigation in our laboratory.

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