Bioconjugation of Laminin Peptide YIGSR with
Poly(Styrene Co-maleic Acid) Increases Its Antimetastatic
Effect on Lung Metastasis of B16-BL6 Melanoma Cells
Yu Mu,* Haruhiko Kamada,* Yoshihisa Kaneda,* Yoko Yamamoto,* Hiroshi Kodaira,*
Shin-ichi Tsunoda,* Yasuo Tsutsumi,* Mistuko Maeda,† Koichi Kawasaki,†
Motoyoshi Nomizu,‡ Yoshihiko Yamada,‡ and Tadanori Mayumi*
,1
*Department of Biopharmaceutics, Graduate School of Pharmaceutical Sciences, Osaka University, 1-6 Yamadaoka, Suita,
Osaka 565-0871, Japan; †Faculty of Pharmaceutical Sciences, Kobe Gakuin University, Ikawadani-cho, Nishi-ku, Kobe
651-2180, Japan; and ‡Molecular Biology Section, National Institute of Dental and Craniofacial Research, National
Institutes of Health, Building 30, Room 405, 30 Convent Dr. MSC 4370, Bethesda, Maryland 20892-4370
Received November 28, 1998
A comb-shaped polymeric modifier, SMA [poly(sty-
rene comaleic anhydride)], which binds to plasma al-
bumin in blood was used to modify the synthetic cell-
adhesive laminin peptide YIGSR, and its inhibitory
effect on experimental lung metastasis of B16-BL6
melanoma cells was examined. YIGSR was chemically
conjugated with SMA via formation of an amide bond
between the N-terminal amino group of YIGSR and the
carboxyl anhydride of SMA. The antimetastatic effect
of SMA-conjugated YIGSR was approximately 50-fold
greater than that of native YIGSR. When injected in-
travenously, SMA-YIGSR showed a 10-fold longer
plasma half-life than native YIGSR in vivo. In addition,
SMA-YIGSR had the same binding affinity to plasma
albumin as SMA, while native YIGSR did not bind to
albumin. These findings suggested that the enhanced
antimetastatic effect of SMA-YIGSR may be due to its
prolonged plasma half-life by binding to plasma albu-
min, and that bioconjugation of in vivo unstable pep-
tides with SMA may facilitate their therapeutic
use.
© 1999 Academic Press
Key Words: peptide modification; YIGSR; poly(styrene-
co-maleic anhydrid); plasma half-life; albumin; binding
affinity.
Tumor metastasis is one of the major causes of mor-
tality in cancer (1–3) and the interaction of tumor cells
with various components of the extracellular matrix
(ECM) such as laminin and fibronectin plays a crucial
role in tumor metastasis (4,5). Therefore, agents which
can selectively block these interactions would be poten-
tially useful as antimetastatic drugs.
Laminins, a family of glycoproteins in basement
membranes, are active in adhesion, migration, spread-
ing and differentiation of various cell types, typified by
endothelial and tumor cells (6). We previously reported
that YIGSR, a core sequence located in the

1 chain of
laminin, markedly inhibited experimental lung metas-
tasis of B16 melanoma cells (7). However, a large
amount of YIGSR is needed to obtain the inhibitory
effect, because of its enzymatic degradation and rapid
rental excretion from blood. These problems are com-
mon to other bioactive peptides and cytokines (8).
Thus, for the therapeutical use of YIGSR as an anti-
metastatic agent, the development of an appropriate
drug delivery system (DDS) is required to improve its
in vivo stability that allows administration at a low
dose. An increase in the blood residency of YIGSR
could augment its inhibitory effect against metastasis
distributed through the vascular circulation. Several
strategies such as peptide-cyclization (9) and D-amino
acid substitution (10) have been reported to enhance
the therapeutic potency of antimetastatic peptides
(YIGSR, etc.) perhaps due to improvement of the phys-
icochemical stability of the steric structure and biolog-
ical stability by inhibiting enzymatic degradation.
However, even these approaches could not overcome
rapid renal excretion from the circulation, and thus the
therapeutic use of YIGSR has remained limited. We
previously reported a new approach in which bioconju-
gation of cytokines (TNF
␣
and IL-6) with water-soluble
polymeric modifier (polyethylene glycol (PEG) (11, 12)
and divinylether maleic anhydride (DIVEMA) (13)
markedly increased their blood-residency, resulting in
effective augmentation of their therapeutic potency
1
To whom correspondence should be addressed. Fax: ϩ81-6-879-
8179. E-mail: mayumi@phs. osaka-u.ac.jp.
Biochemical and Biophysical Research Communications 255, 75–79 (1999)
Article ID bbrc.1999.9930, available online at http://www.idealibrary.com on
75 0006-291X/99 $30.00
Copyright © 1999 by Academic Press
All rights of reproduction in any form reserved.