We reported previously that an
angiogenesis inhibitor,
E7820, inhibits in vitro tube formation of human umbilical vein endothelial cell through the suppression of
integrin alpha2 expression. Here we describe the antiangiogenic and antitumor effects of
E7820 in mice and discuss the feasibility of using platelet
integrin alpha2 expression on platelets as a
biological marker of the efficacy of
E7820.
Oral administration of
E7820 significantly inhibited
basic fibroblast growth factor-induced angiogenesis in
Matrigel implants and human colon WiDr
tumor-induced angiogenesis in a dorsal air sac model. Twice-daily treatment with
E7820 clearly inhibited the s.c.
tumor growth of seven tumor cell lines derived from human colon, breast, pancreas, and kidney, and completely suppressed the growth of human pancreatic KP-1 and human colon LoVo cell lines. Moreover,
E7820 significantly inhibited the growth of KP-1 and human colon
tumor Colo320DM cells orthotopically implanted in the pancreas and cecum, respectively. The efficacy of
E7820 was comparable in the s.c. and orthotopic
transplantation models. Immunohistochemical analyses using anti-CD31 antibody showed that
E7820 significantly reduced microvessel density in orthotopically implanted KP-1
tumor.
E7820 reduced
integrin alpha2 expression on a megakaryocytic cell line, Dami cells, induced by
phorbol 12-myristate 13-acetate treatment. It also decreased the expression level of
integrin alpha2 on platelets withdrawn from mice bearing s.c. KP-1
tumor at a dosage close to that affording antitumor activity. These data demonstrate that
E7820 showed a broad-spectrum antitumor effect in mice through inhibition of angiogenesis and indicate that the decrease of
integrin alpha2 on platelets might serve as a
biological marker for the antitumor efficacy of
E7820.