The expression of
vascular endothelial growth factor (
VEGF), a highly potent angiogenic molecule, is thought to be correlated with the development of
colon cancer; however, direct evidence for a role of
VEGF in
metastasis is lacking. This study was designed to more directly establish the role of
VEGF in the growth and
metastasis of human
colon cancer using a genetically engineered
cancer cell line. A stable
VEGF gene-transfected human
colon cancer cell line, LoVo, was made by genetic manipulation using eukaryotic expression constructs designed to express the complete VEGF121
cDNA in the sense orientation. Transfected clones were screened for VEGF121
mRNA expression by Northern blot analysis and for VEGF121
protein expression by Western blot analysis. Consequently, we obtained S17 cells that expressed a high level of both
VEGF mRNA and
VEGF protein. A vector-transfected clone (V7 cell) was used as a control. The experiment with the dorsal air sac method revealed that S17 cells elicited a stronger directional out-growth of capillaries than V7 cells. S17 cells formed faster-growing
tumors than did V7 cells when xenografted s.c. into nude mice, although there was no significant difference in their in vitro proliferation.
Tumors derived from S17 cells had more vascularity, as assessed by counting capillary vessels after staining with
factor VIII, than did
tumors derived from V7 cells (P < 0.05). With regard to the metastatic potential, S17 cells exhibited a higher capacity for both hepatic
metastasis after the splenic portal inoculation and peritoneal dissemination after i.p. injection than did V7 cells. However, S17 cells showed no apparent
metastasis, despite their rapid growth after orthotopic implantation. In conclusion, the present study showed clearly that
VEGF plays an important role in
cancer growth due to stimulation of angiogenesis by accelerating cell growth after reaching the target organs.