FGF-8b increases angiogenic capacity and tumor growth of androgen-regulated S115 breast cancer cells

Abstract

Fibroblast growth factor 8 (FGF-8) is a secreted heparinbinding protein, which has transforming potential. Alternative splicing of the mouse Fgf-8 gene potentially codes for eight protein isoforms (a ± h) which di er in their transforming capacity in transfected cells. S115 mouse mammary tumor cells express a transformed phenotype and secrete FGF-8 in an androgen-dependent manner. In order to study the role of FGF-8 isoforms in the induction of transformed phenotype of breast cancer cells, we over-expressed FGF-8 isoforms a, b and e in S115 cells. Over-expression of FGF-8b, but not FGF-8a or FGF-8e, induced androgen and anchorage independent growth of S115 cells. FGF-8b-transfected S115 cells formed rapidly growing tumors with increased vascularization when injected s.c. into nude mice. FGF-8a also slightly increased tumor growth and probably tumor vascularization but FGF-8e was not found to have any e ects. The angiogenic activity of FGF-8b and heparinbinding growth factor fraction (HBGF) of S115 cell conditioned media was tested in in vitro and in vivo models for angiogenesis using immortomouse brain capillary endothelial cells (IBEC) and chorion allantoic membrane (CAM) assays. Recombinant FGF-8b protein was able to stimulate proliferation, migration, and vessellike tube formation of IBECs. In addition, stimulatory e ect of S115-HBGF on IBE cell proliferation was evident. A positive angiogenic response to FGF-8b was also seen in CAM assay. The results demonstrate that the expression of Fgf-8b is able to promote vessel formation. Angiogenic capacity probably markedly contributes to the ability of FGF-8b to increase tumor growth of androgen-regulated S115 mouse breast cancer cells. Oncogene (2001) 20, 2791 ± 2804.

FGF8 isoform b expression in human prostate cancer

“…Tumours produced by FGF8b-expressing MCF7 cells were also shown to be more vascular than untransfected controls . Mattila et al (2001) have also demonstrated that FGF8b is able to stimulate migration and sprouting of mouse brain capillary endothelial cells. In this study, FGF8b promoted endothelial cell differentiation, organisation of capillary cells into cords and formation of lumen-like structures.…”

Fibroblast growth factor/fibroblast growth factor receptor system in angiogenesis

“…FGF2 [50] and FGF8b [17] can enhance endothelial cell reorganization on Matrigel. The process requires the activation of the proteolytic machinery, including type IV collagenase(s) and TIMPs production [51] as well as uPA and PAI-1 upregulation [52], a 6 b 1 integrin receptor engagement [53], PECAM-1 [54], and activation of the small GTPase Rac [55].…”

“…Recently, also the FGF8b isoform has been shown to stimulate endothelial cell proliferation in vitro [17]. FGFR engagement involves the activation of several parallel signaling pathways as a consequence of receptor autophosphorylation followed by recruitment of Shc, FRS2, and Crk adaptor molecules (for a review see [16]).…”

“…FGF1 and FGF2 [27,28], the FGF8b isoform [17], and FGF10 [29] stimulate chemotaxis and/or chemokinesis in endothelial cells. Similar to cell proliferation, the chemotactic effect of FGF2 requires the activation of the MAPK signaling pathway [30] and is abolished by PKC down-regulation [31].…”

“…Subnanomolar concentrations of FGF7/KGF induce neovascolarization in the avascular rat cornea [29]. FGF8b elicits an angiogenic response in the CAM assay [17] significantly enhanced by heparin co-administration (Presta, unpublished observations). Transient expression of FGF9 in transgenic mice results in alterations of retinal pigment epithelium possible related to alterations of the choroidal vasculature [96].…”