The endogenous anti-angiogenic VEGF isoform, VEGF165b inhibits human tumour growth in mice - PubMed (original) (raw)

The endogenous anti-angiogenic VEGF isoform, VEGF165b inhibits human tumour growth in mice

Es Rennel et al. Br J Cancer. 2008.

Abstract

Vascular endothelial growth factor-A is widely regarded as the principal stimulator of angiogenesis required for tumour growth. VEGF is generated as multiple isoforms of two families, the pro-angiogenic family generated by proximal splice site selection in the terminal exon, termed VEGFxxx, and the anti-angiogenic family formed by distal splice site selection in the terminal exon, termed VEGFxxxb, where xxx is the amino acid number. The most studied isoforms, VEGF165 and VEGF165b have been shown to be present in tumour and normal tissues respectively. VEGF165b has been shown to inhibit VEGF- and hypoxia-induced angiogenesis, and VEGF-induced cell migration and proliferation in vitro. Here we show that overexpression of VEGF165b by tumour cells inhibits the growth of prostate carcinoma, Ewing's sarcoma and renal cell carcinoma in xenografted mouse tumour models. Moreover, VEGF165b overexpression inhibited tumour cell-mediated migration and proliferation of endothelial cells. These data show that overexpression of VEGF165b can inhibit growth of multiple tumour types in vivo indicating that VEGF165b has potential as an anti-angiogenic, anti-tumour strategy in a number of different tumour types, either by control of VEGF165b expression by regulation of splicing, overexpression of VEGF165b, or therapeutic delivery of VEGF165b to tumours.

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Figures

Figure 1

Figure 1

The antiangiogenic VEGF165b is downregulated in human malignant prostate tumour and reduces prostate tumour growth. Anonymous examples of VEGFxxx and VEGFxxxb mRNA expression in TURP chips from benign prostate hypertrophy (A) and malignant prostate cancer (B). (A) RT–PCR of mRNA extracted from benign prostate chips using primers to detect VEGFxxxb and VEGFxxx. Ten out of 11 benign samples showed expression of VEGFxxxb. All but one sample also showed VEGF165 expression. (B) RT–PCR of RNA extracted from malignant prostate chips. Only four of the nine malignant samples showed expression of VEGF165b and eight out of nine malignant samples showed VEGF165 expression. _β_-microglobulin expression was seen in all the malignant tissues (data not shown). (C–F) Images of tumour-bearing mice. Tumours from PC3 cells overexpressing empty pcDNA3 vector (C), VEGF165 (D), VEGF165b (E) and cotransfection with VEGF165 and VEGF165b (F). Scale bar=10 mm. (G) VEGF165b reduced prostate tumour growth in a xenograft mouse model. Three million PC3 cells were injected and VEGF165b overexpression reduced control and VEGF165-mediated tumour growth at day 18 (P<0.05 Kruskal–Wallis, *control vs VEGF165b P<0.05, +VEGF165 vs VEGF165b P<0.05).

Figure 2

Figure 2

VEGF165b inhibits tumour growth in renal cell carcinomas. Renal cell carcinoma (8 × 106 CAKI) cells, transfected with pcDNA3 vectors expressing empty vector (A) VEGF165 (B), VEGF165b (C) or cotransfected with VEGF165 and VEGF165b (D) were injected into the back of nude mice, n_=6 mice per group, photographs taken at 29 days. Tumour border outlined by dotted line. Inset shows excised tumours. (E) Tumour growth curves. (F) Tumour weight at day of culling. (G) Macroscopic estimation of blood content at day of culling. (*P<0.05 VEGF165b vs VEGF165, Δ_P<0.05 ΔΔΔ_P_<0.001 VEGF165+165b vs VEGF165, ##P<0.01 VEGF165 vs pcDNA).

Figure 3

Figure 3

Overexpression of VEGF165b does not affect proliferation when overexpressed in renal cell carcinoma cells in vitro. (A, B) Transfected renal cell carcinoma CAKI cell growth was analysed by direct counting of cells after 24 and 48 h in low serum (0.01% FCS). The doubling time was calculated for each cell population. No significant differences were observed in either instance (_P_>0.05 _n_=3, one-way ANOVA). (C) Cell viability and metabolic rate was analysed at 48 h in low serum with transfected CAKI cells. No significant difference was observed (_P_>0.05 _n_=4, one-way ANOVA).

Figure 4

Figure 4

VEGF165b transfection reduces migration, proliferation and tumour growth in vivo of Ewing's sarcoma tumours. (A) VEGF165b overexpression in Ewing's sarcoma cells resulted in significantly smaller tumours 30 days after implantation of 1 × 106 cells, P<0.05 after 7 days, one way ANOVA. (B) Human microvascular endothelial cells, HMVECs (stained with haematoxylin), migrated towards 10% serum and to conditioned media from Ewing's sarcoma cells (C). In contrast VEGF165b overexpression by these cells reduced migration compared to conditioned media and 10% serum (D). (E) When HMVECs were incubated in conditioned media from tumour cells VEGF165 (100 ng ml−1) could still stimulate increased proliferation. Conditioned media from cells overexpressing VEGF165b inhibited this increase.

Figure 5

Figure 5

Switching expression from VEGF165 to VEGF165b inhibits tumour growth. Mel57 melanoma cells, which express very low levels of VEGF in vivo were transfected with VEGF165 or VEGF165b and 1 × 106 cells injected subcutaneously into nude mice. Whereas the VEGF165 transfected cells grew rapidly, VEGF165b transfected cells grew no more quickly than previous studies have shown for this VEGF-deficient cell type.

Figure 6

Figure 6

VEGF165b reduces vessel density in tumours. Tumour sections were stained with PECAM antibody to visualise vessels. (A–D and F–I) Representative images at × 10 magnification and × 20 (image inset). Quantification of vessel number in CAKI tumours (E) and PC3 (J). Overall P<0.0001 One-way ANOVA P<0.0001 **P<0.01, ***P<0.001 compared to control or VEGF165.

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