Expression of a protease-resistant insulin-like growth factor-binding protein-4 inhibits tumour growth in a murine model of breast cancer

Abstract

BACKGROUND: Insulin-like growth factor 1 (IGF1) promotes breast cancer and disease progression. Bioavailability of IGF1 is modulated by IGF-binding proteins (IGFBPs). IGFBP4 inhibits IGF1 activity but cleavage by pregnancy-associated plasma protein-A (PAPP-A) protease releases active IGF1. METHODS: Expression of IGF pathway components and PAPP-A was assessed by western blot or RT -PCR. IGFBP4 (dBP4) resistant to PAPP-A cleavage, but retaining IGF-binding capacity, was used to block IGF activity in vivo. 4T1.2 mouse mammary adenocarcinoma cells transfected with empty vector, vector expressing wild-type IGFBP4 or vector expressing dBP4 were implanted in the mammary fat pad of BALB/c mice and tumour growth was assessed. Tumour angiogenesis and endothelial cell apoptosis were assessed by immunohistochemistry. RESULTS: 4T1.2 cells expressed the IGF1R receptor and IGFBP4. PAPP-A was expressed within mammary tumours but not by 4T1.2 cells. Proliferation and vascular endothelial growth factor (VEGF) production by 4T1.2 cells was increased by IGF1(E3R) (recombinant IGF1 resistant to binding by IGFBPs) but not by wild-type IGF1. IGF1-stimulated microvascular endothelial cell proliferation was blocked by recombinant IGFBP4. 4T1.2 tumours expressing dBP4 grew significantly more slowly than controls or tumours expressing wild-type IGFBP4. Inhibition of tumour growth by dBP4 was accompanied by the increased endothelial cell apoptosis. CONCLUSION: Protease-resistant IGFBP4 blocks IGF activity, tumour growth and angiogenesis .

Nanoparticle-facilitated Intratumoral Delivery of Bcl-2/IGF-1R siRNAs and p53 Gene Synergistically Inhibits Tumor Growth in Immunocompetent Mice

“…However, the combined delivery of IGF-1R siRNA+p53 plasmid, IGF-1R siRNA+Bcl-2 siRNA or Bcl-2 siRNA+p53 plasmid did not further improve the efficacy of cell killing except IGF-1R siRNA+Bcl-2 siRNA+p53 plasmid (p<0.01), which could be due to the interactions among IGF-1R, Bcl-2 and p53 signaling pathways as discussed above, leading to a synergistic effect in reducing cell viability. A similar finding was observed in 4T1 cells (Figure 2) which also possess IGF-1R [43,44] and bcl-2 [45], but are deficient of p53 [46,47], indicating that the seeming synergistic effect of IGF-1R siRNA+Bcl-2 siRNA+p53 plasmid (p<0.01) might be due to the concerted role of IGF-1R as well as Bcl-2 knockdown and overexpression of p53 gene. A statistically significant effect was also exerted by Bcl-2 siRNA+p53 plasmid (p<0.05) in comparison with the nanoparticle-treated cells.…”

Pregnancy-associated plasma protein-A expression in human breast cancer

“…Studies of PAPP-A in human breast cancer, subsets of which are IGF-responsive [10], are limited. There is some evidence that PAPP-A plays a role in promoting breast cancer progression [11,12]. However, a recent study suggested that PAPP-A is epigenetically silenced in human breast cancer [13].…”

Cell cycle arrest in cultured neuroblastoma cells exposed to a bis(thiosemicarbazonato) metal complex

“…Previous studies have shown that IGF-IR activity is important for maintaining cyclin D expression and cell cycle progression (Wilsbacher et al 2008) and that this can be mediated by IGF-IR-dependent PI3 K-Akt activity (Banudevi et al 2010). Also, aberrant metabolism of IGF-IR is associated with a number of cancers including prostate, colorectal, breast and brain (Coulter et al 2008;Ma et al 2010;Kaulfuss et al 2009;Ryan et al 2009). We found that Cu II (gtsm) was a potent inhibitor of IGF-IR expression in the presence or absence of IGF and that this effect was associated with loss of PI3 K expression and activation.…”