Gene expression profiling of the antiangiogenic factor 16K human prolactin (hPRL) on endothelial cells underlines the key role of NF-κB and reveals novel mechanisms of action
Sébastien Tabruyn1, Céline Sabatel1, Ngoc-Quynh-Nhu Nguyen1, Catherine Verhaeghe1, Karolien Castermans2, Ludovic Malvaux1, Arjan Griffioen2, Joseph Martial1 & Ingrid Struman1
The 16-kDa N-terminal fragment of human prolactin (16K hPRL) is a potent angiostatic factor described to prevent tumor growth in mouse models. Using microarray experiments, we have dissected how the endothelial-cell genome responds to 16K hPRL treatment. Of the 23.000 transcripts present on the chips, 210 are regulated by 16K hPRL. Bio-informatic analysis and experiments performed on endothelial cells with various chemical inhibitors clearly suggest that NF-κB is crucial for the direct regulation of the majority of theses genes. In addition, our results reveal that the angiogenesis inhibitor 16K hPRL regulates apoptosis and proliferation in endothelial cells by numerous non-previously identified targets. Unexpectedly, a large proportion of 16K hPRL-regulated genes turned out to be associated with the process of immunity. 16K hPRL induces expression of various chemokines and endothelial adhesion molecules. These expressions, under the control of NF-κB, result in an enhanced leukocyte-endothelial cell interaction. Furthermore, analysis of B16-F10 tumor tissues reveals a higher expression of adhesion molecules (ICAM-1, VCAM-1 or E-selectin) in endothelial cells and a significantly higher number of infiltrated leukocytes within the tumors treated with 16K hPRL than in the untreated ones. In conclusion, this study describes a new anti-tumor mechanism of 16K hPRL. Since cellular immunity against tumor cells is a crucial step in therapy, the discovery that treatment with 16K hPRL overcomes tumor-induced anergy may become important for therapeutic perspectives.
Work supported by grants from the F.R.I.A. (Fonds pour la formation à la recherche dans lindustrie et lagriculture), Télévie, F.N.R.S. (Fonds national pour la recherche scientifique), the Fédération Belge contre le Cancer and the Université de Liège (Fonds Spéciaux).