Abstract 4059: The bone morphogenic protein 7 (Bmp7) plays a pro-tumorigenic role in pheochromocytoma

Abstract

Abstract Introduction Rats carrying a germline loss-of-function mutation in p27 (MENX syndrome) develop bilateral pheochromcoytoma (PCC) with complete penetrance. Gene expression profiling of rat PCCs identified genes highly expressed in tumors versus normal adrenal medulla. Several of them were found up-regulated also in human PCCs (both sporadic and familial), including the BMP7 gene encoding a member of the bone morphogenic protein family. BMP7 has been shown to be involved in other human cancers, but its role in PCC tumorigenesis is unknown. Methods We used 3 PCC cell lines: PC12 (rat), having low endogenous levels of Bmp7; MPC (mouse) and its aggressive derivative MTT, both with high levels of Bmp7. We also used primary rat PCC cells with high endogenous levels of Bmp7. A Bmp7-expressing plasmid was transfected in PC12 cells. In contrast, Bmp7 gene knockdown in MPC/MTT cells and in primary rat cultures was performed using lentiviral vector expressing anti-Bmp7 shRNA molecules. In vitro assays assessing proliferation (MTT), migration and invasion (Boyden chamber) were then performed. We analyzed the link between p27 and Bmp7 in embryonic mouse and rat fibroblast cells having different doses of p27 gene and in PC12 cells transfected with anti-p27 siRNA molecules. Integrin beta1 expression following activation of Bmp7 signaling was assessed by western blotting in PCC cell lines. Expression of BMP7 and Integrin beta1 was determined also in snap-frozen human primary PCC tissues by western blotting. Results We observed that up-regulation of Bmp7 enhances proliferation, migration and invasion of the PC12 cells, while down-regulation of Bmp7 impairs these properties in MPC and MTT cells. Knock-down of Bmp7 in primary rat PCC cells reduced their viability compared to cells infected with control vector. Additionally, we found that p27 expression was inversely correlated to that of Bmp7, suggesting a potential functional link between the two molecules. Overexpression of Bmp7 in PC12 cells was associated with an increase in integrin beta1 expression. A good correlation was observed in human primary PCC samples between the expression of BMP7 and that of Integrin beta1. Conclusions In conclusion, we demonstrated for the first time that Bmp7 promotes the migration and invasion of PCC cells. We found that endogenous Bmp7 levels are influenced by the amount of p27. Integrin beta1 seems to mediate the ability of Bmp7 signaling to promote migration and invasion of PCC cells. Bmp7 represents a novel target for therapy of PCC since the knock-down in vitro shows promising impairment of the tumorigenic phenotype. Citation Format: Ines Leinhäuser, Ines Höfig, Natasa Anastasov, Felix Beuschlein, Massimo Mannelli, Michael J. Atkinson, Natalia S. Pellegata. The bone morphogenic protein 7 (Bmp7) plays a pro-tumorigenic role in pheochromocytoma. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 4059. doi:10.1158/1538-7445.AM2014-4059