Endocrine Abstracts

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 vs 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 cell lines such as PC12 (rat PCC), with low endogenous levels of Bmp7, and MPC (mouse PCC) and its aggressive derivative MTT, both with high levels of Bmp7. We also use primary rat PCC cells with high levels of Bmp7. Bmp7-expressing plasmid was transfected in PC12 cells. Bmp7 gene knockdown in MPC/MTT cells and 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 fibroblast cells with either mutant or knocked-out p27 or in sip27- transfected PC12 cells.

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.

Conclusion: In conclusion, we observed that Bmp7 promotes the tumorigenic phenotype of PCC cells and that its level is influenced by the amount of p27. BMP7 represents a novel target for therapy of PCC since the knock-down in vitro shows promising impairment of the tumorigenic phenotype.