2002 CTOS Annual Meeting Oral Presentations — Biology

NEOPLASTIC TRANSFORMATION OF PRIMARY HUMAN OSTEOBLASTS OVER-EXPRESSING THE MET RECEPTOR BY MEANS OF TRANSDUCTION WITH LENTIVIRAL VECTORS
[Abstract ID: 22]

Category: Biology

Presentation: Oral

Authors: Riccardo Ferracini¹, Nicola Baldini³, Nadia Coltella¹, Sofia Avnet³, Salvatore Patane'¹, Martina Olivero¹, Luigi Naldini², MariaFlavia Di Renzo¹

Author Institutions: ¹Laboratory of Cancer Genetics of the Institute for Cancer Research and Treatment IRCC Candiolo, Italy; ²Laboratory of Gene Therapy of the Institute for Cancer Research and Treatment IRCC Candiolo, Italy; ³Laboratory for Pathophysiology of Orthopaedic Implants Istituti Ortopedici Rizzoli Bologna, Italy

Presenter: Riccardo Ferracini
rferracini@ircc.unito.it

Correspondent: Riccardo Ferracini
rferracini@ircc.unito.it
Candiolo Italy 10060
Ph: 39 011 9933 460
Fax: 39 011 9933 225

Objectives: The MET oncogene is activated in cell lines where it is amplified and over-expressed. Point mutations of its kinase domain leading to its activation have been found in families suffering from hereditary papillary renal cell carcinomas. We previously showed that the receptor is aberrantly expressed in a number of human osteosarcomas producing the ligand, suggesting that overexpression of MET receptor(s) might contribute to transformation of osteoprogenitor cells.

Methods: To demonstrate the transforming potential of MET in human osteoblast-like cells(HOB-L), we constructed an ex-vivo model using primary cultures of HOB-L stably expressing wild-type or constitutively-active MET receptors by means of transduction with Lentiviral vectors in vitro.

Results: All the wt- and mutant-MET-HOB-L clones showed a different morphology from parental HOB-L cells, namely a loss of contact-inhibition, proliferation at low serum concentrations and anchorage-independent growth. They formed colonies in soft agar, while the parental HOB-L cells did not.
Tumorigenic potential of MET-HOB-L cells was assayed in immuno-compromised SCID mice. Two out 12 animals, which received wt-MET transduced osteoblast cells, developed tumor after a long latency. Nine out of 16 mice receiving mutated MET-expressing osteoblast cells developed tumors in a shorter period. These tumors showed features of highly aggressive and undifferentiated osteosarcomas and carried integrated copies of the human MET.

Conclusions: Over-expression of the MET oncogene activated by a point mutation makes the same cells not only transformed but also highly tumorigenic in immuno-compromised mice. These results show that over-expression of an activated tyrosine kinase suffices to convert a primary human cell into a tumorigenic cell.