Breaking news: S. Mahalingam

Title: The Role of Fibroblast Growth Factor Signalling in Osteosarcoma

Field of research: Oncology

Keywords: Bone, Osteosarcoma, Fibroblast Growth Factor

Authors:

S. Mahalingam BSc, S. Mahalingam BSc, R. Al-Dabbagh MD/PHD, D. Weekes MD/PHD, A.E. Grigoriadis MD/PHD

Presenting author:

S. Mahalingam BSc

 

Introduction:

The mechanisms responsible for oncogenic transformation of osteoblasts and development of osteosarcomas are not known. Preliminary experiments using a c-Fos transgenic mouse model of osteosarcoma (OS) suggest an important role for fibroblast growth factor (FGF) signalling in the abnormal growth of osteoblasts and tumour formation. We hypothesise this to be the case in humans. Here, we investigate the role of fibroblast growth factors and FGF receptors (FGFRs) in the growth control of normal and transformed human osteoblasts. The specific aims of this study were to compare FGFR expression between normal human osteoblasts (HOBs) and OS cells; to determine the effects of FGF on growth and proliferation of HOBs compared to OS cells; and to establish a 3-dimensional culture model to represent better an in vivo environment.

 Material & methods:

Western blot analysis of FGFR expression was performed on HOBs and 3 human OS cell lines (MG-63, Saos2, U2OS). Cell culture techniques were utilised to investigate the effect of bFGF and SU5402 (FGFR inhibitor) on cell transformation. Proliferation and apoptosis were observed using proliferation and MTT assays. In parallel to these in vitro experiments, we developed an in ovo model. Our system involves grafting tumours (explants from mouse model) onto a developing chick chorioallantoic membrane (CAM) in the presence or absence of bFGF. Statistical analyses were performed using the two-tailed Student’s t test.

 Results:

FGFR1 was overexpressed in MG-63 OS cells, and FGFR4 was overexpressed in all three OS cell lines in comparison to HOBS. bFGF induced features of transformed cells in HOBs, particularly, anchorage-independent growth and lack of contact inhibition; this was reversed by SU5402. bFGF increased the rate of proliferation of OS cells in comparison to HOBs. All tumours grafted onto the CAM became vascularised. Interestingly, there was a marked increase in tumour vascularisation in bFGF-treated samples.

 Conclusion:

This new evidence indicates that FGF signalling does play an important role in osteoblast transformation and the pathogenesis of OS. Furthermore, the first steps have been taken in developing a highly manipulatable in ovo tumour culture system. This can be further developed to study the effects of modulating other exogenous factors on tumour growth and survival.