Although some tumors cause osteolytic lesions, there are some that sti
mulate new bone formation. This is an important phenomenon because the
responsible mechanisms probably represent an aberration of normal phy
siological bone formation, and identifying the factors involved in the
process may lead to new therapies for various bone diseases. To clari
fy our understanding of the potential mechanism responsible, we compar
ed and quantitated the extent of new bone formation stimulated by huma
n tumors (HeLa, Hep-2, AV-3, FL, WISH and KB), some of which have oste
ogenic activity in vivo [2]. Tumor cells were injected over the calvar
ia of nude mice to examine formation of new bone. The tumor cells prod
uced three histologically distinct patterns of new bone growth: (1) WI
SH and KB stimulated appositional bone growth adjacent to periosteal b
one surfaces; (2) HeLa and Hep2 induced new bone growth over calvarial
surface even when distant from the tumor mass; (3) FL stimulated bone
formation adjacent to periosteum as well as ectopic bone formation in
sites distant from bone. All tumors except AV3 induced mean new bone
thickness >100 mu m, and Hep-2 cells produced bone 330 mu m thick. PCR
and Northern blot analysis of mRNA isolated from cultured tumor cells
revealed that all cell lines expressed mRNA for TGF beta, (fibroblast
growth factor) FGF-1, FGF-2, and IGF-I, and most cell lines produced
mRNA for PDGF. Only FL expressed large amounts of mRNA for BMP2. In se
rum-free conditioned media from Hep2 and HeLa cells purified by hepari
n affinity chromatography, we have identified FGF-1, FGF-2, and PDGF b
y immunodetection with specific antibodies. Our results show that new
bone growth caused by these tumors is likely due to the production of
bone growth factors by the tumor cells, and that the overall effects o
n bone may be due to several factors working in concert.