IGF-I secretion by prostate carcinoma cells does not alter tumor-bone cell interactions in vitro or in vivo.

Background: IGF-I is an important growth and differentiative factor for osteoblasts and may have a role in defining prostate cancer risk and skeletal metastases.

Methods: Conditioned media (CM) from human prostate cancer (PC), C4-2 and C4-2B, which produce osteoblastic lesions, and PC-3, which causes osteolysis, was added to MC3T3-E1 bone cultures. SCID mice were injected intratibially with these engineered cells. Tumor bearing tibiae were analyzed by microCT and pQCT.

Results: CM from PC cells increased osteoblast proliferation and differentiation and was unaltered by the type of PC cell, IGF-I antibodies, or exogenous IGF-I and IGFBP2. Study of intratibial PC tumors in SCID mice showed that C4-2 cells grew slowly preserving bone structure, while PC-3 tumors caused rapid osteolysis. Overexpression of IGF-I did not change either tumor progression or skeletal response.

Conclusions: IGF-I is neither necessary nor sufficient for the osteoblastic response to PC metastases.