Objectives: Hormone-independent and cytotoxic drug-resistant tumor growth in osteoblastic metastases defines poor survival in patients with advanced prostate cancer. Therefore, we analyzed the ability of human osteoblast-like cells (MG-63 cells) and MG-63 conditioned media (MG-63 CM) to protect PC-3 human prostate cancer cells from adriamycin cytotoxicity in vitro.
Methods: Adriamycin cytotoxicity was assessed in MG-63 osteoblast-like and PC-3 prostate cancer monolayer and three-dimensional collagen coculture systems using the DNA content and trypan blue exclusion assays, analysis of indexes of cell cycle by flow cytometry, determination of DNA fragmentation on simple agarose gel and terminal deoxynucleotidyl transferase-mediated nick end labeling (TUNEL) assay, and immunocytochemistry.
Results: Adriamycin (100 nM) arrested both the PC-3 and MG-63 cells at the G2/M phase in the cell cycle but induced apoptosis only in PC-3 cells, as assessed by flow cytometry, trypan blue exclusion, and agarose gel. Optimal doses of MG-63 CM (50 microg/mL), insulin-like growth factor I (50 ng/mL), and transforming growth factor-beta-1 (25 ng/mL), as determined by DNA content assay, partially neutralized the adriamycin cytotoxicity of PC-3 cells detected by flow cytometry and trypan blue exclusion. In addition, MG-63 cells rescued PC-3 cells from adriamycin apoptosis in the three-dimensional type I collagen gel coculture system, as analyzed by TUNEL assay.
Conclusions: These data suggest that osteoblast-like cells and osteoblast-derived growth factors can optimize survival of metastatic prostate cancer cells, thereby helping to develop cytotoxic drug-resistant growth in vitro.