2-methoxyestradiol-mediated anti-tumor effect increases osteoprotegerin expression in osteosarcoma cells.
Osteosarcoma is a bone tumor that frequently develops during adolescence. 2-Methoxyestradiol (2-ME), a naturally occurring metabolite of 17beta-estradiol, induces cell cycle arrest and cell death in human osteosarcoma cells. To investigate whether the osteoprotegrin (OPG) protein plays a role in 2-ME actions, we studied the effect of 2-ME treatment on OPG gene expression in human osteosarcoma cells. 2-ME treatment induced OPG gene promoter activity and mRNA levels. Also, Western blot analysis showed that 2-ME treatment increased OPG protein levels in MG63, KHOS, 143B and LM7 osteosarcoma cells by 3-, 1.9-, 2.8-, and 2.5-fold, respectively, but did not affect OPG expression in normal bone cells. In addition, increases in OPG protein levels were observed in osteosarcoma cell culture media after 3 days of 2-ME treatment. The effect of 2-ME on osteosarcoma cells was ligand-specific as parent estrogen, 17beta-estradiol and a tumorigenic estrogen metabolite, 16alpha-hydroxyestradiol, which do not affect osteosarcoma cell cycle and cell death, had no effect on OPG protein expression. Furthermore, co-treating osteosarcoma cells with OPG protein did not further enhance 2-ME-mediated anti-tumor effects. OPG-released in 2-ME-treated cultures led to an increase in osteoblastic activity and a decrease in osteoclast number, respectively. These findings suggest that OPG is not directly involved in 2-ME-mediated anti-proliferative effects in osteosarcoma cells, but rather participates in anti-resorptive functions of 2-ME in bone tumor environment.
Benedikt
Michaela B
MB
Department of Orthopedics, College of Medicine, Mayo Clinic, Rochester, Minnesota 55905, USA.
Mahlum
Eric W
EW
Shogren
Kristen L
KL
Subramaniam
Malayannan
M
Spelsberg
Thomas C
TC
Yaszemski
Michael J
MJ
Maran
Avudaiappan
A
D000077584:2-Methoxyestradiol; D000469:Alkaline Phosphatase / Q000378:metabolism; D000818:Animals; D016923:Cell Death / Q000187:drug effects; D049109:Cell Proliferation / Q000187:drug effects; D004354:Drug Screening Assays, Antitumor; D004958:Estradiol / Q000031:analogs & derivatives* / Q000494:pharmacology; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects; D006801:Humans; D010006:Osteoblasts / Q000166:cytology / Q000187:drug effects / Q000201:enzymology; D053244:Osteoprotegerin / Q000235:genetics / Q000378:metabolism*; D012516:Osteosarcoma / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D010455:Peptides / Q000494:pharmacology; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D051381:Rats; D014158:Transcription, Genetic / Q000187:drug effects
D053244:Osteoprotegerin; D010455:Peptides; D012333:RNA, Messenger; D004958:Estradiol; D000077584:2-Methoxyestradiol; D000469:Alkaline Phosphatase