Mechanism for bone invasion of oral cancer cells mediated by interleukin-6 in vitro and in vivo.
BACKGROUND
Osteoclastic bone resorption is an important step in bone invasion in several malignancies. Although interleukin (IL)-6 accelerates osteoclastic bone resorption, it remains unclear whether IL-6 may be involved in bone invasion of oral cancer.


METHODS
The pit formation assay with calf femur-derived bone slices was performed to examine the bone-resorbing activity of osteoclasts and cancer cells. The chemotaxis activity of the culture media was analyzed by the use of Boyden chamber technique. Nude mice, which were inoculated with IL-6-producing oral cancer cells into masseter, were treated with anti-IL-6 neutralizing antibody, and mandibular-bone invasion of the cells was assessed.


RESULTS
BHY, a bone-invasive oral cancer cell line, but not HNT, a noninvasive cell line, produced large amounts of IL-6. In a pit formation assay, addition of conditioned medium (CM) derived from BHY but not HNT increased osteoclastic bone resorption, and the effects were inhibited by anti-IL-6 antibody. BHY-secreted IL-6 showed significant chemotaxis activity for osteoclasts. Of note, CM from the cocultivation of osteoclasts and BHY markedly enhanced the cancer cell migration, and the chemotaxis activity was significantly reduced when anti-IL-6 antibody was added into the coculture and then CM were collected, but not when the antibody was added into the CM after they were collected. Furthermore, treatment with anti-IL-6 antibody almost completely inhibited mandibular bone invasion of BHY in nude mice.


CONCLUSIONS
These results strongly suggest that IL-6 secreted by oral cancer cells plays a significant role in bone invasion.
Okamoto
M
M
Second Department of Oral and Maxillofacial Surgery, Tokushima University School of Dentistry, Tokushima, Japan. mokamoto@dent.tokushima-u.ac.jp
Hiura
K
K
Ohe
G
G
Ohba
Y
Y
Terai
K
K
Oshikawa
T
T
Furuichi
S
S
Nishikawa
H
H
Moriyama
K
K
Yoshida
H
H
Sato
M
M
D000818:Animals; D001859:Bone Neoplasms / Q000473:pathology; D001862:Bone Resorption; D018196:Carcinoma, Adenosquamous / Q000378:metabolism / Q000473:pathology*; D002294:Carcinoma, Squamous Cell / Q000378:metabolism / Q000473:pathology*; D002633:Chemotaxis; D018920:Coculture Techniques; D017077:Culture Media, Conditioned; D006801:Humans; D015850:Interleukin-6 / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D008339:Mandibular Neoplasms / Q000473:pathology*; D051379:Mice; D008819:Mice, Nude; D009062:Mouth Neoplasms / Q000378:metabolism / Q000473:pathology*; D009361:Neoplasm Invasiveness; D010010:Osteoclasts / Q000378:metabolism / Q000502:physiology*; D012333:RNA, Messenger / Q000032:analysis; D011817:Rabbits; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014407:Tumor Cells, Cultured
D017077:Culture Media, Conditioned; D015850:Interleukin-6; D012333:RNA, Messenger