2002 CTOS Annual Meeting Posters — Biology

HUMAN BREAST CANCER CELLS MODULATE THE SURVIVAL AND ACTIVITY OF OSTEOBLASTS
[Abstract ID: 36]

Category: Biology

Authors: Matthew J. Allen¹, Sheila A. Moore¹, Timothy A. Damron¹

Author Institutions: ¹SUNY Upstate Medical University at Syracuse, New York, United States

Presenter: Matthew J. Allen
allenm@mail.upstate.edu

Correspondent: Timothy A. Damron
tdamron@twcny.rr.com
Syracuse New York United States 13202
Ph: 315-464-4472
Fax: 315-464-4664

Objectives: Breast cancer lytic metastases are known to be mediated in part via osteoclast activity. However, we hypothesized that osteoblast inhibition may be an additional contributor to bone loss in this setting. The specific aim was to determine whether soluble factors released from tumor cells are capable of influencing osteoblast growth or synthetic activity.

Methods: Human breast cancer MDA-MB-435 cells were cultured to confluence. Confluent cells were exposed to serum-free medium to create a tumor-conditioned medium (CM) which was centrifuged and filtered. The conditioned medium was diluted to 0, 0.1, 1, 5, 10 or 20% (v/v) and added to cultured murine MC3T3-E1 osteoblasts. Specimens were analyzed for MTT, alkaline phosphatase (ALP), lactase dehydrogenase, caspase, and mineralization.

Results: Tumor conditioned medium inhibited ALP activity in cultured osteoblasts. This inhibitory effect was observed even at very low concentrations of CM (0.1% v/v). MTT data indicated proliferation of osteoblasts was stimulated in dose-dependent fashion by the addition of conditioned medium. Conditioned medium also induced a marked increase in apoptosis and cytotoxicity at concentrations of 5% or greater. No effect on mineralization was seen.

Conclusions: These data confirm our hypothesis that soluble factors released by tumor cells are capable of modulating growth and synthetic activity of osteoblasts. Although we expected osteoblastic growth inhibition by CM, increased proliferation in response to CM was seen. We hypothesize that breast cancer cells stimulate osteoblast proliferation to recruit and activate osteoclasts while inhibiting osteoblast synthetic machinery, further tipping the scales toward osteolysis. This pathway provides a potential target for therapeutic intervention.