Abstract P2-02-03: The Collagen Receptor Endo180: A Metastatic Plasma Marker In Breast Cancer Modulated By Bisphosphonate Treatment

Purpose: To establish whether the collagen remodelling receptor, Endo180, should be given consideration as a useful plasma marker in metastatic breast cancer.

Patients and Methods: Analysis of MCF-7 and MDA-MB-231 cell conditioned medium validated the anti-human (39.10) monoclonal antibody as suitable for the detection of soluble Endo180 in plasma. Eighty-seven breast cancer patients with early primary, locally advanced and metastatic disease were included in the study. Correlations between Endo180, CA 15–3 antigen (MUC1; mucin 1) and bisphosphonate treatment were investigated.

Results: Endo180 was elevated in metastatic compared to early breast cancer (P <.0001) and was able to differentiate locoregional disease and visceral and/or osseous metastasis (P = .0005). In combination CA 15–3 antigen (cut-off: 28 U/mL) and Endo180 (relative plasma level cut-off range: 0.95–1.65) had sensitivity of 94–97% and specificity of 52–68%. Endo180 levels were significantly higher in patients who were treatment naive (2.17 ± 0.82, N = 13) compared to those previously (1.82 ± 0.33, N = 5) or currently (1.37 ± 0.74, N = 24) receiving bisphosphonates (P = .011). In the bisphosphonate naive setting (N = 57) the combination of Endo180 (relative plasma level cut-off range: 0.95–1.65) and CA 15–3 antigen (cut-off: 28 U/mL) had a sensitivity of 87–92% and specificity of 72–79%.

Conclusion: Endo180 is a plasma marker with high sensitivity in metastatic breast cancer that can be modulated by bisphosphonate treatment.

Citation Information: Cancer Res 2012;72(24 Suppl):Abstract nr P2-02-03.

The influence of mechanical stimulation on osteocyte apoptosis and bone viability in human trabecular bone

It has been shown previously using in vivo and ex vivo animal models, that cyclical mechanical stimulation is capable of maintaining osteocyte viability through the control of apoptotic cell death. Here we have studied the effect of mechanical stimulation on osteocyte viability in human trabecular bone maintained in a 3-D bioreactor system. Bone samples, maintained in the bioreactor system for periods of 3, 7 and 27 days, were subjected to either cyclical mechanical stimulation which engendered a maximum of 3,000 microstrain in a waveform corresponding to physiological jumping exercise for 5 minutes daily or control unloading. Unloading resulted in a decrease in osteocyte viability within 3 days that was accompanied by increased levels of cellular apoptosis. Mechanical stimulation significantly reduced apoptosis (p< or =0.032) and improved the maintenance of osteocyte viability in bone from all patient samples. The percentage Alkaline Phosphatase (ALP) labelled bone surface was significantly increased (p< or =0.05) in response to mechanical stimulation in all samples as was the Bone Formation Rate (BFR/BS) (p=0.005) as determined by calcein label incorporation in the 27-day experiment. These data indicate that in this model system, mechanical stimulation is capable of maintaining osteocyte viability in human bone.

Fas/CD95 is associated with glucocorticoid-induced osteocyte apoptosis

Prolonged use of glucocorticoids is associated with decreased bone formation, increased resorption and osteonecrosis, through direct and indirect effects on the activity and viability of bone effector cells, osteoblasts and osteoclasts, and osteocytes. This study has investigated molecular pathways implicated in Dexamethasone-induced apoptosis of osteocytes, using a cell line and primary chicken cells. MLO-Y4 osteocytes were pre-treated with several bisphosphonates representing a range of anti-resorptive activities and conformation/structure relationships, and were subsequently challenged with Dexamethasone. Apoptotic cells were detected at various times after treatment using morphological and biochemical criteria. Dex was shown to induce apoptosis associated with the Fas/CD95 death receptor and in a caspase 8 dependent manner. The apoptotic response was inhibited by all variants of the BP molecules, including those with reduced anti-resorptive activity, indicating that Dex-induced apoptosis is independent of anti-osteoclastic activity. Dex-induced apoptosis was associated with a transient increase in phosphorylated ERK 1/2 and was blocked by the ERK inhibitor UO126. In addition, both UO126 and BPs decreased localization of Fas to the cell membrane. ERK activation by PMA did not induce death or Fas upregulation, suggesting that Fas may be important for the induction of apoptosis and the existence of an additional factor activated by Dex which enables the cooperation between the Dex-activated ERK and Fas pathways, during apoptosis of osteocytes. Furthermore, upregulation of death and Fas was not accompanied by upregulation of FasL, pointing to the possible existence of FasL-independent Fas-associated death in these cells.