Download Tumor Cells Outside of the Local Bone Marrow Contribute to

Tumor Cells Outside of the Local Bone Marrow Contribute to Generalized Bone Loss
1
Edwards, CM; 2Fowler, J; 2Ruppender, N; 2Sterling, J; 1Lwin, ST; 2Johnson, J; 2Hart, A; 2Mundy, GR; +1Edwards, JR
+1University of Oxford, Oxford, UK, 2Vanderbilt University Medical Centre, Nashville, TN
[email protected]
INTRODUCTION:
The production and sustained release of ectopic hormones by cancer
cells, induce striking systemic effects in tissues distant to the tumor site.
For example, untreated breast cancer patients develop decreased Bone
Mineral Density (BMD) leading to increased vertebral fractures,
compared to healthy individuals1, and untreated melanoma patients
without skeletal metastases have increased skeletal-related disorders
(including accelerated osteoporosis and arthritis) than healthy
individuals2.
Despite the absence of myeloma cells within the bone, uCT analysis
demonstrated a 23% reduction in trabecular bone volume/total volume
(BV/TV), and decreased vBMD and mBMD in mice bearing
plasmacytomas compared with non-tumor controls (p<0.05),
accompanied by a significant increase in trabecular separation.
Figure 3. Myeloma cells outside of bone decrease bone volume.
5TGM1 cells injected s.c. lead to decreased BV/TV and increased
trabecular spacing (*p<0.05)
Figure 1. Tumor-Bone Interactions. Tumor cells metastasize to bone
and activate osteoclastic resorption, fueling tumor proliferation and
localized osteolysis. Tumor cells distant to bone may also affect bone
mass.
Based on these clinical observations, we hypothesized that tumors at
locations distant to bone may result in a generalized bone loss.
In addition, melanoma s.c. tumors resulted in a 20% decrease in BV/TV,
along with decreased vBMD, mBMD and trabecular number, thickness
and increased separation, while untreated bones in the intra-tibial MDAMB-231 model showed a 47% decrease in BV/TV accompanied by
decreased trabecular number, thickness and increased separation, along
with decreased vBMD and mBMD compared to non-tumor bearing
animals (p<0.01).
METHODS:
To investigate this we employed well-established murine tumor
models of melanoma, breast cancer and multiple myeloma, to induce
tumors at sites distant to the assessed region of bone. All in vivo models
conformed to national and institutional IACUC approved guidelines.
Bone volume was analysed by uCT scanning and histomorphometric
analysis. Subcutaneous (s.c.) tumor growth was measured daily and
tumor growth in bone determined by GFP fluorescence and histology.
The 5TGM1 myeloma tumor burden was assessed by serum IgG2κ
paraprotein levels. Urinary markers of bone resorption were also
examined and dual-label fluorescent imaging used to assess bone
formation rates (BFR). Statistical significance was determined using a
students t-test with p values less than 0.05 considered significant.
RESULTS:
Intravenous inoculation of 5TGM1 cells resulted in myeloma bone
disease, with homing of myeloma cells to bone, osteolytic bone lesions,
increased osteoclast number and decreased trabecular bone and BFR. In
contrast, s.c. inoculation resulted in a time-dependent growth of a
plasmacytoma, accompanied by a significant increase in serum IgG2κ
levels. Flow cytometric analysis detected no significant increase in
GFP+ cells within the marrow, demonstrating that myeloma cells
inoculated s.c. do not home to the bone marrow.
Figure 4. Breast cancer (Top) and Melanoma (Bottom) induce
generalized bone loss. Tumor cells outside of the skeletal regions
analyzed resulted in decreased BV/TV, BMD and trabecular thickness
(*p<0.05,**p<0.01).
DISCUSSION:
Our data demonstrate that myeloma, melanoma and breast cancer
cells induce generalized bone loss, providing evidence for the
development of cancer-induced osteoporosis from tumors at sites distant
to bone.
SIGNIFICANCE:
With increasing detection and treatment options, cancer suffers are
generally surviving to increased ages. However, the systemic, long-term
effects of tumor on the body are poorly understood. The significance of
these findings lies in the demonstration that even without skeletal
metastases, bone mass can be markedly reduced by the presence of
tumors outside of the skeleton.
Figure 2. Myeloma cells grow outside of bone. 5TGM1 myeloma cells
injected s.c proliferate (A) and release IgG2k paraprotien (B). Myeloma
cells were not detected in the bone marrow (C).
REFERENCES:
1. Kanis JA, McCloskey EV, et al. A high incidence of vertebral fracture
in women with breast cancer. Br J Cancer. 1999 Mar;79(7-8):1179-81.
2. Stava C, Beck M, et al. Health profiles of 996 melanoma survivors:
the M. D. Anderson experience. BMC Cancer. 2006 Apr 18;6:95.
Paper No. 0270 • ORS 2012 Annual Meeting