Tumor-bone interaction induced by transplantable human tumors in nude mice

Human breast cancer induces osteoclast activation and increases the number of osteoclasts at sites of tumor osteolysis

The cellular mechanism through which osseous breast cancer metastases induce the focal destruction of bone (tumor osteolysis) is unknown. An athymic mouse model designed for the study of tumor osteolysis was developed and the influence of two human breast cancer tumors on bone was studied. Tumor-induced osteolysis occurred between 7 and 10 weeks after inoculation of mouse femora with MDA-MB-231 or MDA-MB-435s breast cancer cells. An increase in osteoclast number and an increase in osteoclast size (area) were detected when tumor-bearing and sham-injected limbs were compared. In vitro analysis of the influence of the tumor-conditioned medium on osteoclast-mediated bone resorption revealed that this conditioned medium stimulated the resorption by increasing both the number of osteoclasts bound to bone and the number of bone resorption pits formed per osteoclast. In addition, in vitro analysis of the influence of breast cancer tumor cells on osteoclast formation or survival, or both, demonstrated that breast cancer cells induced a dramatic increase in the number of osteoclasts detected in culture. Taken in total these findings suggest that human breast cancer tumors induce osteolysis by enhancing osteoclast adherence to bone, stimulating osteoclast-mediated bone resorption and either prolonging the survival of osteoclasts or increasing osteoclast formation.

Localized, tumor-associated osteolysis involves the recruitment and activation of osteoclasts

The cellular and biochemical mechanisms that direct destruction of bone at the site of tumor osteolysis are unknown. In order to understand this process better, a murine model designed for the study of tumor osteolysis was developed and the influence of osteolytic and nonosteolytic tumors on bone was investigated. Tumors developed following femoral intramedullary injection of sarcoma (2472) and melanoma (G3.26) cell lines; however, only tumors from the 2472 cell line caused osteolysis. It was determined that 2472 tumor-induced osteolysis commenced 6 days after the femora had been inoculated with 2472 cells. There were more osteoclasts per millimeter of bone surface in 2472 tumor-bearing limbs (16.7 +/- 5.0) than in sham-injected limbs (3.8 +/- 0.9) (p < 0.015). In addition, an increase in the osteoclast size (area) was detected in 2472 tumor-bearing limbs: 412 +/- 65 micron2 compared with 187 +/- 17 micron2 (p < 0.01). In vitro bone resorption experiments indicated that 2472 tumor cells had a limited ability to destroy bone in comparison with macrophages and osteoclasts. Taken in total, these findings define a model that is useful for the study of tumor osteolysis, and the data from analyses of the model demonstrate that the cellular mechanisms responsible for 2472 tumor-induced osteolysis include both an increase in the number of osteoclasts and activation of mature osteoclasts.

Inhibition by a new bisphosphonate (YM175) of bone resorption induced by the MBT-2 tumour of mice

A new bisphosphonate, disodium dihydrogen (cycloheptylamino) methylene bisphosphonate monohydrate (YM175), was compared with 3-amino-1-hydroxypropylidene-1, 1-bisphosphonate (AHPrBP) and 1-hydroxyethylidene-1,1-bisphosphonate (HEBP) in terms of its effect on tumour induced osteolysis using a bladder tumour in mice (MBT-2). The method consisted of inoculating tumour cells subcutaneously (SC) over the calvaria in mice, resulting in a local tumour causing fragmentation of the bone. The compounds were active not only when administered preventively before establishment of bone resorption, but also in an inhibitory fashion once the variables were already under the influence of the tumour. This osteolysis was evaluated by measuring the increased area of bone resorption in reduced opacity to radiograph and histology. The results showed the following sequence of potency: YM175 > AHPrBP = HEBP. This inhibition was obtained with no apparent effect on the growth of the MBT-2 tumour. YM175 appears to be an interesting new bisphosphonate with possible clinical application.

Response of MBT-2 bladder carcinoma-induced osteolysis to various agents

Tumor-bone interactions were experimentally studied using a bladder tumor in mice (MBT-2). The method consisted of subcutaneously inoculating tumor cells over the calvaria in nude mice after the periosteum was disrupted. This resulted in a local tumor that caused fragmentation of the bone. Bone destruction was found to increase in proportion to the number of osteoclasts in the earlier phase. The osteoclasts decreased in number when the tumors had grown large enough to envelop the residual bone. However, bone destruction continued and seemed to be mediated by the tumor cells by a mechanism that did not involve the osteoclasts. The effects of several agents were investigated in this model. High doses of calcitonin and cyclosporine reduced the bone resorption, and these agents may be effective in the early phase of bone destruction. A bisphosphonate derivative (AHBuBP) inhibited bone resorption markedly in the early and late phases of bone destruction. Autoradiography using carbon 14 (14C)-labeled AHBuBP showed that the isotope was concentrated at the surface of the bone adjacent to the MBT-2 tumors. These results suggest that bisphosphonates may make bone less susceptible to the actions of osteoclasts and tumor cells.

Inhibition by a new bisphosphonate (AHBuBP) of bone resorption induced by the MBT-2 tumor of mice

A new bisphosphonate, 4-amino-1-hydroxybuthylidene-1,1-bisphosphonate (AHBuBP), was compared with 3-amino-1-hydroxypropylidene-1,1-bisphosphonate (AHPrBP) and 1-hydroxyethylidene-1,1-bisphosphonate (HEBP) in terms of its effect on tumor-induced osteolysis using a bladder tumor in mice (MBT-2). Tumor cells were inoculated subcutaneously (SC) over the calvaria in mice, resulting in a local tumor causing fragmentation of the bone. The tumor-induced osteolysis associated with osteoclasts proliferation was accompanied with reactive new bone formation. This osteolysis was evaluated by measuring the increased area of bone resorption in reduced opacity to radiograph and histologic study. The results showed the following sequence of potency: AHBuBP greater than AHPrBP = HEBP. This inhibition was obtained with no apparent effect on the growth of the MBT-2 tumor. The authors conclude that AHBuBP appears to be an interesting new bisphosphonate with possible clinical application.

Effects of a new bisphosphonate (AHBuBP) on osteolysis induced by human prostate cancer cells in nude mice

A new bisphosphonate, 4-amino-1-hydroxybutylidene-1, 1-bisphosphonate (AHBuBP), was compared with 3-amino-1-hydroxypropylidene-1, 1-bisphosphonate (AHPrBP) and 1-hydroxyethylidene-1, 1-bisphosphonate (HEBP) assessing their effects on tumor induced osteolysis using human prostate adenocarcinoma cells in nude mice. The method consisted of inoculating transplantable human prostate cancer cells subcutaneously over the calvaria in nude mice resulting in a local tumor causing fragmentation of the bone. The parameters included assessing the extent of decreased osteolysis in bone as judged by X-ray and histological examination. The results showed the following sequence of potency: AHBuBP greater than AHPrBP greater than HEBP. The compounds were active not only when administered preventively before establishment of bone resorption, but also in an inhibitory fashion once the variables were already under the influence of the tumor. This inhibition was obtained with no apparent effect on the growth of the tumor. AHBuBP appears to be an interesting new bisphosphonate for future clinical use.