The Relationship between Urinary Pyridinoline, Deoxypyridinoline and Bone Metastasis in a Rat Breast Cancer Model

Humanised xenograft models of bone metastasis revisited: novel insights into species-specific mechanisms of cancer cell osteotropism

The determinants and key mechanisms of cancer cell osteotropism have not been identified, mainly due to the lack of reproducible animal models representing the biological, genetic and clinical features seen in humans. An ideal model should be capable of recapitulating as many steps of the metastatic cascade as possible, thus facilitating the development of prognostic markers and novel therapeutic strategies. Most animal models of bone metastasis still have to be derived experimentally as most syngeneic and transgeneic approaches do not provide a robust skeletal phenotype and do not recapitulate the biological processes seen in humans. The xenotransplantation of human cancer cells or tumour tissue into immunocompromised murine hosts provides the possibility to simulate early and late stages of the human disease. Human bone or tissue-engineered human bone constructs can be implanted into the animal to recapitulate more subtle, species-specific aspects of the mutual interaction between human cancer cells and the human bone microenvironment. Moreover, the replication of the entire "organ" bone makes it possible to analyse the interaction between cancer cells and the haematopoietic niche and to confer at least a partial human immunity to the murine host. This process of humanisation is facilitated by novel immunocompromised mouse strains that allow a high engraftment rate of human cells or tissue. These humanised xenograft models provide an important research tool to study human biological processes of bone metastasis.

Orthotopic model of canine osteosarcoma in athymic rats for evaluation of stereotactic radiotherapy

OBJECTIVE

To develop an orthotopic model of canine osteosarcoma in athymic rats as a model for evaluating the effects of stereotactic radiotherapy (SRT) on osteosarcoma cells.

ANIMALS

26 athymic nude rats.

PROCEDURES

3 experiments were performed. In the first 2 experiments, rats were injected with 1 × 10(6) Abrams canine osteosarcoma cells into the proximal aspect of the tibia (n = 12) or distal aspect of the femur (6). Tumor engraftment and progression were monitored weekly via radiography, luciferase imaging, and measurement of urine pyridinoline concentration for 5 weeks and histologic evaluation after euthanasia. In the third experiment, 8 rats underwent canine osteosarcoma cell injection into the distal aspect of the femur and SRT was administered to the affected area in three 12-Gy fractions delivered on consecutive days (total radiation dose, 36 Gy). Percentage tumor necrosis and urinary pyridinoline concentrations were used to assess local tumor control. The short-term effect of SRT on skin was also evaluated.

RESULTS

Tumors developed in 10 of 12 tibial sites and all 14 femoral sites. Administration of SRT to rats with femoral osteosarcoma was feasible and successful. Mean tumor necrosis of 95% was achieved histologically, and minimal adverse skin effects were observed.

CONCLUSIONS AND CLINICAL RELEVANCE

The orthotopic model of canine osteosarcoma in rats developed in this study was suitable for evaluating the effects of local tumor control and can be used in future studies to evaluate optimization of SRT duration, dose, and fractionation schemes. The model could also allow evaluation of other treatments in combination with SRT, such as chemotherapy or bisphosphonate, radioprotectant, or parathyroid hormone treatment.

Rat models of bone metastases

Bone metastases occur frequently in patients with advanced breast or prostate cancer. Bone metastases can be predominantly osteolytic, osteoblastic or mixed. Studies with animal models allow advances in understanding the molecular basis for bone metastases and provide new targets for therapy. Several animal models have been developed in rat with different pathophysiologies; they required injection or implantation of neoplastic cells into orthotopic locations, bones or the left ventricle of the heart. Several specific strains of rat have an increased incidence of spontaneous tumors. Carcinomas can be induced by either chemicals or physical agents. However, the most used and convenient way to induce bone metastases is a syngeneic transmission. MAT-Ly-Lu cells have been used in several models using Copenhagen rats to induce osteoblastic bone lesions. PA-III cells derived from Pollard tumors can also produce a combination of osteolytic and osteoblastic reactions at the site of transplantation. Osteolytic bone lesions can be obtained with an injection of Walker cells. The use of 13762 or c-SST2 cells allows also leads to osteolysis. Human xenografts can only be used in nude animals. It is essential to validate and correctly interpret the lesions in several models of bone metastasis. No animal model is sufficient by itself to represent the clinical findings observed in humans. The use of models developed in different species should be more predictive and bring a beam of arguments for a better knowledge of pathophysiological and therapeutic mechanisms.

Inhibition of bone metastasis from breast cancer with pamidronate resulting in reduction of urinary pyridinoline and deoxypyridinoline in a rat model

BACKGROUND

Breast cancers frequently metastasize to bone, in a process in which osteoclasts play a major role. Bisphosphonate pamidronate, a specific inhibitor of osteoclasts, has been widely used in the treatment of bone metastasis (BM). In this study, using an animal model of BM, we examined the prophylactic and treatment effects of pamidronate against BM and clarified the relationships between BM, pamidronate and bone resorption markers such as urinary pyridinoline and deoxypyridinoline.

METHODS

Bone metastases were established by inoculating c-SST-2 (spontaneously developed rat mammary adenocarcinoma) cells into the thoracic aorta of 27 rats, which were then divided into three groups of rats: the untreated control group, the pre-treatment group, consisting of rats treated with pamidronate (10 mg/kg) injected subcutaneously a day before tumor inoculation, and the post-treatment group, in which rats were injected with pamidronate a week after tumor inoculation. Three weeks after tumor inoculation, blood and urine samples were collected. The subjects were then sacrificed to harvest the thoracic and lumbar vertebrae for histological examination, consisting of staining with hematoxylin and eosin and tartrate resistant acid phosphatase (TRACP).

RESULTS

The incidence of BM was 70.0%, 44.4% and 37.5% in the control, pre-treatment and post-treatment groups, respectively. Although there was no significant difference among the groups, the rate of BM in the treated groups was lower than that of the control group and no bone destruction was observed in treated rats. The TRACP-stained specimens revealed that there were numerous osteoclasts contributing to the control group tumor burden. The urinary levels of pyridinoline and deoxypyridinoline were reduced by pamidronate.

CONCLUSION

Our results suggest that pamidronate prevents the development of BM and the destruction of bone associated with BM. Maintaining the values of Pyr and Dpyr at low levels with pamidronate might lead to inhibition of the incidence and development of BM.

SU11248 inhibits tumor growth and CSF-1R-dependent osteolysis in an experimental breast cancer bone metastasis model

The aim of the study was to investigate inhibitory effects of the receptor tyrosine kinase (RTK) inhibitor SU11248 against CSF-1R and osteoclast (OC) formation. We developed an in vivo model of breast cancer metastasis to evaluate efficacy of SU11248 against tumor growth and tumor-induced osteolysis in bone. The in vitro effects of SU11248 on CSF-1R phosphorylation, OC formation and function were evaluated. Effects on 435/HAL-Luc tumor growth in bone were monitored by in vivo bioluminescence imaging (BLI), and inhibition of osteolysis was evaluated by measurement of serum pyridinoline (PYD) concentration and histology. Phosphorylation of the receptor for M-CSF (CSF-1R) expressed by NIH3T3 cells was inhibited by SU11248 with an IC50 of 50-100 nM, consistent with CSF-1R belonging to the class III split kinase domain RTK family. The early M-CSF-dependent phase of in vitro murine OC development and function were inhibited by SU11248 at 10-100 nM. In vivo inhibition of osteolysis was confirmed by significant lowering of serum PYD levels following SU11248 treatment of tumor-bearing mice (P = 0.047). Using BLI, SU11248 treatment at 40 mg/kg/day for 21 days showed 64% inhibition of tumor growth in bone (P = 0.006), and at 80 mg/kg/day showed 89% inhibition (P = 0.001). Collectively, these data suggest that SU11248 may be an effective and tolerated therapy to inhibit growth of breast cancer bone metastases, with the additional advantage of inhibiting tumor-associated osteolysis.

Biochemical markers of bone metabolism in animals: uses and limitations

Routine assessment of the skeleton's response to disease and injury traditionally has consisted of plain-film radiography supplemented with advanced imaging techniques, such as computed tomography, magnetic resonance imaging, nuclear scintigraphy, and bone densitometry. Although these techniques provide increased sensitivity as compared with radiography, they still are limited by the fact that they can only document the net results of past skeletal activity. In contrast, serum and urinary biomarkers of bone formation and resorption provide near real-time information about bone cell activity. In this review, I describe the scientific rationale behind the use of these markers in humans and detail the efforts that have been made to adapt this technology to veterinary medicine and animal research. Commercial assay kits that are applicable to different animal species are described, and the potential limitations of the technology are discussed. The goal of this review is to provide clinical pathologists and researchers with the information needed to decide whether the use of bone markers is likely to be helpful and to select the most appropriate marker (or panel of markers) to answer a particular question.

Follow-up of collagen crosslink excretion in patients with oral squamous cell carcinoma and analysis of tissue samples

The presence of an oral squamous cell carcinoma (OSCC) may be associated with increased urinary excretion of the markers of collagen degradation, hydroxylysylpyridinoline (HP) and lysylpyridinoline (LP). We investigated the possibility of these markers predicting the presence of active disease. Patients from a current study on HP and LP were included as follows: Group 1a (OSCC with confirmed mandibular bony infiltration, n=12), group 1b (group 1a patients >6 months after successful treatment), group 2a (OSCC without evidence of mandibular bone infiltration, n=8), group 2b (group 2a patients >6 months after successful treatment), group 3a (recurrent OSCC, n=8), group 3b (group 3a patients >6 weeks later, symptoms unchanged) and group 4 (control group, n=74). Tissue samples from tumour tissue and adjacent healthy mucosa were additionally investigated for HP and LP concentrations (n=8). The decrease in the urinary concentrations of HP and LP was statistically significant between groups 1a and 1b (P<0.001 for HP and LP), but not between groups 2a and 2b (P=0.07 for HP and LP), while values in groups 1b and 2b were within the normal range. When comparing groups 3a and 3b, a significant increase was observed for LP (P=0.050), but not HP (P=0.208). In conclusion, successful treatment of OSCC with bony involvement may be associated with a reduction of urinary HP and LP, whereas ongoing disease may result in an increase of LP. HP and LP may both be useful markers of tumour progression in patients with OSCC.

Differential enhancement of collagen crosslink excretion in cases of osteosarcoma and chondrosarcoma

Hydroxylysylpyridinoline (HP) and lysylpyridinoline (LP) are markers of collagen absorption and LP is specific for collagen type I in bone. In the present study we evaluated the concentration of HP and LP in urine of patients with osteosarcoma ( n=20; age range 16-49 years) and chondrosarcoma ( n=15; age range 18-70 years). The values were compared with those obtained from 74 healthy controls (age range 16-83 years). The range and upper limit of normal values (HP(max) and LP(max)) were measured in our control group. High performance liquid chromatography (HPLC) was used to determine concentrations of HP and LP (nmol/mmol creatinine). The average urinary HP concentrations were significantly increased in patients with osteosarcoma ( p=0.001) and chondrosarcoma ( p<0.001), whereas HP remained within the normal range in approximately half of the patients. The average urinary LP concentrations were not increased in osteosarcoma and chondrosarcoma patients as compared with the control group. Further studies in a large group of patients are necessary to evaluate whether HP might be a valuable marker of prognosis, and if its urinary concentration can be correlated to tumour burden.

Collagen crosslink excretion and staging of oral cancer

Lysylpyridinoline (LP) and hydroxylysylpyridinoline (HP) are collagen crosslink residues of which the urinary concentration reflects the level of connective-tissue turnover. HP is ubiquitous in tissue, whereas LP is specific for bone. The purpose of this investigation was to assess the sensitivity and specificity of an increased urinary concentration of both HP and LP in indicating infiltration of mandibular bone by an oral squamous cell carcinoma (OSCC) or recurrence of the disease after successful therapy. We investigated the history and urine levels in 116 adult patients, who were divided into the following groups. Group 1: patients with OSCC with bone infiltration (n=17); group 2: patients with confirmed OSCC (n=12) without evidence of bone infiltration; group 3: patients with recurrence of an OSCC (n=13); group 4: patients without clinical evidence of disease (n=74). The range and upper limit of normal values (HP(max) and LP(max)) were measured from the normal controls in group 4. Levels of LP and HP were measured by HPLC and fluorescence detection. There was a significant difference in the average urinary levels of LP and HP between groups 1-4 (P<0.001). The presence of mandibular bone infiltration could be detected with a sensitivity and specificity of 100% when comparing groups 1 and 2. Presence of tumour tissue could be detected with a sensitivity of 90%. In conclusion, a normal LP concentration in patients with an OSCC strongly suggests that bone invasion by the disease has not taken place. If both urinary HP and LP are elevated, disease recurrence is highly likely.