Bruce E. LeRoy

Animal models of bone metastasis

Animal models are important tools to investigate the pathogenesis and develop treatment strategies for bone metastases in humans. However, there are few spontaneous models of bone metastasis despite the fact that rodents (rats and mice) and other animals (dogs and cats) often spontaneously develop cancer. Therefore, most experimental models of bone metastasis in rodents require injection or implantation of neoplastic cells into orthotopic locations, bones, or the left ventricle of the heart.

Computer-assisted imaging algorithms facilitate histomorphometric quantification of kidney damage in rodent renal failure models

Introduction: Surgical 5/6 nephrectomy and adenine-induced kidney failure in rats are frequently used models of progressive renal failure. In both models, rats develop significant morphological changes in the kidneys and quantification of these changes can be used to measure the efficacy of prophylactic or therapeutic approaches. In this study, the Aperio Genie Pattern Recognition technology, along with the Positive Pixel Count, Nuclear and Rare Event algorithms were used to quantify histological changes in both rat renal failure models. Methods: Analysis was performed on digitized slides of whole kidney sagittal sections stained with either hematoxylin and eosin or immunohistochemistry with an anti-nestin antibody to identify glomeruli, regenerating tubular epithelium, and tubulointerstitial myofibroblasts. An anti-polymorphonuclear neutrophil (PMN) antibody was also used to investigate neutrophil tissue infiltration. Results: Image analysis allowed for rapid and accurate quantification of relevant histopathologic changes such as increased cellularity and expansion of glomeruli, renal tubular dilatation, and degeneration, tissue inflammation, and mineral aggregation. The algorithms provided reliable and consistent results in both control and experimental groups and presented a quantifiable degree of damage associated with each model. Conclusion: These algorithms represent useful tools for the uniform and reproducible characterization of common histomorphologic features of renal injury in rats.

New bone formation in nude mouse calvaria induced by canine prostate tissue

Osteoblastic metastases are common in patients with advanced prostate cancer. The pathophysiology of the new bone formation at metastatic sites is not currently known, but it is hypothesized that growth factors secreted by the prostate may be involved. Unfortunately, most rodent models of prostate cancer with metastasis to bone are osteolytic and not osteoblastic. Significant osteolysis by tumor cells at metastatic sites also may lead to fractures or bone instability. Misinterpretation of new periosteal bone due to bone instability as tumor-cell osteo-induction is another disadvantage of the osteolytic models. To circumvent these problems, we have developed a model system of new bone formation in the calvaria of nude mice stimulated by normal canine prostate tissue. Collagenase-digested normal prostate tissue was implanted adjacent to the calvaria of nude mice. Calvaria were examined at 2 weeks post-implantation for changes in the bone microenvironment by histology, calcein uptake at sites of bone mineralization, and tartrate-resistant acid phosphatase staining for osteoclasts. The prostate tissue remained viable and induced abundant new woven bone formation on the adjacent periosteal surface. In some cases new bone formation also was induced on the distant or concave calvarial periosteum. The new bone stained intensely with calcein, which demonstrated mineralization of the bone matrix. The new bone formation on prostate-implanted calvaria significantly increased (1.7-fold) the thickness of the calvaria compared with control calvaria. New bone formation was not induced in calvaria of mice implanted with normal canine kidney, urinary bladder, spleen, or skeletal muscle tissue, or mice with surgically-induced disruption of the periosteum. Osteoclast numbers in the medullary spaces and periosteum of calvaria were mildly increased (61%) in mice with implanted prostate tissue. In conclusion, this animal model will be useful for investigating the roles of prostate-derived growth factors on new bone formation in vivo.

From the Cover: Inhibitors of Nicotinamide Phosphoribosyltransferase Cause Retinal Damage in Larval Zebrafish

Nicotinamide phosphoribosyltransferase (NAMPT) has been investigated as a target for oncology because it catalyzes a rate-limiting step in cellular energy metabolism to produce nicotinamide adenine dinucleotide. Small molecule inhibitors of NAMPT have been promising drug candidates but preclinical development has been hindered due to associated retinal toxicity. Here we demonstrate that larval zebrafish can predict retinal toxicity associated with this mechanism revealing an attractive alternative method for identifying such toxicities. Zebrafish permit higher throughput testing while using far lower quantities of test article compared with mammalian systems. NAMPT inhibitor-associated toxicity manifested in zebrafish as a loss of response to visual cues compared with auditory cues. Zebrafish retinal damage associated with NAMPT inhibitor treatment was confirmed through histopathology. Ranking 6 NAMPT inhibitors according to their impact on zebrafish vision revealed a positive correlation with their in vitro potencies on human tumor cells. This correlation indicates translatable pharmacodynamics between zebrafish and human NAMPT and is consistent with on-target activity as the cause of retinal toxicity associated with NAMPT inhibition. Together, these data illustrate the utility of zebrafish for identifying compounds that may cause ocular toxicity in mammals, and, likewise, for accelerating development of compounds with improved safety margins.