A better understanding of tumor metastasis requires development of animal models that authentically reproduce the metastatic process. By modifying an existing mouse model of breast cancer, we discovered that macrophage-stimulating protein promoted breast tumor growth and metastasis to several organs. A special feature of our findings was the occurrence of osteolytic bone metastases, which are prominent in human breast cancer. To explore the clinical relevance of our model, we examined expression levels of three genes involved in activation of the MSP signaling pathway (MSP, MT-SP1, and MST1R) in human breast tumors. We found that overexpression of MSP, MT-SP1, and MST1R was a strong independent indicator of both metastasis and death in human breast cancer patients and significantly increased the accuracy of an existing gene expression signature for poor prognosis. These data suggest that signaling initiated by MSP is an important contributor to metastasis of breast cancer and introduce an independent biomarker for assessing the prognosis of humans with breast cancer.bone metastasis ͉ Ron ͉ tumor ͉ inflammation ͉ prognostic factor B reast cancer often results in metastasis to many organs, including lymph nodes, bone, lungs, brain, and liver. The most frequent site of breast cancer metastasis is the bone, which occurs in Ϸ80% of patients with advanced disease (1). To better understand metastasis of breast cancer, models are needed in which metastases spontaneously occur from tumors arising in the orthotopic site. Such models have been described, although they use immortalized cell lines and usually require immunodeficient hosts. We describe here the modification of a mouse model of breast cancer in which tumors originate from primary breast epithelial cells, and metastasis occurs from an orthotopic tumor in immunocompetent animals. This experimental system allows us to efficiently examine the effect of individual genes or combinations of genes on tumor behavior. In this study, we examined the role of macrophage-stimulating protein (MSP) in breast tumor growth and metastasis.MSP was originally identified as a serum protein that elicited macrophage chemotaxis and activation (2, 3). MSP is secreted as an inactive single-chain precursor (pro-MSP), which becomes active after proteolytic cleavage to yield a disufide-linked heterodimer. The protease that activates pro-MSP was isolated from the extracellular membranes of macrophages (4) and has recently been identified as membrane-type serine protease-1 (MT-SP1, also known as matripase), which is expressed on macrophages and several types of epithelial cells, including breast cells (5).The biological effects of MSP are not restricted to macrophages. In particular, MSP can promote migration of various epithelial cell lines (6, 7), and the receptor for MSP, macrophage-stimulating-1 receptor (MST1R, also known as Ron), can induce an epithelialto-mesenchymal transition in immortalized canine kidney cells in vitro (8). Evidence is accumulating that the MSP/MST1R pathway is inv...

Evaluation of glycosaminoglycan (GAG) concentration in articular cartilage is of particular interest to the study of degenerative joint diseases such as osteoarthritis (OA). Noninvasive imaging techniques such as magnetic resonance imaging (MRI) and computed tomography (CT) have demonstrated the potential to assess biochemical markers of cartilage integrity such as GAG content; however, many imaging techniques are available and the optimization of particular techniques in the diagnosis of joint disease remains an active area of research. In order to highlight the differences between these various approaches, this work compares MRI (T1, T2, and T1ρ) and contrast-enhanced CT in human articular cartilage, in both the presence and absence of gadolinium-based contrast agent. Pre-and postcontrast T2 values were found to be similar on a regional level and correlated with each other. As expected, T1 values were shortened significantly on both a global and a spatial basis in the presence of gadolinium (Gd); similar results were found for T1ρ. T2 values were found to correlate mildly with postcontrast T1, T1(Gd), and with precontrast T1ρ values. In addition, contrast-enhanced CT values correlated with both precontrast T1ρ and T1(Gd) more strongly than with precontrast T2. Finally, T1(Gd) and precontrast T1ρ were found to be moderately correlated with CT data. However, T1(Gd) and precontrast T1ρ were found to be almost completely uncorrelated. Together, these results indicate that T1ρ, T2, and contrast-enhanced techniques may provide complementary information about the molecular environment in cartilage during the evolution of OA.

Objective The development of osteoarthritis following traumatic anterior cruciate ligament (ACL) injury is well established. However, few reliable indicators of early osteoarthritic changes have been established, which has limited the development of effective therapies. T1ρ and T2 mapping techniques have the ability to provide highly accurate and quantitative measurements of articular cartilage degeneration in vivo. Relating these cartilaginous changes to high-resolution bone-densitometric evaluations of the late-stage osteoarthritic bone is crucial in elucidating the mechanisms of development of traumatic osteoarthritis (OA) and potential therapies for early- or late-stage intervention. Methods Twelve rabbits were monitored with in vivo magnetic resonance imaging (MRI) scans following ACL transection surgery with a contralateral leg sham operation. Six of the rabbits were treated with oral doxycycline for the duration of the experiment. At 12 weeks, the excised knees from three animals from each group (n=6 overall) were subjected to micro-computed tomography (CT) analysis. Results Consistent with previous studies, initial elevations in T1ρ and T2 values in ACL-transected animals were observed with relative normalization towards values see in sham-operated legs over the 12-week study. This biphasic pattern could hold diagnostic potential to differentiate osteoarthritic cartilage by tracking the relative proportions of T1ρ and T2 values as they rise with inflammation then fall as collagen and proteoglycan loss leads to further dehydration. The addition of doxycycline resulted in inconclusive, yet potentially interesting, cartilaginous changes in several compartments of the rabbit legs. Micro-CT studies demonstrated decreased bone densitometrics in ACL-transected knees. Correlation studies suggest that the cartilaginous changes may be associated with some aspects of bony change and the development of OA. Conclusion We conclude that there are definite relationships between cartilaginous changes as seen on MRI and late-stage microstructural bony changes after traumatic ACL injury in rabbits. In addition, doxycycline may show promise in mitigating early-stage cartilage damage that may serve to lessen late-stage osteoarthritic changes. This study demonstrates the ability to track OA progression and therapeutic efficacy with imaging modalities in vivo.

Significant effort currently is being devoted to the development of noninvasive imaging systems that allow in vivo assessment of biological and biomolecular interactions in mice and other small animals. While physiological function in small animals can be localized and imaged using conventional radionuclide imaging techniques such as single-photon emission tomography (SPECT) and positron emission tomography (PET), these techniques inherently are limited to spatial resolutions of 1−2 mm. For this reason, we are developing a small animal radionuclide imaging system (SARIS) using grazing incidence optics to focus gamma-rays emitted by 125 I and other radiopharmaceuticals. We have developed a prototype optic with sufficient accuracy and precision to focus the 27.5 keV photons from 125 I onto a high-resolution imaging detector. Experimental measurements from the prototype have demonstrated that the optic can focus X-rays from a microfocus X-ray tube to a spot having physical dimensions (approximately 1500 microns half-power diameter) consistent with those predicted by theory. Our theoretical and numerical analysis also indicate that an optic can be designed and build that ultimately can achieve 100 µm spatial resolution with sufficient efficiency to perform in vivo single photon emission imaging studies in small animal.