Intratibial model of prostate to bone metastases
To study the impact of prostate cancer growth in the bone microenvironment.
Intratibial Inoculation, Lucifrase, fluorescence, CT
Bone metastasis is a common event in advanced prostate cancer (1). The metastatic lesions are hallmarked by areas of extensive bone destruction and formation (2). Currently, treatment options are limited and an understanding of the molecular mechanisms that drive osteotropism, establishment and growth of the lesions is required in order to generate new therapies to prevent or cure the disease. Therefore, appropriate animal models that recapitualte human clinical scenario are necessary.
Several spontaneous genetic models of primary prostate cancer exist and some develop bone metastases over time. For example, the transgenic adenocarcinoma of the mouse prostate (TRAMP) model has been shown to develop bone metastases but in addition to taking time to be detectable, bone metastases are rare in the model compared to periaortic lymph nodes and lung metastases (3). Crossing the transgenic pro-basin driven large-T antigen (LADY) model with a probasin driven hepsin transgenic results in faster progression of prostate cancer with increased metastasis to bone but the metastases are typically lytic and the cancer cells appear to be neuroendocrine rather than adenocarcinoma, the latter being the most common form of human prostate cancer (4). Alternatives to transgenic models mainly include the use of human and rodent cell lines and tissues. These include but by no means are limited to C4-2B (5)and LuCAP (6)both of which will mixed osteoblastic and osteolytic lesions and PC-3 (7)that typically induces lytic lesions.
While cell lines can metastasize to bone from sub-cutaneous or orthotopic sites, many researchers use intracardiac inoculation (8). In this method, injection of the cancer cells into the left ventricle allows for systemic dissemination of the cancer cells and preferential seeding of the skeleton. A major advantage is that the IC model mimics the route of hematogenous metastasis to bone but disadvantages lie in the technicality of the procedure and the consistency of the site of bone metastasis making direct comparisons between groups difficult.
Models of intraosseous cancer growth have also been developed. Implanting femoral human fetal bone sub-cutaneously and allowing for aborization by the host has been shown to preferentially recruit human prostate cancer cells when they are systemically delivered via tail vein (9). Calvarial implant of prostate cancer tissue is also a useful approach to examining tumor-bone interaction albeit examining cancer invasion into intramembranous rather than endochondral bone (10).
Arguably, one of the most common techniques used to study tumor interaction with the host bone microenvironment is the intratibial model. Typically, 1x106 cells in a volume of 10μl are injected through the tibial crest and into the medullary canal. The contralateral limb should receive an injection of saline to control for changes in bone remodeling as a consequence of the injection. The expression of luciferase or fluorescent proteins in the cancer cells can be utilized to monitor tumor growth over time. Use of μCT/SPECT/PET modalities can also be used to monitor tumor induced osteolysis (depending on resolution) and osteogenesis. Radioisotopes such as Methyldiphosphonate-Technitium99 (MDP-Tc99) and sodium fluoride (NaF18) can be used to label areas of rapid bone formation (11). Disadvantages to the intratibial model include that the injury induced during inoculation may contribute to tumor establishment but this can be somewhat controlled by the sham inoculation in the contralateral limb. Further the model does not mimic the process of metastasis but rather the metastatic tumor-bone microenvironment.
- Coleman RE, Guise TA, Lipton A, Roodman GD, Berenson JR, Body JJ, et al. Advancing treatment for metastatic bone cancer: consensus recommendations from the Second Cambridge Conference. Clin Cancer Res. 2008;14(20):6387-95.
- Keller ET, Brown J. Prostate cancer bone metastases promote both osteolytic and osteoblastic activity. J Cell Biochem. 2004;91(4):718-29.
- Gingrich JR, Barrios RJ, Morton RA, Boyce BF, DeMayo FJ, Finegold MJ, et al. Metastatic prostate cancer in a transgenic mouse. Cancer Research. 1996;56(18):4096-102.
- Klezovitch O, Chevillet J, Mirosevich J, Roberts RL, Matusik RJ, Vasioukhin V. Hepsin promotes prostate cancer progression and metastasis 1. Cancer Cell. 2004;6(2):185-95.
- Wu HC, Hsieh JT, Gleave ME, Brown NM, Pathak S, Chung LW. Derivation of androgen-independent human LNCaP prostatic cancer cell sublines: role of bone stromal cells. Int J Cancer. 1994;57(3):406-12.
- Corey E, Quinn JE, Bladou F, Brown LG, Roudier MP, Brown JM, et al. Establishment and characterization of osseous prostate cancer models: intra-tibial injection of human prostate cancer cells. Prostate. 2002;52(1):20-33.
- Bonfil RD, Dong Z, Trindade Filho JC, Sabbota A, Osenkowski P, Nabha S, et al. Prostate cancer-associated membrane type 1-matrix metalloproteinase: a pivotal role in bone response and intraosseous tumor growth. Am J Pathol. 2007;170(6):2100-11.
- Sterling JA, Oyajobi BO, Grubbs B, Padalecki SS, Munoz SA, Gupta A, et al. The hedgehog signaling molecule Gli2 induces parathyroid hormone-related peptide expression and osteolysis in metastatic human breast cancer cells. Cancer Research. 2006;66(15):7548-53.
- Nemeth JA, Yousif R, Herzog M, Che M, Upadhyay J, Shekarriz B, et al. Matrix metalloproteinase activity, bone matrix turnover, and tumor cell proliferation in prostate cancer bone metastasis. Journal National Cancer Institute. 2002;94(1):17-25.
- Lynch CC, Hikosaka A, Acuff HB, Martin MD, Kawai N, Singh RK, et al. MMP-7 promotes prostate cancer-induced osteolysis via the solubilization of RANKL. Cancer Cell. 2005;7(5):485-96.
- Bruni-Cardoso A, Johnson LC, Vessella RL, Peterson TE, Lynch CC. Osteoclast-Derived Matrix Metalloproteinase-9 Directly Affects Angiogenesis in the Prostate Tumor-Bone Microenvironment. Mol Cancer Res. 2010.