Xenografts processing

One of the obvious advantages of orthotopic models is that targeting processes involved in local invasion (e.g., angiogenesis) can be undertaken at a clinically relevant site (36). Since the early studies showing orthotopic transplantation of colon tumors and metastasis to the liver (39), tumor xenografts have been grown orthotopically in mice. However, despite the clinical relevance of orthotopic models, their utilization is hindered by a need for a high level of technical skill, time and cost. Therapeutic efficacy is also more difficult to assess with orthotopic models in contrast to the relative ease of subcutis tumor measurements (36). 

In summary, for monitoring the phosphorylation state of a tissue, highly sensitive detection provides an effective alternative to conventional detection, especially for archival material in which the fixation process is not controlled sufficiently compared with experimental material such as xenografts. The selection and validation of the phosphorylation-specific antibody used are also key processes for obtaining reliable histological information. 

In one study, PLG microspheres bound to DNA using a cryogenic double emulsion process and injected intramuscularly into mice were found to promote transgene expression for up to 174 days after injection, dependent upon microsphere mass. More recently nanoparticles were constructed from carboxy terminated, PEG modified PGL polymers. These particles were conjugated with an aptamer to the prostate specific membrane antigen and evaluated for in vivo biodistribution in an LNCaP (PSMA+) xenograft mouse model of prostate cancer. In this study, the aptamer caused a 3.77-fold increase in polymer concentration in the tumor tissue after retro-orbital injection (79). 

Animal models of disease play a critical role in the drug discovery process and are important in the lead candidate selection process as well. Categories of animal disease models include spontaneous disease, induced models (e.g., chemically, immunologically), xenograft models, infection models, and genetically modified models (e.g., transgenic knockouts (KOs) or knock-ins (KIs), humanized animals (e.g., expressing the human protein or receptor). The sub-... 

Products that may have the potential to stimulate growth or induce proliferation or clonal expansion of cell types, in particular, transformed cells, all processes that may eventually lead to neoplasia should be evaluated with respect to receptor expression in various malignant and normal human cells that are relevant to the patient population under study [27], In such cases normal human cell lines and multiple human cancer cell lines expressing the relevant receptor, as well as primary cells derived from human tumor explants, should be used for in vitro assessment. When in vitro data demonstrate enhanced growth, further studies in relevant in vivo xenograft animal models with receptor expressing tumor cell lines may be needed. In addition incorporation of sensitive indexes of cellular proliferation in long-term repeat-dose toxicity studies may provide useful information. 

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