If one wants to know whether a patient's tumor will respond to a specific therapeutic regime, one must examine the response of that human tumor, not a mouse tumor, to the therapy Numerous murine models have been developed to study human cancer. These models are used to investigate the factors involved in malignant transformation, invasion and metastasis, as well as to examine response to therapy. One of the most widely used models is the human tumor xenograft. In this model, human tumor cells are transplanted, either under the skin or into the organ type in which the tumor originated, into immunocompromised mice that do not reject human cells. For example, the xenograft will be readily accepted by athymic nude mice, severely compromised immunodeficient (SCID) mice, or other immunocompromised mice (Morton and Houghton, 2007). Depending upon the number of cells injected, or the size of the tumor transplanted, the tumor will develop over 1-8 weeks (or in some instances 1-4 months, or longer), and the response to appropriate therapeutic regimes can be studied in vivo. Another type of animal model for studying human cancer is the genetically engineered mouse (GEM) model. The genetic profile of these mice is altered such that one or several genes thought to be involved in transformation or malignancy are mutated, deleted or overexpressed; subsequently, the effect of altering these genes is studied over time and therapeutic responses to these tumors may be followed in vivo. Both athymic nude mice and mouse xenograft models that use human tumor cell lines have been used for decades to increase our understanding of factors affecting tumor growth; however, recent information regarding the key influence of the tumor microenvironment on tumor progression and growth has led to greater reliance on GEM tumor models using immunocompetent mice, as well as use of primary human tumor xenografts in humanized mouse models. In fact, the xenograft models are often regarded as inferior to the GEM models. In this article, I hope to show that each model has its use in cancer diagnostics and in preclinical therapeutic modalities.Several criteria have recently been suggested for GEM models of human cancers: (1) mice must carry the same mutation that occurs in human tumors; (2) mutations should be engineered within the endogenous locus, and not expressed as a transgene; (3) mutated genes should be silent during embryogenesis and early postnatal development, except for in models of inherited pediatric tumors; (4) mutations should be within the specific target tissues in selected cell types; and (5) mutations must occur in a limited number of cells. Additional 'desired features' are that the tumor type and anatomopathology should be as similar as possible to that observed in human tumors, and that tumor development should proceed through the same, or similar, 'preneoplastic' stages (M. Barbacid, Keystone Symposium on Inflamation, Microenvironment and Cancer, 2008, and personal communication). Another important criterion, which is difficult t...

PurposeKnowledge of tumor mutation status is becoming increasingly important for the treatment of cancer, as mutation-specific inhibitors are being developed for clinical use that target only sub-populations of patients with particular tumor genotypes. Melanoma provides a recent example of this paradigm. We report here development, validation, and implementation of an assay designed to simultaneously detect 43 common somatic point mutations in 6 genes (BRAF, NRAS, KIT, GNAQ, GNA11, and CTNNB1) potentially relevant to existing and emerging targeted therapies specifically in melanoma.MethodsThe test utilizes the SNaPshot method (multiplex PCR, multiplex primer extension, and capillary electrophoresis) and can be performed rapidly with high sensitivity (requiring 5–10% mutant allele frequency) and minimal amounts of DNA (10–20 nanograms). The assay was validated using cell lines, fresh-frozen tissue, and formalin-fixed paraffin embedded tissue. Clinical characteristics and the impact on clinical trial enrollment were then assessed for the first 150 melanoma patients whose tumors were genotyped in the Vanderbilt molecular diagnostics lab.ResultsDirecting this test to a single disease, 90 of 150 (60%) melanomas from sites throughout the body harbored a mutation tested, including 57, 23, 6, 3, and 2 mutations in BRAF, NRAS, GNAQ, KIT, and CTNNB1, respectively. Among BRAF V600 mutations, 79%, 12%, 5%, and 4% were V600E, V600K, V600R, and V600M, respectively. 23 of 54 (43%) patients with mutation harboring metastatic disease were subsequently enrolled in genotype-driven trials.ConclusionWe present development of a simple mutational profiling screen for clinically relevant mutations in melanoma. Adoption of this genetically-informed approach to the treatment of melanoma has already had an impact on clinical trial enrollment and prioritization of therapy for patients with the disease.

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The chemokine receptors, CXCR1 and CXCR2, couple to Gαi to induce leukocyte recruitment and activation at sites of inflammation. Upon activation by CXCL8, these receptors become phosphorylated, desensitized and internalized. In this study we investigated the role of different G protein-coupled receptor kinases (GRKs) in CXCR1- and CXCR2-mediated cellular functions. To that end, shRNA was used to inhibit GRK 2, 3, 5 and 6 in RBL-2H3 cells stably expressing CXCR1 or CXCR2, and CXCL8-mediated receptor activation and regulation were assessed. Inhibition of GRK2 and GRK6, respectively, increased CXCR1 and CXCR2 resistance to phosphorylation, desensitization and internalization, and enhanced CXCL8-induced phosphoinositide hydrolysis and exocytosis in vitro. GRK2 depletion diminished CXCR1-induced ERK1/2 phosphorylation but had no effect in CXCR2-induced ERK1/2 phosphorylation. GRK6 depletion had no significant effect on CXCR1 function. However, peritoneal neutrophils from mice deficient in GRK6 (GRK6−/−) displayed an increase in CXCR2-mediated G-protein activation, but in vitro exhibited a decrease in chemotaxis, receptor desensitization and internalization relative to wild type (GRK6+/+) cells. In contrast, neutrophil recruitment in vivo in GRK6−/− mice was increased in response to delivery of CXCL1 through the air-pouch model. In a wound closure assay, GRK6−/− mice showed enhanced myeloperoxidase activity, suggesting enhanced neutrophil recruitment, and faster wound closure as compared to GRK6+/+ animals. Taken together, the results indicate that CXCR1 and CXCR2 couple to distinct GRK isoforms to mediate and regulate inflammatory responses. CXCR1 predominantly couples to GRK2, whereas CXCR2 interacts with GRK6 to negatively regulate receptor sensitization and trafficking, thus affecting cell signaling and angiogenesis.