A technology that visualizes tumor stem cells with clinically relevant tracers could have a broad impact on cancer diagnosis and treatment. The AC133 epitope of CD133 currently is one of the best-characterized tumor stem cell markers for many intra-and extracranial tumor entities. Here we demonstrate the successful noninvasive detection of AC133 + tumor stem cells by PET and nearinfrared fluorescence molecular tomography in subcutaneous and orthotopic glioma xenografts using antibody-based tracers. Particularly, microPET with 64 Cu-NOTA-AC133 mAb yielded high-quality images with outstanding tumor-to-background contrast, clearly delineating subcutaneous tumor stem cell-derived xenografts from surrounding tissues. Intracerebral tumors as small as 2-3 mm also were clearly discernible, and the microPET images reflected the invasive growth pattern of orthotopic cancer stem cell-derived tumors with low density of AC133 + cells. These data provide a basis for further preclinical and clinical use of the developed tracers for high-sensitivity and high-resolution monitoring of AC133 + tumor stem cells.cancer stem cells | CSCs | glioblastoma

Cancer stem cells (CSC) drive tumorigenesis and contribute to genotoxic therapy resistance, diffuse infiltrative invasion, and immunosuppression, which are key factors for the incurability of glioblastoma multiforme (GBM). The AC133 epitope of CD133 is an important CSC marker for GBM and other tumor entities. Here, we report the development and preclinical evaluation of a recombinant AC133ÂCD3 bispecific antibody (bsAb) that redirects human polyclonal T cells to AC133þ GBM stem cells (GBM-SC),inducing their strong targeted lysis. This novel bsAb prevented the outgrowth of AC133-positive subcutaneous GBM xenografts.Moreover, upon intracerebral infusion along with the local application of human CD8 þ T cells, it exhibited potent activity in prophylactic and treatment models of orthotopic GBM-SC-derived invasive brain tumors. In contrast, normal hematopoietic stem cells, some of which are AC133-positive, were virtually unaffected at bsAb concentrations effective against GBM-SCs and retained their colony-forming abilities. In conclusion, our data demonstrate the high activity of this new bsAb against patient-derived AC133-positive GBM-SCs in models of local therapy of highly invasive GBM. Cancer Res; 75(11); 2166-76. Ó2015 AACR.

BackgroundWe systematically analyzed multiple myeloma (MM) cell lines and patient bone marrow cells for their engraftment capacity in immunodeficient mice and validated the response of the resulting xenografts to antimyeloma agents.Design and MethodsUsing flow cytometry and near infrared fluorescence in-vivo-imaging, growth kinetics of MM cell lines L363 and RPMI8226 and patient bone marrow cells were investigated with use of a murine subcutaneous bone implant, intratibial and intravenous approach in NOD/SCID, NOD/SCID treated with CD122 antibody and NOD/SCID IL-2Rγ(null) mice (NSG).ResultsMyeloma growth was significantly increased in the absence of natural killer cell activity (NSG or αCD122-treated NOD/SCID). Comparison of NSG and αCD122-treated NOD/SCID revealed enhanced growth kinetics in the former, especially with respect to metastatic tumor sites which were exclusively observed therein. In NSG, MM cells were more tumorigenic when injected intratibially than intravenously. In NOD/SCID in contrast, the use of juvenile long bone implants was superior to intratibial or intravenous cancer cell injection. Using the intratibial NSG model, mice developed typical disease symptoms exclusively when implanted with human MM cell lines or patient-derived bone marrow cells, but not with healthy bone marrow cells nor in mock-injected animals. Bortezomib and dexamethasone delayed myeloma progression in L363- as well as patient-derived MM cell bearing NSG. Antitumor activity could be quantified via flow cytometry and in vivo imaging analyses.ConclusionsOur results suggest that the intratibial NSG MM model mimics the clinical situation of the disseminated disease and serves as a valuable tool in the development of novel anticancer strategies.

Patient-derived xenografts (PDX) have emerged as an important translational research tool for understanding tumor biology and enabling drug efficacy testing. They are established by transfer of patient tumor into immune compromised mice with the intent of using them as Avatars; operating under the assumption that they closely resemble patient tumors. In this study, we established 27 PDX from 100 resected gastric cancers and studied their fidelity in histological and molecular subtypes. We show that the established PDX preserved histology and molecular subtypes of parental tumors. However, in depth investigation of the entire cohort revealed that not all histological and molecular subtypes are established. Also, for the established PDX models, genetic changes are selected at early passages and rare subclones can emerge in PDX. This study highlights the importance of considering the molecular and evolutionary characteristics of PDX for a proper use of such models, particularly for Avatar trials.

In up to 30% of non-small cell lung cancer (NSCLC) patients, the oncogenic driver of tumor growth is a constitutively activated epidermal growth factor receptor (EGFR). Although these patients gain great benefit from treatment with EGFR tyrosine kinase inhibitors, the development of resistance is inevitable. To model the emergence of drug resistance, an EGFR-driven, patient-derived xenograft (PDX) NSCLC model was treated continuously with Gefitinib in vivo. Over a period of more than three months, three separate clones developed and were subsequently analyzed: Whole exome sequencing and reverse phase protein arrays (RPPAs) were performed to identify the mechanism of resistance. In total, 13 genes were identified, which were mutated in all three resistant lines. Amongst them the mutations in NOMO2, ARHGEF5 and SMTNL2 were predicted as deleterious. The 53 mutated genes specific for at least two of the resistant lines were mainly involved in cell cycle activities or the Fanconi anemia pathway. On a protein level, total EGFR, total Axl, phospho-NFκB, and phospho-Stat1 were upregulated. Stat1, Stat3, MEK1/2, and NFκB displayed enhanced activation in the resistant clones determined by the phosphorylated vs. total protein ratio. In summary, we developed an NSCLC PDX line modelling possible escape mechanism under EGFR treatment. We identified three genes that have not been described before to be involved in an acquired EGFR resistance. Further functional studies are needed to decipher the underlying pathway regulation.