Panel Of Breast Cancer Xenografts Research Articles

Coordinate hyperactivation of Notch1 and Ras/MAPK pathways correlates with poor patient survival: novel therapeutic strategy for aggressive breast cancers.

Aberrant activation of Notch and Ras pathways has been detected in breast cancers. A synergy between these two pathways has also been shown in breast cell transformation in culture. Yet, the clinical relevance of Notch-Ras cooperation in breast cancer progression remains unexplored. In this study, we show that coordinate hyperactivation of Notch1 and Ras/MAPK pathways in breast cancer patient specimens, as assessed by IHC for cleaved Notch1 and pErk1/2, respectively, correlated with early relapse to vital organs and poor overall survival. Interestingly, majority of such Notch1(high)Erk(high) cases encompassed the highly aggressive triple-negative breast cancers (TNBC), and were enriched in stem cell markers. We further show that combinatorial inhibition of Notch1 and Ras/MAPK pathways, using a novel mAb against Notch1 and a MEK inhibitor, respectively, led to a significant reduction in proliferation and survival of breast cancer cells compared with individual inhibition. Combined inhibition also abrogated sphere-forming potential, and depleted the putative cancer stem-like cell subpopulation. Most importantly, combinatorial inhibition of Notch1 and Ras/MAPK pathways completely blocked tumor growth in a panel of breast cancer xenografts, including the TNBCs. Thus, our study identifies coordinate hyperactivation of Notch1 and Ras/MAPK pathways as novel biomarkers for poor breast cancer outcome. Furthermore, based on our preclinical data, we propose combinatorial targeting of these two pathways as a treatment strategy for highly aggressive breast cancers, particularly the TNBCs that currently lack any targeted therapeutic module.

68Ga-DOTA-affibody molecule for in vivo assessment of HER2/neu expression with PET.

Overexpression of HER2/neu in breast cancer is correlated with a poor prognosis. It may vary between primary tumors and metastatic lesions and change during the treatment. Therefore, there is a need for a new means to assess HER2/neu expression in vivo. In this work, we used (68)Ga-labeled DOTA-Z(HER2:2891)-Affibody to monitor HER2/neu expression in a panel of breast cancer xenografts. DOTA-Z(HER2:2891)-Affibody molecules were labeled with (68)Ga. In vitro binding was characterized by a receptor saturation assay. Biodistribution and PET imaging studies were conducted in athymic nude mice bearing subcutaneous human breast cancer tumors with three different levels of HER2/neu expression. Nonspecific uptake was analyzed using non-HER2-specific Affibody molecules. Signal detected by PET was compared with ex vivo assessment of the tracer uptake and HER2/neu expression. The (68)Ga-DOTA-Z(HER2:2891)-Affibody probe showed high binding affinity to MDA-MB-361 cells (K (D) = 1.4 ± 0.19 nM). In vivo biodistribution and PET imaging studies demonstrated high radioactivity uptake in HER2/neu-positive tumors. Tracer was eliminated quickly from the blood and normal tissues, resulting in high tumor-to-blood ratios. The highest concentration of radioactivity in normal tissue was seen in the kidneys (227 ± 14%ID/g). High-contrast PET images of HER2/neu-overexpressing tumors were recorded as soon as 1 h after tracer injection. A good correlation was observed between PET imaging, biodistribution estimates of tumor tracer concentration, and the receptor expression. These results suggest that PET imaging using (68)Ga-DOTA-Z(HER2:2891)-Affibody is sensitive enough to detect different levels of HER2/neu expression in vivo.

Abstract 5284: 68Ga-radiolabeled DOTA-affibody molecule for in vivo assessment of HER2 expression with PET

Abstract Overexpression of HER2, a transmembrane tyrosine kinase receptor, is correlated with poor prognosis in patients with breast cancer. HER2 expression may vary between primary tumors and metastatic lesions and also change during the treatment. Therefore, there is a need for methods that can assess global HER2 expression non-invasively and reproducibly. PET imaging is well suited to this task based on its high sensitivity. Fluorine-18 (18F) is the most commonly used PET emitter for in vivo imaging since it is relatively short lived radionuclide (109 min). However, its production requires a cyclotron. Gallium-68 (68Ga) is an attractive alternative to 18F. It has a similarly short half-life (68 min) but can be obtained from a generator. In this work, we sought to monitor HER2 expression in vivo with 68Ga-labeled DOTA-ZHER2:2891 Affibody in a panel of breast cancer xenografts with different levels of HER2 expression. ZHER2:2891 Affibody molecules were conjugated with the chelator, DOTA (1,4,7,10-tetraazacyclododecane-N,N′,N′′,N′′′-tetraacetic acid), and labeled with 68Ga. The in vitro binding characteristic of the tracer was evaluated using saturation cell-binding assay. In vivo studies were conducted in athymic nude mice bearing subcutaneous human breast cancer tumors with four different levels of HER2 expression. PET/CT scans were performed 1, 2, 3 hour post tracer injection. After imaging, the animals were sacrificed and selected organs were dissected to characterize the relationship between the signal detected by PET, ex vivo assessment of the tracer uptake, and the HER2 expression (in tumors). Nonspecific uptake was analyzed 1 hour post His6-ZTaq-GS-Cys-DOTA-68Ga (non-HER2-specific Affibody molecules) injection. In vitro assays showed high binding affinity of 68Ga-DOTA-ZHER2:2891 Affibody probe to MDA-MB-361 cells (Kd = 1.4±0.19 nM). In vivo biodistribution and PET imaging studies demonstrated high radioactivity uptake in the HER2 overexpressing tumors. Tracer was eliminated quickly from the blood and normal tissues, providing high tumor-to-blood ratios. The highest normal tissue concentration of radioactivity was seen in the kidneys. High-contrast PET images were recorded in BT474 and MDA-MB361 tumors 1 h post tracer injection. Low, but still detectable, uptake was observed for MCF7 tumors. Very good correlation was observed between PET and ex vivo estimates of tracer concentration and the receptor expression in the tumor tissue, as assessed by, respectively, radioactivity accumulation and enzyme-linked immunosorbent assay (ELISA). Stability tests of 68Ga-DOTA- ZHER2:2891 Affibody in vivo revealed that the tracer is stable in blood. These results suggest that PET imaging using 68Ga-DOTA-ZHER2:2891 Affibody is sensitive enough to detect different levels of HER2 expression in vivo. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 5284. doi:10.1158/1538-7445.AM2011-5284

A New Model of Patient Tumor-Derived Breast Cancer Xenografts for Preclinical Assays

To establish a panel of human breast cancer (HBC) xenografts in immunodeficient mice suitable for pharmacologic preclinical assays. 200 samples of HBCs were grafted into Swiss nude mice. Twenty-five transplantable xenografts were established (12.5%). Their characterization included histology, p53 status, genetic analysis by array comparative genomic hybridization, gene expression by Western blotting, and quantitative reverse transcription-PCR. Biological profiles of nine xenografts were compared with those of the corresponding patient's tumor. Chemosensitivities of 17 xenografts to a combination of Adriamycin and cyclophosphamide (AC), docetaxel, trastuzumab, and Degarelix were evaluated. Almost all patient tumors established as xenografts displayed an aggressive phenotype, i.e., high-grade, triple-negative status. The histology of the xenografts recapitulated the features of the original tumors. Mutation of p53 and inactivation of Rb and PTEN proteins were found in 83%, 30%, and 42% of HBC xenografts, respectively. Two HBCx had an ERBB2 (HER2) amplification. Large variations were observed in the expression of HER family receptors and in genomic profiles. Genomic alterations were close to those of original samples in paired tumors. Three xenografts formed lung metastases. A total of 15 of the 17 HBCx (88%) responded to AC, and 8 (47%) responded to docetaxel. One ERBB2-amplified xenograft responded to trastuzumab, whereas the other did not. The drug response of HBC xenografts was concordant with that of the patient's tumor in five of seven analyzable cases. This panel of breast cancer xenografts includes 15 triple-negative, one ER positive and 2 ERBB2 positive. This panel represents a useful preclinical tool for testing new agents and protocols and for further exploration of the biological basis of drug responses.