Inhibition of tumor angiogenesis through blockade of the vascular endothelial growth factor (VEGF) signaling pathway is a novel treatment modality in oncology. Preclinical findings suggest that ...long-term clinical outcomes may improve with blockade of additional proangiogenic receptor tyrosine kinases: platelet-derived growth factor receptors (PDGFR) and fibroblast growth factor receptors (FGFR). BIBF 1120 is an indolinone derivative potently blocking VEGF receptor (VEGFR), PDGFR and FGFR kinase activity in enzymatic assays (IC(50), 20-100 nmol/L). BIBF 1120 inhibits mitogen-activated protein kinase and Akt signaling pathways in three cell types contributing to angiogenesis, endothelial cells, pericytes, and smooth muscle cells, resulting in inhibition of cell proliferation (EC(50), 10-80 nmol/L) and apoptosis. In all tumor models tested thus far, including human tumor xenografts growing in nude mice and a syngeneic rat tumor model, BIBF 1120 is highly active at well-tolerated doses (25-100 mg/kg daily p.o.), as measured by magnetic resonance imaging of tumor perfusion after 3 days, reducing vessel density and vessel integrity after 5 days, and inducing profound growth inhibition. A distinct pharmacodynamic feature of BIBF 1120 in cell culture is sustained pathway inhibition (up to 32 hours after 1-hour treatment), suggesting slow receptor off-kinetics. Although BIBF 1120 is rapidly metabolized in vivo by methylester cleavage, resulting in a short mean residence time, once daily oral dosing is fully efficacious in xenograft models. These distinctive pharmacokinetic and pharmacodynamic properties may help explain clinical observations with BIBF 1120, currently entering phase III clinical development.
Activated tumor stroma participates in tumor cell growth, invasion, and metastasis. Normal fibroblasts and cancer-associated fibroblasts (CAFs) have been shown to display distinct gene expression ...signatures. This molecular heterogeneity may influence the way tumor cells migrate, proliferate, and survive during tumor progression. To test this hypothesis and to better understand the molecular mechanisms that control these interactions, we established a three-dimensional (3D) human cell culture system that recapitulates the tumor heterogeneity observed in vivo. Human colon tumor cells were grown as multicellular spheroids and subsequently co-cultured with normal fibroblasts or CAFs in collagen I gels. This in vitro model system closely mirrors the architecture of human epithelial cancers and allows the characterization of the tumor cell-stroma interactions phenotypically and at the molecular level. Using GeneChip analysis, antibody arrays, and enzyme-linked immunosorbent assays, we demonstrate that the interaction of colon cancer cells with stromal fibroblasts induced different highly relevant cancer expression profiles. Genes involved in invasion, extracellular matrix remodeling, inflammation, and angiogenesis were differentially regulated in our 3D carcinoma model. The modular setup, reproducibility, and robustness of the model make it a powerful tool to identify target molecules involved in signaling pathways that mediate paracrine interactions in the tumor microenvironment and to validate the influence of these molecular targets during tumor growth and invasion in the supporting stroma.
In the period from 1923 to 1986 our pathologists examined pathologic material from 102 patients with alveolar soft‐part sarcoma (ASPS). Followup clinical data is available for 91. Median followup is ...7 years (range 1 month to 27 years). Local recurrence was only found if residual disease was left at the time of the original excision. Survival in those patients who presented without metastases was 77% at 2 years, 60% at 5 years, 38% at 10 years and 15% at 20 years (median 6 years). No survival advantage could be demonstrated for patients who received chemo and/or radiotherapy, although numbers are small and staging not uniform. An evaluation by electron microscopy and immunohistochemistry cannot confirm recent claims that ASPS is a muscle tumor. ASPS is an unusual neoplasm; the primary therapeutic option is aggressive surgical excision. Survival even with the development of metastases can be long.
Metastasis, which is linked to the invasive properties acquired by the primary tumor during cancer progression, is the major life-threatening event in cancer patients. There is increasing evidence ...that the tumor stroma is involved in the infiltrative growth of malignant cells. Many models have been developed to study tumor/stroma interaction and 3D model systems represent the most promising approaches, because they closely mimic the situation in vivo. The main goal of these models is to better understand tumorigenesis and to discover novel therapeutic avenues to treat cancer.
Mutations in the HER2 kinase domain have been identified in human clinical lung cancer specimens. Here we demonstrate that inducible expression of the most common HER2 mutant (HER2YVMA) in mouse lung ...epithelium causes invasive adenosquamous carcinomas restricted to proximal and distal bronchioles. Continuous expression of HER2YVMA is essential for tumor maintenance, suggesting a key role for HER2 in lung adenosquamous tumorigenesis. Preclinical studies assessing the in vivo effect of erlotinib, trastuzumab, BIBW2992, and/or rapamycin on HER2YVMA transgenic mice or H1781 xenografts with documented tumor burden revealed that the combination of BIBW2992 and rapamycin is the most effective treatment paradigm causing significant tumor shrinkage. Immunohistochemical analysis of lung tumors treated with BIBW2992 and rapamycin combination revealed decreased phosphorylation levels for proteins in both upstream and downstream arms of MAPK and Akt/mTOR signaling axes, indicating inhibition of these pathways. Based on these findings, clinical testing of the BIBW2992/rapamycin combination in non-small cell lung cancer patients with tumors expressing HER2 mutations is warranted.
EndoGlyx-1, the antigen identified with the monoclonal antibody H572, is a pan-endothelial human cell surface glycoprotein complex composed of four different disulfide-bonded protein species with an ...apparent molecular mass of approximately 500 kDa. Here, we report the purification and peptide analysis of two EndoGlyx-1 subunits, p125 and p140, and the identification of a common, full-length cDNA with an open reading frame of 2847 base pairs. The EndoGlyx-1 cDNA encodes a protein of 949 amino acids with a predicted molecular mass of 105 kDa, found as an entry for an unnamed protein with unknown function in public data bases. A short sequence tag matching the cDNA of this gene was independently discovered by serial analysis of gene expression profiling as a pan-endothelial marker, PEM87. Bioinformatic evaluation classifies EndoGlyx-1 as an EMILIN-like protein composed of a signal sequence, an N-terminal EMI domain, and a C-terminal C1q-like domain, separated from each other by a central coiled-coil-rich region. Biochemical and carbohydrate analysis revealed that p125, p140, and the two additional EndoGlyx-1 subunits, p110 and p200, are exposed on the cell surface. The three smaller subunits show a similar pattern of N-linked and O-linked carbohydrates, as shown by enzyme digestion. Because the two globular domains of EndoGlyx-1 p125/p140 show structural features shared by EMILIN-1 and Multimerin, two oligomerizing glycoproteins implicated in cell-matrix adhesion and hemostasis, it will be of interest to explore similar functions for EndoGlyx-1 in human vascular endothelium.
BI 882370 is a highly potent and selective RAF inhibitor that binds to the DFG-out (inactive) conformation of the BRAF kinase. The compound inhibited proliferation of human BRAF-mutant melanoma cells ...with 100× higher potency (1-10 nmol/L) than vemurafenib, whereas wild-type cells were not affected at 1,000 nmol/L. BI 882370 administered orally was efficacious in multiple mouse models of BRAF-mutant melanomas and colorectal carcinomas, and at 25 mg/kg twice daily showed superior efficacy compared with vemurafenib, dabrafenib, or trametinib (dosed to provide exposures reached in patients). To model drug resistance, A375 melanoma-bearing mice were initially treated with vemurafenib; all tumors responded with regression, but the majority subsequently resumed growth. Trametinib did not show any efficacy in this progressing population. BI 882370 induced tumor regression; however, resistance developed within 3 weeks. BI 882370 in combination with trametinib resulted in more pronounced regressions, and resistance was not observed during 5 weeks of second-line therapy. Importantly, mice treated with BI 882370 did not show any body weight loss or clinical signs of intolerability, and no pathologic changes were observed in several major organs investigated, including skin. Furthermore, a pilot study in rats (up to 60 mg/kg daily for 2 weeks) indicated lack of toxicity in terms of clinical chemistry, hematology, pathology, and toxicogenomics. Our results indicate the feasibility of developing novel compounds that provide an improved therapeutic window compared with first-generation BRAF inhibitors, resulting in more pronounced and long-lasting pathway suppression and thus improved efficacy.
Background. Bone morphogenetic proteins (BMPs) are potent inducers of bone formation. Functional and immunohistochemical studies have identified BMPs in a subset of osteosarcomas. In the present ...study, the authors extend the analysis of BMP expression to other bone and soft tissue sarcomas.
Methods. Monoclonal antibody AbH3b2/17 against human BMP‐2 and BMP‐4 was used in avidin‐biotin‐immunoperoxidase assays with frozen sections of bone tumors (71 specimens), soft tissue sarcomas (69 specimens), and normal tissues.
Results. Among bone tumors, BMP was detected in osteosarcomas (17 of 29 samples), malignant fibrous histiocytomas (MFHs) (6 of 6), and the spindle cell sarcomatous components of spindle cell (dedifferentiated) chondrosarcomas (4 of 4), but not in conventional chondrosarcomas (0 of 10) or Ewing's sarcomas (0 of 14). Histologic subtypes of osteosarcoma differed for BMP expression, with 8 of 9 fibrohistiocytic, 9 of 13 osteoblastic, and 0 of 5 chondroblastic lesions showing immunostaining. In all BMP‐positive bone tumors, immunostaining was localized in the cytoplasm of primitive mesenchymal cells, with little or no staining in tumor matrix and more mature osteoblastic/chondrocytic cells. Among soft tissue sarcomas, MFHs (11 of 12), liposarcomas (5 of 11), leiomyosarcomas (3 of 9), and malignant schwannomas (3 of 8) showed cytoplasmic BMP immunostaining. Synovial sarcomas (0 of 9), rhabdomyosarcomas (0 of 8), and fibrosarcomas (0 of 7) were BMP‐negative. All normal humantissues tested, including the tissues of a 16‐week‐old fetus, lacked BMP immunoreactivity.
Conclusions. Bone morphogenetic protein is expressed in a subset of osteosarcomas, a high proportion of MFHs of bone and soft tissue, and in spindle cell chondrosarcomas. In these tumors, BMP is localized predominantly to the cytoplasm of malignant cells with primitive mesenchymal features; no or little BMP is detected in the more differentiated elements of bone and soft tissue sarcomas, Different histologic types of bone and soft tissue sarcomas may mimic discrete stages of mesenchymal differentiation as defined by BMP expression and histologic criteria.
Antigens and receptors that are highly expressed on tumor stromal cells, such as fibroblast activation protein (FAP), are attractive targets for antibody-based therapies because the supporting stroma ...and vessel network is essential for a solid neoplasm to grow beyond a size of 1-2 mm. The in vivo characterization of antibodies targeting human stromal or vessel antigens is hindered by the lack of an appropriate mouse model system because xenografts in standard mouse models express stromal and vessels elements of murine origin. This limitation may be overcome by the development of a human skin/mouse chimeric model, which is established by transplanting human foreskin on to the lateral flank of severe combined immunodeficient mice. The subsequent inoculation of breast carcinoma MCF-7 cells within the dermis of the transplanted human skin resulted in the production of xenografts expressing stromal and vessel elements of human origin. Widespread expression of human FAP-positive reactive stromal fibroblasts within xenografts was seen up to 2 months posttransplantation and postinjection of cells. Human blood vessel antigen expression also persisted at 2 months posttransplantation and postinjection of cells with murine vessels coexisting with the human vascular supply. The model was subsequently used to evaluate the biodistribution properties of an iodine-131-labeled humanized anti-FAP monoclonal antibody (BIBH-7). The results showed high specific targeting of the stromal compartment of the xenograft, indicating that the model provides a useful and novel approach for the in vivo assessment of the immunotherapeutic potential of molecules targeting human stroma and angiogenic systems.
PDF
