Citations

Abstract Purpose: Gliomas with isocitrate dehydrogenase 1 mutations (IDH1mut) are less aggressive than IDH1 wild-type (IDH1wt) gliomas and have global genomic hypermethylation. Yet it is unclear how specific hypermethylation events contribute to the IDH1mut phenotype. Previously, we showed that the gene encoding the procoagulant tissue factor (TF), F3, is among the most hypermethylated and downregulated genes in IDH1mut gliomas, correlating with greatly reduced thrombosis in patients with IDH1mut glioma. Because TF also increases the aggressiveness of many cancers, the current study explored the contribution of TF suppression to the reduced malignancy of IDH1mut gliomas. Experimental Design: TF expression was manipulated in patient-derived IDH1mut and IDH1wt glioma cells, followed by evaluation of in vitro and in vivo behavior and analyses of cell signaling pathways. Results: A demethylating agent, decitabine, increased F3 transcription and TF-dependent coagulative activity in IDH1mut cells, but not in IDH1wt cells. TF induction enhanced the proliferation, invasion, and colony formation of IDH1mut cells, and increased the intracranial engraftment of IDH1mut GBM164 from 0% to 100% (P = 0.0001). Conversely, TF knockdown doubled the median survival of mice engrafted with IDH1wt/EGFRvIIIamp GBM6, and caused complete regression of IDH1wt/EGFRamp GBM12 (P = 0.001). In vitro and in vivo effects were linked to activation of receptor tyrosine kinases (RTK) by TF through a Src-dependent intracellular pathway, even when extracellular RTK stimulation was blocked. TF stimulated invasion predominately through upregulation of β-catenin. Conclusions: These data show that TF suppression is a component of IDH1mut glioma behavior, and that it may therefore be an attractive target against IDH1wt gliomas.

Abstract Triple-negative breast cancer (TNBC) is characterized by elevated locoregional recurrence risk despite aggressive local therapies. New tumor-specific radiosensitizers are needed. We hypothesized that the ATR inhibitor, VX-970 (now known as M6620), would preferentially radiosensitize TNBC. Noncancerous breast epithelial and TNBC cell lines were investigated in clonogenic survival, cell cycle, and DNA damage signaling and repair assays. In addition, patient-derived xenograft (PDX) models generated prospectively as part of a neoadjuvant chemotherapy study from either baseline tumor biopsies or surgical specimens with chemoresistant residual disease were assessed for sensitivity to fractionated radiotherapy, VX-970, or the combination. To explore potential response biomarkers, exome sequencing was assessed for germline and/or somatic alterations in homologous recombination (HR) genes and other alterations associated with ATR inhibitor sensitivity. VX-970 preferentially inhibited ATR-Chk1-CDC25a signaling, abrogated the radiotherapy-induced G2–M checkpoint, delayed resolution of DNA double-strand breaks, and reduced colony formation after radiotherapy in TNBC cells relative to normal-like breast epithelial cells. In vivo, VX-970 did not exhibit significant single-agent activity at the dose administered even in the context of genomic alterations predictive of ATR inhibitor responsiveness, but significantly sensitized TNBC PDXs to radiotherapy. Exome sequencing and functional testing demonstrated that combination therapy was effective in both HR-proficient and -deficient models. PDXs established from patients with chemoresistant TNBC were also highly radiosensitized. In conclusion, VX-970 is a tumor-specific radiosensitizer for TNBC. Patients with residual TNBC after neoadjuvant chemotherapy, a subset at particularly high risk of relapse, may be ideally suited for this treatment intensification strategy. Mol Cancer Ther; 17(11); 2462–72. ©2018 AACR.

Abstract Despite recent advances in cancer therapy, options for central nervous system metastasis (CM) remain limited and patient outcomes are dismal. The lack of tumor models that reflect the heterogeneity and complexity of human CM tumors is a barrier to understanding the underlying biology and to developing novel therapies. Here, we report the development and characterization of 39 patient derived xenograft (PDX) models of CM tumors with histological subtypes representing the disease spectrum. The PDX models successfully grew both in the flank and brains of mice, and retained their histology regardless of the site of implantation. Brain metastasis also formed in 5/12 models after intra-cardiac injection. Multi-omic analysis of the PDX tumor and the patient-matched CM tumor showed that PDXs largely retained the molecular profiles of the tumor from which they were derived, including the retention of aberrations in key driver genes and signaling pathways. PDXs differed primarily from the ungrafted patient tumors by a downregulation in immunity-related pathways, which was expected due to the use of an immuno-compromised host, arguing for the validity of using the flank as a site of implantation. Integrated analysis of mutations and gene expression changes in CM revealed an upregulation of neuronal signaling and DNA damage response, and downregulation of calcium signaling and inflammation. We also assessed the clonal evolution of the PDX from the original patient CM by tracing variant allele frequencies in copy number neutral regions. We found that the PDX tumors were heterogeneous and comprised of multiple tumor clones that were either unique or in common with the original tumor, and displayed evidence of clonal expansion. Two PDXs that underwent phylogeny assessment showed evidence of minor clone expansion. One such PDX was a tumor from a Her2+ breast cancer (CM13), which largely did not molecularly resemble its matched patient tumor but was confirmed to have some shared expressed variants. The PDX was nearly copy number neutral, which included loss of the Her2 amplicon, and had few mutations compared with its parent tumor. Most noteworthy, is that CM13 displayed unique molecular patterns, aggressive growth and was highly metastatic in vivo. From the flank, it led to multiple metastases, including micrometastasis in the brain. This suggests that minor clone takeover may confer tumor aggressiveness and potentiate brain metastasis. The large and diverse repertoire of PDXs developed and characterized in this study provides a new set of tools that will help deepen our understanding of CM and improve preclinical testing for CM therapies. Our data also show that expansion of minor clones could confer aggressive tumor behavior and may be important in tumor evolution in PDX models and human cancers. Citation Format: Ben Yi Tew, Christophe Legendre, Tim Triche, Gerald C. Gooden, Kyle N. Johnson, Rae Anne Martinez, Emanuel F. Petricoin, Mariaelena Pierobon, Joyce O'Shaughnessy, Cindy Osborne, Mark A. Schroeder, Daniel J. Ma, Mark Bernstein, Jann N. Sarkaria, Steven A. Toms, Bodour Salhia. Development and characterization of patient derived xenografts from central nervous system metastasis reveal minor clone expansion linked with aggressive tumor behavior [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 991.