The Public Repository of Xenografts enables discovery and randomized phase II-like trials in mice

More than 90% of drugs with preclinical activity fail in human trials, largely due to insufficient efficacy. We hypothesized that adequately powered trials of patient-derived xenografts (PDX) in mice could efficiently define therapeutic activity across heterogeneous tumors. To address this hypothesis, we established a large, publicly available repository of well-characterized leukemia and lymphoma PDXs that undergo orthotopic engraftment, called the Public Repository of Xenografts (PRoXe). PRoXe includes all de-identified information relevant to the primary specimens and the PDXs derived from them. Using this repository, we demonstrate that large studies of acute leukemia PDXs that mimic human randomized clinical trials can characterize drug efficacy and generate transcriptional, functional, and proteomic biomarkers in both treatment-naive and relapsed/refractory disease

Targeting Vascular Pericytes in Hypoxic Tumors Increases Lung Metastasis via Angiopoietin-2

Strategies to target angiogenesis include inhibition of the vessel-stabilizing properties of vascular pericytes. Pericyte depletion in early-stage non-hypoxic tumors suppressed nascent angiogenesis, tumor growth, and lung metastasis. In contrast, pericyte depletion in advanced-stage hypoxic tumors with pre-established vasculature resulted in enhanced intra-tumoral hypoxia, decreased tumor growth, and increased lung metastasis. Furthermore, depletion of pericytes in post-natal retinal blood vessels resulted in abnormal and leaky vasculature. Tumor transcriptome profiling and biological validation revealed that angiopoietin signaling is a key regulatory pathway associated with pericyte targeting. Indeed, pericyte targeting in established mouse tumors increased angiopoietin-2 (ANG2/Angpt2) expression. Depletion of pericytes, coupled with targeting of ANG2 signaling, restored vascular stability in multiple model systems and decreased tumor growth and metastasis. Importantly, ANGPT2 expression correlated with poor outcome in patients with breast cancer. These results emphasize the potential utility of therapeutic regimens that target pericytes and ANG2 signaling in metastatic breast cancer

VEGF-A and Tenascin-C produced by S100A4+ stromal cells are important for metastatic colonization

Increased numbers of S100A4+ cells are associated with poor prognosis in patients who have cancer. Although the metastatic capabilities of S100A4+ cancer cells have been examined, the functional role of S100A4+ stromal cells in metastasis is largely unknown. To study the contribution of S100A4+ stromal cells in metastasis, we used transgenic mice that express viral thymidine kinase under control of the S100A4 promoter to specifically ablate S100A4+ stromal cells. Depletion of S100A4+ stromal cells significantly reduced metastatic colonization without affecting primary tumor growth. Multiple bone marrow transplantation studies demonstrated that these effects of S100A4+ stromal cells are attributable to local non–bone marrow-derived S100A4+ cells, which are likely fibroblasts in this setting. Reduction in metastasis due to the loss of S100A4+ fibroblasts correlated with a concomitant decrease in the expression of several ECM molecules and growth factors, particularly Tenascin-C and VEGF-A. The functional importance of stromal Tenascin-C and S100A4+ fibroblast-derived VEGF-A in metastasis was established by examining Tenascin-C null mice and transgenic mice expressing Cre recombinase under control of the S100A4 promoter crossed with mice carrying VEGF-A alleles flanked by loxP sites, which exhibited a significant decrease in metastatic colonization without effects on primary tumor growth. In particular, S100A4+ fibroblast-derived VEGF-A plays an important role in the establishment of an angiogenic microenvironment at the metastatic site to facilitate colonization, whereas stromal Tenascin-C may provide protection from apoptosis. Our study demonstrates a crucial role for local S100A4+ fibroblasts in providing the permissive “soil” for metastatic colonization, a challenging step in the metastatic cascade

Pericyte Depletion Results in Hypoxia-Associated Epithelial-to-Mesenchymal Transition and Metastasis Mediated by Met Signaling Pathway

The functional role of pericytes in cancer progression remains unknown. Clinical studies suggest that low numbers of vessel-associated pericytes correlated with a drop in overall survival of patients with invasive breast cancer. Using genetic mouse models or pharmacological inhibitors, pericyte depletion suppressed tumor growth but enhanced metastasis. Pericyte depletion was further associated with increased hypoxia, epithelial-to-mesenchymal transition (EMT), and Met receptor activation. Silencing of Twist or use of a Met inhibitor suppressed hypoxia and EMT/Met-driven metastasis. In addition, poor pericyte coverage coupled with high Met expression in cancer cells speculates the worst prognosis for patients with invasive breast cancer. Collectively, our study suggests that pericytes within the primary tumor microenvironment likely serve as important gatekeepers against cancer progression and metastasis.National Institutes of Health (U.S.) (NIH Grant CA125550)National Institutes of Health (U.S.) (NIH grant CA155370)National Institutes of Health (U.S.) (NIH Grant CA151925)National Institutes of Health (U.S.) (NIH Grant DK81576)National Institutes of Health (U.S.) (NIH Grant CA163191)National Institutes of Health (U.S.) (NIH grant DK55001)Champalimaud Foundation (Champalimaud metastasis programme)Champalimaud Foundation (Champalimaud investigator)National Institutes of Health (U.S.) (NRSA F32 Ruth Kirschstein Postdoctoral Fellowship from NIH/NIDDK (5F32DK082119-02))National Institutes of Health (U.S.) (NIH Research Training Grant in Gastroenterology (2T32DK007760-11))National Institutes of Health (U.S.) (NIH Research Training Grant in Cancer Biology (5T32CA081156-08))United States. Dept. of Defense (DoD Breast Cancer Research Predoctoral Traineeship Award (W81XWH-09-1-0008))National Institutes of Health (U.S.) (NIH Research Training Grant in Cardiovascular Medicine (5T32HL007374-30))United Negro College Fund/Merck (Postdoctoral Science Research Fellowship)National Institutes of Health (U.S.) (NIH supplemental grant (CA125550)

Inhibition of wild-type p53-expressing AML by the novel small molecule HDM2 inhibitor CGM097

The tumor suppressor p53 is a key regulator of apoptosis and functions upstream in the apoptotic cascade by both indirectly and directly regulating Bcl-2 family proteins. In cells expressing wild-type (WT) p53, the HDM2 protein binds to p53 and blocks its activity. Inhibition of HDM2:p53 interaction activates p53 and causes apoptosis or cell-cycle arrest. Here, we investigated the ability of the novel HDM2 inhibitor CGM097 to potently and selectively kill WT p53-expressing AML cells. The antileukemic effects of CGM097 were studied using cellbased proliferation assays (human AML cell lines, primary AML patient cells, and normal bone marrow samples), apoptosis, and cell-cycle assays, ELISA, immunoblotting, and an AML patient-derived in vivo mouse model. CGM097 potently and selectively inhibited the proliferation of human AML cell lines and the majority of primary AML cells expressing WT p53, but not mutant p53, in a target-specific manner. Several patient samples that harbored mutant p53 were comparatively unresponsive to CGM097. Synergy was observed when CGM097 was combined with FLT3 inhibition against oncogenic FLT3-expressing cells cultured both in the absence as well as the presence of cytoprotective stromal-secreted cytokines, as well as when combined with MEK inhibition in cells with activated MAPK signaling. Finally, CGM097 was effective in reducing leukemia burden in vivo. These data suggest that CGM097 is a promising treatment for AML characterized as harboring WT p53 as a single agent, as well as in combination with other therapies targeting oncogene-activated pathways that drive AML

Discovery of Darovasertib (NVP-LXS196), a Pan-PKC Inhibitor for the Treatment of Metastatic Uveal Melanoma

Uveal melanoma (UM) is the most common primary intraocular malignancy in the adult eye. Despite the aggressive local management of primary UM, the development of metastases is common with no effective treatment options for metastatic disease. Genetic analysis of UM samples reveals the presence of mutually exclusive activating mutations in the Gq alpha subunits GNAQ and GNA11. One of the key downstream targets of the constitutively active Gq alpha subunits is the protein kinase C (PKC) signaling pathway. Herein, we describe the discovery of darovasertib (NVP-LXS196), a potent pan-PKC inhibitor with high whole kinome selectivity. The lead series was optimized for kinase and off target selectivity to afford a compound that is rapidly absorbed and well tolerated in preclinical species. LXS196 is being investigated in the clinic as a monotherapy and in combination with other agents for the treatment of uveal melanoma (UM), including primary UM and metastatic uveal melanoma (MUM)

Discovery of Darovasertib (NVP-LXS196), a Pan-PKC Inhibitor for the Treatment of Metastatic Uveal Melanoma

Uveal melanoma (UM) is the most common primary intraocular malignancy in the adult eye. Despite the aggressive local management of primary UM, the development of metastases is common with no effective treatment options for metastatic disease. Genetic analysis of UM samples reveals the presence of mutually exclusive activating mutations in the Gq alpha subunits GNAQ and GNA11. One of the key downstream targets of the constitutively active Gq alpha subunits is the protein kinase C (PKC) signaling pathway. Herein, we describe the discovery of darovasertib (NVP-LXS196), a potent pan-PKC inhibitor with high whole kinome selectivity. The lead series was optimized for kinase and off target selectivity to afford a compound that is rapidly absorbed and well tolerated in preclinical species. LXS196 is being investigated in the clinic as a monotherapy and in combination with other agents for the treatment of uveal melanoma (UM), including primary UM and metastatic uveal melanoma (MUM)

Pharmacological and genomic profiling identifies NF-κB-targeted treatment strategies for mantle cell lymphoma

Mantle cell lymphoma (MCL) is an aggressive malignancy that is characterized by poor prognosis. Large-scale pharmacological profiling across more than 100 hematological cell line models identified a subset of MCL cell lines that are highly sensitive to the B cell receptor (BCR) signaling inhibitors ibrutinib and sotrastaurin. Sensitive MCL models exhibited chronic activation of the BCR-driven classical nuclear factor-{kappa}B (NF-{kappa}B) pathway, whereas insensitive cell lines displayed activation of the alternative NF-{kappa}B pathway. Transcriptome sequencing revealed genetic lesions in alternative NF-{kappa}B pathway signaling components in ibrutinib-insensitive cell lines, and sequencing of 165 samples from patients with MCL identified recurrent mutations in TRAF2 or BIRC3 in 15% of these individuals. Although they are associated with insensitivity to ibrutinib, lesions in the alternative NF-{kappa}B pathway conferred dependence on the protein kinase NIK (also called mitogen-activated protein 3 kinase 14 or MAP3K14) both in vitro and in vivo. Thus, NIK is a new therapeutic target for MCL treatment, particularly for lymphomas that are refractory to BCR pathway inhibitors. Our findings reveal a pattern of mutually exclusive activation of the BCR-NF-{kappa}B or NIK-NF-{kappa}B pathways in MCL and provide critical insights into patient stratification strategies for NF-{kappa}B pathway-targeted agents