The molecular mechanisms that transduce the osteoblast response to physical forces in the bone microenvironment are poorly understood. Here, we used genetic and pharmacological experiments to determine whether the polycystins PC1 and PC2 (encoded by Pkd1 and Pkd2) and the transcriptional coactivator TAZ form a mechanosensing complex in osteoblasts. Compound-heterozygous mice lacking 1 copy of Pkd1 and Taz exhibited additive decrements in bone mass, impaired osteoblast-mediated bone formation, and enhanced bone marrow fat accumulation. Bone marrow stromal cells and osteoblasts derived from these mice showed impaired osteoblastogenesis and enhanced adipogenesis. Increased extracellular matrix stiffness and application of mechanical stretch to multipotent mesenchymal cells stimulated the nuclear translocation of the PC1 C-terminal tail/TAZ (PC1-CTT/TAZ) complex, leading to increased runt-related transcription factor 2–mediated (Runx2-mediated) osteogenic and decreased PPARγ-dependent adipogenic gene expression. Using structure-based virtual screening, we identified a compound predicted to bind to PC2 in the PC1:PC2 C-terminal tail region with helix:helix interaction. This molecule stimulated polycystin- and TAZ-dependent osteoblastogenesis and inhibited adipogenesis. Thus, we show that polycystins and TAZ integrate at the molecular level to reciprocally regulate osteoblast and adipocyte differentiation, indicating that the polycystins/TAZ complex may be a potential therapeutic target to increase bone mass.
Zhousheng Xiao, Jerome Baudry, Li Cao, Jinsong Huang, Hao Chen, Charles R. Yates, Wei Li, Brittany Dong, Christopher M. Waters, Jeremy C. Smith, L. Darryl Quarles
Medulloblastoma, an aggressive cancer of the cerebellum, is among the most common pediatric brain tumors. Approximately one-third of medulloblastomas are associated with misactivation of the Hedgehog (Hh) pathway. GLI family zinc finger 2 (GLI2) coordinates the Hh transcriptional program; however, the GLI2 targets that promote cancer cell proliferation are unknown. Here, we incorporated a Gli2-EGFP allele into 2 different genetic mouse models of Hh-associated medulloblastoma. Hh signaling induced GLI2 binding to the Cdk6 promoter and activated Cdk6 expression, thereby promoting uncontrolled cell proliferation. Genetic or pharmacological inhibition of CDK6 in mice repressed the growth of Hh-associated medulloblastoma and prolonged survival through inhibition of cell proliferation. In human medulloblastoma, misactivation of Hh signaling was associated with high levels of CDK6, pointing to CDK6 as a direct transcriptional target of the Hh pathway. These results suggest that CDK6 antagonists may be a promising therapeutic approach for Hh-associated medulloblastoma in humans.
David R. Raleigh, Pervinder K. Choksi, Alexis Leigh Krup, Wasima Mayer, Nicole Santos, Jeremy F. Reiter
The transcription factor PU.1 is often impaired in patients with acute myeloid leukemia (AML). Here, we used AML cells that already had low PU.1 levels and further inhibited PU.1 using either RNA interference or, to our knowledge, first-in-class small-molecule inhibitors of PU.1 that we developed specifically to allosterically interfere with PU.1-chromatin binding through interaction with the DNA minor groove that flanks PU.1-binding motifs. These small molecules of the heterocyclic diamidine family disrupted the interaction of PU.1 with target gene promoters and led to downregulation of canonical PU.1 transcriptional targets. shRNA or small-molecule inhibition of PU.1 in AML cells from either PU.1lo mutant mice or human patients with AML-inhibited cell growth and clonogenicity and induced apoptosis. In murine and human AML (xeno)transplantation models, treatment with our PU.1 inhibitors decreased tumor burden and resulted in increased survival. Thus, our study provides proof of concept that PU.1 inhibition has potential as a therapeutic strategy for the treatment of AML and for the development of small-molecule inhibitors of PU.1.
Iléana Antony-Debré, Ananya Paul, Joana Leite, Kelly Mitchell, Hye Mi Kim, Luis A. Carvajal, Tihomira I. Todorova, Kenneth Huang, Arvind Kumar, Abdelbasset A. Farahat, Boris Bartholdy, Swathi-Rao Narayanagari, Jiahao Chen, Alberto Ambesi-Impiombato, Adolfo A. Ferrando, Ioannis Mantzaris, Evripidis Gavathiotis, Amit Verma, Britta Will, David W. Boykin, W. David Wilson, Gregory M.K. Poon, Ulrich Steidl
Melanoma can be stratified into unique subtypes based on distinct pathologies. The acral/mucosal melanoma subtype is characterized by aberrant and constitutive activation of the proto-oncogene receptor tyrosine kinase C-KIT, which drives tumorigenesis. Treatment of these melanoma patients with C-KIT inhibitors has proven challenging, prompting us to investigate the downstream effectors of the C-KIT receptor. We determined that C-KIT stimulates MAP kinase–interacting serine/threonine kinases 1 and 2 (MNK1/2), which phosphorylate eukaryotic translation initiation factor 4E (eIF4E) and render it oncogenic. Depletion of MNK1/2 in melanoma cells with oncogenic C-KIT inhibited cell migration and mRNA translation of the transcriptional repressor SNAI1 and the cell cycle gene CCNE1. This suggested that blocking MNK1/2 activity may inhibit tumor progression, at least in part, by blocking translation initiation of mRNAs encoding cell migration proteins. Moreover, we developed an MNK1/2 inhibitor (SEL201), and found that SEL201-treated KIT-mutant melanoma cells had lower oncogenicity and reduced metastatic ability. Clinically, tumors from melanoma patients harboring KIT mutations displayed a marked increase in MNK1 and phospho-eIF4E. Thus, our studies indicate that blocking MNK1/2 exerts potent antimelanoma effects and support blocking MNK1/2 as a potential strategy to treat patients positive for KIT mutations.
Yao Zhan, Jun Guo, William Yang, Christophe Goncalves, Tomasz Rzymski, Agnieszka Dreas, Eliza Żyłkiewicz, Maciej Mikulski, Krzysztof Brzózka, Aniela Golas, Yan Kong, Meng Ma, Fan Huang, Bonnie Huor, Qianyu Guo, Sabrina Daniela da Silva, Jose Torres, Yutian Cai, Ivan Topisirovic, Jie Su, Krikor Bijian, Moulay A. Alaoui-Jamali, Sidong Huang, Fabrice Journe, Ghanem E. Ghanem, Wilson H. Miller Jr., Sonia V. del Rincón
The mammalian target of rapamycin complex 1 (mTORC1) kinase promotes cell growth by activating biosynthetic pathways and suppressing catabolic pathways, particularly that of macroautophagy. A prerequisite for mTORC1 activation is its translocation to the lysosomal surface. Deregulation of mTORC1 has been associated with the pathogenesis of several diseases, but its role in skeletal disorders is largely unknown. Here, we show that enhanced mTORC1 signaling arrests bone growth in lysosomal storage disorders (LSDs). We found that lysosomal dysfunction induces a constitutive lysosomal association and consequent activation of mTORC1 in chondrocytes, the cells devoted to bone elongation. mTORC1 hyperphosphorylates the protein UV radiation resistance–associated gene (UVRAG), reducing the activity of the associated Beclin 1–Vps34 complex and thereby inhibiting phosphoinositide production. Limiting phosphoinositide production leads to a blockage of the autophagy flux in LSD chondrocytes. As a consequence, LSD chondrocytes fail to properly secrete collagens, the main components of the cartilage extracellular matrix. In mouse models of LSD, normalization of mTORC1 signaling or stimulation of the Beclin 1–Vps34–UVRAG complex rescued the autophagy flux, restored collagen levels in cartilage, and ameliorated the bone phenotype. Taken together, these data unveil a role for mTORC1 and autophagy in the pathogenesis of skeletal disorders and suggest potential therapeutic approaches for the treatment of LSDs.
Rosa Bartolomeo, Laura Cinque, Chiara De Leonibus, Alison Forrester, Anna Chiara Salzano, Jlenia Monfregola, Emanuela De Gennaro, Edoardo Nusco, Isabella Azario, Carmela Lanzara, Marta Serafini, Beth Levine, Andrea Ballabio, Carmine Settembre
Blood vessels in the tumor periphery have high pericyte coverage and are resistant to vascular disrupting agents (VDAs). VDA treatment resistance leads to a viable peripheral tumor rim that contributes to treatment failure and disease recurrence. Here, we provide evidence to support a hypothesis that shifting the target of VDAs from tumor vessel endothelial cells to pericytes disrupts tumor peripheral vessels and the viable rim, circumventing VDA treatment resistance. Through chemical engineering, we developed Z-GP-DAVLBH (from the tubulin-binding VDA desacetylvinblastine monohydrazide [DAVLBH]) as a prodrug that can be selectively activated by fibroblast activation protein α (FAPα) in tumor pericytes. Z-GP-DAVLBH selectively destroys the cytoskeleton of FAPα-expressing tumor pericytes, disrupting blood vessels both within the core and around the periphery of tumors. As a result, Z-GP-DAVLBH treatment eradicated the otherwise VDA-resistant tumor rim and led to complete regression of tumors in multiple lines of xenografts without producing the drug-related toxicity that is associated with similar doses of DAVLBH. This study demonstrates that targeting tumor pericytes with an FAPα-activated VDA prodrug represents a potential vascular disruption strategy in overcoming tumor resistance to VDA treatments.
Minfeng Chen, Xueping Lei, Changzheng Shi, Maohua Huang, Xiaobo Li, Baojian Wu, Zhengqiu Li, Weili Han, Bin Du, Jianyang Hu, Qiulin Nie, Weiqian Mai, Nan Ma, Nanhui Xu, Xinyi Zhang, Chunlin Fan, Aihua Hong, Minghan Xia, Liangping Luo, Ande Ma, Hongsheng Li, Qiang Yu, Heru Chen, Dongmei Zhang, Wencai Ye
Thiazide diuretics are among the most widely used treatments for hypertension, but thiazide-induced hyponatremia (TIH), a clinically significant adverse effect, is poorly understood. Here, we have studied the phenotypic and genetic characteristics of patients hospitalized with TIH. In a cohort of 109 TIH patients, those with severe TIH displayed an extended phenotype of intravascular volume expansion, increased free water reabsorption, urinary prostaglandin E2 excretion, and reduced excretion of serum chloride, magnesium, zinc, and antidiuretic hormone. GWAS in a separate cohort of 48 TIH patients and 2,922 controls from the 1958 British birth cohort identified an additional 14 regions associated with TIH. We identified a suggestive association with a variant in SLCO2A1, which encodes a prostaglandin transporter in the distal nephron. Resequencing of SLCO2A1 revealed a nonsynonymous variant, rs34550074 (p.A396T), and association with this SNP was replicated in a second cohort of TIH cases. TIH patients with the p.A396T variant demonstrated increased urinary excretion of prostaglandin E2 and metabolites. Moreover, the SLCO2A1 phospho-mimic p.A396E showed loss of transporter function in vitro. These findings indicate that the phenotype of TIH involves a more extensive metabolic derangement than previously recognized. We propose one mechanism underlying TIH development in a subgroup of patients in which SLCO2A1 regulation is altered.
James S. Ware, Louise V. Wain, Sarath K. Channavajjhala, Victoria E. Jackson, Elizabeth Edwards, Run Lu, Keith Siew, Wenjing Jia, Nick Shrine, Sue Kinnear, Mahli Jalland, Amanda P. Henry, Jenny Clayton, Kevin M. O’Shaughnessy, Martin D. Tobin, Victor Schuster, Stuart Cook, Ian P. Hall, Mark Glover
Fibrodysplasia ossificans progressiva (FOP) is a rare and intractable disease characterized by extraskeletal bone formation through endochondral ossification. Patients with FOP harbor point mutations in ACVR1, a type I receptor for BMPs. Although mutated ACVR1 (FOP-ACVR1) has been shown to render hyperactivity in BMP signaling, we and others have uncovered a mechanism by which FOP-ACVR1 mistransduces BMP signaling in response to Activin-A, a molecule that normally transduces TGF-β signaling. Although Activin-A evokes enhanced chondrogenesis in vitro and heterotopic ossification (HO) in vivo, the underlying mechanisms have yet to be revealed. To this end, we developed a high-throughput screening (HTS) system using FOP patient–derived induced pluripotent stem cells (FOP-iPSCs) to identify pivotal pathways in enhanced chondrogenesis that are initiated by Activin-A. In a screen of 6,809 small-molecule compounds, we identified mTOR signaling as a critical pathway for the aberrant chondrogenesis of mesenchymal stromal cells derived from FOP-iPSCs (FOP-iMSCs). Two different HO mouse models, an FOP model mouse expressing FOP-ACVR1 and an FOP-iPSC–based HO model mouse, revealed critical roles for mTOR signaling in vivo. Moreover, we identified ENPP2, an enzyme that generates lysophosphatidic acid, as a linker of FOP-ACVR1 and mTOR signaling in chondrogenesis. These results uncovered the crucial role of the Activin-A/FOP-ACVR1/ENPP2/mTOR axis in FOP pathogenesis.
Kyosuke Hino, Kazuhiko Horigome, Megumi Nishio, Shingo Komura, Sanae Nagata, Chengzhu Zhao, Yonghui Jin, Koichi Kawakami, Yasuhiro Yamada, Akira Ohta, Junya Toguchida, Makoto Ikeya
Preferentially expressed antigen in melanoma (PRAME) is a cancer-testis antigen that is expressed in many cancers and leukemias. In healthy tissue, PRAME expression is limited to the testes and ovaries, making it a highly attractive cancer target. PRAME is an intracellular protein that cannot currently be drugged. After proteasomal processing, the PRAME300–309 peptide ALYVDSLFFL (ALY) is presented in the context of human leukocyte antigen HLA-A*02:01 molecules for recognition by the T cell receptor (TCR) of cytotoxic T cells. Here, we have described Pr20, a TCR mimic (TCRm) human IgG1 antibody that recognizes the cell-surface ALY peptide/HLA-A2 complex. Pr20 is an immunological tool and potential therapeutic agent. Pr20 bound to PRAME+HLA-A2+ cancers. An afucosylated Fc form (Pr20M) directed antibody-dependent cellular cytotoxicity against PRAME+HLA-A2+ leukemia cells and was therapeutically effective against mouse xenograft models of human leukemia. In some tumors, Pr20 binding markedly increased upon IFN-γ treatment, mediated by induction of the immunoproteasome catalytic subunit β5i. The immunoproteasome reduced internal destructive cleavages within the ALY epitope compared with the constitutive proteasome. The data provide rationale for developing TCRm antibodies as therapeutic agents for cancer, offer mechanistic insight on proteasomal regulation of tumor-associated peptide/HLA antigen complexes, and yield possible therapeutic solutions to target antigens with ultra-low surface presentation.
Aaron Y. Chang, Tao Dao, Ron S. Gejman, Casey A. Jarvis, Andrew Scott, Leonid Dubrovsky, Melissa D. Mathias, Tatyana Korontsvit, Victoriya Zakhaleva, Michael Curcio, Ronald C. Hendrickson, Cheng Liu, David A. Scheinberg
Primary effusion lymphoma (PEL) is a largely incurable malignancy of B cell origin with plasmacytic differentiation. Here, we report the identification of a highly effective inhibitor of PEL. This compound, 6-ethylthioinosine (6-ETI), is a nucleoside analog with toxicity to PEL in vitro and in vivo, but not to other lymphoma cell lines tested. We developed and performed resistome analysis, an unbiased approach based on RNA sequencing of resistant subclones, to discover the molecular mechanisms of sensitivity. We found different adenosine kinase–inactivating (ADK-inactivating) alterations in all resistant clones and determined that ADK is required to phosphorylate and activate 6-ETI. Further, we observed that 6-ETI induces ATP depletion and cell death accompanied by S phase arrest and DNA damage only in ADK-expressing cells. Immunohistochemistry for ADK served as a biomarker approach to identify 6-ETI–sensitive tumors, which we documented for other lymphoid malignancies with plasmacytic features. Notably, multiple myeloma (MM) expresses high levels of ADK, and 6-ETI was toxic to MM cell lines and primary specimens and had a robust antitumor effect in a disseminated MM mouse model. Several nucleoside analogs are effective in treating leukemias and T cell lymphomas, and 6-ETI may fill this niche for the treatment of PEL, plasmablastic lymphoma, MM, and other ADK-expressing cancers.
Utthara Nayar, Jouliana Sadek, Jonathan Reichel, Denise Hernandez-Hopkins, Gunkut Akar, Peter J. Barelli, Michelle A. Sahai, Hufeng Zhou, Jennifer Totonchy, David Jayabalan, Ruben Niesvizky, Ilaria Guasparri, Duane Hassane, Yifang Liu, Shizuko Sei, Robert H. Shoemaker, J. David Warren, Olivier Elemento, Kenneth M. Kaye, Ethel Cesarman
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