Nucleophosmin (NPM1) is amongst the most frequently mutated genes in acute myeloid leukemia (AML). It is not known, however, how the resulting oncoprotein mutant-NPM1 is leukemogenic. To reveal the cellular machinery in which NPM1 participates in myeloid cells, we analyzed the endogenous NPM1 protein-interactome by mass-spectrometry, and discovered abundant amounts of the master transcription factor driver of monocyte lineage-differentiation PU.1 (SPI1). Mutant-NPM1, which aberrantly accumulates in cytoplasm, dislocated PU.1 into cytoplasm with it. CEBPA and RUNX1, the master transcription factors that collaborate with PU.1 to activate granulo-monocytic lineage-fates, remained nuclear, but without PU.1, their coregulator interactions were toggled from coactivators to corepressors, repressing instead of activating greater than 500 granulocyte and monocyte terminal-differentiation genes. An inhibitor of nuclear export, selinexor, by locking mutant-NPM1/PU.1 in the nucleus, activated terminal monocytic fates. Direct depletion of the corepressor DNA methyltransferase 1 (DNMT1) from the CEBPA/RUNX1 protein interactome using the clinical drug decitabine activated terminal granulocytic fates. Together, these non-cytotoxic treatments extended survival by greater than 160 days versus vehicle in a patient-derived xenotransplant model of NPM1/FLT3-mutated AML. In sum, mutant-NPM1 represses monocyte and granulocyte terminal-differentiation by disrupting PU.1/CEBPA/RUNX1 collaboration, a transforming action that can be reversed by pharmacodynamically-directed dosing of clinical small molecules.
Xiaorong Gu, Quteba Ebrahem, Reda Z. Mahfouz, Metis Hasipek, Francis Enane, Tomas Radivoyevitch, Nicolas Rapin, Bartlomiej Przychodzen, Zhenbo Hu, Ramesh Balusu, Claudiu V. Cotta, David Wald, Christian Argueta, Yosef Landesman, Maria Paola Martelli, Brunangelo Falini, Hetty Carraway, Bo T. Porse, Jaroslaw P. Maciejewski, Babal K. Jha, Yogen Saunthararajah
Genome-wide association studies have repeatedly mapped susceptibility loci for emphysema to genes that modify hedgehog signaling, but the functional relevance of hedgehog signaling to this morbid disease remains unclear. In the current study, we identified a broad population of mesenchymal cells in the adult murine lung receptive to hedgehog signaling, characterized by higher activation of hedgehog surrounding the proximal airway relative to the distal alveoli. Single cell RNA-sequencing showed that the hedgehog-receptive mesenchyme is composed of mostly fibroblasts with distinct proximal and distal subsets with discrete identities. Ectopic hedgehog activation in the distal fibroblasts promoted expression of proximal fibroblast markers, and promoted loss of distal alveoli and airspace enlargement of over twenty percent compared to controls. We found that hedgehog suppressed mesenchymal-derived mitogens enriched in distal fibroblasts that regulate alveolar stem cell regeneration and airspace size. Finally, single cell analysis of the human lung mesenchyme showed that segregated proximal-distal identity with preferential hedgehog activation in the proximal fibroblasts is conserved between mice and humans. In conclusion, we showed that differential hedgehog activation segregates mesenchymal identities of distinct fibroblast subsets, and disruption of fibroblast identity can alter the alveolar stem cell niche leading to emphysematous changes in the murine lung.
Chaoqun Wang, Nabora S. Reyes de Mochel, Stephanie A. Christenson, Monica Cassandras, Rebecca Moon, Alexis N. Brumwell, Lauren E. Byrnes, Alfred Li, Yasuyuki Yokosaki, Peiying Shan, Julie B. Sneddon, David Jablons, Patty J. Lee, Michael A. Matthay, Harold A. Chapman, Tien Peng
Induction of TLR2 activation depends on its association with adapter protein MyD88. We have found that levels of TLR2 and MyD88 are elevated in the hippocampus and cortex of Alzheimer’s disease (AD) patients and 5XFAD mouse model of AD. Since there is no specific inhibitor of TLR2, to target induced TLR2 from therapeutic angle, we engineered a peptide corresponding to the TLR2-interacting domain of MyD88 (TIDM) that binds to the BB loop of only TLR2, but not other TLRs. Interestingly, wild type (wt) TIDM peptide inhibited microglial activation induced by fibrillar Aβ1-42 and lipoteichoic acid, but not 1-methyl-4-phenylpyridinium, double-stranded RNA, bacterial lipopolysaccharide, flagellin, and CpG DNA. After intranasal administration, wtTIDM peptide reached the hippocampus, reduced hippocampal glial activation, lowered Aβ burden, attenuated neuronal apoptosis, and improved memory and learning in 5XFAD mice. However, wtTIDM peptide was not effective in 5XFAD mice lacking TLR2. In addition to 5XFAD mice, wtTIDM peptide also suppressed the disease process in mice with experimental allergic encephalomyelitis and collagen-induced arthritis. Therefore, selective targeting of activated status of one component of the innate immune system by wtTIDM peptide may be beneficial in AD as well as other disorders in which TLR2-MyD88 signaling plays a role in disease pathogenesis.
Suresh B. Rangasamy, Malabendu Jana, Avik Roy, Grant T. Corbett, Madhuchhanda Kundu, Sujyoti Chandra, Susanta Mondal, Sridevi Dasarathi, Elliott J. Mufson, Rama K. Mishra, Chi-Hao Luan, David A. Bennett, Kalipada Pahan
Anaplastic thyroid carcinomas (ATC) have a high prevalence of BRAF and TP53 mutations. A trial of vemurafenib in non-melanoma BRAFV600E-mutant cancers showed significant, although short-lived, responses in ATCs, indicating that these virulent tumors remain addicted to BRAF despite their high mutation burden. To explore the mechanisms mediating acquired resistance to BRAF blockade we generated mice with thyroid-specific deletion of p53 and dox-dependent expression of BRAFV600E, 50% of which developed ATCs after dox treatment. Upon dox withdrawal there was complete regression in all mice, although recurrences were later detected in 85% of animals. The relapsed tumors had elevated MAPK transcriptional output, and retained responses to the MEK/RAF inhibitor CH5126766 in vivo and in vitro. Whole exome sequencing identified recurrent focal amplifications of chromosome 6, with a minimal region of overlap that included Met. Met-amplified recurrences overexpressed the receptor as well as its ligand Hgf. Growth, signaling and viability of Met-amplified tumor cells were suppressed in vitro and in vivo by the Met kinase inhibitors PF-04217903 and crizotinib, whereas primary ATCs and Met-diploid relapses were resistant. Hence, recurrences are the rule after BRAF suppression in murine ATCs, most commonly due to activation of HGF/MET signaling, which generates exquisite dependency to MET kinase inhibitors.
Jeffrey A. Knauf, Kathleen A. Luckett, Kuen-Yuan Chen, Francesca Voza, Nicholas D. Socci, Ronald Ghossein, James A. Fagin
No posts were found with this tag.