Myc activation is a primary oncogenic event in many human cancers; however, these transcription factors are difficult to inhibit pharmacologically, suggesting that Myc-dependent downstream effectors may be more tractable therapeutic targets. Here we show that Myc overexpression induces endoplasmic reticulum (ER) stress and engages the IRE1α-XBP1 pathway through multiple molecular mechanisms in a variety of c-Myc- and N-Myc-dependent cancers. In particular, Myc-overexpressing cells require IRE1α-XBP1 signaling for sustained growth and survival in vitro and in vivo, dependent on elevated stearoyl-CoA-desaturase 1 (SCD1) activity. Pharmacological and genetic XBP1 inhibition induces Myc-dependent apoptosis, which is alleviated by exogenous unsaturated fatty acids. Of note, SCD1 inhibition phenocopies IRE1α RNase activity suppression in vivo. Furthermore, IRE1α inhibition enhances the cytotoxic effects of standard chemotherapy drugs used to treat c-Myc-overexpressing Burkitt’s lymphoma, suggesting that inhibiting the IRE1α-XBP1 pathway is a useful general strategy for treatment of Myc-driven cancers.
Hong Xie, Chih-Hang Anthony Tang, Jun H. Song, Anthony Mancuso, Juan R. Del Valle, Jin Cao, Yan Xiang, Chi V. Dang, Roy Lan, Danielle J. Sanchez, Brian Keith, Chih-Chi Andrew Hu, M. Celeste Simon
Aberrant activation of MAPK signaling leads to activation of oncogenic transcriptomes. How MAPK signaling is coupled with transcriptional response in cancer is not fully understood. In gastrointestinal stromal tumor and melanoma, both with oncogenic MAPK activation, we find that ETV1 and other Pea3-ETS transcription factors are critical nuclear effectors of MAPK signaling that are regulated through protein stability. Expression of stabilized Pea3-ETS factors can partially rescue the MAPK transcriptome and cell viability after MAPK inhibition. To identify players involved in this process, we performed a pooled genome-wide RNAi screen using a novel fluorescence-based ETV1 protein stability sensor, and identified COP1, DET1, DDB1, UBE3C, PSMD4, and COP9 signalosome members. COP1 and DET1 loss led to decoupling between MAPK signaling and downstream transcriptional response, where MAPK inhibition failed to destabilize Pea3 factors and fully inhibit the MAPK transcriptome, thus resulting in decreased sensitivity to MAPK pathway inhibitors. We identified multiple COP1 and DET1 mutations in human tumors that were defective in degradation of Pea3-ETS factors. Two melanoma patients had de novo DET1 mutations arising after vemurafenib treatment. These observations indicate that MAPK signaling-dependent regulation of Pea3-ETS protein stability is a key signaling node in oncogenesis and therapeutic resistance to MAPK pathway inhibition.
Yuanyuan Xie, Zhen Cao, Elissa W.P. Wong, Youxin Guan, Wenfu Ma, Jenny Q. Zhang, Edward G. Walczak, Devan Murphy, Leili Ran, Inna Sirota, Shangqian Wang, Shipra Shukla, Dong Gao, Simon R.V. Knott, Kenneth Chang, Justin Leu, John Wongvipat, Cristina R. Antonescu, Gregory Hannon, Ping Chi, Yu Chen
Blockade of the checkpoint inhibitor programmed death 1 (PD1) has demonstrated remarkable success in the clinic for the treatment of cancer; however, a majority of tumors are resistant to anti-PD1 monotherapy. Numerous ongoing clinical combination therapy studies will likely reveal additional therapeutics that complement anti-PD1 blockade. Recent studies found that immunogenic cell death (ICD) improves T cell responses against different tumors, thus indicating that ICD may further augment antitumor immunity elicited by anti-PD1. Here, we observed antitumor activity following combinatorial therapy with anti-PD1 Ab and the cyclin-dependent kinase inhibitor dinaciclib in immunocompetent mouse tumor models. Dinaciclib induced a type I IFN gene signature within the tumor, leading us to hypothesize that dinaciclib potentiates the effects of anti-PD1 by eliciting ICD. Indeed, tumor cells treated with dinaciclib showed the hallmarks of ICD including surface calreticulin expression and release of high mobility group box 1 (HMGB1) and ATP. Mice treated with both anti-PD1 and dinaciclib showed increased T cell infiltration and DC activation within the tumor, indicating that this combination improves the overall quality of the immune response generated. These findings identify a potential mechanism for the observed benefit of combining dinaciclib and anti-PD1, in which dinaciclib induces ICD, thereby converting the tumor cell into an endogenous vaccine and boosting the effects of anti-PD1.
Dewan Md Sakib Hossain, Sarah Javaid, Mingmei Cai, Chunsheng Zhang, Anandi Sawant, Marlene Hinton, Manjiri Sathe, Jeff Grein, Wendy Blumenschein, Elaine M. Pinheiro, Alissa Chackerian
Charcot-Marie-Tooth disease type 1A (CMT1A) is caused by duplication of peripheral myelin protein 22 (PMP22) and is the most common hereditary peripheral neuropathy. CMT1A is characterized by demyelination and axonal loss, which underlie slowed motor nerve conduction velocity (MNCV) and reduced compound muscle action potentials (CMAP) in patients. There is currently no known treatment for this disease. Here, we show that antisense oligonucleotides (ASOs) effectively suppress PMP22 mRNA in affected nerves in 2 murine CMT1A models. Notably, initiation of ASO treatment after disease onset restored myelination, MNCV, and CMAP almost to levels seen in WT animals. In addition to disease-associated gene expression networks that were restored with ASO treatment, we also identified potential disease biomarkers through transcriptomic profiling. Furthermore, we demonstrated that reduction of PMP22 mRNA in skin biopsies from ASO-treated rats is a suitable biomarker for evaluating target engagement in response to ASO therapy. These results support the use of ASOs as a potential treatment for CMT1A and elucidate potential disease and target engagement biomarkers for use in future clinical trials.
Hien Tran Zhao, Sagar Damle, Karli Ikeda-Lee, Steven Kuntz, Jian Li, Apoorva Mohan, Aneeza Kim, Gene Hung, Mark A. Scheideler, Steven S. Scherer, John Svaren, Eric E. Swayze, Holly B. Kordasiewicz
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
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