Curtis Thorne

Interests

Research

My laboratory investigates the signaling mechanisms controlling cell fate and tissue homeostasis of the intestine. We utilizes the fascinating characteristics of ex vivo organoid cultures of intestinal stem cells to address fundamental questions in cell and cancer biology: How do cells identify, measure, and respond to each other and to their environment? What are the signals that control the renewal and regeneration of intestinal tissues? How do these signals malfunction in colorectal cancer? Our long-term goal is to uncover an underlying circuit theory behind these behaviors – a set of predictive principles that tell us how complex functionality arises from simpler biological components. We have a particular interest in kinase networks that regulate healthy tissue homeostasis and are dis-regulated in cancer. Through our quantitative high-throughput imaging and drug discovery efforts, we are finding new ways to understand and repair these networks.

Courses

Scholarly Contributions

Journals/Publications

• Senthil Kumar, S., Gunda, V., Reinartz, D. M., Pond, K. W., Thorne, C. A., Santiago Raj, P. V., Johnson, M. D., & Wilson, J. E. (2024). Oral streptococci and induce distinct morphological, inflammatory, and metabolic signatures in macrophages. Infection and immunity, e0053623.
  More info

  Oral streptococci, key players in oral biofilm formation, are implicated in oral dysbiosis and various clinical conditions, including dental caries, gingivitis, periodontal disease, and oral cancer. Specifically, is associated with esophageal, gastric, and pharyngeal cancers, while is linked to oral cancer. However, no study has investigated the mechanistic links between these species and cancer-related inflammatory responses. As an initial step, we probed the innate immune response triggered by and in RAW264.7 macrophages. These bacteria exerted time- and dose-dependent effects on macrophage morphology without affecting cell viability. Compared with untreated macrophages, macrophages infected with exhibited a robust proinflammatory response characterized by significantly increased levels of inflammatory cytokines and mediators, including TNF, IL-6, IL-1β, NOS2, and COX2, accompanied by enhanced NF-κB activation. In contrast, -infected macrophages failed to elicit a robust inflammatory response. Seahorse Xfe96 analysis revealed an increased extracellular acidification rate in macrophages infected with compared with . At the 24-h time point, the presence of led to reduced extracellular itaconate, while triggered increased itaconate levels, highlighting distinct metabolic profiles in macrophages during infection in contrast to aconitate decarboxylase expression observed at the 6-h time point. This initial investigation highlights how and , two Gram-positive bacteria from the same genus, can prompt distinct immune responses and metabolic shifts in macrophages during infection.IMPORTANCEThe surge in head and neck cancer cases among individuals devoid of typical risk factors such as Human Papilloma Virus (HPV) infection and tobacco and alcohol use sparks an argumentative discussion around the emerging role of oral microbiota as a novel risk factor in oral squamous cell carcinoma (OSCC). While substantial research has dissected the gut microbiome's influence on physiology, the oral microbiome, notably oral streptococci, has been underappreciated during mucosal immunopathogenesis. , a viridans streptococci group, has been linked to abscess formation and an elevated presence in esophageal cancer and OSCC. The current study aims to probe the innate immune response to compared with the early colonizer as an important first step toward understanding the impact of distinct oral species on the host immune response, which is an understudied determinant of OSCC development and progression.
• Kang, H., Fitch, J. C., Varghese, R. P., Thorne, C. A., & Cusanovich, D. A. (2023). SGRN: A Cas12a-driven Synthetic Gene Regulatory Network System. bioRxiv : the preprint server for biology.
  More info

  Gene regulatory networks, which control gene expression patterns in development and in response to stimuli, use regulatory logic modules to coordinate inputs and outputs. One example of a regulatory logic module is the gene regulatory cascade (GRC), where a series of transcription factor genes turn on in order. Synthetic biologists have derived artificial systems that encode regulatory rules, including GRCs. Furthermore, the development of single-cell approaches has enabled the discovery of gene regulatory modules in a variety of experimental settings. However, the tools available for validating these observations remain limited. Based on a synthetic GRC using DNA cutting-defective Cas9 (dCas9), we designed and implemented an alternative synthetic GRC utilizing DNA cutting-defective Cas12a (dCas12a). Comparing the ability of these two systems to express a fluorescent reporter, the dCas9 system was initially more active, while the dCas12a system was more streamlined. Investigating the influence of individual components of the systems identified nuclear localization as a major driver of differences in activity. Improving nuclear localization for the dCas12a system resulted in 1.5-fold more reporter-positive cells and a 15-fold increase in reporter intensity relative to the dCas9 system. We call this optimized system the "Synthetic Gene Regulatory Network" (SGRN, pronounced "sojourn").
• Lasick, K. A., Jose, E., Samayoa, A. M., Shanks, L., Pond, K. W., Thorne, C. A., & Paek, A. L. (2023). FOXO Nuclear Shuttling Dynamics are Stimulus Dependent and Correspond with Cell Fate. Molecular biology of the cell, mbcE22050193.
  More info

  FOXO transcription factors are regulators of cellular homeostasis linked to increased lifespan and tumor suppression. FOXOs are activated by diverse cell stresses including serum starvation and oxidative stress. FOXO activity is regulated through post-translational modifications that control shuttling of FOXO proteins to the nucleus. In the nucleus, FOXOs upregulate genes in multiple, often conflicting pathways including cell-cycle arrest and apoptosis. How cells control FOXO activity to ensure the proper response for a given stress is an open question. Using quantitative immunofluorescence and live-cell imaging we found that the dynamics of FOXO nuclear shuttling are stimulus dependent and correspond with cell fate. HO treatment leads to an all-or-none response where some cells show no nuclear FOXO accumulation, while other cells show strong nuclear FOXO signal. The time that FOXO remains in the nucleus increases with dose and is linked with cell death. In contrast, serum starvation causes low amplitude pulses of nuclear FOXO and predominantly results in cell-cycle arrest. The accumulation of FOXO in the nucleus is linked with low AKT activity for both HO and serum starvation. Our findings suggest the dynamics of FOXO nuclear shuttling is one way in which the FOXO pathway dictates different cellular outcomes. [Media: see text] [Media: see text] [Media: see text].
• Song, H., Sontz, R. A., Vance, M. J., Morris, J. M., Sheriff, S., Zhu, S., Duan, S., Zeng, J., Koeppe, E., Pandey, R., Thorne, C. A., Stoffel, E. M., & Merchant, J. L. (2023). High-fat diet plus HNF1A variant promotes polyps by activating β-catenin in early-onset colorectal cancer. JCI insight, 8(13).
  More info

  The incidence of early-onset colorectal cancer (EO-CRC) is rising and is poorly understood. Lifestyle factors and altered genetic background possibly contribute. Here, we performed targeted exon sequencing of archived leukocyte DNA from 158 EO-CRC participants, which identified a missense mutation at p.A98V within the proximal DNA binding domain of Hepatic Nuclear Factor 1 α (HNF1AA98V, rs1800574). The HNF1AA98V exhibited reduced DNA binding. To test function, the HNF1A variant was introduced into the mouse genome by CRISPR/Cas9, and the mice were placed on either a high-fat diet (HFD) or high-sugar diet (HSD). Only 1% of the HNF1A mutant mice developed polyps on normal chow; however, 19% and 3% developed polyps on the HFD and HSD, respectively. RNA-Seq revealed an increase in metabolic, immune, lipid biogenesis genes, and Wnt/β-catenin signaling components in the HNF1A mutant relative to the WT mice. Mouse polyps and colon cancers from participants carrying the HNF1AA98V variant exhibited reduced CDX2 and elevated β-catenin proteins. We further demonstrated decreased occupancy of HNF1AA98V at the Cdx2 locus and reduced Cdx2 promoter activity compared with WT HNF1A. Collectively, our study shows that the HNF1AA98V variant plus a HFD promotes the formation of colonic polyps by activating β-catenin via decreasing Cdx2 expression.
• Chen, E. C., Gilchuk, P., Zost, S. J., Suryadevara, N., Winkler, E. S., Cabel, C. R., Binshtein, E., Chen, R. E., Sutton, R. E., Rodriguez, J., Day, S., Myers, L., Trivette, A., Williams, J. K., Davidson, E., Li, S., Doranz, B. J., Campos, S. K., Carnahan, R. H., , Thorne, C. A., et al. (2021). Convergent antibody responses to the SARS-CoV-2 spike protein in convalescent and vaccinated individuals. Cell reports, 36(8), 109604.
  More info

  Unrelated individuals can produce genetically similar clones of antibodies, known as public clonotypes, which have been seen in responses to different infectious diseases, as well as healthy individuals. Here we identify 37 public clonotypes in memory B cells from convalescent survivors of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection or in plasmablasts from an individual after vaccination with mRNA-encoded spike protein. We identify 29 public clonotypes, including clones recognizing the receptor-binding domain (RBD) in the spike protein S1 subunit (including a neutralizing, angiotensin-converting enzyme 2 [ACE2]-blocking clone that protects in vivo) and others recognizing non-RBD epitopes that bind the S2 domain. Germline-revertant forms of some public clonotypes bind efficiently to spike protein, suggesting these common germline-encoded antibodies are preconfigured for avid recognition. Identification of large numbers of public clonotypes provides insight into the molecular basis of efficacy of SARS-CoV-2 vaccines and sheds light on the immune pressures driving the selection of common viral escape mutants.
• Chen, E. C., Gilchuk, P., Zost, S. J., Suryadevara, N., Winkler, E. S., Cabel, C. R., Binshtein, E., Sutton, R. E., Rodriguez, J., Day, S., Myers, L., Trivette, A., Williams, J. K., Davidson, E., Li, S., Doranz, B. J., Campos, S. K., Carnahan, R. H., Thorne, C. A., , Diamond, M. S., et al. (2021). Convergent antibody responses to the SARS-CoV-2 spike protein in convalescent and vaccinated individuals. bioRxiv : the preprint server for biology.
  More info

  Unrelated individuals can produce genetically similar clones of antibodies, known as public clonotypes, which have been seen in responses to different infectious diseases as well as healthy individuals. Here we identify 37 public clonotypes in memory B cells from convalescent survivors of SARS-CoV-2 infection or in plasmablasts from an individual after vaccination with mRNA-encoded spike protein. We identified 29 public clonotypes, including clones recognizing the receptor-binding domain (RBD) in the spike protein S1 subunit (including a neutralizing, ACE2-blocking clone that protects ), and others recognizing non-RBD epitopes that bound the heptad repeat 1 region of the S2 domain. Germline-revertant forms of some public clonotypes bound efficiently to spike protein, suggesting these common germline-encoded antibodies are preconfigured for avid recognition. Identification of large numbers of public clonotypes provides insight into the molecular basis of efficacy of SARS-CoV-2 vaccines and sheds light on the immune pressures driving the selection of common viral escape mutants.
• Grant, A., Xicola, R. M., Nguyen, V., Lim, J., Thorne, C., Salhia, B., Llor, X., Ellis, N., & Padi, M. (2021). Molecular drivers of tumor progression in microsatellite stable APC mutation-negative colorectal cancers. Scientific reports, 11(1), 23507.
  More info

  The tumor suppressor gene adenomatous polyposis coli (APC) is the initiating mutation in approximately 80% of all colorectal cancers (CRC), underscoring the importance of aberrant regulation of intracellular WNT signaling in CRC development. Recent studies have found that early-onset CRC exhibits an increased proportion of tumors lacking an APC mutation. We set out to identify mechanisms underlying APC mutation-negative (APC) CRCs. We analyzed data from The Cancer Genome Atlas to compare clinical phenotypes, somatic mutations, copy number variations, gene fusions, RNA expression, and DNA methylation profiles between APC and APC mutation-positive (APC) microsatellite stable CRCs. Transcriptionally, APC CRCs clustered into two approximately equal groups. Cluster One was associated with enhanced mitochondrial activation. Cluster Two was strikingly associated with genetic inactivation or decreased RNA expression of the WNT antagonist RNF43, increased expression of the WNT agonist RSPO3, activating mutation of BRAF, or increased methylation and decreased expression of AXIN2. APC CRCs exhibited evidence of increased immune cell infiltration, with significant correlation between M2 macrophages and RSPO3. APC CRCs comprise two groups of tumors characterized by enhanced mitochondrial activation or increased sensitivity to extracellular WNT, suggesting that they could be respectively susceptible to inhibition of these pathways.
• Perez-Miller, S., Patek, M., Moutal, A., Duran, P., Cabel, C. R., Thorne, C. A., Campos, S. K., & Khanna, R. (2021). Novel Compounds Targeting Neuropilin Receptor 1 with Potential To Interfere with SARS-CoV-2 Virus Entry. ACS chemical neuroscience, 12(8), 1299-1312.
  More info

  Neuropilin-1 (NRP-1) is a multifunctional transmembrane receptor for ligands that affect developmental axonal growth and angiogenesis. In addition to a role in cancer, NRP-1 is a reported entry point for several viruses, including severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the causal agent of coronavirus disease 2019 (COVID-19). The furin cleavage product of SARS-CoV-2 Spike protein takes advantage of the vascular endothelial growth factor A (VEGF-A) binding site on NRP-1 which accommodates a polybasic stretch ending in a C-terminal arginine. This site has long been a focus of drug discovery efforts for cancer therapeutics. We recently showed that interruption of the VEGF-A/NRP-1 signaling pathway ameliorates neuropathic pain and hypothesize that interference of this pathway by SARS-CoV-2 Spike protein interferes with pain signaling. Here, we report confirmed hits from a small molecule and natural product screen of nearly 0.5 million compounds targeting the VEGF-A binding site on NRP-1. We identified nine chemical series with lead- or drug-like physicochemical properties. Using ELISA, we demonstrate that six compounds disrupt VEGF-A-NRP-1 binding more effectively than EG00229, a known NRP-1 inhibitor. Secondary validation in cells revealed that all tested compounds inhibited VEGF-A triggered VEGFR2 phosphorylation. Further, two compounds displayed robust inhibition of a recombinant vesicular stomatitis virus protein that utilizes the SARS-CoV-2 Spike for entry and fusion. These compounds represent a first step in a renewed effort to develop small molecule inhibitors of the VEGF-A/NRP-1 signaling for the treatment of neuropathic pain and cancer with the added potential of inhibiting SARS-CoV-2 virus entry.
• Wu, M. H., Padilla-Rodriguez, M., Blum, I., Camenisch, A., Figliuolo da Paz, V., Ollerton, M., Muller, J., Momtaz, S., Mitchell, S. A., Kiela, P., Thorne, C., Wilson, J. M., & Cox, C. M. (2021). Proliferation in the developing intestine is regulated by the endosomal protein Endotubin. Developmental biology, 480, 50-61.
  More info

  During postnatal intestinal development, the intestinal epithelium is highly proliferative, and this proliferation is regulated by signaling in the intervillous and crypt regions. This signaling is primarily mediated by Wnt, and requires membrane trafficking. However, the mechanisms by which membrane trafficking regulates signaling during this developmental phase are largely unknown. Endotubin (EDTB, MAMDC4) is an endosomal protein that is highly expressed in the apical endocytic complex (AEC) of villus enterocytes during fetal and postnatal development, and knockout of EDTB results in defective formation of the AEC and giant lysosome. Further, knockout of EDTB in cell lines results in decreased proliferation. However, the role of EDTB in proliferation during the development of the intestine is unknown. Using Villin-CreERT2 in EDTB mice, we deleted EDTB in the intestine in the early postnatal period, or in enteroids in vitro after isolation of intervillous cells. Loss of EDTB results in decreased proliferation in the developing intestinal epithelium and decreased ability to form enteroids. EDTB is present in cells that contain the stem cell markers LGR5 and OLFM4, indicating that it is expressed in the proliferative compartment. Further, using immunoblot analysis and TCF/LEF-GFP mice as a reporter of Wnt activity, we find that knockout of EDTB results in decreased Wnt signaling. Our results show that EDTB is essential for normal proliferation during the early stages of intestinal development and suggest that this effect is through modulation of Wnt signaling.
• Cabel, C. R., Alizadeh, E., Robbins, D. J., Ahmed, Y., Lee, E., & Thorne, C. A. (2019). Single-Cell Analyses Confirm the Critical Role of LRP6 for Wnt Signaling in APC-Deficient Cells. Developmental cell, 49(6), 827-828.
• Miyata, N., Morris, L. L., Chen, Q., Thorne, C., Singla, A., Zhu, W., Winter, M., Melton, S. D., Li, H., Sifuentes-Dominguez, L., Llano, E., Huff-Hardy, K., Starokadomskyy, P., Lopez, A., Reese, T. A., Turer, E., Billadeau, D. D., Winter, S. E., & Burstein, E. (2018). Microbial Sensing by Intestinal Myeloid Cells Controls Carcinogenesis and Epithelial Differentiation. Cell reports, 24(9), 2342-2355.
  More info

  Physiologic microbe-host interactions in the intestine require the maintenance of the microbiota in a luminal compartment through a complex interplay between epithelial and immune cells. However, the roles of mucosal myeloid cells in this process remain incompletely understood. In this study, we identified that decreased myeloid cell phagocytic activity promotes colon tumorigenesis. We show that this is due to bacterial accumulation in the lamina propria and present evidence that the underlying mechanism is bacterial induction of prostaglandin production by myeloid cells. Moreover, we show that similar events in the normal colonic mucosa lead to reductions in Tuft cells, goblet cells, and the mucus barrier of the colonic epithelium. These alterations are again linked to the induction of prostaglandin production in response to bacterial penetration of the mucosa. Altogether, our work highlights immune cell-epithelial cell interactions triggered by the microbiota that control intestinal immunity, epithelial differentiation, and carcinogenesis.
• Thorne, C. A., Chen, I. W., Sanman, L. E., Cobb, M. H., Wu, L. F., & Altschuler, S. J. (2018). Enteroid Monolayers Reveal an Autonomous WNT and BMP Circuit Controlling Intestinal Epithelial Growth and Organization. Developmental cell, 44(5), 624-633.e4.
  More info

  The intestinal epithelium maintains a remarkable balance between proliferation and differentiation despite rapid cellular turnover. A central challenge is to elucidate mechanisms required for robust control of tissue renewal. Opposing WNT and BMP signaling is essential in establishing epithelial homeostasis. However, it has been difficult to disentangle contributions from multiple sources of morphogen signals in the tissue. Here, to dissect epithelial-autonomous morphogenic signaling circuits, we developed an enteroid monolayer culture system that recapitulates four key properties of the intestinal epithelium, namely the ability to maintain proliferative and differentiated zones, self-renew, polarize, and generate major intestinal cell types. We systematically perturb intrinsic and extrinsic sources of WNT and BMP signals to reveal a core morphogenic circuit that controls proliferation, tissue organization, and cell fate. Our work demonstrates the ability of intestinal epithelium, even in the absence of 3D tissue architecture, to control its own growth and organization through morphogen-mediated feedback.
• Coate, K. C., Hernandez, G., Thorne, C. A., Sun, S., Le, T. D., Vale, K., Kliewer, S. A., & Mangelsdorf, D. J. (2017). FGF21 Is an Exocrine Pancreas Secretagogue. Cell metabolism, 25(2), 472-480.
  More info

  The metabolic stress hormone FGF21 is highly expressed in exocrine pancreas, where its levels are increased by refeeding and chemically induced pancreatitis. However, its function in the exocrine pancreas remains unknown. Here, we show that FGF21 stimulates digestive enzyme secretion from pancreatic acinar cells through an autocrine/paracrine mechanism that requires signaling through a tyrosine kinase receptor complex composed of an FGF receptor and β-Klotho. Mice lacking FGF21 accumulate zymogen granules and are susceptible to pancreatic ER stress, an effect that is reversed by administration of recombinant FGF21. Mice carrying an acinar cell-specific deletion of β-Klotho also accumulate zymogen granules but are refractory to FGF21-stimulated secretion. Like the classical post-prandial secretagogue, cholecystokinin (CCK), FGF21 triggers intracellular calcium release via PLC-IP3R signaling. However, unlike CCK, FGF21 does not induce protein synthesis, thereby preventing protein accumulation. Thus, pancreatic FGF21 is a digestive enzyme secretagogue whose physiologic function is to maintain acinar cell proteostasis.
• Coster, A. D., Thorne, C. A., Wu, L. F., & Altschuler, S. J. (2017). Examining Crosstalk among Transforming Growth Factor β, Bone Morphogenetic Protein, and Wnt Pathways. The Journal of biological chemistry, 292(1), 244-250.
  More info

  The integration of morphogenic signals by cells is not well understood. A growing body of literature suggests increasingly complex coupling among classically defined pathways. Given this apparent complexity, it is difficult to predict where, when, or even whether crosstalk occurs. Here, we investigated pairs of morphogenic pathways, previously reported to have multiple points of crosstalk, which either do not share (TGFβ and Wnt/β-catenin) or share (TGFβ and bone morphogenetic protein (BMP)) core signaling components. Crosstalk was measured by the ability of one morphogenic pathway to cross-activate core transcription factors and/or target genes of another morphogenic pathway. In contrast to previous studies, we found a surprising absence of crosstalk between TGFβ and Wnt/β-catenin. Further, we did not observe expected cross-pathway inhibition in between TGFβ and BMP, despite the fact that both use (or could compete) for the shared component SMAD4. Critical to our assays was a separation of timescales, which helped separate crosstalk due to initial signal transduction from subsequent post-transcriptional feedback events. Our study revealed fewer (and different) inter-morphogenic pathway crosstalk connections than expected; even pathways that share components can be insulated from one another.
• Li, B., Orton, D., Neitzel, L. R., Astudillo, L., Shen, C., Long, J., Chen, X., Kirkbride, K. C., Doundoulakis, T., Guerra, M. L., Zaias, J., Fei, D. L., Rodriguez-Blanco, J., Thorne, C., Wang, Z., Jin, K., Nguyen, D. M., Sands, L. R., Marchetti, F., , Abreu, M. T., et al. (2017). Differential abundance of CK1α provides selectivity for pharmacological CK1α activators to target WNT-dependent tumors. Science signaling, 10(485).
  More info

  Constitutive WNT activity drives the growth of various human tumors, including nearly all colorectal cancers (CRCs). Despite this prominence in cancer, no WNT inhibitor is currently approved for use in the clinic largely due to the small number of druggable signaling components in the WNT pathway and the substantial toxicity to normal gastrointestinal tissue. We have shown that pyrvinium, which activates casein kinase 1α (CK1α), is a potent inhibitor of WNT signaling. However, its poor bioavailability limited the ability to test this first-in-class WNT inhibitor in vivo. We characterized a novel small-molecule CK1α activator called SSTC3, which has better pharmacokinetic properties than pyrvinium, and found that it inhibited the growth of CRC xenografts in mice. SSTC3 also attenuated the growth of a patient-derived metastatic CRC xenograft, for which few therapies exist. SSTC3 exhibited minimal gastrointestinal toxicity compared to other classes of WNT inhibitors. Consistent with this observation, we showed that the abundance of the SSTC3 target, CK1α, was decreased in WNT-driven tumors relative to normal gastrointestinal tissue, and knocking down CK1α increased cellular sensitivity to SSTC3. Thus, we propose that distinct CK1α abundance provides an enhanced therapeutic index for pharmacological CK1α activators to target WNT-driven tumors.
• Wang, Z., Tacchelly-Benites, O., Yang, E., Thorne, C. A., Nojima, H., Lee, E., & Ahmed, Y. (2016). Wnt/Wingless Pathway Activation Is Promoted by a Critical Threshold of Axin Maintained by the Tumor Suppressor APC and the ADP-Ribose Polymerase Tankyrase. Genetics, 203(1), 269-81.
  More info

  Wnt/β-catenin signal transduction directs metazoan development and is deregulated in numerous human congenital disorders and cancers. In the absence of Wnt stimulation, a multiprotein "destruction complex," assembled by the scaffold protein Axin, targets the key transcriptional activator β-catenin for proteolysis. Axin is maintained at very low levels that limit destruction complex activity, a property that is currently being exploited in the development of novel therapeutics for Wnt-driven cancers. Here, we use an in vivo approach in Drosophila to determine how tightly basal Axin levels must be controlled for Wnt/Wingless pathway activation, and how Axin stability is regulated. We find that for nearly all Wingless-driven developmental processes, a three- to fourfold increase in Axin is insufficient to inhibit signaling, setting a lower-limit for the threshold level of Axin in the majority of in vivo contexts. Further, we find that both the tumor suppressor adenomatous polyposis coli (APC) and the ADP-ribose polymerase Tankyrase (Tnks) have evolutionarily conserved roles in maintaining basal Axin levels below this in vivo threshold, and we define separable domains in Axin that are important for APC- or Tnks-dependent destabilization. Together, these findings reveal that both APC and Tnks maintain basal Axin levels below a critical in vivo threshold to promote robust pathway activation following Wnt stimulation.
• Karra, A. S., Taylor, C. A., Thorne, C. A., & Cobb, M. H. (2015). A Kinase Divided. Cancer cell, 28(2), 145-7.
  More info

  In this issue of Cancer Cell, Herrero and colleagues identify an anti-tumorigenic small molecule that blocks ERK dimerization, but neither its catalytic activity nor its phosphorylation by MEK. These findings demonstrate that targeting protein dimerization could be a therapeutic avenue for inhibiting kinase signaling pathways associated with lower drug resistance.
• Thorne, C. A., Wichaidit, C., Coster, A. D., Posner, B. A., Wu, L. F., & Altschuler, S. J. (2015). GSK-3 modulates cellular responses to a broad spectrum of kinase inhibitors. Nature chemical biology, 11(1), 58-63.
  More info

  A fundamental challenge in treating disease is identifying molecular states that affect cellular responses to drugs. Here, we focus on glycogen synthase kinase 3 (GSK-3), a key regulator for many of the hallmark behaviors of cancer cells. We alter GSK-3 activity in colon epithelial cells to test its role in modulating drug response. We find that GSK-3 activity broadly affects the cellular sensitivities to a panel of oncology drugs and kinase inhibitors. Specifically, inhibition of GSK-3 activity can strongly desensitize or sensitize cells to kinase inhibitors (for example, mTOR or PLK1 inhibitors, respectively). Additionally, colorectal cancer cell lines, in which GSK-3 function is commonly suppressed, are resistant to mTOR inhibitors and yet highly sensitive to PLK1 inhibitors, and this is further exacerbated by additional GSK-3 inhibition. Finally, by conducting a kinome-wide RNAi screen, we find that GSK-3 modulates the cell proliferative phenotype of a large fraction (∼35%) of the kinome, which includes ∼50% of current, clinically relevant kinase-targeted drugs. Our results highlight an underappreciated interplay of GSK-3 with therapeutically important kinases and suggest strategies for identifying disease-specific molecular profiles that can guide optimal selection of drug treatment.
• Hao, J., Ao, A., Zhou, L., Murphy, C. K., Frist, A. Y., Keel, J. J., Thorne, C. A., Kim, K., Lee, E., & Hong, C. C. (2013). Selective small molecule targeting β-catenin function discovered by in vivo chemical genetic screen. Cell reports, 4(5), 898-904.
  More info

  The canonical Wnt signaling pathway, mediated by the transcription factor β-catenin, plays critical roles in embryonic development and represents an important therapeutic target. In a zebrafish-based in vivo screen for small molecules that specifically perturb embryonic dorsoventral patterning, we discovered a compound named windorphen that selectively blocks the Wnt signal required for ventral development. Windorphen exhibits remarkable specificity toward β-catenin-1 function, indicating that the two β-catenin isoforms found in zebrafish are not functionally redundant. We show that windorphen is a selective inhibitor of p300 histone acetyltransferase, a coactivator that associates with β-catenin. Finally, windorphen robustly and selectively kills cancer cells that harbor Wnt-activating mutations, supporting the therapeutic potential of this Wnt inhibitor class.
• Saito-Diaz, K., Chen, T. W., Wang, X., Thorne, C. A., Wallace, H. A., Page-McCaw, A., & Lee, E. (2013). The way Wnt works: components and mechanism. Growth factors (Chur, Switzerland), 31(1), 1-31.
  More info

  The canonical Wnt/β-catenin pathway is an ancient and evolutionarily conserved signaling pathway that is required for the proper development of all metazoans, from the basal demosponge Amphimedon queenslandica to humans. Misregulation of Wnt signaling is implicated in many human diseases, making this pathway an intense area of research in industry as well as academia. In this review, we explore our current understanding of the molecular steps involved in the transduction of a Wnt signal. We will focus on how the critical Wnt pathway component, β-catenin, is in a "futile cycle" of constant synthesis and degradation and how this cycle is disrupted upon pathway activation. We describe the role of the Wnt pathway in major human cancers and in the control of stem cell self-renewal in the developing organism and in adults. Finally, we describe well-accepted criteria that have been proposed as evidence for the involvement of a molecule in regulating the canonical Wnt pathway.
• Hang, B. I., Thorne, C. A., Robbins, D. J., Huppert, S. S., Lee, L. A., & Lee, E. (2012). Screening for small molecule inhibitors of embryonic pathways: sometimes you gotta crack a few eggs. Bioorganic & medicinal chemistry, 20(6), 1869-77.
  More info

  Extract prepared from Xenopus eggs represents a cell-free system that has been shown to recapitulate a multitude of cellular processes, including cell cycle regulation, DNA replication/repair, and cytoskeletal dynamics. In addition, this system has been used to successfully reconstitute the Wnt pathway. Xenopus egg extract, which can be biochemically manipulated, offers an ideal medium in which small molecule screening can be performed in near native milieu. Thus, the use of Xenopus egg extract for small molecule screening represents an ideal bridge between targeted and phenotypic screening approaches. This review focuses on the use of this system for small molecules modulators of major signal transduction pathways (Notch, Hedgehog, and Wnt) that are critical for the development of the early Xenopus embryo. We describe the properties of Xenopus egg extract and our own high throughput screen for small molecules that modulate the Wnt pathway using this cell-free system. We propose that Xenopus egg extract could similarly be adapted for screening for modulators of the Notch and Hedgehog pathways.
• Ni, T. T., Rellinger, E. J., Mukherjee, A., Xie, S., Stephens, L., Thorne, C. A., Kim, K., Hu, J., Lee, E., Marnett, L., Hatzopoulos, A. K., & Zhong, T. P. (2011). Discovering small molecules that promote cardiomyocyte generation by modulating Wnt signaling. Chemistry & biology, 18(12), 1658-68.
  More info

  We have developed a robust in vivo small-molecule screen that modulates heart size and cardiomyocyte generation in zebrafish. Three structurally related compounds (Cardionogen-1 to Cardionogen-3) identified from our screen enlarge the size of the developing heart via myocardial hyperplasia. Increased cardiomyocyte number in Cardionogen-treated embryos is due to expansion of cardiac progenitor cells. In zebrafish embryos and murine embryonic stem (ES) cells, Cardionogen treatment promotes cardiogenesis during and after gastrulation, whereas it inhibits heart formation before gastrulation. Cardionogen-induced effects can be antagonized by increasing Wnt/β-catenin signaling activity. We demonstrate that Cardionogen inhibits Wnt/β-catenin-dependent transcription in murine ES cells and zebrafish embryos. Cardionogen can rescue Wnt8-induced cardiomyocyte deficiency and heart-specific phenotypes during development. These findings demonstrate that in vivo small-molecule screens targeting heart size can reveal compounds with cardiomyogenic effects and identify underlying target pathways.
• Thorne, C. A., Lafleur, B., Lewis, M., Hanson, A. J., Jernigan, K. K., Weaver, D. C., Huppert, K. A., Chen, T. W., Wichaidit, C., Cselenyi, C. S., Tahinci, E., Meyers, K. C., Waskow, E., Orton, D., Salic, A., Lee, L. A., Robbins, D. J., Huppert, S. S., & Lee, E. (2011). A biochemical screen for identification of small-molecule regulators of the Wnt pathway using Xenopus egg extracts. Journal of biomolecular screening, 16(9), 995-1006.
  More info

  Misregulation of the Wnt pathway has been shown to be responsible for a variety of human diseases, most notably cancers. Screens for inhibitors of this pathway have been performed almost exclusively using cultured mammalian cells or with purified proteins. We have previously developed a biochemical assay using Xenopus egg extracts to recapitulate key cytoplasmic events in the Wnt pathway. Using this biochemical system, we show that a recombinant form of the Wnt coreceptor, LRP6, regulates the stability of two key components of the Wnt pathway (β-catenin and Axin) in opposing fashion. We have now fused β-catenin and Axin to firefly and Renilla luciferase, respectively, and demonstrate that the fusion proteins behave similarly as their wild-type counterparts. Using this dual luciferase readout, we adapted the Xenopus extracts system for high-throughput screening. Results from these screens demonstrate signal distribution curves that reflect the complexity of the library screened. Of several compounds identified as cytoplasmic modulators of the Wnt pathway, one was further validated as a bona fide inhibitor of the Wnt pathway in cultured mammalian cells and Xenopus embryos. We show that other embryonic pathways may be amendable to screening for inhibitors/modulators in Xenopus egg extracts.
• Alfaro, M. P., Vincent, A., Saraswati, S., Thorne, C. A., Hong, C. C., Lee, E., & Young, P. P. (2010). sFRP2 suppression of bone morphogenic protein (BMP) and Wnt signaling mediates mesenchymal stem cell (MSC) self-renewal promoting engraftment and myocardial repair. The Journal of biological chemistry, 285(46), 35645-53.
  More info

  Transplantation of mesenchymal stem cells (MSCs) is a promising therapy for ischemic injury; however, inadequate survival of implanted cells in host tissue is a substantial impediment in the progress of cellular therapy. Secreted Frizzled-related protein 2 (sFRP2) has recently been highlighted as a key mediator of MSC-driven myocardial and wound repair. Notably, sFRP2 mediates significant enhancement of MSC engraftment in vivo. We hypothesized that sFRP2 improves MSC engraftment by modulating self-renewal through increasing stem cell survival and by inhibiting differentiation. In previous studies we demonstrated that sFRP2-expressing MSCs exhibited an increased proliferation rate. In the current study, we show that sFRP2 also decreased MSC apoptosis and inhibited both osteogenic and chondrogenic lineage commitment. sFRP2 activity occurred through the inhibition of both Wnt and bone morphogenic protein (BMP) signaling pathways. sFRP2-mediated inhibition of BMP signaling, as assessed by levels of pSMAD 1/5/8, was independent of its effects on the Wnt pathway. We further hypothesized that sFRP2 inhibition of MSC lineage commitment may reduce heterotopic osteogenic differentiation within the injured myocardium, a reported adverse side effect. Indeed, we found that sFRP2-MSC-treated hearts and wound tissue had less ectopic calcification. This work provides important new insight into the mechanisms by which sFRP2 increases MSC self-renewal leading to superior tissue engraftment and enhanced wound healing.
• Jernigan, K. K., Cselenyi, C. S., Thorne, C. A., Hanson, A. J., Tahinci, E., Hajicek, N., Oldham, W. M., Lee, L. A., Hamm, H. E., Hepler, J. R., Kozasa, T., Linder, M. E., & Lee, E. (2010). Gbetagamma activates GSK3 to promote LRP6-mediated beta-catenin transcriptional activity. Science signaling, 3(121), ra37.
  More info

  Evidence from Drosophila and cultured cell studies supports a role for heterotrimeric guanosine triphosphate-binding proteins (G proteins) in Wnt signaling. Wnt inhibits the degradation of the transcriptional regulator beta-catenin. We screened the alpha and betagamma subunits of major families of G proteins in a Xenopus egg extract system that reconstitutes beta-catenin degradation. We found that Galpha(o), Galpha(q), Galpha(i2), and Gbetagamma inhibited beta-catenin degradation. Gbeta(1)gamma(2) promoted the phosphorylation and activation of the Wnt co-receptor low-density lipoprotein receptor-related protein 6 (LRP6) by recruiting glycogen synthase kinase 3 (GSK3) to the membrane and enhancing its kinase activity. In both a reporter gene assay and an in vivo assay, c-betaARK (C-terminal domain of beta-adrenergic receptor kinase), an inhibitor of Gbetagamma, blocked LRP6 activity. Several components of the Wnt-beta-catenin pathway formed a complex: Gbeta(1)gamma(2), LRP6, GSK3, axin, and dishevelled. We propose that free Gbetagamma and Galpha subunits, released from activated G proteins, act cooperatively to inhibit beta-catenin degradation and activate beta-catenin-mediated transcription.
• Saraswati, S., Alfaro, M. P., Thorne, C. A., Atkinson, J., Lee, E., & Young, P. P. (2010). Pyrvinium, a potent small molecule Wnt inhibitor, promotes wound repair and post-MI cardiac remodeling. PloS one, 5(11), e15521.
  More info

  Wnt signaling plays an important role in developmental and stem cell biology. To test the hypothesis that temporary inhibition of Wnt signaling will enhance granulation tissue and promote angiogenesis in tissue repair, we employed a recently characterized small molecule Wnt inhibitor. Pyrvinium is an FDA-approved drug that we identified as a Wnt inhibitor in a chemical screen for small molecules that stabilize β-catenin and inhibit Axin degradation. Our subsequent characterization of pyrvinium has revealed that its critical cellular target in the Wnt pathway is Casein Kinase 1α. Daily administration of pyrvinium directly into polyvinyl alcohol (PVA) sponges implanted subcutaneously in mice generated better organized and vascularized granulation tissue; this compound also increased the proliferative index of the tissue within the sponges. To evaluate its effect in myocardial repair, we induced a myocardial infarction (MI) by coronary artery ligation and administered a single intramyocardial dose of pyrvinium. Mice were evaluated by echocardiography at 7 and 30 days post-MI and treatment; post mortem hearts were evaluated by histology at 30 days. Pyrvinium reduced adverse cardiac remodeling demonstrated by decreased left ventricular internal diameter in diastole (LVIDD) as compared to a control compound. Increased Ki-67+ cells were observed in peri-infarct and distal myocardium of pyrvinium-treated animals. These results need to be further followed-up to determine if therapeutic inhibition of canonical Wnt may avert adverse remodeling after ischemic injury and its impact on myocardial repair and regeneration.
• Thorne, C. A., Hanson, A. J., Schneider, J., Tahinci, E., Orton, D., Cselenyi, C. S., Jernigan, K. K., Meyers, K. C., Hang, B. I., Waterson, A. G., Kim, K., Melancon, B., Ghidu, V. P., Sulikowski, G. A., LaFleur, B., Salic, A., Lee, L. A., Miller, D. M., & Lee, E. (2010). Small-molecule inhibition of Wnt signaling through activation of casein kinase 1α. Nature chemical biology, 6(11), 829-36.
  More info

  Wnt/β-catenin signaling is critically involved in metazoan development, stem cell maintenance and human disease. Using Xenopus laevis egg extract to screen for compounds that both stabilize Axin and promote β-catenin turnover, we identified an FDA-approved drug, pyrvinium, as a potent inhibitor of Wnt signaling (EC(50) of ∼10 nM). We show pyrvinium binds all casein kinase 1 (CK1) family members in vitro at low nanomolar concentrations and pyrvinium selectively potentiates casein kinase 1α (CK1α) kinase activity. CK1α knockdown abrogates the effects of pyrvinium on the Wnt pathway. In addition to its effects on Axin and β-catenin levels, pyrvinium promotes degradation of Pygopus, a Wnt transcriptional component. Pyrvinium treatment of colon cancer cells with mutation of the gene for adenomatous polyposis coli (APC) or β-catenin inhibits both Wnt signaling and proliferation. Our findings reveal allosteric activation of CK1α as an effective mechanism to inhibit Wnt signaling and highlight a new strategy for targeted therapeutics directed against the Wnt pathway.
• Cselenyi, C. S., Jernigan, K. K., Tahinci, E., Thorne, C. A., Lee, L. A., & Lee, E. (2008). LRP6 transduces a canonical Wnt signal independently of Axin degradation by inhibiting GSK3's phosphorylation of beta-catenin. Proceedings of the National Academy of Sciences of the United States of America, 105(23), 8032-7.
  More info

  Wnt/beta-catenin signaling controls various cell fates in metazoan development and is misregulated in several cancers and developmental disorders. Binding of a Wnt ligand to its transmembrane coreceptors inhibits phosphorylation and degradation of the transcriptional coactivator beta-catenin, which then translocates to the nucleus to regulate target gene expression. To understand how Wnt signaling prevents beta-catenin degradation, we focused on the Wnt coreceptor low-density lipoprotein receptor-related protein 6 (LRP6), which is required for signal transduction and is sufficient to activate Wnt signaling when overexpressed. LRP6 has been proposed to stabilize beta-catenin by stimulating degradation of Axin, a scaffold protein required for beta-catenin degradation. In certain systems, however, Wnt-mediated Axin turnover is not detected until after beta-catenin has been stabilized. Thus, LRP6 may also signal through a mechanism distinct from Axin degradation. To establish a biochemically tractable system to test this hypothesis, we expressed and purified the LRP6 intracellular domain from bacteria and show that it promotes beta-catenin stabilization and Axin degradation in Xenopus egg extract. Using an Axin mutant that does not degrade in response to LRP6, we demonstrate that LRP6 can stabilize beta-catenin in the absence of Axin turnover. Through experiments in egg extract and reconstitution with purified proteins, we identify a mechanism whereby LRP6 stabilizes beta-catenin independently of Axin degradation by directly inhibiting GSK3's phosphorylation of beta-catenin.
• Tahinci, E., Thorne, C. A., Franklin, J. L., Salic, A., Christian, K. M., Lee, L. A., Coffey, R. J., & Lee, E. (2007). Lrp6 is required for convergent extension during Xenopus gastrulation. Development (Cambridge, England), 134(22), 4095-106.
  More info

  Wnt signaling regulates beta-catenin-mediated gene transcription and planar cell polarity (PCP). The Wnt co-receptor, Lrp6, is required for signaling along the beta-catenin arm. We show that Lrp6 downregulation (by morpholino injection) or overexpression in Xenopus embryos disrupts convergent extension, a hallmark feature of Wnt/PCP components. In embryos with decreased Lrp6 levels, cells of the dorsal marginal zone (DMZ), which undergoes extensive cellular rearrangements during gastrulation, exhibit decreased length:width ratios, decreased migration, and increased numbers of transient cytoplasmic protrusions. We show that Lrp6 opposes Wnt11 activity and localizes to the posterior edge of migrating DMZ cells and that Lrp6 downregulation enhances cortical and nuclear localization of Dsh and phospho-JNK, respectively. Taken together, these data suggest that Lrp6 inhibits Wnt/PCP signaling. Finally, we identify the region of the Lrp6 protein with Wnt/PCP activity to a stretch of 36 amino acids, distinct from regions required for Wnt/beta-catenin signaling. We propose a model in which Lrp6 plays a critical role in the switch from Wnt/PCP to Wnt/beta-catenin signaling.
• Thorne, C., & Lee, A. V. (2003). Cross talk between estrogen receptor and IGF signaling in normal mammary gland development and breast cancer. Breast disease, 17, 105-14.
  More info

  Both estrogen and insulin-like growth factor-1 (IGF-I) are critical for normal mammary gland development, but are also implicated in breast cancer development and progression. Evidence that the signaling pathways utilized by these hormones interact has been shown in normal and tumorigenic cell lines, xenograft models, and breast cancer tissue. Analysis of the mechanism of interaction between estrogen and IGF-I has revealed multiple levels of cross-talk with bi-directional regulation of both pathways. Importantly, this bi-directional regulation is often in a positive manner and the resulting synergism noted between these two potent mitogens may be a critical element in the progression of breast cancer. While targeting of the estrogen receptor has shown success in the prevention and treatment of breast cancer, it is hoped that targeting of the IGF signaling pathway will yield similar beneficial results and that inhibitors of IGF signaling may be particularly useful in combination with current antiestrogen therapies. This review will focus on the evidence indicating cross-talk between estrogen and IGF-I and reveal some of the complex mechanisms that link these important pathways in breast cancer.