Jia-Ling Teo

A small molecule inhibitor of beta-catenin/CREB-binding protein transcription [corrected].

Inherited and somatic mutations in the adenomatous polyposis coli occur in most colon cancers, leading to activation of beta-catenin-responsive genes. To identify small molecule antagonists of this pathway, we challenged transformed colorectal cells with a secondary structure-templated chemical library, looking for compounds that inhibit a beta-catenin-responsive reporter. We identified ICG-001, a small molecule that down-regulates beta-catenin/T cell factor signaling by specifically binding to cyclic AMP response element-binding protein. ICG-001 selectively induces apoptosis in transformed cells but not in normal colon cells, reduces in vitro growth of colon carcinoma cells, and is efficacious in the Min mouse and nude mouse xenograft models of colon cancer.

The Wnt signaling pathway in cellular proliferation and differentiation: A tale of two coactivators.

Wnt signaling pathways play divergent roles during development, normal homeostasis and disease. The responses that result from the activation of the pathway control both proliferation and differentiation. Tight regulation and controlled coordination of the Wnt signaling cascade is required to maintain the balance between proliferation and differentiation. The non-redundant roles of the coactivator proteins CBP and p300, within the context of Wnt signaling are discussed. We highlight their roles as integrators of the various inputs that a cell receives to elicit the correct and coordinated response. We propose that essentially all cellular information - i.e. from other signaling pathways, nutrient levels, etc. - is funneled down into a choice of coactivators usage, either CBP or p300, by their interacting partner beta-catenin (or catenin-like molecules in the absence of beta-catenin) to make the critical decision to either remain quiescent, or once entering cycle to proliferate without differentiation or to initiate the differentiation process.

A small molecule inhibitor of β-catenin/cyclic AMP response element-binding protein transcription

Inherited and somatic mutations in the adenomatous polyposis coli occur in most colon cancers, leading to activation of beta-catenin-responsive genes. To identify small molecule antagonists of this pathway, we challenged transformed colorectal cells with a secondary structure-templated chemical library, looking for compounds that inhibit a beta-catenin-responsive reporter. We identified ICG-001, a small molecule that down-regulates beta-catenin/T cell factor signaling by specifically binding to cyclic AMP response element-binding protein. ICG-001 selectively induces apoptosis in transformed cells but not in normal colon cells, reduces in vitro growth of colon carcinoma cells, and is efficacious in the Min mouse and nude mouse xenograft models of colon cancer.

Wnt Signaling Orchestration with a Small Molecule DYRK Inhibitor Provides Long-Term Xeno-Free Human Pluripotent Cell Expansion

An optimal culture system for human pluripotent stem cells should be fully defined and free of animal components. To date, most xeno‐free culture systems require human feeder cells and/or highly complicated culture media that contain activators of the fibroblast growth factor (FGF) and transforming growth factor‐β (TGFβ) signaling pathways, and none provide for replacement of FGF/TGFβ ligands with chemical compounds. The Wnt/β‐catenin signaling pathway plays an important role in mouse embryonic stem cells in leukemia inhibitory factor‐independent culture; however, the role of Wnt/β‐catenin signaling in human pluripotent stem cell is still poorly understood and controversial because of the dual role of Wnts in proliferation and differentiation. Building on our previous investigations of small molecules modulating Wnt/β‐catenin signaling in mouse embryonic stem cells, we identified a compound, ID‐8, that could support Wnt‐induced human embryonic stem cell proliferation and survival without differentiation. Dual‐specificity tyrosine phosphorylation‐regulated kinase (DYRK) is the target of the small molecule ID‐8. Its role in human pluripotent cell renewal was confirmed by DYRK knockdown in human embryonic stem cells. Using Wnt and the DYRK inhibitor ID‐8, we have developed a novel and simple chemically defined xeno‐free culture system that allows for long‐term expansion of human pluripotent stem cells without FGF or TGFβ activation. These culture conditions do not include xenobiotic supplements, serum, serum replacement, or albumin. Using this culture system, we have shown that several human pluripotent cell lines maintained pluripotency (>20 passages) and a normal karyotype and still retained the ability to differentiate into derivatives of all three germ layers. This Wnt‐dependent culture system should provide a platform for complete replacement of growth factors with chemical compounds.

Pharmacogenetic profiling of CD133 is associated with response rate (RR) and progression-free survival (PFS) in patients with metastatic colorectal cancer (mCRC), treated with bevacizumab-based chemotherapy.

Recent studies suggest CD133, a surface protein widely used for isolation of colon cancer stem cells, to be associated with tumor angiogenesis and recurrence. We hypothesized that gene expression levels and germline variations in CD133 will predict clinical outcome in patients with metastatic colorectal cancer (mCRC), treated in first-line setting with 5-fluorouracil, oxaliplatin and bevacizumab (BV), and we investigated whether there is a correlation with gene expression levels of CD133, vascular endothelial growth factor (VEGF) and its receptors. We evaluated intra-tumoral gene expression levels by quantitative real-time (RT) PCR from 54 patients and three germline variants of the CD133 gene by PCR-restriction-fragment length polymorphism from 91 patients with genomic DNA. High gene expression levels of CD133 (>7.76) conferred a significantly greater tumor response (RR=86%) than patients with low expression levels (⩽7.76, RR=38%, adjusted P=0.003), independent of VEGF or its receptor gene expression levels. Gene expression levels of CD133 were significantly associated with VEGF and its receptors messenger RNA levels (VEGFR-1 (P<0.01), -2 and -3, P<0.05). Combined analyses of two polymorphisms showed a significant association with progression-free survival (PFS) (18.5 months vs 9.8 months, P=0.004) in a multivariate analysis as an independent prognostic factor for PFS (adjusted P=0.002). These results suggest that CD133 is a predictive marker for standard first-line BV-based treatment in mCRC.

A small molecule inhibitor of -catenin/CREB-binding protein transcription

Inherited and somatic mutations in the adenomatous polyposis coli occur in most colon cancers, leading to activation of beta-catenin-responsive genes. To identify small molecule antagonists of this pathway, we challenged transformed colorectal cells with a secondary structure-templated chemical library, looking for compounds that inhibit a beta-catenin-responsive reporter. We identified ICG-001, a small molecule that down-regulates beta-catenin/T cell factor signaling by specifically binding to cyclic AMP response element-binding protein. ICG-001 selectively induces apoptosis in transformed cells but not in normal colon cells, reduces in vitro growth of colon carcinoma cells, and is efficacious in the Min mouse and nude mouse xenograft models of colon cancer.

CBP/catenin antagonist safely eliminates drug-resistant leukemia-initiating cells

CREB-binding protein (CBP) and p300 are highly homologous transcriptional coactivators with unique, non-redundant roles that bind a wide array of proteins, including catenins—β and γ. ICG-001 is a small-molecule inhibitor that specifically inhibits the CBP/catenin interaction. Importantly, ICG-001 does not inhibit the p300/catenin interaction. We demonstrate that specifically inhibiting the interaction between CBP and catenin with ICG-001 results in the differentiation of quiescent drug-resistant chronic myelogenous leukemia-initiating cells (CML LICs), thereby sensitizing them to BCR-ABL tyrosine kinase inhibitors, for example, Imatinib. Using ICG-001 in a NOD/SCID/IL2Rγ−/− mouse model of engrafted human chronic myelogenous leukemia, we now demonstrate the complete elimination of engrafted leukemia after only one course of combined chemotherapy. Combination-treated animals live as long as their non-engrafted littermates. Results from these studies demonstrate that specifically antagonizing the CBP/catenin interaction with ICG-001 can eliminate drug-resistant CML LICs without deleterious effects to the normal endogenous hematopoietic stem cell population.

Wnt Signaling in Stem Cells

Wnt signaling pathways play divergent roles during development, normal homeostasis and disease. Wnt signaling is also critically important in stem cell biology. It has been demonstrated to be involved in both the proliferation and differentiation of stem and progenitor populations. Wnt/β-catenin signaling also plays a critical role in lineage decision/commitment. These dramatically different outcomes upon activation of the Wnt signaling cascade has fueled enormous controversy concerning the role of Wnt signaling in maintenance of potency and induction of differentiation. Tight regulation and controlled coordination of the Wnt signaling cascade is required to maintain the balance between proliferation and differentiation. The diverse and titrated responses that result from the activation of the Wnt signaling pathway however begs the question of how the Wnt signaling network integrates the various inputs that a cell receives to elicit the correct and coordinated responses.

Differentiation Therapy Targeting the β-Catenin/CBP Interaction in Pancreatic Cancer

Background: Although canonical Wnt signaling is known to promote tumorigenesis in pancreatic ductal adenocarcinoma (PDAC), a cancer driven principally by mutant K-Ras, the detailed molecular mechanisms by which the Wnt effector β-catenin regulates such tumorigenesis are largely unknown. We have previously demonstrated that β-catenin’s differential usage of the Kat3 transcriptional coactivator cyclic AMP-response element binding protein-binding protein (CBP) over its highly homologous coactivator p300 increases self-renewal and suppresses differentiation in other types of cancer. Aim/methods: To investigate Wnt-mediated carcinogenesis in PDAC, we have used the specific small molecule CBP/β-catenin antagonist, ICG-001, which our lab identified and has extensively characterized, to examine its effects in human pancreatic cancer cells and in both an orthotopic mouse model and a human patient-derived xenograft (PDX) model of PDAC. Results/conclusion: We report for the first time that K-Ras activation increases the CBP/β-catenin interaction in pancreatic cancer; and that ICG-001 specific antagonism of the CBP/β-catenin interaction sensitizes pancreatic cancer cells and tumors to gemcitabine treatment. These effects were associated with increases in the expression of let-7a microRNA; suppression of K-Ras and survivin; and the elimination of drug-resistant cancer stem/tumor-initiating cells.

Abstract 5772: Antagonizing the CREB binding protein (CBP)/beta-catenin interaction sensitizes pancreatic cancer cells to chemotherapy

Proceedings: AACR 101st Annual Meeting 2010‐‐ Apr 17‐21, 2010; Washington, DC Wnt/beta-catenin signaling plays an important role in the regulation of cell proliferation and differentiation, maintenance of stem cell pluripotency and cancer development. Using specific small molecular inhibitors, we have previously demonstrated that the critical mechanism differentiating between cell proliferation and cell differentiation is the switch of beta-catenin binding to the coactivator CBP or p300 respectively. In colorectal cancer, and hematologic malignancies with overt wnt/beta-catenin signaling activity, the small molecular inhibitor of CBP/beta-catenin enhances sensitivity to chemotherapy and tumor growth control. Although pancreatic cancers do not generally carry mutations in Wnt signaling regulators (e.g. APC, beta-catenin), recent studies indicate that Wnt/beta-catenin signaling promotes tumorigenesis in pancreatic cancer as well. Since pancreatic cancer is one of the most intrinsically resistant cancers to chemotherapy, the purpose of this study was to explore the effect of the small molecular CBP/beta-catenin inhibitor alone and in combination with standard chemotherapy in pancreatic cancer cell lines in vitro and in vivo. The combination of the small molecular inhibitor of CBP/beta-catenin with Gemcitabine or Erlotinib significantly inhibited cell proliferation of Panc-1, BxPC-3 and AsPC-1 pancreatic cancer cells in vitro. Anti-proliferative effects were seen with the combination of a small molecular CBP/beta-catenin antagonist and Gemcitabine concentrations as low as 1nM. qRT-PCR revealed a significant down regulation of the Wnt target genes Survivin and S100A4 which have been shown previously to be of prognostic relevance in pancreatic cancer patients. AsPC-1-Luc pancreatic cancer cells with stable transfected luciferase activity were implanted orthotopically into the pancreas of Nu/Nu mice and mice were randomized to either treatment with single agent small molecular CBP/beta-catenin inhibitor, Gemicitabine, Erlotinib or the combination of small molecular inhibitor and Gemcitabine or Erlotinib. Tumor engraftment and tumor growth were monitored once per week using the bioluminescence imaging system IVIS200. The data of the ongoing orthotopic tumor xenograft study show a beneficial therapeutic effect of the small molecular inhibitor in combination with chemotherapeutic and targeted agents. The results of our study indicate that the Wnt/beta-catenin pathway is an attractive therapeutic target in pancreatic cancer. In particular the inhibition of CBP/beta-catenin interaction using a small molecular inhibitor sensitizes pancreatic cancer cells to the chemotherapeutic agent Gemcitabine and EGFR-targeted therapy with Erlotinib in vitro. Ongoing in vivo experiments appear to be highly promising to confirm the in vitro results. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 5772.