Kang Yell Choi

The Dishevelled-binding protein CXXC5 negatively regulates cutaneous wound healing

In human melanoma biopsies and a murine cutaneous wound model, Lee et al. identify the Dishevelled-binding protein CXXC5 as a negative modulator of skin wound healing. CXXC5-deficient mice present accelerated wound healing as well as keratin and collagen synthesis. CXXC5, interacting with Dvl, operates as a negative feedback regulator of Wnt/β-catenin signaling and may represent a potential target for wound treatment.

CXXC5 is a transcriptional activator of Flk-1 and mediates bone morphogenic protein-induced endothelial cell differentiation and vessel formation

CXXC5 is a member of a small subset of proteins containing CXXC‐type zinc‐finger domain. Here, we show that CXXC5 is a transcription factor activating Flk‐1, a receptor for vascular endothelial growth factor. CXXC5 and Flk‐1 were accmulated in nucli and membrane of mouse embryonic stem cells (mESCs), respectively, during their endothelial differentiation. CXXC5 overexpression induced Flk‐1 transcription in both endothelium‐differentiated mESCs and human umbilical vein endothelial cells (HUVECs). In vitro DNA binding assay showed direct interaction of CXXC5 on the Flk‐1 promoter region, and mutation on its DNA‐binding motif abolished transcriptional activity. We showed that bone morphorgeneic protein 4 (BMP4) induced CXXC5 transcription in the cells, and inhibitors of BMP signaling suppressed the CXXC5 induction and the consequent Flk‐1 induction by BMP4 treatment. CXXC5 knockdown resulted in suppression of BMP4‐induced stress fiber formation (56.8±1.3% decrease, P<0.05) and migration (54.6±1.9% decrease, P<0.05) in HUVECs. The in vivo roles of CXXC5 in BMP‐signaling‐specific vascular development and angiogenesis were shown by specific defect of caudal vein plex vessel formation (57.9±11.8% decrease, P<0.05) in cxxc5 morpholino‐injected zebrafish embryos and by supression of BMP4‐induced angigogensis in subcutaneously injected Matrigel plugs in CXXC5‐/‐ mice. Overall, CXXC5 is a transcriptional activator for Flk‐1, mediating BMP signaling for differentiation and migration of endothelial cell and vessel formation.—Kim, H.‐Y., Yang, D.‐H., Shin, S.‐W., Kim, M.‐Y., Yoon, J.‐H., Kim, S., Park, H.‐C., Kang, D. W., Min, D., Hur, M.‐W., Choi, K‐Y. CXXC5 is a transcriptional activator of Flk‐1 and mediates bone morphogenic protein‐induced endothelial cell differentiation and vessel formation. FASEB J. 28, 615–626 (2014). www.fasebj.org

Hovenia dulcis Thunb Extract and Its Ingredient Methyl Vanillate Activate Wnt/β-Catenin Pathway and Increase Bone Mass in Growing or Ovariectomized Mice

The Wnt/β-catenin pathway is a potential target for development of anabolic agents to treat osteoporosis because of its role in osteoblast differentiation and bone formation. However, there is no clinically available anti-osteoporosis drug that targets this Wnt/β-catenin pathway. In this study, we screened a library of aqueous extracts of 350 plants and identified Hovenia dulcis Thunb (HDT) extract as a Wnt/β-catenin pathway activator. HDT extract induced osteogenic differentiation of calvarial osteoblasts without cytotoxicity. In addition, HDT extract increased femoral bone mass without inducing significant weight changes in normal mice. In addition, thickness and area of femoral cortical bone were also significantly increased by the HDT extract. Methyl vanillate (MV), one of the ingredients in HDT, also activated the Wnt/β-catenin pathway and induced osteoblast differentiation in vitro. MV rescued trabecular or cortical femoral bone loss in the ovariectomized mice without inducing any significant weight changes or abnormality in liver tissue when administrated orally. Thus, natural HDT extract and its ingredient MV are potential anabolic agents for treating osteoporosis.

Sur8/Shoc2 promotes cell motility and metastasis through activation of Ras-PI3K signaling

Sur8 (also known as Shoc2) is a Ras-Raf scaffold protein that modulates signaling through extracellular signal-regulated kinase (ERK) pathway. Although Sur8 has been shown to be a scaffold protein of the Ras-ERK pathway, its interaction with other signaling pathways and its involvement in tumor malignancy has not been reported. We identified that Sur8 interacts with the p110α subunit of phosphatidylinositol 3-kinase (PI3K), as well as with Ras and Raf, and these interactions are increased in an epidermal growth factor (EGF)- and oncogenic Ras-dependent manner. Sur8 regulates cell migration and invasion via activation of Rac and matrix metalloproteinases (MMPs). Interestingly, using inhibitors of MEK and PI3K we found Sur8 mediates these cellular behaviors predominantly through PI3K pathway. We further found that human metastatic melanoma tissues had higher Sur8 content followed by activations of Akt, ERK, and Rac. Lentivirus-mediated Sur8-knockdown attenuated metastatic potential of highly invasive B16-F10 melanoma cells indicating the role of Sur8 in melanoma metastasis. This is the first report to identify the role of scaffold protein Sur8 in regulating cell motility, invasion, and metastasis through activation of both ERK and PI3K pathways.

House dust mite allergen der f 2 induces interleukin-13 expression by activating the PI3K/Akt pathway

House dust mites (HDMs) are a common cause of allergic asthma. The group 2 allergen from Dermatophagoides farinae, Der f 2, is one of the major HDM allergens. Elevated Der f 2 immunoglobulin E (IgE) levels are observed in most of the allergic patients. Interleukin-13 (IL-13), a gene associated with asthma pathology, was induced by Der f 2 in BEAS-2B human airway epithelial cells; however, the signaling pathways associated with Der f 2 are not fully understood. In this study, we identified a role of the phosphatidylinositol-3-kinase (PI3K)/Akt pathway, a well-known potential target for anti-asthma drugs, in the IL-13 induction by Der f 2. First, Der f 2 activated the PI3K/Akt pathway, which subsequently activated the nuclear factor-kappa B (NF-κB) pathway and induced IL-13 expression in BEAS-2B cells. Treatment with the PI3K inhibitor LY294002 abolished Der f 2-induced activation of Akt and NF-κB and the expression of IL-13. Furthermore, Der f 2-induced activation of the PI3K/Akt and NF-κB pathways, expression of IL-13, and the blockade of these effects with a PI3K inhibitor were confirmed in the lungs of mice that were intranasally exposed to Der f 2. Taken together, these results indicate that the PI3K/Akt pathway regulates Der f 2-induced IL-13 expression via activation of the NF-κB pathway.

Phospholipase D inhibitor enhances radiosensitivity of breast cancer cells

Radiation and drug resistance remain the major challenges and causes of mortality in the treatment of locally advanced, recurrent and metastatic breast cancer. Dysregulation of phospholipase D (PLD) has been found in several human cancers and is associated with resistance to anticancer drugs. In the present study, we evaluated the effects of PLD inhibition on cell survival, cell death and DNA damage after exposure to ionizing radiation (IR). Combined IR treatment and PLD inhibition led to an increase in the radiation-induced apoptosis of MDA-MB-231 metastatic breast cancer cells. The selective inhibition of PLD1 and PLD2 led to a significant decrease in the IR-induced colony formation of breast cancer cells. Moreover, PLD inhibition suppressed the radiation-induced activation of extracellular signal-regulated kinase and enhanced the radiation-stimulated phosphorylation of the mitogen-activated protein kinases p38 and c-Jun N-terminal kinase. Furthermore, PLD inhibition, in combination with radiation, was very effective at inducing DNA damage, when compared with radiation alone. Taken together, these results suggest that PLD may be a useful target molecule for the enhancement of the radiotherapy effect.

Small-molecule binding of the axin RGS domain promotes β-catenin and Ras degradation.

Both the Wnt/β-catenin and Ras pathways are aberrantly activated in most human colorectal cancers (CRCs) and interact cooperatively in tumor promotion. Inhibition of these signaling may therefore be an ideal strategy for treating CRC. We identified KY1220, a compound that destabilizes both β-catenin and Ras, via targeting the Wnt/β-catenin pathway, and synthesized its derivative KYA1797K. KYA1797K bound directly to the regulators of G-protein signaling domain of axin, initiating β-catenin and Ras degradation through enhancement of the β-catenin destruction complex activating GSK3β. KYA1797K effectively suppressed the growth of CRCs harboring APC and KRAS mutations, as shown by various in vitro studies and by in vivo studies using xenograft and transgenic mouse models of tumors induced by APC and KRAS mutations. Destabilization of both β-catenin and Ras via targeting axin is a potential therapeutic strategy for treatment of CRC and other type cancers activated Wnt/β-catenin and Ras pathways.

Small molecule inhibitors of the Dishevelled‐CXXC5 interaction are new drug candidates for bone anabolic osteoporosis therapy

Bone anabolic agents promoting bone formation and rebuilding damaged bones would ideally overcome the limitations of anti‐resorptive therapy, the current standard prescription for osteoporosis. However, the currently prescribed parathyroid hormone (PTH)‐based anabolic drugs present limitations and adverse effects including osteosarcoma during long‐term use. Also, the antibody‐based anabolic drugs that are currently being developed present the potential limits in clinical application typical of macromolecule drugs. We previously identified that CXXC5 is a negative feedback regulator of the Wnt/β‐catenin pathway via its interaction with Dishevelled (Dvl) and suggested the Dvl–CXXC5 interaction as a potential target for anabolic therapy of osteoporosis. Here, we screened small‐molecule inhibitors of the Dvl–CXXC5 interaction via a newly established in vitro assay system. The screened compounds were found to activate the Wnt/β‐catenin pathway and enhance osteoblast differentiation in primary osteoblasts. The bone anabolic effects of the compounds were shown using ex vivo‐cultured calvaria. Nuclear magnetic resonance (NMR) titration analysis confirmed interaction between Dvl PDZ domain and KY‐02061, a representative of the screened compounds. Oral administration of KY‐02327, one of 55 newly synthesized KY‐02061 analogs, successfully rescued bone loss in the ovariectomized (OVX) mouse model. In conclusion, small‐molecule inhibitors of the Dvl–CXXC5 interaction that block negative feedback regulation of Wnt/β‐catenin signaling are potential candidates for the development of bone anabolic anti‐osteoporosis drugs.

Targeting of CXXC5 by a Competing Peptide Stimulates Hair Regrowth and Wound-Induced Hair Neogenesis

The Wnt/β-catenin pathway has been implicated in hair follicle development and hair regeneration in adults. We discovered that CXXC-type zinc finger protein 5 (CXXC5) is a negative regulator of the Wnt/β-catenin pathway involved in hair regrowth and wound-induced hair follicle neogenesis via an interaction with Dishevelled. CXXC5 was upregulated in miniaturized hair follicles and arrector pili muscles in human balding scalps. The inhibitory effects of CXXC5 on alkaline phosphatase activity and cell proliferation were demonstrated using human hair follicle dermal papilla cells. Moreover, CXXC5-/- mice displayed accelerated hair regrowth, and treatment with valproic acid, a glycogen synthase kinase 3β inhibitor that activates the Wnt/β-catenin pathway, further induced hair regrowth in the CXXC5-/- mice. Disrupting the CXXC5-Dishevelled interaction with a competitor peptide activated the Wnt/β-catenin pathway and accelerated hair regrowth and wound-induced hair follicle neogenesis. Overall, these findings suggest that the CXXC5-Dishevelled interaction is a potential target for the treatment of hair loss.

KY1022, a small molecule destabilizing Ras via targeting the Wnt/β-catenin pathway, inhibits development of metastatic colorectal cancer

APC (80-90%) and K-Ras (40-50%) mutations frequently occur in human colorectal cancer (CRC) and these mutations cooperatively accelerate tumorigenesis including metastasis. In addition, both β-catenin and Ras levels are highly increased in CRC, especially in metastatic CRC (mCRC). Therefore, targeting both the Wnt/β-catenin and Ras pathways could be an ideal therapeutic approach for treating mCRC patients. In this study, we characterized the roles of KY1022, a small molecule that destabilizes both β-catenin and Ras via targeting the Wnt/β-catenin pathway, in inhibiting the cellular events, including EMT, an initial process of metastasis, and apoptosis. As shown by in vitro and in vivo studies using APCMin/+/K-RasG12DLA2 mice, KY1022 effectively suppressed the development of mCRC at an early stage of tumorigenesis. A small molecular approach degrading both β-catenin and Ras via inhibition of the Wnt/β-catenin signaling would be an ideal strategy for treatment of mCRC.