CK1δ/ε inhibition induces ULK1-mediated autophagy in tumorigenesis.

INTRODUCTION: Autophagy is an important mechanism of cell homeostasis maintenance. As essential serine/threonine-protein kinases, casein kinase I family members affect tumorigenesis by regulating a variety of cellular progression. However, the mechanism by which they regulate autophagy remains unclear. MATERIALS AND METHODS: We silenced CK1δ/ε in cancer cells and observed cell morphology, the expression of autophagy-related genes, and its impact on cancer cell growth and viability. By inhibiting CK1δ/ε-induced upregulation of autophagy genes, we profiled the regulatory mechanism of CK1δ/ε on autophagy and cancer cell growth. The impact of CK1δ/ε inhibition on tumor cell growth was also assessed in vivo. RESULTS: Here, we found that CK1δ/ε played an important role in ULK1-mediated autophagy regulation in both lung cancer and melanoma cells. Mechanically, silencing CK1δ/ε increased ULK1 expression with enhanced autophagic flux and suppressed cancer cell proliferation, while ULK1 knockdown blocked the activation of autophagy caused by CK1δ/ε inhibition. By silencing CK1δ/ε in syngeneic mouse model bearing LLC1 murine lung cancer cells in vivo, we observed tumor growth suppression mediated by CK1δ/ε inhibition. CONCLUSION: Our results provide evidence for the role of CK1δ/ε in the regulation of tumorigenesis via the ULK1-mediated autophagy, and also suggest the impact of CK1δ/ε inhibition on tumor growth and its significance as a potential therapeutic target.

ISX9 loaded thermoresponsive nanoparticles for hair follicle regrowth.

There is a high demand for an optimal drug delivery system to treat androgenetic alopecia. Topical application of ISX9, which is a neurogenesis inducer, has been found to stimulate hair follicle (HF) regrowth by upregulating the Wnt/ß-catenin signaling pathway, an essential pathway involved in initiating HF growth and development. In the present study, a temperature-sensitive, biopolymer-based, biocompatible, and eco-friendly drug-delivery system was synthesized. This system comprised chitosan-grafted poly(glycidyl methacrylate-co-N-isopropyl acrylamide) (Poly(GMA-co-NIPAAm)@CS-PGNCS) as the shell component and PF127 as the core polymer. The hydrophobic nature of the PF127 block copolymer efficiently dissolved the partially water-soluble drug, ISX9, and the thermos-responsive shell polymer effectively released the drug at a definite skin temperature. The optimized spherical nanoparticles demonstrated the lowest critical solution temperature (LCST) at 32 ± 2 °C with a diameter of 100-250 nm, which delivered encapsulated ISX9 with greater precision than topical ISX9. In a series of in vivo experiments, we demonstrated that ISX9-coated TBNPs upregulated the expression of ß-catenin, active ß-catenin, Wnt target genes, stemness marker genes, proliferating cell nuclear antigen, HF stem cell markers, and HF markers including VEGF, TGF, and IGF-1 more effectively than topical ISX9. These results suggest that TBNPs could be employed as a platform for effective transdermal delivery of various hydrophobic drugs.

Isoxazole 9 (ISX9), a small molecule targeting Axin, activates Wnt/ß-catenin signalling and promotes hair regrowth.

BACKGROUND AND PURPOSE: Isoxazole 9 (ISX9) is a neurogenesis-promoting small molecule compound that can up-regulate the expression of NeuroD1 and induce differentiation of neuronal, cardiac and islet endocrine progenitors. So far, the molecular mechanisms underlying the action of ISX9 still remain elusive. EXPERIMENTAL APPROACH: To identify a novel agonist of the Wnt/ß-catenin, a cell-based SuperTOPFlash reporter system was used to screen known-compound libraries. An activation effect of ISX9 on the Wnt/ß-catenin pathway was analysed with the SuperTOPFlash or SuperFOPFlash reporter system. Effects of ISX9 on Axin1/LRP6 interaction were examined using a mammalian two-hybrid system, co-immunoprecipitation, microscale thermophoresis, emission spectra and mass spectrometry assays. The expression of Wnt target and stemmness marker genes were evaluated with real-time PCR and immunoblotting. In vivo hair regeneration abilities of ISX9 were analysed by immunohistochemical staining, real-time PCR and immunoblotting in hair regrowth model using C57BL/6J mice. KEY RESULTS: In this study, ISX9 was identified as a novel agonist of the Wnt/ß-catenin pathway. ISX9 targeted Axin1 by covalently binding to its N-terminal region and potentiated the LRP6-Axin1 interaction, thereby resulting in the stabilization of ß-catenin and up-regulation of Wnt target genes and stemmness marker genes. Moreover, the topical application of ISX9 markedly promoted hair regrowth in C57BL/6J mice and induced hair follicle transition from telogen to anagen via enhancing Wnt/ß-catenin pathway. CONCLUSIONS AND IMPLICATIONS: Taken together, our study unravelled that ISX9 could activate Wnt/ß-catenin signalling by potentiating the association between LRP6 and Axin1, and may be a promising therapeutic agent for alopecia treatment.

The CK1δ/ϵ-Tip60 Axis Enhances Wnt/ß-Catenin Signaling via Regulating ß-Catenin Acetylation in Colon Cancer.

Casein kinase 1δ/ϵ (CK1δ/ϵ) are well-established positive modulators of the Wnt/ß-catenin signaling pathway. However, the molecular mechanisms involved in the regulation of ß-catenin transcriptional activity by CK1δ/ϵ remain unclear. In this study, we found that CK1δ/ϵ could enhance ß-catenin-mediated transcription through regulating ß-catenin acetylation. CK1δ/ϵ interacted with Tip60 and facilitated the recruitment of Tip60 to ß-catenin complex, resulting in increasing ß-catenin acetylation at K49. Importantly, Tip60 significantly enhanced the SuperTopFlash reporter activity induced by CK1δ/ϵ or/and ß-catenin. Furthermore, a CK1δ/CK1ϵ/ß-catenin/Tip60 complex was detected in colon cancer cells. Simultaneous knockdown of CK1δ and CK1ϵ significantly attenuated the interaction between ß-catenin and Tip60. Notably, inhibition of CK1δ/ϵ or Tip60, with shRNA or small molecular inhibitors downregulated the level of ß-catenin acetylation at K49 in colon cancer cells. Finally, combined treatment with CK1 inhibitor SR3029 and Tip60 inhibitor MG149 had more potent inhibitory effect on ß-catenin acetylation, the transcription of Wnt target genes and the viability and proliferation in colon cancer cells. Taken together, our results revealed that the transcriptional activity of ß-catenin could be modulated by the CK1δ/ϵ-ß-catenin-Tip60 axis, which may be a potential therapeutic target for colon cancer.

Transmembrane protein 97 exhibits oncogenic properties via enhancing LRP6-mediated Wnt signaling in breast cancer.

Upregulation of transmembrane protein 97 (TMEM97) has been associated with progression and poor outcome in multiple human cancers, including breast cancer. Recent studies suggest that TMEM97 may be involved in the activation of the Wnt/ß-catenin pathway. However, the molecular mechanism of TMEM97 action on Wnt/ß-catenin signaling is completely unclear. In the current study, TMEM97 was identified as an LRP6-interacting protein. TMEM97 could interact with LRP6 intracellular domain and enhance LRP6-mediated Wnt signaling in a CK1δ/ε-dependent manner. The binding of TMEM97 to LRP6 facilitated the recruitment of CK1δ/ε to LRP6 complex, resulting in LRP6 phosphorylation at Ser 1490 and the stabilization of ß-catenin. In breast cancer cells, knockout of TMEM97 attenuated the Wnt/ß-catenin signaling cascade via regulating LRP6 phosphorylation, leading to a decrease in the expression of Wnt target genes AXIN2, LEF1, and survivin. TMEM97 deficiency also suppressed cell viability, proliferation, colony formation, migration, invasion, and stemness properties in breast cancer cells. Importantly, TMEM97 knockout suppressed tumor growth through downregulating the Wnt/ß-catenin signaling pathway in a breast cancer xenograft model. Taken together, our results revealed that TMEM97 is a positive modulator of canonical Wnt signaling. TMEM97-mediated Wnt signaling is implicated in the tumorigenesis of breast cancer, and its targeted inhibition may be a promising therapeutic strategy for breast cancer.

The CK1δ/ε-AES axis regulates tumorigenesis and metastasis in colorectal cancer.

Background: Amino-terminal enhancer of split (AES) has been identified as a tumor and metastasis suppressor in some cancers including colorectal cancer (CRC), but very little is known about the regulation of AES expression. Methods: Bioinformatics analysis was used to investigate the expression patterns of AES, CK1δ and CK1ε. The co-immunoprecipitation, GST pull-down, Western Blot, real-time PCR and immunohistochemistry were performed to study the mechanism underlying the regulation of AES expression by CK1δ/ε. The biological function was assessed by in vitro colony formation, transwell, sphere formation, tumor organoids, in vivo tumor metastasis model and patient-derived colorectal tumor xenografts (PDTX) model. Results: A strong inverse relationship was observed between the expression of AES and the expression of CK1δ/ε. Mechanically, AES could interact with CK1δ/ε and SKP2 using its Q domain. SKP2 mediated the ubiquitination and degradation of AES in a CK1δ/ε-dependent manner. CK1δ/ε phosphorylated AES at Ser121 and accelerated the SKP2-mediated ubiquitination and degradation of AES. In colon cancer cells, CK1δ/ε antagonized the effect of wild-type AES but not that of its mutant (S121A) on Wnt and Notch signaling, leading to an increase in the expression of Wnt target genes and Notch target genes. By downregulating the expression of AES, CK1δ/ε enhanced anchorage-independent growth, migration, invasion and sphere formation in colon cancer cells. CK1δ/ε also promoted the growth of APCmin/+ colorectal tumor organoids and liver metastasis in colon cancer mouse models through the regulation of AES degradation. Furthermore, CK1 inhibitor SR3029 treatment suppressed tumor growth via stabilizing AES in APCmin/+ colorectal tumor organoids and patient-derived colorectal tumor xenografts (PDTX). Conclusions: Our results revealed that the CK1δ/ε-AES axis is important for CRC tumorigenesis and metastasis, and targeted inhibition of this axis may be a potential therapeutic strategy for CRC.

Chlorquinaldol targets the ß-catenin and T-cell factor 4 complex and exerts anti-colorectal cancer activity.

Aberrant activation of Wnt signaling plays a critical role in the initiation and progression of colorectal cancer (CRC). Chlorquinaldol (CQD) is a topical antimicrobial agent used to treat skin infections. Little is known about the anticancer activity of CQD and its underlying mechanisms. In this study, CQD was demonstrated to inhibit Wnt/ß-catenin signaling through targeting the downstream part of this pathway. The results showed that CQD could inhibit the acetylation of ß-catenin and disrupt the interaction of ß-catenin with T-cell factor 4 (TCF4), leading to reduced binding of ß-catenin to the promoters of Wnt target genes and downregulation of the expression of these target genes. Moreover, treatment with CQD suppressed the proliferation, migration, invasion and stemness of CRC cells. In APCmin/+ mice and CRC cell xenografts, administration of CQD suppressed tumor growth and the expression of Wnt target genes c-Myc and Leucine-rich G protein-coupled receptor-5 (LGR5). These results strongly suggest that CQD may be a promising therapeutic agent in the treatment of CRC.