BLIMP1 transcriptionally induced by EGFR activation and post-translationally regulated by proteasome and lysosome is involved in keratinocyte differentiation, migration and inflammation

Decoy receptor 3 is involved in epidermal keratinocyte commitment to terminal differentiation via EGFR and PKC activation

Decoy receptor 3 (DcR3) is a soluble receptor for Fas ligand, LIGHT and TL1A, but it also exerts effector functions. Previously, we found that DcR3 is upregulated in the serum and lesional skin of patients with psoriasis and is upregulated by EGFR activation in proliferating primary human epidermal keratinocytes. However, the functional role of intracellular DcR3 in keratinocyte differentiation is still incompletely defined. Herein, primary cultured human epidermal keratinocytes were differentiated by phorbol 12-myristate 13-acetate (PMA) treatment, calcium treatment and cell confluence, which are three standard in vitro differentiation models. We found that the constitutive expression of the DcR3 gene and protein was progressively suppressed during terminal differentiation of keratinocytes. These changes were correlated with downregulation of EGFR activation during keratinocyte differentiation. EGFR inhibition by gefitinib further decreased confluence-induced suppression of DcR3 mRNA expression, and, vice versa, knocking down DcR3 expression attenuated EGFR and EGFR ligand expression as well as EGFR activation. Under conditions without a change in cell growth, DcR3 silencing reduced the expression of involucrin and transglutaminase 1 but enhanced the induction of the terminal differentiation markers keratin 10 and loricrin. Of note, DcR3 interacted with PKCα and PKCδ and enhanced PKC activity. In keratinocytes with PKCα and PKCδ silencing, differentiation markers were differentially affected. In conclusion, DcR3 expression in keratinocytes is regulated by EGFR and forms a positive feedback loop to orchestrate constitutive EGFR and PKC activity. During differentiation, DcR3 is downregulated and involved in modulating the pattern of terminal differentiation.

A protein linked to cancer and various inflammatory diseases may also be an important driver for the skin condition in psoriasis. The outer surface of the skin is formed by cells called keratinocytes, which transition from a highly proliferative state to a fully mature state where they no longer divide. This developmental process is disrupted in psoriasis. Researchers led by Wan-Wan Lin at National Taiwan University, Taipei, have now identified a prominent role for a protein called decoy receptor 3 (DcR3), which is a biomarker for a variety of disorders and is also abnormally expressed in keratinocytes in psoriatic lesions. Lin and colleagues demonstrated that DcR3 interacts with multiple cellular signaling pathways that coordinate cell differentiation. These findings reveal how aberrant DcR3 activity might lead to the abnormal keratinocyte developmental behavior observed in psoriasis.

Combining explainable machine learning, demographic and multi-omic data to inform precision medicine strategies for inflammatory bowel disease

Inflammatory bowel diseases (IBDs), including ulcerative colitis and Crohn’s disease, affect several million individuals worldwide. These diseases are heterogeneous at the clinical, immunological and genetic levels and result from complex host and environmental interactions. Investigating drug efficacy for IBD can improve our understanding of why treatment response can vary between patients. We propose an explainable machine learning (ML) approach that combines bioinformatics and domain insight, to integrate multi-modal data and predict inter-patient variation in drug response. Using explanation of our models, we interpret the ML models’ predictions to infer unique combinations of important features associated with pharmacological responses obtained during preclinical testing of drug candidates in ex vivo patient-derived fresh tissues. Our inferred multi-modal features that are predictive of drug efficacy include multi-omic data (genomic and transcriptomic), demographic, medicinal and pharmacological data. Our aim is to understand variation in patient responses before a drug candidate moves forward to clinical trials. As a pharmacological measure of drug efficacy, we measured the reduction in the release of the inflammatory cytokine TNFα from the fresh IBD tissues in the presence/absence of test drugs. We initially explored the effects of a mitogen-activated protein kinase (MAPK) inhibitor; however, we later showed our approach can be applied to other targets, test drugs or mechanisms of interest. Our best model predicted TNFα levels from demographic, medicinal and genomic features with an error of only 4.98% on unseen patients. We incorporated transcriptomic data to validate insights from genomic features. Our results showed variations in drug effectiveness (measured by ex vivo assays) between patients that differed in gender, age or condition and linked new genetic polymorphisms to patient response variation to the anti-inflammatory treatment BIRB796 (Doramapimod). Our approach models IBD drug response while also identifying its most predictive features as part of a transparent ML precision medicine strategy.

Blimp-1 Upregulation by Multiple Ligands via EGFR Transactivation Inhibits Cell Migration in Keratinocytes and Squamous Cell Carcinoma

B lymphocyte-induced maturation protein-1 (Blimp-1) is a transcriptional repressor and plays a crucial role in the regulation of development and functions of various immune cells. Currently, there is limited understanding about the regulation of Blimp-1 expression and cellular functions in keratinocytes and cancer cells. Previously we demonstrated that EGF can upregulate Blimp-1 gene expression in keratinocytes, playing a negative role in regulation of cell migration and inflammation. Because it remains unclear if Blimp-1 can be regulated by other stimuli beyond EGF, here we further investigated multiple stimuli for their regulation of Blimp-1 expression in keratinocytes and squamous cell carcinoma (SCC). We found that PMA, TNF-α, LPS, polyIC, H₂O₂ and UVB can upregulate the protein and/or mRNA levels of Blimp-1 in HaCaT and SCC cells. Concomitant EGFR activation was observed by these stimuli, and EGFR inhibitor gefitinib and Syk inhibitor can block Blimp-1 gene expression caused by PMA. Reporter assay of Blimp-1 promoter activity further indicated the involvement of AP-1 in PMA-, TNF-α-, LPS- and EGF-elicited Blimp-1 mRNA expression. Confocal microscopic data indicated the nuclear loclization of Blimp-1, and such localization was not changed by stimuli. Moreover, Blimp-1 silencing enhanced SCC cell migration. Taken together, Blimp-1 can be transcriptionally upregulated by several stimuli in keratinocytes and SCC via EGFR transactivation and AP-1 pathway. These include growth factor PMA, cytokine TNF-α, TLR ligands (LPS and polyIC), and ROS insults (H₂O₂ and UVB). The function of Blimp-1 as a negative regulator of cell migration in SCC can provide a new therapeutic target in SCC.

Expression, purification and functional identification of the modified hEGF protein

Human epidermal growth factor (hEGF) plays an important role in the growth and division of epithelial cells and has good application prospects in skin-related injuries and diseases. Weak skin penetration and rapid clearance of hEGF in skin via the mononuclear phagocyte system have restricted the application of hEGF. To overcome these shortcomings, the recombinant gene TAT-hEGF-CD47 was constructed in our experiments, and the fusion protein TAT-hEGF-CD47 was expressed, purified and renatured. The cell proliferation-promoting function, skin penetration and concentration of TAT-hEGF-CD47 in skin after its application were determined. The results showed that TAT-hEGF-CD47 effectively promoted human skin fibroblast and skin epithelial cell proliferation, and the proliferation-promoting effect was positively correlated with the TAT-hEGF-CD47 concentration. After administration to the skin, TAT-hEGF-CD47 effectively penetrated the epidermal layer of the skin because of the TAT domain and stayed in the skin for a long time because the CD47 fragment slowed its clearance via the mononuclear phagocytic system. In conclusion, TAT-hEGF-CD47 exhibits high cell proliferation-promoting activity, high skin penetration efficiency and long retention time in skin and has laid the foundation for its wide application in skin repair, ulcer, diabetes and even cancer treatments.

From Orai to E-Cadherin: Subversion of Calcium Trafficking in Cancer to Drive Proliferation, Anoikis-Resistance, and Metastasis

The common currency of epithelial differentiation and homeostasis is calcium, stored primarily in the endoplasmic reticulum, rationed according to need, and replenished from the extracellular milieu via store-operated calcium entry (SOCE). This currency is disbursed by the IP3 receptor in response to diverse extracellular signals. The rate of release is governed by regulators of proliferation, autophagy, survival, and programmed cell death, the strength of the signal leading to different outcomes. Intracellular calcium acts chiefly through intermediates such as calmodulin that regulates growth factor receptors such as epidermal growth factor receptor (EGFR), actin polymerization, and adherens junction assembly and maintenance. Here we review this machinery and its role in differentiation, then consider how cancer cells subvert it to license proliferation, resist anoikis, and enable metastasis, either by modulating the level of intracellular calcium or its downstream targets or effectors such as EGFR, E-cadherin, IQGAP1, TMEM16A, CLCA2, and TRPA1. Implications are considered for the roles of E-cadherin and growth factor receptors in circulating tumor cells and metastasis. The discovery of novel, cell type-specific modulators and effectors of calcium signaling offers new possibilities for cancer chemotherapy.

s-HBEGF/SIRT1 circuit-dictated crosstalk between vascular endothelial cells and keratinocytes mediates sorafenib-induced hand-foot skin reaction that can be reversed by nicotinamide

Hand-foot skin reaction (HFSR), among the most significant adverse effects of sorafenib, has been limiting the clinical benefits of this frontline drug in treating various malignant tumors. The mechanism underlying such toxicity remains poorly understood, hence the absence of effective intervention strategies. In the present study, we show that vascular endothelial cells are the primary cellular target of sorafenib-induced HFSR wherein soluble heparin-binding epidermal growth factor (s-HBEGF) mediates the crosstalk between vascular endothelial cells and keratinocytes. Mechanistically, s-HBEGF released from vascular endothelial cells activates the epidermal growth factor receptor (EGFR) on keratinocytes and promotes the phosphorylation of c-Jun N-terminal kinase 2 (JNK2), which stabilizes sirtuin 1 (SIRT1), an essential keratinization inducer, and ultimately gives rise to HFSR. The administration of s-HBEGF in vivo could sufficiently induce hyper-keratinization without sorafenib treatment. Furthermore, we report that HBEGF neutralization antibody, Sirt1 knockdown, and a classic SIRT1 inhibitor nicotinamide could all significantly reduce the sorafenib-induced HFSR in the mouse model. It is noteworthy that nicotinic acid, a prodrug of nicotinamide, could substantially reverse the sorafenib-induced HFSR in ten patients in a preliminary clinical study. Collectively, our findings reveal the mechanism of vascular endothelial cell-promoted keratinization in keratinocytes and provide a potentially promising therapeutic strategy for the treatment of sorafenib-induced HFSR.

A short peptide potentially promotes the healing of skin wound

Skin wound, a common form of skin damage in daily life, remains a serious challenge in clinical treatment. Bioactive peptides with high efficiency have been considered as potential therapeutic candidates for wound healing. In this report, a novel short linear peptide, with mature peptide sequence of 'GLLSGINAEWPC' and no obvious similarity with other known bioactive peptides, was identified by genomic method from the skin of odorous frog, Odorrana andersonii Our results suggested that OA-GL12 (OA: abbreviation of species (O. andersonii), GL: two initial amino acids, 12: peptide length) obviously accelerated the scratch-healing of keratinocytes and human fibroblasts in a time- and concentration-dependent manner. Meanwhile, OA-GL12 showed significant effect in promoting the wound healing on the full-thickness skin wound model. Inflammatory assay results demonstrated that OA-GL12 induced the secretion of tumor necrosis factor (TNF) and transforming growth factor β1 (TGF-β1) on murine macrophage cell line (RAW264.7), which might explain the powerful accelerating capacity of wound healing. Moreover, results also indicated that epidermal growth factor receptor (EGFR) was involved in the mechanisms underlying the scratch-healing promoting activity of OA-GL12. In addition, OA-GL12 showed obvious free radical scavenging activity. Results supported that OA-GL12 did not exert risk in acute toxicity, hemolytic activity, and direct antibacterial activity. The remarkable effect of OA-GL12 on promoting wound healing verified in this research made it potential to be a novel template for the development of wound healing-promoting agents.