Keratin 23 is a stress-inducible marker of mouse and human ductular reaction in liver disease.

BACKGROUND & AIMS: Keratins (K) constitute the epithelial intermediate filaments. Among them, K7/K19 are widely used markers of the regenerative liver response termed ductular reaction (DR) that consists of activated biliary epithelial cells (BECs) and hepatic progenitor cells (HPCs) and correlates with liver disease severity. In the present study we aimed to characterize K23 in the liver. METHODS: We analyzed the expression and localization of K23 in the digestive system under basal conditions as well as in various human and mouse liver diseases/stress models. Cell culture studies were used to study factors regulating K23 expression. RESULTS: In untreated mice, K23 was restricted to biliary epithelia. It was (together with K7/K19) markedly upregulated in three different DR/cholestatic injury models, i.e., multidrug resistance protein 2 (Mdr2) knockouts, animals treated with 3,5-diethoxycarbonyl-1,4-dihydrocollidine or subjected to bile duct ligation. K23 levels correlated with the DR marker Fn14 and immunofluorescence staining showed a distinct co-localization with K7/K19. In chronic human liver disease, K23 expression increased in patients with a more prominent inflammation/fibrosis. A dramatic upregulation (>200times) was observed in patients with acute liver failure (ALF) and end-stage primary biliary cholangitis (PBC). Patients with alcoholic liver cirrhosis displayed increased K23 serum levels. In primary hepatocytes as well as hepatobiliary cell lines, treatment with TNF-related weak inducer of apoptosis (TWEAK), and the type I acute phase inducer interleukin (IL)-1ß but not the type II inducer IL-6 elevated K23 expression. CONCLUSIONS: K23 represents a specific, stress-inducible DR marker, whose levels correlate with liver disease severity. K23 may represent a useful non-invasive DR marker. LAY SUMMARY: Ductular reaction represents a basic response to liver injury and correlates with liver disease severity. Our study identifies K23 as a novel ductular reaction marker in mice and humans.

Loss of keratin 23 enhances growth inhibitory effect of melatonin in gastric cancer.

To investigate the effect of keratin 23 (KRT23) on the anticancer activity of melatonin (MLT) against gastric cancer (GC) cells, microarray analysis was applied to screen differentially expressed genes in AGS GC cells following MLT treatment. Western blotting was used to detect the expression of KRT23 in GC cells and normal gastric epithelial cell line GES­1. KRT23 knockout was achieved by CRISPR/Cas9. Assays of cell viability, colony formation, cell cycle, electric cell­substrate impedance sensing and western blotting were conducted to reveal the biological functions of KRT23­knockout cells without or with MLT treatment. Genes downregulated by MLT were enriched in purine metabolism, pyrimidine metabolism, genetic information processing and cell cycle pathway. Expression levels of KRT23 were downregulated by MLT treatment. Expression levels of KRT23 in AGS and SNU­216 GC cell lines were significantly higher compared with normal gastric epithelial cell line GES­1. KRT23 knockout led to reduced phosphorylation of ERK1/2 and p38, arrest of the cell cycle and inhibition of GC cell proliferation. Moreover, KRT23 knockout further enhanced the inhibitory activity of MLT on the tumor cell proliferation by inhibiting the phosphorylation of p38/ERK. KRT23 knockout contributes to the antitumor effects of MLT in GC via suppressing p38/ERK phosphorylation. In the future, KRT23 might be a potential prognostic biomarker and a novel molecular target for GC.

Combined targeting of KRT23 and NCCRP1 as a potential novel therapeutic approach for the treatment of triple-negative breast cancer.

Background: Breast cancers characterized by triple-negative status tend to be more malignant and have a poorer prognosis. A risk model for predicting breast cancer risk should be developed. Methods: We obtained gene expression and clinical characteristics data using the Clinical Proteomic Tumor Analysis Consortium (CPTAC) and The Cancer Genome Atlas (TCGA) database. Differential gene screening between patients with triple-negative breast cancer (TNBC) and non-triple-negative breast cancers (NTNBC) was performed according to the "edgeR" filter criteria. Univariate and multivariate Cox regression analyses were used to construct a risk model and identify prognosis-related genes. XCELL, TIMER, EPIC, QUANTISEQ, MCPCOUNTER, EPIC, CIBERSORT-ABS, and CIBERSORT software programs were used to determine the extent of tumor immune cell infiltration. To evaluate the clinical responses to breast cancer treatment, the half maximal inhibitory concentration (IC50s) of common chemotherapeutics were calculated using "pRRophetic" and "ggplot2". Cell proliferation was assayed using cell counting kit-8 (CCK8) and 5-Ethynyl-2'-deoxyuridine (EdU) Cell Proliferation Kit. A dual-luciferase reporter assay confirmed the gene regulatory relationship of sex determining region Y-box 10 (SOX10). Results: An assessment model was established for Keratin23 (KRT23) and non-specific cytotoxic cell receptor 1 (NCCRP1) using the univariate and multivariate Cox regression analyses. In addition, high expression levels of KRT23 and NCCRP1 indicated high proliferation and poor prognosis. We also found that the gene expression patterns of multiple genes were significantly more predictive of risks and have a higher level of consistency when assessing risk. In vitro experiments showed that the expressions of KRT23 and NCCRP1 were increased in TNBCs and promoted cell proliferation. Mechanically, the dual-luciferase reporter assay confirmed that SOX10 regulated the expressions of KRT23 and NCCRP1. The risk score model revealed a close relationship between the expressions of KRT23 and NCCRP1, the tumor immune microenvironment, and chemotherapeutics. Conclusions: In conclusion, we constructed a risk assessment model to predict the risk of TNBC patients, which acted as a potential predictor for chemosensitivity.

Identification of Keratin 23 as a Hepatitis C Virus-Induced Host Factor in the Human Liver.

Keratin proteins form intermediate filaments, which provide structural support for many tissues. Multiple keratin family members are reported to be associated with the progression of liver disease of multiple etiologies. For example, keratin 23 (KRT23) was reported as a stress-inducible protein, whose expression levels correlate with the severity of liver disease. Hepatitis C virus (HCV) is a human pathogen that causes chronic liver diseases including fibrosis, cirrhosis, and hepatocellular carcinoma. However, a link between KRT23 and hepatitis C virus (HCV) infection has not been reported previously. In this study, we investigated KRT23 mRNA levels in datasets from liver biopsies of chronic hepatitis C (CHC) patients and in primary human hepatocytes experimentally infected with HCV, in addition to hepatoma cells. Interestingly, in each of these specimens, we observed an HCV-dependent increase of mRNA levels. Importantly, the KRT23 protein levels in patient plasma decreased upon viral clearance. Ectopic expression of KRT23 enhanced HCV infection; however, CRIPSPR/Cas9-mediated knockout did not show altered replication efficiency. Taken together, our study identifies KRT23 as a novel, virus-induced host-factor for hepatitis C virus.