We collected paired samples of tumor and adjacent normal colorectal tissues from 22 patients with colorectal carcinoma to compare the differences in the expression of lysine specific demethylase 1 (LSD1) in these two tissues. The results showed that in 19 paired samples (86.4%), LSD1 is more highly expressed in tumor tissue than in normal tissue. To explore the role of LSD1 in colorectal tumorigenesis, we used somatic cell gene targeting to generate an LSD1 knockout (KO) HCT 116 human colorectal cancer cell line as a research model. The analysis of phenotypic changes showed that LSD1 KO colorectal cancer cells are less tumorigenic, both in vivo and in vitro. The differential expression analysis of the cells by mRNA sequencing (RNA-Seq) yielded 2,663 differentially expressed genes, and 28 of these genes had highly significant differences (Q <0.01). We then selected the 4 colorectal cancer-related genes ADM, DKK1, HAS3 and SMURF2 for quantitative real-time PCR verification. The results showed that the differences in the expression of ADM, DKK1 and HAS3 were consistent with those measured using the RNA-Seq data. As DKK1 was the gene with the most significant differential expression, we analyzed the key proteins of the DKK1-related Wnt/β-catenin signaling pathway and found that, after knocking out LSD1, the amount of free β-catenin translocated to the nucleus was significantly reduced and that the transcription of the signaling pathway target gene c-Myc was down-regulated. Our studies show that LSD1 activates the Wnt/β-catenin signaling pathway by down-regulating the pathway antagonist DKK1, which may be one of the mechanisms leading to colorectal tumorigenesis.

Hepatic ischemia/reperfusion injury (IRI) is a common cause of morbidity and mortality in liver transplantation settings and involves severe cell death and inflammatory responses. MicroRNA-191 has recently been reported to be abnormally expressed in hepatocellular carcinoma and other liver diseases in the regulation of important cellular processes. However, little is known about its function and molecular mechanism in IRI. Here, we demonstrate that miR-191 is significantly upregulated in a cultured cell line during hypoxia/reperfusion (H/R) and in liver tissue during IRI in mice. The activation of miR-191 under hypoxic conditions is mediated by hypoxia-inducible factor-1α (HIF1α) binding to its promoter region. Global miR-191 KO mice were constructed by CRISPR/Cas9 system, and we found that miR-191 deficiency markedly reduces liver tissue damage, cell inflammatory responses and cell death in a mouse hepatic IRI model. Under the H/R condition, miR-191 overexpression promotes G0/G1 cell cycle arrest and cell apoptosis, but inhibition of miR-191 facilitates cell cycle progression and decreases cell death. Mechanistically, upon induction by hypoxia or ischemia, miR-191 suppresses expression of ZO-1-associated Y-box factor (ZONAB) and its downstream factor Cyclin D1, consequently resulting in cell death and tissue injury. Moreover, the effects of miR-191 on cell cycle arrest and cell apoptosis are abrogated by ZONAB overexpression, and vice versa. Taken together, our results indicate an important role of the HIF1α/miR-191/ZONAB signaling pathway in hepatic IRI and suggest miR-191 as a novel therapeutic target for the treatment of liver IRI.

MAPK/JNK signaling is pivotal in carcinogenesis. However, ubiquitin-mediated homeostasis of JNK remains to be verified. Here, with results from RNA sequencing (RNA-seq) and luciferase reporter pathway identification, we show that USP14 orchestrates MAPK/JNK signaling and identify USP14 as a deubiquitinase that interacts and stabilizes JNK. USP14 is elevated in colorectal cancer patients and is positively associated with JNK protein and downstream gene expression. USP14 ablation reduces cancer cell proliferation in vitro and colorectal tumorigenesis in vivo by downregulating MAPK/JNK pathway activation. Moreover, USP14 expression is induced by TNF-α, forming a feedback loop with JNK and leading to tumor amplification. Our study suggests that elevated expression of USP14 promotes MAPK/JNK signaling by stabilizing JNK, which in turn augments colorectal carcinogenesis, indicating a potential therapeutic target for colorectal cancer patients with increased USP14 expression.