MicroRNAs (miRNAs) play pivotal roles in tumorigenesis as either tumor suppressors or oncogenes. In the present study, we discovered and demonstrated the tumor suppressive function of a novel miRNA miR-5582-5p. miR-5582-5p induced apoptosis and cell cycle arrest in cancer cells, but not in normal cells. GAB1, SHC1, and CDK2 were identified as direct targets of miR-5582-5p. Knockdown of GAB1/SHC1 or CDK2 phenocopied the apoptotic or cell cycle arrest-inducing function of miR-5582-5p, respectively. The expression of miR-5582-5p was lower in tumor tissues than in adjacent normal tissues of colorectal cancer patients, while the expression of the target proteins exhibited patterns opposite to that of miR-5582-5p. Intratumoral injection of a miR-5582-5p mimic or induced expression of miR-5582-5p in tumor cells suppressed tumor growth in HCT116 xenografts. Collectively, our results suggest a novel tumor suppressive function for miR-5582-5p and its potential applicability for tumor control.

One of the initial steps in metastatic dissemination is the epithelial-mesenchymal transition (EMT). Along this line, microRNAs (miRNAs) have been shown to function as important regulators of tumor progression at various stages. Therefore, we performed a functional screening for EMT-regulating miRNAs and identified several candidate miRNAs. Among these, we demonstrated that miR-5003-3p induces cellular features characteristic of EMT. miR-5003-3p induced upregulation of Snail, a key EMT-promoting transcription factor and transcriptional repressor of E-cadherin, through protein stabilization. MDM2 was identified as a direct target of miR-5003-3p, the downregulation of which induced Snail stabilization. E-cadherin was also demonstrated to be a direct target of miR-5003-3p, reinforcing the EMT-promoting function of miR-5003-3p. In situ hybridization and immunohistochemical analyses using tissue microarrays revealed that miR-5003-3p expression was higher in paired metastatic breast carcinoma tissues than in primary ductal carcinoma tissues, and was inversely correlated with the expression of MDM2 and E-cadherin. Furthermore, miR-5003-3p enhanced the formation of metastatic nodules in the lungs of mice in a tail vein injection experiment. Collectively, our results suggest that miR-5003-3p functions as a metastasis activator by promoting EMT through dual regulation of Snail stability and E-cadherin, and may therefore be a potential therapeutic target in metastatic cancers.

Type I collagen is the major constituent of the skin and the reduction of dermal type I collagen content is closely associated with the intrinsic skin aging. We here found that esculetin, 6,7-dihydroxycoumarin, strongly induces type I procollagen expression in human dermal fibroblasts. Esculetin not only increased protein levels of type I procollagen but also increased mRNA levels of COL1A1 but not COL1A2. Esculetin activated the MAPKs (ERK1/2, p38, JNK) and PI3K/Akt pathways, through which it promoted the type I procollagen expression. We also demonstrated that the binding motifs for transcription factor Sp1 occur with the highest frequency in the COL1A1 promoter and that esculetin increases the Sp1 expression through the MAPK and PI3K/Akt pathways. These results suggest that esculetin promotes type I procollagen expression through the MAPK and PI3K/Akt pathways and that Sp1 might be involved in the esculetin-induced type I procollagen expression via activation of the COL1A1 transcription.

Background Oxidative stress induced by chronic hyperglycemia is recognized as a significant mechanistic contributor to the development of diabetic kidney disease (DKD). Nonphagocytic nicotinamide adenine dinucleotide phosphate oxidase 4 (Nox4) is a major source of reactive oxygen species (ROS) in many cell types and in the kidney tissue of diabetic animals. We designed this study to explore the therapeutic potential of chloroquine (CQ) and amodiaquine (AQ) for inhibiting mitochondrial Nox4 and diabetic tubular injury. Methods Human renal proximal tubular epithelial cells (hRPTCs) were cultured in high-glucose media (30 mM D-glucose), and diabetes was induced with streptozotocin (STZ, 50 mg/kg i.p. for 5 days) in male C57BL/6J mice. CQ and AQ were administered to the mice via intraperitoneal injection for 14 weeks. Results CQ and AQ inhibited mitochondrial Nox4 and increased mitochondrial mass in hRPTCs under high-glucose conditions. Reduced mitochondrial ROS production after treatment with the drugs resulted in decreased endoplasmic reticulum (ER) stress, suppressed inflammatory protein expression and reduced cell apoptosis in hRPTCs under high-glucose conditions. Notably, CQ and AQ treatment diminished Nox4 activation and ER stress in the kidneys of STZ-induced diabetic mice. In addition, we observed attenuated inflammatory protein expression and albuminuria in STZ-induced diabetic mice after CQ and AQ treatment. Conclusion We substantiated the protective actions of CQ and AQ in diabetic tubulopathy associated with reduced mitochondrial Nox4 activation and ER stress alleviation. Further studies exploring the roles of mitochondrial Nox4 in the pathogenesis of DKD could suggest new therapeutic targets for patients with DKD.