Knockdown of HMGN5 expression by RNA interference induces cell cycle arrest in human lung cancer cells

HMGN5 promotes proliferation and invasion via the activation of Wnt/β-catenin signaling pathway in pancreatic ductal adenocarcinoma

Pancreatic ductal adenocarcinoma (PDAC) is a highly aggressive carcinoma with a poor prognosis. A recent study has demonstrated that high mobility group nucleosome binding domain 5 (HMGN5) was involved in tumorigenesis and progression of multiple types of human cancers. However, the role of HMGN5 in PDAC is unknown. The objective of the present study was to analyze the function and novel mechanism of HMGN5 involved in PDAC cell progression. It was firstly revealed that the expression of HMGN5 was significantly upregulated in PDAC cell lines and tissues, when compared with that in normal pancreatic duct epithelial cells and adjacent normal pancreatic tissues. In vitro assay revealed that HMGN5 silencing impaired PDAC cell viability, proliferation, migration and invasion. Similarly, tumor growth rate was also decreased in vivo following HMGN5 silencing. Furthermore, it was demonstrated that HMGN5 silencing significantly inhibited epithelial-mesenchymal transition in vitro. Notably, HMGN5-medicated Wnt/β-catenin signaling pathway activation was observed to be one of the critical signal transduction pathways that associates HMGN5 with EMT activation. Collectively, the results indicated the important role of HMGN5 in PDAC cell proliferation and metastasis, and provide a promising target against the transcriptional program of PDAC.

Research advances in HMGN5 and cancer

High-mobility group nucleosome-binding domain 5 (HMGN5) is a new member of the high-mobility group N (HMGN) protein family that is involved in nucleosomal binding and transcriptional activation. It was first discovered in mouse, and recent studies found that the expressions of HMGN5 in many human cancers were also highly regulated, such as prostate, bladder, breast, and lung and clear cell renal cell carcinoma. Numerous reports have demonstrated that HMGN5 plays significant roles in many biological and pathological conditions, such as in developmental defects, hypersensitivity to stress, embryonic stem cell differentiation, and tumor progression. Importantly, deficiency of HMGN5 has been shown to be linked to cancer cell growth, cell cycle regulation, migration, invasion, and clinical outcomes, and it represents a promising therapeutic target for many malignant tumors. In the present review, we provide an overview of the current knowledge concerning the role of HMGN5 in cancer development and progression.

HMGB1 in health and disease

Complex genetic and physiological variations as well as environmental factors that drive emergence of chromosomal instability, development of unscheduled cell death, skewed differentiation, and altered metabolism are central to the pathogenesis of human diseases and disorders. Understanding the molecular bases for these processes is important for the development of new diagnostic biomarkers, and for identifying new therapeutic targets. In 1973, a group of non-histone nuclear proteins with high electrophoretic mobility was discovered and termed high-mobility group (HMG) proteins. The HMG proteins include three superfamilies termed HMGB, HMGN, and HMGA. High-mobility group box 1 (HMGB1), the most abundant and well-studied HMG protein, senses and coordinates the cellular stress response and plays a critical role not only inside of the cell as a DNA chaperone, chromosome guardian, autophagy sustainer, and protector from apoptotic cell death, but also outside the cell as the prototypic damage associated molecular pattern molecule (DAMP). This DAMP, in conjunction with other factors, thus has cytokine, chemokine, and growth factor activity, orchestrating the inflammatory and immune response. All of these characteristics make HMGB1 a critical molecular target in multiple human diseases including infectious diseases, ischemia, immune disorders, neurodegenerative diseases, metabolic disorders, and cancer. Indeed, a number of emergent strategies have been used to inhibit HMGB1 expression, release, and activity in vitro and in vivo. These include antibodies, peptide inhibitors, RNAi, anti-coagulants, endogenous hormones, various chemical compounds, HMGB1-receptor and signaling pathway inhibition, artificial DNAs, physical strategies including vagus nerve stimulation and other surgical approaches. Future work further investigating the details of HMGB1 localization, structure, post-translational modification, and identification of additional partners will undoubtedly uncover additional secrets regarding HMGB1's multiple functions.

Evolution of high mobility group nucleosome-binding proteins and its implications for vertebrate chromatin specialization

High mobility group (HMG)-N proteins are a family of small nonhistone proteins that bind to nucleosomes (N). Despite the amount of information available on their structure and function, there is an almost complete lack of information on the molecular evolutionary mechanisms leading to their exclusive differentiation. In the present work, we provide evidence suggesting that HMGN lineages constitute independent monophyletic groups derived from a common ancestor prior to the diversification of vertebrates. Based on observations of the functional diversification across vertebrate HMGN proteins and on the extensive silent nucleotide divergence, our results suggest that the long-term evolution of HMGNs occurs under strong purifying selection, resulting from the lineage-specific functional constraints of their different protein domains. Selection analyses on independent lineages suggest that their functional specialization was mediated by bursts of adaptive selection at specific evolutionary times, in a small subset of codons with functional relevance-most notably in HMGN1, and in the rapidly evolving HMGN5. This work provides useful information to our understanding of the specialization imparted on chromatin metabolism by HMGNs, especially on the evolutionary mechanisms underlying their functional differentiation in vertebrates.