Loss of nuclear pro-IL-16 facilitates cell cycle progression in human cutaneous T cell lymphoma

SKping cell cycle regulation: role of ubiquitin ligase SKP2 in hematological malignancies

SKP2 (S-phase kinase-associated protein 2) is a member of the F-box family of substrate-recognition subunits in the SCF ubiquitin-protein ligase complexes. It is associated with ubiquitin-mediated degradation in the mammalian cell cycle components and other target proteins involved in cell cycle progression, signal transduction, and transcription. Being an oncogene in solid tumors and hematological malignancies, it is frequently associated with drug resistance and poor disease outcomes. In the current review, we discussed the novel role of SKP2 in different hematological malignancies. Further, we performed a limited in-silico analysis to establish the involvement of SKP2 in a few publicly available cancer datasets. Interestingly, our study identified Skp2 expression to be altered in a cancer-specific manner. While it was found to be overexpressed in several cancer types, few cancer showed a down-regulation in SKP2. Our review provides evidence for developing novel SKP2 inhibitors in hematological malignancies. We also investigated the effect of SKP2 status on survival and disease progression. In addition, the role of miRNA and its associated families in regulating Skp2 expression was explored. Subsequently, we predicted common miRNAs against Skp2 genes by using miRNA-predication tools. Finally, we discussed current approaches and future prospective approaches to target the Skp2 gene by using different drugs and miRNA-based therapeutics applications in translational research.

Differential gene expression of red-spotted grouper (Epinephelus akaara) in response to lipopolysaccharide, poly I:C, and nervous necrosis virus revealed by RNA-seq data

Red-spotted grouper (Epinephelus akaara) is a popular aquaculture species with high commercial value in the food industry. However, some infectious diseases may cause mass mortality in cultural practice. Therefore, it is important to understand the immune responses of red-spotted groupers upon pathogenic invasion to develop successful disease prevention mechanisms. Here, we analyzed the transcriptomic profiles of red-spotted grouper head kidney stimulated with lipopolysaccharide (LPS), polyinosinic:polycytidylic acid (poly I:C), and nervous necrosis virus (NNV) and identified differentially expressed genes (DEGs) using RNA-sequencing technology. Cluster analysis of the identified DEGs showed DEG distribution in nine separate clusters based on their expression patterns. However, significant upregulation of most DEGs was observed 6 h after poly I:C stimulation. The DEGs were functionally annotated using Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analysis, which revealed significant expression of many immune-related signaling pathways, including antiviral, protein translation, cellular protein catabolic process, inflammatory responses, DNA repair, and cell division. Furthermore, selected DEGs were validated by quantitative real-time PCR, confirming the reliability of our findings. Collectively, this study provides insight into the immune responses of red-spotted groupers, thereby expanding the understanding of fish immunity.

The Ubiquitin Proteasome System in Hematological Malignancies: New Insight into Its Functional Role and Therapeutic Options

The ubiquitin proteasome system (UPS) is the main cellular degradation machinery designed for controlling turnover of critical proteins involved in cancer pathogenesis, including hematological malignancies. UPS plays a functional role in regulating turnover of key proteins involved in cell cycle arrest, apoptosis and terminal differentiation. When deregulated, it leads to several disorders, including cancer. Several studies indicate that, in some subtypes of human hematological neoplasms such as multiple myeloma and Burkitt’s lymphoma, abnormalities in the UPS made it an attractive therapeutic target due to pro-cancer activity. In this review, we discuss the aberrant role of UPS evaluating its impact in hematological malignancies. Finally, we also review the most promising therapeutic approaches to target UPS as powerful strategies to improve treatment of blood cancers.

Dysregulated expression of SKP2 and its role in hematological malignancies

S-phase kinase-associated protein 2 (SKP2) is a well-studied F-box protein and a critical part of the Skp1-Cul1-Fbox (SCF) E3 ligase complex. It controls cell cycle by regulating the expression level of p27 and p21 through ubiquitination and proteasomal degradation. SKP2-mediated loss of p27Kip1 is associated with poor clinical outcome in various types of cancers including hematological malignancies. It is however well established that SKP2 is an oncogene, and its targeting may be an attractive therapeutic strategy for the management of hematological malignancies. In this article, we have highlighted the recent findings from our group and other investigators regarding the role of SKP2 in the pathogenesis of hematological malignancies.

Interaction of Cx43 with Hsc70 regulates G1/S transition through CDK inhibitor p27

Connexin 43 (Cx43) functions as a cell growth suppressor. We have demonstrated that Cx43 interacts with heat shock cognate protein 70 (Hsc70) for regulating cell proliferation. Hsc70 interacts with CDK inhibitor p27, which regulates the assembly and subcellular localization of cyclin D1-CDK4-p27 complex. However, the involvement of p27 with Cx43-mediated cell cycle suppression is still poorly understood. Here, we report that nuclear accumulation of p27 is reduced by overexpression of Cx43, and that this reduction is restored by co-overexpression with Hsc70. We found that Cx43 competes with p27 for binding to Hsc70, and as a result, decreases the level of Hsc70 in cyclin D1-CDK4-p27 complex, leading to prevention of the nuclear translocation of the complex and the G1/S transition. Collectively, our findings suggest that, in Cx43 up-regulation, which is most likely an emergency measure, Cx43-Hsc70 interaction regulates cell cycle G1/S progression through a novel mechanism by which Cx43-Hsc70 interaction prevents the nuclear accumulation of p27 through controlling the nuclear translocation of cyclin D1-CDK4-p27 complex.

A specific DNA methylation profile correlates with a high risk of disease progression in stage I classical (Alibert-Bazin type) mycosis fungoides

BACKGROUND

Mycosis fungoides (MF) is the most common type of cutaneous T-cell lymphoma; in its classical presentation it evolves slowly, but it can have an aggressive course in a subset of patients.

OBJECTIVES

To investigate the impact of epigenetic mechanisms on the progression of early stage MF.

METHODS

We analysed DNA methylation at 12 different loci and long interspersed nucleotide elements-1 (LINE-1), as a surrogate marker of global methylation, on tissue samples from 41 patients with stage I MF followed up for at least 12 years or until disease progression. The methylation profiles were also analysed in two T-cell lymphoma cell lines and correlated with gene expression.

RESULTS

The selected loci were methylated in a tumour-specific manner; concomitant hypermethylation of at least four loci was more frequent in cases progressing within 1-3 and 3-6 years than in late-progressive or non-progressive cases. LINE-1 methylation was significantly lower in rapidly progressive MF at 3 years (61%, P < 0·001) than in those at 12 years (67%). PPARG, SOCS1 and NEUROG1 methylation showed remarkable differences among the prognostic groups, but only PPARG was a significant predictor of disease progression within 6 years, after adjustment for patients' age or gender. Strikingly, a methylation profile similar to progressive cases was found in highly proliferative Sézary-derived HUT78 cells but not in MF-derived HUT102 cells. Exposure to a DNA demethylating agent restored sensitivity to apoptosis and cell cycle arrest.

CONCLUSIONS

Epigenetic silencing of specific biomarkers can predict the risk of disease progression in early-stage MF, providing insights into its pathogenesis, prognosis and therapy.

CCR4+T cell recruitment to the skin in mycosis fungoides: potential contributions by thymic stromal lymphopoietin and interleukin-16

Mycosis fungoides (MF) is characterized by skin accumulation of CCR4+CCR7- effector memory T cells; however the mechanism for their recruitment is not clearly identified. Thymic Stromal Lymphopoietin (TSLP) is a keratinocyte-derived cytokine that triggers Th2 immunity and is associated with T cell recruitment to the skin in atopic dermatitis. Interleukin-16 (IL-16) is a chemoattractant and growth factor for CD4+T cells. We hypothesized that TSLP and IL-16 could contribute to recruitment of malignant T cells in MF. We found elevated TSLP and IL-16 in very early stage patients' plasma and skin biopsies, prior to elevation in CCL22. Both TSLP and IL-16 induced migratory responses of CCR4+TSLPR+CD4+CCR7-CD31+cells, characteristic of malignant T cells in the skin. Co-stimulation also resulted in significant proliferative responses. We conclude that TSLP and IL-16, expressed at early stages of disease, function to recruit malignant T cells to the skin and contribute to their enhanced proliferation.

Regulation of cellular processes by interleukin-16 in homeostasis and cancer

Interleukin-16 (IL-16) is generated as a precursor molecule that is cleaved by caspase-3 to produce a pro-IL-16 molecule that functions as a regulator of T cell growth, and a secreted peptide that functions as a CD4 and/or CD9 ligand for induction of cell motility and activation. IL-16 has been predominantly studied as a contributing factor in the orchestration of an immune response; however, more recently IL-16 bioactivity has been closely associated with the progression of a number of different cancers. While the association between IL-16 plasma levels and tumor progression has been reported for many types of cancer, the mechanism for IL-16 involvement has been partially elucidated for three of the cancer types, cutaneous T cell lymphoma (CTCL), multiple myeloma (MM), and breast cancer. The mechanism for promoting cell growth is different in each of these cancers and involves a sequence mutation in the pro-molecule facilitating decreased p27(KIP1) levels in CTCL; over expression of the secreted IL-16 molecule to induce proliferation in CTCL T cells, and plasma cells in MM; and increased secreted IL-16 acting to recruit CD4+ pro-tumor macrophages in breast cancer. This article will review the cellular process for generating IL-16, the biological activities for both the pro- and secreted forms of the protein, and then the mechanism by which these forms contribute to cancer progression. As a soluble cytokine the ability to reduce or eliminate IL-16 synthesis through siRNA approaches or bioactivity through the use of neutralizing antibody treatment may represent a novel therapeutic approach.

HSPA8/HSC70 chaperone protein: structure, function, and chemical targeting

HSPA8/HSC70 protein is a fascinating chaperone protein. It represents a constitutively expressed, cognate protein of the HSP70 family, which is central in many cellular processes. In particular, its regulatory role in autophagy is decisive. We focused this review on HSC70 structure-function considerations and based on this, we put a particular emphasis on HSC70 targeting by small molecules and peptides in order to develop intervention strategies that deviate some of HSC70 properties for therapeutic purposes. Generating active biomolecules regulating autophagy via its effect on HSC70 can effectively be designed only if we understand the fine relationships between HSC70 structure and functions.

Comprehensive analysis of PTEN status in Sezary syndrome

Sézary syndrome (SS) is an incurable leukemic variant of cutaneous T-cell lymphoma characterized by recurrent chromosomal alterations, among which, chromosome 10q deletion is very frequent. In this study, we investigated the PTEN status, on locus 10q23, in 44 SS patients; our findings show that PTEN is deleted in 36% of SS cases, whereas PTEN downregulation is observed in almost all of the samples evaluated by quantitative reverse-transcriptase polymerase chain reaction and Western blotting analysis. Neither DNA sequence mutation nor promoter hypermethylation were found at the PTEN locus, but we demonstrate that PTEN level can be also reduced by a group of miRs previously found upregulated and of prognostic relevance in SS; particularly, miR-21, miR-106b, and miR-486 were able to control PTEN abundance either in vitro or in vivo. Finally, because reduced PTEN activates the PI3/AKT-mediated pathway of cell growth and survival, we demonstrate that PTEN deficiency is associated with activated AKT in skin resident but not circulating SS cells, suggesting that the cutaneous milieu may strongly contribute to the SS cell growth. To our knowledge, this is the first study fully exploring the PTEN status in a large cohort of SS patients, unveiling potential elements of clinical utility in this malignancy.

Role of SKP1-CUL1-F-box-protein (SCF) E3 ubiquitin ligases in skin cancer

Many biological processes such as cell proliferation, differentiation, and cell death depend precisely on the timely synthesis and degradation of key regulatory proteins. While protein synthesis can be regulated at multiple levels, protein degradation is mainly controlled by the ubiquitin-proteasome system (UPS), which consists of two distinct steps: (1) ubiquitylation of targeted protein by E1 ubiquitin-activating enzyme, E2 ubiquitin-conjugating enzyme and E3 ubiquitin ligase, and (2) subsequent degradation by the 26S proteasome. Among all E3 ubiquitin ligases, the SCF (SKP1-CUL1-F-box protein) E3 ligases are the largest family and are responsible for the turnover of many key regulatory proteins. Aberrant regulation of SCF E3 ligases is associated with various human diseases, such as cancers, including skin cancer. In this review, we provide a comprehensive overview of all currently published data to define a promoting role of SCF E3 ligases in the development of skin cancer. The future directions in this area of research are also discussed with an ultimate goal to develop small molecule inhibitors of SCF E3 ligases as a novel approach for the treatment of human skin cancer. Furthermore, altered components or substrates of SCF E3 ligases may also be developed as the biomarkers for early diagnosis or predicting prognosis.