PAK5 potentiates slug transactivation of N-cadherin to facilitate metastasis of renal cell carcinoma

Renal cell carcinoma (RCC) is an aggravating cancer with a poor prognosis and a high rate of metastasis. PAK5, a p21-activated kinases, has shown to be overexpressed in a variety of cancers, including RCC. In previous studies, we discovered that PAK5 regulates cell migration and invasion in RCC cell lines. However, the underlying mechanisms remain obscure. In this study, we consolidated that PAK5 confers a pro-metastatic phenotype RCC cells in vitro and exacerbates metastasis in vivo. High PAK5 expression was associated with an advanced TNM stage and a lower overall survival. Furthermore, PAK5 increases the expression level of N-cadherin. In terms of mechanism, PAK5 bound to Slug and phosphorylated it at serine 87. As a result, phosphorylated Slug transactivated N-cadherin, accelerating the epithelial-mesenchymal transition. Collectively, Slug is a novel PAK5 substrate, and PAK5-mediated phosphorylation of Slug-S87 increases N-cadherin and the pro-metastatic phenotype of RCC, implying that phosphorylated Slug-S87 could be a therapeutic target in progressive RCC.

HPV E7-drived ALKBH5 promotes cervical cancer progression by modulating m6A modification of PAK5

Human papillomavirus (HPV) infection is a causative agent of cervical cancer (CC). N6-methyladenosine (m6A) modification is implicated in carcinogenesis and tumor progression. However, the involvement of m6A modification in HPV-involved CC remains unclear. Here we showed that HPV E6/7 oncoproteins affected the global m6A modification and E7 specifically promoted the expression of ALKBH5. We found that ALKBH5 was significantly upregulated in CC and might serve as a valuable prognostic marker. Forced expression of ALKBH5 enhanced the malignant phenotypes of CC cells. Mechanistically, we discovered that E7 increased ALKBH5 expression through E2F1-mediated activation of the H3K27Ac and H3K4Me3 histone modifications, as well as post-translational modification mediated by DDX3. ALKBH5-mediated m6A demethylation enhanced the expression of PAK5. The m6A reader YTHDF2 bound to PAK5 mRNA and regulated its stability in an m6A-dependent manner. Moreover, ALKBH5 promoted tumorigenesis and metastasis of CC by regulating PAK5. Overall, our findings herein demonstrate a significant role of ALKBH5 in CC progression in HPV-positive cells. Thus, we propose that ALKBH5 may serve as a prognostic biomarker and therapeutic target for CC patients.

COPS6 promotes tumor progression and reduces CD8+ T cell infiltration by repressing IL-6 production to facilitate tumor immune evasion in breast cancer

Due to poor T cell infiltration, tumors evade immune surveillance. Increased CD8+ T cell infiltration in breast cancer suggests a satisfactory response to immunotherapy. COPS6 has been identified as an oncogene, but its role in regulating antitumor immune responses has not been defined. In this study, we investigated the impact of COPS6 on tumor immune evasion in vivo. Tumor transplantation models were established in C57BL/6 J mice and BALB/c nude mice. Flow cytometry was conducted to identify the role of COPS6 on tumor-infiltrating CD8+ T cells. By analyzing the TCGA and GTEx cohort, we found that COPS6 expression was significantly up-regulated in a variety of cancers. In human osteosarcoma cell line U2OS and non-small cell lung cancer cell line H1299, we showed that p53 negatively regulated COPS6 promoter activity. In human breast cancer MCF-7 cells, COPS6 overexpression stimulated p-AKT expression as well as the proliferation and malignant transformation of tumor cells, whereas knockdown of COPS6 caused opposite effects. Knockdown of COPS6 also significantly suppressed the growth of mouse mammary cancer EMT6 xenografts in BALB/c nude mice. Bioinformatics analysis suggested that COPS6 was a mediator of IL-6 production in the tumor microenvironment and a negative regulator of CD8+ T cell tumor infiltration in breast cancer. In C57BL6 mice bearing EMT6 xenografts, COPS6 knockdown in the EMT6 cells increased the number of tumor-infiltrating CD8+ T cells, while knockdown of IL-6 in COPS6KD EMT6 cells diminished tumor infiltrating CD8+ T cells. We conclude that COPS6 promotes breast cancer progression by reducing CD8+ T cell infiltration and function via the regulation of IL-6 secretion. This study clarifies the role of p53/COPS6/IL-6/CD8+ tumor infiltrating lymphocytes signaling in breast cancer progression and immune evasion, opening a new path for development of COPS6-targeting therapies to enhance tumor immunogenicity and treat immunologically "cold" breast cancer.

NRP1 contributes to stemness and potentiates radioresistance via WTAP-mediated m6A methylation of Bcl-2 mRNA in breast cancer

NRP1 is a transmembrane glycoprotein that is highly expressed in a variety of tumors. There is evidence that NRP1 can enhance the stem cell properties of tumor cells, which are thought to be resistant to radiotherapy. This study aims to elucidate the potential mechanism of NRP1 in radiation resistance. We transfected NRP1 siRNA and plasmid in breast cancer cells to detect the expression of cancer stem cell markers by western blot and qRT-PCR. The effect of NRP1 on radiotherapy resistance was assesses by immunofluorescence and flow cytometry. In vivo, we established xenograft tumor model treating with shRNA-NRP1 to assess radiotherapy sensitivity. We found that NRP1 could enhance the stem cell properties and confer radioresistance of breast cancer cells. Mechanistically, we proved that NRP1 reduced IR-induced apoptosis by downregulation of Bcl-2 via methyltransferase WTAP in m6A-depentent way. It is suggested that these molecules may be the therapeutic targets for improving the efficacy of radiotherapy for breast cancer.

The Role of Alternative Splicing in Cancer: Regulatory Mechanism, Therapeutic Strategy, and Bioinformatics Application

[Formula: see text] Alternative splicing (AS) can generate distinct transcripts and subsequent isoforms that play differential functions from the same pre-mRNA. Recently, increasing numbers of studies have emerged, unmasking the association between AS and cancer. In this review, we arranged AS events that are closely related to cancer progression and presented promising treatments based on AS for cancer therapy. Obtaining proliferative capacity, acquiring invasive properties, gaining angiogenic features, shifting metabolic ability, and getting immune escape inclination are all splicing events involved in biological processes. Spliceosome-targeted and antisense oligonucleotide technologies are two novel strategies that are hopeful in tumor therapy. In addition, bioinformatics applications based on AS were summarized for better prediction and elucidation of regulatory routines mingled in. Together, we aimed to provide a better understanding of complicated AS events associated with cancer biology and reveal AS a promising target of cancer treatment in the future.

MicroRNA-138-1-3p sensitizes sorafenib to hepatocellular carcinoma by targeting PAK5 mediated β-catenin/ABCB1 signaling pathway

Background

Sorafenib is a kinase inhibitor that is used as a first-line therapy in advanced hepatocellular carcinoma (HCC) patients. However, the existence of sorafenib resistance has limited its therapeutic effect. Through RNA sequencing, we demonstrated that miR-138-1-3p was downregulated in sorafenib resistant HCC cell lines. This study aimed to investigate the role of miR-138-1-3p in sorafenib resistance of HCC.

Methods

In this study, quantitative real-time PCR (qPCR) and Western Blot were utilized to detect the levels of PAK5 in sorafenib-resistant HCC cells and parental cells. The biological functions of miR-138-1-3p and PAK5 in sorafenib-resistant cells and their parental cells were explored by cell viability assays and flow cytometric analyses. The mechanisms for the involvement of PAK5 were examined via co-immunoprecipitation (co-IP), immunofluorescence, dual luciferase reporter assay and chromatin immunoprecipitation (ChIP). The effects of miR-138-1-3p and PAK5 on HCC sorafenib resistant characteristics were investigated by a xenotransplantation model.

Results

We detected significant down-regulation of miR-138-1-3p and up-regulation of PAK5 in sorafenib-resistance HCC cell lines. Mechanistic studies revealed that miR-138-1-3p reduced the protein expression of PAK5 by directly targeting the 3′-UTR of PAK5 mRNA. In addition, we verified that PAK5 enhanced the phosphorylation and nuclear translocation of β-catenin that increased the transcriptional activity of a multidrug resistance protein ABCB1.

Conclusions

PAK5 contributed to the sorafenib resistant characteristics of HCC via β-catenin/ABCB1 signaling pathway. Our findings identified the correlation between miR-138-1-3p and PAK5 and the molecular mechanisms of PAK5-mediated sorafenib resistance in HCC, which provided a potential therapeutic target in advanced HCC patients.

System Xc-: a key regulatory target of ferroptosis in cancer

Ferroptosis is a type of oxidative stress-dependent regulated necrosis characterized by excessive lipid peroxide accumulation. This novel cell death modality has been implicated in preventing cancer progression. Cancer cells tend to modulate their redox state to prevent excessive peroxidation, eventually facilitating tumor growth. System Xc^- (a cystine/glutamate antiporter system) is a promising target in cancer cells for ferroptosis induction. The overexpression of system Xc^-, especially its core subunit xCT, has been reported in several tumors, and these high expression levels were closely related to cancer cell proliferation, invasion, metastasis and the tumor microenvironment. xCT might serve as a novel biomarker, and its upregulation almost always indicates drug tolerance and poor survival. Therefore, system Xc^- inhibition may enhance chemotherapy sensitivity and optimize patient prognosis. Here, we elaborate on the mediation of ferroptosis by suppressing system Xc^- and the relevant underlying molecular mechanism in cancer cells. The spotlight on this approach to cancer treatment is creating a new horizon and pointing to future opportunities.

Serine hydroxymethyltransferase 2: a novel target for human cancer therapy

Serine and glycine are the primary sources of one-carbon units that are vital for cell proliferation. Their abnormal metabolism is known to be associated with cancer progression. As the key enzyme of serine metabolism, Serine Hydroxymethyltransferase 2 (SHMT2) has been a research hotspot in recent years. SHMT2 is a PLP-dependent tetrameric enzyme that catalyzes the reversible transition from serine to glycine, thus promoting the production of one-carbon units that are indispensable for cell growth and regulation of the redox and epigenetic states of cells. Under a hypoxic environment, SHMT2 can be upregulated and could promote the generation of nicotinamide adenine dinucleotide phosphate (NADPH) and glutathione for maintaining the redox balance. Accumulating evidence confirmed that SHMT2 facilitates cell proliferation and tumor growth and is tightly associated with poor prognosis. In this review, we present insights into the function and research development of SHMT2 and summarize the possible molecular mechanisms of SHMT2 in promoting tumor growth, in the hope that it could provide clues to more effective clinical treatment of cancer.

System Xc-: a key regulatory target of ferroptosis in cancer

Ferroptosis is a type of oxidative stress-dependent regulated necrosis characterized by excessive lipid peroxide accumulation. This novel cell death modality has been implicated in preventing cancer progression. Cancer cells tend to modulate their redox state to prevent excessive peroxidation, eventually facilitating tumor growth. System Xc^- (a cystine/glutamate antiporter system) is a promising target in cancer cells for ferroptosis induction. The overexpression of system Xc^-, especially its core subunit xCT, has been reported in several tumors, and these high expression levels were closely related to cancer cell proliferation, invasion, metastasis and the tumor microenvironment. xCT might serve as a novel biomarker, and its upregulation almost always indicates drug tolerance and poor survival. Therefore, system Xc^- inhibition may enhance chemotherapy sensitivity and optimize patient prognosis. Here, we elaborate on the mediation of ferroptosis by suppressing system Xc^- and the relevant underlying molecular mechanism in cancer cells. The spotlight on this approach to cancer treatment is creating a new horizon and pointing to future opportunities.

N6 -methyladenosine (m6 A) RNA modification in human cancer

N⁶ -methyladenosine (m⁶ A) RNA modification, first discovered in 1974, is the most prevalent, abundant and penetrating messenger RNA (mRNA) modification in eukaryotes. This governs the fate of modified transcripts, regulates RNA metabolism and biological processes, and participates in pathogenesis of numerous human diseases, especially in cancer through the reciprocal regulation of m⁶ A methyltransferases ("writers") and demethylases ("erasers") and the binding proteins decoding m⁶ A methylation ("readers"). Accumulating evidence indicates a complicated regulation network of m⁶ A modification involving multiple m⁶ A-associated regulatory proteins whose biological functions have been further analysed. This review aimed to summarize the current knowledge on the potential significance and molecular mechanisms of m⁶ A RNA modification in the initiation and progression of cancer.

Long noncoding RNA MAPKAPK5-AS1 promotes colorectal cancer progression by cis-regulating the nearby gene MK5 and acting as a let-7f-1-3p sponge

BACKGROUND

Long noncoding RNAs (lncRNAs) are considered critical regulators in cancers; however, the clinical significance and mechanisms of MAPKAPK5-AS1 (hereinafter referred to as MK5-AS1) in colorectal cancer (CRC) remain mostly unknown.

METHODS

In this study, quantitative real-time PCR (qPCR) and western blotting were utilized to detect the levels of MK5-AS1, let-7f-1-3p and MK5 (MAPK activated protein kinase 5) in CRC tissues and cell lines. The biological functions of MK5-AS1, let-7f-1-3p and MK5 in CRC cells were explored using Cell Counting Kit-8 (CCK8), colony formation and transwell assays. The potential mechanisms of MK5-AS1 were evaluated by RNA pull-down, RNA immunoprecipitation (RIP), dual luciferase reporter assay, chromatin immunoprecipitation (ChIP) and bioinformatics analysis. The effects of MK5-AS1 and MK5 on CRC were investigated by a xenotransplantation model.

RESULTS

We confirmed that MK5-AS1 was significantly increased in CRC tissues. Knockdown of MK5-AS1 suppressed cell migration and invasion in vitro and inhibited lung metastasis in mice. Mechanistically, MK5-AS1 regulated SNAI1 expression by sponging let-7f-1-3p and cis-regulated the adjacent gene MK5. Moreover, MK5-AS1 recruited RBM4 and eIF4A1 to promote the translation of MK5. Our study verified that MK5 promoted the phosphorylation of c-Jun, which activated the transcription of SNAI1 by directly binding to its promoter.

CONCLUSIONS

MK5-AS1 cis-regulated the nearby gene MK5 and acted as a let-7f-1-3p sponge, playing a vital role in CRC tumorigenesis. This study could provide novel insights into molecular therapeutic targets of CRC.

HMGB1 regulates SNAI1 during NSCLC metastasis, both directly, through transcriptional activation, and indirectly, in a RSF1-IT2-dependent manner

High-mobility group protein B1 (HMGB1) has important functions in cancer cell proliferation and metastasis. However, the mechanisms of HMGB1 function in non-small-cell lung cancer (NSCLC) remain unclear. This study aimed to investigate the underlying mechanism of HMGB1-dependent tumor cell proliferation and NSCLC metastasis. Firstly, we found high HMGB1 expression in NSCLC and showed that HMBG1 promoted proliferation, migration, and invasion of NSCLC cells. HMGB1 could bind to SNAI1 promoter and activate the expression of SNAI1. In addition, HMGB1 could transcriptionally regulate the lncRNA RSF1-IT2. RSF1-IT2 was found to function as ceRNA, sponging miR-129-5p, which targets SNAI1. Notably, HMGB1 was also identified as a target of miR-129-5p, which indicates the establishment of a positive feedback loop. Consequently, high expression of RSF1-IT2 and SNAI1 was found to closely correlate with tumor progression in both HMGB1-overexpressing xenograft nude mice and patients with NSCLC. Taken together, our findings provide new insights into molecular mechanisms of HMGB1-dependent tumor metastasis. Components of the HMGB1-RSF1-IT2-miR-129-5p-SNAI1 pathway may have a potential as prognostic and therapeutic targets in NSCLC.

Function and evolution of RNA N6-methyladenosine modification

N6-methyladenosine (m⁶A) is identified as the most prevalent and abundant internal RNA modification, especially within eukaryotic mRNAs, which has attracted much attention in recent years since its importance for regulating gene expression and deciding cell fate. m⁶A modification is installed by RNA methyltransferases METTL3, METTL14 and WTAP (Writers), removed by the demethylases FTO and ALKBH5 (Erasers) and recognized by m⁶A binding proteins, such as YT521-B homology YTH domain-containing proteins (Readers). Accumulating evidence shows that m⁶A RNA methylation participates in almost all aspects of RNA processing, implying an association with important bioprocesses. In this review, we mainly summarize and discuss the functional relevance and importance of m⁶A modification in cellular processes.

The Emerging Role of CSN6 in Biological Behavior and Cancer Progress

BACKGROUND

The Constitutive Photomorphogenesis 9 (COP9) signalosome (CSN) subunit 6 (CSN6) noticeably acts as a regulator of the degradation of cancer-related proteins, which contributes to cancerogenesis. The aims of this paper are to expound the research advances of CSN6, particularly focusing on roles of CSN6 in the regulation of biological behavior and cancer progress.

METHODS

Literature from PubMed and Web of Science databases about biological characteristics and application of CSN6 published in recent years was collected to conduct a review.

RESULTS

CSN6, not only the non-catalytic Mpr1p and Pad1p N-terminal (MPN) subunit of CSN, but also a relatively independent protein molecule, has received great attention as a regulator of a wide range of developmental processes by taking part in the ubiquitin-proteasome system and signal transduction, as well as regulating genome integrity and DNA damage response. In addition, phosphorylation of CSN6 increases the stability of CSN6, thereby promoting its regulatory capacity. Moreover, CSN6 is overexpressed in many types of cancer compared with normal tissues and is involved in the regulation of several important intracellular pathways, consisting of cell proliferation, migration, invasion, transformation, and tumorigenesis.

CONCLUSION

We mainly present insights into the function and research development of CSN6, hoping that it can help guide the treatment of developmental defects and improve clinical care, especially in the regulation of cancer signaling pathways.

Friend or foe, the role of EGR-1 in cancer

Early growth response-1 (EGR-1), also termed NEFI-A and Krox-24, as a multi-domain protein is implicated in several vital physiological processes, including development, metabolism, cell growth and proliferation. Previous studies have implied that EGR-1 was producing in response to the tissue injury, immune response and fibrosis. Meanwhile, emerging studies stressed the pronounced correlation of EGR-1 and human cancers. Nevertheless, the intricate mechanisms of cancer-reduce EGR-1 alteration still poorly characterized. In the review, we evaluated the effects of EGR-1 in tumor cell proliferation, apoptosis, migration, invasion and tumor microenvironment, and then, we dwell on the intricate signaling pathways that EGR-1 involved in. The aberrantly expressed of EGR-1 in cancers are expected to provide a new cancer therapy strategy or a new marker for assessing treatment efficacy.

Reciprocal Role Of DNA Methylation And Sp1 Binding In Ki-67 Gene Transcription

Purpose

DNA methylation plays major regulatory roles in gene transcription. Our previous studies confirmed that Ki-67 promoter is hypomethylated and Sp1 is a transcriptional activator of Ki-67 gene in cancer cells. However, whether Sp1-mediated transcriptional activation of Ki-67 is related to its methylation has not been studied yet.

Materials and methods

In this study, we confirmed that methylated CpG binding protein 2 (MBD2) binding to methylated DNA hindered the binding of Sp1 to Ki-67 promoter and then repressed Ki-67 transcription through chromatin immunoprecipitation (ChIP) and quantitative real-time PCR (qRT-PCR). Co-immunoprecipitation (Co-IP), ChIP, methylation-specific PCR (MS-PCR) and Western blot were utilized to analyze the effects of Sp1 binding to Ki-67 promoter on its methylation status.

Results

Less DNA methyltransferase 1 (DNMT1) bound to the Ki-67 promoter in MKN45 cells than in HK-2 cells. Histone acetyltransferase p300 that was recruited by Sp1 to Ki-67 promoter could attenuate the methylation level of Ki-67 promoter. Furthermore, higher expression of Sp1 and Ki-67 was related to the overall survival (OS), first progression (FP) and post-progression survival (PPS) in gastric cancer by scrutinizing bioinformatics datasets.

Conclusion

Taken together, our findings suggested that hypomethylation of Ki-67 promoter enhanced the binding of Sp1, which in turn maintained hypomethylation of promoter, leading to increase Ki-67 expression in cancer cells. Sp1 and Ki-67 could act promising prognostic biomarkers for clinical diagnosis and treatment of cancer.

CSN6 Promotes the Migration and Invasion of Cervical Cancer Cells by Inhibiting Autophagic Degradation of Cathepsin L

CSN6 is one subunit of the highly conserved constitutive photomorphogenesis 9 (COP9) signalosome (CSN), which is overexpressed in many types of cancers, and has received great attention as a regulator of the degradation of cancer-related proteins, suggesting its importance in oncogenic activity. CSN6 has been shown to be overexpressed in cervical cancer (CC) and associated with CC development. CC remains to be one of the most aggressive cancers affecting women. Cathepsin L (CTSL), significantly associated with the autophagy, plays a critical role in degradation of extracellular matrix for metastasis. However, the detailed biological functions of CSN6 on CTSL in CC metastasis have not been well clarified. Our data has shown that CSN6 and CTSL are positively correlated. The overexpression of CSN6 and CTSL might be a strong indicator for CC enhanced aggressiveness. CSN6 could suppress the degradation of CTSL, then facilitated the migration and invasion of CC cells. Interestingly, our results indicated that autophagy is essential for decreasing CTSL, while CSN6 could inhibit the autophagy ability of CC cells. In addition, blocking of the mammalian target of rapamycin (mTOR) pathway reversed CSN6-mediated autophagy inhibition. We further demonstrated that CSN6 positively regulated CTSL expression through an autophagy-lysosomal system. Taken together, we concluded that CSN6 might promote the migration and invasion of cervical cancer cells by inhibiting autophagic degradation of CTSL and serve as a potential gene therapy target for the treatment of CC metastasis.

ACP5: Its Structure, Distribution, Regulation and Novel Functions

Background:

Tartrate-resistant acid phosphatase 5 (ACP5) is an evolutionarily conserved and multifunctional protein that is involved in generations of reactive oxygen species, normal bone development, osteoblast regulation and macrophage function, affecting a series of pathways, as well as reflecting bone resorption and osteoclast activity.

Methods:

Literature searches, systematic reviews and assessments about the structure, distribution, regulation and novel functions of ACP5 were performed in this review from PubMed and Medline databases.

Results:

Studies demonstrate that RANKL can increase the expression of ACP5 through NFATc1 and c-Fos to accelerate osteoclastogenesis, which also can be regulated by many regulators. Based on the aforementioned information, it is shown that ACP5, together with the phosphatase activity, can medicate the progression and development of human genetic diseases and cancer.

Conclusion:

As a novel target, ACP5 plays a critical role in preventing, monitoring and treating various kinds of tumors, as well as accelerating the development of a promising therapeutic strategy for human genetic diseases. However, the explicit mechanism between ACP5 and cancer is not so clear. It is necessary and significant for us to pay more in-depth attention.

PAK5 promotes the migration and invasion of cervical cancer cells by phosphorylating SATB1

p21-activated kinase 5 (PAK5) is involved in several oncogenic signaling pathways and its amplification or overexpression has been found in various types of cancer; however, the pathophysiologic role of PAK5 in cervical cancer (CC) remains elusive. This study aims to elucidate the effects of PAK5 on CC metastasis and its specific regulation mechanism. We performed western blotting and immunohistochemistry (IHC) analysis and found that the expression levels of PAK5 were significantly upregulated in CC cells and tissues. In addition, statistical analysis via IHC showed that increased PAK5 significantly correlated with CC progression. Mn²⁺-Phos-tag SDS-PAGE, western blotting, immunofluorescence and dual luciferase reporter assays were utilized to determine the involvement of SATB1 in PAK5-mediated epithelial-mesenchymal transition (EMT). We found that PAK5-mediated special AT-rich binding protein-1 (SATB1) phosphorylation on Ser47 initiated EMT cascade and promoted migration and invasion of CC cells. Furthermore, overexpression of PAK5 induced lung metastasis of CC cells in xenograft modes. Taken together, we conclude that PAK5 is a novel prognostic indicator and plays an important role in the CC metastasis.

The role of high-mobility group protein box 1 in lung cancer

High-mobility group protein box 1(HMGB1)is a ubiquitous highly conserved nuclear protein. Acting as a chromatin-binding factor, HMGB1 binds to DNA and plays an important role in stabilizing nucleosome formation, facilitating gene transcription, DNA repairing, inflammation, cell differentiation, and regulating the activity of steroid hormone receptors. Currently, HMGB1 is discovered to be related to development, progression, and targeted therapy of lung cancer, which makes it an attractive biomarker, and therapeutic target. This review aims to encapsulate the relationship between HMGB1 and lung cancer, suggesting that HMGB1 plays a pivotal role in initiation, development, invasion, metastasis, and prognosis of lung cancer.

Suppression of Jab1 expression inhibits proliferation and promotes apoptosis of AMC-HN-8 cells

c-Jun activation domain-binding protein-1 (Jab1) is a multifunctional protein involved in cell proliferation and apoptosis, DNA damage and repair and genome stability. In a number of types of human carcinoma, the abnormal expression of Jab1 is associated with poor prognosis, suggesting that Jab1 serves a vital function in tumorigenesis. However, the functional effects and the underlying molecular mechanisms of Jab1 in laryngeal squamous cell carcinoma (LSCC) progression remain poorly understood. The results of the present study demonstrate that downregulating Jab1 expression promotes LSCC apoptosis while inhibiting the proliferation of LSCC cells. Furthermore, Jab1 inhibition results in decreased protein kinase B phosphorylation accompanied by increased caspase-3 cleavage and p53 expression. It has been identified that the increased expression of Jab1 is markedly associated with LSCC progression, therefore Jab1 may be used as a novel target for the treatment of laryngeal cancer.

PAK5-mediated phosphorylation and nuclear translocation of NF-κB-p65 promotes breast cancer cell proliferation in vitro and in vivo

Background

Abnormal proliferation is significantly associated with the promotion of malignant tumor. Growing evidence suggest that the signal pathways of p21^cdc42/rac1-activated kinase 5 (PAK5) have been found in various tumor progression, however, the role of PAK5 in breast cancer remains largely unclear.

Methods

We evaluated PAK5 and p65 staining in breast cancer tissues (BCTs) and paired non-cancerous tissues (NTs) using tissue microarray (TMA) technology. The functions of PAK5 were studied in vitro and in vivo. Cell Counting Kit-8 (CCK-8) and flow cytometry were performed to determine proliferation of breast cancer cells. Phosphorylation assay and co-immunoprecipitation (co-IP) were employed to identify the regulation mechanism of p65 by PAK5. The activation of Cyclin D1 promoter was measured with luciferase reporter assay. Xenograft models in nude mice were established to explore the roles of PAK5 in breast cancer growth.

Results

In this study, we show that PAK5 is highly expressed in breast cancer tissues and the increased PAK5 is significantly associated with breast cancer progression. Overexpression of PAK5 promotes the proliferation and cell-cycle progression by increasing the expression of Cyclin D1 in vitro and in vivo. Mechanistic studies demonstrated that PAK5 can promote the phosphorylation and the nuclear translocation of p65 subunit of nuclear factor-kappaB (NF-κB). Furthermore, p65 can directly bind to the promoter of Cyclin D1 and mediate an increase in its protein expression.

Conclusions

Taken together, our findings suggest that PAK5 may serve as a potential prognosis marker and therapeutic target for human breast cancer.

Egr-1 suppresses breast cancer cells proliferation by arresting cell cycle progression via down-regulating CyclinDs

Egr-1 is an important nuclear transcription factor in the early growth response gene family (Egr family). Egr-1 was reportedly involved in the tumorigenesis of diverse tumors. However, there was a paucity of data regarding the role of Egr-1 in the breast cancer. Herein, we investigated the expression of Egr-1 in breast tissues and breast cancer cell lines BT549 and Bcap37. Immunohistochemistry showed that Egr-1 was down-regulated in breast cancer tissues versus the normal paracancerous tissues. Overexpression of Egr-1 could arrest the progression of cell cycle in breast cancer cells. Luciferase reporter assay revealed Egr-1 could bind to the promoters of CyclinD1, CyclinD2 and CyclinD3. Together, these results suggested that Egr-1 could affect the cell cycle of breast cancer cells and defined the mechanism for the cells by inhibiting the process of G0/G1 phase. Our findings provide new insight into Egr-1 in breast cancer.

The Role of Tumor Suppressor DLC-1: Far From Clear

BACKGROUND

Deleted in liver cancer 1 (DLC-1) In human was originally isolated from rats brain and was often found to be deleted in hepatocellular carcinoma (HCC).

METHODS

We undertook a structured search of bibliographic databases for peer-reviewed research literature using a focused review question and inclusion/exclusion criteria.

RESULTS

Subsequent studies have demonstrated that DLC-1 is generally expressed in normal human tissues as well as in rats, while it always exists inactivated or even lost in many human cancers, which characterizes DLC-1 as a potential tumor suppressor. Additionally, the RhoGAP (Rho-GTPase activating proteins) activity was found to play a pivotal role in regulating DLC-1.

CONCLUSION

Although emerging studies in a variety of cancers have identified DLC-1 and its downstream signaling molecules as potential therapeutic targets for treatments of DLC-1-related cancers, the mechanisms linked to DLC-1 remain undefined.

MicroRNA-9 inhibits the gastric cancer cell proliferation by targeting TNFAIP8

BACKGROUND AND OBJECTIVES

MicroRNA-9 is frequently dysregulated in many human carcinoma types, including gastric cancer (GC). Previous studies demonstrated that the expression of TNFAIP8 in GC is correlated with tumour occurrence, development, invasion, metastasis and prognosis. However, till now, the relationship between MicroRNA-9 and TNFAIP8 in GC has not been reported.

MATERIALS AND METHODS

Levels of miR-9 and TNFAIP8 expression in GC tissues and in human GC cell lines were studied using qualitative real-time PCR (qRT-PCR) and Western blotting. Cell viability was detected using the CCK-8 and clone formation assays. A dual-luciferase reporter system was used to confirm the target gene of miR-9.

RESULTS

We found that the expression level of MicroRNA-9 in GC tissues and cell lines was significantly lower than that in adjacent non-cancerous tissues and human immortalized gastric epithelial cell (GES) line, respectively. In addition, overexpression of MicroRNA-9 markedly inhibited GC cell proliferation in vitro and tumour growth in vivo. Further experiments revealed that TNFAIP8 was a direct and functional target of MicroRNA-9 in GC and overexpression of MicroRNA-9 obviously down-regulated the expression of TNFAIP8, which was involved in the gastric carcinogenesis and cancer progression.

CONCLUSION

Our results suggested that MicroRNA-9-TNFAIP8 might represent a promising diagnostic biomarker for GC patients and could be a potential therapeutic target in the prevention and treatment of GC.

RPA1 expression in esophageal carcinoma and its influence on radiosensitivity of esophageal carcinoma TE-1 cells

AIM

To determinate the RPA1 expression in esophageal carcinoma and the paired tumor-adjacent tissue, and to explore the influence of RPA1 on radiosensitivity of esophageal carcinoma TE-1 cells.

METHODS

Firstly, the RPA1 expression of 40 cases esophageal carcinoma and their adjacent tissues were detected by immunohistochemistry. Secondly, The esophageal carcinoma cell subline-radiation resistance model (TE-1R) was constructed by radiation-induction, the RPA1 expression and proliferation activity of TE-1 and TE-1R cells were detected by Western blot and MTT assay respectively. After radiation, the expression of RPA1 and cell apoptosis were detected by Western blot and FACS respectively. Cell clone formation and survival rate were detected by clonogenic assay. Thirdly, Inhibiting RPA1 expression by siRNA in TE-1 cells, the expression of RPA1 was detected by RT-PCR and Western blot, Cell proliferation inhibition ratio and cell apoptosis after radiation were detected by MTT assay and FACS respectively.

RESULTS

The RPA1 expression in esophageal carcinoma was significantly higher than that in the tumor-adjacent tissues, which was associated with tumor invasion and lymph node metastasis. The RPA1 expression in TE-1R cells was higher than that in TE-1 cells, while the proliferation activity of TE-1R cells was lower than that of TE-1 cells, and the apoptosis rate of TE-1R cells after radiation was less than that of TE-1 cells. In addtion, the clone formation and survival rate of TE-1R cells were higher than that of TE-1 cells. Moreover, inhibiting RPA1 expression by siRNA-RPA1 could promoted proliferation inhibition ratio and apoptosis rate of TE-1 cells after radiation.

CONCLUSION

The over-expression of RPA1 in esophageal carcinoma was related with progression and metastasis. Moreover, radiation induced the excessive expression RPA1 in TE-1 cells, and the radiosensitivity of TE-1R cells was less than that of TE-1 cells. Furthermore, inhibiting RPA1 expression could increase radiosensitivity of TE-1 cells. Overall, RPA1 could influence radiosensitivity and might be one important mechanism of radiation resistance in TE-1 cells.

FK506-binding protein 5 inhibits proliferation and stimulates apoptosis of glioma cells

INTRODUCTION

FK506-binding protein 5 (FKBP5) is reported to act as a scaffolding protein for Akt to promote the dephosphorylation of AKT Ser473 and suppress pancreatic cancer growth. However, other studies have shown that FKBP5 promotes tumor growth and chemoresistance through regulating NF-κB signaling in other cancers. In this study, we attempted to investigate the role and mechanism of action of FKBP5 in the regulation of proliferation and apoptosis of glioma cells.

MATERIAL AND METHODS

The glioma U251 cell line was used as the model. Cell proliferation was detected by MTT assay. Cell apoptosis was detected by annexin-V staining. Protein expression was detected by Western blot analysis.

RESULTS

FKBP5 overexpression inhibited the proliferation of U251 cells significantly (p < 0.05), and promoted the apoptosis of U251 cells significantly (p < 0.05). In addition, FKBP5 overexpression inhibited the phosphorylation of Akt at Ser743, decreased the level of Bcl-2, increased the level of Bax, and enhanced the cleavage of caspase-9 and caspase-3 (p < 0.05 compared to control). In contrast, FKBP5 knockdown enhanced the proliferation of U251 cells, increased the phosphorylation of Akt significantly (p < 0.05), increased the expression of Bcl-2 and decreased the expression of Bax, and decreased the cleavage of caspase-9 and caspase-3 significantly (p < 0.05).

CONCLUSIONS

FKBP5 plays the role of a tumor suppressor in glioma by inhibiting the activation of Akt and stimulating the intrinsic mitochondrial apoptotic pathway, and could be used as a new target for gene therapy of glioma.

p42.3: An abductor of cell cycle

As a newly discovered tumor-associated gene, p42.3 was originally ascertained in gastric cancer cell line BGC823 and has been confirmed as a cell cycle-dependent gene that is overexpressed in many human tumor cell lines and embryonic tissues. p42.3 can regulate the level of relevant cycle-dependent proteins and promote malignant transformation of cells. A variety of cellular functions, including cell proliferation, cell invasion and cell migration, are under control of p42.3. Our review, namely the introduction of the structure of p42.3, underlying activity regulation mechanisms of p42.3 as well as the role p42.3 plays in malignant cellular transformation process, are accompanied by the presentation of potential directions of further researches of cancer prevention and therapy in which p42.3 is inevitable.

A sphingosine kinase-1 inhibitor, SKI-II, induces growth inhibition and apoptosis in human gastric cancer cells

SKI-II has been reported as an inhibitor of sphingosine kinase 1 and has been extensively used to prove the involvement of sphingosine kinase and sphingosine-1-phosphate (Sphk1) in cellular processes. In the current study, we investigated the effects of SKI-II and its potential mechanisms in human gastric cancer SGC7901 cells. After treatment with SKI-II, cell growth, cell cycle distribution, apoptosis, expression of Sphk1, NF-κB, Bcl-2, Bax and p27 were assessed by MTT assay, flow cytometry, electron microscopy, immunocytochemistry and Western-blot assay, respectively. Our results showed that SKI-II markedly inhibited SGC7901 cell survival in a dose-dependent manner, reduced cell proliferation with accumulation of cells in the G0/G1 phase and induced apoptosis in the tumor cells. Furthermore, Western blotting and immunocytochemistry showed that the expression of p27 and Bax was increased significantly, but the expression of NF-κB, Bcl-2 and Sphk1 decreased by different degrees. These results indicate that SKI-II induced cell growth arrest and apoptosis. The increased apoptotic sensitivity of SGC7901 was correlated with NF-κB or Bcl-2/Bax activation.

PLCε signaling in cancer

PURPOSE

As one of the members of the PLC family, the phosphoinositide-specific phospholipase Cε (PLCε) has been shown to play pivotal roles in multiple signal pathways and control a variety of cellular functions. A number of studies have shown that aberrant regulation of PLCε was involved in various types of animal and human cancer. However, the role of PLCε in cancer remains elusive. In this review, we provide an overview of the PLCε, especially its roles in multiple signal pathways, and summarize the recent findings that highlight the roles of PLCε in carcinogenesis and cancer progression, making an avenue to provide a novel therapeutic strategy for the treatment of cancer.

METHODS

A literature search mainly paying attention to the network of PLCε involved in tumorigenesis and development was performed in electronic databases.

RESULTS

PLCε plays a key role in medicating the development and progression of human cancers with highest potency to be a target of cancer prevention and treatment.

Gamma-aminobutyric acid induces tumor cells apoptosis via GABABR1·β-arrestins·JNKs signaling module

Gamma-aminobutyric acid (GABA), an inhibitory neurotransmitter in central nervous system, has yet been found to widely exist in tumor tissues to regulate tumor cells growth. However, the function of GABA on inducing tumor cells apoptosis and the potential mechanism are still unclear. In order to detect whether GABA via GABAB receptor GABABR1 would activate c-Jun N-terminal kinases (JNKs) to promote tumor cells apoptosis, co-immunoprecipitation assay was used to investigate the association of β-arrestins with GABABR1 and JNKs in the different four cancer cell lines. Our observation demonstrated that β-arrestins, in addition to their role in G protein-coupled receptors desensitization, had an additional function as adapter proteins to recruit JNKs to GABABR1, thereby conferring distinct enzymatic activities upon the receptor, which may trigger JNKs signal pathway involved in the regulation of cellular growth. Activated JNKs subsequently phosphorylated downstream c-Jun to transcribe a wide variety of pro-apoptotic genes. Additionally, GABA up-regulated the ratio of pro-apoptotic protein Bax to anti-apoptotic protein Bcl-2, and thus facilitated caspase-3 cleavage, leading to tumor cells apoptosis in a mitochondrial-dependent pathway. In contrast, GABABR antagonist CGP35348 reversed GABA-induced JNKs phosphorylation and its downstream proteins activation, which consequently restrained tumor cells apoptosis. Taken together, our study suggested that GABA via its receptor GABABR1 recruited β-arrestins to facilitate the activation of JNKs cascade, resulting in tumor cells growth inhibition.

Rap2a is a novel target gene of p53 and regulates cancer cell migration and invasion

The p53 transcription factor is a critical regulator of the cell cycle, DNA repair, and apoptosis. Recent evidences suggest that p53 may contribute to the regulation of cell invasion and migration. Rap2a, a member of the small GTPase superfamily, mediates diverse cellular events such as cell adhesion, migration and proliferation through various signaling pathways. In this study, we identify that Rap2a is a novel target of p53 and is induced upon DNA damage in a p53-dependent manner. Upon DNA damage, p53 directly binds to the promoter of Rap2a and activates its transcription. We show that Rap2a is significantly upregulated in many types of tumors. In addition, the ectopic expression of Rap2a enhances the migration and invasive ability of cancer cells and increases activities of matrix metalloproteinase MMP2 and MMP9. In contrast, the inactivation of Rap2a inhibits cell invasion and activities of MMP2 and MMP9. We also show that Rap2a regulates the phosphorylation level of Akt. Collectively, our results show that ectopic expression of Rap2a has a key role in enhancing migration, invasion and metastasis by upregulating p-Akt.

p42.3 promotes cell proliferation and invasion in human Renal-Cell Carcinoma

p42.3 is a tumor-specific gene and found to be over-expressed in many tumor cell lines and primary tumor tissues. It plays a significant role in neoplastic transformation and tumor progression. To date, the association between p42.3 and Renal-Cell Carcinoma (RCC) has not been reported. This study investigated the biological effects and mechanisms of p42.3 in RCC progression. In this study, we found that p42.3 is overexpressed in various kinds of RCC cells, and knockdown of p42.3 dramatically reduced cell proliferation and invasion in vitro. Our studies revealed that overexpression of p42.3 accelerates the epithelial-mesenchymal transition (EMT) progression and induces RCC cells proliferation and invasion. Further studies show that p42.3 may involve in activation of β-catenin and participate in RCC cell invasion. Combined, these data indicate that p42.3 contributes to promoting RCC cells proliferation and invasion through accelerates the EMT progression and β-catenin activation.

Ubiquitination of p53 is involved in troglitazone induced apoptosis in cervical cancer cells

Peroxisome proliferator-activated receptor gamma (PPAR-γ), a ligand-dependent nuclear transcription factor, has been found to widely exist in tumor tissues and plays an important role in affecting tumor cell growth. In this study, we investigated the effect of PPAR-γ on aspects of the cervical cancer malignant phenotype, such as cell proliferation and apoptosis. Cell growth assay, Western blotting, Annexin V and flow cytometry analysis consistently showed that treatment with troglitazone (TGZ, a PPAR-γ agonist) led to dose-dependent inhibition of cervical cancer cell growth through apoptosis, whereas T0070907 (another PPAR-γ antagonist???) had no effect on Hela cell proliferation and apoptosis. Furthermore, we also detected the protein expression of p53, p21 and Mdm2 to explain the underlying mechanism of PPAR-γ on cellular apoptosis. Our work, finally, demonstrated the existence of the TGZ-PPAR-γ-p53 signaling pathway to be a critical regulator of cell apoptosis. These results suggested that PPAR-γ may be a potential therapeutic target for cervical cancer.

Melanoma differentiation associated gene-7/interleukin-24 induces caspase-3 denitrosylation to facilitate the activation of cancer cell apoptosis

Melanoma differentiation-associated gene-7 (mda-7)/interleukin-24 (IL-24) induces caspase-3 cleavage and subsequent activation via the intrinsic or extrinsic pathway to result in cancer cell-selective apoptosis, but whether mda-7/IL-24 may directly regulate caspase-3 through the post-translational modification remains unknown. Here, we reported that tumor-selective replicating adenovirus ZD55-IL-24 led to caspase-3 denitrosylation and subsequent activation, indicating that caspase-3 denitrosylation played a crucial role in ZD55-IL-24-induced cancer cell apoptosis. To confirm the relationship between caspase-3 denitrosylation and its activation in response to ZD55-IL-24, we treated carcinoma cells with the different nitric oxide (NO) regulators to modulate caspase-3 denitrosylation level, then observed the corresponding caspase-3 cleavage. We found that NO inhibitor 2-(4-carboxyphenyl)-4,4,5,5-tetramethylimidazoline-1-oxy-3-oxide (PTIO) promoted caspase-3 denitrosylation and caspase-3 cleavage, thereby exacerbating ZD55-IL-24-induced cancer cell apoptosis, whereas NO donor sodium nitroprusside (SNP) showed the opposite effect. Moreover, caspase-3 denitrosylation facilitated its downstream target poly ADP-ribose polymerase (PARP) degradation that further increased the apoptotic susceptibility. Although caspase-3 activation controlled by denitrosylation modification has emerged as an important regulator of programmed cell death, the detailed molecular mechanism by which caspase-3 exerts its denitrosylation modification in response to ZD55-IL-24 still needs to be elucidated. Thus, our results demonstrated that ZD55-IL-24 increased Fas expression to enhance thioredoxin reductase 2 (TrxR2), which was responsible for caspase-3 denitrosylation. Collectively, these findings elucidate that ZD55-IL-24 induces caspase-3 denitrosylation through Fas-mediated TrxR2 enhancement, thereby facilitating caspase-3 cleavage and the downstream caspase signaling pathway activation, which provides a novel insight into ZD55-IL-24-induced cancer-specific apoptosis by post-translational modification of the apoptotic executor caspase-3.

An oncogenic kinase: putting PAK5 forward

INTRODUCTION

Overexpression of p21-activated kinase 5 (PAK5) is discovered in many tumors, probably due to its regulation in cytoskeleton, antiapoptosis and proliferation. A better understanding of the modulation mechanisms of PAK5 is needed for the development of tumor treatment where current therapeutics is inadequate.

AREAS COVERED

This review discusses the current understanding of PAK5 functions as an oncogenic kinase in tumor cellular regulation. Mechanisms of action and molecular pathways involved in cytoskeleton regulation, antiapoptosis and proliferation of tumors are discussed.

EXPERT OPINION

PAKs are serine/threonine kinases and downstream effectors for Cdc42 and Rac, the subfamilies of Rho small GTPases. PAK5 shares sequence identities in p21-GTPase-binding domain and kinase domain and is completely different in other regions compared with other PAKs. Overexpression of PAK5 has been found in several tumors, probably due to its contribution to proliferation, cytoskeleton and anti-apoptosis. Additional regulation mechanisms which are independent of Rho GTPases also indicate that PAK5 functions as a special signal molecule in cellular signaling pathways of tumor progression.

P53/microRNA-34-induced metabolic regulation: new opportunities in anticancer therapy

MicroRNA-34 (miR-34) is directly regulated by p53, and its potential tumor suppressive roles have been studied extensively. As a p53-induced microRNA, miR-34 functions as a tumor suppressor by playing a role in cell cycle arrest, apoptosis and metabolic regulation. Among these p53/miR-34 associated processes, apoptosis and cell cycle arrest are known as essential for p53/miR-34-mediated tumor suppression. P53-mediated metabolic processes have been shown to play pivotal roles in cancer cell biology. Recent studies have also identified several miR-34 targets involved in p53/miR-34-induced metabolic regulation. However, correlations among these metabolic targets remain to be fully elucidated. In this review, we summarize the current progress in the field of metabolic regulation by the p53/miR-34 axis and propose future directions for the development of metabolic approaches in anticancer therapy.

Tyrosine phosphorylation of β-catenin affects its subcellular localization and transcriptional activity of β-catenin in Hela and Bcap-37 cells

In order to investigate the relationship between tyrosine phosphorylation of β-catenin and transcriptional activity of β-catenin in Hela and Bcap-37 cells, genistein (a tyrosine kinase inhibitor) was used to inhibit tyrosine phosphorylation in cells. Our results showed the total β-catenin protein levels were mainly equal in Hela, Bcap-37 and HK-2 cells, β-catenin was mainly present in nucleus in Hela and Bcap-37cells, while in HK-2 cell β-catenin was mainly located in cytoplasm. Genistein could inhibit tyrosine phosphorylation of β-catenin and downregulate nuclear β-catenin expression in Hela and Bcap-37 cells. In addition, genistein suppressed Ki-67 promoter activity and Ki-67 protein level, thus promoted cell apoptosis. Furthermore, β-catenin could increase the Ki-67 promoter activity in Hela and Bcap-37 cells. From these findings we conclude that tyrosine phosphorylation of β-catenin can regulate the cellular distribution of β-catenin and affect the transcriptional activity of β-catenin.

β-arrestin promotes c-Jun N-terminal kinase mediated apoptosis via a GABA(B)R·β-arrestin·JNK signaling module

Evidence is growing that the GABAB receptor, which belongs to the G protein-coupled receptor (GPCR) superfamily, is involved in tumorigenesis. Recent studies have shown that β-arrestin can serve as a scaffold to recruit signaling protein c-Jun N-terminal knase (JNK) to GPCR. Here we investigated whether β-arrestin recruits JNK to the GABAB receptor and facilitates its activation to affect the growth of cancer cells. Our results showed that β-arrestin expression is decreased in breast cancer cells in comparison with controls. β-arrestin could enhance interactions of the GABABR·β-arrestin·JNK signaling module in MCF-7 and T-47D cells. Further studies revealed that increased expression of β-arrestin enhances the phosphorylation of JNK and induces cancer cells apoptosis. Collectively, these results indicate that β-arrestin promotes JNK mediated apoptosis via a GABABR·β-arrestin·JNK signaling module.