TRIM68 regulates ligand-dependent transcription of androgen receptor in prostate cancer cells

Regulating Androgen Receptor Function in Prostate Cancer: Exploring the Diversity of Post-Translational Modifications

Androgen receptor (AR) transcriptional activity significantly influences prostate cancer (PCa) progression. In addition to ligand stimulation, AR transcriptional activity is also influenced by a variety of post-translational modifications (PTMs). A number of oncogenes and tumor suppressors have been observed leveraging PTMs to influence AR activity. Subjectively targeting these post-translational modifiers based on their impact on PCa cell proliferation is a rapidly developing area of research. This review elucidates the modifiers, contextualizes the effects of these PTMs on AR activity, and connects these cellular interactions to the progression of PCa.

RNA N6-methyladenosine-modified-binding protein YTHDF1 promotes prostate cancer progression by regulating androgen function-related gene TRIM68

PURPOSE

There is no report about the direct relationship between m6A modification and androgen receptor (AR)-related genes in prostate cancer (PC). We aimed to study the mechanisms of m6A methylation in regulating the pathogenesis of PC from the perspective of AR-related genes.

METHODS

qRT-PCR was applied to detect the expression of m6A-related genes in PC cell with or without AR inhibitor. The effects of YTHDF1 knockdown on PC cell viability, apoptosis, migration and invasion were investigated using flow cytometry, wound healing and transwell assays, respectively. The mechanism of YTHDF1 action was investigated using m6A RNA immunoprecipitation (MeRIP) sequencing. The biological functions of YTHDF1 were also explored through in vivo experiments.

RESULTS

YTHDF1 was significantly down-regulated in AR inhibitor group. YTHDF1 knockdown significantly decreased AR level, viability and m6A methylation level of PC cells. TRIM68 was identified as a direct target of YTHDF1. Both YTHDF1 and TRIM68 knockdown increased apoptosis, and decreased cell viability, migration, and invasion of PC cells, while TRIM68 overexpression reversed the effects of YTHDF1 knockdown on PC cells. In addition, knockdown of YTHDF1 or TRIM68 significantly decreased the m6A methylation level, and mRNA and protein levels of YTHDF1, TRIM68 and AR in PC cells, while TRIM68 overexpression increased the expression levels above. Furthermore, subcutaneous xenografts of nude mice also revealed that TRIM68 could reverse the effects of YTHDF1 knockdown in PC in vivo.

CONCLUSION

This study suggested the key role of YTHDF1-mediated m6A modification in PC progression by regulating androgen function-related gene TRIM68 in PC.

Tripartite motif-containing 68-stabilized modulator of apoptosis-1 retards the proliferation and metastasis of lung cancer

Non-small cell lung cancer (NSCLC) is a major global health threat with high incidence and mortality. Modulator of apoptosis-1 (MOAP1), also named MAP-1, belongs to the PNMA gene family and plays a key role in regulating apoptosis and tumor growth. However, its influences on NSCLC are largely unclear, and thus were explored in our present study, particularly the underlying mechanisms. Here, we initially find that MOAP1 expression is significantly decreased in NSCLC patients compared with the normal ones, and negatively correlated with the TNM and pathologic stages among patients. Additionally, MOAP1 low expression predicts a poorer prognosis than that of the NSCLC patients expressing higher MOAP1. Our in vitro studies confirm much lower MOAP1 expression in NSCLC cell lines. Of note, promoting MOAP1 expression strongly reduces the proliferation and induces apoptosis in NSCLC cells, accompanied with cell cycle arrest distributed in G0/G1 phase. Moreover, we find that MOAP1 has a negative correlation with Th2 cells' infiltration, but a positive correlation with the infiltration levels of eosinophils. Epithelial mesenchymal transition (EMT) process is also greatly restrained in NSCLC cells with MOAP1 over-expression, as proved by the reduced migration and invasion of cells. We further identify a positive correlation between MOAP1 and tripartite motif-containing 68 (TRIM68) in patients with NSCLC. Further analysis shows that TRIM68 directly interacts with MOAP1 and stabilizes MOAP1. Importantly, TRIM68 can activate MOAP1 by inducing the K63-linked polyubiquitination of MOAP1. Finally, animal studies verify that promoting MOAP1 efficiently suppresses tumor growth and lung metastasis in the nude mice. Collectively, our results reveal a novel mechanism through which MOAP1 stabilized by TRIM68 inhibits NSCLC development and targeting MOAP1 for its up-regulation may be a promising therapeutic strategy for NSCLC treatment.

TRIM proteins in breast cancer: Function and mechanism

Breast cancer is the most prevalent malignancy in the world, and despite tremendous progress in current treatment strategies, recurrence, metastasis and drug resistance of breast cancer remain the major causes of death in patients. Tripartite motif (TRIM) family proteins play a critical role in the tumor progression such as cell proliferation, migration, invasion, and metastasis. Accumulating evidence suggests that the TRIM protein family serve as cancer suppressor proteins or oncoproteins in breast cancer. This review focused on the roles and molecular mechanisms of TRIM protein in breast cancer. Importantly, it provides new insights that TRIM proteins may be ideal targets to treat breast cancer.

The androgen receptor-targeted proteolysis targeting chimera and other alternative therapeutic choices in overcoming the resistance to androgen deprivation treatment in prostate cancer

Androgen receptor (AR) plays a vital role in prostate cancer (PCa), including castration-resistant PCa, by retaining AR signalling. Androgen deprivation treatment (ADT) has been the standard treatment in the past decades. A great number of AR antagonists initially had been found effective in tumour remission; however, most PCa relapsed that caused by pre-translational resistance such as AR mutations to turn antagonist into agonist, and AR variants to bypass the androgen binding. Recently, several alternative therapeutic choices have been proposed. Among them, proteolysis targeting chimera (PROTAC) acts different from traditional drugs that usually function as inhibitors or antagonists, and it degrades oncogenic protein and does not disrupt the transcription of an oncogene. This review first discussed some essential mechanisms of ADT resistance, and then introduced the application of AR-targeted PROTAC in PCa cells, as well as other AR-targeted therapeutic choices.

The roles and targeting options of TRIM family proteins in tumor

Tripartite motif (TRIM) containing proteins are a class of E3 ubiquitin ligases, which are critically implicated in the occurrence and development of tumors. They can function through regulating various aspects of tumors, such as tumor proliferation, metastasis, apoptosis and the development of drug resistance during tumor therapy. Some members of TRIM family proteins can mediate protein ubiquitination and chromosome translocation via modulating several signaling pathways, like p53, NF-κB, AKT, MAPK, Wnt/β-catenin and other molecular regulatory mechanisms. The multi-domain nature/multi-functional biological role of TRIMs implies that blocking just one function or one domain might not be sufficient to obtain the desired therapeutic outcome, therefore, a detailed and systematic understanding of the biological functions of the individual domains of TRIMs is required. This review mainly described their roles and underlying mechanisms in tumorigenesis and progression, and it might shade light on a potential targeting strategy for TRIMs in tumor treatment, especially using PROTACs.

Genetic and serum markers in adult degenerative scoliosis: a literature review

STUDY DESIGN

Literature review.

OBJECTIVE

Adult degenerative scoliosis (ADS) is becoming a more prevalent diagnosis with an increasing elderly population. Our objective is to provide a literature review of genetic and serum markers in ADS.

METHODS

A literature review was conducted in the various databases from their inception to July 2020. Studies that reviewed any genetic or serum markers of ADS whether in detection or progression were selected. Studies that reviewed congenital scoliosis or adolescent idiopathic scoliosis (AIS) were excluded.

RESULTS

A total of 1447 titles were identified of which 14 were included in the final review. Two papers reported on serum markers pertaining to serum cartilage metabolites and pentosidine. Twelve studies reported on genetic markers including gene polymorphisms in estrogen receptors, parathyroid hormone receptors, interleukin 6, cyclooxygenase-2 (COX-2), COL2A1, GPRIN1, TRAIL, GRIN receptor, RIMS, LBX1 as well as copy number variations.

CONCLUSIONS

Serum markers of osteoarthritis and sarcopenia have been found to be significantly elevated in ADS patients as well. Numerous polymorphisms have been found in a variety of genes playing key roles in bone formation and regulation. Further research is needed in validating previous studies as well as identifying other biomarkers for patients at risk for developing ADS.

Construction and evaluation of a nomogram for predicting survival in patients with lung cancer

BACKGROUND

Lung cancer is a heterogeneous disease with a severe disease burden. Because the prognosis of patients with lung cancer varies, it is critical to identify effective biomarkers for prognosis prediction.

METHODS

A total of 2325 lung cancer patients were integrated into four independent sets (training set, validation set I, II and III) after removing batch effects in our study. We applied the microarray data algorithm to screen the differentially expressed genes in the training set. The most robust markers for prognosis were identified using the LASSO-Cox regression model, which was then used to create a Cox model and nomogram.

RESULTS

Through LASSO and multivariate Cox regression analysis, eight genes were identified as prognosis-associated hub genes, followed by the creation of prognosis-associated risk scores (PRS). The results of the Kaplan-Meier analysis in the three validation sets demonstrate the good predictive performance of PRS, with hazard ratios of 2.38 (95% confidence interval (CI), 1.61-3.53) in the validation set I, 1.35 (95% CI, 1.06-1.71) in the validation set II, and 2.71 (95% CI, 1.77-4.18) in the validation set III. Additionally, the PRS demonstrated superior survival prediction in subgroups by age, gender, p-stage, and histologic type (p < 0.0001). The complex model integrating PRS and clinical risk factors also have a good predictive performance for 3-year overall survival.

CONCLUSIONS

In this study, we developed a PRS signature to help predict the survival of lung cancer. By combining it with clinical risk factors, a nomogram was established to quantify the individual risk assessments.

Proteomic analysis of lung cancer cells reveals a critical role of BCAT1 in cancer cell metastasis

Metastasis is the major cause of high mortality in lung cancer. Exploring the underlying mechanisms of metastasis thus holds promise for identifying new therapeutic strategies that may enhance survival. Methods: We applied quantitative mass spectrometry to compare protein expression profiles between primary and metastatic lung cancer cells whilst investigating metastasis-related molecular features. Results: We discovered that BCAT1, the key enzyme in branched-chain amino acid metabolism, is overexpressed at the protein level in metastatic lung cancer cells, as well as in metastatic tissues from lung cancer patients. Analysis of transcriptomic data available in the TCGA database revealed that increased BCAT1 transcription is associated with poor overall survival of lung cancer patients. In accord with a critical role in metastasis, shRNA-mediated knockdown of BCAT1 expression reduced migration of metastatic cells in vitro and the metastasis of these cells to distal organs in nude mice. Mechanistically, high levels of BCAT1 depleted α-ketoglutarate (α-KG) and promoted expression of SOX2, a transcription factor regulating cancer cell stemness and metastasis. Conclusion: Our findings suggest that BCAT1 plays an important role in promoting lung cancer cell metastasis, and may define a novel pathway to target as an anti-metastatic therapy.

TRIMming Down Hormone-Driven Cancers: The Biological Impact of TRIM Proteins on Tumor Development, Progression and Prognostication

The tripartite motif (TRIM) protein family is attracting increasing interest in oncology. As a protein family based on structure rather than function, a plethora of biological activities are described for TRIM proteins, which are implicated in multiple diseases including cancer. With hormone-driven cancers being among the leading causes of cancer-related death, TRIM proteins have been described to portrait tumor suppressive or oncogenic activities in these tumor types. This review describes the biological impact of TRIM proteins in relation to hormone receptor biology, as well as hormone-independent mechanisms that contribute to tumor cell biology in prostate, breast, ovarian and endometrial cancer. Furthermore, we point out common functions of TRIM proteins throughout the group of hormone-driven cancers. An improved understanding of the biological impact of TRIM proteins in cancer may pave the way for improved prognostication and novel therapeutics, ultimately improving cancer care for patients with hormone-driven cancers.

The translational values of TRIM family in pan-cancers: From functions and mechanisms to clinics

Cancer is the second leading cause of human death across the world. Tripartite motif (TRIM) family, with E3 ubiquitin ligase activities in majority of its members, is reported to be involved in multiple cellular processes and signaling pathways. TRIM proteins have critical effects in the regulation of biological behaviors of cancer cells. Here, we discussed the current understanding of the molecular mechanism of TRIM proteins regulation of cancer cells. We also comprehensively reviewed published studies on TRIM family members as oncogenes or tumor suppressors in the oncogenesis, development, and progression of a variety of types of human cancers. Finally, we highlighted that certain TRIM family members are potential molecular biomarkers for cancer diagnosis and prognosis, and potential therapeutic targets.

TRIM68, PIKFYVE, and DYNLL2: The Possible Novel Autophagy- and Immunity-Associated Gene Biomarkers for Osteosarcoma Prognosis

Introduction

Osteosarcoma is among the most common orthopedic neoplasms, and currently, there are no adequate biomarkers to predict its prognosis. Therefore, the present study was aimed to identify the prognostic biomarkers for autophagy-and immune-related osteosarcoma using bioinformatics tools for guiding the clinical diagnosis and treatment of this disease.

Materials and Methods

The gene expression and clinical information data were downloaded from the Public database. The genes associated with autophagy were extracted, followed by the development of a logistic regression model for predicting the prognosis of osteosarcoma using univariate and multivariate COX regression analysis and LASSO regression analysis. The accuracy of the constructed model was verified through the ROC curves, calibration plots, and Nomogram plots. Next, immune cell typing was performed using CIBERSORT to analyze the expression of the immune cells in each sample. For the results obtained from the analysis, we used qRT-PCR validation in two strains of human osteosarcoma cells.

Results

The screening process identified a total of three genes that fulfilled all the screening criteria. The survival curves of the constructed prognostic model revealed that patients with the high risk presented significantly lower survival than the patients with low risk. Finally, the immune cell component analysis revealed that all three genes were significantly associated with the immune cells. The expressions of TRIM68, PIKFYVE, and DYNLL2 were higher in the osteosarcoma cells compared to the control cells. Finally, we used human pathological tissue sections to validate the expression of the genes modeled in osteosarcoma and paracancerous tissue.

Conclusion

The TRIM68, PIKFYVE, and DYNLL2 genes can be used as biomarkers for predicting the prognosis of osteosarcoma.

TRIM Proteins in Colorectal Cancer: TRIM8 as a Promising Therapeutic Target in Chemo Resistance

Colorectal cancer (CRC) represents one of the most widespread forms of cancer in the population and, as all malignant tumors, often develops resistance to chemotherapies with consequent tumor growth and spreading leading to the patient’s premature death. For this reason, a great challenge is to identify new therapeutic targets, able to restore the drugs sensitivity of cancer cells. In this review, we discuss the role of TRIpartite Motifs (TRIM) proteins in cancers and in CRC chemoresistance, focusing on the tumor-suppressor role of TRIM8 protein in the reactivation of the CRC cells sensitivity to drugs currently used in the clinical practice. Since the restoration of TRIM8 protein levels in CRC cells recovers chemotherapy response, it may represent a new promising therapeutic target in the treatment of CRC.

TRIM proteins in neuroblastoma

Neuroblastoma (NB) is the most common extracranial solid tumor in childhood. Outcome for children with high-risk NB remains unsatisfactory. Accumulating evidence suggests that tripartite motif (TRIM) family proteins express diversely in various human cancers and act as regulators of oncoproteins or tumor suppressor proteins. This review summarizes the TRIM proteins involving in NB and the underlying molecular mechanisms. We expect these new insights will provide important implications for the treatment of NB by targeting TRIM proteins.

Recapitulation of prostate tissue cell type-specific transcriptomes by an in vivo primary prostate tissue xenograft model

Studies of the normal functions and diseases of the prostate request in vivo models that maintain the tissue architecture and the multiple-cell type compartments of human origin in order to recapitulate reliably the interactions of different cell types. Cell type-specific transcriptomes are critical to reveal the roles of each cell type in the functions and diseases of the prostate. A primary prostate tissue xenograft model was developed using fresh human prostate tissue specimens transplanted onto male mice that were castrated surgically and implanted with a device to maintain circulating testosterone levels comparable to adult human males. Endothelial cells and epithelial cells were isolated from 7 fresh human prostate tissue specimens and from primary tissue xenografts established from 9 fresh human prostate tissue specimens, using antibody-conjugated magnetic beads specific to human CD31 and human EpCAM, respectively. Transcriptomes of endothelial, epithelial and stromal cell fractions were obtained using RNA-Seq. Global and function-specific gene expression profiles were compared in inter-cell type and inter-tissue type manners. Gene expression profiles in the individual cell types isolated from xenografts were similar to those of cells isolated from fresh tissue, demonstrating the value of the primary tissue xenograft model for studies of the inter-relationships between prostatic cell types and the role of such inter-relationships in organ development, disease progression, and response to drug treatments.

The Tripartite Nexus: Autophagy, Cancer, and Tripartite Motif-Containing Protein Family Members

Autophagy is a cellular degradative process that has multiple important actions in cancer. Autophagy modulation is under consideration as a promising new approach to cancer therapy. However, complete autophagy dysregulation is likely to have substantial undesirable side effects. Thus, more targeted approaches to autophagy modulation may prove clinically beneficial. One potential avenue to achieving this goal is to focus on the actions of tripartite motif-containing protein family members (TRIMs). TRIMs have key roles in an array of cellular processes, and their dysregulation has been extensively linked to cancer risk and prognosis. As detailed here, emerging data shows that TRIMs can play important yet context-dependent roles in controlling autophagy and in the selective targeting of autophagic substrates. This review covers how the autophagy-related actions of TRIM proteins contribute to cancer and the possibility of targeting TRIM-directed autophagy in cancer therapy.

Divergent Modulation of Proteostasis in Prostate Cancer

Proteostasis regulates key cellular processes such as cell proliferation, differentiation, transcription, and apoptosis. The mechanisms by which proteostasis is regulated are crucial and the deterioration of cellular proteostasis has been significantly associated with tumorigenesis since it specifically targets key oncoproteins and tumor suppressors. Prostate cancer (PCa) is the second most common cause of cancer death in men worldwide. Androgens mediate one of the most central signaling pathways in all stages of PCa via the androgen receptor (AR). In addition to their regulation by hormones, PCa cells are also known to be highly secretory and are particularly prone to ER stress as proper ER function is essential. Alterations in various complex signaling pathways and cellular processes including cell cycle control, transcription, DNA repair, apoptosis, cell adhesion, epithelial-mesenchymal transition (EMT), and angiogenesis are critical factors influencing PCa development through key molecular changes mainly by posttranslational modifications in PCa-related proteins, including AR, NKX3.1, PTEN, p53, cyclin D1, and p27. Several ubiquitin ligases like MDM2, Siah2, RNF6, CHIP, and substrate-binding adaptor SPOP; deubiquitinases such as USP7, USP10, USP26, and USP12 are just some of the modifiers involved in the regulation of these key proteins via ubiquitin-proteasome system (UPS). Some ubiquitin-like modifiers, especially SUMOs, have been also closely associated with PCa. On the other hand, the proteotoxicity resulting from misfolded proteins and failure of ER adaptive capacity induce unfolded protein response (UPR) that is an indispensable signaling mechanism for PCa development. Lastly, ER-associated degradation (ERAD) also plays a crucial role in prostate tumorigenesis. In this section, the relationship between prostate cancer and proteostasis will be discussed in terms of UPS, UPR, SUMOylation, ERAD, and autophagy.

Acetic acid alleviates the inflammatory response and liver injury in septic mice by increasing the expression of TRIM40

Sepsis remains a significant health care issue in clinical practice due to its high mortality rate and healthcare cost, despite extensive efforts to better understand the pathophysiology of sepsis. The systemic inflammatory response often leads to severe liver injury, even acute liver dysfunction and failure. Acetic acid, as a type of chemical compound, has been reported to be an emerging drug for improving metabolic syndrome and inhibiting inflammation in rats and human. To verify the effects of acetic acid in protecting the liver and reducing the inflammatory response, a septic mouse model was established by cecal ligation and puncture (CLP), and then the CLP-model mice were treated with acetic acid or PBS. Following the treatment, it was determined that, in CLP-model mice, acetic acid could alleviate the inflammatory response by decreasing the expression of cytokines including interleukin-6 and tumor necrosis factor-α. Additionally, acetic acid also alleviated the liver injury, and the levels of alanine aminotransaminase, aspartate aminotransferase, Toll-like receptor (TLR)4 and nuclear factor-κB (NF-κB) were decreased. The expression of tripartite motif-containing protein (TRIM)40 was also upregulated significantly. Therefore, the authors of the current study hypothesized that acetic acid could decrease the inflammatory response by increasing the expression of TRIM40 and TRIM40 may regulate the activity of the TLR4 signaling pathway. To further illustrate the interaction between TRIM40 and the TLR4 signaling pathway, the authors collected macrophages from the peritoneal cavity by intraperitoneally administering mice with 5 ml ice-cold normal saline. Following the collection, peritoneal macrophages were treated with acetic acid, TRIM40 small interfering RNA or PBS. It was demonstrated that acetic acid upregulated the expression of TRIM40. When TRIM40 was silenced, the protective effect of acetic acid would be reversed as well. The results suggested that TRIM40 could act on and downregulate the activity of the TLR4 signaling pathway. TRIM40 is possibly the major target for acetic acid, which may function as a protective factor in septic mice.

Increased expression of tripartite motif (TRIM) like 2 promotes tumoral growth in human oral cancer

Tripartite motif family-like 2 (TRIML2), a member of the TRIM proteins family, is closely related to Alzheimer's disease, however, no studies of TRIML2 have been published in the cancer research literature. In the current study, we investigated the expression level of TRIML2 and its molecular mechanisms in human oral squamous cell carcinoma (OSCC); reverse transcriptase-quantitative polymerase chain reaction, immunoblot analysis, and immunohistochemistry showed that TRIML2 is up-regulated significantly in OSCCs in vitro and in vivo. TRIML2 knockdown OSCC cells showed decreased cellular proliferation by cell-cycle arrest at G1 phase that resulted from down-regulation of CDK4, CDK6, and cyclin D1 and up-regulation of p21^Cip1 and p27^Kip1. Surprisingly, resveratrol, a polyphenol, led to not only down-regulation of TRIML2 but also cell-cycle arrest at G1 phase similar to TRIML2 knockdown experiments. Taken together, we concluded that TRIML2 might play a significant role in tumoral growth and that resveratrol may be a new drug for treating OSCC by interfering with TRIML2 function.

Knockdown of TRIM66 inhibits malignant behavior and epithelial-mesenchymal transition in non-small cell lung cancer

OBJECTIVE

The tripartite motif 66(TRIM66) is an important member of the TRIM protein superfamily, which can participate in the expression of multiple proteins, and is closely associated with the behaviors of non-small cell lung cancer (NSCLC). In this study, we aimed to explore the effect of TRIM66 in this process in vitro using NSCLC cell lines, and the role of TRIM66 in regulating epithelial-mesenchymal transition(EMT) in NSCLC.

METHODS

Western blotting was used to detect the TRIM66 protein expression levels in NSCLC cell lines and normal lung epithelial cells BEAS-2B. We silenced its expression in A549 cells by transient siRNA transfection to ascertain the function of TRIM66 in NSCLC cells. Western blotting was used to detect the expression of EMT-related proteins.

RESULTS

TRIM66 protein content was highest in NSCLC cell line A549, compared with BEAS-2B, it showed that the TRIM66-siRNA group lung cancer cell proliferation was significantly reduced after knockdown of TRIM66, and knockdown of TRIM66 also suppressed invasion, migration and clonogenic ability of A549 cells. Finally, we found that siRNA-mediated TRIM66 silencing suppressed EMT by downregulating expression of N-cadherin and vimentin and upregulating that of E-cadherin in NSCLC cells, which could effectively reduce the invasive, migratory, and proliferative capacities of lung cancer cells.

CONCLUSION

Silence TRIM66 expression suppressed NSCLC cell proliferation, invasion, and migration. The siRNA-mediated TRIM66 silencing could block the occurrence of EMT. TRIM66 could be a promising novel target for future NSCLC treatments.

Lentivirus-mediated RNA interference of tripartite motif 68 inhibits the proliferation of colorectal cancer cell lines SW1116 and HCT116 in vitro

Colorectal cancer is one of the most common types of cancer worldwide. Previous studies have revealed that certain members of tripartite motif (TRIM) proteins are involved in carcin ogenesis regulation, but little is known about the function of TRIM68 in human colorectal cancer. To investigate the role of TRIM68 in colorectal cancer SW1116 and HCT116 cell lines, the present study conducted lentivirus-mediated knockdown against TRIM68 and demonstrated that depletion of TRIM68 notably inhibits colorectal cancer cell proliferation and colony formation ability. Cell cycle arrest in the G0/G1 phase and cycle accumulation in sub-G1 phase provided evidence that TRIM68 may participate in the regulation of colorectal cancer tumorigenesis. The results revealed the significant role of TRIM68 in regulating colorectal cancer cell mitosis and indicated that TRIM68 may be a promising therapeutic target.

Overexpression of TRIM14 promotes tongue squamous cell carcinoma aggressiveness by activating the NF-κB signaling pathway

Tongue squamous cells carcinoma (TSCC) is one of the most lethal malignancies of oral cancers and its prognosis remains dismal due to the paucity of effective therapeutic targets. Herein, we showed that Tripartite motif containing 14(TRIM14) is markedly up-regulated in TSCC cell lines and clinical tissues. Immunohistochemical (IHC) analysis of 116 clinical TSCC specimens revealed that TRIM14 expression was significantly correlated with the TNM classification (T: P = 0.01; N: P < 0.001; M: P < 0.001) in patients with TSCC. Multivariate analysis indicated that TRIM14 expression might be an independent prognostic indicator for the survival of patients with TSCC. Ectopic expression of TRIM14 in TSCC cells promoted proliferation, angiogenesis, and increased resistance to cisplatin-induced apoptosis of TSCC cells in vitro. Furthermore, TRIM14 overexpressing significantly promoted the tumorigenicity of TSCC cells in vivo whereas silencing endogenous TRIM14 caused an opposite outcome. Moreover, we demonstrated that TRIM14 enhanced TSCC aggressiveness by activating NF-κB signaling. Together, our results provide new evidence that TRIM14 overexpression promotes the progression of TSCC and might represent a novel therapeutic target for its treatment.

Discovery Proteomics Identifies a Molecular Link between the Coatomer Protein Complex I and Androgen Receptor-dependent Transcription

Aberrant androgen receptor (AR)-dependent transcription is a hallmark of human prostate cancers. At the molecular level, ligand-mediated AR activation is coordinated through spatial and temporal protein-protein interactions involving AR-interacting proteins, which we designate the “AR-interactome.” Despite many years of research, the ligand-sensitive protein complexes involved in ligand-mediated AR activation in prostate tumor cells have not been clearly defined. Here, we describe the development, characterization, and utilization of a novel human LNCaP prostate tumor cell line, N-AR, which stably expresses wild-type AR tagged at its N terminus with the streptavidin-binding peptide epitope (streptavidin-binding peptide-tagged wild-type androgen receptor; SBP-AR). A bioanalytical workflow involving streptavidin chromatography and label-free quantitative mass spectrometry was used to identify SBP-AR and associated ligand-sensitive cytosolic proteins/protein complexes linked to AR activation in prostate tumor cells. Functional studies verified that ligand-sensitive proteins identified in the proteomic screen encoded modulators of AR-mediated transcription, suggesting that these novel proteins were putative SBP-AR-interacting proteins in N-AR cells. This was supported by biochemical associations between recombinant SBP-AR and the ligand-sensitive coatomer protein complex I (COPI) retrograde trafficking complex in vitro. Extensive biochemical and molecular experiments showed that the COPI retrograde complex regulates ligand-mediated AR transcriptional activation, which correlated with the mobilization of the Golgi-localized ARA160 coactivator to the nuclear compartment of prostate tumor cells. Collectively, this study provides a bioanalytical strategy to validate the AR-interactome and define novel AR-interacting proteins involved in ligand-mediated AR activation in prostate tumor cells. Moreover, we describe a cellular system to study how compartment-specific AR-interacting proteins influence AR activation and contribute to aberrant AR-dependent transcription that underlies the majority of human prostate cancers.

Increased Expression of Tripartite Motif (TRIM) 47 Is a Negative Prognostic Predictor in Human Prostate Cancer

BACKGROUND

Many prognostic biomarkers associated with androgen signaling have been proposed in PC. The role of tripartite motif (TRIM) proteins remains unclear in PC. We investigated TRIM protein 47 (TRIM47) expression levels in human prostate tissues.

METHODS

We performed immunohistochemistry using original TRIM47 antibody in prostate tissues obtained by radical prostatectomy (n = 105). Stained slides were evaluated for the proportion and staining intensity of immunoreactive cells. Total immunoreactivity (IR) scores (range, 0-8) were calculated as the sum of the proportion and intensity scores. TRIM47 expression levels were confirmed by quantitative reverse transcription polymerase chain reaction (qRT-PCR). Associations between the clinicopathologic features of the patients and their TRIM47 status were analyzed.

RESULTS

Western blot analysis validated the specificity of the anti-TRIM47 antibody in 293T cells. TRIM47 expression levels were found to be significantly increased in PC compared to benign tissues by both immunohistochemistry (P < .0001) and qRT-PCR (P = .003). Additionally, advanced pathologic stage (≥ T3b) was found to be associated with high TRIM47 IR scores (≥ 4; P = .04). Furthermore, high TRIM47 IR scores were also significantly correlated with worse cancer-specific survival rates in multivariate regression analyses (hazard ratio, 6.82; P = .016).

CONCLUSION

The results of the present study indicated differential TRIM47 expression levels in human prostate tissues compared to benign tissues. Because high levels of TRIM47 expression were found to be a strong prognostic factor in PC, TRIM47 may represent a novel therapeutic target.

Screening of Target Genes and Regulatory Function of miRNAs as Prognostic Indicators for Prostate Cancer

Background

MicroRNAs expression profiling of prostate cancer is becoming increasingly used due to its usefulness in diagnosis, staging, prognosis, and response to treatment. The aim of this study was to screen differentially expressed miRNAs in prostate cancer and analyze the functions and signal pathways of their target genes.

Material/Methods

High-throughput data of miRNAs were downloaded from The Cancer Genome Atlas (TCGA) database. A total of 551 samples (52 normal and 499 prostate cancer cases) and 1046 miRNAs expression values were selected for further analysis. Differentially expressed miRNAs between normal and prostate cancer tissues were identified using SAMR. StarBase and TargetScan software were used to predict the miRNAs’ target group and target genes, respectively. GO functional and KEGG pathway analysis was conducted on up/down-regulated expressed miRNA with DAVID. Finally, survival analysis was performed to evaluate the association of differently expressed miRNAs signature and overall survival of prostate cancer patients.

Results

A total of 162 miRNAs were differentially expressed between normal and prostate cancer samples, including 128 up-regulated and 38 down-regulated ones; hsa-mir-153-2, hsa-mir-92a-1, and hsa-mir-182 (up-regulated); and hsa-mir-29a, hsa-mir-10a, and hsa-mir-221 (down-regulated) were identified as good biomarkers. In GO and KEGG analysis, target genes of down-regulated miRNAs were significantly enriched in positive ion combination and JAK-STAT pathway annotation, respectively; the ones with up-regulated miRNAs were significantly enriched in the function of plasma membrane and MARK signaling pathway annotation, respectively. Patients were categorized into low- or high-score groups according to their risk scores from each miRNA. The patients in the low-score group had better overall survival compared with those in high-score group.

Conclusions

The 6 differentially expressed miRNAs and their target genes were used to define important molecular targets that could serve as prognostic and predictive markers in the treatment of prostate cancer. Further research on the function of the target genes in the MAPK signal pathway could provide references for treatment of prostate cancer.

Genetic characterization of Greek population isolates reveals strong genetic drift at missense and trait-associated variants

Isolated populations are emerging as a powerful study design in the search for low-frequency and rare variant associations with complex phenotypes. Here we genotype 2,296 samples from two isolated Greek populations, the Pomak villages (HELIC-Pomak) in the North of Greece and the Mylopotamos villages (HELIC-MANOLIS) in Crete. We compare their genomic characteristics to the general Greek population and establish them as genetic isolates. In the MANOLIS cohort, we observe an enrichment of missense variants among the variants that have drifted up in frequency by more than fivefold. In the Pomak cohort, we find novel associations at variants on chr11p15.4 showing large allele frequency increases (from 0.2% in the general Greek population to 4.6% in the isolate) with haematological traits, for example, with mean corpuscular volume (rs7116019, P=2.3 × 10(-26)). We replicate this association in a second set of Pomak samples (combined P=2.0 × 10(-36)). We demonstrate significant power gains in detecting medical trait associations.

TRIM68 negatively regulates IFN-β production by degrading TRK fused gene, a novel driver of IFN-β downstream of anti-viral detection systems

In recent years members of the tripartite motif-containing (TRIM) family of E3 ubiquitin ligases have been shown to both positively and negatively regulate viral defence and as such are emerging as compelling targets for modulating the anti-viral immune response. In this study we identify TRIM68, a close homologue of TRIM21, as a novel regulator of Toll-like receptor (TLR)- and RIG-I-like receptor (RLR)-driven type I IFN production. Proteomic analysis of TRIM68-containing complexes identified TRK-fused gene (TFG) as a potential TRIM68 target. Overexpression of TRIM68 and TFG confirmed their ability to associate, with TLR3 stimulation appearing to enhance the interaction. TFG is a known activator of NF-κB via its ability to interact with inhibitor of NF-κB kinase subunit gamma (IKK-γ) and TRAF family member-associated NF-κB activator (TANK). Our data identifies a novel role for TFG as a positive regulator of type I IFN production and suggests that TRIM68 targets TFG for lysosomal degradation, thus turning off TFG-mediated IFN-β production. Knockdown of TRIM68 in primary human monocytes resulted in enhanced levels of type I IFN and TFG following poly(I:C) treatment. Thus TRIM68 targets TFG, a novel regulator of IFN production, and in doing so turns off and limits type I IFN production in response to anti-viral detection systems.

Ubiquitin Specific Protease 26 (USP26) expression analysis in human testicular and extragonadal tissues indicates diverse action of USP26 in cell differentiation and tumorigenesis

Ubiquitin specific protease 26 (USP26), a deubiquitinating enzyme, is highly expressed early during murine spermatogenesis, in round spermatids, and at the blood-testis barrier. USP26 has also been recognized as a regulator of androgen receptor (AR) hormone-induced action involved in spermatogenesis and steroid production in in vitro studies. Prior mutation screening of USP26 demonstrated an association with human male infertility and low testosterone production, but protein localization and expression in the human testis has not been characterized previously. USP26 expression analysis of mRNA and protein was completed using murine and human testis tissue and human tissue arrays. USP26 and AR mRNA levels in human testis were quantitated using multiplex qRT-PCR. Immunofluorescence colocalization studies were performed with formalin-fixed/paraffin-embedded and frozen tissues using primary and secondary antibodies to detect USP26 and AR protein expression. Human microarray dot blots were used to identify protein expression in extra-gonadal tissues. For the first time, expression of USP26 and colocalization of USP26 with androgen receptor in human testis has been confirmed predominantly in Leydig cell nuclei, with less in Leydig cell cytoplasm, spermatogonia, primary spermatocytes, round spermatids, and Sertoli cells. USP26 likely affects regulatory proteins of early spermatogenesis, including androgen receptor with additional activity in round spermatids. This X-linked gene is not testis-specific, with USP26 mRNA and protein expression identified in multiple other human organ tissues (benign and malignant) including androgen-dependent tissues such as breast (myoepithelial cells and secretory luminal cells) and thyroid tissue (follicular cells). USP26/AR expression and interaction in spermatogenesis and androgen-dependent cancer warrants additional study and may prove useful in diagnosis and management of male infertility.

Androgen receptor and gene network: Micromechanics reassemble the signaling machinery of TMPRSS2-ERG positive prostate cancer cells

Prostate cancer is a gland tumor in the male reproductive system. It is a multifaceted and genomically complex disease. Transmembrane protease, serine 2 and v-ets erythroblastosis virus E26 homolog (TMPRSS2-ERG) gene fusions are the common molecular signature of prostate cancer. Although tremendous advances have been made in unraveling various facets of TMPRSS2-ERG-positive prostate cancer, many research findings must be sequentially collected and re-interpreted. It is important to understand the activation or repression of target genes and proteins in response to various stimuli and the assembly in signal transduction in TMPRSS2-ERG fusion-positive prostate cancer cells. Accordingly, we divide this multi-component review ofprostate cancer cells into several segments: 1) The role of TMPRSS2-ERG fusion in genomic instability and methylated regulation in prostate cancer and normal cells; 2) Signal transduction cascades in TMPRSS2-ERG fusion-positive prostate cancer; 3) Overexpressed genes in TMPRSS2-ERG fusion-positive prostate cancer cells; 4) miRNA mediated regulation of the androgen receptor (AR) and its associated protein network; 5) Quantitative control of ERG in prostate cancer cells; 6) TMPRSS2-ERG encoded protein targeting; In conclusion, we provide a detailed understanding of TMPRSS2-ERG fusion related information in prostate cancer development to provide a rationale for exploring TMPRSS2-ERG fusion-mediated molecular network machinery.

The TRIM-FLMN protein TRIM45 directly interacts with RACK1 and negatively regulates PKC-mediated signaling pathway

The receptor for activated C-kinase (RACK1), a scaffolding protein that participates in the protein kinase C (PKC) signaling pathway, has an important role in shuttling active PKCs to its substrate. Indeed, recent studies have revealed that RACK1 has an important role in tumorigenesis and that enhancement of the feed-forward mechanism of the c-Jun N-terminal kinase (JNK)-Jun pathway via RACK1 is associated with constitutive activation of MEK (MAPK-ERK kinase)-ERK (extracellular signal-regulated kinase) signaling in human melanoma cells. Taken together, RACK1 additionally has a very important role in the mitogen-activated protein kinase (MAPK) signaling pathway. Here, we show that one of the tripartite motif-containing (TRIM) family ubiquitin ligases, TRIM45, is a novel RACK1-interacting protein and downregulates MAPK signal transduction. Importantly, the expression of TRIM45 is induced when growth-promoting extracellular stimuli activate the MAPK signaling pathway, resulting in attenuation of activation of the MAPK pathway. These findings suggest that TRIM45 functions as a member of the negative feedback loop of the MAPK pathway.

The differently expressed proteins in MSCs of degenerative scoliosis

PURPOSE

Degenerative scoliosis (DS) is an important degenerative lumbar disease causing spinal dysfunction. The true reason or pathogenesis of DS is still unknown. Bone marrow-derived mesenchymal stem cells (BM-MSCs) are the stem/progenitor cells of the osteoblasts. The diseases associated with osteogenesis could be caused by abnormality of the MSCs. The purpose of this study was to find the differential proteins expressed in MSCs of patients with DS.

METHODS

We collected and cultured the MSCs from 12 DS patients and 12 age- and gender-matched patients with lumbar spinal stenosis. Then the MSC samples were analyzed with 2D-DIGE and MALDI-TOF-MS to find the differential proteins which were further validated by Western blot.

RESULTS

We found 115 spots that were differently expressed in the MSC of DS patients with 2D-DIGE, and 44 proteins were identified from samples of DS and control using MALDI-TOF-MS. Of these proteins, PIAS2, NDUFA2, and TRIM 68, which were up-regulated in DS more than 4 times were validated by Western blot.

CONCLUSIONS

The information obtained with this proteomics analysis will be useful in understanding the pathophysiology of DS. Further investigations on the functioning pathway, the specificity and the mechanism of these proteins will be carried out.

Molecular aspects of androgenic signaling and possible targets for therapeutic intervention in prostate cancer

The androgen axis is of crucial importance in the development of novel therapeutic approaches for non-organ-confined prostate cancer. Recent studies revealed that tumor cells have the ability to synthesize androgenic hormones in an intracrine manner. This recognition opened the way for the development of a novel drug, abiraterone acetate, which shows benefits in clinical trials. A novel anti-androgen enzalutamide that inhibits androgen receptor (AR) nuclear translocation has also been developed and tested in the clinic. AR coactivators exert specific cellular regulatory functions, however it is difficult to improve the treatment because of a large number of coregulators overexpressed in prostate cancer. AR itself is a target of several miRNAs which may cause its increased degradation, inhibition of proliferation, and increased apoptosis. Truncated AR occur in prostate cancer as a consequence of alternative splicing. They exhibit ligand-independent transcriptional activity. Although there has been an improvement of endocrine therapy in prostate cancer, increased intracrine ligand synthesis and appearance of variant receptors may facilitate the development of resistance.

miR-17-5p targets the p300/CBP-associated factor and modulates androgen receptor transcriptional activity in cultured prostate cancer cells

BACKGROUND

Androgen receptor (AR) signalling is critical to the initiation and progression of prostate cancer (PCa). Transcriptional activity of AR involves chromatin recruitment of co-activators, including the p300/CBP-associated factor (PCAF). Distinct miRNA expression profiles have been identified in PCa cells during the development and progression of the disease. Whether miRNAs regulate PCAF expression in PCa cells to regulate AR transcriptional activity is still unclear.

METHODS

Expression of PCAF was investigated in several PCa cell lines by qRT-PCR, Western blot, and immunocytochemistry. The effects of PCAF expression on AR-regulated transcriptional activity and cell growth in PCa cells were determined by chromatin immunoprecipitation, reporter gene construct analysis, and MTS assay. Targeting of PCAF by miR-17-5p was evaluated using the luciferase reporter assay.

RESULTS

PCAF was upregulated in several PCa cell lines. Upregulation of PCAF promoted AR transcriptional activation and cell growth in cultured PCa cells. Expression of PCAF in PCa cells was associated with the downregulation of miR-17-5p. Targeting of the 3'-untranslated region of PCAF mRNA by miR-17-5p caused translational suppression and RNA degradation, and, consequently, modulation of AR transcriptional activity in PCa cells.

CONCLUSIONS

PCAF is upregulated in cultured PCa cells, and upregulation of PCAF is associated with the downregulation of miR-17-5p. Targeting of PCAF by miR-17-5p modulates AR transcriptional activity and cell growth in cultured PCa cells.

miR-141 modulates androgen receptor transcriptional activity in human prostate cancer cells through targeting the small heterodimer partner protein

BACKGROUND

Aberrant expressions of microRNAs, including upregulation of miR-141, are closely associated with the tumorigenesis of prostate cancer (PCa). The orphan receptor small heterodimer partner (Shp) is a co-repressor to androgen receptor (AR) and represses AR-regulated transcriptional activity.

METHODS

Here, we investigated the correlation of Shp expression with the cellular level of miR-141 and its effects on AR transcriptional activity in non-malignant and malignant human prostate epithelial cell lines.

RESULTS

We found that Shp was downregulated in multiple PCa cell lines. The mature form of miR-141 was upregulated in PCa cells. miR-141 could target 3'-untranslated region of Shp mRNA resulting in translational suppression and RNA degradation. Moreover, enforced expression of Shp or inhibition of miR-141 function by anti-miR-141 attenuated AR-regulated transcriptional activity in AR-responsive LNCaP cells. Phenethyl isothiocyanate, a natural constituent of many edible cruciferous vegetables, increased Shp expression, downregulated miR-141, and inhibited AR transcriptional activity in LNCaP cells.

CONCLUSIONS

Shp is a target for miR-141 and it is downregulated in cultured human PCa cells with the involvement of upregulation of miR-141, which promotes AR transcriptional activity. Moreover, Shp and miR-141 could be targets for chemoprevention for PCa.

Epigenetic deregulation of miR-29a and miR-1256 by isoflavone contributes to the inhibition of prostate cancer cell growth and invasion

The epigenetic regulation of genes has long been recognized as one of the causes of prostate cancer (PCa) development and progression. Recent studies have shown that a number of microRNAs (miRNAs) are also epigenetically regulated in different types of cancers including PCa. In this study, we found that the DNA sequence of the promoters of miR-29a and miR-1256 are partly methylated in PCa cells, which leads to their lower expression both in PCa cells and in human tumor tissues compared with normal epithelial cells and normal human prostate tissues. By real-time PCR, Western Blot analysis and miRNA mimic and 3'-UTR-Luc transfection, we found that TRIM68 is a direct target of miR-29a and miR-1256 and that the downregulation of miR-29a and miR-1256 in PCa cells leads to increased expression of TRIM68 and PGK-1 in PCa cells and in human tumor tissue specimens. Interestingly, we found that a natural agent, isoflavone, could demethylate the methylation sites in the promoter sequence of miR-29a and miR-1256, leading to the upregulation of miR-29a and miR-1256 expression. The increased levels of miR-29a and miR-1256 by isoflavone treatment resulted in decreased expression of TRIM68 and PGK-1, which is mechanistically linked with inhibition of PCa cell growth and invasion. The selective demethylation activity of isoflavone on miR-29a and miR-1256 leading to the suppression of TRIM68 and PGK-1 expression is an important biological effect of isoflavone, suggesting that isoflavone could be a useful non-toxic demethylating agent for the prevention of PCa development and progression.

TRIM45 negatively regulates NF-κB-mediated transcription and suppresses cell proliferation

The NF-κB signaling pathway plays an important role in cell survival, immunity, inflammation, carcinogenesis, and organogenesis. Activation of NF-κB is regulated by several posttranslational modifications including phosphorylation, neddylation and ubiquitination. The NF-κB signaling pathway is activated by two distinct signaling mechanisms and is strictly modulated by the ubiquitin-proteasome system. It has been reported that overexpression of TRIM45, one of the TRIM family ubiquitin ligases, suppresses transcriptional activities of Elk-1 and AP-1, which are targets of the MAPK signaling pathway. In this study, we showed that TRIM45 also negatively regulates TNFα-induced NF-κB-mediated transcription by a luciferase reporter assay and that TRIM45 lacking a RING domain also has an activity to inhibit the NF-κB signal. Moreover, we found that TRIM45 overexpression suppresses cell growth. These findings suggest that TRIM45 acts as a repressor for the NF-κB signal and regulates cell growth.

TRIM6 interacts with Myc and maintains the pluripotency of mouse embryonic stem cells

The proto-oncogene product Myc is a master regulator of cell proliferation through its specific binding to the E-box motif in genomic DNA. It has been reported that Myc has an important role in the proliferation and maintenance of the pluripotency of embryonic stem (ES) cells and that the transcriptional activity of Myc is regulated by several post-translational modifications, including ubiquitination. In this study, we showed that tripartite motif containing 6 (TRIM6), one of the TRIM family ubiquitin ligases, was selectively expressed in ES cells and interacted with Myc followed by attenuation of the transcriptional activity of Myc. Knockdown of TRIM6 in ES cells enhanced the transcriptional activity of Myc and repressed expression of NANOG, resulting in the promotion of ES cell differentiation. These findings indicate that TRIM6 regulates the transcriptional activity of Myc during the maintenance of ES cell pluripotency, suggesting that TRIM6 functions as a novel regulator for Myc-mediated transcription in ES cells.

TRIM32 promotes retinoic acid receptor α-mediated differentiation in human promyelogenous leukemic cell line HL60

Ubiquitination, one of the posttranslational modifications, appears to be involved in the transcriptional activity of nuclear receptors including retinoic acid receptor α (RARα). We previously reported that an E3 ubiquitin ligase, TRIM32, interacts with several important proteins including RARα and enhances transcriptional activity of RARα in mouse neuroblastoma cells and embryonal carcinoma cells. Retinoic acid (RA), which acts as a ligand to nuclear receptors including RARα, plays crucial roles in development, differentiation, cell cycles and apoptosis. In this study, we found that TRIM32 enhances RARα-mediated transcriptional activity even in the absence of RA and stabilizes RARα in the human promyelogenous leukemic cell line HL60. Moreover, we found that overexpression of TRIM32 in HL60 cells suppresses cellular proliferation and induces granulocytic differentiation even in the absence of RA. These findings suggest that TRIM32 functions as one of the coactivators for RARα-mediated transcription in acute promyelogenous leukemia (APL) cells, and thus TRIM32 may become a potentially therapeutic target for APL.

Identification of molecular vulnerabilities in human multiple myeloma cells by RNA interference lethality screening of the druggable genome

Despite recent advances in targeted treatments for multiple myeloma, optimal molecular therapeutic targets have yet to be identified. To functionally identify critical molecular targets, we conducted a genome-scale lethality study in multiple myeloma cells using siRNAs. We validated the top 160 lethal hits with four siRNAs per gene in three multiple myeloma cell lines and two non-myeloma cell lines, cataloging a total of 57 potent multiple myeloma survival genes. We identified the Bcl2 family member MCL1 and several 26S proteasome subunits among the most important and selective multiple myeloma survival genes. These results provided biologic validation of our screening strategy. Other essential targets included genes involved in RNA splicing, ubiquitination, transcription, translation, and mitosis. Several of the multiple myeloma survival genes, especially MCL1, TNK2, CDK11, and WBSCR22, exhibited differential expression in primary plasma cells compared with other human primary somatic tissues. Overall, the most striking differential functional vulnerabilities between multiple myeloma and non-multiple myeloma cells were found to occur within the 20S proteasome subunits, MCL1, RRM1, USP8, and CKAP5. We propose that these genes should be investigated further as potential therapeutic targets in multiple myeloma.

Androgen receptor co-activators in the regulation of cellular events in prostate cancer

OBJECTIVES

Androgen receptor (AR) action in benign and malignant tissue is potentiated by a number of co-regulatory proteins that may interact with one or more receptor domains. With improvement of research methodologies, it became possible to detect a number of co-activators whose expression is increased in prostate cancer tissue.

METHODS

Manuscripts describing prostate cancer-relevant regulation of cellular events by co-activators are selected and summarized.

RESULTS

AR co-activators may regulate histone modification, proteasomal degradation, chaperones, sumoylation, chromatin remodeling, and cytoskeleton. Some of them (TIF-2) are up-regulated by androgens, whereas the expression of others increases during androgen ablation (p300, CBP, and Tip60). Most co-factors are important for the stimulation of cellular proliferation, although in some cases (ART-27), they act as tumor suppressors and are deleted in prostate cancer tissue. In addition to stimulating AR, some co-activators suppress apoptosis in prostate cancer cells that do not express the AR (p300 and SRC-3). It was recently shown that the inhibition of p300 slows down proliferation, stimulates apoptosis, and inhibits migration and invasion.

CONCLUSIONS

Co-factors whose down-regulation results in the alterations of multiple cellular functions may be valid targets for novel therapies in advanced prostate cancer.

TRIM proteins and cancer

Emerging clinical evidence shows that the deregulation of ubiquitin-mediated degradation of oncogene products or tumour suppressors is likely to be involved in the aetiology of carcinomas and leukaemias. Recent studies have indicated that some members of the tripartite motif (TRIM) proteins (one of the subfamilies of the RING type E3 ubiquitin ligases) function as important regulators for carcinogenesis. This Review focuses on TRIM proteins that are involved in tumour development and progression.

TRIM32 promotes neural differentiation through retinoic acid receptor-mediated transcription

Retinoic acid (RA), a metabolite of vitamin A, plays versatile roles in development, differentiation, cell cycles and regulation of apoptosis by regulating gene transcription through nuclear receptor activation. Ubiquitinylation, which is one of the post-translational modifications, appears to be involved in the transcriptional activity of intranuclear receptors including retinoic acid receptor α (RARα). Mutations in the tripartite motif-containing protein 32 gene (TRIM32; also known as E3 ubiquitin-protein ligase) have been reported to be responsible for limb-girdle muscular dystrophy type 2H in humans, and its encoded protein has been shown to interact with several other important proteins. In this study, we found that TRIM32 interacts with RARα and enhances its transcriptional activity in the presence of RA. We also found that overexpression of TRIM32 in mouse neuroblastoma cells and embryonal carcinoma cells promoted stability of RARα, resulting in enhancement of neural differentiation. These findings suggest that TRIM32 functions as one of the co-activators for RARα-mediated transcription, and thereby TRIM32 is a potential therapeutic target for developmental disorders and RA-dependent leukemias.

TRIM40 promotes neddylation of IKKγ and is downregulated in gastrointestinal cancers

Gastrointestinal neoplasia seems to be a common consequence of chronic inflammation in the gastrointestinal epithelium. Nuclear factor-kappaB (NF-κB) is an important transcription factor for carcinogenesis in chronic inflammatory diseases and plays a key role in promoting inflammation-associated carcinoma in the gastrointestinal tract. Activation of NF-κB is regulated by several posttranslational modifications including phosphorylation, ubiquitination and neddylation. In this study, we showed that tripartite motif (TRIM) 40 is highly expressed in the gastrointestinal tract and that TRIM40 physically binds to Nedd8, which is conjugated to target proteins by neddylation. We also found that TRIM40 promotes the neddylation of inhibitor of nuclear factor kappaB kinase subunit gamma, which is a crucial regulator for NF-κB activation, and consequently causes inhibition of NF-κB activity, whereas a dominant-negative mutant of TRIM40 lacking the RING domain does not inhibit NF-κB activity. Knockdown of TRIM40 in the small intestinal epithelial cell line IEC-6 caused NF-κB activation followed by increased cell growth. In addition, we found that TRIM40 is highly expressed in normal gastrointestinal epithelia but that TRIM40 is downregulated in gastrointestinal carcinomas and chronic inflammatory lesions of the gastrointestinal tract. These findings suggest that TRIM40 inhibits NF-κB activity via neddylation of inhibitor of nuclear factor kappaB kinase subunit gamma and that TRIM40 prevents inflammation-associated carcinogenesis in the gastrointestinal tract.

The deubiquitinating enzyme USP26 is a regulator of androgen receptor signaling

The androgen receptor (AR) is a member of the nuclear receptor superfamily and is essential for male sexual development and maturation, as well as prostate cancer development. Regulation of AR signaling activity depends on several posttranslational modifications, one of these being ubiquitination. We screened a short hairpin library targeting members of the deubiquitination enzyme family and identified the X-linked deubiquitination enzyme USP26 as a novel regulator of AR signaling. USP26 is a nuclear protein that binds to AR via three important nuclear receptor interaction motifs, and modulates AR ubiquitination, consequently influencing AR activity and stability. Our data suggest that USP26 assembles with AR and other cofactors in subnuclear foci, and serves to counteract hormone-induced AR ubiquitination, thereby contributing to the regulation of AR transcriptional activity.

Partners in crime: deregulation of AR activity and androgen synthesis in prostate cancer

Prostate cancer remains a leading cause of cancer death, as there are no durable means to treat advanced disease. Treatment of non-organ-confined prostate cancer hinges on its androgen dependence. First-line therapeutic strategies suppress androgen receptor (AR) activity, via androgen ablation and direct AR antagonists, whereas initially effective, incurable, 'castration-resistant' tumors arise as a result of resurgent AR activity. Alterations of AR and/or associated regulatory networks are known to restore receptor activity and support resultant therapy-resistant tumor progression. However, recent evidence also reveals an unexpected contribution of the AR ligand, indicating that alterations in pathways controlling androgen synthesis support castration-resistant AR activity. In this report, the mechanisms underlying the lethal pairing of AR deregulation and aberrant androgen synthesis in prostate cancer progression will be discussed.

TRIM24 mediates ligand-dependent activation of androgen receptor and is repressed by a bromodomain-containing protein, BRD7, in prostate cancer cells

The androgen receptor (AR) is a ligand-dependent transcription factor that belongs to the family of nuclear receptors, and its activity is regulated by numerous AR coregulators. AR plays an important role in prostate development and cancer. In this study, we found that TRIM24/transcriptional intermediary factor 1alpha (TIF1alpha), which is known as a ligand-dependent nuclear receptor co-regulator, interacts with AR and enhances transcriptional activity of AR by dihydrotestosterone in prostate cancer cells. We showed that TRIM24 functionally interacts with TIP60, which acts as a coactivator of AR and synergizes with TIP60 in the transactivation of AR. We also showed that TRIM24 binds to bromodomain containing 7 (BRD7), which can negatively regulate cell proliferation and growth. A luciferase assay indicated that BRD7 represses the AR transactivation activity upregulated by TRIM24. These findings indicate that TRIM24 regulates AR-mediated transcription in collaboration with TIP60 and BRD7.

TRIM31 interacts with p52(Shc) and inhibits Src-induced anchorage-independent growth

Tripartite motif-containing protein (TRIM) family proteins are involved in a broad range of biological processes and, consistently, their alterations result in diverse pathological conditions such as genetic diseases, viral infection and cancer development. In this study, we found that one of the TRIM family proteins, TRIM31, is highly expressed in the gastrointestinal tract and interacts with p52(Shc), one of the signal transducers. We also found by a binding assay that almost the whole region other than the RING domain is required for the binding to p52(Shc) but found by pulse-chase analysis that overexpression of TRIM31 does not affect the stability of p52(Shc). Moreover, we found that overexpression of TRIM31 suppresses anchorage-independent cell growth induced by the active form of c-Src. These results suggest that TRIM31 attenuates c-Src signaling via p52(Shc) under anchorage-independent growth conditions and is potentially associated with growth activity of cells in the gastrointestinal tract.

TRIM21 is essential to sustain IFN regulatory factor 3 activation during antiviral response

Virus infection induces host antiviral responses including induction of type I IFNs. Transcription factor IFN regulatory factor 3 (IRF3) plays an essential role and is tightly regulated in this process. Herein we report that TRIM21 (tripartite motif-containing 21) is significantly induced and interacts with IRF3 upon RNA virus infection. Ectopic expression or knockdown of TRIM21 could respectively enhance or impair IRF3-mediated gene expression. Mechanistically, TRIM21 interferes with the interaction between Pin1 (peptidyl-prolyl cis/trans isomerase, NIMA-interacting 1) and IRF3, thus preventing IRF3 ubiquitination and degradation. A conserved motif in the B 30.2 domain of TRIM21 is critical for its modulation of IRF3 function, while the RING finger is dispensable. Host antiviral responses are significantly boosted or crippled in the presence or absence of TRIM21. Our results identify TRIM21 as an essential modulator of IRF3 stability and demonstrate that it positively regulates the strength and duration of primary antiviral response, thus further strengthening the notion that the TRIM family is evolutionarily integrated with innate immunity.

TRIM36 interacts with the kinetochore protein CENP-H and delays cell cycle progression

The tripartite motif-containing protein (TRIM) family is defined by the presence of a common domain structure composed of a RING finger, a B-box, and a coiled-coil motif. TRIM family proteins are involved in a broad range of biological processes and, consistently, their alterations result in diverse pathological conditions such as genetic diseases, viral infection, and cancer development. In this study, we found by using yeast two-hybrid screening that TRIM36 has a ubiquitin ligase activity and interacts with centromere protein-H, one of the kinetochore proteins. We also found by immunofluorescence analysis that TRIM36 colocalizes with alpha-tubulin, one of the microtubule proteins. Moreover, we found that overexpression of TRIM36 decelerates the cell cycle and attenuates cell growth. These results indicate that TRIM36 is potentially associated with chromosome segregation and that an excess of TRIM36 may cause chromosomal instability.

Transcription factors, chromatin and cancer

Transcription factors, chromatin and chromatin-modifying enzymes are key components in a complex network through which the genome interacts with its environment. For many transcription factors, binding motifs are found adjacent to the promoter regions of a large proportion of genes, requiring mechanisms that confer binding specificity in any given cell type. These include association of the factor with other proteins and packaging of DNA, as chromatin, at the binding sequence so as to inhibit or facilitate binding. Recent evidence suggests that specific post-translational modifications of the histones packaging promoter DNA can help guide transcription factors to selected sites. The enzymes that put such modifications in place are dependent on metabolic components (e.g. acetyl CoA, S-adenosyl methionine) and susceptible to inhibition or activation by environmental factors. Local patterns of histone modification can be altered or maintained through direct interaction between the transcription factor and histone modifying enzymes. The functional consequences of transcription factor binding are also dependent on protein modifying enzymes, particularly those that alter lysine methylation at selected residues. Remarkably, the role of these enzymes is not limited to promoter-proximal events, but can be linked to changes in the intranuclear location of target genes. In this review we describe results that begin to define how transcription factors, chromatin and environmental variables interact and how these interactions are subverted in cancer. We focus on the nuclear receptor family of transcription factors, where binding of ligands such as steroid hormones and dietary derived factors provides an extra level of environmental input.