High expression of p300 is linked to aggressive features and poor prognosis of nasopharyngeal carcinoma

Protein lysine acetyltransferase CBP/p300: A promising target for small molecules in cancer treatment

CBP and p300 are homologous proteins exhibiting remarkable structural and functional similarity. Both proteins function as acetyltransferase and coactivator, underscoring their significant roles in cellular processes. The function of histone acetyltransferases is to facilitate the release of DNA from nucleosomes and act as transcriptional co-activators to promote gene transcription. Transcription factors recruit CBP/p300 by co-condensation and induce transcriptional bursting. Disruption of CBP or p300 functions is associated with different diseases, especially cancer, which can result from either loss of function or gain of function. CBP and p300 are multidomain proteins containing HAT (histone acetyltransferase) and BRD (bromodomain) domains, which perform acetyltransferase activity and maintenance of HAT signaling, respectively. Inhibitors targeting HAT and BRD have been explored for decades, and some BRD inhibitors have been evaluated in clinical trials for treating hematologic malignancies or advanced solid tumors. Here, we review the development and application of CBP/p300 inhibitors. Several inhibitors have been evaluated in vivo, exhibiting notable potency but limited selectivity. Exploring these inhibitors emphasizes the promise of targeting CBP and p300 with small molecules in cancer therapy.

Comprehensive Characterization of HATs and HDACs in Human Cancers Reveals Their Role in Immune Checkpoint Blockade

Histone acetylation that controlled by two mutually antagonistic enzyme families, histone acetyl transferases (HATs) and histone deacetylases (HDACs), as one of major epigenetic mechanisms controls transcription and its abnormal regulation was implicated in various aspects of cancer. However, the comprehensive understanding of HDACs and HATs in cancer is still lacking. Systematically analysis through 33 cancer types based on next-generation sequence data reveals heterogeneous expression pattern of HDACs and HATs across different cancer types. In particular, HDAC10 and HDAC6 show significant downregulation in most cancers. Principal components analysis (PCA) of pan-cancer reveals significant difference of HDACs and HATs between normal tissues and normal tissue adjacent to the tumor. The abnormal expression of HDACs and HATs was partially due to CNV and DNA methylation in multiple types of cancer. Prognostic significance (AUC reached 0.736) of HDACs and HATs demonstrates a five-gene signature including KAT2A, HAT1, KAT5, CREBBP and SIRT1 in KIRC. Analysis of NCI-60 drug database reveals the cytotoxic effect of several drugs are associated with dysregulated expression of HDACs and HATs. Analysis of immune infiltration and immunotherapy reveals that KAT2B and HDAC9 are associated with immune infiltration and immunotherapy. Our analysis provided comprehensive understanding of the regulation and implication of HDACs and HATs in pan-cancer. These findings provide novel evidence for biological investigating potential individual HDACs and HATs in the development and therapy of cancer in the future.

Advances of Epigenetic Biomarkers and Epigenome Editing for Early Diagnosis in Breast Cancer

Epigenetic modifications are known to regulate cell phenotype during cancer progression, including breast cancer. Unlike genetic alterations, changes in the epigenome are reversible, thus potentially reversed by epi-drugs. Breast cancer, the most common cause of cancer death worldwide in women, encompasses multiple histopathological and molecular subtypes. Several lines of evidence demonstrated distortion of the epigenetic landscape in breast cancer. Interestingly, mammary cells isolated from breast cancer patients and cultured ex vivo maintained the tumorigenic phenotype and exhibited aberrant epigenetic modifications. Recent studies indicated that the therapeutic efficiency for breast cancer regimens has increased over time, resulting in reduced mortality. Future medical treatment for breast cancer patients, however, will likely depend upon a better understanding of epigenetic modifications. The present review aims to outline different epigenetic mechanisms including DNA methylation, histone modifications, and ncRNAs with their impact on breast cancer, as well as to discuss studies highlighting the central role of epigenetic mechanisms in breast cancer pathogenesis. We propose new research areas that may facilitate locus-specific epigenome editing as breast cancer therapeutics.

Discovery of novel benzimidazole derivatives as potent p300 bromodomain inhibitors with anti-proliferative activity in multiple cancer cells

Adenovirus E1A-associated 300-k_D protein (p300) bromodomain, which regulates gene expression by recognizing acetylated lysine (KAc) of histone, is a promising target for the treatment of cancer. Herein, a series of potent p300 bromodomain inhibitors with novel CBP30-based scaffolds was discovered through bioisosterism and conformational restriction strategies. The most promising compound 1u showed more potent inhibitory activity (IC₅₀ = 49 nM) against p300 bromodomain and anti-proliferative activity in various cancer cell lines compared to CBP30. Moreover, 1u suppressed the expression of c-Myc and induced G₁/G₀ phase arrest and apoptosis in OPM-2 cells more potently than CBP30. This study provides new lead compounds for further research on the biological functions of p300.

The p300 Inhibitor A-485 Exerts Antitumor Activity in Growth Hormone Pituitary Adenoma

CONTEXT

Growth hormone pituitary adenoma (GHPA), a major subtype of pituitary adenoma (PA), can lead to progressive somatic disfigurement, multiple complications, and even increased mortality. The efficacy of current treatments is limited; thus, a novel pharmacological treatment is urgently needed. As a histone acetyltransferase (HAT) coactivator, p300 can regulate the transcription of several genes that are crucial for PA tumorigenesis and progression. However, the role of p300 and its catalytic inhibitor in GHPA is still unclear.

OBJECTIVE

We aimed to identify the expression of p300 in GHPA and in normal pituitary glands.

METHODS

The expression of p300 was detected in GHPA and normal pituitary tissues. Genetic knockdown was performed by siRNA. The efficacy of the p300 inhibitor A-485 in the cell cycle, proliferation, apoptosis, and hormone secretion was investigated by flow cytometry, ELISAs, Western blotting, and qRT-PCR. RNA sequencing, bioinformatic analysis, and subsequent validation experiments were performed to reveal the potential biological mechanism of A-485.

RESULTS

High expression of p300 was found in GHPA tissues compared with normal pituitary tissues. Knockdown of p300 inhibited cell proliferation and clone formation. Treatment with A-485 suppressed cell growth and inhibited the secretion of GH in vitro and in vivo. Further mechanistic studies showed that A-485 could downregulate the expression or activity of several oncogenes, such as genes in the Pttg1, c-Myc, cAMP and PI3K/AKT/mTOR signaling pathways, which are crucial for PA tumorigenesis and progression.

CONCLUSION

Our findings demonstrate that inhibition of HAT p300 by its selective inhibitor A-485 is a promising therapy for GHPA.

Epigenetic Mechanisms in Parenchymal Lung Diseases: Bystanders or Therapeutic Targets?

Epigenetic responses due to environmental changes alter chromatin structure, which in turn modifies the phenotype, gene expression profile, and activity of each cell type that has a role in the pathophysiology of a disease. Pulmonary diseases are one of the major causes of death in the world, including lung cancer, idiopathic pulmonary fibrosis (IPF), chronic obstructive pulmonary disease (COPD), pulmonary hypertension (PH), lung tuberculosis, pulmonary embolism, and asthma. Several lines of evidence indicate that epigenetic modifications may be one of the main factors to explain the increasing incidence and prevalence of lung diseases including IPF and COPD. Interestingly, isolated fibroblasts and smooth muscle cells from patients with pulmonary diseases such as IPF and PH that were cultured ex vivo maintained the disease phenotype. The cells often show a hyper-proliferative, apoptosis-resistant phenotype with increased expression of extracellular matrix (ECM) and activated focal adhesions suggesting the presence of an epigenetically imprinted phenotype. Moreover, many abnormalities observed in molecular processes in IPF patients are shown to be epigenetically regulated, such as innate immunity, cellular senescence, and apoptotic cell death. DNA methylation, histone modification, and microRNA regulation constitute the most common epigenetic modification mechanisms.

Role of histone acetyltransferase inhibitors in cancer therapy

The development of cancer is a complex phenomenon driven by various extrinsic as well as intrinsic risk factors including epigenetic modifications. These post-translational modifications are encountered in diverse cancer cells and appear for a relatively short span of time. These changes can significantly affect various oncogenic genes and proteins involved in cancer initiation and progression. Histone lysine acetylation and deacetylation processes are controlled by two opposing classes of enzymes that modulate gene regulation either by adding an acetyl moiety on a histone lysine residue by histone lysine acetyltransferases (KATs) or via removing it by histone deacetylases (KDACs). Deregulated KAT activity has been implicated in the development of several diseases including cancer and can be targeted for the development of anti-neoplastic drugs. Here, we describe the predominant epigenetic changes that can affect key KAT superfamily members during carcinogenesis and briefly highlight the pharmacological potential of employing lysine acetyltransferase inhibitors (KATi) for cancer therapy.

Identification of novel biomarkers and small-molecule compounds for nasopharyngeal carcinoma with metastasis

The purpose of this study was to investigate novel biomarkers and potential mechanisms in nasopharyngeal carcinoma (NPC) patients with metastasis.Two microarray datasets (GSE103611 and GSE36682) were obtained from GEO database, differentially expressed genes (DEGs) and differentially expressed miRNA (DEMs) were identified, Gene ontology (GO) as well as Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis were conducted with DEGs and DEMs targeted genes. Protein-protein interactions (PPI) network of the DEGs and DEMs targeted genes were constructed, furthermore, Connectivity Map (CMap) database was applied to select the potential drugs with therapeutic effects.Overall, we identified 396 upregulated and 19 downregulated DEGs. Additionally, we identified 1 upregulated DEM, miR-135b, and a downregulated DEM, miR-574-5p. Functional enrichment analysis indicated that both DEGs and DEMs targeted genes participated in biological process (BP) of regulation of transcription from RNA polymerase II promoter, DNA-templated positive regulation of transcription, and Epstein-Barr virus infection signaling pathway. Besides, upregulated EP300 gene was a hub node both in DEGs and DEMs target genes. CMap database analysis indicated that sanguinarine, verteporfin, and chrysin are potential drugs for prevention and treatment of NPC metastasis.In summary, the common hub gene, biological process and pathway identified in the study provided a novel insight into the potential mechanism of NPC metastasis. Furthermore, we identified several possible small molecule compounds for treatment of NPC metastasis.

Prognostic role of upregulated P300 expression in human cancers: A clinical study of synovial sarcoma and a meta-analysis

E1A binding protein p300 (P300) is a member of the histone acetyltransferase family of transcriptional co-activators, which are associated with various types of cancer. Numerous studies have evaluated the diagnostic value of P300, but their results are not consistent. Therefore, a clinical study and a meta-analysis were performed in the present study to investigate the prognostic value of P300 expression in human malignant neoplasms. Immunohistochemical (IHC) analysis was used to assess P300 expression in 43 paraffin-embedded primary synovial sarcoma (SS) samples. For the meta-analysis, eligible studies published until January 21, 2018 were identified by searching the PubMed, EMBASE and Web of Science databases. The IHC analysis indicated a high P300 expression rate in 33.3% (10/30) of biphasic SS (BSSs) and in 60% (6/10) of monophasic fibrous SS tissues. In BSS, the expression rate was significantly higher in the epithelial component (80.0%, 24/30) than that in the spindle-cell component (30.0%, 9/30; P<0.05). The meta-analysis indicated that high expression of P300 was associated with poor overall survival (OS) in digestive system malignant neoplasms (HR=1.54, 95% CI: 1.20-2.23), as well as with poor progression-free survival, recurrence-free survival and disease-free survival combined (HR=1.84, 95% CI: 1.36-2.47). Analysis of subgroups by ethnicity demonstrated that high expression of P300 was associated with poor OS in Asians (HR=1.72, 95% CI: 1.20-2.47) but favourable OS in Caucasians (HR=0.59, 95% CI: 0.47-0.73). Furthermore, high expression of P300 was associated with clinical stage [Relative Risk (RR)=1.30, 95% CI: 1.07-1.58], lymph node metastasis (RR=1.30, 95% CI: 1.03-1.64) and depth of invasion (RR=1.31, 95% CI: 1.07-1.60). P300 expression may therefore be a useful biomarker for predicting patient prognosis in various types of human cancer.

Oncogenic EP300 can be targeted with inhibitors of aldo-keto reductases

E-cadherin transcriptional activator EP300 is down-regulated in metaplastic breast carcinoma, a rare form of triple negative and E-cadherin-negative aggressive breast cancer with a poor clinical outcome. In order to shed light on the regulation of E-cadherin by EP300 in breast cancer we analyzed by immunohistochemistry 41 cases of invasive breast cancer with both E-cadherinhigh and E-cadherinlow expression levels, together with 20 non-malignant breast tissues. EP300 and E-cadherin showed a positive correlation in both non-malignant and cancer cases and both markers together were better predictors of lymph node metastasis than E-cadherin alone. These data support a metastasis suppressor role for EP300 in breast cancer. However, some reports suggest an oncogenic role for EP300. We generated a breast cancer cell model to study E-cadherin-independent effects of EP300 by over-expression of EP300 in HS578T cells which have E-cadherin promoter hypermethylated. In this cell system, EP300 led to up-regulation of mesenchymal (vimentin, Snail, Slug, Zeb1) and stemness (ALDH+ and CD44high/CD24low) markers, increases in migration, invasion, anchorage-independent growth and drug resistance. Genome-wide expression profiling identified aldo-keto reductases AKR1C1-3 as effectors of stemness and drug resistance, since their pharmacological inhibition with flufenamic acid restored both doxorubicin and paclitaxel sensitivity and diminished mammosphere formation. Thus, in cells with a permissive E-cadherin promoter, EP300 acts as a tumour/metastasis supressor by up-regulating E-cadherin expression, maintenance of the epithelial phenotype and avoidance of an epithelial-to-mesenchymal transition. In cells in which the E-cadherin promoter is hypermethylated, EP300 functions as an oncogene via up-regulation of aldo-keto reductases. This offers the rationale of using current aldo-keto reductase inhibitors in breast cancer treatment.

P300 inhibition enhances gemcitabine-induced apoptosis of pancreatic cancer

The transcriptional cofactor p300 has histone acetyltransferase activity (HAT) and has been reported to participate in chromatin remodeling and DNA repair. We hypothesized that targeting p300 can enhance the cytotoxicity of gemcitabine, which induces pancreatic cancer cell apoptosis by damaging DNA. Expression of p300 was confirmed in pancreatic cancer cell lines and human pancreatic adenocarcinoma tissues by western blotting and immunohistochemistry. When pancreatic cancer cells were treated with gemcitabine, p300 was recruited to chromatin within 24 hours, indicating the role in response to DNA damage. When p300 was gene-silenced with siRNA, histone acetylation was substantially reduced and pancreatic cancer cells were sensitized to gemcitabine. The selective p300 HAT inhibitor C646 similarly decreased histone acetylation, increased gemcitabine-induced apoptosis and thus enhanced the cytotoxicity of gemcitabine on pancreatic cancer cells. These findings indicate that p300 contributes to chemo-resistance of pancreatic cancer against gemcitabine and suggest that p300 and its HAT activity may be a potential therapeutic target to improve outcomes in patients with pancreatic cancer.

The multifaceted role of lysine acetylation in cancer: prognostic biomarker and therapeutic target

Lysine acetylation is a post-translational modification that regulates gene transcription by targeting histones as well as a variety of transcription factors in the nucleus. Recently, several reports have demonstrated that numerous cytosolic proteins are also acetylated and that this modification, affecting protein activity, localization and stability has profound consequences on their cellular functions. Interestingly, most non-histone proteins targeted by acetylation are relevant for tumorigenesis. In this review, we will analyze the functional implications of lysine acetylation in different cellular compartments, and will examine our current understanding of lysine acetyltransferases family, highlighting the biological role and prognostic value of these enzymes and their substrates in cancer. The latter part of the article will address challenges and current status of molecules targeting lysine acetyltransferase enzymes in cancer therapy.

Subcellular localization of β-arrestin1 and its prognostic value in lung adenocarcinoma

β-Arrestins play important roles in cancer progression, and the subcellular localization of β-arrestin1 has been receiving increasingly more attention. Intriguingly, several studies, including some of our previous work, showed that the effects of β-arrestin1 on outcomes of cancer patients were controversial.Specimens were obtained from 133 patients with lung adenocarcinoma. Immunohistochemistry was used to detect the expression of β-arrestin1 and p300 in the collected tissues. The Kaplan-Meier analysis and Cox proportional hazards regression were used to examine the relationship between β-arrestin1 and patient survival.We found no significant association between β-arrestin1 and clinicopathological variables. The Kaplan-Meier plot showed that patients with high expression of β-arrestin1 (especially in the nucleus) had a poorer overall survival (OS) and shorter disease-free survival (DFS) (P = .026, P = .015). Additionally, high p300 expression also resulted in worse OS (P = .039). Following the univariate analysis, high expressions of nuclear β-arrestin1 and p300 were classed as poor prognostic factors for both OS (P = .016) and DFS (P = .025).The expression of β-arrestin1 in the nucleus is associated with increased malignant tendency of lung adenocarcinoma, and the predictive value of β-arrestin1 may be optimized by combining information about the expression of p300 acetyltransferase.

Expression of the EP300, TP53 and BAX genes in colorectal cancer: Correlations with clinicopathological parameters and survival

E1A binding protein P300 (EP300), tumor protein P53 (TP53) and BCL2 associated X, apoptosis regulator (BAX) genes encode proteins which cooperate to regulate important cellular processes. The present study aimed to determine the expression levels of EP300, TP53 and BAX in colorectal cancer (CRC) and to investigate their prognostic value and association with the progression of CRC. Tumor and matched unchanged colorectal tissues were collected from 121 CRC patients. Quantitative polymerase chain reaction and immunohistochemistry were used to assess the mRNA and protein levels of the studied genes. Altered expression of the studied genes in CRC tissues was observed at both the mRNA and protein levels. The depth of invasion was associated with TP53 mRNA levels and was correlated negatively with BAX mRNA expression. Moreover, a relationship between tumor location and BAX mRNA content was noted. BAX immunoreactivity was correlated positively with the intensity of p300 immunostaining and was associated with lymph node involvement and tumor-node-metastasis (TNM) disease stage. Univariate regression analysis revealed that overexpression of p53 and BAX in CRC tissues was associated with poor patient outcome. In conclusion, dysregulation of the expression of the studied genes was found to contribute to CRC pathogenesis. The association between p300 and BAX levels suggests the existence of an interdependent regulatory mechanism of their expression. Moreover, BAX expression may be regulated alternatively, in a p53-independent manner, since the lack of correlations between expression of these factors was observed.

P300 promotes migration, invasion and epithelial-mesenchymal transition in a nasopharyngeal carcinoma cell line

A previous study demonstrated that p300 is overexpressed in nasopharyngeal carcinoma (NPC), and that its expression is an independent prognostic factor. The aim of the present study is to investigate the role of p300 in human NPC development. A small hairpin (sh) RNA lentiviral expression vector targeting the p300 gene was constructed to suppress the expression of p300 in NPC cells. Knockdown of p300 was verified by reverse transcription-quantitative polymerase chain reaction and western blotting. Wound-healing, invasion, immunofluorescence and immunoprecipitation assays were performed to assess the influence of p300 on nasopharyngeal tumorigenesis and metastasis in vitro. The expression of p300 was upregulated in NPC cell lines. After knockdown of p300, the migration and invasion ability of shp300 cells were significantly inhibited (P<0.05). Furthermore, the depletion of p300 expression in NPC cell lines resulted in the upregulation of epithelial phenotype marker E-cadherin and α-catenin, and downregulation of mesenchymal phenotype markers N-cadherin and vimentin. p300 promotes epithelial-mesenchymal transition (EMT) through the acetylation of Smad2 and Smad3 in the tumor growth factor-β signaling pathway. In conclusion, p300 may be involved in the invasion and metastasis of NPC through the induction of EMT.

Aberrant lysine acetylation in tumorigenesis: Implications in the development of therapeutics

The 'language' of covalent histone modifications translates environmental and cellular cues into gene expression. This vast array of post-translational modifications on histones are more than just covalent moieties added onto a protein, as they also form a platform on which crucial cellular signals are relayed. The reversible lysine acetylation has emerged as an important post-translational modification of both histone and non-histone proteins, dictating numerous epigenetic programs within a cell. Thus, understanding the complex biology of lysine acetylation and its regulators is essential for the development of epigenetic therapeutics. In this review, we will attempt to address the complexities of lysine acetylation in the context of tumorigenesis, their role in cancer progression and emphasize on the modalities developed to target lysine acetyltransferases towards cancer treatment.

Epigenetic regulation of proliferation and invasion in hepatocellular carcinoma cells by CBP/p300 histone acetyltransferase activity

Altered epigenetic control of gene expression plays a substantial role in tumor development and progression. Accumulating studies suggest that somatic mutations of CREB binding proteins (CBP)/p300 occur in some cancer cells. CBP/p300 possess histone acetyltransferase (HAT) activity, and are involved in many cellular processes. In this study, we investigated the expression and functional role of CBP/p300 in hepatocellular carcinoma (HCC) using the specific inhibitor C646 of CBP/p300 HAT activity. We examined its effect on several apoptosis-related proteins and invasion-related genes. The results showed that CBP/p300 were highly expressed in HCC tissues and that expression of p300, but not of CBP, was strongly correlated with the malignant character of HCC. C646 inhibited proliferation of HCC cell lines in a dose dependent manner. C646 significantly augmented TRAIL-induced apoptotic sensitivity, which was accompanied by reduced levels of survivin, in HepG2, HLE and SK-HEP1 cells. C646 significantly inhibited invasion of Huh7, HLE and SK-HEP1 cells. The level of matrix metallopeptidase 15 (MMP15) mRNA expression was significantly reduced, whereas the level of laminin alpha 3 (LAMA3) and secreted phosphoprotein 1 (SPP1) mRNA expression was significantly increased in Huh7 cells following exposure to C646. In conclusion, our results suggest that CBP/p300 HAT activity has an important role in malignant transformation, proliferation, apoptotic sensitivity and invasion in HCC. CBP/p300 could be a promising therapeutic target in HCC.

Immunohistochemical evaluation of ROCK activation in invasive breast cancer

BACKGROUND

Two isoforms of Rho-associated coiled-coil kinase (ROCK), ROCKI and ROCKII, play an important role in many cellular processes. Despite the accumulating evidence showing that ROCK could be a potential cancer therapeutic target, the relevant tumor types to ROCK activation are not well clarified. The aim of this study was to evaluate the ROCK activation status in different tumor types of breast cancer.

RESULTS

We evaluated the immunoreactivities of phosphorylation-specific antibodies of ROCKI and ROCKII to inform their kinase activation in 275 of breast carcinoma tissues, including 56 of carcinoma in situ, 116 of invasive carcinoma, and 103 of invasive carcinoma with metastasis. ROCKII activation signal detected in nucleus was significantly correlated with tumor metastasis, while ROCKI and cytosolic ROCKII activation signals made no significant difference in that metastasis. Furthermore, nuclear ROCKII activation signal was associated with poor clinical outcome and correlated with late tumor stage, low expression of estrogen receptor (ER) and progesterone receptor (PR), overexpression of human epidermal growth factor receptor 2 (HER2) and high Ki67 labeling index.

CONCLUSIONS

Nuclear ROCKII activation signal might contribute to the tumor metastasis in breast cancer. Differences in ROCK activation that underlie the phenotypes of breast cancer could enhance our understanding for the use of ROCK inhibitors in cancer therapy.

KATs in cancer: functions and therapies

Post-translational acetylation of lysines is most extensively studied in histones, but this modification is also found in many other proteins and is implicated in a wide range of biological processes in both the cell nucleus and the cytoplasm. Like phosphorylation, acetylation patterns and levels are often altered in cancer, therefore small molecule inhibition of enzymes that regulate acetylation and deacetylation offers much potential for inhibiting cancer cell growth, as does disruption of interactions between acetylated residues and ‘reader’ proteins. For more than a decade now, histone deacetylase (HDAC) inhibitors have been investigated for their ability to increase acetylation and promote expression of tumor suppressor genes. However, emerging evidence suggests that acetylation can also promote cancer, in part by enhancing the functions of oncogenic transcription factors. In this review we focus on how acetylation of both histone and non-histone proteins may drive cancer, and we will discuss the implications of such changes on how patients are assigned to therapeutic agents. Finally, we will explore what the future holds in the design of small molecule inhibitors for modulation of levels or functions of acetylation states.

Serglycin expression: An independent marker of distant metastases in nasopharyngeal carcinoma

BACKGROUND

Nasopharyngeal carcinoma (NPC) has a high propensity for metastasis. The purpose of this study was for us to determine whether serglycin expression can be used to predict distant metastases.

METHODS

Serglycin expression of tumor tissue of 112 patients with NPC was assessed based on percentage of tumor cells expressing serglycin, staining intensity, percentage of tumor-infiltrated lymphocyte (TIL) expressing serglycin and TIL-staining intensity.

RESULTS

Risk factors for distant metastases include sex, smoking status, tumor intensity, and TIL percentage for serglycin. The odds of distant metastases was 4.13 and 0.18 in patients with strong tumor intensity and >50% TIL percentage, respectively. Based on a nomogram incorporating predictors, patients were stratified into 2 prognostic groups. The proportion of distant metastases in the high-risk group (strong tumor intensity and ≤50% TIL percentage) was 78% versus 19% in the low risk group (p < .001).

CONCLUSION

Patients with NPC with tumors showing strong tumor intensity and low TIL percentage with serglycin may be at high risk for distant metastases.

The role of p300 in the tumor progression of oral squamous cell carcinoma

BACKGROUND

EP300 gene encoding p300 is a candidate tumor suppressor gene. This study investigated p300 expression and gene alteration in oral squamous cell carcinoma (OSCC) specimens to assess its role in OSCC development.

METHODS

Genomic DNA extracted from 13 human OSCC cell lines and 40 OSCC patient specimens was subjected to methylation-specific PCR and exon sequencing. Immunohistochemical staining with primary antibodies against p300 and p53 was performed in 48 patients with OSCC. We analyzed the association between the data and clinicopathological factors of OSCC patients.

RESULTS

Methylation-specific PCR revealed that the EP300 promoter region was not hypermethylated in OSCC. Only one cell line demonstrated a point mutation at exon 31. On immunohistochemical examination, patients with metastatic lymph nodes (P = 0.009) and advanced clinical stage (P = 0.046) tended to show increased expression of p300. There was no statistically significant relationship between p300 expression and p53 accumulation in OSCC tissue samples. Patient survival was not correlated with p300 expression.

CONCLUSIONS

EP300 is not a tumor suppressor gene because there was neither epigenetic inactivation of the gene nor a mutation resulting in functional impairment. Based on p300 overexpression and its association with clinical factors in patients with OSCC, it is likely that p300 itself or one of its target genes plays a key role in the aggressive phenotypes of OSCC.

Prognostic impact of p300 expression in patients with colorectal cancer

BACKGROUND

This study evaluated the expression of p300 in colorectal cancer, its relationship with clinicopathological characteristics, and its potential prognostic significance.

METHODS

The expression of p300 was measured using immunohistochemistry in tumors and surrounding normal mucosa from 199 patients with primary colorectal cancer. The patients were followed for a median period of 83 months.

RESULTS

Nuclear p300 expression was significantly associated with histology (P = 0.031) and lymph node involvement (P = 0.019). When the low and high p300 groups were subdivided according to tumor location, the disease-free survival rate differed only for the patients with colon cancer (P = 0.008). In addition, the disease-free survival significantly differed with p300 expression for stage II disease (P = 0.038), but not for stage III disease. Multivariate analysis revealed that lymph node involvement (P = 0.014) and p300 expression (P = 0.032) were independent predictors of overall survival in adenocarcinomas.

CONCLUSION

The overexpression of p300 may be an independent favorable prognostic factor for disease-free survival in patients with colorectal cancer.

S6K2: The Neglected S6 Kinase Family Member

S6 kinase 2 (S6K2) is a member of the AGC kinases super-family. Its closest homolog, S6K1, has been extensively studied along the years. However, due to the belief in the community that the high degree of identity between these two isoforms would translate in essentially identical biological functions, S6K2 has been largely neglected. Nevertheless, recent research has clearly highlighted that these two proteins significantly differ in their roles in vitro as well as in vivo. These findings are significant to our understanding of S6 kinase signaling and the development of therapeutic strategies for several diseases including cancer. Here, we will focus on S6K2 and review the protein–protein interactions and specific substrates that determine the selective functions of this kinase.

The E3 ubiquitin ligase Itch regulates tumor suppressor protein RASSF5/NORE1 stability in an acetylation-dependent manner

Ras association (RalGDS/AF-6) domain family member RASSF5 is a non-enzymatic RAS effector super family protein, known to be involved in cell growth regulation. Expression of RASSF5 is found to be extinguished by promoter hypermethylation in different human cancers, and its ectopic expression suppresses cell proliferation and tumorigenicity. Interestingly, this role in tumorigenesis has been confounded by the fact that regulation at molecular level remains unclear and many transformed cells actually display elevated RASSF5 expression. Here, we demonstrate that E3 ubiquitin ligase Itch is a unique binding partner of RASSF5. Itch can interact with PPxY motif in RASSF5 both in vivo and in vitro through its WW domains. Importantly, the overexpression of Itch induces RASSF5 degradation by poly-ubiquitination via 26S proteasome pathway. In addition, our results indicate that the elevated levels of RASSF5 found in tumor cells due to acetylation, which restricts its binding to Itch and results in a more stable inert protein. Inhibition of RASSF5 acetylation permits its interaction with Itch and provokes proteasomal degradation. These data suggest that apart from promoter methylation, hyperacetylation could also be downregulating RASSF5 function in different human cancer. Finally, results from functional assays suggest that the overexpression of wild type, not the ligase activity defective Itch negatively regulate RASSF5-mediated G1 phase transition of cell cycle as well as apoptosis, suggesting that Itch alone is sufficient to alter RASSF5 function. Collectively, the present investigation identifies a HECT class E3 ubiquitin ligase Itch as a unique negative regulator of RASSF5, and suggests the possibility that acetylation as a potential therapeutic target for human cancer.

BRMS1 suppresses lung cancer metastases through an E3 ligase function on histone acetyltransferase p300

The mechanisms through which the metastasis suppressor gene BRMS1 functions are poorly understood. Herein, we report the identification of a previously undescribed E3 ligase function of BRMS1 on the histone acetyltransferase p300. BRMS1 induces polyubiquitination of p300, resulting in its proteasome-mediated degradation. We identify BRMS1 as the first eukaryote structural mimic of the bacterial IpaH E3 ligase family and establish that the evolutionarily conserved CXD motif located in BRMS1 is responsible for its E3 ligase function. Mutation of this E3 ligase motif not only abolishes BRMS1-induced p300 polyubiquitination and degradation, but importantly, dramatically reduces the metastasis suppressor function of BRMS1 in both in vitro and in vivo models of lung cancer metastasis.

High expression levels of COX-2 and P300 are associated with unfavorable survival in laryngeal squamous cell carcinoma

In order to provide a basis for clinical treatment decisions, we explored whether there was a correlation between the expression of COX-2 and P300 and clinical factors in a group of patients with laryngeal squamous cell carcinoma (LSCC). A retrospective analysis of clinicopathological data was conducted in 80 patients with LSCC who presented between January 1997 and December 1998. An immunohistochemistry tissue microarray was conducted of 80 surgically resected LSCC and 20 adjacent normal tissue specimens. Survival analysis and Kaplan–Meier curves were used to compare the effects of clinicopathological factors on survival. The Cox model was applied for multivariate analysis. The expression level of COX-2/P300 in LSCC tissues and adjacent normal tissues were 47.5/50.0 versus 0.0/15.0 %. The expression of COX-2 and P300 was correlated with higher T category, N category, clinical staging, histological grade and recurrence (P < 0.05). P300 expression was correlated with COX-2 expression (P < 0.05). Univariate survival analysis showed that P300, COX-2, N category, clinical staging and recurrence factors were closely correlated with unfavorable survival (P < 0.05). Multivariate analysis showed that COX-2 expression, histological grade and recurrence were independent prognostic factors for LSCC. High expression levels of COX-2 and P300 indicated poor survival outcomes for patients with LSCC.