Regulation of the p14ARF-Mdm2-p53 pathway: an overview in breast cancer

Breast Cancer Chemoresistance: Insights into the Regulatory Role of lncRNA

Long noncoding RNAs (lncRNAs) are a subclass of noncoding RNAs composed of more than 200 nucleotides without the ability to encode functional proteins. Given their involvement in critical cellular processes such as gene expression regulation, transcription, and translation, lncRNAs play a significant role in organism homeostasis. Breast cancer (BC) is the second most common cancer worldwide and evidence has shown a relationship between aberrant lncRNA expression and BC development. One of the main obstacles in BC control is multidrug chemoresistance, which is associated with the deregulation of multiple mechanisms such as efflux transporter activity, mitochondrial metabolism reprogramming, and epigenetic regulation as well as apoptosis and autophagy. Studies have shown the involvement of a large number of lncRNAs in the regulation of such pathways. However, the underlying mechanism is not clearly elucidated. In this review, we present the principal mechanisms associated with BC chemoresistance that can be directly or indirectly regulated by lncRNA, highlighting the importance of lncRNA in controlling BC chemoresistance. Understanding these mechanisms in deep detail may interest the clinical outcome of BC patients and could be used as therapeutic targets to overcome BC therapy resistance.

ZBTB7A as a novel vulnerability in neuroendocrine prostate cancer

Neuroendocrine prostate cancer (NEPC) is a highly aggressive subtype of prostate cancer. NEPC is characterized by the loss of androgen receptor (AR) signaling and transdifferentiation toward small-cell neuroendocrine (SCN) phenotypes, which results in resistance to AR-targeted therapy. NEPC resembles other SCN carcinomas clinically, histologically and in gene expression. Here, we leveraged SCN phenotype scores of various cancer cell lines and gene depletion screens from the Cancer Dependency Map (DepMap) to identify vulnerabilities in NEPC. We discovered ZBTB7A, a transcription factor, as a candidate promoting the progression of NEPC. Cancer cells with high SCN phenotype scores showed a strong dependency on RET kinase activity with a high correlation between RET and ZBTB7A dependencies in these cells. Utilizing informatic modeling of whole transcriptome sequencing data from patient samples, we identified distinct gene networking patterns of ZBTB7A in NEPC versus prostate adenocarcinoma. Specifically, we observed a robust association of ZBTB7A with genes promoting cell cycle progression, including apoptosis regulating genes. Silencing ZBTB7A in a NEPC cell line confirmed the dependency on ZBTB7A for cell growth via suppression of the G1/S transition in the cell cycle and induction of apoptosis. Collectively, our results highlight the oncogenic function of ZBTB7A in NEPC and emphasize the value of ZBTB7A as a promising therapeutic strategy for targeting NEPC tumors.

RUNX3 Meets the Ubiquitin-Proteasome System in Cancer

RUNX3 is a transcription factor with regulatory roles in cell proliferation and development. While largely characterized as a tumor suppressor, RUNX3 can also be oncogenic in certain cancers. Many factors account for the tumor suppressor function of RUNX3, which is reflected by its ability to suppress cancer cell proliferation after expression-restoration, and its inactivation in cancer cells. Ubiquitination and proteasomal degradation represent a major mechanism for the inactivation of RUNX3 and the suppression of cancer cell proliferation. On the one hand, RUNX3 has been shown to facilitate the ubiquitination and proteasomal degradation of oncogenic proteins. On the other hand, RUNX3 can be inactivated through the ubiquitin-proteasome system. This review encapsulates two facets of RUNX3 in cancer: how RUNX3 suppresses cell proliferation by facilitating the ubiquitination and proteasomal degradation of oncogenic proteins, and how RUNX3 is degraded itself through interacting RNA-, protein-, and pathogen-mediated ubiquitination and proteasomal degradation.

An integrated investigation of structural and pathway alteration caused by PIK3CA and TP53 mutations identified in cfDNA of metastatic breast cancer

In peripheral blood, cell-free DNA (cfDNA) contains circulating tumor DNA (ctDNA), which indicates molecular abnormalities in metastatic breast tumor tissue. The sequencing of cfDNA of Metastatic Breast Cancer (MBC) patients allows assessment of therapy response and noninvasive treatment. In the proposed study, clinically significant alterations in PIK3CA and TP53 genes associated with MBC resulting in a missense substitution of His1047Arg and Arg282Trp from an next-generation sequencing-based multi-gene panel were reported in a cfDNA of a patient with MBC. To investigate the impact of the reported mutation, we used molecular docking, molecular dynamics simulation, network analysis, and pathway analysis. Molecular Docking analysis determined the distinct binding pattern revealing H1047R-ATP complex has a higher number of Hydrogen bonds (H-bonds) and binding affinity with a slight difference compared to the PIK3CA-ATP complex. Following, molecular dynamics simulation for 200 ns, of which H1047R-ATP complex resulted in the instability of PIK3CA. Similarly, for TP53 mutant R282W, the zinc-free state (apo) and zinc-bounded (holo) complexes were investigated for conformational change between apo and holo complexes, of which the holo complex mutant R282W was unstable. To validate the conformational change of PIK3CA and TP53, 80% mutation of H1047R in the kinase domain of p110α expressed ubiquitously in PIK3CA protein that alters PI3K pathway, while R282W mutation in DNA binding helix (H2) region of P53 protein inhibits the transcription factor in P53 pathway causing MBC. According to our findings, the extrinsic (hypoxia, oxidative stress, and acidosis); intrinsic factors (MYC amplification) in PIK3CA and TP53 mutations will provide potential insights for developing novel therapeutic methods for MBC therapy.

Transcription profiling of feline mammary carcinomas and derived cell lines reveals biomarkers and drug targets associated with metabolic and cell cycle pathways

The molecular heterogeneity of feline mammary carcinomas (FMCs) represents a prognostic and therapeutic challenge. RNA-Seq-based comparative transcriptomic profiling serves to identify recurrent and exclusive differentially expressed genes (DEGs) across sample types and molecular subtypes. Using mass-parallel RNA-Seq, we identified DEGs and performed comparative function-based analysis across 15 tumours (four basal-like triple-negative [TN], eight normal-like TN, and three luminal B fHER2 negative [LB fHER2-]), two cell lines (CL, TiHo-0906, and TiHo-1403) isolated from the primary tumours (LB fHER2-) of two cats included in this study, and 13 healthy mammary tissue controls. DEGs in tumours were predominantly upregulated; dysregulation of CLs transcriptome was more extensive, including mostly downregulated genes. Cell-cycle and metabolic-related DEGs were upregulated in both tumours and CLs, including therapeutically-targetable cell cycle regulators (e.g. CCNB1, CCNB2, CDK1, CDK4, GTSE1, MCM4, and MCM5), metabolic-related genes (e.g. FADS2 and SLC16A3), heat-shock proteins (e.g. HSPH1, HSP90B1, and HSPA5), genes controlling centrosome disjunction (e.g. RACGAP1 and NEK2), and collagen molecules (e.g. COL2A1). DEGs specifically upregulated in basal-like TN tumours were involved in antigen processing and presentation, in normal-like TN tumours encoded G protein-coupled receptors (GPCRs), and in LB fHER2- tumours were associated with lysosomes, phagosomes, and endosomes formation. Downregulated DEGs in CLs were associated with structural and signalling cell surface components. Hence, our results suggest that upregulation of genes enhancing proliferation and metabolism is a common feature among FMCs and derived CLs. In contrast, the dissimilarities observed in dysregulation of membrane components highlight CLs' disconnection with the tumour microenvironment. Furthermore, recurrent and exclusive DEGs associated with dysregulated pathways might be useful for the development of prognostically and therapeutically-relevant targeted panels.

The use of adenoviral vectors in gene therapy and vaccine approaches

Adenovirus was first identified in the 1950s and since then this pathogenic group of viruses has been explored and transformed into a genetic transfer vehicle. Modification or deletion of few genes are necessary to transform it into a conditionally or non-replicative vector, creating a versatile tool capable of transducing different tissues and inducing high levels of transgene expression. In the early years of vector development, the application in monogenic diseases faced several hurdles, including short-term gene expression and even a fatality. On the other hand, an adenoviral delivery strategy for treatment of cancer was the first approved gene therapy product. There is an increasing interest in expressing transgenes with therapeutic potential targeting the cancer hallmarks, inhibiting metastasis, inducing cancer cell death or modulating the immune system to attack the tumor cells. Replicative adenovirus as vaccines may be even older and date to a few years of its discovery, application of non-replicative adenovirus for vaccination against different microorganisms has been investigated, but only recently, it demonstrated its full potential being one of the leading vaccination tools for COVID-19. This is not a new vector nor a new technology, but the result of decades of careful and intense work in this field.

Identification of cuproptosis-related subtypes, cuproptosis-related gene prognostic index in hepatocellular carcinoma

Cuproptosis is a novel form of cell death, correlated with the tricarboxylic acid (TCA) cycle. However, the metabolic features and the benefit of immune checkpoint inhibitor (ICI) therapy based on cuproptosis have not yet been elucidated in Hepatocellular carcinoma (HCC). First, we identified and validated three cuproptosis subtypes based on 10 cuproptosis-related genes (CRGs) in HCC patients. We explored the correlation between three cuproptosis subtypes and metabolism-related pathways. Besides, a comprehensive immune analysis of three cuproptosis subtypes was performed. Then, we calculated the cuproptosis-related gene prognostic index (CRGPI) score for predicting prognosis and validated its predictive capability by Decision curve analysis (DCA). We as well explored the benefit of ICI therapy of different CRGPI subgroups in two anti-PD1/PD-L1 therapy cohorts (IMvigor210 cohort and GSE176307). Finally, we performed the ridge regression algorithm to calculate the IC50 value for drug sensitivity and Gene set enrichment analysis (GSEA) analysis to explore the potential mechanism. We found that cluster A presented a higher expression of FDX1 and was correlated with metabolism, glycolysis, and TCA cycle pathways, compared with the other two clusters. HCC patients with high CRGPI scores had a worse OS probability, and we further found that the CRGPI-high group had high expression of PD1/PDL1, TMB, and better response (PR/CR) to immunotherapy in the IMvigor210 cohort and GSE176307. These findings highlight the importance of CRGPI serving as a potential biomarker for both prognostic and immunotherapy for HCC patients. Generally, our results provide novel insights about cuproptosis into immune therapeutic strategies.

Synthesis and Characterization of Plumbagin S-Allyl Cysteine Ester: Determination of Anticancer Activity In Silico and In Vitro

In recent years, derivatives of natural compounds are synthesized to increase the bioavailability, pharmacology, and pharmacokinetics properties. The naphthoquinone, plumbagin (PLU), is well known for its anticancer activity. However, the clinical use of PLU is hindered due to its toxicity. Previous reports have shown that modification of PLU at 5'-hydroxyl group has reduced its toxicity towards normal cell line. In accordance, in the present study, 5'-hydroxyl group of PLU was esterified with S-allyl cysteine (SAC) to obtain PLU-SAC ester. The drug-likeness of PLU-SAC was understood by in silico ADME analysis. PLU-SAC was characterized by UV-visible spectroscopy, mass spectroscopy, and nuclear magnetic resonance (NMR) spectroscopy. Molecular docking and dynamics simulation analysis revealed the interaction of PLU-SAC with proteins of interest in cancer therapy such as human estrogen receptor α, tumor protein p53 negative regulator mouse double minute 2, and cyclin-dependent kinase 2. MMGBSA calculation showed the favorable binding energy which in turn demonstrated the stable binding of PLU-SAC with these proteins. PLU-SAC showed apoptosis in breast cancer cell line (MCF-7) by inducing oxidative stress, disturbing mitochondrial function, arresting cells at G1 phase of cell cycle, and initiating DNA fragmentation. However, PLU-SAC did not show toxicity towards normal Vero cell line. PLU-SAC was synthesized and structurally characterized, and its anticancer activity was determined by in silico and in vitro analysis.

An Unanticipated Modulation of Cyclin-Dependent Kinase Inhibitors: The Role of Long Non-Coding RNAs

It is now definitively established that a large part of the human genome is transcribed. However, only a scarce percentage of the transcriptome (about 1.2%) consists of RNAs that are translated into proteins, while the large majority of transcripts include a variety of RNA families with different dimensions and functions. Within this heterogeneous RNA world, a significant fraction consists of sequences with a length of more than 200 bases that form the so-called long non-coding RNA family. The functions of long non-coding RNAs range from the regulation of gene transcription to the changes in DNA topology and nucleosome modification and structural organization, to paraspeckle formation and cellular organelles maturation. This review is focused on the role of long non-coding RNAs as regulators of cyclin-dependent kinase inhibitors’ (CDKIs) levels and activities. Cyclin-dependent kinases are enzymes necessary for the tuned progression of the cell division cycle. The control of their activity takes place at various levels. Among these, interaction with CDKIs is a vital mechanism. Through CDKI modulation, long non-coding RNAs implement control over cellular physiology and are associated with numerous pathologies. However, although there are robust data in the literature, the role of long non-coding RNAs in the modulation of CDKIs appears to still be underestimated, as well as their importance in cell proliferation control.

Cancer cells with defective RB and CDKN2A are resistant to the apoptotic effects of rapamycin

Inhibition of mammalian target of rapamycin complex 1 (mTORC1) with rapamycin in the absence of transforming growth factor-β (TGFβ) signaling induces apoptosis in many cancer cell lines. In the presence of TGFβ, rapamycin induces G₁ cell cycle arrest; however, in the absence of TGFβ, cells do not arrest in G₁ and progress into S-phase where rapamycin is cytotoxic rather than cytostatic. However, we observed that DU145 prostate and NCI-H2228 lung cancer cells were resistant to the cytotoxic effect of rapamycin. Of interest, the rapamycin-resistant DU145 and NCI-H2228 cells have mutations in the RB and CDKN2A tumor suppressor genes. The gene products of RB and CDKN2A (pRb and p14^ARF) suppress E2F family transcription factors that promote cell cycle progression from G₁ into S. Restoration of wild type RB or inhibition of E2F activity in DU145 and NCI-H2228 cells led to rapamycin sensitivity. These data provide evidence that the combination of mutant RB and mutant CDKN2A in cancer cells leads to rapamycin resistance, which has implications for precision medicine approaches to anti-cancer therapies.

Genetic and methylation status of CDKN2A (p14ARF/p16INK4A) and TP53 genes in recurrent respiratory papillomatosis

Recurrent respiratory papillomatosis (RRP) is a rare and chronic disease affecting the upper airway with papillomatous lesions caused by the human papillomavirus (HPV) infection, especially HPV-6 and/or HPV-11 types. Little is known about the genetic and epigenetic drivers in RRP pathophysiology. For this purpose, we analyzed 27 papillomatous lesions from patients with RRP to evaluate somatic mutations and methylation status in CDKN2A (p14^ARF/p16^INK4A) and TP53, which are key tumor suppressor genes for the cell cycle control. Sanger sequencing analysis revealed one somatic mutation in TP53 (c.733_734insA) and four mutations in CDKN2A (c.-30G > T, c.29_30insA, c.69delT, and c.300C > A). These mutations were observed in 10 patients, 6 of which carried double mutation. Furthermore, 50% (5/10) of these patients carrying somatic mutations had RRP severity, representing 62.5% (5/8) of the severity cases in this study, albeit no significant association was found between somatic mutations and disease severity. Methylation-specific polymerase chain reaction assays revealed p14^ARF promoter hypermethylation in 100% of cases, followed by TP53 (96.3%) and p16^INK4A (55.6%), suggesting the influence of HPV in the DNA methylation machinery. In conclusion, somatic mutations were not common events identified in patients with RRP. However, epigenetic modulation by high methylation rates, particularly for the p14^ARF/TP53 pathway, seems to be in the course of RRP development.

Novel Methylation Biomarkers for Colorectal Cancer Prognosis

Colorectal cancer (CRC) comprises the third most common cancer worldwide and the second regarding number of deaths. In order to make a correct and early diagnosis to predict metastasis formation, biomarkers are an important tool. Although there are multiple signaling pathways associated with cancer progression, the most recognized are the MAPK pathway, p53 pathway, and TGF-β pathway. These pathways regulate many important functions in the cell, such as cell cycle regulation, proliferation, differentiation, and metastasis formation, among others. Changes in expression in genes belonging to these pathways are drivers of carcinogenesis. Often these expression changes are caused by mutations; however, epigenetic changes, such as DNA methylation, are increasingly acknowledged to play a role in the deregulation of oncogenic genes. This makes DNA methylation changes an interesting biomarkers in cancer. Among the newly identified biomarkers for CRC metastasis INHBB, SMOC2, BDNF, and TBRG4 are included, all of which are highly deregulated by methylation and closely associated with metastasis. The identification of such biomarkers in metastasis of CRC may allow a better treatment and early identification of cancer formation in order to perform better diagnostics and improve the life expectancy.

The Post-Translational Regulation of Epithelial-Mesenchymal Transition-Inducing Transcription Factors in Cancer Metastasis

Epithelial-mesenchymal transition (EMT) is generally observed in normal embryogenesis and wound healing. However, this process can occur in cancer cells and lead to metastasis. The contribution of EMT in both development and pathology has been studied widely. This transition requires the up- and down-regulation of specific proteins, both of which are regulated by EMT-inducing transcription factors (EMT-TFs), mainly represented by the families of Snail, Twist, and ZEB proteins. This review highlights the roles of key EMT-TFs and their post-translational regulation in cancer metastasis.

Regulation of Canonical Oncogenic Signaling Pathways in Cancer via DNA Methylation

Disruption of signaling pathways that plays a role in the normal development and cellular homeostasis may lead to the dysregulation of cellular signaling and bring about the onset of different diseases, including cancer. In addition to genetic aberrations, DNA methylation also acts as an epigenetic modifier to drive the onset and progression of cancer by mediating the reversible transcription of related genes. Although the role of DNA methylation as an alternative driver of carcinogenesis has been well-established, the global effects of DNA methylation on oncogenic signaling pathways and the presentation of cancer is only emerging. In this article, we introduced a differential methylation parsing pipeline (MethylMine) which mined for epigenetic biomarkers based on feature selection. This pipeline was used to mine for biomarkers, which presented a substantial difference in methylation between the tumor and the matching normal tissue samples. Combined with the Data Integration Analysis for Biomarker discovery (DIABLO) framework for machine learning and multi-omic analysis, we revisited the TCGA DNA methylation and RNA-Seq datasets for breast, colorectal, lung, and prostate cancer, and identified differentially methylated genes within the NRF2-KEAP1/PI3K oncogenic pathway, which regulates the expression of cytoprotective genes, that serve as potential therapeutic targets to treat different cancers.

Apigenin as Tumor Suppressor in Cancers: Biotherapeutic Activity, Nanodelivery, and Mechanisms With Emphasis on Pancreatic Cancer

Pancreatic cancer is the most lethal malignancy of the gastrointestinal tract. Due to its propensity for early local and distant spread, affected patients possess extremely poor prognosis. Currently applied treatments are not effective enough to eradicate all cancer cells, and minimize their migration. Besides, these treatments are associated with adverse effects on normal cells and organs. These therapies are not able to increase the overall survival rate of patients; hence, finding novel adjuvants or alternatives is so essential. Up to now, medicinal herbs were utilized for therapeutic goals. Herbal-based medicine, as traditional biotherapeutics, were employed for cancer treatment. Of them, apigenin, as a bioactive flavonoid that possesses numerous biological properties (e.g., anti-inflammatory and anti-oxidant effects), has shown substantial anticancer activity. It seems that apigenin is capable of suppressing the proliferation of cancer cells via the induction of cell cycle arrest and apoptosis. Besides, apigenin inhibits metastasis via down-regulation of matrix metalloproteinases and the Akt signaling pathway. In pancreatic cancer cells, apigenin sensitizes cells in chemotherapy, and affects molecular pathways such as the hypoxia inducible factor (HIF), vascular endothelial growth factor (VEGF), and glucose transporter-1 (GLUT-1). Herein, the biotherapeutic activity of apigenin and its mechanisms toward cancer cells are presented in the current review to shed some light on anti-tumor activity of apigenin in different cancers, with an emphasis on pancreatic cancer.

IU1 suppresses proliferation of cervical cancer cells through MDM2 degradation

Previous studies have demonstrated that the antitumor potential of IU1 (a pharmacological compound), which was mediated by selective inhibition of proteasome-associated deubiquitinase ubiquitin-specific protease 14 (USP14). However, the underlying molecular mechanisms remain elusive. It has been well established that mdm2 (Murine double minute 2) gene was amplified and/or overexpressed in a variety of human neoplasms, including cervical cancer. Furthermore, MDM2 is critical to cervical cancer development and progression. Relatively studies have reported that USP15 and USP7 stabilized MDM2 protein levels by removing its ubiquitin chain. In the current study, we studied the cell proliferation status after IU1 treatment and the USP14-MDM2 protein interaction in cervical cancer cells. This study experimentally revealed that IU1 treatment reduced MDM2 protein expression in HeLa cervical cancer cells, along with the activation of autophagy-lysosomal protein degradation and promotion of ubiquitin-proteasome system (UPS) function, thereby blocked G0/G1 to S phase transition, decreased cell growth and triggered cell apoptosis. Thus, these results indicate that IU1 treatment simultaneously targets two major intracellular protein degradation systems, ubiquitin-proteasome and autophagy-lysosome systems, which leads to MDM2 degradation and contributes to the antitumor effect of IU1.

The Expression of P53, MDM2, c-myc, and P14ARF Genes in Newly Diagnosed Acute Lymphoblastic Leukemia Patients

The treatment response of acute lymphoblastic leukemia (ALL) depends on the percentage of lymphoblasts, cytogenetic aberrations, and altered gene expression. The analysis of the gene expression is applicable for determination of risk stratification and prognosis of cancers. c-MYC, P14^ARF, MDM2, and P53 play a vital role in cell survival through a functional network. This study aimed to investigate the expression of these genes, also their correlation with immunophenotypic subtypes of ALL and the percentage of blasts. Real-time PCR was performed for the expression analysis of P53, MDM2, c-MYC, and P14^ARF in the bone marrow or peripheral blood samples of 52 ALL patients and 13 normal samples as controls. The morphological analysis and flow cytometry were carried out to examine the phenotypes and percentage of lymphoblasts. The decreased expression levels of P53 and MDM2 were seen in ALL patients compared with control group. In T cell subgroup of ALL the expression of P14^ARF gene was more decreased among other subgroups. The expression of MDM2 was decreased in ALL patients who were under the age of 16. Based on our study, the interaction between P53 and MDM2 might be more complex and different from reports published in previous studies. Our findings showed that MDM2 is not negatively correlated with P53, at least in our samples. It can be very effective on the current and future studies to use different techniques for analysis of genome, transcriptome, and proteome in definitive risk stratification and prognosis determination.

Emerging role of ZBTB7A as an oncogenic driver and transcriptional repressor

ZBTB7A is a member of the POK family of transcription factors that possesses a POZ-domain at the N-terminus and Krüppel-like zinc-finger at the c-terminus. ZBTB7A was initially isolated as a protein that binds to the inducer of the short transcript of HIV-1 virus TAT gene promoter. The protein forms a homodimer through protein-protein interaction via the N-terminus POZ-domains. ZBTB7A typically binds to the DNA elements through its zinc-finger domains and represses transcription both by modification of the chromatin organization and through the direct recruitment of transcription factors to gene regulatory regions. ZBTB7A is involved in several fundamental biological processes including cell proliferation, differentiation, and development. It also participates in hematopoiesis, adipogenesis, chondrogenesis, cellular metabolism and alternative splicing of BCLXL, DNA repair, development of oligodendrocytes, osteoclast and unfolded protein response. Aberrant ZBTB7A expression promotes oncogenic transformation and tumor progression, but also maintains a tumor suppressive role depending on the type and genetic context of cancer. In this comprehensive review we provide information about the structure, function, targets, and regulators of ZBTB7A and its role as an oncogenic driver and transcriptional repressor in various human diseases.

Targeting the DNA Damage Response for the Treatment of High Risk Neuroblastoma

Despite intensive multimodal therapy, the survival rate for high risk neuroblastoma (HR-NB) remains <50%. Most cases initially respond to treatment but almost half will subsequently relapse with aggressive treatment resistant disease. Novel treatments exploiting the molecular pathology of NB and/or overcoming resistance to current genotoxic therapies are needed before survival rates can significantly improve. DNA damage response (DDR) defects are frequently observed in HR-NB including allelic deletion and loss of function mutations in key DDR genes, oncogene induced replication stress and cell cycle checkpoint dysfunction. Exploiting defects in the DDR has been a successful treatment strategy in some adult cancers. Here we review the genetic features of HR-NB which lead to DDR defects and the emerging molecular targeting agents to exploit them.

Ubiquitin-Regulated Cell Proliferation and Cancer

Ubiquitin ligases (E3) play a crucial role in the regulation of different cellular processes such as proliferation and differentiation via recognition, interaction, and ubiquitination of key cellular proteins in a spatial and temporal regulated manner. The type of ubiquitin chain formed determines the fate of the substrates. The ubiquitinated substrates can be degraded by the proteasome, display altered subcellular localization, or can suffer modifications on their interaction with functional protein complexes. Deregulation of E3 activities is frequently found in various human pathologies, including cancer. The illegitimated or accelerated degradation of oncosuppressive proteins or, inversely, the abnormally high accumulation of oncoproteins, contributes to cell proliferation and transformation. Anomalies in protein abundance may be related to mutations that alter the direct or indirect recognition of proteins by the E3 enzymes or alterations in the level of expression or activity of ubiquitin ligases. Through a few examples, we illustrate here the complexity and diversity of the molecular mechanisms related to protein ubiquitination involved in cell cycle regulation. We will discuss the role of ubiquitin-dependent degradation mediated by the proteasome, the role of non-proteolytic ubiquitination during cell cycle progression, and the consequences of this deregulation on cellular transformation. Finally, we will highlight the novel opportunities that arise from these studies for therapeutic intervention.

Estrogen receptor α promotes Cav1.2 ubiquitination and degradation in neuronal cells and in APP/PS1 mice

Cav1.2 is the pore-forming subunit of L-type voltage-gated calcium channel (LTCC) that plays an important role in calcium overload and cell death in Alzheimer's disease. LTCC activity can be regulated by estrogen, a sex steroid hormone that is neuroprotective. Here, we investigated the potential mechanisms in estrogen-mediated regulation of Cav1.2 protein. We found that in cultured primary neurons, 17β-estradiol (E2) reduced Cav1.2 protein through estrogen receptor α (ERα). This effect was offset by a proteasomal inhibitor MG132, indicating that ubiquitin-proteasome system was involved. Consistently, the ubiquitin (UB) mutant at lysine 29 (K29R) or the K29-deubiquitinating enzyme TRAF-binding protein domain (TRABID) attenuated the effect of ERα on Cav1.2. We further identified that the E3 ligase Mdm2 (double minute 2 protein) and the PEST sequence in Cav1.2 protein played a role, as Mdm2 overexpression and the membrane-permeable PEST peptides prevented ERα-mediated Cav1.2 reduction, and Mdm2 overexpression led to the reduced Cav1.2 protein and the increased colocalization of Cav1.2 with ubiquitin in cortical neurons in vivo. In ovariectomized (OVX) APP/PS1 mice, administration of ERα agonist PPT reduced cerebral Cav1.2 protein, increased Cav1.2 ubiquitination, and improved cognitive performances. Taken together, ERα-induced Cav1.2 degradation involved K29-linked UB chains and the E3 ligase Mdm2, which might play a role in cognitive improvement in OVX APP/PS1 mice.

The Roles of p53 in Mitochondrial Dynamics and Cancer Metabolism: The Pendulum between Survival and Death in Breast Cancer?

Cancer research has been heavily geared towards genomic events in the development and progression of cancer. In contrast, metabolic regulation, such as aberrant metabolism in cancer, is poorly understood. Alteration in cellular metabolism was once regarded simply as a consequence of cancer rather than as playing a primary role in cancer promotion and maintenance. Resurgence of cancer metabolism research has identified critical metabolic reprogramming events within biosynthetic and bioenergetic pathways needed to fulfill the requirements of cancer cell growth and maintenance. The tumor suppressor protein p53 is emerging as a key regulator of metabolic processes and metabolic reprogramming in cancer cells&mdash;balancing the pendulum between cell death and survival. This review provides an overview of the classical and emerging non-classical tumor suppressor roles of p53 in regulating mitochondrial dynamics: mitochondrial engagement in cell death processes in the prevention of cancer. On the other hand, we discuss p53 as a key metabolic switch in cellular function and survival. The focus is then on the conceivable roles of p53 in breast cancer metabolism. Understanding the metabolic functions of p53 within breast cancer metabolism will, in due course, reveal critical metabolic hotspots that cancers advantageously re-engineer for sustenance. Illustration of these events will pave the way for finding novel therapeutics that target cancer metabolism and serve to overcome the breast cancer burden.

Good Guy or Bad Guy? The Duality of Wild-Type p53 in Hormone-Dependent Breast Cancer Origin, Treatment, and Recurrence

"Lactation is at one point perilously near becoming a cancerous process if it is at all arrested", Beatson, 1896. Most breast cancers arise from the milk-producing cells that are characterized by aberrant cellular, molecular, and epigenetic translation. By understanding the underlying molecular disruptions leading to the origin of cancer, we might be able to design novel strategies for more efficacious treatments or, ambitiously, divert the cancerous process. It is an established reality that full-term pregnancy in a young woman provides a lifetime reduction in breast cancer risk, whereas delay in full-term pregnancy increases short-term breast cancer risk and the probability of latent breast cancer development. Hormonal activation of the p53 protein (encode by the TP53 gene) in the mammary gland at a critical time in pregnancy has been identified as one of the most important determinants of whether the mammary gland develops latent breast cancer. This review discusses what is known about the protective influence of female hormones in young parous women, with a specific focus on the opportune role of wild-type p53 reprogramming in mammary cell differentiation. The importance of p53 as a protector or perpetrator in hormone-dependent breast cancer, resistance to treatment, and recurrence is also explored.

OCT4B regulates p53 and p16 pathway genes to prevent apoptosis of breast cancer cells

Octamer-binding transcription factor 4 (OCT4) is a transcription factor with a well-defined role in stem cell pluripotency. Two OCT4 isoforms, OCT4A and OCT4B, tend to be downregulated as normal cells differentiate. However, OCT4, particularly OCT4B, may become reactivated in cancer cells. Despite this observation, the exact function of OCT4B re-expression in cancer is unclear. In the present study, the role of OCT4 in breast cancer cells was determined. In particular, the ability of OCT4 to regulate key genes involved in cellular proliferation and apoptosis, two pathways that are frequently deregulated in cancer, was examined. The cyclin-dependent kinase inhibitor 2A locus encodes p16INK4a and p14ARF, two important cell cycle inhibitors. The tumor suppressor p53 also has well characterized roles in suppressing proliferation and promoting apoptosis. The present study demonstrated, via overexpression and genetic knockdown techniques, that OCT4B regulates the expression of several of these genes and ultimately regulates the rate of apoptosis of MCF-7 breast cancer cells. It was also observed that, while OCT4B and OCT4A regulate one another, it is OCT4B that serves a more prominent role in regulating the transcription of downstream genes. Taken together, the present results suggest that OCT4B is re-expressed in a number of breast cancer cell lines, where it affects both the transcription of cell cycle genes and the rate of apoptosis. These properties of OCT4B may depend on, at least in part, the co-function of OCT4A.

Apigenin, a dietary flavonoid, induces apoptosis, DNA damage, and oxidative stress in human breast cancer MCF-7 and MDA MB-231 cells

Apigenin is found in several dietary plant foods such as vegetables and fruits. To investigate potential anticancer properties of apigenin on human breast cancer, ER-positive MCF-7 and triple-negative MDA MB-231 cells were used. Moreover, toxicological safety of apigenin towards normal cells was evaluated in human lymphocytes. Cytotoxicity of apigenin towards cancer cells was evaluated by MTT assay whereas further genotoxic and oxidative stress parameters were measured by comet and lipid peroxidation assays, respectively. In order to examine the type of cell death induced by apigenin, several biomarkers were used. Toxicological safety towards normal cells was evaluated by cell viability and comet assays. After the treatment with apigenin, we observed changes in cell morphology in a dose- (10 to 100 μM) and time-dependent manner. Moreover, apigenin caused cell death in both cell lines leading to significant toxicity and dominantly to apoptosis. Furthermore, apigenin proved to be genotoxic towards the selected cancer cells with a potential to induce oxidative damage to lipids. Of great importance is that no significant cytogenotoxic effects were detected in normal cells. The observed cytogenotoxic and pro-cell death activities of apigenin coupled with its low toxicity towards normal cells indicate that this natural product could be used as a future anticancer modality. Therefore, further analysis to determine the exact mechanism of action and in vivo studies on animal models are warranted.

From word models to executable models of signaling networks using automated assembly

Word models (natural language descriptions of molecular mechanisms) are a common currency in spoken and written communication in biomedicine but are of limited use in predicting the behavior of complex biological networks. We present an approach to building computational models directly from natural language using automated assembly. Molecular mechanisms described in simple English are read by natural language processing algorithms, converted into an intermediate representation, and assembled into executable or network models. We have implemented this approach in the Integrated Network and Dynamical Reasoning Assembler (INDRA), which draws on existing natural language processing systems as well as pathway information in Pathway Commons and other online resources. We demonstrate the use of INDRA and natural language to model three biological processes of increasing scope: (i) p53 dynamics in response to DNA damage, (ii) adaptive drug resistance in BRAF‐V600E‐mutant melanomas, and (iii) the RAS signaling pathway. The use of natural language makes the task of developing a model more efficient and it increases model transparency, thereby promoting collaboration with the broader biology community.

Chemopreventive Agents and Inhibitors of Cancer Hallmarks: May Citrus Offer New Perspectives?

Fruits and vegetables have long been recognized as potentially important in the prevention of cancer risk. Thus, scientific interest in nutrition and cancer has grown over time, as shown by increasing number of experimental studies about the relationship between diet and cancer development. This review attempts to provide an insight into the anti-cancer effects of Citrus fruits, with a focus on their bioactive compounds, elucidating the main cellular and molecular mechanisms through which they may protect against cancer. Scientific literature was selected for this review with the aim of collecting the relevant experimental evidence for the anti-cancer effects of Citrus fruits and their flavonoids. The findings discussed in this review strongly support their potential as anti-cancer agents, and may represent a scientific basis to develop nutraceuticals, food supplements, or complementary and alternative drugs in a context of a multi-target pharmacological strategy in the oncology.

Novel Molecular Markers for Breast Cancer

The use of molecular biomarkers assures that breast cancer (BC) patients receive optimal treatment. Established biomarkers, such as estrogen receptor, progesterone receptor, HER2, and Ki67, have been playing significant roles in the subcategorization of BC to predict the prognosis and decide the specific therapy to each patient. Antihormonal therapy using 4-hydroxytamoxifen or aromatase inhibitors have been employed in patients whose tumor cells express hormone receptors, while monoclonal antibody to HER2 has been administered to HER2-positive BCs. Although new therapeutic agents have been developed in the past few decades, many patients still die of the disease due to relapse; thus, novel molecular markers that predict therapeutic failure and those that can be targets for specific therapy are expected. We have chosen four of such molecules by reviewing recent publications, which are cyclin E, B-Myb, Twist, and DMP1β. The oncogenicity of these molecules has been demonstrated in vivo and/or in vitro through studies using transgenic mice or siRNAs, and their expressions have been shown to be associated with shortened overall or disease-free survival of BC patients. The former three molecules have been shown to accelerate epithelial-mesenchymal transition that is often associated with cancer stem cell-ness and metastasis; all these four can be novel therapeutic targets as well. Thus, large prospective studies employing immunohistochemistry will be needed to establish the predictive values of these molecules in patients with BC.

p21 induction plays a dual role in anti-cancer activity of ursolic acid

Previous studies have shown that induction of G1 arrest and apoptosis by ursolic acid is associated with up-regulation of cyclin-dependent kinase inhibitor (CDKI) protein p21 in multiple types of cancer cells. However, the functional role of p21 induction in G1 cell cycle arrest and apoptosis, and the mechanisms of p21 induction by ursolic acid have not been critically addressed. In the current study, we demonstrated that p21 played a mediator role in G1 cell cycle arrest by ursolic acid, whereas p21-mediated up-regulation of Mcl-1 compromised apoptotic effect of ursolic acid. These results suggest that p21 induction plays a dual role in the anti-cancer activity of ursolic acid in terms of cell cycle and apoptosis regulation. p21 induction by ursolic acid was attributed to p53 transcriptional activation. Moreover, we found that ursolic acid was able to inhibit murine double minute-2 protein (MDM2) and T-LAK cell-originated protein kinase (TOPK), the two negative regulator of p53, which in turn contributed to ursolic acid-induced p53 activation. Our findings provided novel insights into understanding of the mechanisms involved in cell cycle arrest and apoptosis induction in response to ursolic acid exposure.

All-trans retinoic acid and genistein induce cell apoptosis in OVCAR-3 cells by increasing the P14 tumor suppressor gene

In this study, we evaluated the effects of all-trans retinoic acid (ATRA) alone or in combination with genistein (GEN) in p14 tumor suppressor gene and subsequent apoptosis of human ovarian carcinoma cells (OVCAR-3). The cells were treated with ATRA or GEN at concentrations of 50 and 25 μM respectively, either alone or in combination for 24 and 48 h. The cell viability was evaluated using 3-(4, 5-dimethylthiazolyl-2)-2, 5-diphenyltetrazolium bromide (MTT) assay. The percentage of cell apoptosis was determined using flow cytometry and p14 gene expression was measured using real time PCR. The MTT results showed that in both ATRA and GEN treated groups, the cell viabilityviability in group treated for 48 h was significantly lower than group treated for 24 h. The flow cytometry results showed that the percentage of apoptotic cells in groups that treated with ATRA and GEN in combination for 24 h and 48 h was significantly more than all other tested groups. The real time results showed that the mRNA level of p14 in cells treated with both drugs for 48 h was significantly higher than all other groups. In conclusion, we confirm that GEN in combination with ATRA is an effective strategy to up regulate the p14 tumor suppressor gene and induce cell apoptosis in OVCAR-3 cell line.

p53 Modulates Notch Signaling in MCF-7 Breast Cancer Cells by Associating With the Notch Transcriptional Complex Via MAML1

p53 and Notch-1 play important roles in breast cancer biology. Notch-1 inhibits p53 activity in cervical and breast cancer cells. Conversely, p53 inhibits Notch activity in T-cells but stimulates it in human keratinocytes. Notch co-activator MAML1 binds p53 and functions as a p53 co-activator. We studied the regulation of Notch signaling by p53 in MCF-7 cells and normal human mammary epithelial cells (HMEC). Results show that overexpression of p53 or activation of endogenous p53 with Nutlin-3 inhibits Notch-dependent transcriptional activity and Notch target expression in a dose-dependent manner. This effect could be partially rescued by transfection of MAML1 but not p300. Standard and quantitative co-immunoprecipitation experiments readily detected a complex containing p53 and Notch-1 in MCF-7 cells. Formation of this complex was inhibited by dominant negative MAML1 (DN-MAML1) and stimulated by wild-type MAML1. Standard and quantitative far-Western experiments showed a complex including p53, Notch-1, and MAML1. Chromatin immunoprecipitation (ChIP) experiments showed that p53 can associate with Notch-dependent HEY1 promoter and this association is inhibited by DN-MAML1 and stimulated by wild-type MAML1. Our data support a model in which p53 associates with the Notch transcriptional complex (NTC) in a MAML1-dependent fashion, most likely through a p53-MAML1 interaction. In our cellular models, the effect of this association is to inhibit Notch-dependent transcription. Our data suggest that p53-null breast cancers may lack this Notch-modulatory mechanism, and that therapeutic strategies that activate wild-type p53 can indirectly cause inhibition of Notch transcriptional activity.

The bone marrow metastasis niche in retinoblastoma

BACKGROUND

Retinoblastoma (Rb) is a progressive cancer which mainly occurs in children, and which is caused by different genetic or epigenetic alterations that lead to inactivation of both alleles of the RB1 gene. Hereditary and non-hereditary forms of Rb do exist, and the hereditary form is associated with an increased risk of secondary malignancies. Metastasis to distant organs is a critical feature of many tumors, and may be caused by various molecular alterations at different stages. Recognition of these alterations and, thus, insight into the processes underlying the development of metastases may result in novel preventive as well as effective targeted treatment options. Rb is associated with metastases to various organs and tissues, including the bone marrow (BM).

METHODS

Here, we provide an overview of mutations and other molecular changes known to be involved in Rb development and metastasis to the BM. This overview is based on a literature search ranging from 1990 to 2015.

CONCLUSIONS

The various BM metastasis-related molecular changes identified to date may be instrumental for a better diagnosis, prognosis and classification of Rb patients, as well as for the development of novel comprehensive (targeted) therapies.

Molecular Targets in Biliary Carcinogenesis and Implications for Therapy

Biliary tract cancers (BTCs) encompass a group of invasive carcinomas, including cholangiocarcinoma (intrahepatic, perihilar, or extrahepatic), and gallbladder carcinoma. Approximately 90% of patients present with advanced, unresectable disease and have a poor prognosis. The latest recommendation is to treat advanced or metastatic disease with gemcitabine and cisplatin, although chemotherapy has recorded modest survival benefits. Comprehension of the molecular basis of biliary carcinogenesis has resulted in experimental trials of targeted therapies in BTCs, with promising results. This review addresses the emerging role of targeted therapy in the treatment of BTCs. Findings from preclinical studies were reviewed and correlated with the outcomes of clinical trials that were undertaken to translate the laboratory discoveries.

IMPLICATIONS FOR PRACTICE

Biliary tract cancers are rare. Approximately 90% of patients present with advanced, unresectable disease and have a poor prognosis. Median overall and progression-free survival are 12 and 8 months, respectively. Because chemotherapy has recorded modest survival benefits, targeted therapies are being explored for personalized treatment of these cancers. A comprehensive review of targeted therapies in biliary tract cancers was undertaken to present emerging evidence from laboratory and/or molecular studies as they translate to clinical trials and outcomes. The latest evidence on this topic is presented to clinicians and practitioners to guide decisions on treatment of this disease.

The type 7 serotonin receptor, 5-HT 7 , is essential in the mammary gland for regulation of mammary epithelial structure and function

Autocrine-paracrine activity of serotonin (5-hydroxytryptamine, 5-HT) is a crucial homeostatic parameter in mammary gland development during lactation and involution. Published studies suggested that the 5-HT₇ receptor type was important for mediating several effects of 5-HT in the mammary epithelium. Here, using 5-HT₇ receptor-null (HT7KO) mice we attempt to understand the role of this receptor in mediating 5-HT actions within the mammary gland. We demonstrate for the first time that HT7KO dams are inefficient at sustaining their pups. Histologically, the HT7KO mammary epithelium shows a significant deviation from the normal secretory epithelium in morphological architecture, reduced secretory vesicles, and numerous multinucleated epithelial cells with atypically displaced nuclei, during lactation. Mammary epithelial cells in HT7KO dams also display an inability to transition from lactation to involution as normally seen by transition from a columnar to a squamous cell configuration, along with alveolar cell apoptosis and cell shedding. Our results show that 5-HT₇ is required for multiple actions of 5-HT in the mammary glands including core functions that contribute to changes in cell shape and cell turnover, as well as specialized secretory functions. Understanding these actions may provide new interventions to improve lactation performance and treat diseases such as mastitis and breast cancer.

Expression of the proto-oncogene Pokemon in colorectal cancer--inhibitory effects of an siRNA

OBJECTIVE

This study aimed to investigate expression of the proto-oncogene POK erythroid myeloid ontogenic factor (Pokemon) in colorectal cancer (CRC), and assess inhibitory effects of a small interference RNA (siRNA) expression vector in SW480 and SW620 cells.

METHODS

Semi-quantitative reverse transcription-polymerase chain reaction (PCR) and immunohistochemistry were performed to determine mRNA and protein expression levels of Pokemon in CRC tissues. Indirect immunofluorescence staining was applied to investigate the location of Pokemon in SW480 and SW620 cells. The siRNA expression vectors that were constructed to express a short hairpin RNA against Pokemon were transfected to the SW480 and SW620 cells with a liposome. Expression levels of Pokemon mRNA and protein were examined by real-time quantitative-fluorescent PCR and western blot analysis. The effects of Pokemon silencing on proliferation of SW480 and SW620 cells were evaluated with reference to growth curves with MTT assays.

RESULTS

The mRNA expression level of Pokemon in tumor tissues (0.845 ± 0.344) was significantly higher than that in adjacent tumor specimens (0.321 ± 0.197). The positive expression ratio of Pokemon protein in CRC (87.0%) was significantly higher than that in the adjacent tissues (19.6%). Strong fluorescence staining of Pokemon protein was observed in the cytoplasm of the SW480 and SW620 cells. The inhibition ratios of Pokemon mRNA and protein in the SW480 cells were 83.1% and 73.5% at 48 and 72 h, respectively, compared with those of the negative control cells with the siRNA. In the SW620 cells, the inhibition ratios of Pokemon mRNA and protein were 76.3% and 68.7% at 48 and 72 h, respectively. MTT showed that Pokemon gene silencing inhibited the proliferation of SW480 and SW620 cells.

CONCLUSION

Overexpression of Pokemon in CRC may have a function in carcinogenesis and progression. siRNA expression vectors could effectively inhibit mRNA and protein expression of Pokemon in SW480 and SW620 cells, thereby reducing malignant cell proliferation.

Oncomir miR-125b suppresses p14(ARF) to modulate p53-dependent and p53-independent apoptosis in prostate cancer

MicroRNAs are a class of naturally occurring small non-coding RNAs that target protein-coding mRNAs at the post-transcriptional level and regulate complex patterns of gene expression. Our previous studies demonstrated that in human prostate cancer the miRNA miR-125b is highly expressed, leading to a negative regulation of some tumor suppressor genes. In this study, we further extend our studies by showing that miR-125b represses the protein product of the ink4a/ARF locus, p14(ARF), in two prostate cancer cell lines, LNCaP (wild type-p53) and 22Rv1 (both wild type and mutant p53), as well as in the PC-346C prostate cancer xenograft model that lentivirally overexpressed miR-125b. Our results highlight that miR-125b modulates the p53 network by hindering the down-regulation of Mdm2, thereby affecting p53 and its target genes p21 and Puma to a degree sufficient to inhibit apoptosis. Conversely, treatment of prostate cancer cells with an inhibitor of miR-125b (anti-miR-125b) resulted in increased expression of p14(ARF), decreased level of Mdm2, and induction of apoptosis. In addition, overexpression of miR-125b in p53-deficient PC3 cells induced down-regulation of p14(ARF), which leads to increased cell proliferation through a p53-independent manner. Thus, we conclude that miR-125b acts as an oncogene which regulates p14(ARF)/Mdm2 signaling, stimulating proliferation of prostate cancer cells through a p53-dependent or p53-independent function. This reinforces our belief that miR-125b has potential as a therapeutic target for the management of patients with metastatic prostate cancer.

Phenotypic and Molecular Characterization of MCF10DCIS and SUM Breast Cancer Cell Lines

We reviewed the phenotypic and molecular characteristics of MCF10DCIS.com and the SUM cell lines based on numerous studies performed over the years. The major signaling pathways that give rise to the phenotype of these cells may serve as a good resource of information when researchers in drug discovery and development use these cells to identify novel targets and biomarkers. Major signaling pathways and mutations affecting the coding sequence are also described providing important information when using these cells as a model in a variety of studies.

The silencing of Pokemon attenuates the proliferation of hepatocellular carcinoma cells in vitro and in vivo by inhibiting the PI3K/Akt pathway

Pokemon (POK erythroid myeloid ontogenic factor), which belongs to the POK protein family, is also called LRF, OCZF and FBI-1. As a transcriptional repressor, Pokemon assumes a critical function in cellular differentiation and oncogenesis. Our study identified an oncogenic role for Pokemon in human hepatocellular carcinoma (HCC). We successfully established human HepG2 and Huh-7 cell lines in which Pokemon was stably knocked down. We demonstrated that Pokemon silencing inhibited cell proliferation and migration. Pokemon knockdown inhibited the PI3K/Akt and c-Raf/MEK/ERK pathways and modulated the expression of various cell cycle regulators in HepG2 and Huh-7 cells. Therefore, Pokemon may also be involved in cell cycle progression in these cells. We confirmed that Pokemon silencing suppresses hepatocellular carcinoma growth in tumor xenograft mice. These results suggest that Pokemon promotes cell proliferation and migration in hepatocellular carcinoma and accelerates tumor development in an Akt- and ERK-signaling-dependent manner.

A biomimetic nanovector-mediated targeted cholesterol-conjugated siRNA delivery for tumor gene therapy

RNA interference holds tremendous potential as a therapeutic approach of malignant tumors. However, safe and efficient nanovectors are extremely lack for systemic delivery of small interfering RNA (siRNA). The study aimed to develop a biomimetic nanovector, reconstituted high density lipoprotein (rHDL), mediating targeted cholesterol-conjugated siRNA (Chol-siRNA) delivery for Pokemon gene silencing therapy. Chol-siRNA-loaded rHDL nanoparticles (rHDL/Chol-siRNA complexes) were prepared using thin-film dispersion method and their characteristics were investigated in detail. RHDL/Chol-siRNA complexes at the optimal volume ratio (lipid: Chol-siRNA) exhibited high Chol-siRNA-loading efficiency (~99%), desirable nanoparticle size and excellent stability in serum. In addition, by analyzing Chol-siRNA release profile, rHDL/Chol-siRNA complexes displayed sustained-release characteristic and storage stability. Observations from FACS and confocal microscopic analyses revealed that rHDL-mediated carboxyfluorescein tagged Chol-siRNA (FAM-Chol-siRNA) transfection resulted in highly efficient uptake and specific cytoplasmic delivery of FAM-Chol-siRNA into human hepatocellular carcinoma cell line HepG2 via HDL-receptor mediated mechanism. In vitro cytotoxicity, apoptosis and Western-blot analyses revealed significant cellular growth inhibition and decrease of Pokemon and Bcl-2 protein expression in HepG2 cells treated with Chol-siRNA-Pokemon-loaded rHDL nanoparticles (rHDL/Chol-siRNA-Pokemon complexes), respectively. In in vivo studies, the near-infrared (NIR) dye Cy5 labeled Chol-siRNA-loaded rHDL nanoparticles (rHDL/Cy5-Chol-siRNA complexes) obviously accumulated in tumor of nude mice after i.v. administration as compared with Cy5-Chol-siRNA-loaded lipoplexes (Lipos/Cy5-Chol-siRNA complexes). Morover, rHDL/Chol-siRNA-Pokemon complexes demonstrated great tumor growth inhibition and significant decrease of Pokemon and Bcl-2 protein expression in vivo. These results suggested that rHDL should be an ideal non-viral tumor-targeting vector for Chol-siRNA transfer, and rHDL-mediated Chol-siRNA-Pokemon delivery might be a promising new strategy for gene therapy in hepatocellular carcinoma.

p53, a target of estrogen receptor (ER) α, modulates DNA damage-induced growth suppression in ER-positive breast cancer cells

In response to genotoxic stress, the p53 tumor suppressor induces target genes for cell cycle arrest, apoptosis, and DNA repair. Although p53 is the most commonly mutated gene in all human cancers, it is only mutated in about 20% of breast cancers. 70% of all breast cancer cases are estrogen receptor (ER)-positive and express ERα. ER-positive breast cancer generally indicates good patient prognosis and treatment responsiveness with antiestrogens, such as tamoxifen. However, ER-positive breast cancer patients can experience loss or a reduction in ERα, which is associated with aggressive tumor growth, increased invasiveness, poor prognosis, and loss of p53 function. Consistent with this, we found that p53 is a target gene of ERα. Specifically, we found that knockdown of ERα decreases expression of p53 and its downstream targets, MDM2 and p21. In addition, we found that ERα activates p53 transcription via binding to estrogen response element half-sites within the p53 promoter. Moreover, we found that loss of ERα desensitizes, whereas ectopic expression of ERα sensitizes, breast cancer cells to DNA damage-induced growth suppression in a p53-dependent manner. Altogether, this study provides an insight into a feedback loop between ERα and p53 and a biological role of p53 in the DNA damage response in ER-positive breast cancers.

Pokemon reduces Bcl-2 expression through NF-κ Bp65: A possible mechanism of hepatocellular carcinoma

OBJECTIVE

To investigate the relationship among Pokemon, NF-κ B p65 and Bcl-2 in hepatoma cells.

METHODS

HCC cell HepG2, SMMC7721 and human fetal liver cell line LO2 cells were used, and expression of Pokemon, NF-κ B p65 and Bcl-2 in three cells were detected by real-time PCR and western blot. Then siRNA of Pokemon was applied to inhibit the expression of Pokemon and NF-κ B p65 and apoptotic rate was determined by flow cytometric analysis.

RESULTS

Expressions of Pokemon, NF-κ B p65 and Bcl-2 in human hepatoma cell HepG2, SMMC7721 expression were significantly higher than those in human embryonic stem cells LO2. siRNA of Pokemon inhibited the expression of Pokemon, NF-κ B p65 and Bcl-2 in liver cancer cells, and significantly increased apoptosis of liver cells. While siRNA of NF-κ B p65 inhibited the expression of NF-κ B p65 and Bcl-2, but Pokemon expression in hepatoma cells had no significant change.

CONCLUSIONS

The proto-oncogene Pokemon can inhibit P14ARF by specific transcription regulation of cell cycle and can induce tumors. In addition, Pokemon can regulate NF-κ B p65 through the expression of apoptosis repressor, and promote the development of liver cancer. It suggests signal network in the liver include the regulation of new non-classical NF-κ B regulatory pathway.

Endoplasmic reticulum chaperone glucose regulated protein 170-Pokemon complexes elicit a robust antitumor immune response in vivo

Previous evidence suggested that the stress protein grp170 can function as a highly efficient molecular chaperone, binding to large protein substrates and acting as a potent vaccine against specific tumors when purified from the same tumor. In addition, Pokemon can be found in almost all malignant tumor cells and is regarded to be a promising candidate for the treatment of tumors. However, the potential of the grp170-Pokemon chaperone complex has not been well described. In the present study, the natural chaperone complex between grp170 and the Pokemon was formed by heat shock, and its immunogenicity was detected by ELISPOT and (51)Cr-release assays in vitro and by tumor bearing models in vivo. Our results demonstrated that the grp170-Pokemon chaperone complex could elicit T cell responses as determined by ELISPOT and (51)Cr-release assays. In addition, immunized C57BL/6 mice were challenged with subcutaneous (s.c.) injection of Lewis cancer cells to induce primary tumors. Treatment of mice with the grp170-Pokemon chaperone complex also significantly inhibited tumor growth and prolonged the life span of tumor-bearing mice. Our results indicated that the grp170-Pokemon chaperone complex might represent a powerful approach to tumor immunotherapy and have significant potential for clinical application.

Expression of SPRR3 is associated with tumor cell proliferation in less advanced stages of breast cancer

Small proline rich repeat protein 3 (SPRR3), a member of the SPRR family of cornified envelope precursor proteins, is a marker for terminal squamous cell differentiation. Previously, this laboratory showed that SPRR3 is strongly upregulated in colorectal tumors, and is involved in the tumorigenesis. The current study was performed to investigate the expression status and effect of SPRR3 in breast cancers (BCs). SPRR3 expression was examined by immunohistochemistry in 241 tumor samples from BC patients. SPRR3 was overexpressed in more than half of all BC samples. SPRR3 overexpression was significantly associated with less advanced stage (0-1 vs. II-III) and the absence of lymph node metastasis (P = 0.004 and 0.013, respectively). HER2/neu overexpression was closely correlated with SPRR3 overexpression in a multivariate analysis (OR, 3.23, P = 0.017). To assess the influence of SPRR3 on cell proliferation and related signaling pathways, SPRR3-transfected clones from the SPRR3-negative T-47D human BC cell line were generated. Among the total of six SPRR3-overexpressing clones, five showed marked proliferation compared with SPRR3-nonexpressing control cells from day 3 of culture (P < 0.001). The SPRR3-overexpressing BC clones showed increased phosphorylation of AKT and MDM2, p21 overexpression, and p53 downregulation. Furthermore, phosphorylation of MEK and MAPK was markedly increased. This study demonstrates that SPRR3 promotes BC cell proliferation by enhancing p53 degradation via the AKT and MAPK pathways and is, therefore, a potential novel therapeutic target for less advanced stages of BC.