Senescence delay and repression of p16INK4a by Lsh via recruitment of histone deacetylases in human diploid fibroblasts

Oncogenic Ras and ΔNp63α cooperate to recruit immunosuppressive polymorphonuclear myeloid-derived suppressor cells in a mouse model of squamous cancer pathogenesis

Introduction

Amplification of human chromosome 3q26-29, which encodes oncoprotein ΔNp63 among other isoforms of the p63 family, is a feature common to squamous cell carcinomas (SCCs) of multiple tissue origins. Along with overexpression of ΔNp63, activation of the protooncogene, RAS, whether by overexpression or oncogenic mutation, is frequently observed in many cancers. In this study, analysis of transcriptome data from The Cancer Genome Atlas (TCGA) demonstrated that expression of TP63 mRNA, particularly ΔNp63 isoforms, and HRAS are significantly elevated in advanced squamous cell carcinomas of the head and neck (HNSCCs), suggesting pathological significance. However, how co-overexpressed ΔNp63 and HRAS affect the immunosuppressive tumor microenvironment (TME) is incompletely understood.

Methods

Here, we established and characterized an immune competent mouse model using primary keratinocytes with retroviral-mediated overexpression of ΔNp63α and constitutively activated HRAS (v-rasHa G12R) to evaluate the role of these oncogenes in the immune TME.

Results

In this model, orthotopic grafting of wildtype syngeneic keratinocytes expressing both v-rasHa and elevated levels of ΔNp63α consistently yield carcinomas in syngeneic hosts, while cells expressing v-rasHa alone yield predominantly papillomas. We found that polymorphonuclear (PMN) myeloid cells, experimentally validated to be immunosuppressive and thus representing myeloid-derived suppressor cells (PMN-MDSCs), were significantly recruited into the TME of carcinomas arising early following orthotopic grafting of ΔNp63α/v-rasHa-expressing keratinocytes. ΔNp63α/v-rasHa-driven carcinomas expressed higher levels of chemokines implicated in recruitment of MDSCs compared to v-rasHa-initiated tumors, providing a heretofore undescribed link between ΔNp63α/HRAS-driven carcinomas and the development of an immunosuppressive TME.

Conclusion

These results support the utilization of a genetic carcinogenesis model harboring specific genomic drivers of malignancy to study mechanisms underlying the development of local immunosuppression.

Alteration in mitochondrial dynamics promotes the proinflammatory response of microglia and is involved in cerebellar dysfunction of young and aged mice following LPS exposure

Cerebellar dysfunction is implicated in impaired motor coordination and balance, thus disturbing the dynamics of sensorimotor integration. Neuroinflammation and aging could be prominent contributors to cerebellar aberration. Additionally, changes in mitochondrial dynamics may precede microglia activation in several chronic neurodegenerative diseases; however, the underlying mechanism remains largely unknown.Here using LPS (1 mg/kg i.p. for four consecutive days) stimulation in both young (3 months old) and aged (12 months old) mice, followed by molecular analysis on the 21st day, we have explored the correlation between aging and mitochondrial dynamic alteration in the backdrop of chronic neuroinflammation. Following LPS stimulation, we observed microglia activation and subsequent elevation in proinflammatory cytokines (M1; TNF-α, IFN-γ) with NLRP3 activationand a concomitant reduction in the expression of anti-inflammatory markers (M2; YM1, TGF-β1) in the cerebellar tissue of aged mice compared with the young LPS and aged controls. Remarkably, senescence (p21, p27, p53) and epigenetic (HDAC2) markers were found upregulated in the cerebellum tissue of the aged LPS group, suggesting their crucial role in LPS-induced cerebellar deficit. Further, we demonstrated alteration in the antagonistic forces of mitochondrial fusion and fission with increased expression of the mitochondrial fission-related gene [FIS1] and decreased fusion-related genes [MFN1 and MFN2]. We noted increased mtDNA copy number, microglia activation, and inflammatory response of IL1β and IFN-γ post-chronic neuroinflammation in aged LPS group. Our results suggest that the crosstalk between mitochondrial dynamics and altered microglial activation paradigm in chronic neuroinflammatory conditions may be the key to understanding the cerebellar molecular mechanism.

The role of oxidative stress in intervertebral disc cellular senescence

With the aggravation of social aging and the increase in work intensity, the prevalence of spinal degenerative diseases caused by intervertebral disc degeneration(IDD)has increased yearly, which has driven a heavy economic burden on patients and society. It is well known that IDD is associated with cell damage and degradation of the extracellular matrix. In recent years, it has been found that IDD is induced by various mechanisms (e.g., genetic, mechanical, and exposure). Increasing evidence shows that oxidative stress is a vital activation mechanism of IDD. Reactive oxygen species (ROS) and reactive nitrogen species (RNS) could regulate matrix metabolism, proinflammatory phenotype, apoptosis, autophagy, and aging of intervertebral disc cells. However, up to now, our understanding of a series of pathophysiological mechanisms of oxidative stress involved in the occurrence, development, and treatment of IDD is still limited. In this review, we discussed the oxidative stress through its mechanisms in accelerating IDD and some antioxidant treatment measures for IDD.

Regulation of Ferroptosis Pathway by Ubiquitination

Ferroptosis is an iron-dependent form of programmed cell death, which plays crucial roles in tumorigenesis, ischemia–reperfusion injury and various human degenerative diseases. Ferroptosis is characterized by aberrant iron and lipid metabolisms. Mechanistically, excess of catalytic iron is capable of triggering lipid peroxidation followed by Fenton reaction to induce ferroptosis. The induction of ferroptosis can be inhibited by sufficient glutathione (GSH) synthesis via system Xc^– transporter-mediated cystine uptake. Therefore, induction of ferroptosis by inhibition of cystine uptake or dampening of GSH synthesis has been considered as a novel strategy for cancer therapy, while reversal of ferroptotic effect is able to delay progression of diverse disorders, such as cardiopathy, steatohepatitis, and acute kidney injury. The ubiquitin (Ub)–proteasome pathway (UPP) dominates the majority of intracellular protein degradation by coupling Ub molecules to the lysine residues of protein substrate, which is subsequently recognized by the 26S proteasome for degradation. Ubiquitination is crucially involved in a variety of physiological and pathological processes. Modulation of ubiquitination system has been exhibited to be a potential strategy for cancer treatment. Currently, more and more emerged evidence has demonstrated that ubiquitous modification is involved in ferroptosis and dominates the vulnerability to ferroptosis in multiple types of cancer. In this review, we will summarize the current findings of ferroptosis surrounding the viewpoint of ubiquitination regulation. Furthermore, we also highlight the potential effect of ubiquitination modulation on the perspective of ferroptosis-targeted cancer therapy.

HDAC2 and 7 down-regulation induces senescence in dermal fibroblasts

Originally simply reported to be in a stable and irreversible growth arrest in vitro, senescent cells are now clearly associated with normal and pathological ageing in vivo. They are characterized by several biomarkers and changes in gene expression that may depend on epigenetic factors, such as histone acetylation, involving a balance between histone acetyltransferases (HATs) and histone deacetylases (HDACs). In this study, we investigate the expression and the role of HDACs on the senescent phenotype of dermal fibroblasts. We report that during replicative senescence, most canonical HDACs are less expressed. Moreover, treatment with SAHA, a histone deacetylase inhibitor (HDACi) also known as Vorinostat, or the specific downregulation of HDAC2 or HDAC7 by siRNA, induces the appearance of senescence biomarkers of dermal fibroblasts. Conversely, the ectopic re-expression of HDAC7 by lentiviral transduction in pre-senescent dermal fibroblasts extends their proliferative lifespan. These results demonstrate that HDACs expression can modulate the senescent phenotype, highlighting their pharmaceutical interest in the context of healthy ageing.

HELLS, a chromatin remodeler is highly expressed in pancreatic cancer and downregulation of it impairs tumor growth and sensitizes to cisplatin by reexpressing the tumor suppressor TGFBR3

Pancreatic cancer (PC) is the most malignant cancer type in the digestive system with a poor prognosis. Chemotherapy such as cisplatin is the last chance for PC patients diagnosed with advanced or metastatic disease. Obtaining a deep understanding of the molecular mechanism underlying PC tumorigenesis and identifying optimal biomarkers to estimate chemotherapy sensitivity are essential for PC treatment. The chromatin remodeler HELLS was found to regulate various tumor suppressors through an epigenetic pathway in several cancers. We analyzed HELLS expression in clinical samples by Western blotting and immunohistochemical staining. Next, we identified the variation in tumor growth and cisplatin sensitivity after knockdown of HELLS and explored the downstream mediators of HELLS in PC via RNA-seq, chromatin immunoprecipitation, and gain- and loss-of-function assays. We found that HELLS is upregulated in PC tissues and correlates with advanced clinical stage and a poor prognosis, and the knockdown of HELLS leads to tumor growth arrest and increased sensitivity to cisplatin. Mechanistically, the tumor suppressor TGFBR3 is markedly reexpressed after HELLS knockdown; conversely, compromising TGFBR3 rescues HELLS knockdown-mediated effects in PC cells. Thus, our data provide evidence that HELLS can serve as a potential oncogene and suitable biomarker to evaluate chemotherapy sensitivity via epigenetically silencing the tumor suppressor TGFBR3 in PC.

Mitochondrial nucleoid remodeling and biogenesis are regulated by the p53-p21WAF1-PKCζ pathway in p16INK4a-silenced cells

Mitochondrial dysfunction is linked to age-related senescence phenotypes. We report here the pathway increasing nucleoid remodeling and biogenesis in mitochondria during the senescence of foreskin human diploid fibroblasts (fs-HDF) and WI-38 cells. Replicative senescence in fs-HDF cells increased mitochondrial nucleoid remodeling as indicated by 5-bromo-2'-deoxyuridine (BrdU) incorporation and mitochondrial transcription factor A (TFAM) expression in enlarged and fused mitochondria. Mitochondrial nucleoid remodeling was accompanied by mitochondrial biogenesis in old cells, and the expression levels of OXPHOS complex-I, -IV and -V subunits, PGC-1α and NRF1 were greatly increased compared to young cells. Activated protein kinase C zeta (PKCζ) increased mitochondrial activity and expressed phenotypes of delayed senescence in fs-HDF cells, but not in WI-38 cells. The findings were reproduced in the doxorubicin-induced senescence of young fs-HDF and WI-38 cells via the PKCζ-LKB1-AMPK signaling pathway, which was regulated by the p53-p21^WAF1 pathway when p16^INK4a was silenced. The signaling enhanced PGC-1α-NRF1-TFAM axis in mitochondria, which was demonstrated by Ingenuity Pathway Analysis of young and old fs-HDF cells. Activation of the p53-p21^WAF1 pathway and silencing of p16^INK4a are responsible for mitochondrial reprogramming in senescent cells, which may be a compensatory mechanism to promote cell survival under senescence stress.

Downregulation of the Helicase Lymphoid-Specific (HELLS) Gene Impairs Cell Proliferation and Induces Cell Cycle Arrest in Colorectal Cancer Cells

AIM

Colorectal cancer (CRC) is the fourth most frequently diagnosed cancer worldwide. Despite the decrease in mortality of CRC patients, further investigation of the molecular pathogenesis of CRC could unveil new therapeutic targets and offer better prognosis predictions, which might direct attention to epigenetic regulators.

METHODS

Publicly available data from the Gene Expression Omnibus (GEO) database and clinical samples were collected. Bioinformatics methods were used to screen hub genes expressed in CRC. qRT-PCR and Western blotting were used to experimentally determine the expression of one gene of interest, the helicase lymphoid-specific (HELLS) gene, at the RNA and protein levels. Immunohistochemical (IHC) assays were used to correlate the stained HELLS proteins to survival data. Cell proliferation levels were assayed by a CCK-8 kit, a colony formation assay was performed, and flow cytometry was used to quantify the cells at each stage of the cell cycle.

RESULTS

A total of 225 overlapping genes were screened, including 14 hub genes. Analysis through a protein-protein interaction (PPI) network and the Gene Ontology database was performed by using the Cytoscape and DAVID online tools, respectively. HELLS RNA and protein expression levels in tumor tissues were 2.09-fold higher and 1.46-fold higher, respectively, than in the peritumoral tissues (p < 0.001, p<0.001). HELLS expression was significantly associated with the T stage (p=0.0027), M stage (p=0.0119), and TNM clinical stage (p = 0.0312) and a higher pathological grade (p=0.049). Highly expressed HELLS was reversibly associated with overall survival (log-rank p = 0.027). HELLS siRNA impaired cell proliferation and colony generation in vitro. HELLS siRNA induced significant G2+M arrest in HT29 and HCT116 cells compared with the respective negative controls (82.29% vs 25.85% and 35.41% vs 15.26%, respectively).

CONCLUSION

Our data revealed that HELLS was significantly upregulated in CRC and correlated with clinicopathological parameters. High expression of HELLS indicated poor prognosis for CRC patients. HELLS knockdown led to impaired cell proliferation, colony generation, and G2+M cell cycle arrest.

Upregulation of the chromatin remodeler HELLS is mediated by YAP1 in Sonic Hedgehog Medulloblastoma

Medulloblastoma is a malignant pediatric tumor that arises from neural progenitors in the cerebellum. Despite a five-year survival rate of ~70%, nearly all patients incur adverse side effects from current treatment strategies that drastically impact quality of life. Roughly one-third of medulloblastoma are driven by aberrant activation of the Sonic Hedgehog (SHH) signaling pathway. However, the scarcity of genetic mutations in medulloblastoma has led to investigation of other mechanisms contributing to cancer pathogenicity including epigenetic regulation of gene expression. Here, we show that Helicase, Lymphoid Specific (HELLS), a chromatin remodeler with epigenetic functions including DNA methylation and histone modification, is induced by Sonic Hedgehog (SHH) in SHH-dependent cerebellar progenitor cells and the developing murine cerebella. HELLS is also up-regulated in mouse and human SHH medulloblastoma. Others have shown that HELLS activity generally results in a repressive chromatin state. Our results demonstrate that increased expression of HELLS in our experimental systems is regulated by the oncogenic transcriptional regulator YAP1 downstream of Smoothened, the positive transducer of SHH signaling. Elucidation of HELLS as one of the downstream effectors of the SHH pathway may lead to novel targets for precision therapeutics with the promise of better outcomes for SHH medulloblastoma patients.

Endothelial toll-like receptor 4 maintains lung integrity via epigenetic suppression of p16INK4a

We previously reported that the canonical innate immune receptor toll-like receptor 4 (TLR4) is critical in maintaining lung integrity. However, the molecular mechanisms via which TLR4 mediates its effect remained unclear. In the present study, we identified distinct contributions of lung endothelial cells (Ec) and epithelial cells TLR4 to pulmonary homeostasis using genetic-specific, lung- and cell-targeted in vivo methods. Emphysema was significantly prevented via the reconstituting of human TLR4 expression in the lung Ec of TLR4-/- mice. Lung Ec-silencing of TLR4 in wild-type mice induced emphysema, highlighting the specific and distinct role of Ec-expressed TLR4 in maintaining lung integrity. We also identified a previously unrecognized role of TLR4 in preventing expression of p16INK4a , a senescence-associated gene. Lung Ec-p16INK4a -silencing prevented TLR4-/- induced emphysema, revealing a new functional role for p16INK4a in lungs. TLR4 suppressed endogenous p16INK4a expression via HDAC2-mediated deacetylation of histone H4. These findings suggest a novel role for TLR4 in maintaining of lung homeostasis via epigenetic regulation of senescence-related gene expression.

HELLS Regulates Chromatin Remodeling and Epigenetic Silencing of Multiple Tumor Suppressor Genes in Human Hepatocellular Carcinoma

Hepatocellular carcinoma (HCC) is the third most lethal cancer worldwide. Increasing evidence shows that epigenetic alterations play an important role in human carcinogenesis. Deregulation of DNA methylation and histone modifications have recently been characterized in HCC, but the significance of chromatin remodeling in liver carcinogenesis remains to be explored. In this study, by systematically analyzing the expression of chromatin remodeling genes in human HCCs, we found that helicase, lymphoid-specific (HELLS), an SWI2/SNF2 chromatin remodeling enzyme, was remarkably overexpressed in HCC. Overexpression of HELLS correlated with more aggressive clinicopathological features and poorer patient prognosis compared to patients with lower HELLS expression. We further showed that up-regulation of HELLS in HCC was conferred by hyperactivation of transcription factor specificity protein 1 (SP1). To investigate the functions of HELLS in HCC, we generated both gain-of-function and loss-of-function models by the CRISPR activation system, lentiviral short hairpin RNA, and the CRISPR/Cas9 genome editing system. We demonstrated that overexpression of HELLS augmented HCC cell proliferation and migration. In contrast, depletion of HELLS reduced HCC growth and metastasis both in vitro and in vivo. Moreover, inactivation of HELLS led to metabolic reprogramming and reversed the Warburg effect in HCC cells. Mechanistically, by integrating analysis of RNA sequencing and micrococcal nuclease sequencing, we revealed that overexpression of HELLS increased nucleosome occupancy, which obstructed the accessibility of enhancers and hindered formation of the nucleosome-free region (NFR) at the transcription start site. Though this mechanism, up-regulation of HELLS mediated epigenetic silencing of multiple tumor suppressor genes including E-cadherin, FBP1, IGFBP3, XAF1 and CREB3L3 in HCC. Conclusion: Our data reveal that HELLS is a key epigenetic driver of HCC; by altering the nucleosome occupancy at the NFR and enhancer, HELLS epigenetically suppresses multiple tumor suppressor genes to promote HCC progression.

Dormancy and cancer stem cells: An enigma for cancer therapeutic targeting

Dormancy occurs when cells remain viable but stop proliferating. When most of a cancer population undergoes this phenomenon, the result is called tumor dormancy, and when a single cancer cell undergoes this process, it is termed quiescence. Cancer stem cells (CSCs) share several overlapping characteristics and signaling pathways with dormant cancer cells, including therapy resistance, and an ability to metastasize and evade the immune system. Cancer cells can be broadly grouped into dormancy-competent CSCs (DCCs), cancer-repopulating cells (CRCs), dormancy-incompetent CSCs and disseminated tumor cells (DTCs). The settings in which cancer cells exploit the dormancy phase to survive and adapt are: (i) primary cancer dormancy; (ii) metastatic dormancy; (iii) therapy-induced dormancy; and (iv) immunologic dormancy. Dormancy, therapy resistance and plasticity of CSCs are fundamentally interconnected processes mediated through mechanisms involving reversible genetic alterations. Niches including metastatic, bone marrow, and perivascular are known to harbor dormant cancer cells. Mechanisms of dormancy induction are complex and multi-factorial and can involve angiogenic switching, addictive oncogene inhibition, immunoediting, anoikis, therapy, autophagy, senescence, epigenetic, and biophysical regulation. Therapy can have opposing effects on cancer cells with respect to dormancy; some therapies can induce dormancy, while others can reactivate dormant cells. There is a lack of consensus relative to the value of therapy-induced dormancy, i.e., some researchers view dormancy induction as a beneficial strategy as it can lead to metastasis inhibition, while others argue that reactivating dormant cancer cells and then eliminating them through therapy are a better approach. More focused investigations of intrinsic cell kinetics and environmental dynamics that promote and maintain cancer cells in a dormant state, and the long-term consequences of dormancy are critical for improving current therapeutic treatment outcomes.

Epigenetic Regulation of Skin Cells in Natural Aging and Premature Aging Diseases

Skin undergoes continuous renewal throughout an individual’s lifetime relying on stem cell functionality. However, a decline of the skin regenerative potential occurs with age. The accumulation of senescent cells over time probably reduces tissue regeneration and contributes to skin aging. Keratinocytes and dermal fibroblasts undergo senescence in response to several intrinsic or extrinsic stresses, including telomere shortening, overproduction of reactive oxygen species, diet, and sunlight exposure. Epigenetic mechanisms directly regulate skin homeostasis and regeneration, but they also mark cell senescence and the natural and pathological aging processes. Progeroid syndromes represent a group of clinical and genetically heterogeneous pathologies characterized by the accelerated aging of various tissues and organs, including skin. Skin cells from progeroid patients display molecular hallmarks that mimic those associated with naturally occurring aging. Thus, investigations on progeroid syndromes strongly contribute to disclose the causal mechanisms that underlie the aging process. In the present review, we discuss the role of epigenetic pathways in skin cell regulation during physiologic and premature aging.

Cellular senescence induces replication stress with almost no affect on DNA replication timing

Organismal aging entails a gradual decline of normal physiological functions and a major contributor to this decline is withdrawal of the cell cycle, known as senescence. Senescence can result from telomere diminution leading to a finite number of population doublings, known as replicative senescence (RS), or from oncogene overexpression, as a protective mechanism against cancer. Senescence is associated with large-scale chromatin re-organization and changes in gene expression. Replication stress is a complex phenomenon, defined as the slowing or stalling of replication fork progression and/or DNA synthesis, which has serious implications for genome stability, and consequently in human diseases. Aberrant replication fork structures activate the replication stress response leading to the activation of dormant origins, which is thought to be a safeguard mechanism to complete DNA replication on time. However, the relationship between replicative stress and the changes in the spatiotemporal program of DNA replication in senescence progression remains unclear. Here, we studied the DNA replication program during senescence progression in proliferative and pre-senescent cells from donors of various ages by single DNA fiber combing of replicated DNA, origin mapping by sequencing short nascent strands and genome-wide profiling of replication timing (TRT). We demonstrate that, progression into RS leads to reduced replication fork rates and activation of dormant origins, which are the hallmarks of replication stress. However, with the exception of a delay in RT of the CREB5 gene in all pre-senescent cells, RT was globally unaffected by replication stress during entry into either oncogene-induced or RS. Consequently, we conclude that RT alterations associated with physiological and accelerated aging, do not result from senescence progression. Our results clarify the interplay between senescence, aging and replication programs and demonstrate that RT is largely resistant to replication stress.

Genetic ablation of histone deacetylase 2 leads to lung cellular senescence and lymphoid follicle formation in COPD/emphysema

Histone deacetylase 2 (HDAC2), a critical determinant of chromatin remodeling, is reduced as a consequence of oxidative stress-mediated DNA damage and impaired repair. Cigarette smoke (CS) exposure causes DNA damage and cellular senescence. However, no information is available on the role of HDAC2 in CS-induced DNA damage, stress-induced premature senescence (SIPS), and senescence-associated secretory phenotype (SASP) during the pathogenesis of chronic obstructive pulmonary disease (COPD)/emphysema. We hypothesized that CS causes persistent DNA damage and cellular senescence via HDAC2-dependent mechanisms. We used HDAC2 global knockout (KO) and HDAC2 lung epithelial cell-specific KO [Clara cell-specific HDAC2 deletion (HDAC2 CreCC10)] mice to determine whether HDAC2 is a major player in CS-induced oxidative stress, SIPS, and SASP. HDAC2 KO mice exposed to CS show exaggerated DNA damage, inflammatory response, and decline in lung function leading to airspace enlargement. Chronic CS exposure augments lung senescence-associated β-galactosidase activity in HDAC2 KO, but not in HDAC2 CreCC10 mice. HDAC2 lung epithelial cell-specific KO did not further augment CS-induced inflammatory response and airspace enlargement but instead caused an increase in lymphoid aggregate formation. Our study reveals that HDAC2 is a key player regulating CS-induced DNA damage, inflammatory response, and cellular senescence leading to COPD/emphysema.-Sundar, I. K., Rashid, K., Gerloff, J., Rangel-Moreno, J., Li, D., Rahman, I. Genetic ablation of histone deacetylase 2 leads to lung cellular senescence and lymphoid follicle formation in COPD/emphysema.

FOXO1 is crucial in glioblastoma cell tumorigenesis and regulates the expression of SIRT1 to suppress senescence in the brain

In the present study, the role of Forkhead Box O1 (FOXO1) in glioblastoma (GBM) cell tumorigenesis was examined and the underlying mechanisms were investigated. Reverse transcription‑quantitative polymerase chain reaction and western blot analyses were used to analyze the expression of FOXO1 in GBM cell lines (LN18 and T98G) and tissues. Compared with the control groups, FOXO1 was significantly downregulated in the GBM tissues and GBM cell lines (P<0.05). The effects of the expression of FOXO1 on GBM cell proliferation and cell cycle were examined using flow cytometry. The overexpression of FOXO1 markedly inhibited LN18 and T98G cell proliferation and arrested cell cycle at the G0/G1 phase. In addition, FOXO1 facilitated cell senescence through regulation of the expression of sirtuin 1. Epithelial‑mesenchymal transition (EMT) is a complex process, which affects cell growth, invasion and metastasis. The results of the present study revealed that FOXO1 inhibited EMT and metastasis in GBM. These finding revealed a novel mechanism of FOXO1 in the suppression of tumorigenesis and metastasis of GBM cells and suggested that FOXO1 may be a potential therapeutic target for treating GBM.

Salidroside slows the progression of EA.hy926 cell senescence by regulating the cell cycle in an atherosclerosis model

Aging is the major risk factor for diseases of the cardiovascular system, such as coronary atherosclerotic heart disease, but little is known about the relationship between atherosclerosis (AS) and age-related declines in vascular structure and function. Here, we used histological analyses in combination with molecular biology techniques to show that lipid deposition in endothelial cell was accompanied by aging and growth arrest. Endothelial cell senescence is sufficient to cause AS; however, we found that salidroside reduced intracellular lipid deposition, slowed the progression of endothelial cell senescence and inhibited the expression of the senescence-related molecules and phosphorylated the retinoblastoma (Rb) protein. Further study confirmed that salidroside increased the percent of S phase cells in oxidized low-density lipoprotein (ox-LDL)-treated endothelial cells. Collectively, vascular endothelial cell function declined with age and AS, and our data suggested that salidroside prevented ox-LDL-treated endothelial cell senescence by promoting cell cycle progression from G0/G1 phase to S phase via Rb phosphorylation. We demonstrated for the first time the complex interactions between AS and endothelial cell senescence, and we believe that salidroside represents a promising therapy for senescence-related AS.

The Role of p16INK4a Pathway in Human Epidermal Stem Cell Self-Renewal, Aging and Cancer

The epidermis is a self-renewing tissue. The balance between proliferation and differentiation processes is tightly regulated to ensure the maintenance of the stem cell (SC) population in the epidermis during life. Aging and cancer may be considered related endpoints of accumulating damages within epidermal self-renewing compartment. p16^INK4a is a potent inhibitor of the G1/S-phase transition of the cell cycle. p16^INK4a governs the processes of SC self-renewal in several tissues and its deregulation may result in aging or tumor development. Keratinocytes are equipped with several epigenetic enzymes and transcription factors that shape the gene expression signatures of different epidermal layers and allow dynamic and coordinated expression changes to finely balance keratinocyte self-renewal and differentiation. These factors converge their activity in the basal layer to repress p16^INK4a expression, protecting cells from senescence, and preserving epidermal homeostasis and regeneration. Several stress stimuli may activate p16^INK4a expression that orchestrates cell cycle exit and senescence response. In the present review, we discuss the role of p16^INK4a regulators in human epidermal SC self-renewal, aging and cancer.

The Ubiquitin-like with PHD and Ring Finger Domains 1 (UHRF1)/DNA Methyltransferase 1 (DNMT1) Axis Is a Primary Regulator of Cell Senescence

As senescence develops, cells sequentially acquire diverse senescent phenotypes along with simultaneous multistage gene reprogramming. It remains unclear what acts as the key regulator of the collective changes in gene expression at initiation of senescent reprogramming. Here we analyzed time series gene expression profiles obtained in two different senescence models in human diploid fibroblasts: replicative senescence and H₂O₂-induced senescence. Our results demonstrate that suppression of DNA methyltransferase 1 (DNMT1)-mediated DNA methylation activity was an initial event prior to the display of senescent phenotypes. We identified seven DNMT1-interacting proteins, ubiquitin-like with PHD and ring finger domains 1 (UHRF1), EZH2, CHEK1, SUV39H1, CBX5, PARP1, and HELLS (also known as LSH (lymphoid-specific helicase) 1), as being commonly down-regulated at the same time point as DNMT1 in both senescence models. Knockdown experiments revealed that, among the DNMT1-interacting proteins, only UHRF1 knockdown suppressed DNMT1 transcription. However, UHRF1 overexpression alone did not induce DNMT1 expression, indicating that UHRF1 was essential but not sufficient for DNMT1 transcription. Although UHRF1 knockdown effectively induced senescence, this was significantly attenuated by DNMT1 overexpression, clearly implicating the UHRF1/DNMT1 axis in senescence. Bioinformatics analysis further identified WNT5A as a downstream effector of UHRF1/DNMT1-mediated senescence. Senescence-associated hypomethylation was found at base pairs -1569 to -1363 from the transcription start site of the WNT5A gene in senescent human diploid fibroblasts. As expected, WNT5A overexpression induced senescent phenotypes. Overall, our results indicate that decreased UHRF1 expression is a key initial event in the suppression of DNMT1-mediated DNA methylation and in the consequent induction of senescence via increasing WNT5A expression.

Elevated ΔNp63α Levels Facilitate Epidermal and Biliary Oncogenic Transformation

Unlike its family member p53, TP63 is rarely mutated in human cancer. However, ΔNp63α protein levels are often elevated in tumors of epithelial origin, such as squamous cell carcinoma and cholangiocarcinoma. To study the oncogenic properties of ΔNp63α in vivo, we generated transgenic mice overexpressing ΔNp63α from the Rosa26 locus promoter controlled by keratin 5-Cre. We found that these mice spontaneously develop epidermal cysts and ectopic ΔNp63α expression in the bile duct epithelium that leads to dilatation of the intrahepatic biliary ducts, to hepatic cyst formation and bile duct adenoma. Moreover, when subjected to models of 7,12-dimethylbenz[a]anthracene-based carcinogenesis, tumor initiation was increased in ΔNp63α transgenic mice in a gene dosage-dependent manner although ΔNp63α overexpression did not alter the sensitivity to 7,12-dimethylbenz[a]anthracene-induced cytotoxicity in vivo. However, keratinocytes isolated from ΔNp63α transgenic mice displayed increased survival and delayed cellular senescence compared with wild-type keratinocytes, marked by decreased p16^Ink4a and p19^Arf expression. Taken together, we show that increased ΔNp63α protein levels facilitate oncogenic transformation in the epidermis as well as in the bile duct.

BICD1 and Chromosome 18 Polymorphisms Associated With Recipients' Telomere Length Affect Kidney Allograft Function After Transplantation

BACKGROUND

Reports regarding recipient's nonmodifiable genetic factors affecting telomerase activity and thus allograft function are lacking. Therefore the aim of this study was to analyze the associations between recipients' rs2735940 hTERT, rs2630578 BICD1, and rs7235755 chromosome 18 polymorphisms and kidney function after transplantation.

METHODS

The study enrolled 119 white Polish kidney allograft recipients (64 men, 55 women; overall mean age, 47.3 ± 14.0 y). To identify genotypes of the studied polymorphisms, real-time polymerase chain reaction was performed.

RESULTS

There were statistically significant differences in distribution of rs7235755 chromosome 18 polymorphism genotypes and alleles between recipients with delayed graft function (DGF) and without DGF (P = .03). The presence of A allele was significantly associated with higher risk of DGF occurrence (AA + GA vs GG: OR, 3.25 [95% CI, 1.16-9.14]; P = .02; GA vs GG: OR, 4.00 [1.35-11.82]; P = .01). Analysis of the rs2630578 BICD1 gene polymorphism genotypes revealed statistically significant differences in long-term creatinine concentrations. The presence of C allele of this polymorphism was significantly associated with higher creatinine concentrations 24, 36, and 18-48 months after transplantation (GC + CC vs GG: P = .008, P = .008, and P = .01, respectively).

CONCLUSIONS

Recipients' polymorphisms of genes associated with telomere length, BICD1 and chromosome 18, but not hTERT, affect kidney allograft early and long-term function after transplantation. There is an urgent need for explanation of these observations in genome-wide association studies.

Cell cycle regulation of human DNA repair and chromatin remodeling genes

Maintenance of a genome requires DNA repair integrated with chromatin remodeling. We have analyzed six transcriptome data sets and one data set on translational regulation of known DNA repair and remodeling genes in synchronized human cells. These data are available through our new database: www.dnarepairgenes.com. Genes that have similar transcription profiles in at least two of our data sets generally agree well with known protein profiles. In brief, long patch base excision repair (BER) is enriched for S phase genes, whereas short patch BER uses genes essentially equally expressed in all cell cycle phases. Furthermore, most genes related to DNA mismatch repair, Fanconi anemia and homologous recombination have their highest expression in the S phase. In contrast, genes specific for direct repair, nucleotide excision repair, as well as non-homologous end joining do not show cell cycle-related expression. Cell cycle regulated chromatin remodeling genes were most frequently confined to G1/S and S. These include e.g. genes for chromatin assembly factor 1 (CAF-1) major subunits CHAF1A and CHAF1B; the putative helicases HELLS and ATAD2 that both co-activate E2F transcription factors central in G1/S-transition and recruit DNA repair and chromatin-modifying proteins and DNA double strand break repair proteins; and RAD54L and RAD54B involved in double strand break repair. TOP2A was consistently most highly expressed in G2, but also expressed in late S phase, supporting a role in regulating entry into mitosis. Translational regulation complements transcriptional regulation and appears to be a relatively common cell cycle regulatory mechanism for DNA repair genes. Our results identify cell cycle phases in which different pathways have highest activity, and demonstrate that periodically expressed genes in a pathway are frequently co-expressed. Furthermore, the data suggest that S phase expression and over-expression of some multifunctional chromatin remodeling proteins may set up feedback loops driving cancer cell proliferation.

Combination of SAHA and bortezomib up-regulates CDKN2A and CDKN1A and induces apoptosis of Epstein-Barr virus-positive Wp-restricted Burkitt lymphoma and lymphoblastoid cell lines

Epstein-Barr virus (EBV) latent proteins exert anti-apoptotic effects on EBV-transformed lymphoid cells by down-regulating BCL2L11 (BIM), CDKN2A (p16(INK4A) ) and CDKN1A (p21(WAF1) ). However, the potential therapeutic effects of targeting these anti-apoptotic mechanisms remain unexplored. Here, we tested both in vitro and in vivo effects of the combination of histone deacetylase (HDAC) and proteasome inhibitors on the apoptosis of six endemic Burkitt lymphoma (BL) lines of different latency patterns (types I and III and Wp-restricted) and three lymphoblastoid cell lines (LCLs). We found that the combination of HDAC and proteasome inhibitors (e.g. SAHA/bortezomib) synergistically induced the killing of Wp-restricted and latency III BL and LCLs but not latency I BL cells. The synergistic killing was due to apoptosis, as evidenced by the high percentage of annexin V positivity and strong cleavage of PARP1 (PARP) and CASP3 (caspase-3). Concomitantly, SAHA/bortezomib up-regulated the expression of CDKN2A and CDKN1A but did not affect the level of BCL2L11 or BHRF1 (viral homologue of BCL2). The apoptotic effects were dependent on reactive oxygen species generation. Furthermore, SAHA/bortezomib suppressed the growth of Wp-restricted BL xenografts in nude mice. This study provides the rationale to test the novel application of SAHA/bortezomib on the treatment of EBV-associated Wp-restricted BL and post-transplant lymphoproliferative disorder.

The molecular balancing act of p16(INK4a) in cancer and aging

p16(INK4a), located on chromosome 9p21.3, is lost among a cluster of neighboring tumor suppressor genes. Although it is classically known for its capacity to inhibit cyclin-dependent kinase (CDK) activity, p16(INK4a) is not just a one-trick pony. Long-term p16(INK4a) expression pushes cells to enter senescence, an irreversible cell-cycle arrest that precludes the growth of would-be cancer cells but also contributes to cellular aging. Importantly, loss of p16(INK4a) is one of the most frequent events in human tumors and allows precancerous lesions to bypass senescence. Therefore, precise regulation of p16(INK4a) is essential to tissue homeostasis, maintaining a coordinated balance between tumor suppression and aging. This review outlines the molecular pathways critical for proper p16(INK4a) regulation and emphasizes the indispensable functions of p16(INK4a) in cancer, aging, and human physiology that make this gene special.

Oxidative stress and chromatin remodeling in chronic obstructive pulmonary disease and smoking-related diseases

SIGNIFICANCE

Chronic obstructive pulmonary disease (COPD) is predominantly a tobacco smoke-triggered disease with features of chronic low-grade systemic inflammation and aging (inflammaging) of the lung associated with steroid resistance induced by cigarette smoke (CS)-mediated oxidative stress. Oxidative stress induces various kinase signaling pathways leading to chromatin modifications (histone acetylation/deacetylation and histone methylation/demethylation) in inflammation, senescence, and steroid resistance.

RECENT ADVANCES

Histone mono-, di-, or tri-methylation at lysine residues result in either gene activation (H3K4, H3K36, and H3K79) or repression (H3K9, H3K27, and H3K20). Cross-talk occurs between various epigenetic marks on histones and DNA methylation. Both CS and oxidants alter histone acetylation/deacetylation and methylation/demethylation leading to enhanced proinflammatory gene expression. Chromatin modifications occur in lungs of patients with COPD. Histone deacetylase 2 (HDAC2) reduction (levels and activity) is associated with steroid resistance in response to oxidative stress.

CRITICAL ISSUES

Histone modifications are associated with DNA damage/repair and epigenomic instability as well as premature lung aging, which have implications in the pathogenesis of COPD. HDAC2/SIRTUIN1 (SIRT1)-dependent chromatin modifications are associated with DNA damage-induced inflammation and senescence in response to CS-mediated oxidative stress.

FUTURE DIRECTIONS

Understanding CS/oxidative stress-mediated chromatin modifications and the cross-talk between histone acetylation and methylation will demonstrate the involvement of epigenetic regulation of chromatin remodeling in inflammaging. This will lead to identification of novel epigenetic-based therapies against COPD and other smoking-related lung diseases. Pharmacological activation of HDAC2/SIRT1 or reversal of their oxidative post-translational modifications may offer therapies for treatment of COPD and CS-related diseases based on epigenetic histone modifications.

Histone deacetylase 3 (HDAC3) participates in the transcriptional repression of the p16 (INK4a) gene in mammary gland of the female rat offspring exposed to an early-life high-fat diet

Maternal exposure to environmental agents throughout pregnancy and lactation may affect offspring's mammary gland growth and alter the epigenome. This may predispose the offspring's mammary glands to be more susceptible to carcinogenesis. The purpose of this study was to examine the effect of a maternal high-fat diet on the regulation of p16 (INK4a) gene expression in the mammary gland of rat offspring. Timed-pregnant Sprague-Dawley rats were fed one of the two diets, a control (C, 16% of fat) or a high fat (HF, 45% of fat) diet, throughout gestation and lactation and sacrificed at 12 weeks of age. Compared with C, HF offspring showed a decrease of p16 (INK4a) gene expression in the mammary gland at both mRNA and protein levels. Chromatin immunoprecipitation (ChIP) assay demonstrated that the downregulation of p16 (INK4a) transcription in HF offspring was associated with reduced acetylation of histone H4 and increased recruitment of histone deacetylase 3 (HDAC3) within the p16 (INK4a) promoter region, but was not associated with acetylation of histone H3 or HDAC1. Methylated DNA immunoprecipitation (MeDIP) did not detect differences in methylation at different regions of the p16 (INK4a) gene between C and HF offspring. We conclude that maternal high fat exposure represses p16 (INK4a) gene expression in the mammary gland of offspring through changes of histone modifications and HDAC3 binding activity within the regulatory regions of the p16 (INK4a) gene.

Role of histone deacetylase 2 in epigenetics and cellular senescence: implications in lung inflammaging and COPD

Histone deacetylase 2 (HDAC2) is a class I histone deacetylase that regulates various cellular processes, such as cell cycle, senescence, proliferation, differentiation, development, apoptosis, and glucocorticoid function in inhibiting inflammatory response. HDAC2 has been shown to protect against DNA damage response and cellular senescence/premature aging via an epigenetic mechanism in response to oxidative stress. These phenomena are observed in patients with chronic obstructive pulmonary disease (COPD). HDAC2 is posttranslationally modified by oxidative/carbonyl stress imposed by cigarette smoke and oxidants, leading to its reduction via an ubiquitination-proteasome dependent degradation in lungs of patients with COPD. In this perspective, we have discussed the role of HDAC2 posttranslational modifications and its role in regulation of inflammation, histone/DNA epigenetic modifications, DNA damage response, and cellular senescence, particularly in inflammaging, and during the development of COPD. We have also discussed the potential directions for future translational research avenues in modulating lung inflammaging and cellular senescence based on epigenetic chromatin modifications in diseases associated with increased oxidative stress.

FOXM1 induces a global methylation signature that mimics the cancer epigenome in head and neck squamous cell carcinoma

The oncogene FOXM1 has been implicated in all major types of human cancer. We recently showed that aberrant FOXM1 expression causes stem cell compartment expansion resulting in the initiation of hyperplasia. We have previously shown that FOXM1 regulates HELLS, a SNF2/helicase involved in DNA methylation, implicating FOXM1 in epigenetic regulation. Here, we have demonstrated using primary normal human oral keratinocytes (NOK) that upregulation of FOXM1 suppressed the tumour suppressor gene p16(INK4A) (CDKN2A) through promoter hypermethylation. Knockdown of HELLS using siRNA re-activated the mRNA expression of p16(INK4A) and concomitant downregulation of two DNA methyltransferases DNMT1 and DNMT3B. The dose-dependent upregulation of endogenous FOXM1 (isoform B) expression during tumour progression across a panel of normal primary NOK strains (n = 8), dysplasias (n = 5) and head and neck squamous cell carcinoma (HNSCC) cell lines (n = 11) correlated positively with endogenous expressions of HELLS, BMI1, DNMT1 and DNMT3B and negatively with p16(INK4A) and involucrin. Bisulfite modification and methylation-specific promoter analysis using absolute quantitative PCR (MS-qPCR) showed that upregulation of FOXM1 significantly induced p16(INK4A) promoter hypermethylation (10-fold, P<0.05) in primary NOK cells. Using a non-bias genome-wide promoter methylation microarray profiling method, we revealed that aberrant FOXM1 expression in primary NOK induced a global hypomethylation pattern similar to that found in an HNSCC (SCC15) cell line. Following validation experiments using absolute qPCR, we have identified a set of differentially methylated genes, found to be inversely correlated with in vivo mRNA expression levels of clinical HNSCC tumour biopsy samples. This study provided the first evidence, using primary normal human cells and tumour tissues, that aberrant upregulation of FOXM1 orchestrated a DNA methylation signature that mimics the cancer methylome landscape, from which we have identified a unique FOXM1-induced epigenetic signature which may have clinical translational potentials as biomarkers for early cancer screening, diagnostic and/or therapeutic interventions.

Quantitative proteomic analysis of mouse embryonic fibroblasts and induced pluripotent stem cells using 16O/18O labeling

Induced pluripotent stem cells (iPSC) hold great promise for regenerative medicine as well as for investigations into the pathogenesis and treatment of various diseases. Understanding of key intracellular signaling pathways and protein targets that control development of iPSC from somatic cells is essential for designing new approaches to improve reprogramming efficiency. Here, we report the development and application of an integrated quantitative proteomics platform for investigating differences in protein expressions between mouse embryonic fibroblasts (MEF) and MEF-derived iPSC. This platform consists of 16O/18O labeling, multidimensional peptide separation coupled with tandem mass spectrometry, and data analysis with UNiquant software. With this platform, a total of 2481 proteins were identified and quantified from the 16O/18O-labeled MEF-iPSC proteome mixtures with a false discovery rate of 0.01. Among them, 218 proteins were significantly upregulated, while 247 proteins were significantly downregulated in iPSC compared to MEF. Many nuclear proteins, including Hdac1, Dnmt1, Pcna, Ccnd1, Smarcc1, and subunits in DNA replication and RNA polymerase II complex, were found to be enhanced in iPSC. Protein network analysis revealed that Pcna functions as a hub orchestrating complicated mechanisms including DNA replication, epigenetic inheritance (Dnmt1), and chromatin remodeling (Smarcc1) to reprogram MEF and maintain stemness of iPSC.

WW domain-containing E3 ubiquitin protein ligase 1 (WWP1) delays cellular senescence by promoting p27(Kip1) degradation in human diploid fibroblasts

WW domain-containing E3 ubiquitin protein ligase 1 (WWP1) plays an important role in the proliferation of tumor cells and the lifespan of Caenorhabditis elegans. However, the role of WWP1 in cellular senescence is still unknown. Here, we show that the expression patterns of p27(Kip1) and WWP1 are inversely correlated during cellular senescence. Moreover, the overexpression of WWP1 delayed senescence, whereas the knockdown of WWP1 led to premature senescence in human fibroblasts. Furthermore, we demonstrate that WWP1 repressed endogenous p27(Kip1) expression through ubiquitin-proteasome-mediated degradation. Additionally, WWP1 had a strong preference for catalyzing the Lys-48-linked polyubiquitination of p27(Kip1) in vitro. Finally, we demonstrate that WWP1 markedly inhibited the replicative senescence induced by p27(Kip1) by promoting p27(Kip1) degradation. Therefore, our study provides a new molecular mechanism for the regulation of cellular senescence.

Regulatory mechanisms of tumor suppressor P16(INK4A) and their relevance to cancer

P16(INK4A) (also known as P16 and MTS1), a protein consisting exclusively of four ankyrin repeats, is recognized as a tumor suppressor mainly because of the prevalence of genetic inactivation of the p16(INK4A) (or CDKN2A) gene in virtually all types of human cancers. However, it has also been shown that an elevated level of expression (upregulation) of P16 is involved in cellular senescence, aging, and cancer progression, indicating that the regulation of P16 is critical for its function. Here, we discuss the regulatory mechanisms of P16 function at the DNA level, the transcription level, and the posttranscriptional level, as well as their implications for the structure-function relationship of P16 and for human cancers.

Transcriptional activation of the senescence regulator Lsh by E2F1

Lsh, a protein related to the SNF2 family of chromatin-remodeling ATPases, is a major epigenetic regulator that is essential for DNA methylation and histone acetylation at repetitive elements. Lsh represses endogenous p16(INK4a) expression by recruiting HDAC to the p16(INK4a) promoter, which in turn delays cell senescence. However, the molecular mechanisms that govern loss of Lsh expression during cellular senescence have yet to be elucidated. Here we investigate the transcriptional regulation of the human Lsh promoter. We find that the minimal Lsh promoter is located between positions -216 and -119 relative to the transcription start site, and contains two putative E2F binding sites. Ectopic E2F1 increases expression of Lsh at both transcriptional and translational levels. E2F1 physically interacts with the Lsh promoter by binding to each of the two putative binding sites and transactivates the Lsh promoter. E2F1 also induces Lsh protein expression and transactivates the Lsh promoter in 2BS cells. At the same time, E2F1-induced Lsh promoter activity is reduced in senescent cells compared to young cells. These results indicate that E2F1 plays a crucial role in transcriptional control of the human Lsh gene and the decrease of Lsh expression in senescent cells is related to the repression of E2F1.

LSH and G9a/GLP complex are required for developmentally programmed DNA methylation

LSH, a member of the SNF2 family of chromatin remodeling ATPases encoded by the Hells gene, is essential for normal levels of DNA methylation in the mammalian genome. While the role of LSH in the methylation of repetitive DNA sequences is well characterized, its contribution to the regulation of DNA methylation and the expression of protein-coding genes has not been studied in detail. In this report we investigate genome-wide patterns of DNA methylation at gene promoters in Hells(-/-) mouse embryonic fibroblasts (MEFs). We find that in the absence of LSH, DNA methylation is lost or significantly reduced at ∼20% of all normally methylated promoter sequences. As a consequence, a large number of genes are misexpressed in Hells(-/-) MEFs. Comparison of Hells(-/-) MEFs with wild-type MEFs and embryonic stem (ES) cells suggests that LSH is important for de novo DNA methylation events that accompany the establishment and differentiation of embryonic lineage cells. We further show that the generation of normal DNA methylation patterns and stable gene silencing at specific promoters require cooperation between LSH and the G9a/GLP complex of histone methylases. At such loci, G9a recruitment is compromised when LSH is absent or greatly reduced. Taken together, our data suggest a mechanism whereby LSH promotes binding of DNA methyltransferases and the G9a/GLP complex to specific loci and facilitates developmentally programmed DNA methylation and stable gene silencing during lineage commitment and differentiation.

Downstream targets of FOXM1: CEP55 and HELLS are cancer progression markers of head and neck squamous cell carcinoma

We recently showed that upregulation of a key oncogene FOXM1 precedes head and neck squamous cell carcinoma (HNSCC) malignancy. Furthermore, we also identified a centrosomal protein CEP55 and a DNA helicase/putative stem cell marker HELLS, which are both downstream targets of FOXM1. In this study, we have investigated the expression profiles of CEP55 and HELLS using immunohistochemistry and quantified by digital densitometry in a tissue panel (20 samples) consisting of normal oral mucosa, dysplasias, HNSCC and lymph node metastasis (LnMet) samples. Furthermore, we corroborated our findings using absolute real-time PCR (qPCR) on a panel of 12 primary normal human oral keratinocytes, five dysplasia and 10 HNSCC cell lines. Finally, we validated our study using bioinformatics microarray analysis on an independent HNSCC patient cohort (four normal and 16 tumours). In normal oral mucosa, CEP55 protein was detected at very low level within the upper differentiated layers. In contrast, CEP55 was highly expressed in oral dysplasia whereas only moderate expression was detected in HNSCC and LnMet. Low level of HELLS expression was detected in the basal cell layer of the normal oral mucosa, moderate level was seen in dysplasia and high levels in both HNSCC and LnMet. These expression patterns were consistent with both qPCR data from the cell line panel and microarray data analysis of TNM-stage defined HNSCC samples confirming the progressive expression pattern of CEP55 and HELLS. To our knowledge, this is the first pilot study demonstrating that both CEP55 and HELLS mRNA and protein expression positively correlate with pre-malignancy and HNSCC progression. This study provides strong evidence that CEP55 and HELLS may be used in conjunction with FOXM1 as a biomarker set for early cancer detection and indicators of malignant conversion and progression.