PR55α-controlled protein phosphatase 2A inhibits p16 expression and blocks cellular senescence induction by γ-irradiation.

Cellular senescence is a permanent cell cycle arrest that can be triggered by both internal and external genotoxic stressors, such as telomere dysfunction and DNA damage. The execution of senescence is mainly by two pathways, p16/RB and p53/p21, which lead to CDK4/6 inhibition and RB activation to block cell cycle progression. While the regulation of p53/p21 signaling in response to DNA damage and other insults is well-defined, the regulation of the p16/RB pathway in response to various stressors remains poorly understood. Here, we report a novel function of PR55α, a regulatory subunit of PP2A Ser/Thr phosphatase, as a potent inhibitor of p16 expression and senescence induction by ionizing radiation (IR), such as γ-rays. The results show that ectopic PR55α expression in normal pancreatic cells inhibits p16 transcription, increases RB phosphorylation, and blocks IR-induced senescence. Conversely, PR55α-knockdown by shRNA in pancreatic cancer cells elevates p16 transcription, reduces RB phosphorylation, and triggers senescence induction after IR. Furthermore, this PR55α function in the regulation of p16 and senescence is p53-independent because it was unaffected by the mutational status of p53. Moreover, PR55α only affects p16 expression but not p14 (ARF) expression, which is also transcribed from the same CDKN2A locus but from an alternative promoter. In normal human tissues, levels of p16 and PR55α proteins were inversely correlated and mutually exclusive. Collectively, these results describe a novel function of PR55α/PP2A in blocking p16/RB signaling and IR-induced cellular senescence.

PTEN-mediated dephosphorylation of 53BP1 confers cellular resistance to DNA damage in cancer cells.

Homologous recombination (HR) repair for DNA double-strand breaks (DSBs) is critical for maintaining genome stability and conferring the resistance of tumor cells to chemotherapy. Nuclear PTEN which contains both phosphatidylinositol 3,4,5-trisphosphate 3-phosphatase and protein phosphatase plays a key role in HR repair, but the underlying mechanism remains largely elusive. We find that SUMOylated PTEN promotes HR repair but represses nonhomologous end joining (NHEJ) repair by directly dephosphorylating TP53-binding protein 1 (53BP1). During DNA damage responses (DDR), tumor suppressor ARF (p14ARF) was phosphorylated and then interacted efficiently with PTEN, thus promoting PTEN SUMOylation as an atypical SUMO E3 ligase. Interestingly, SUMOylated PTEN was subsequently recruited to the chromatin at DSB sites. This was because SUMO1 that was conjugated to PTEN was recognized and bound by the SUMO-interacting motif (SIM) of breast cancer type 1 susceptibility protein (BRCA1), which has been located to the core of 53BP1 foci on chromatin during S/G2 stage. Furthermore, these chromatin-loaded PTEN directly and specifically dephosphorylated phosphothreonine-543 (pT543) of 53BP1, resulting in the dissociation of the 53BP1 complex, which facilitated DNA end resection and ongoing HR repair. SUMOylation-site-mutated PTENK254R mice also showed decreased DNA damage repair in vivo. Blocking the PTEN SUMOylation pathway with either a SUMOylation inhibitor or a p14ARF(2-13) peptide sensitized tumor cells to chemotherapy. Our study therefore provides a new mechanistic understanding of PTEN in HR repair and clinical intervention of chemoresistant tumors.

Fusobacterium nucleatum triggers senescence phenotype in gingival epithelial cells.

The prevalence of periodontitis increases with physiological aging. However, whether bacteria associated with periodontal diseases foster aging and the mechanisms by which they may do so are unknown. Herein, we hypothesize that Fusobacterium nucleatum, a microorganism associated with periodontitis and several other age-related disorders, triggers senescence, a chief hallmark of aging responsible to reduce tissue repair capacity. Our study analyzed the senescence response of gingival epithelial cells and their reparative capacity upon long-term exposure to F. nucleatum. Specifically, we assessed (a) cell cycle arrest by analyzing the cyclin-dependent kinase inhibitors p16INK4a and p14ARF and their downstream cascade (pRb, p53, and p21) at both gene and protein levels, (b) lysosomal mediated dysfunction by using assays targeting the expression and activity of the senescence-associated ß-galactosidase (SA-ß-Gal) enzyme, and (c) nuclear envelope breakdown by assessing the expression of Lamin-B1. The consequences of the senescence phenotype mediated by F. nucleatum were further assessed using wound healing assays. Our results revealed that prolonged exposure to F. nucleatum promotes an aging-like phenotype as evidenced by the increased expression of pro-senescence markers (p16INK4a , p21, and pRb) and SA-ß-Gal activity and reduced expression of the counter-balancing cascade (p14ARF and p53) and Lamin-B1. Furthermore, we also noted impaired wound healing capacity of gingival epithelial cells upon prolong bacterial exposure, which was consistent with the senescence-induced phenotype. Together, our findings provide a proof-of-concept evidence that F. nucleatum triggers a pro-senescence response in gingival epithelial cells. This might affect periodontal tissue homeostasis by reducing its repair capacity and, consequently, increasing susceptibility to periodontitis during aging.

MDM2-Targeting Reassembly Peptide (TRAP) Nanoparticles for p53-Based Cancer Therapy.

Gene mutations and functional inhibition are the major obstacles for p53-mediated oncotherapy. For p53-wild-type tumors, the underlying mechanisms of functional inhibition of p53 during oncogenesis are unknown. The results reveal that the expression of the MDM2 inhibitor ARF is inhibited in p53-wild-type tumors, indicating that the restoration of ARF could be a potential oncotherapy strategy for p53-wild-type tumors. Therefore, ARF-mimetic MDM2-targeting reassembly peptide nanoparticles (MtrapNPs) for p53-based tumor therapy is developed. The results elucidated that the MtrapNPs respond to and form a nanofiber structure with MDM2. By trapping MDM2, the MtrapNPs stabilize and activate p53 for the inhibition of p53-wild-type tumors. In most cases, reactivated mutant p53 is inhibited and degraded by MDM2. In the present study, MtrapNPs are used to load and deliver arsenic trioxide, a p53 mutation rescuer, for p53-mutated tumor treatment in both orthotopic and metastatic models, and they exhibit significant therapeutic effects. Therefore, the study provides evidence supporting a link between decreased ARF expression and tumor development in patients with p53-wild-type tumors. Thus, the MDM2-trap strategy, which addresses both the inhibition and mutations of p53, is an efficient strategy for the treatment of p53-mutated tumors.

MLL3 regulates the CDKN2A tumor suppressor locus in liver cancer.

Mutations in genes encoding components of chromatin modifying and remodeling complexes are among the most frequently observed somatic events in human cancers. For example, missense and nonsense mutations targeting the mixed lineage leukemia family member 3 (MLL3, encoded by KMT2C) histone methyltransferase occur in a range of solid tumors, and heterozygous deletions encompassing KMT2C occur in a subset of aggressive leukemias. Although MLL3 loss can promote tumorigenesis in mice, the molecular targets and biological processes by which MLL3 suppresses tumorigenesis remain poorly characterized. Here, we combined genetic, epigenomic, and animal modeling approaches to demonstrate that one of the mechanisms by which MLL3 links chromatin remodeling to tumor suppression is by co-activating the Cdkn2a tumor suppressor locus. Disruption of Kmt2c cooperates with Myc overexpression in the development of murine hepatocellular carcinoma (HCC), in which MLL3 binding to the Cdkn2a locus is blunted, resulting in reduced H3K4 methylation and low expression levels of the locus-encoded tumor suppressors p16/Ink4a and p19/Arf. Conversely, elevated KMT2C expression increases its binding to the CDKN2A locus and co-activates gene transcription. Endogenous Kmt2c restoration reverses these chromatin and transcriptional effects and triggers Ink4a/Arf-dependent apoptosis. Underscoring the human relevance of this epistasis, we found that genomic alterations in KMT2C and CDKN2A were associated with similar transcriptional profiles in human HCC samples. These results collectively point to a new mechanism for disrupting CDKN2A activity during cancer development and, in doing so, link MLL3 to an established tumor suppressor network.

TYMS promotes genomic instability and tumor progression in Ink4a/Arf null background.

We previously showed that elevated TYMS exhibits oncogenic properties and promotes tumorigenesis after a long latency, suggesting cooperation with sequential somatic mutations. Here we report the cooperation of ectopic expression of human TYMS with loss of Ink4a/Arf, one of the most commonly mutated somatic events in human cancer. Using an hTS/Ink4a/Arf -/- genetically engineered mouse model we showed that deregulated TYMS expression in Ink4a/Arf null background accelerates tumorigenesis and metastasis. In addition, tumors from TYMS-expressing mice were associated with a phenotype of genomic instability including enhanced double strand DNA damage, aneuploidy and loss of G1/S checkpoint. Downregulation of TYMS in vitro decreased cell proliferation and sensitized tumor cells to antimetabolite chemotherapy. In addition, depletion of TYMS in vivo by TYMS shRNA reduced tumor incidence, delayed tumor progression and prolonged survival in hTS/Ink4a/Arf -/- mice. Our data shows that activation of TYMS in Ink4a/Arf null background enhances uncontrolled cell proliferation and tumor growth, supporting the development of new agents and strategies targeting TYMS to delay tumorigenesis and prolong survival.

hCINAP alleviates senescence by regulating MDM2 via p14ARF and the HDAC1/CoREST complex.

Cellular senescence is a major process affected by multiple signals and coordinated by a complex signal response network. Identification of novel regulators of cellular senescence and elucidation of their molecular mechanisms will aid in the discovery of new treatment strategies for aging-related diseases. In the present study, we identified human coilin-interacting nuclear ATPase protein (hCINAP) as a negative regulator of aging. Depletion of cCINAP significantly shortened the lifespan of Caenorhabditis elegans and accelerated primary cell aging. Moreover, mCINAP deletion markedly promoted organismal aging and stimulated senescence-associated secretory phenotype in the skeletal muscle and liver from mouse models of radiation-induced senescence. Mechanistically, hCINAP functions through regulating MDM2 status by distinct mechanisms. On the one hand, hCINAP decreases p53 stability by attenuating the interaction between p14ARF and MDM2; on the other hand, hCINAP promotes MDM2 transcription via inhibiting the deacetylation of H3K9ac in the MDM2 promoter by hindering the HDAC1/CoREST complex integrity. Collectively, our data demonstrate that hCINAP is a negative regulator of aging and provide insight into the molecular mechanisms underlying the aging process.

p14ARF ameliorates inflammation and airway remodeling in nitric acid aerosol inhalation-induced bronchiolitis obliterans.

BACKGROUND: To investigate the protective effect of p14ARF in a nitric acid (NA) aerosol inhalation-induced bronchiolitis obliterans (BO) mouse model and its potential regulatory mechanism. METHODS: A BO mouse model was established by NA aerosol inhalation. The expressions of p14ARF, phosphatidylinositol-3-kinase (PI3K), and protein kinase B (AKT) were detected by quantitative reverse transcription PCR (qRT-PCR) and western blot (WB). Hematoxylin (HE) staining, Masson staining, and periodic acid-Schiff (PAS) staining observed pulmonary histological changes. TdT-mediated dUTP nick end labeling (TUNEL) staining detected pulmonary cell apoptosis, and enzyme-linked immunosorbent assay (ELISA) measured matrix metalloproteinase-2 (MMP-2), MMP-9, tissue inhibitor of metalloproteinase-1 (TIMP-1), interleukon-6 (IL-6), and transforminh growth factor-ß (TGF-ß) levels in lung tissue and bronchoalveolar lavage fluid (BALF). RESULTS: The expressions of p14ARF, PI3K, and AKT showed a time gradient change, with a decrease trend (*P < 0.05 and **P < 0.01). Severe inflammatory infiltration and tracheal fibrosis were found in lung tissue in the modeling group (BO group) compared with the control group (Con group). The pH, PaO2, and PaO2/FiO2 values significantly reduced, while the PaCO2 value and the number of TUNEL-positive cells increased in BO group (P < 0.05). In addition, MMP-2, MMP-9, IL-6, and TGF-ß levels remarkably increased, with an increase in the number of white blood cells, neutrophils, and lymphocytes in BO group (P < 0.05). Furthermore, p14ARF up-regulation reversed the trend of the aforementioned indexes in BO mice. CONCLUSIONS: p14ARF ameliorated the inflammatory response and airway remodeling in a BO mouse model via the PI3K/AKT pathway.

Immortalized murine tenocyte cells: a novel and innovative tool for tendon research.

Primary tenocytes rapidly undergo senescence and a phenotypic drift upon in vitro monolayer culture, which limits tendon research. The Ink4a/Arf locus encodes the proteins p16Ink4a/Arf and p14ARF (p19ARF in mice) that regulate cell cycle progression and senescence. We here established an immortalized cell line using tenocytes isolated from Ink4a/Arf deficient mice (Ink4a/Arf-/-). These cells were investigated at three distinct time points, at low (2-5), intermediate (14-17) and high (35-44) passages. Wild-type cells at low passage (2-5) served as controls. Ink4a/Arf-/- tenocytes at all stages were comparable to wild-type cells regarding morphology, expression of tenogeneic genes (collagen type 1, 3 and 5, Scleraxis, Tenomodulin and Tenascin-C), and surface markers (CD29, CD44 and CD105) and form 3D tendon-like structures. Importantly, Ink4a/Arf-/- tenocytes maintained their phenotypic features and proliferation potential in culture for more than 40 passages and also following freeze-thaw cycles. In contrast, wild-type tenocytes underwent senescence starting in passage 6. These data define Ink4a/Arf-/- tenocytes as novel tool for in vitro tendon research and as valuable in vitro alternative to animal experiments.

Induction of Immune-Stimulating Factors and Oncolysis Upon p14ARF Gene Transfer in Melanoma Cell Lines.

Together with an anti-tumor immune response, oncolysis using a recombinant viral vector promises to eliminate cancer cells by both gene transfer and host-mediated functions. In this study we explore oncolysis induced by nonreplicating adenoviral vectors used for p14ARF and interferon-ß (hIFNß) gene transfer in human melanoma cell lines, revealing an unexpected role for p14ARF in promoting cellular responses predictive of immune stimulation. Oncolysis was confirmed when UACC-62 (p53 wild-type) cells succumbed upon p14ARF gene transfer in vitro, whereas SK-Mel-29 (p53-mutant) benefitted from its combination with hIFNß. In the case of UACC-62, in situ gene therapy in nude mice yielded reduced tumor progression in response to the p14ARF and hIFNß combination. Potential for immune stimulation was revealed where p14ARF gene transfer in vitro was sufficient to induce emission of immunogenic cell death factors in UACC-62 and upregulate pro-immune genes, including IRF1, IRF7, IRF9, ISG15, TAP-1, and B2M. In SK-Mel-29, p14ARF gene transfer induced a subset of these factors. hIFNß was, as expected, sufficient to induce these immune-stimulating genes in both cell lines. This work is a significant advancement for our melanoma gene therapy strategy because we revealed not only the induction of oncolysis, but also the potential contribution of p14ARF to immune stimulation.

Computational screening and analysis of deleterious nsSNPs in human p14ARF (CDKN2A gene) protein using molecular dynamic simulation approach.

Cyclin-dependent kinase inhibitor 2 A (CDKN2A) gene belongs to the cyclin-dependent kinase family that code for two transcripts (p16INK4A and p14ARF), both work as tumor suppressors proteins. The mutation that occurs in the p14ARF protein can lead to different types of cancers. Single nucleotide polymorphisms (SNPs) are an important type of genetic alteration that can lead to different types of diseases. In this study, we applied the computational strategy on human p14ARF protein to identify the potential deleterious nsSNPs and check their impact on the structure, function, and protein stability. We applied more than ten prediction tools to screen the retrieved 288 nsSNPs, consequently extracting four deleterious nsSNPs i.e., rs139725688 (R10G), rs139725688 (R21W), rs374360796 (F23L) and rs747717236 (L124R). Homology modeling, conservation and conformational analysis of mutant models were performed to examine the divergence of these variants from the native p14ARF structure. All-atom molecular dynamics simulation revealed a significant impact of these mutations on protein stability, compactness, globularity, solvent accessibility and secondary structure elements. Protein-protein interactions indicated that p14ARF operates as a hub linking clusters of different proteins and that changes in p14ARF may result in the disassociation of numerous signal cascades. Our current study is the first survey of computational analysis on p14ARF protein that determines the association of these nsSNPs with the altered function of p14ARF protein and leads to the development of various types of cancers. This research proposes the described functional SNPs as possible targets for proteomic investigations, diagnostic procedures, and treatments.Communicated by Ramaswamy H. Sarma.

Impact of Transcript (p16/p14ARF) Alteration on Cancer Risk in CDKN2A Germline Pathogenic Variant Carriers.

BACKGROUND: Few studies have evaluated the relationship between CDKN2A germline pathogenic variants (GPV), transcript (p16/p14ARF) alteration, and cancer risk. METHODS: Standardized incidence ratios (SIRs) comparing cancer risk with the general population were calculated for 385 CDKN2A GPV carriers from 2 large cohorts (259 United States and 126 Swedish individuals) using Poisson regression; statistical significance was defined as P less than .002 (Bonferroni correction). Cumulative incidence is reported for melanoma and nonmelanoma cancer. RESULTS: Incidence was increased for melanoma (SIR = 159.8, 95% confidence interval [CI] = 132.1 to 193.2), pancreatic cancer (SIR = 24.1, 95% CI = 14.7 to 39.4), head and neck squamous cell carcinoma (SIR = 16.2, 95% CI = 9.5 to 27.6), and lung cancer (SIR = 5.6, 95% CI = 3.4 to 9.1) in GPV carriers. Similar associations were observed with p16 alteration. Combined p16 and p14ARF alteration was associated with increased incidence of esophageal cancer (SIR = 16.7, 95% CI = 5.7 to 48.9) and malignant peripheral nerve sheath tumor (SIR = 113.0, 95% CI = 16.4 to 780.9), although cancer events were limited (n < 5 for each malignancy). Cumulative incidence at age 70 years for melanoma and nonmelanoma cancer was 68.3% (95% CI = 68.0% to 68.6%) and 35.2% (95% CI = 34.9% to 35.6%), respectively. A total 89% of smoking-related cancers (lung, head and neck squamous cell carcinoma, pancreatic, esophageal) occurred in ever smokers. CONCLUSION: These findings highlight the impact of p16 and p14ARF alteration on cancer risk. Smoking was an important risk factor for smoking-related cancers in our study.

Bivalent binding of p14ARF to MDM2 RING and acidic domains inhibits E3 ligase function.

ARF tumor suppressor protein is a key regulator of the MDM2-p53 signaling axis. ARF interferes with MDM2-mediated ubiquitination and degradation of p53 by sequestering MDM2 in the nucleolus and preventing MDM2-p53 interaction and nuclear export of p53. Moreover, ARF also directly inhibits MDM2 ubiquitin ligase (E3) activity, but the mechanism remains elusive. Here, we apply nuclear magnetic resonance and biochemical analyses to uncover the mechanism of ARF-mediated inhibition of MDM2 E3 activity. We show that MDM2 acidic and zinc finger domains (AD-ZnF) form a weak intramolecular interaction with the RING domain, where the binding site overlaps with the E2∼ubiquitin binding surface and thereby partially reduces MDM2 E3 activity. Binding of human N-terminal 32 residues of p14ARF to the acidic domain of MDM2 strengthens the AD-ZnF-RING domain interaction. Furthermore, the N-terminal RxFxV motifs of p14ARF participate directly in the MDM2 RING domain interaction. This bivalent binding mode of p14ARF to MDM2 acidic and RING domains restricts E2∼ubiquitin recruitment and massively hinders MDM2 E3 activity. These findings elucidate the mechanism by which ARF inhibits MDM2 E3 activity.

CDKN2A exon 1B deletion predisposing to melanoma and neural system tumour syndrome.

CDKN2A at chromosome positon 9p21 is a tumour suppressor gene encoding the cell cycle regulators p16 and p14ARF. While melanoma is associated with variants affecting both transcripts, families with mutations involving the p14ARF-specific exon 1B may be predisposed to central nervous system tumours. We describe a family with a deletion of exon 1B in CDKN2A, who had multiple cutaneous melanomas, neural tumours and various malignancies.

The Senescence Markers p16INK4A, p14ARF/p19ARF, and p21 in Organ Development and Homeostasis.

It is widely accepted that senescent cells accumulate with aging. They are characterized by replicative arrest and the release of a myriad of factors commonly called the senescence-associated secretory phenotype. Despite the replicative cell cycle arrest, these cells are metabolically active and functional. The release of SASP factors is mostly thought to cause tissue dysfunction and to induce senescence in surrounding cells. As major markers for aging and senescence, p16INK4, p14ARF/p19ARF, and p21 are established. Importantly, senescence is also implicated in development, cancer, and tissue homeostasis. While many markers of senescence have been identified, none are able to unambiguously identify all senescent cells. However, increased levels of the cyclin-dependent kinase inhibitors p16INK4A and p21 are often used to identify cells with senescence-associated phenotypes. We review here the knowledge of senescence, p16INK4A, p14ARF/p19ARF, and p21 in embryonic and postnatal development and potential functions in pathophysiology and homeostasis. The establishment of senolytic therapies with the ultimate goal to improve healthy aging requires care and detailed knowledge about the involvement of senescence and senescence-associated proteins in developmental processes and homeostatic mechanism. The review contributes to these topics, summarizes open questions, and provides some directions for future research.

Helicobacter pylori pathogen inhibits cellular responses to oncogenic stress and apoptosis.

Helicobacter pylori (H. pylori) is a common gastric pathogen that infects approximately half of the world's population. Infection with H. pylori can lead to diverse pathological conditions, including chronic gastritis, peptic ulcer disease, and cancer. The latter is the most severe consequence of H. pylori infection. According to epidemiological studies, gastric infection with H. pylori is the strongest known risk factor for non-cardia gastric cancer (GC), which remains one of the leading causes of cancer-related deaths worldwide. However, it still remains to be poorly understood how host-microbe interactions result in cancer development in the human stomach. Here we focus on the H. pylori bacterial factors that affect the host ubiquitin proteasome system. We investigated E3 ubiquitin ligases SIVA1 and ULF that regulate p14ARF (p19ARF in mice) tumor suppressor. ARF plays a key role in regulation of the oncogenic stress response and is frequently inhibited during GC progression. Expression of ARF, SIVA1 and ULF proteins were investigated in gastroids, H. pylori-infected mice and human gastric tissues. The role of the H. pylori type IV secretion system was assessed using various H. pylori isogenic mutants. Our studies demonstrated that H. pylori infection results in induction of ULF, decrease in SIVA1 protein levels, and subsequent ubiquitination and degradation of p14ARF tumor suppressor. Bacterial CagA protein was found to sequentially bind to SIVA1 and ULF proteins. This process is regulated by CagA protein phosphorylation at the EPIYA motifs. Downregulation of ARF protein leads to inhibition of cellular apoptosis and oncogenic stress response that may promote gastric carcinogenesis.

CRL2KLHDC3 mediates p14ARF N-terminal ubiquitylation degradation to promote non-small cell lung carcinoma progression.

Kelch superfamily involves a variety of proteins containing multiple kelch motif and is well characterized as substrate adaptors for CUL3 E3 ligases, which play critical roles in carcinogenesis. However, the role of kelch proteins in lung cancer remains largely unknown. In this study, the non-small cell lung cancer (NSCLC) patients with higher expression of a kelch protein, kelch domain containing 3 (KLHDC3), showed worse overall survival. KLHDC3 deficiency affected NSCLC cell lines proliferation in vitro and in vivo. Further study indicated that KLHDC3 mediated CUL2 E3 ligase and tumor suppressor p14ARF interaction, facilitating the N-terminal ubiquitylation and subsequent degradation of p14ARF. Interestingly, Gefitinib-resistant NSCLC cell lines displayed higher KLHDC3 protein levels. Gefitinib and Osimertinib medications were capable of upregulating KLHDC3 expression to promote p14ARF degradation in the NSCLC cell lines. KLHDC3 shortage significantly increased the sensitivity of lung cancer cells to epidermal growth factor receptor (EGFR)-targeted drugs, providing an alternative explanation for the development of Gefitinib and Osimertinib resistance in NSCLC therapy. Our works suggest that CRL2KLHDC3 could be a valuable target to regulate the abundance of p14ARF and postpone the occurrence of EGFR-targeted drugs resistance.

Aberrant hydroxymethylation in promoter CpG regions of genes related to the cell cycle and apoptosis characterizes advanced chronic myeloid leukemia disease, poor imatinib respondents and poor survival.

BACKGROUND: There is strong evidence that disease progression, drug response and overall clinical outcomes of CML disease are not only decided by BCR/ABL1 oncoprotein but depend on accumulation of additional genetic and epigenetic aberrations. DNA hydroxymethylation is implicated in the development of variety of diseases. DNA hydroxymethylation in gene promoters plays important roles in disease progression, drug response and clinical outcome of various diseases. Therefore in this study, we aimed to explore the role of aberrant hydroxymethylation in promoter regions of different tumor suppressor genes in relation to CML disease progression, response to imatinib therapy and clinical outcome. METHODS: We recruited 150 CML patients at different clinical stages of the disease. Patients were followed up for 48 months and haematological/molecular responses were analysed. Haematological response was analysed by peripheral blood smear. BCR/ABL1 specific TaqMan probe based qRT-PCR was used for assessing the molecular response of CML patients on imatinib therapy. Promoter hydroxymethylation of the genes was characterized using MS-PCR. RESULTS: We observed that promoter hydroxymethylation of DAPK1, RIZ1, P16INK4A, RASSF1A and p14ARFARF genes characterize advanced CML disease and poor imatinib respondents. Although, cytokine signalling (SOCS1) gene was hypermethylated in advanced stages of CML and accumulated in patients with poor imatinib response, but the differences were not statistically significant. Moreover, we found hypermethylation of p14ARF, RASSF1 and p16INK4A genes and cytokine signalling gene (SOCS1) significantly associated with poor overall survival of CML patients on imatinib therapy. The results of this study are in agreement of the role of aberrant DNA methylation of different tumor suppressor genes as potential biomarkers of CML disease progression, poor imatinib response and overall clinical outcome. CONCLUSION: In this study, we report that promoter hydroxymethylation of DAPK1, RIZ1, P16INK4A, RASSF1A and p14ARFARF genes is a characteristic feature of CML disease progressions, defines poor imatinib respondents and poor overall survival of CML patients to imatinib therapy.

Effect of Sodium Butyrate on p16INK4a, p14ARF, p15INK4b, Class I HDACs (HDACs 1, 2, 3) Class II HDACs (HDACs 4, 5, 6), Cell Growth Inhibition and Apoptosis Induction in Pancreatic Cancer AsPC-1 and Colon Cancer HCT-116 Cell Lines.

BACKGROUND: In higher eukaryotes, cell-cycle transitions are regulated by different cyclin-dependent kinases (Cdks) and Cdk inhibitors (CKIs). CKIs include two groups, the Ink4 (p16INK4a, p15INK4b, p18INK4c, and p19INK4d) and the Cip/Kip (p21Cip1, p27Kip1, and p57Kip2) families. The hyperactivity of histone deacetylases (HDACs) is associated with cancer induction. Histone deacetylase inhibitors (HDACIs) such as sodium butyrate (NaBT) can inhibit HDAC activity resulting in apoptosis induction. The present study was designed to investigate the effect of sodium butyrate on p16INK4a, p14ARF, p15INK4b, class I HDACs (HDACs 1, 2, 3), and class II HDACs (HDACs 4, 5, 6), cell growth inhibition, and apoptosis induction in pancreatic cancer AsPC-1 and colon cancer HCT-116 cell lines. In fact, we want to know whether sodium butyrate can reactivate Ink4 and Cip/Kip families by HDACs inhibition. MATERIALS AND METHODS: The AsPC-1 and HCT-116 cells were treated with sodium butyrate at different periods. Then, the MTT assay, cell apoptosis assay, and qRT-PCR were done to determine viability, apoptosis, and the relative expression level of the genes respectively. RESULTS: The sodium butyrate increased p16INK4a, p14ARF, and p15INK4b and decreased class I and II HDACs significantly. Besides, HCT-116 cell was more sensitive to sodium butyrate in comparison to AsPC-1 cell. CONCLUSION: The sodium butyrate can reactivate the p16INK4a, p14ARF, and p15INK4b through inhibition of HDACs in AsPC-1 and HCT-116 cell lines.

Farnesoid X receptor functions in cervical cancer via the p14ARF-mouse double minute 2-p53 pathway.

BACKGROUND: Cervical cancer is the second most common cancer among women living in developing countries. Farnesoid X receptor (FXR) is a member of the nuclear receptor family, which regulates the development and proliferation of cancer. However, the role of and molecular mechanism by which FXR acts in cervical cancer are still unknown. METHODS AND RESULTS: The relationship between FXR and the proliferation of cervical cancer cell lines was detected by MTT and colony formation assays. Immunohistochemistry was used to detect the expression of FXR in cervical cancer tissue slides. Western blotting was used to detect the expression of p14ARF, mouse double minute 2 (MDM2) and p53 when FXR was overexpressed or siRNA was applied. Western blotting was used to detect the expression of MDM2 and p53 when pifithrin-α (PFT-α) was applied. FXR activation inhibited the proliferation of cervical cancer cell lines. FXR was significantly decreased in cervical squamous cell carcinoma, which was correlated with TNM stage, but not with metastasis. Overexpression of FXR activated the p14ARF-MDM2-p53 pathway. As a p53 inhibitor, PFT-α increased MDM2 in Lenti-vector cells, but had no effect on MDM2 in Lenti-FXR cells. CONCLUSIONS: FXR inhibits cervical cancer by upregulating the p14ARF-MDM2-p53 pathway. Activation of FXR may be a potential strategy for the treatment of cervical cancer.