Pathogenic Role of Immune Evasion and Integration of Human Papillomavirus in Oropharyngeal Cancer

The incidence of oropharyngeal cancer (OPC) is increasing remarkably among all head and neck cancers, mainly due to its association with the human papillomavirus (HPV). Most HPVs are eliminated by the host’s immune system; however, because HPV has developed an effective immune evasion mechanism to complete its replication cycle, a small number of HPVs are not eliminated, leading to persistent infection. Moreover, during the oncogenic process, the extrachromosomal HPV genome often becomes integrated into the host genome. Integration involves the induction and high expression of E6 and E7, leading to cell cycle activation and increased genomic instability in the host. Therefore, integration is an important event in oncogenesis, although the associated mechanism remains unclear, especially in HPV-OPC. In this review, we summarize the current knowledge on HPV-mediated carcinogenesis, with special emphasis on immune evasion and integration mechanisms, which are crucial for oncogenesis.

Pathogenic tau disrupts the cellular program that maintains neuronal identity

Neurons in human Alzheimer’s disease acquire phenotypes that are also present in various cancers, including over-stabilization of the cytoskeleton, nuclear pleomorphism, decondensation of constitutive heterochromatin, and aberrant activation of the cell cycle. Unlike in cancer, in which cell cycle activation drives tumor formation, activation of the cell cycle in post-mitotic neurons is sufficient to induce neuronal death. Multiple lines of evidence suggest that abortive cell cycle activation is a consequence of pathogenic forms of tau, a protein that drives neurodegeneration in Alzheimer’s disease and related “tauopathies.” We have combined network analysis of human Alzheimer’s disease and mouse tauopathy with mechanistic studies in Drosophila to discover that pathogenic forms of tau drive abortive cell cycle activation by disrupting the cellular program that maintains neuronal identity. Mechanistically, we identify Moesin, a prognostic biomarker for cancer and mediator of the epithelial-mesenchymal transition (EMT), as a major effector of tau-induced neurotoxicity. We find that aberrant activation of Moesin in neurons acts through the actin cytoskeleton to dysregulate the cellular program that maintains neuronal identity. Our study identifies mechanistic parallels between tauopathy and cancer and sets the stage for novel therapeutic approaches.

Avena fatua caryopsis dormancy release is associated with changes in KAR1 and ABA sensitivity as well as with ABA reduction in coleorhiza and radicle

Main conclusion The dormancy release in Avena fatua caryopses was associated with a reduction in the ABA content in embryos, coleorhiza and radicle. The coleorhiza proved more sensitive to KAR1 and less sensitive to ABA than the radicle. The inability of dormant caryopses and ABA-treated non-dormant caryopses to complete germination is related to inhibition and delayed of cell-cycle activation, respectively. Abstract As freshly harvested Avena fatua caryopses are dormant at 20 °C, they cannot complete germination; the radicle is not able to emerge. Both karrikin 1 (KAR1) and dry after-ripening release dormancy, enabling the emergence of, first, the coleorhiza and later the radicle. The after-ripening removes caryopse sensitivity to KAR1 and decreases the sensitivity to abscisic acid (ABA). The coleorhiza was found to be more sensitive to KAR1, and less sensitive to ABA, than radicles. Effects of KAR1 and after-ripening were associated with a reduction of the embryo’s ABA content during caryopsis germination. KAR1 was found to decrease the ABA content in the coleorhiza and radicles. Germination of after-ripened caryopses was associated with the progress of cell-cycle activation before coleorhiza emergence. Inhibition of the germination completion due to dormancy or treating the non-dormant caryopses with ABA was associated with a total and partial inhibition of cell-cycle activation, respectively.

Abstract 400: Tip60 Depletion in Neonatal Cardiomyocytes Reduces the DNA Damage Response and Increases Cell-cycle Activation

Tip60 ( T at i nteractive p rotein, 60 kD) is a tumor suppressor encoded by the Kat5 gene that functions as a pan-acetylase. Among its targets, Atm ( a taxia- t elangiectasia m utated) undergoes auto-phosphorylation (pATM) when acetylated by Tip60 to induce the DNA damage response (DDR). Because pAtm-induced activation of the DDR is known to cause proliferative senescence in neonatal cardiomyocytes (CMs), we hypothesize that Tip60 is one of the upstream components in this pathway. Using mice containing floxed Kat5 alleles and a tamoxifen-inducible Cre-recombinase transgene driven by Myh6 (Kat5 flox/flox;Myh6-merCremer ), we assessed the effect of depleting Tip60 from neonatal CMs via a single injection of tamoxifen on postnatal day 0 (P0). Immunofluorescent microscopy revealed reduced pAtm-positive CMs at three postnatal stages (P7, P12, P39), accompanied by activation of the cell-cycle as indicated by significantly increased percentages of 5’-bromodeoxyuridine (BrdU)-, phosphohistone H3 (pH3)- and Ki67-positive CMs. In addition to cell-cycle activation, Tip60 depletion promoted nuclear division followed by cytokinesis, as indicated by increased percentage of mononuclear diploid CMs at P12. Accordingly, qPCR revealed that Tip60 depletion increased expression of mRNAs encoding the fetal markers Nppa, Nppb, Myh7 , and Acta1 at P39, which in the absence of CM hypertrophy (assessed by WGA staining) suggested maintenance of a proliferation-competent state. These effects occurred concomitant with depressed levels of mRNAs encoding cell-cycle inhibitors ( Meis1, p27 ) and a trend toward increased levels of G 2 -phase cell-cycle activators ( cyclins A2, B1 ; Cdk1 ) in Tip60-depleted hearts. These findings suggest that depletion of Tip60 at birth inhibits the DDR and delays replicative senescence in neonatal CMs.

Abstract 399: Tip60 Depletion in Adult Cardiomyocytes Promotes Proliferation and Preserves Cardiac Function After Myocardial Infarction

Cardiac disease and injury are accompanied by significant cardiomyocyte (CM) loss. CMs are essentially non-regenerable, preventing re-muscularization and resulting in permanent dysfunction during the healing process. The identification of factors from multiple layers of inhibitors that induce and maintain CM’s pronounced state of proliferative senescence provides potential therapeutic targets. Tip60 ( T at- i nteractive p rotein, 60 kD), a pan-acetylase tumor suppressor encoded by the Kat5 gene, activates multiple anti-proliferative pathways in other cell types. Tip60 is known to acetylate Atm and p53, which respectively activate the DNA damage response and apoptosis. And, Tip60 regulates intracellular levels of p21 and Tert polymerase in a fashion designed to maintain proliferative senescence. Although these functions promote CM proliferative senescence and Tip60 is strongly expressed in the myocardium, whether Tip60 regulates these activities in CMs remains unknown. This study tests the hypothesis that Tip60 inhibits CM cell-cycle activation, promotes apoptosis in the myocardium, and prevents regeneration after cardiac injury. In adult mice containing LoxP -flanked Kat5 alleles and a tamoxifen-inducible Cre-recombinase transgene driven by Myh6 (Kat5 flox/flox;Myh6-merCremer ) , Tip60 depletion three days after myocardial infarction (MI) preserved cardiac function as assessed by echocardiography at 10, 21, and 28 days post-MI. Histologic evaluation revealed that depletion of Tip60 in CMs significantly diminished scarring and increased CM cell-cycle activation, as indicated by increased numbers of Ki67-, BrdU- and pH3-positive CMs at 28 days post-MI. This was accompanied by the presence of CMs in the infarct border zone expressing smooth muscle α-actin, indicative of CM de-differentiation, and by reduced apoptosis in the remote zone as assessed by TUNEL and cleaved caspase-3 staining, suggesting reduced cardiac remodeling. These findings suggest that genetic depletion of Tip60 protects CMs from ischemia-induced cell death while promoting CM proliferation, implicating Tip60 as a novel candidate for cardiac therapeutics.

Therapeutic Effect of Rapamycin on Aortic Dissection in Mice

Aortic dissection (AD) is a serious clinical condition that is unpredictable and frequently results in fatal outcome. Although rapamycin, an inhibitor of mechanistic target of rapamycin (mTOR), has been reported to be effective in preventing aortopathies in mouse models, its mode of action has yet to be clarified. A mouse AD model that was created by the simultaneous administration of β-aminopropionitrile (BAPN) and angiotensin II (AngII) for 14 days. Rapamycin treatment was started either at day 1 or at day 7 of BAPN+AngII challenge, and continued throughout the observational period. Rapamycin was effective both in preventing AD development and in suppressing AD progression. On the other hand, gefitinib, an inhibitor of growth factor signaling, did not show such a beneficial effect, even though both rapamycin and gefitinib suppressed cell cycle activation in AD. Rapamycin suppressed cell cycle-related genes and induced muscle development-related genes in an AD-related gene expression network without a major impact on inflammation-related genes. Rapamycin augmented the activation of Akt1, Akt2, and Stat3, and maintained the contractile phenotype of aortic smooth muscle cells. These findings indicate that rapamycin was effective both in preventing the development and in suppressing the progression of AD, indicating the importance of the mTOR pathway in AD pathogenesis.

Comprehensive proteomics analyses identify PIM kinases as key regulators of IL-15 driven activation of intestinal intraepithelial lymphocytes

SUMMARYIntestinal intraepithelial lymphocytes (IEL) are an abundant population of tissue-resident T cells that protect the gut from pathogens and maintain intestinal homeostasis. The cytokine IL-15 is transpresented by epithelial cells to IEL in complex with the IL-15 receptor α chain (IL-15Rα). It plays essential roles both in maintaining IEL homeostasis, and in inducing IEL activation in response to epithelial stress. IL-15 overexpression also drives the gluten-induced enteropathy Coeliac disease, through cytotoxic activation of IEL. In order to better understand how IL-15 directly regulates both homeostatic and inflammatory functions of IEL, we set up quantitative proteomics of IL-15/Rα stimulated IEL. We reveal that high IL-15/Rα stimulation licenses cell cycle activation, upregulates the biosynthetic machinery in IEL, increases mitochondrial respiratory capacity and induces expression of cell surface immune receptors and adhesion proteins that potentially drive IEL activation. We find that high IL-15/Rα selectively upregulated the Ser/Thr kinases PIM1 and PIM2 and demonstrate that PIM1/2 are essential for IEL to proliferate, grow, and upregulate Granzyme B in response to high IL-15. Significantly, IEL from Coeliac disease patients express high levels of PIM kinases. These unexpected findings reveal PIM kinases to be key determinants of IEL responses to elevated levels of IL-15.

Redox activation of JNK2α2 mediates thyroid hormone-stimulated proliferation of neonatal murine cardiomyocytes

Mitochondria-generated reactive oxygen species (mROS) are frequently associated with DNA damage and cell cycle arrest, but physiological increases in mROS serve to regulate specific cell functions. T3 is a major regulator of mROS, including hydrogen peroxide (H2O2). Here we show that exogenous thyroid hormone (T3) administration increases cardiomyocyte numbers in neonatal murine hearts. The mechanism involves signaling by mitochondria-generated H2O2 (mH2O2) acting via the redox sensor, peroxiredoxin-1, a thiol peroxidase with high reactivity towards H2O2 that activates c-Jun N-terminal kinase-2α2 (JNK2α2). JNK2α2, a relatively rare member of the JNK family of mitogen-activated protein kinases (MAPK), phosphorylates c-Jun, a component of the activator protein 1 (AP-1) early response transcription factor, resulting in enhanced insulin-like growth factor 1 (IGF-1) expression and activation of proliferative ERK1/2 signaling. This non-canonical mechanism of MAPK activation couples T3 actions on mitochondria to cell cycle activation. Although T3 is regarded as a maturation factor for cardiomyocytes, these studies identify a novel redox pathway that is permissive for T3-mediated cardiomyocyte proliferation—this because of the expression of a pro-proliferative JNK isoform that results in growth factor elaboration and ERK1/2 cell cycle activation.

Parasympathetic Effect Induces Cell Cycle Activation in Upper Limbs of Paraplegic Patients with Spinal Cord Injury

The present study aimed to investigate gene expression changes related to cell cycle activation in patients with spinal cord injury (SCI) and to further evaluate the difference between the upper and lower limbs of SCI patients. Fibroblasts were obtained from the upper and lower limbs of SCI patients and healthy subjects. To investigate gene expression profiling in the fibroblasts from SCI patients compared to the healthy subjects, RNA-Seq transcriptome analysis was performed. To validate the parasympathetic effects on cell cycle activation, fibroblasts from upper or lower limbs of SCI patients were treated with the anticholinergic agents tiotropium or acetylcholine, and quantitative RT-PCR and Western blot were conducted. Cell proliferation was significantly increased in the upper limbs of SCI patients compared with the lower limbs of SCI patients and healthy subjects. The pathway and genes involved in cell cycle were identified by RNA-Seq transcriptome analysis. Expression of cell-cycle-related genes CCNB1, CCNB2, PLK1, BUB1, and CDC20 were significantly higher in the upper limbs of SCI patients compared with the lower limbs of SCI patients and healthy subjects. When the fibroblasts were treated with tiotropium the upper limbs and acetylcholine in the lower limbs, the expression of cell-cycle-related genes and cell proliferation were significantly modulated. This study provided the insight that cell proliferation and cell cycle activation were observed to be significantly increased in the upper limbs of SCI patients via the parasympathetic effect.