CBCT Use in Endodontic Diagnosis.

Endodontic diagnosis and treatment planning has taken a giant leap forward due to introduction of CBCT in dentistry. While conventional 2-D radiographs remain the most cost-effective and routine method to evaluate a patient's dentition, their diagnostic potential is limited. The 3-D manipulation of images that CBCT offers provides better insight into diagnostic dilemmas and complicate treatment decisions. Despite the advantages of CBCT imaging, it should be used complimentary to 2-D radiography, not as a replacement. The principle of ALARA (in which patients should be exposed to radiation "as low as reasonably achievable"), still applies to this technology. CBCT should not be used routinely in the absence of clinical signs or symptoms that necessitate a more in-depth view of a tooth and surrounding structures. In other words, if a conventional 2-D radiograph will suffice, then a CBCT pretreatment scan is not necessary. However, if more information is needed to make an accurate diagnosis, a 3-D CBCT image is justified and highly beneficial as shown through several case examples share in this article.

Targeting CDK4 and CDK6: From Discovery to Therapy.

UNLABELLED: Biochemical and genetic characterization of D-type cyclins, their cyclin D-dependent kinases (CDK4 and CDK6), and the polypeptide CDK4/6 inhibitor p16(INK4)over two decades ago revealed how mammalian cells regulate entry into the DNA synthetic (S) phase of the cell-division cycle in a retinoblastoma protein-dependent manner. These investigations provided proof-of-principle that CDK4/6 inhibitors, particularly when combined with coinhibition of allied mitogen-dependent signal transduction pathways, might prove valuable in cancer therapy. FDA approval of the CDK4/6 inhibitor palbociclib used with the aromatase inhibitor letrozole for breast cancer treatment highlights long-sought success. The newest findings herald clinical trials targeting other cancers. SIGNIFICANCE: Rapidly emerging data with selective inhibitors of CDK4/6 have validated these cell-cycle kinases as anticancer drug targets, corroborating longstanding preclinical predictions. This review addresses the discovery of these CDKs and their regulators, as well as translation of CDK4/6 biology to positive clinical outcomes and development of rational combinatorial therapies.

The senescent methylome and its relationship with cancer, ageing and germline genetic variation in humans.

BACKGROUND: Cellular senescence is a stable arrest of proliferation and is considered a key component of processes associated with carcinogenesis and other ageing-related phenotypes. Here, we perform methylome analysis of actively dividing and deeply senescent normal human epithelial cells. RESULTS: We identify senescence-associated differentially methylated positions (senDMPs) from multiple experiments using cells from one donor. We find that human senDMP epigenetic signatures are positively and significantly correlated with both cancer and ageing-associated methylation dynamics. We also identify germline genetic variants, including those associated with the p16INK4A locus, which are associated with the presence of in vivo senDMP signatures. Importantly, we also demonstrate that a single senDMP signature can be effectively reversed in a newly-developed protocol of transient senescence reversal. CONCLUSIONS: The senDMP signature has significant potential for understanding some of the key (epi)genetic etiological factors that may lead to cancer and age-related diseases in humans.

Ageing as developmental decay: insights from p16(INK4a.).

The p16(INK4a) cell cycle regulator is one of the best ageing biomarkers because it is suppressed in early embryogenesis and progressively induced during ageing. p16(INK4a) plays a crucial role in key cell fate decisions which contribute to ageing, such as cellular senescence and stem cell dynamics. Detailed examination of the pathways regulating p16(INK4a) expression has revealed an overlap with those regulating early development. We present the hypothesis that ageing might be primarily driven by gradual functional decay of developmental pathways. To support this, we summarise the role of p16(INK4a) in ageing and our current knowledge on p16(INK4a) regulation. The developmental decay hypothesis implies that the much-evidenced damage associated with all aspects of ageing might be secondary to such decay.

Senescence-inducing stress promotes proteolysis of phosphoglycerate mutase via ubiquitin ligase Mdm2.

Despite the well-documented clinical significance of the Warburg effect, it remains unclear how the aggressive glycolytic rates of tumor cells might contribute to other hallmarks of cancer, such as bypass of senescence. Here, we report that, during oncogene- or DNA damage-induced senescence, Pak1-mediated phosphorylation of phosphoglycerate mutase (PGAM) predisposes the glycolytic enzyme to ubiquitin-mediated degradation. We identify Mdm2 as a direct binding partner and ubiquitin ligase for PGAM in cultured cells and in vitro. Mutations in PGAM and Mdm2 that abrogate ubiquitination of PGAM restored the proliferative potential of primary cells under stress conditions and promoted neoplastic transformation. We propose that Mdm2, a downstream effector of p53, attenuates the Warburg effect via ubiquitination and degradation of PGAM.

Cellular senescence mediated by p16INK4A-coupled miRNA pathways.

p16 is a key regulator of cellular senescence, yet the drivers of this stable state of proliferative arrest are not well understood. Here, we identify 22 senescence-associated microRNAs (SA-miRNAs) in normal human mammary epithelial cells. We show that SA-miRNAs-26b, 181a, 210 and 424 function in concert to directly repress expression of Polycomb group (PcG) proteins CBX7, embryonic ectoderm development (EED), enhancer of zeste homologue 2 (EZH2) and suppressor of zeste 12 homologue (Suz12), thereby activating p16. We demonstrate the existence of a tight positive feedback loop in which SA-miRNAs activate and re-enforce the expression of other SA-miRNA members. In contrast, PcG members restrain senescence by epigenetically repressing the expression of these SA-miRNAs. Importantly, loss of p16 leads to repression of SA-miRNA expression, intimately coupling this effector of senescence to the SA-miRNA/PcG self-regulatory loop. Taken together, our findings illuminate an important regulatory axis that underpins the transition from proliferation to cellular senescence.

The villain team-up or how Trichomonas vaginalis and bacterial vaginosis alter innate immunity in concert.

OBJECTIVES: Complex interactions of vaginal microorganisms with the genital tract epithelium shape mucosal innate immunity, which holds the key to sexual and reproductive health. Bacterial vaginosis (BV), a microbiome-disturbance syndrome prevalent in reproductive-age women, occurs commonly in concert with trichomoniasis, and both are associated with increased risk of adverse reproductive outcomes and viral infections, largely attributable to inflammation. To investigate the causative relationships among inflammation, BV and trichomoniasis, we established a model of human cervicovaginal epithelial cells colonised by vaginal Lactobacillus isolates, dominant in healthy women, and common BV species (Atopobium vaginae, Gardnerella vaginalis and Prevotella bivia). METHODS: Colonised epithelia were infected with Trichomonas vaginalis (TV) or exposed to purified TV virulence factors (membrane lipophosphoglycan (LPG), its ceramide-phosphoinositol-glycan core (CPI-GC) or the endosymbiont Trichomonas vaginalis virus (TVV)), followed by assessment of bacterial colony-forming units, the mucosal anti-inflammatory microbicide secretory leucocyte protease inhibitor (SLPI), and chemokines that drive pro-inflammatory, antigen-presenting and T cells. RESULTS: TV reduced colonisation by Lactobacillus but not by BV species, which were found inside epithelial cells. TV increased interleukin (IL)-8 and suppressed SLPI, likely via LPG/CPI-GC, and upregulated IL-8 and RANTES, likely via TVV as suggested by use of purified pathogenic determinants. BV species A vaginae and G vaginalis induced IL-8 and RANTES, and also amplified the pro-inflammatory responses to both LPG/CPI-GC and TVV, whereas P bivia suppressed the TV/TVV-induced chemokines. CONCLUSIONS: These molecular host-parasite-endosymbiont-bacteria interactions explain epidemiological associations and suggest a revised paradigm for restoring vaginal immunity and preventing BV/TV-attributable inflammatory sequelae in women.

Monitoring tumorigenesis and senescence in vivo with a p16(INK4a)-luciferase model.

Monitoring cancer and aging in vivo remains experimentally challenging. Here, we describe a luciferase knockin mouse (p16(LUC)), which faithfully reports expression of p16(INK4a), a tumor suppressor and aging biomarker. Lifelong assessment of luminescence in p16(+/LUC) mice revealed an exponential increase with aging, which was highly variable in a cohort of contemporaneously housed, syngeneic mice. Expression of p16(INK4a) with aging did not predict cancer development, suggesting that the accumulation of senescent cells is not a principal determinant of cancer-related death. In 14 of 14 tested tumor models, expression of p16(LUC) was focally activated by early neoplastic events, enabling visualization of tumors with sensitivity exceeding other imaging modalities. Activation of p16(INK4a) was noted in the emerging neoplasm and surrounding stromal cells. This work suggests that p16(INK4a) activation is a characteristic of all emerging cancers, making the p16(LUC) allele a sensitive, unbiased reporter of neoplastic transformation.

Endobiont viruses sensed by the human host - beyond conventional antiparasitic therapy.

Wide-spread protozoan parasites carry endosymbiotic dsRNA viruses with uncharted implications to the human host. Among them, Trichomonas vaginalis, a parasite adapted to the human genitourinary tract, infects globally ∼250 million each year rendering them more susceptible to devastating pregnancy complications (especially preterm birth), HIV infection and HPV-related cancer. While first-line antibiotic treatment (metronidazole) commonly kills the protozoan pathogen, it fails to improve reproductive outcome. We show that endosymbiotic Trichomonasvirus, highly prevalent in T. vaginalis clinical isolates, is sensed by the human epithelial cells via Toll-like receptor 3, triggering Interferon Regulating Factor -3, interferon type I and proinflammatory cascades previously implicated in preterm birth and HIV-1 susceptibility. Metronidazole treatment amplified these proinflammatory responses. Thus, a new paradigm targeting the protozoan viruses along with the protozoan host may prevent trichomoniasis-attributable inflammatory sequelae.

A whole genome screen for HIV restriction factors.

BACKGROUND: Upon cellular entry retroviruses must avoid innate restriction factors produced by the host cell. For human immunodeficiency virus (HIV) human restriction factors, APOBEC3 (apolipoprotein-B-mRNA-editing-enzyme), p21 and tetherin are well characterised. RESULTS: To identify intrinsic resistance factors to HIV-1 replication we screened 19,121 human genes and identified 114 factors with significant inhibition of infection. Those with a known function are involved in a broad spectrum of cellular processes including receptor signalling, vesicle trafficking, transcription, apoptosis, cross-nuclear membrane transport, meiosis, DNA damage repair, ubiquitination and RNA processing. We focused on the PAF1 complex which has been previously implicated in gene transcription, cell cycle control and mRNA surveillance. Knockdown of all members of the PAF1 family of proteins enhanced HIV-1 reverse transcription and integration of provirus. Over-expression of PAF1 in host cells renders them refractory to HIV-1. Simian Immunodeficiency Viruses and HIV-2 are also restricted in PAF1 expressing cells. PAF1 is expressed in primary monocytes, macrophages and T-lymphocytes and we demonstrate strong activity in MonoMac1, a monocyte cell line. CONCLUSIONS: We propose that the PAF1c establishes an anti-viral state to prevent infection by incoming retroviruses. This previously unrecognised mechanism of restriction could have implications for invasion of cells by any pathogen.

Clinical isolates of Trichomonas vaginalis concurrently infected by strains of up to four Trichomonasvirus species (Family Totiviridae).

Trichomonas vaginalis, which causes the most common nonviral sexually transmitted disease worldwide, is itself commonly infected by nonsegmented double-stranded RNA (dsRNA) viruses from the genus Trichomonasvirus, family Totiviridae. To date, cDNA sequences of one or more strains of each of three trichomonasvirus species have been reported, and gel electrophoresis showing several different dsRNA molecules obtained from a few T. vaginalis isolates has suggested that more than one virus strain might concurrently infect the same parasite cell. Here, we report the complete cDNA sequences of 3 trichomonasvirus strains, one from each of the 3 known species, infecting a single, agar-cloned clinical isolate of T. vaginalis, confirming the natural capacity for concurrent (in this case, triple) infections in this system. We furthermore report the complete cDNA sequences of 11 additional trichomonasvirus strains, from 4 other clinical isolates of T. vaginalis. These additional strains represent the three known trichomonasvirus species, as well as a newly identified fourth species. Moreover, 2 of these other T. vaginalis isolates are concurrently infected by strains of all 4 trichomonasvirus species (i.e., quadruple infections). In sum, the full-length cDNA sequences of these 14 new trichomonasviruses greatly expand the existing data set for members of this genus and substantiate our understanding of their genome organizations, protein-coding and replication signals, diversity, and phylogenetics. The complexity of this virus-host system is greater than has been previously well recognized and suggests a number of important questions relating to the pathogenesis and disease outcomes of T. vaginalis infections of the human genital mucosa.