ALT Positivity in Human Cancers: Prevalence and Clinical Insights.

Many exciting advances in cancer-related telomere biology have been made in the past decade. Of these recent advances, great progress has also been made with respect to the Alternative Lengthening of Telomeres (ALT) pathway. Along with a better understanding of the molecular mechanism of this unique telomere maintenance pathway, many studies have also evaluated ALT activity in various cancer subtypes. We first briefly review and assess a variety of commonly used ALT biomarkers. Then, we provide both an update on ALT-positive (ALT+) tumor prevalence as well as a systematic clinical assessment of the presently studied ALT+ malignancies. Additionally, we discuss the pathogenetic alterations in ALT+ cancers, for example, the mutation status of ATRX and DAXX, and their correlations with the activation of the ALT pathway. Finally, we highlight important ALT+ clinical associations within each cancer subtype and subdivisions within, as well as their prognoses. We hope this alternative perspective will allow scientists, clinicians, and drug developers to have greater insight into the ALT cancers so that together, we may develop more efficacious treatments and improved management strategies to meet the urgent needs of cancer patients.

The Effects of Genetic and Epigenetic Alterations of BARD1 on the Development of Non-Breast and Non-Gynecological Cancers.

Breast Cancer 1 (BRCA1) gene is a well-characterized tumor suppressor gene, mutations of which are primarily found in women with breast and ovarian cancers. BRCA1-associated RING domain 1 (BARD1) gene has also been identified as an important tumor suppressor gene in breast, ovarian, and uterine cancers. Underscoring the functional significance of the BRCA1 and BARD1 interactions, prevalent mutations in the BRCA1 gene are found in its RING domain, through which it binds the RING domain of BARD1. BARD1-BRCA1 heterodimer plays a crucial role in a variety of DNA damage response (DDR) pathways, including DNA damage checkpoint and homologous recombination (HR). However, many mutations in both BARD1 and BRCA1 also exist in other domains that significantly affect their biological functions. Intriguingly, recent genome-wide studies have identified various single nucleotide polymorphisms (SNPs), genetic alterations, and epigenetic modifications in or near the BARD1 gene that manifested profound effects on tumorigenesis in a variety of non-breast and non-gynecological cancers. In this review, we will briefly discuss the molecular functions of BARD1, including its BRCA1-dependent as well as BRCA1-independent functions. We will then focus on evaluating the common BARD1 related SNPs as well as genetic and epigenetic changes that occur in the non-BRCA1-dominant cancers, including neuroblastoma, lung, and gastrointestinal cancers. Furthermore, the pro- and anti-tumorigenic functions of different SNPs and BARD1 variants will also be discussed.

Sirtuin Inhibitors Are Broadly Antiviral against Arboviruses.

Arthropod-borne viruses are diverse pathogens and are often associated with human disease. These viruses span multiple genera, including flaviviruses, alphaviruses, and bunyaviruses. In a high-throughput drug screen, we found that tenovin-1 was antiviral against the flaviviruses Zika virus and dengue virus. Tenovin-1 is a sirtuin inhibitor, and here we found that inhibition of sirtuins, but not inhibition of the related histone deacetylases, is potently antiviral against diverse arboviruses. Sirtuin inhibitors block infection of arboviruses in multiple human cell types. We found that sirtuin inhibitors arrest infection downstream of entry but that they do so at an early step, preventing the accumulation of viral RNA and protein. However, sirtuin inhibitors had no impact on the replication of flaviviral replicons, suggesting a defect in the establishment of replication. Consistent with this, we found that sirtuin inhibitors impacted double-stranded RNA (dsRNA) accumulation during flaviviral infection. Since these viruses infect vector insects, we also tested whether sirtuin inhibitors impacted infection of adult flies and found that these inhibitors blocked infection; therefore, they target highly conserved facets of replication. Taken together, these results suggest that sirtuin inhibitors represent a new class of potent host-targeting antivirals.IMPORTANCE Arthropod-borne viruses are diverse pathogens and are associated with human disease. Through high-throughput drug screening, we found that sirtuin inhibitors are potently antiviral against diverse arboviruses, including flaviviruses such as West Nile virus, bunyaviruses such as Rift Valley fever virus, and alphaviruses such as chikungunya virus. Sirtuin inhibitors block infection of these viruses in multiple human cell types. Moreover, we found that sirtuin inhibitors arrest infection downstream of entry but that they do so at an early step, preventing the accumulation of viral RNA and protein. Since these viruses infect vector insects, we also tested whether sirtuin inhibitors impacted infection of adult flies and found that these inhibitors blocked infection; therefore, they target highly conserved facets of replication. Taken together, these results suggest that sirtuin inhibitors represent a new class of potent host-targeting antivirals.

Sieving characteristics of cytokine- and peroxide-induced epithelial barrier leak: Inhibition by berberine.

AIM: To study whether the inflammatory bowel disease (IBD) colon which exhibits varying severity and cytokine levels across its mucosa create varying types of transepithelial leak. METHODS: We examined the effects of tumor necrosis factor-α (TNF-α), interferon-γ (IFN-γ), interleukin-1-ß (IL1ß) and hydrogen peroxide (H2O2) - singly and in combinations - on barrier function of CACO-2 cell layers. Our focus was on the type (not simply the magnitude) of transepithelial leak generated by these agents as measured by transepithelial electrical resistance (TER) and transepithelial flux of (14)C-D-mannitol, (3)H-Lactulose and (14)C-Polyethylene glycol as radiolabeled probe molecules. The isoquinoline alkaloid, berberine, was then examined for its ability to reduce specific types of transepithelial leak. RESULTS: Exposure to TNF-α alone (200 ng/mL; 48 h) induced a 50% decrease in TER, i.e., increased leak of Na(+) and Cl(-) - with only a marginal but statistically significant increase in transepithelial leak of (14)C-mannitol (Jm). Exposure to TNF-α + IFN-γ (200 ng/mL; 48 h) + IL1ß (50 ng/mL; 48 h) did not increase the TER change (from TNF-α alone), but there was now a 100% increase in Jm. There however was no increase in transepithelial leak of two larger probe molecules, (3)H-lactulose and (14)C-polyethylene glycol (PEG). However, exposure to TNF-α + IFN-γ + IL1ß followed by a 5 h exposure to 2 mmol/L H2O2 resulted in a 500% increase in (14)C-PEG leak as well as leak to the luminal mitogen, epidermal growth factor. CONCLUSION: This model of graded transepithelial leak is useful in evaluating therapeutic agents reducing IBD morbidity by reducing barrier leak to various luminal substances.

Remodeling of Tight Junctions and Enhancement of Barrier Integrity of the CACO-2 Intestinal Epithelial Cell Layer by Micronutrients.

The micronutrients zinc, quercetin, butyrate, indole and berberine were evaluated for their ability to induce remodeling of epithelial tight junctions (TJs) and enhance barrier integrity in the CACO-2 gastrointestinal epithelial cell culture model. All five of these chemically very diverse micronutrients increased transepithelial electrical resistance (Rt) significantly, but only berberine also improved barrier integrity to the non-electrolyte D-mannitol. Increases of Rt as much as 200% of untreated controls were observed. Each of the five micronutrients also induced unique, signature-like changes in TJ protein composition, suggesting multiple pathways (and TJ arrangements) by which TJ barrier function can be enhanced. Decreases in abundance by as much as 90% were observed for claudin-2, and increases of over 300% could be seen for claudins -5 and -7. The exact effects of the micronutrients on barrier integrity and TJ protein composition were found to be highly dependent on the degree of differentiation of the cell layer at the time it was exposed to the micronutrient. The substratum to which the epithelial layer adheres was also found to regulate the response of the cell layer to the micronutrient. The implications of these findings for therapeutically decreasing morbidity in Inflammatory Bowel Disease are discussed.