In response to a meal, Glucose-dependent Insulinotropic Polypeptide (GIP) and Glucagon-like Peptide-1 (GLP-1) are released from gut endocrine cells into the circulation and interact with their ...cognate G-protein coupled receptors (GPCRs). Receptor activation results in tissue-selective pleiotropic responses that include augmentation of glucose-induced insulin secretion from pancreatic beta cells. N-glycosylation and receptor oligomerization are co-translational processes that are thought to regulate the exit of functional GPCRs from the ER and their maintenance at the plasma membrane. Despite the importance of these regulatory processes, their impact on functional expression of GIP and GLP-1 receptors has not been well studied. Like many family B GPCRs, both the GIP and GLP-1 receptors possess a large extracellular N-terminus with multiple consensus sites for Asn-linked (N)-glycosylation. Here, we show that each of these Asn residues is glycosylated when either human receptor is expressed in Chinese hamster ovary cells. N-glycosylation enhances cell surface expression and function in parallel but exerts stronger control over the GIP receptor than the GLP-1 receptor. N-glycosylation mainly lengthens receptor half-life by reducing degradation in the endoplasmic reticulum. N-glycosylation is also required for expression of the GIP receptor at the plasma membrane and efficient GIP potentiation of glucose-induced insulin secretion from the INS-1 pancreatic beta cell line. Functional expression of a GIP receptor mutant lacking N-glycosylation is rescued by co-expressed wild type GLP1 receptor, which, together with data obtained using Bioluminescence Resonance Energy Transfer, suggests formation of a GIP-GLP1 receptor heteromer.
Krüppel-associated box-domain zinc finger protein (KRAB-ZFP) transcriptional repressors recruit TRIM28/KAP1 to heterochromatinize the mammalian genome while also guarding the host by silencing ...invading foreign genomes. However, how a KRAB-ZFP recognizes target sequences in the natural context of its own or foreign genomes is unclear. Our studies on B-lymphocytes permanently harboring the cancer-causing Epstein-Barr virus (EBV) have shown that SZF1, a KRAB-ZFP, binds to several lytic/replicative phase genes to silence them, thereby promoting the latent/quiescent phase of the virus. As a result, unless SZF1 and its binding partners are displaced from target regions on the viral genome, EBV remains dormant, i.e. refractory to lytic phase-inducing triggers. As SZF1 also heterochromatinizes the cellular genome, we performed in situ footprint mapping on both viral and host genomes in physically separated B-lymphocytes bearing latent or replicative/active EBV genomes. By analyzing footprints, we learned that SZF1 recognizes the host genome through a repeat sequence-bearing motif near centromeres. Remarkably, SZF1 does not use this motif to recognize the EBV genome. Instead, it uses distinct binding sites that lack obvious similarities to each other or the above motif, to silence the viral genome. Virus mutagenesis studies show that these distinct binding sites are not only key to maintaining the established latent phase but also silencing the lytic phase in newly-infected cells, thus enabling the virus to establish latency and transform cells. Notably, these binding sites on the viral genome, when also present on the human genome, are not used by SZF1 to silence host genes during latency. This differential approach towards target site recognition may reflect a strategy by which the host silences and regulates genomes of persistent invaders without jeopardizing its own homeostasis.
Epstein-Barr virus (EBV) is an oncogenic herpesvirus and WHO class 1 carcinogen that resides in B lymphocytes of nearly all humans. While silent in most, EBV can cause endemic Burkitt lymphoma in ...children and post-transplant lymphoproliferative disorders/lymphomas in immunocompromised hosts. The pathogenesis of such lymphomas is multifactorial but to a large extent depends on EBV's ability to aggressively drive cellular DNA replication and B cell proliferation despite cell-intrinsic barriers to replication. One such barrier is oncogenic replication stress which hinders the progression of DNA replication forks. To understand how EBV successfully overcomes replication stress, we examined cellular replication forks in EBV-transformed B cells using iPOND (isolation of Proteins on Nascent DNA)-mass spectrometry and identified several cellular proteins that had not previously been linked to DNA replication. Of eight candidate replisome-associated proteins that we validated at forks in EBV-transformed cells and Burkitt lymphoma-derived cells, three zinc finger proteins (ZFPs) were upregulated early in B cells newly-infected with EBV in culture as well as expressed at high levels in EBV-infected B blasts in the blood of immunocompromised transplant recipients. Expressed highly in S- and G2-phase cells, knockdown of each ZFP resulted in stalling of proliferating cells in the S-phase, cleavage of caspase 3, and cell death. These proteins, newly-identified at replication forks of EBV-transformed and Burkitt lymphoma cells therefore contribute to cell survival and cell cycle progression, and represent novel targets for intervention of EBV-lymphomas while simultaneously offering a window into how the replication machinery may be similarly modified in other cancers.
Context
Deforestation and landscape fragmentation have been identified as processes enabling direct transmission of zoonotic infections. Certain human behaviors provide opportunities for direct ...contact between humans and wild nonhuman primates (NHPs), but are often missing from studies linking landscape level factors and observed infectious diseases.
Objectives
Our objective is to better understand landscape and livelihood factors influencing human-NHP contact in rural communities whose landscapes undergo deforestation. We investigate core loss and edge density within a buffered area around survey respondent households to identify which landscape changes and behaviors increase the risk of human-NHP contact.
Methods
Behavioral survey data were collected from small-scale agriculturists living near forest fragments around Kibale National Park in western Uganda. We combined spatially explicit behavioral data with high-resolution satellite imagery. Using land cover classification and change detection, we investigated the relationships between forest loss and fragmentation, behavioral data, and human-NHP contact using logistic regression.
Results
Between 2011 and 2015, there were differences in the landscape metrics around the households of individuals who had experienced human-NHP contact compared to those who had not had contact. Increased edge density around households, collection of small trees for construction, and foraging and hunting for food in forested habitat significantly increase the likelihood of human-NHP contact.
Conclusion
This study provides empirical evidence that forest landscape fragmentation and certain smallholders’ behaviors in forest patches jointly increase the likelihood of human-NHP contact events. Combining spatially explicit data on land use and human behaviors is crucial for understanding the social and ecological drivers of human-NHP contact.
Abstract
We explore observational and theoretical constraints on how galaxies might transition between the ‘star-forming main sequence’ (SFMS) and varying ‘degrees of quiescence’ out to z = 3. Our ...analysis is focused on galaxies with stellar mass M* > 1010 M⊙, and is enabled by GAMA and CANDELS observations, a semi-analytic model (SAM) of galaxy formation, and a cosmological hydrodynamical ‘zoom in’ simulation with momentum-driven AGN feedback. In both the observations and the SAM, transition galaxies tend to have intermediate Sérsic indices, half-light radii, and surface stellar mass densities compared to star-forming and quiescent galaxies out to z = 3. We place an observational upper limit on the average population transition time-scale as a function of redshift, finding that the average high-redshift galaxy is on a ‘fast track’ for quenching whereas the average low-redshift galaxy is on a ‘slow track’ for quenching. We qualitatively identify four physical origin scenarios for transition galaxies in the SAM: oscillations on the SFMS, slow quenching, fast quenching, and rejuvenation. Quenching time-scales in both the SAM and the hydrodynamical simulation are not fast enough to reproduce the quiescent population that we observe at z ∼ 3. In the SAM, we do not find a clear-cut morphological dependence of quenching time-scales, but we do predict that the mean stellar ages, cold gas fractions, SMBH (supermassive black hole) masses and halo masses of transition galaxies tend to be intermediate relative to those of star-forming and quiescent galaxies at z < 3.
Active surveillance (AS) has gained acceptance as a management strategy for localized renal masses.
To review our large single-center experience with AS.
From 2000 to 2016, we identified 457 patients ...with 544 lesions managed with AS from our prospectively maintained kidney cancer database. A subset analysis was performed for patients with ≥5-yr follow-up without delayed intervention (DI).
Linear growth rates (LGRs) were estimated using linear regression for the initial LGR (iLGR) AS interval and the entire AS period. Overall survival (OS) and cumulative incidence of DI were estimated with Kaplan-Meier methods utilizing iLGR groups, adjusting for covariates. DI was evaluated for association with OS in Cox models.
Median follow-up was 67 mo (interquartile range IQR 41–94 mo) for surviving patients. Cumulative incidence of DI (n=153) after 1, 2, 3, 4, and 5 yr was 9%, 22%, 29%, 35%, and 42%, respectively. Median initial maximum tumor dimension was 2.1cm (IQR 1.5–3.1cm). Median iLGR and overall LGR were 1.9 (IQR 0–7) and 1.9 (IQR 0.3–4.2) mm/yr, respectively. Compared with the no growth group, low iLGR (hazard ratio HR 1.25, 95% cumulative incidence CI 0.82–1.91), moderate iLGR (HR 2.1, 95% CI 1.31–3.36), and high iLGR (HR 1.87, 95% CI 1.23–2.84) were associated with DI (p=0.003). The iLGR was not associated with OS (p=0.8). DI was not associated with OS (HR 1.34, 95% CI 0.79–2.29, p=0.3). Five-year cancer-specific mortality (CSM) was 1.2% (95% CI 0.4–2.8%). Of 99 patients on AS without DI for >5 yr, one patient metastasized.
At >5 yr, AS±DI is a successful strategy in carefully managed patients. DI often occurs in the first 2–3 yr, becoming less likely over time. Rare metastasis and low CSM rates should reassure physicians that AS is safe in the intermediate to long term.
In this report, we looked at the outcomes of patients with kidney masses who elected to enroll in active surveillance rather than immediate surgery. We found that patients who need surgery are often identified early and those who remain on active surveillance become less likely to need surgery over time. We concluded that active surveillance with or without delayed surgery is a safe practice and that, when properly managed and followed, patients are unlikely to metastasize or die from kidney cancer.
Active surveillance (AS)±delayed intervention (DI) for localized renal masses is safe at >5 yr of follow-up. Many patients can safely avoid DI, and its likelihood decreases over time. Disease progression is unlikely when remaining on AS for >5 yr.
Epstein-Barr virus (EBV) causes lymphomas and epithelial cell cancers. Though generally silent in B lymphocytes, this widely prevalent virus can cause endemic Burkitt lymphoma and post-transplant ...lymphoproliferative disorders/lymphomas in immunocompromised hosts. By learning how EBV breaches barriers to cell proliferation, we hope to undermine those strategies to treat EBV lymphomas and potentially other cancers. We had previously found that EBV, through activation of cellular STAT3 prevents phosphorylation of Chk1, and thereby, suppresses activation of the intra-S phase cell-cycle checkpoint, a potent barrier to oncogene-driven proliferation. This observation prompted us to examine the consequences on DNA repair since homologous recombination repair, the most error-free form, requires phosphoChk1. We now report that the defect in Chk1 phosphorylation also curtails RAD51 nucleation, and thereby, homologous recombination repair of DNA double strand breaks. The resulting reliance on error-prone microhomology-mediated end-joining (MMEJ) repair makes EBV-transformed cells susceptible to PARP inhibition and simultaneous accrual of genome-wide deletions and insertions resulting from synthesis-dependent MMEJ. Analysis of transcriptomic and drug susceptibility data from hundreds of cancer lines reveals a STAT3-dependent gene-set predictive of susceptibility of cancers to synthetic lethal PARP inhibition. These findings i) demonstrate how the tumor virus EBV re-shapes cellular DNA repair, ii) provide the first genome-wide evidence for insertions resulting from MMEJ in human cells, and iii) expand the range of cancers (EBV-related and -unrelated) that are likely to respond to synthetic lethal inhibitors given the high prevalence of cancers with constitutively active STAT3.
Background
The management of metastatic renal cell carcinoma (mRCC) has evolved rapidly, and results from the Cancer du Rein Metastatique Nephrectomie et Antiangiogéniques (CARMENA) trial bring into ...question the utility of cytoreductive nephrectomy (CN). The objective of this study was to examine overall survival (OS) and identify risk factors associated with patients less likely to benefit from CN in the targeted therapy era.
Methods
Patients with mRCC undergoing CN from 2005 to 2017 were identified. Kaplan‐Meier methods and Cox proportional hazards regression analyses were used to assess OS and risk‐stratify patients, respectively, on the basis of preoperative clinical and laboratory data.
Results
Six hundred eight patients were eligible with a median follow‐up of 29.4 months. Ninety‐five percent of the patients had an Eastern Cooperative Oncology Group performance status less than or equal to 1, and 70% had a single site of metastatic disease. In a multivariable analysis, risk factors significantly associated with decreased OS included systemic symptoms at diagnosis, retroperitoneal and supradiaphragmatic lymphadenopathy, bone metastasis, clinical T4 disease, a hemoglobin level less than the lower limit of normal (LLN), a serum albumin level less than the LLN, a serum lactate dehydrogenase level greater than the upper limit of normal, and a neutrophil/lymphocyte ratio greater than or equal to 4. Patients were stratified into 3 risk groups: low (fewer than 2 risk factors), intermediate (2‐3 risk factors), and high (more than 3 risk factors). These groups had median OS of 58.9 months (95% confidence interval CI, 44.3‐66.6 months), 30.6 months (95% CI, 27.0‐35.0 months), and 19.2 months (95% CI, 13.9‐22.6 months), respectively (P < .0001). The median time to postoperative systemic therapy was 45 days (interquartile range, 30‐90 days).
Conclusions
Patients with more than 3 risk factors did not seem to benefit from CN. Importantly, OS in this group was equivalent to, if not higher than, OS for patients in the CN plus sunitinib arm of CARMENA, and this raises the possibility that a well‐selected population might benefit from CN.
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