Background
Delayed gastric emptying (DGE) is a frequent complication after pancreaticoduodenectomy (PD). The diagnosis of DGE is based on International Study Group for Pancreatic Surgery (ISGPS) ...clinical criteria and objective assessments of DGE are infrequently used. The present literature review aimed to identify objective measures of DGE following PD and determine whether these measures correlate with the clinical definition of DGE.
Methods
A systematic search was performed using the MEDLINE Ovid, EMBASE, Google Scholar and CINAHL databases for studies including pancreatic surgery, delayed gastric emptying and gastric motility until June 2022. The primary outcome was modalities undertaken for the objective measurement of DGE following PD and correlation between objective measurements and clinical diagnosis of DGE. Relevant risk of bias analysis was performed.
Results
The search revealed 4881 records, of which 46 studies were included in the final analysis. There were four objective modalities of DGE assessment including gastric scintigraphy (
n
= 28), acetaminophen/paracetamol absorption test (
n
= 10), fluoroscopy (
n
= 6) and the
13
C-acetate breath test (
n
= 3). Protocols were inconsistent, and reported correlations between clinical and objective measures of DGE were variable; however, amongst these measures, at least one study directly or indirectly inferred a correlation, with the greatest evidence accumulated for gastric scintigraphy.
Conclusion
Several objective modalities to assess DGE following PD have been identified and evaluated, however are infrequently used. Substantial variability exists in the literature regarding indications and interpretation of these tests, and there is a need for a real-time objective modality which correlates with ISGPS DGE definition after PD.
Universal health coverage (UHC) is broadly defined as all individuals having access to needed health services without financial hardship.1 Over the last decade, the push for UHC has gained ...considerable momentum, having become a priority area in reaching the sustainable development goals (SDGs) by 2030. Initial evaluations indicate progress in important areas such as coverage of human immunodeficiency virus, tuberculosis and malaria services.1 Oral health, by contrast, has been largely absent from the UHC discussion, and limited progress has been made in addressing oral diseases around the world over the last twenty years. In many countries, oral health is deemed low priority and attributed to individual, rather than social responsibility. However, a few countries working towards UHC include dental services for some or all population groups, suggesting that the exclusion of oral health from UHC is no conceptual inevitability. Failing to broaden UHC to encompass oral health risks undermining systemic health outcomes and exacerbating health disparities. As countries plan and align strategies towards UHC, reviewing whether excluding oral health is compatible with the overall goals of UHC is necessary.To monitor progress towards UHC, the World Health Organization (WHO) and the World Bank use 16 tracer indicators in four categories: (i) reproductive, maternal, and child health; (ii) infectious diseases; (iii) noncommunicable diseases; and (iv) service capacity and access.1 Though poor oral health is recognized as a noncommunicable disease, it was excluded from being an indicator for the health-related SDG, which aims to broadly improve health outcomes.
The bacterial clustered regularly interspaced short palindromic repeats (CRISPR)–Cas9 system for genome editing has greatly expanded the toolbox for mammalian genetics, enabling the rapid generation ...of isogenic cell lines and mice with modified alleles. Here, we describe a pooled, loss-of-function genetic screening approach suitable for both positive and negative selection that uses a genome-scale lentiviral single-guide RNA (sgRNA) library. sgRNA expression cassettes were stably integrated into the genome, which enabled a complex mutant pool to be tracked by massively parallel sequencing. We used a library containing 73,000 sgRNAs to generate knockout collections and performed screens in two human cell lines. A screen for resistance to the nucleotide analog 6-thioguanine identified all expected members of the DNA mismatch repair pathway, whereas another for the DNA topoisomerase II (TOP2A) poison etoposide identified TOP2A, as expected, and also cyclin-dependent kinase 6, CDK6. A negative selection screen for essential genes identified numerous gene sets corresponding to fundamental processes. Last, we show that sgRNA efficiency is associated with specific sequence motifs, enabling the prediction of more effective sgRNAs. Collectively, these results establish Cas9/sgRNA screens as a powerful tool for systematic genetic analysis in mammalian cells.
Mitochondria house metabolic pathways that impact most aspects of cellular physiology. While metabolite profiling by mass spectrometry is widely applied at the whole-cell level, it is not routinely ...possible to measure the concentrations of small molecules in mammalian organelles. We describe a method for the rapid and specific isolation of mitochondria and use it in tandem with a database of predicted mitochondrial metabolites (“MITObolome”) to measure the matrix concentrations of more than 100 metabolites across various states of respiratory chain (RC) function. Disruption of the RC reveals extensive compartmentalization of mitochondrial metabolism and signatures unique to the inhibition of each RC complex. Pyruvate enables the proliferation of RC-deficient cells but has surprisingly limited effects on matrix contents. Interestingly, despite failing to restore matrix NADH/NAD balance, pyruvate does increase aspartate, likely through the exchange of matrix glutamate for cytosolic aspartate. We demonstrate the value of mitochondrial metabolite profiling and describe a strategy applicable to other organelles.
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•A workflow for absolute quantification of mitochondrial matrix metabolites•Rapid and specific isolation of mitochondria from cells for metabolite profiling•Profiling guided by MITObolome, a set of all predicted mitochondrial metabolites•Dynamics of mitochondrial metabolism revealed by quantification of >100 metabolites
Metabolite profiling of intact mammalian mitochondria captures dynamics of mitochondrial metabolism not revealed by whole-cell analysis.
Large-scale genetic analysis of lethal phenotypes has elucidated the molecular underpinnings of many biological processes. Using the bacterial clustered regularly interspaced short palindromic ...repeats (CRISPR) system, we constructed a genome-wide single-guide RNA library to screen for genes required for proliferation and survival in a human cancer cell line. Our screen revealed the set of cell-essential genes, which was validated with an orthogonal gene-trap–based screen and comparison with yeast gene knockouts. This set is enriched for genes that encode components of fundamental pathways, are expressed at high levels, and contain few inactivating polymorphisms in the human population. We also uncovered a large group of uncharacterized genes involved in RNA processing, a number of whose products localize to the nucleolus. Last, screens in additional cell lines showed a high degree of overlap in gene essentiality but also revealed differences specific to each cell line and cancer type that reflect the developmental origin, oncogenic drivers, paralogous gene expression pattern, and chromosomal structure of each line. These results demonstrate the power of CRISPR-based screens and suggest a general strategy for identifying liabilities in cancer cells.
The mitochondrial electron transport chain (ETC) enables many metabolic processes, but why its inhibition suppresses cell proliferation is unclear. It is also not well understood why pyruvate ...supplementation allows cells lacking ETC function to proliferate. We used a CRISPR-based genetic screen to identify genes whose loss sensitizes human cells to phenformin, a complex I inhibitor. The screen yielded GOT1, the cytosolic aspartate aminotransferase, loss of which kills cells upon ETC inhibition. GOT1 normally consumes aspartate to transfer electrons into mitochondria, but, upon ETC inhibition, it reverses to generate aspartate in the cytosol, which partially compensates for the loss of mitochondrial aspartate synthesis. Pyruvate stimulates aspartate synthesis in a GOT1-dependent fashion, which is required for pyruvate to rescue proliferation of cells with ETC dysfunction. Aspartate supplementation or overexpression of an aspartate transporter allows cells without ETC activity to proliferate. Thus, enabling aspartate synthesis is an essential role of the ETC in cell proliferation.
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•A CRISPR-Cas9 genetic screen reveals that GOT1 loss kills cells upon ETC inhibition•In cells with ETC inhibition, GOT1 reverses flux to generate aspartate in the cytosol•Aspartate is limiting for proliferation in cells with ETC inhibition•Pyruvate reverses the effects of ETC inhibition by inducing aspartate synthesis
Aspartate is a limiting metabolite for proliferation in cells with mitochondrial electron transport chain defects.
The CDK4/6 inhibitor, palbociclib (PAL), significantly improves progression-free survival in HR+/HER2− breast cancer when combined with anti-hormonals. We sought to discover PAL resistance mechanisms ...in preclinical models and through analysis of clinical transcriptome specimens, which coalesced on induction of MYC oncogene and Cyclin E/CDK2 activity. We propose that targeting the G1 kinases CDK2, CDK4, and CDK6 with a small-molecule overcomes resistance to CDK4/6 inhibition. We describe the pharmacodynamics and efficacy of PF-06873600 (PF3600), a pyridopyrimidine with potent inhibition of CDK2/4/6 activity and efficacy in multiple in vivo tumor models. Together with the clinical analysis, MYC activity predicts (PF3600) efficacy across multiple cell lineages. Finally, we find that CDK2/4/6 inhibition does not compromise tumor-specific immune checkpoint blockade responses in syngeneic models. We anticipate that (PF3600), currently in phase 1 clinical trials, offers a therapeutic option to cancer patients in whom CDK4/6 inhibition is insufficient to alter disease progression.
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•Clinical CDK4/6 inhibitor resistance converges on MYC and CDK2 activation•CDK2/4/6 inhibitor, PF-06873600, exhibits robust preclinical anti-tumor activity•PF-06873600 preferentially inhibits MYC activated preclinical models•Anti-tumor immunity is retained and possibly augmented by PF-06873600
While CDK4/6 inhibitors are therapeutically beneficial in HR+ breast cancer, many patients experience therapy resistance. Freeman-Cook et al. find that in preclinical and clinical contexts, activation of the oncogene MYC can elicit CDK4/6 inhibitor resistance that converges on CDK2 activation. To mitigate these mechanisms CDK2/4/6 inhibitor PF-06873600 is developed, which has robust pharmacodynamic and tumor growth inhibitory activity in multiple models of cancer, preferentially those with elevated MYC activity.
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