UBC (ubiquitin C): protein involved in the process of protein turnover in eukaryotic cells. Its essential function qualifies UBC as a housekeeping gene.
ubiquitin: a small protein that attaches to a protein. See proteasome.
ubiquitination: a process by which a small protein (ubiquitin) attaches to a protein.
ubiquitylation: the addition of ubiquitin to proteins, targeting them to degradation by the proteasomal pathway. See ubiquitin.
UGT1A1 (UDP-glucuronosyltransferase 1A1): an isoform of uridine-diphosphoglucuronate glucuronosyltransferases. UGT1A1 is responsible for the glucuronidation of bilirubin, xenobiotic compounds, and endogenous steroids. Variants of UGT1A1 are known to affect the glucuronidation of SN-38, the active metabolite of irinotecan.
UGT1A1H28: an allele of UGT1A1 with seven TA repeats in the promoter region of the UGT1A1 gene. The variant allele is associated with a reduced expression of UGT1A1, leading to reduced glucuronidation of metabolites such as SN-38, which accumulates and leads to toxicities such as diarrhea and leucopenia during irinotecan therapy.
unclassified variant: alteration of the normal gene sequence of
which the significance on the phenotype is unclear.
unplanned outcomes: in a clinical trial, endpoints or statistical analyses that were performed and reported post hoc and were not identified and specified in the protocol at study initiation. These outcomes must be identified as unplanned in all published reports.
unsupervised hierarchical clustering: analysis performed without using the knowledge of clinical end points of the study. Methods such as cluster analysis, which identify partitions in data sets by comparing pair-wise similarity measures of gene expression, are unsupervised methods. These methods are generally poorly suited for identifying prognostic variables because they do not necessarily create categories reflecting distinct biologic phenotypes, and in most cases, the categories do not allow a straightforward interpretation.
unsupervised methods: analysis done without using the knowledge of clinical end points of the study. Methods such as cluster analysis, which identify partitions in data sets by comparing pair-wise similarity measures of gene expression, are unsupervised methods. These methods are generally poorly suited for identifying prognostic variables because they do not necessarily create categories reflecting distinct biological phenotypes, and in most cases, the categories do not allow a straightforward interpretation.
uPA (urokinase-type plasminogen activator): a molecule with chemotactic activity when bound to its receptor, uPAR. Soluble uPA (or uPA bound to uPAR) also generates plasmin, which degrades extracellular matrix components leading to invasion and metastasis. The chemotactic activity is responsible for cell recruitment, which occurs in inflammation, neoangiogenesis, and cancer invasiveness.
uPAR: is a GPI (glycophosphatidylinositol) -anchored protein that is expressed by various cells, including neutrophils, T lymphocytes, monocytes, macrophages and fibroblasts. In the absence of an intracytoplasmic region, the GPI acts as a tether, with the transmembrane adaptor(s) mediating the activation of intracellular signal transduction molecules. Also called CD87.
updated covariate: also known as time-dependent covariate in
contrast to a fixed covariate, which is measured at a single point in time.
uridine-cytidine kinase: an enzyme involved in the nucleotide metabolism pathway. Uridine-cytidine kinase catalyzes the formation of uridine monophosphate from uridine and GTP.
utility: a measure of the preference for, or desirability of, a specific level of health status or specific health outcome.