kallikreins: proteolytic enzymes found in body fluids (eg, blood, saliva, lymph, urine) that hydrolyze kininogens to kinins, thereby activating plasminolysis.
KAP1 (KRAB-associated protein): a transcriptional co-repressor that binds to KRAB domains in transcriptional repressors. See KRAB domain (krüppel-associated box).
Karnofsky performance score: a standard way of measuring the ability of patients with cancer to perform ordinary tasks. Karnofsky performance scores range from 0 to 100. A higher score means the patient is better able to carry out daily activities. The Karnofsky performance score may be used to determine a patient's prognosis, measure changes in a patient's ability to function, or decide whether a patient could be included in a clinical trial.
karyotype: an organized chromosomal profile defining chromosomal arrangement and number. In a karyotype, chromosomes are photographically arranged and displayed in pairs, ordered by size. Chromosomal size, banding pattern, and centromere position are typically used as guides to determine chromosomal abnormalities, but improved resolution may be obtained by combining traditional banding techniques with genome-wide molecular cytogenetics such as multicolor fluorescent in situ hybridization (FISH) and locus-specific FISH.
KCNS3: gene coding for the potassium voltage-gated channel, delayed-rectifier, subfamily S, member 3.
KDR/Flk1: see VEGFR (vascular endothelial growth factor receptor).
kep rate constant: reverse rate constant from tumor to the vascular space determined on dynamic contrast-enhanced magnetic resonance
keyhole limpet hemocyanin (KLH): an extracellular respiratory protein isolated from hemolymph of the marine mollusk, the giant keyhole limpet Megathura crenulata, that is native to the Pacific coast of California and Mexico. KLH is known to be highly immunogenic in humans and animals.
Khorana score: a clinical predictive model for the risk of venous thromboembolism during chemotherapy that includes site of cancer, prechemotherapy platelet count, hemoglobin, prechemotherapy leukocyte count, and body mass index.
Ki-67: a marker of proliferation. Ki-67 is a protein that is expressed in the nucleus of proliferating cells. It is absent only in resting cells. Cells in the G1, S, G2, and M phase of the cell cycle express this marker.
KIAA1209: contig sequence previously identified in a DNA microarray study of breast cancer recurrence risk.
Kip1/p27: member of the family of cell cycle regulators, typically known as cyclin-dependent kinase inhibitors (CDKI). Kip1/p27, like other CDKIs, binds cyclin-cdk complexes, leading to cell cycle arrest in the G1 phase of growth.
KIT: a member of the platelet-derived growth factor receptor family. See cKIT.
KLF6 (Kruppel-like factor 6): gene that encodes a nuclear protein
that has three zinc fingers at the end of its C-terminal domain, a serine/
threonine-rich central region, and an acidic domain lying within the
N-terminal region. The zinc fingers of this protein are responsible for the
specific DNA binding with the guanine-rich core promoter elements. The central region might be involved in activation or post-translational regulatory pathways, and the acidic N-terminal domain might play an important role in the process of transcriptional activation.
knockout animals: animals(typically mice) that have a functional gene replaced by a mutated gene, produced by gene targeting. The procedure is undertaken in embryonic stem cells, derived from a very early male mouse embryo. Sperm cells, which arise from embryonic stem cells carry the mutant gene, and propagate the mutation to every cell. In an additional round of breeding, mice are generated that are homozygous for the mutation. Knockout mouse models are widely used to study the role of specific genes in development and in human diseases, which arise as a consequence of loss of gene function.
Knudson's two-hit hypothesis: proposal in the early 1970s by Alfred Knudson that individuals develop retinoblastoma if they carry a germline mutation for one RB1 allele and later in life develop a second genetic hit affecting the other allele. In sporadic cases, the individual is conceived with two normal alleles that are both inactivated by somatic mutation events in later life. As long as only one RB1 allele functions normally, the cancer is suppressed. Knudson named cancer-preventing genes such as RB1 "anti-oncogenes," although they are now better known as "tumor suppressors."
KRAB domain (krüppel-associated box): conserved motif present in transcriptional repressors.
KRAS: see K-RAS.
K-Ras: isoform of RAS. See RAS and KRAS.
K-RAS: the gene that encodes K-RAS, a protein that is a member of the small GTPase superfamily, in which a single amino acid substitution results in an activating mutation. Alternative splicing gives rise to variants encoding two isoforms that differ in the C-terminal region.
Ktrans transfer constant: forward transfer constant from vascular
space to the tumor determined on dynamic contrast-enhanced magnetic resonance imaging.
Ku70: DNA repair enzyme that is involved in repairing DNA double-strand breaks by nonhomologous end joining with assistance from Ku80, XRCC4, and DNA ligase IV.
Kyoto Encyclopedia of Genes and Genomes (KEGG): an integrate bioinformatic database resource that is used as a reference knowledge base for biologic interpretation of large-scale data sets generated by sequencing and other high-throughput experimental technologies.