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Oncology Glossary

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T helper 1: CD4 T cells that secrete cytokines such as interferon-γ, tumor necrosis factor α, and interleukin-2. These cells are immune system activators and support the growth and function of cytotoxic CD8 T cells.

T helper 2: CD4 T cells that secrete cytokines such as interleukin (IL) -4, IL-10, and IL-6. These cells support the proliferation of B cells and dampen the function of cytotoxic CD8 T cells.

T1 N0 M0: disease staging in which T1 refers to a tumor 2 cm or less in greatest dimension, N0 indicates no regional lymph node metastasis, and M0 means no distant metastasis.

T2 N0 M0: disease staging in which T2 refers to a tumor more than 2 cm but not more than 4 cm in greatest dimension, N0 indicates no regional lymph node metastasis, and M0 means no distant metastasis.

TAp73: TP73 isoforms, which contain the DNA-binding, the oligomerization, and transactivation domains. TAp73 proteins largely mimic p53 suppressor functions in experimental systems and are capable of inducing cell cycle arrest and cell death in response to DNA damage.

TAp73: transactivation-deficient TP73 variant (including ∇Ex2p73, ∇Ex2/3p73, ∇Np73, and ∇N'p73, so-called ∇TAp73), which are generated through alternative processing at the NH2-terminal region or differential promoter usage. ∇TAp73 proteins fail to induce apoptosis and cell cycle arrest by acting as direct competitors for the DNA binding sites and/or by heteroduplex formation with p53 and the transactivation-competent TAp73 variants, inhibiting their tumor suppressor properties.

target intensity: a predefined average intensity signal that is used to scale and normalize the actual signals of all gene sequencing chips in an assay.

targeted sequencing: sequencing of the coding regions or other selected regions from a relatively small subset of genes.

targeted therapeutics: therapeutic agents that are specifically modeled to inhibit very specific molecules in signal transduction pathways implicated in the disease.

taxanes: a class of chemotherapy that leads to the disruption of microtubule function and thus stops cell division. Paclitaxel and docetaxel are examples of taxanes.

TBP: gene coding for the TATA box-binding protein, a transcription initiation factor. The protein product, TBP, plays a key role in the activation and regulation of eukaryotic promoters that occurs when it binds to TATA elements in promoter regions, initiating the assembly of a preinitiation complex involving RNA polymerase II and several initiation factors.

TBP2 (thioredoxin binding protein 2): protein involved in the binding of thioredoxin, leading to decreased levels of thioredoxin in cells.

TCR (T-cell receptor): a disulfide-linked heterodimer of highly variable α and β chains in complex with CD3 molecules on T-cell surfaces. In some subsets of T cells, disulfide-linked highly variable δ and γ chains are in complex with CD3 molecules. Thus, T cells carrying these receptors are designated either as α:β or δ:γ T cells, respectively.

TCRγδ: T cells bearing the γδ T-cell receptor that typically contribute to host defense mechanisms at epithelial surfaces.

TEL: a subset of the ETS family of transcription repressors.

TEL:RUNX1: the most common gene rearrangement associated with childhood cancer. TEL:RUNX1 is a result of the chromosomal translocation t(12;21) seen in pediatric acute lymphoid leukemia. The fusion protein functions as a transcriptional repressor.

telomerase: also called telomere terminal transferase, an enzyme made of protein and RNA subunits. Its role is to elongate chromosomes by adding telomeric sequences to the end of existing chromosomes.

telomeres: a tandem array of short DNA sequences that occur at the physical ends of chromosomes. Telomeres have addressed the issue of the inability of DNA polymerases to replicate the ends of DNA strands. As a result, during the course of replication, telomeres in somatic cells shorten with each cell division.

temozolomide: see temozolomide (TMZ).

temozolomide (TMZ): an imidazotetrazine derivative that is administered orally. Temozolomide is a prodrug that undergoes rapid nonenzymatic conversion to the reactive compound MTIC at physiologic pH; MTIC is believed to be involved in the alkylation of DNA. Alkylation (methylation) occurs primarily at the O6 and N7 positions of guanine. Temozolomide passes through the blood-brain barrier and has shown activity in the treatment of primary brain tumors.

temsirolimus: an inhibitor of the mammalian target of rapamycin, a member of the phophoinositide kinase-related family proteins. Also called CCI-779.

terminal respiratory unit (TRU): a physioanatomical unit of the terminal airway in the lung that is conducted by single respiratory bronchioles to a few alveoli. This unit is a primary site of gas exchange. The surface is covered by a characteristic epithelium (ie, pneumocytes).

TERT: catalytic subunit of telomerase reverse transcriptase.

tertiary lymphoid structure: lymph node–like formations that contain T cells, B cells, and antigen-presenting cells in an organized structure. These formations occur in nonlymphatic sites.

test set: an experimental set that is used to determine the validity of classifiers that have been defined in a training set.

TFAP (transcriptional factor AP-2 alpha): regulator of cell proliferation, differentiation, and cell death. In the absence of AP-2, the deregulated expression of critical genes involved in metastases and invasion, including c-kit, MUC18, thrombin receptor, and MMP-2, is responsible for the progression to the metastatic phenotype through processes involved in resistance to apoptosis, adhesion to endothelial cells, and increased angiogenesis and invasion.

TFAR19 (TF1 cell apoptosis-related gene 19): gene coding for a protein expressed in tumor cells during apoptosis independent of the apoptosis-inducing stimuli. Before apoptosis induction, this gene product is distributed in both the nucleus and cytoplasm. Once apoptosis is induced, the level of this protein increases, and by relocation from the cytoplasm, it accumulates in the nucleus. Although its exact function is not defined, this protein is thought to play an early and universal role in apoptosis. TFAR19 is also called PDCD5 (programmed cell death 5).

TFIIE: transcriptional factor IIE has multiple roles in transcription initiation. It recruits TFIIH, a protein complex with subunits having DNA helicase activities.

TFIIF: an α2β2 heterotetramer of RAP74 and RAP30 subunits (RAP; RNA polymerase II-associating protein), which participates in stable recruitment of RNA polymerase II to the promoter.

TFPI (tissue factor pathway inhibitor): a de novo regulator of coagulation activated by tissue factor. TFPI contains protease inhibitor domains for the inhibition of factor Xa and VIIa/tissue factor complex.

TFRC: gene coding for the transferrin receptor, which mediates cellular uptake of iron.

TG4010: a second-generation modified vaccinia virus Ankara harboring nucleotide sequences encoding MUC1 and interleukin 2 (IL-2). It has been engineered to retain its immunogenicity but is replication defective in mammals. IL-2 production by this vaccinia virus potentiates cell-mediated and humoral responses. It is the ability to target MUC1 and coexpression of IL-2 in the vaccine vector providing local release and improved T-cell priming that are believed to the advantages of this vaccine. TG4010 has been studied for its potential to treat a variety of cancer types.

TGF-α (transforming growth factor alpha): a cytokine with 30% homology to epidermal growth factor. TGF-α also binds to epidermal growth factor receptor and mediates proliferative and survival signals.

TGF-β receptors: family of receptors for TGF-β. See TGF-β (transforming growth factor beta).

TGF-β (transforming growth factor beta): a tumor suppressing cytokine with growth inhibitory effects in epithelial cells. TGF-β may also act as a tumor promoter by eliciting an epithelial-to-mesenchymal transition. TGF-β inactivates several proteins involved in cell cycle progression and thereby exerts its growth-inhibitory effects on epithelial cells by causing them to arrest in the G1 phase of the cell cycle.

TGF-β type II receptor: receptors that form heterooligomeric complexes in response to ligand-dependent activation. These complexes exhibit serine/threonine kinase activity. Activated TGF-β type II receptor initiates signal transduction by transphosphorylating the type I receptor.

Th1: a categorization of helper (CD4+) T-cell responses, manifested typically by production of cytokines, including interferon-γ, interleukin-2, and tumor necrosis factor α, and with functional importance in supporting generation of cytotoxic T-cell responses.

Th2: a categorization of helper (CD4+) T-cell responses, manifested typically by production of cytokines, including interleukin-4, interleukin-5, and interleukin-10, and with functional importance in supporting generation of B-cell and antibody responses.

thalidomide: an agent that has an adverse effect on fetal limb bud development with teratogenic activity mediated by angiogenesis inhibition. Reports on its antitumor activity have resulted in its evaluation in clinical trials in patients with several solid tumors as well as hematopoietic diseases.

THBS (thrombospondin): family of extracellular adhesive proteins with five members (THBS-1 through THBS-4, and cartilage oligomeric matrix protein [COMP]). THBSs play a role in several cellular processes, including platelet aggregation and angiogenesis.

therapeutic index: a ratio of the amount of a therapeutic agent that causes the therapeutic effect to the amount that causes toxicity. To calculate the therapeutic index, the dose that produces toxicity in 50% of the population (median toxic dose) is divided by the minimum effective dose for 50% of the population (median effective dose). A high therapeutic index translates to a higher threshold for toxicity and a greater potential to reach maximally efficacious doses.

therapeutic vaccine: a vaccine used for induction of humoral and/or cellular immune responses against an antigen or set of antigens to treat existing disease. In contrast, prophylactic vaccines are used to induce humoral and/or cellular immune responses against an antigen or set of antigens to prevent future disease.

thiopurine S-methyltransferase: an enzyme that catalyzes the S-methylation of aromatic and heterocyclic compounds with sulphydryl groups and is important in the clearance of drugs such as 6-mercaptopurine and azathioprine. Genetic polymorphisms in the enzyme and their clinical relevance to myelosuppression were the first to be studied in the field of pharmacogenetics.

thrombocytopenia: decreased platelet count.

thromboxanes: formed from arachidonic acid (like leukotrienes) but using a separate biochemical pathway that involves the synthesis of prostaglandins. Thromboxane A2 is important in platelet aggregation and mediates vasoconstriction, whereas thromboxane B2 is the stable hydrolysis product of thromboxane A2 and is an indicator of thromboxane biosynthesis. The anti-inflammatory properties of aspirin result from its inhibition of prostaglandin synthase, the enzyme that initiates the synthesis of thromboxanes from arachidonic acid.

thymidylate synthase: catalyst for the synthesis of deoxy-thymidine monophosphate (dTMP) from the substrate dUMP, with 5,10-methylene tetrahydrofolate acting as a cofactor. Because of its central role in DNA synthesis, thymidylate synthase has been the target of cancer drugs. In addition, it is involved in the pharmacokinetics of fluorouracil, and polymorphisms in thymidylate synthase promoters are associated with a diminished response to fluorouracil.

thymidylate synthase (TS): an important enzyme in the formation of de novo thymidylate (dTMP), essential for DNA synthesis, from fluoropyrimidines. In the catabolism of fluorouracil, fluoroUMP is formed, which is the substrate for thymidylate synthase, converting it to deoxythymidine monophosphate.

Tie2: an endothelial cell receptor tyrosine kinase. Tie 2 activates cell migration processes on activation by angiopoietin. Given that it has overlapping activities with vascular endothelial growth factor receptor, Tie2 may be involved in capillary sprouting that is seen in mature vasculature.

Tie2/Tek: another name for Tie2. See Tie2.

TIMP: see TIMP (tissue inhibitor metalloproteinases).

TIMP (tissue inhibitor of metalloproteinases): a family of secreted proteins. TIMPs 1-4 are matrix metalloproteinase inhibitors modulating the activity of soluble, matrix-bound, and cell-associated matrix metalloproteinases of extracellular matrix proteins (eg, collagenases, stromelysins, and gelatinases) during the processes of tissue remodeling, inflammation, and tumor invasion and metastases. Except for TIMP4, TIMPs show wide tissue distribution.

TIMP1: see TIMP (tissue inhibitor metalloproteinases).

TIMP-4: the most cardiac specific TIMP, with weak identity to TIMP-1 and approximately a 50% identity to TIMP-2 and TIMP-3. Unlike other TIMPs, which have specificity toward inhibition of matrix metalloproteinases, TIMP-4 inhibits all classes of matrix metalloproteinases. See TIMP (tissue inhibitor metalloproteinases).

tipifarnib: a farnesyl transferase inhibitor. See FT (farnesyltransferase).

tirapazamine: a bioreductor drug activated under hypoxia to inhibit topoisomerase II. Tirapazamine also binds to DNA.

tissue microarray: microarray used to analyze the expression of genes of interest simultaneously in multiple tissue samples. Tissue microarrays consist of hundreds of individual tissue samples placed on slides ranging from 2 to 3 mm in diameter. Using conventional histochemical and molecular detection techniques, tissue microarrays are powerful tools for evaluating the expression of genes of interest in tissue samples. In cancer research, tissue microarrays are used to analyze the frequency of a molecular alteration in different tumor types, to evaluate prognostic markers, and to test potential diagnostic markers.

TMP (tissue metalloproteinase): a family of zinc-dependent proteinases that is involved in matrix degradation (see MMP [matrix metalloprotease (metalloproteinases)]). In addition, these enzymes can cleave and activate nonmatrix proteins such as cytokines, growth factors, and transmembrane receptors.

TMPRSS2: a member of the serine protease family. The gene is upregulated by androgenic hormones in prostate cancer cells and downregulated in androgen-independent prostate cancer tissue. TMPRSS2 is fused to ETS transcription factors, such as ERG and ETV1, in 40%-80% of prostate cancers in humans.

TMPRSS2: a member of the serine protease family. The gene is upregulated by androgenic hormones in prostate cancer cells and downregulated in androgen-independent prostate cancer tissue. TMPRSS2 is fused to ETS transcription factors, such as ERG and ETV1, in 40%-80% of prostate cancers in humans.

TMPRSS2:ERG (transmembrane protease, serine 2–v-ets erythroblastosis virus E26 oncogene homolog [avian]): the recurrent gene fusion between androgen-regulated TMPRSS2 and ERG, which is present in more than 50% of prostate-specific antigen–screened prostate cancers. It results in ERG protein overexpression in hormone-naive prostate cancer.

TMS1 (target of methylation-induced silencing): a CpG island-associated gene that is hypermethylated and silenced in cells overexpressing DNA cytosine-5-methyltransferase-1. The gene codes for a protein containing a COOH-terminal caspase recruitment domain (CARD) but is structurally dissimilar to other CARD proteins.

TNFα (tumor necrosis factor alpha): a cytokine with pleiotropic activities. TNFα (originally called cachexin) is secreted by several types of cells (eg, macrophages, monocytes, neutrophils, T cells) in response to a variety of stimuli (eg, interferons, interleukin-2, platelet-activating factor). It acts as a cytolytic and cytostatic agent on several cell types. In addition, by promoting thrombotic processes, TNFα is significantly involved in pathologic processes, including venous thromboses and arteriosclerosis. It is also a potent activator of angiogenesis in vivo.

TNP-470: an analog of the fungal product fumagillin that disrupts angiogenesis through specific inhibition of endothelial cell proliferation and migration.

tolerogenic: not capable of inducing an immune response.

toll-like receptor: a class of receptors that are present on many cells in the body and are responsible for initiating innate immune responses. They are particularly effective at triggering dendritic cells.

topoisomerase I: an enzyme that acts on the topology of native DNA by changing the supercoiled structure of DNA. Topoisomerase I makes a nick in one DNA strand, twists it around the other, and religates the nicked strand.

topoisomerase II: an enzyme that catalyzes the ATP-dependent transport of one segment of DNA duplex through another DNA duplex. Topoisomerases change the topology of DNA by controlling the essential functions of separating intertwined daughter chromosomes.

total mesorectal excision (TME): the complete excision of the visceral mesorectal tissue to the level of the levators.

TP53: gene encoding p53, a nuclear protein that plays an essential role in the regulation of cell cycle. Mutations in p53, resulting in proteins that fail to bind DNA, frequently occur in several human cancers, resulting in a loss of tumor-suppressor activity. Alterations of the TP53 gene occur as somatic mutations in human malignancies and as germline mutations in some cancer-prone families with Li-Fraumeni syndrome.

TP53BP1: the gene encodes for tumor protein p53 binding protein 1, a key transducer of DNA damage checkpoint signal.

TP73: family member of the tumor suppressor gene TP53. Although p73 was initially described as a tumor suppressor protein, nowadays it is accepted that it could exert both a tumor suppressor or an oncogenic function depending on its isoforms.

TRAIL (TNF-related apoptosis-inducing ligand): ligand identified on the basis of sequence homology to members of the tumor necrosis factor family. TRAIL induces apoptosis by binding to TRAIL receptors.

TRAIL-R: death receptors used by the ligand TRAIL. TRAIL-R1 (also called DR4) and TRAIL-R2 (also called DR5), the principal receptors for TRAIL, have an intracellular death domain responsible for mediating apoptosis. In addition, TRAIL-R3 and TRAIL-R4, which lack the death domain, are decoy receptors and inhibit apoptosis. The decoy TRAIL receptors are abundantly present in normal cells, perhaps as a factor for regulating apoptosis.

TRAIL-R1: see TRAIL-R.

TRAIL-R2: see TRAIL-R.

TRAIL-R3: see TRAIL-R.

TRAIL-R4: see TRAIL-R.

training set: samples used in a developmental study to define a classifier. The classifier can be internally validated in the test set of samples; those that were not used to develop the classifier.

transactivation: induction of the transcription by a transcription factor binding to DNA and activating adjacent proteins.

transarterial chemoembolization (TACE): treatment of hepatic malignancies by injecting a mixture of chemotherapy, lipiodol, and an embolic agent into the hepatic artery supplying tumor.

transcription therapy: agents that directly target the transcriptional machinery.

transcriptional activator: proteins with conserved, structural motifs or domains that positively modulate the transcriptional machinery of cells. Transcriptional activators recruit other molecules called co-activators to the transcriptional machinery.

transcriptional factors: see transcriptional regulatory complexes.

transcriptional profiling: see gene expression profile.

transcriptional regulators: see transcriptional activator and transcriptional repressors.

transcriptional regulatory complexes: complexes of proteins that regulate the transcriptional activity in cells. Specific regulatory sequences exist in genes or in mRNAs that bind specific transcriptional factors. TFIIA, B, and C, for example, are transcriptional factors regulating RNA polymerase II activity. The number and type of regulatory elements can vary in each gene or mRNA, giving rise to a combination of transcriptional factors, each exerting different regulatory control. Transcriptional complexes are also unique for different cell types.

transcription factors: complexes of proteins that regulate the transcriptional activity in cells. Specific regulatory sequences exist in genes or in mRNAs that bind specific transcriptional factors. TFIIA, B, and C, for example, are transcriptional factors regulating RNA polymerase II activity. The number and type of regulatory elements can vary in each gene or mRNA, giving rise to a combination of transcriptional factors, each exerting different regulatory control. Transcriptional complexes are also unique for different cell types.

transcriptional repressors: proteins with conserved, structural motifs or domains that negatively modulate the transcriptional machinery of cells. Transcriptional repressors recruit other molecules called co-repressors to the transcriptional machinery.

transcriptome: the complete expressed product of the entire genome in a particular cell, tissue, or biofluid at a specific point in time.

transfection: infection of a host eukaryotic cell with purified DNA resulting in subsequent replication of the DNA in the host cell.

transhiatal esophagectomy: removal of the thoracic part of the esophagus by dissection superiorly through a cervical incision and inferiorly with a transhiatal approach through an abdominal incision. A part of the esophagus in the upper mediastinum is mobilized blindly. Adequate lymphadenectomy can be performed to the subcarinal level.

translocation: a translocation of genetic material from one chromosome to another, chromosomal translocations occur during meiosis when chromosomal breaks occur. However, in translocations, fragments of one chromosome rejoin to other chromosomes.

transphosphorylation: an activated receptor acting as a stimulus to phosphorylate another receptor in the cell in the absence of a second stimulus.

transthoracic esophagectomy: removal of the thoracic part of the esophagus through a thoracotomy incision. The mobilization of the thoracic part of the esophagus and lymph node dissection in the mediastinum can be done under direct vision, which allows for more adequate lymphadenectomy.

trapoxin: a small molecule histone deacetylase inhibitor.

trastuzumab: a humanized anti-ErbB2 monoclonal antibody approved for treating patients whose breast cancers overexpress the ErbB2 protein or demonstrate ErbB2 gene amplification. It is currently being tested in combination with other therapies.

treatment-related neuroendocrine prostate cancer: an often under-recognized late manifestation of prostate adenocarcinoma, the development of neuroendocrine prostate cancer in the form of small-cell or large-cell type, which is considered to be a hormone-refractory subtype of prostate cancer after hormonal therapy or other treatment. This tumor does not secrete prostate-specific antigen and is a highly aggressive subtype of prostate cancer characterized by unresponsiveness to hormone therapy; presence of lytic bone lesions; rapid disease progression of and presence of visceral metastases; marked prostatic enlargement; and disproportionately low prostate-specific antigen levels in the setting of metastatic disease.

trial-level surrogacy: the association between the treatment effects on the true and surrogate end points at the population level.

triple-negative breast cancer (TNBC): breast tumors that are negative for estrogen and progesterone receptor expression and that also underexpress HER-neu.

TrkA: gene encoding the tyrosine kinase TrkA receptor. TrkA binds to neurotrophins and serves as the high-affinity receptor for the nerve growth factor, required for normal development of the peripheral nervous system as well as the function of central forebrain neurons. Neurotrophin-3 and neurotrophin-4/5, but not brain-derived neurotrophic factor, are also ligands for TrkA.

TrkB: gene encoding TrkB, a member of the neurotrophic tyrosine receptor kinase family. This kinase is a membrane-bound receptor that, upon neurotrophin binding, phosphorylates itself and members of the MAPK pathway. Signaling through this kinase leads to cell differentiation. It plays an important role in maintaining neuronal cell populations in the neocortex of adults. The neurotrophins, NT4 and NT5, and the brain-derived neurotrophic factor are the ligands for TrkB.

truncating mutation: any mutation that causes premature truncation of the normal protein product. Examples of mutations that can cause truncation are nonsense mutations and out-of-frame deletions, insertions, or insertions/deletions.

tryptase: a unique serine protease whose enzymatic is dependent on the integrity of its tetrameric structure, which is, in turn, dependent on the glycosaminoglycan of mast cells, heparin. Thus tryptase is often used as a marker for mast cells, and tryptase and heparin proteoglycans are colocalized within mast cells. Degranulation of mast cells is also associated with their cosecretion.

TSC1 (tuberous sclerosis protein 1): see hamartin.

TSC2 (tuberous sclerosis protein 2): see tuberin.

TUBB: codes for beta-tubulin.

tuberin: a protein product of the tuberous sclerosis 2 (TSC-2) tumor suppressor gene. Tuberin is a phosphoprotein that negatively regulates the phosphatidylinositol pathway. Tuberin possesses a GTPase activity and functions along with hamartin to convert Rheb to the inactive GDP-bound form.

tubulin: component of microtubules, which are essential components of the eukaryotic cytoskeleton. The three tubulin families are alpha, beta, and gamma. Alpha and beta tubulins are components of microtubules, and gamma tubulins play a critical role in microtubule assembly.

tumor-associated antigens: proteins associated with tumors that elicit an immune response in tumor-bearing subjects.

tumor-host interaction: the evolving cross-talk between different cell types within the tumor and its host environment. Cancer cells can subvert the normal tissue architecture and reprogram the activity of stromal cells to their advantage, such as promoting the formation of new blood vessels or the recruitment of inflammatory cells, which are key events promoting cancer cell survival, invasion, and metastasis.

Tumor-Node-Metastasis (TNM): a cancer staging system based on size and extent of tumor, nodal involvement, and presence/absence of metastases.

tumor repopulation: the regrowth of cancer cells into a radiated area after initial therapy.

tumor suppressor genes: genes whose products typically function to inhibit aspects of the neoplastic phenotype and are subject to inactivating, or loss-of-function mutations, which contribute to tumorigenesis.

tumor-suppressor proteins: proteins expressed by tumor suppressor genes. See tumor suppressor genes.

TUNEL staining: a procedure for detecting apoptotic cells. Because DNA fragmentation is a hallmark of apoptosis, the TdT-mediated dUTP-biotin nick end-labeling (TUNEL) uses the enzyme deoxynucleotidyl transferase (TdT) to directly label the fragmented DNA ends. The apoptotic cells can then be either quantified by using flow cytometry or visualized in tissue sections by using colorimetric reagents.

Turcot's syndrome: an autosomal dominant or recessive childhood condition associated with mutations in mismatch repair genes. Turcot's syndrome is characterized by brain tumors (glioblastoma, astrocytoma, or spongioblastoma) associated with colonic adenomatous polyposis, which becomes malignant in the fourth and fifth decades. Other features include café-au-lait spots and cutaneous port wine stains.

TW-37: small molecule inhibitor of Bcl-2 and the Bcl-2 family of antiapoptotic proteins, induces apoptosis in sensitive cells. TW-37 is an example of a new group of molecules designed to inhibit Bcl-2 and related proteins by targeting their BH3-binding domain. TW-37 is currently in preclinical trials.

TWIST2: a bHLH transcriptional factor important in neural and limb development. The oncogenic properties of TWIST2 are associated with its antagonistic effects on p53-induced apoptosis.

two-way contingency table: a tabular representation of categorical data that shows the frequencies for particular combinations of values of two discrete variables, X and Y. Each cell in the table represents a mutually exclusive combination of X and Y values. A chi2-based P value can be calculated for a contingency table and is used to determine whether there is a statistically significant association between the two variables in the contingency table. A 2 × 2 contingency table refers to a table in which X and Y are binary variables.

type 1 collagen: the major component of bone. Type 1 collagen accounts for more than 90% of the organic matrix of bone.

type 1 endometrial carcinoma: an estrogen-dependent subtype of endometrioid carcinoma expressing both estrogen and progesterone receptors that has a generally good prognosis.

type 2 endometrial carcinoma: a non–estrogen-dependent subtype of endometrioid carcinoma (eg, clear cell and serous papillary carcinomas) that has a generally poorer prognosis compared with Type 1 (ie, hormone dependent) subtype.

tyrosinase: melanocyte differentiation antigen that is shared between melanomas and melanocytes, which is the origin of melanomas. Tyrosinase is the rate-limiting enzyme in the synthesis of melanin.

tyrosine kinase: generic name for enzymes that transfer a terminal phosphate group from ATP to specific protein tyrosine residues. Tyrosine kinases are a member of the family of protein kinases.

tyrosine kinase domain: the three-dimensional structural motif in proteins having tyrosine kinase activity.

tyrosine kinase inhibitors: molecules that inhibit the activity of tyrosine kinase receptors. Tyrosine kinase inhibitors are small molecules developed to inhibit the binding of ATP to the cytoplasmic region of the receptor (eg, gefitinib), thus further blocking the cascade of reactions that is activated by the pathway.

tyrosine kinase receptors: receptors belonging to the tyrosine kinase family (eg, epidermal growth factor receptor, platelet-derived growth factor receptor), which are activated through the auto- or transphosphorylation of tyrosine residues in the cytoplasmic region of the receptors in an ATP-dependent manner.

tyrosine phosphorylation: see tyrosine kinase receptors.


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