9th Annual Symposium on Men's Health: Glossary of Terms Handout

June 2, 2011

Glossary of terms from the presentation "Prostate Cancer: Basic Biology in the New Millenium"
By Perry Karfunkel, MD

• APUD: amine precursor uptake and decarboxylation system.  Endocrine cells dispersed among other tissues which release hormones that may be dispersed within the circulatory system (such as insulin produced by Isle of Langerhans cells or calcitonin) or which may act on nearby cells (such as serotonin) [thus termed paracrine secretory cells].  These cells may be localized within an organ (as Isle of Langerhans cells are localized in the pancreas) or they may be dispersed within many organs of the body (such as serotonin-producing cells which are found within the brain but are also found within the prostate).  Alternatively they may fall into both categories: the C-cells of the thyroid are the source of calcitonin released into the blood stream to control calcium metabolism within the body but are also found interspersed among epithelial cells of the prostate where they produce calcitonin that may act on adjacent prostate cells and/or may be released at the ends of inter-cellular filopodia that abut onto the lumen of the prostatic exocrine ducts to be included in semen.
  
  
• BPH-I.  An "immortalized" cell line that grows indefinitely in tissue culture and which is derived from non-tumor human prostate epithelial cells (originally derived from the gland of a man with benign prostatic hypertrophy). 
  
  
• Cadherin-  calcium-dependent adhesive protein:  The molecule itself has a large extracellular domain that binds to the same molecule of cadherin on an adjacent cell:  this is homophilic binding.   The adhesive interaction is initiated through the dimerization of two cadherins on the same cell surface:  this dimerized molecule produces a particularly strong cell-cell adhesion,  visualized as an adherens junction.  Cadherins have a membrane-spanning domain and a cytoplasmic domain.  The cytoplasmic domain interacts with intracellular molecules (called catenins) which themselves link this domain to the actin-based cytoskeleton of the intracellular matrix.  This linkage is necessary for the cell-cell adhesions to occur; if they are disrupted because of mutations in either E-cadherin or in catenin then cell adhesion is lost. 
  
  
• Cadherin-11 is an osteoblast cadherin expressed in prostate cancer cells derived from bone metastases;  presumably it is the link to the mechanism which is responsible for prostate cancer cells going to bone metastases,  and may be an example of how all cancer types choose the specific locations to which they metastasize. 
  
  
• Catenins: a series of proteins found just below the cell membrane which are linked to the intracellular component of cadherins on one side and to the cytoskeletal actin filaments that extend further into the cytoplasm of the cell. The gene for the synthesis of catenin-alpha is located on chromosome 5; the gene for catenin-beta is on chromosome 3 and the gene for catenin gamma is on chromosome 11.  Beta or gamma catenins bind to the cytoplasmic tail of E-cadherin; alpha catenin binds to those and to the actin filaments.  P-120 catenin has been shown to act as an inhibitor of cadherin function in colon cancer cells. 
  
  
• Cytokeratins: protein filaments within cells that contain keratin; there are more than 20 different such proteins known, and the type of keratins found within a cell are often organ-specific.  Immuno-histopathological staining for one or another cytokeratin is therefore useful in determining the organ-of-origin or cell-type of origin of tumors; thus, for example a colon cancer can have epithelial cells (of an adenocarcinoma) or neuroendocrine cells or both.
  
  
• Cytokines:   small cell-signaling protein molecules.  Interleukins are cytokines derived from white blood cells (leukocytes) of the immune system.  These can function at 10-12 concentrations.  Among other things, tumor-derived cytokines are thought to lead to muscle-wasting in patients with cancer by interfering with mitochondrial function.  This leads to the "cancer-associated cachexia" which is often the actual cause of death in cancer patients. 
  
  
• "Ets" gene:  A gene first described in leukemia virus "E twenty six."   It has five subfamilies, one of which is the ERG (Ets Related Gene). 
  
  
• ERG gene: This has multiple trasnscription sites and is considered a "promoter gene."  Its function depends upon the number of copies of it which are present in any one cell.  It can either activate or negatively regulate the expression of other genes.   The over-exprssion of ERG is considered to be one of the first steps in the development of prostate cancer.   The ERG gene can fuse with another gene,   the androgen-dependent TMPRSS2 gene); when this "fusion-gene" is formed the likelihood of tumor spread into the seminal vesicles is enhanced, as is the likelihood that distant metastases will form or be found.
  
  
• FGF: a family of 22 (presently-known) fibroblast growth factors--  these are tyrosine kinases that activates intracellular signaling pathways once it binds to the trans-membrane FGF receptor, triggering the intracellular signaling it evokes. In the prostate,  this is evoked by the FGF receptor 2 alpha: this is found in developing prostate epithelium and in prostates that have been allowed to atrophy after castration and are then allowed to regenerate by having androgens re-introduced into the host animal. In adults,  the FGF receptor 2 alpha is only present in the basal cells of prostate glandular lobules,  but not in the cells at the surface epithelium of the lobule: it is these basal cells that are in contact with the mesenchymal base of each lobule.
  
  
• "Floxed gene"   The inactivation of a gene by flanking it between two LoxP genes which act to inactivate the gene in question,  (which is then considered "knocked out").  The process is brought about by creating gene translocations/ introductions within a genotype using siRNA (see below) incubated with the tissue involved which is itself sectioned on slides after frozen sectioning of the dissected tissue.  
  
  
• GATA: a family of "zinc-fingered" transcription factors which recognize the G-A-T- A base sequence present in the DNA of many promoter genes.  GATA-2 i s a nuclear transcription factor the presence of which correlates with a 2.65-fold increased risk of prostate cancer recurrence after prostatectomy. 
  
  
• GnRH antagonists/ agonists:  peptide derivatives of GnRH which bind to the pituitary and block the hypothalamic-pituitary axis which normally leads to the production of LH (luteinizing hormone) and FSH (follicle stimulating hormone) by the pituitary.   LH normally stimulates testicular synthesis of testosterone,  so antagonists sharply reduce its synthesis and thereby "chemically castrate" a patient.  They slow the growth of prostate cancer cells and they reduce bone pain associated with enlarging bony prostate cancer metastases. GnRH agonists bind tightly to the GnRH binding site in the pituitary gland and block these binding sites, without causing them to stimulate the production of LH and FSH.  By  blocking the  normal agonist from stimulating the pituitary,  they also lead to "chemical castration" by preventing the pituitary from being stimulated to release LH.  Lupron and Eligard are commonly-used (and well-known) GnRH agonists,  but others have been developed as well. 
   
• GSTP: a family of four classes of enzymes (glutathione S-transferase P's) which conjugate reduced glutathione to reactive-oxygen electrophilic molecules as well as some hydrophobic molecules and therefore inhibit their ability to act as carcinogens.  The family of enzymes is encoded by the GSTP1 gene.
  
  
• Histones:  large complexes of proteins found in the groove within a DNA strand; these come in functional units of protein octomer (eight protein molecules bound together);  one functional octomer typically extends over 146 DNA base pairs, and this is called a "core unit of function."  Histones can be either acetylated or methylated and this occurs as a result of the activity of either histone acetyl-transferase,  histone deacetylase, or histone methyl-transferase enzymes.  The  activation or suppression  of particular genes as a result of effecting changes in their histone core units may activate or suppress tumor activity; chemotherapeutic drugs that function at this level are being researched (e.g. methyl-transferase inhibitors decitabine and zebularine).  Antioxidants can affect histones as well;  green tea prevents hypomethylation of histones: this can benefit both BPH and prostate cancer,  but it seems to increase the risk of colon cancer.
  
  
• Kallikreins: peptidases (protein-cleaving enzymes) which are a subgroup of the serine proteases (see "serine protease").  The first one was detected in the pancreas: "kallikrein" is derived from the Greek word for pancreas; kallikreins 3 is also called PSA: prostate-specific antigen.  Kallikrein2 is also studied in that context.   The genes for these serine proteases are  located on chromosome 19; the enzymes are present in semen, where their function is to hydrolyze and liquefy gelatinous semen after ejaculation to facilitate sperm motility through the semen in order to reach an ovum.
  
  
• "knockdown"-a term used to refer to the product of a gene having been "turned off" or having its action blocked, even after the transcription of RNA that would create its gene-product.   Genes are usually knocked-down by manipulation of the genetic mechanisms of the cell involved using other genetic components (such as siRNA's [see below].
  
  
• MAP kinase: a family of  mitogen activated (protein) kinase enzymes that transfer a phosphate group onto a protein, thus phosphorylating it.
  
  
• MMP-9:  One of a group of matrix metalo-proteinase enzymes.  Increased levels of MMP-9 is found in advanced Gleason-grade prostate cancer; reduction of MMP-9 by si-RNA leads to significant reduction of invasiveness of tumors in both 3-dimentional tissue culture/extracellular matix gels and in tumors implanted into mice; inhibition of MMP-9 by chemotherapy drugs decreases cell proliferation,  cell migration and cell invasiveness- these represent a new class of chemotherapy drugs being tested for prostate cancer
  
  
• Prostate cancer  cell lines in culture:  
  
  
  • DU145: derived from brain metastases
    
    
  • LNCaP: derived from lymph node metastases: these are androgen-receptor positive: they require androgens for cell growth and survival
    
    
  • C4-2B4 cells: bone-metastasis derived prostate cancer cells that are castration-resistant
    
    
  • PC3: derived from bone metastases: these cells are androgen-receptor negative: they do not require androgens for cell growth and survival and do not respond to anti-androgen chemotherapy-  they are termed "castration-resistant" for this reason.
    
    
  • BPH-1 cells are non-tumorigenic SV40-immortalized human prostate epithelial cells
    
    
• PDEF:   prostate-derived Ets factor: see above under Ets gene.  A transcriptional factor that activates PSA; its action is androgen-independent. 
  
  
• PKD3:  protein-kinase D3; an enzyme that seems to be rate-limiting in cell proliferation in LNCaP prostate cancer cells in tissue culture;  unlike the situation in these cells,  it also inhibits migration in tissue culture and invasiveness in PC3 prostate cancer cell and DU145 prostate cancer cells.  Inhibitors of this enzyme are under study as chemotherapeutic agents. 
  
  
• PSA:  prostate specific antigen.   PSA is a serine protease:  (see below).    PSA is known to cleave Insulin-like Growth Factor Binding Protein 3 (IGFBP-3),  which is a known tumor-suppressor-gene product.  Thus a rise in PSA may be not only a marker for the presence of prostate cancer (when it is found in a patient's serum) but may also be mechanistically related to the growth of prostate cancer by its reduction of the tumor-suppressing IGFBP-3.
  
  
• Runx2:  a tissue-specific transcription factor associated with metastases to bone: this is found in high concentration in both prostate cancer and breast cancer metastases in bone.  It is found in tumor cells that are related to bone metastases.  Runx2 is itself a histone deacetylase inhibitor but it also acts on non-histone proteins the activity of which is dependent upon the extent of their acetylation.  Depleting this in such cells put into tissue culture by siRNA interference techniques subsequently inhibits migration and invasive properties of these cells such that it prevents subsequent metastases to bone if these malignant cells are transferred back into host graft animals.  As a "transcription factor"  Runx2 activates multiple genes in cells; it is an activator of many genes associated with osteoblastic differentiation and skeletal morphogenesis in development--  the first gene in this family was associated with "runt" growth, which is the source of its name.  Histone-deacetylase inhibitors are targets of chemotherapy for metastatic prostate cancer (SB939); many others are being tried for leukemias and lymphomas.
  
  
• Serine proteases.  A series of enzymes secreted by both pancreas and prostate cells which cleave proteins at a serine site; PSA is one such serine protease.  They act both to break down cell adhesions to neighboring cells as well as to break down collagen type 1 and thereby allows cells to migrate and subsequently penetrate through an extracellular matrix stroma surrounding normal (or well-differentiated malignant) prostate epithelial cells and thus they facilitate invasiveness.  Protein C is a serine protease as well:  when it is genetically deficient a patient is at risk for deep vein thrombosis and pulmonary emboli.  Genetically deficient protease in the lung leads to thick secretions associated with cystic fibrosis; genetically excessive pancreatic proteases lead to self-digestion of the pancreas in chronic pancreatitis. 
  
  
• Serpin molecules:   serine protease inhibitors
  
  
• siRNA:  small interfering RNA or small interference RNA; these act as "silencing" RNA's which act to bring about post-transcriptional silencing of gene function.  These can "knockdown"  or "knockout" the function of a particular gene if they are introduced into a cell otherwise expressing that gene and introduced into that cell's function as it divides by using a plasmid with itself divides when the cell divides,  so active siRNA remains present in daughter cells rather than being diluted out as the original cells divide and proliferate. siRNA's may have therapeutic benefit in disease management; Phase 1 trials using them for macular degeneration of the retina are in progress; whether they will be effective in cancer treatment remains to be seen.
  
  
• SPINK1 (serine protease inhibitor Kazal-type 1): an active control agent in Ets-negative prostate cancers (i.e. TMRPSS2-ERG negative cancers; approx. 10% of all prostate cancers).   It can be assayed for in patients who have had prostatectomy and if found to be high is a harbinger of an aggressive future outcome for that patient.   Assays were done in both the University of Michigan cancer registry patients and the Swedish Watchful Waiting cohort of patients,  consisting of a total of 392 patients: those with high levels of SPINK1 had a four-fold greater likelihood of aggressive outcomes compared to those with low levels.
   
• Src kinases:  proteins which are tyrosine kinases and which regulate many cellular events; they were originally described in Rous sarcoma (src) cells.  They phosphorylate tyrosine and in the process control many protein-protein interactions within cells.  Src kinases are often found in cell membranes, typically in association with FAK (focal adhesion kinase) and constitute parts of the adhesion complexes cells have with their neighbors (associated with cadherins) these adhesive structures are adherens junctions visible by electron microscopy; in epithelial cells they often work in conjunction with a sub-family of kinases designated Frk which is in the nucleus,  and there they control gene expression. 
  
  
• TRK:  tyrosine receptor kinase- a family of protein kinases.  See src kinase.  Nerve growth factor binds with trk's in the prostate and in the process enhance cell growth and differentiation.  The nerve growth factor itself is produced by smooth muscle cells of the prostate stroma, thus representing an epithelial-mesenchymal interaction within the developing gland as well as the mature well-differentiated gland.
  
  
• TMPRSS2: a gene that encodes for trans-membrane protease serine 2: see serine protease. "Trans-membrane protease serine-2" is a protease (protein-cleaving enzyme) produced by prostate epithelial cells and found in prostate secretions. It  is controlled by the TMPRSS2 gene and which acts at a serine amino acid site. This class of enzymes act to both break down cell adhesions to neighboring cells as well as to break down type 1 collagen, thereby breaking down the stromal connective tissue surrounding a lobule of prostate epithelium.  This gene is down-regulated in "castration-resistant" prostate cancer cells.
  
  
• TRPV2 (transient receptor-potential vanilloid 2):  a cationic receptor that increases MMP-9 activity and decreases androgen-dependence and increases cell migration activity even in the absence of androgens (or in the presence of androgen-blocking drugs).  Its activation brings about hormone-blocking drug resistance ("castration resistance").
  
  
• Vimentin: an "intermediate filament" found particularly in connective tissue but also part of the cytoskeletal components of a eukaryotic cell (along with microtubules and actin fibers).  Because it is found in high quantities in fibroblasts,  it has been used as a marker for "mesodermal" cells and mesodermally-derived tissues,  and particularly as an immunohistochemical marker for sarcomas.  Vimentin is actively involved in cell-matrix adhesions as cells send out filopodia associated with their forward movement over a substrate surface,  so up-regulating vimentin enables cells to start to move on their own.