FINALS LEC: MOLECULAR DETECTION: ONCOLOGY Flashcards
Study of tumors/neoplasm growth of tissue that exceeds and is not coordinated with normal tissue
ONCOLOGY
not recurrent
benign
invasive & tending to recur at multiple sites (cancer)
malignant
movement of tumor cells from the original (primary) site of the tumor to other locations
matastasis
suffix, to the tissue of origin
-Oma
study of cancer at the molecular level
Molecular oncology
An abnormal mass of tissue that usually does not contain cysts/liquid areas
SOLID TUMORS
tumor of epithelial origin
Carcinoma
tumor of bone, cartilage, muscle, blood vessels, or fat
sarcoma
multiple cell types
teratocarcinoma
Abbormal cells in the blood grow out of control
HEMATOLOGICAL MALIGNANCIES
large nos. of WBCs populate the bone marrow & peripheral blood
Leukemia
neoplasm of lymphocytes that form discrete tissue masses
Lymphoma
Plasma cell neoplasms: abnormal plasma cells/cells form tumors in the bones/soft tissues of the body
HEMATOLOGICAL MALIGNANCIES
is caused by nonlethal mutations in DNA affecting 2 types of genes that control the cell division cycle and cell survival
cancer
2 types of genes that control the cell division cycle and cell survival:
Oncogenes
Tumor-supressor genes
● Promote cell division ● Include cell membrane receptors, that are bound by growth factors, hormones, and other extracellular signals
● Support cell survival by inhibiting apoptosis
● >100 in the human genome
Oncogenes
● Factors that control transcription/translation of genes required for cell division
● Participate in repairing DNA damage & in promoting apoptosis
● Slow down/stop cell division by counteracting the movement of the cell from G1-to S (G1 checkpoint) or G2 to M phase (G2 checkpoint)
● >30 in the human genome
Tumor-supressor genes
IN CANCER CELLS
Gain-of-function mutations resulting from:
Amplification/translocation of DNA regions containing the genes
Activating mutations that cause aberrant activity of the proteins
Oncogenes
IN CANCER CELLS
Loss-of-function genes mutations Inactivation of the gene products (deletion, translocation, mutation of the genes)
Tumor-supressor genes
Molecular diagnosis and treatment of cancer cells:
Detection of abnormalities in specific tumor suppressors or oncogenes
ANALYTICAL TARGETS OF MOLECULAR TESTING:
Tissue specific targets
Tumor-specific targets
● Molecular characteristics of the tissue from which a tumor arose
● Detection and monitoring the presence of tumor abnormal amounts or locations of DNA, RNA, proteins or other molecules from these targets
● Examples: DNA/RNA from
1. Cytokeratin genes in gastric cancer 2. Carcinoembryonic antigen in breast cancer
Tissue specific targets
● Genetic structures resulting from mutations in oncogenes & tumorsuppressor genes that are associated with tumor development
● Solid tumors, leukemias, lymphomas ● Mutated cell free nucleic acid/circulating tumor cells can be detected in blood & other body fluids
● Examples: surface receptors, mutated proteins, tumor-associated antigen, metabolic markers
tumor-specific targets
Tyrosine-kinase activity
Normal activity: cell growth and division
Overexpressed in 25%-30% of human breast cancers
Human epidermal growth factor receptor 2, HER/neu/erb-b2 1 (17q21.1)
Detection methods of Human epidermal growth factor receptor 2, HER/neu/erb-b2 1 (17q21.1)
IHC
SOUTHERN, NORTHERN, WESTERN BLOT
FISH
Chromogenic in situ hybridization (CISH)
Silver-enhanced in situ hybridization (SISH)
uses antibodies (fresh/frozen tissues)
IHC
gene amplification increased RNA & proteins
Southern, northern, western blots
direct detection of increased copy nos. of the gene in DNA
FISH
standard bright-field microscope, genome & chromosome mutation detection
Chromogenic in situ hybridization (CISH)
Normal activity: cell signaling pathways that control cell division and survival
Overexpressed in solid tumors
Epidermal growth factor receptor, EFGR (7p12)
Detection methods of Epidermal growth factor receptor, EFGR (7p12)
IHC
qPCR
SSP-PCR, SSCP, direct sequencing, NGS
to assess gene copy no. through increased gene expression
qPCR
mutations
SSP-PCR, SSCP, direct sequencing, NGS
Small GTP-binding proteins that receive signals from the cell surface proteins & activate the initial steps of the mitogen-activated protein kinase (MAPK) pathway cascade
Gain-of-function mutations in ras protooncogenes
cancers
Mutations in these genes are the most common oncogene mutations in human cancers (codons 12, 13, 22, & 61 in exons 2 & 3 of the KRAS gene)
Detection methods of mutation: direct sequencing, pyrosequencing
Kirsten rat sarcoma viral oncogene homolog, K-ras (12p12); neuroblastoma ras, Nras (1p13); & Harvey rat sarcoma viral oncogene homolog, H-ras (11p15)
Ewing sarcoma: group of tumors arising from primitive neuroectodermal tissue (PNET)
Diagnosis and prognosis: a. cytogenetic methods b. molecular methods: RT-PCR, with amplification control (GAPDH or 18S RNA) on tissue/liquid biopsies
Ewing sarcoma, EWS (22q12)
group of tumors arising from primitive neuroectodermal tissue (PNET)
Ewing sarcoma
Detection methods:
a. FISH
b. RT-PCR
c. Semi-nested PCR
d. Agarose gel electrophoresis & EtBr staining (PCR product detection)
Synovial sarcoma translocation, chromosome 18 – Synovial sarcoma breakpoint 1 & 2, SYT-SSX1, SYT-SSX2 t(X;18) (p11.2;q11.2)
rare type of cancer of the muscle, fat, fibrous tissue, blood vessels, or other supporting tissue of the body
Synovial sarcoma
Detection methods: FISH, RT-PCR, qPCR, RNA sequencing
Paired box-fokhead in Rhabdomyosarcoma, PAX3-FKHR, PAX7-FKHR, t(1;13), t(2;13)
most common soft tissue sarcoma of childhood (10% of all solid tumors in children) alveolar RMS, embryonal (RMS-E), & primitive (RMS-P)
Rhabdomyosarcoma (RMS)
Mutations in this gene is found in all types of cancers and also aids in the diagnosis of LiFraumeni syndrome
Detection methods: IHC, microarrays/panel sequencing, SSCP, direct sequencing
Tumor protein 53, TP53 (17p13)
gene product of TP53, DNA-binding protein that controls expression of other genes and participates also in the arrest of cell division in the event of DNA damage
p53
Carriers (autosomal recessive mutations) develops leukemia (B-cell lymphocytic leukemia, T-cell prolymphocytic leukemia), lymphoma (mantle cell lymphoma), or other types of cancers
Detection methods: direct DNA sequencing, SSCP, functional test for the repair of dsbreaks induced by irradiation, test for other family members
Ataxia telangiectasia mutated gene, ATM (11q22)
DNA repair and/or control of the cell cycle
ATM protein
neurological disorder that affects the part of the brain that controls motor movement & speech; predisposition to cancer
Ataxia telangiectasia (AT)
Gene products are involved in DNA dsbreak repair by homologous recombination
Screening tests for mutation: SSCP, protein truncation testes, chromosome breakage tests, etc.
Clinical application method: direct sequencing
Other detection methods: SSP-PCR, allelespecific oligomer hybridization
Breast cancer 1 gene, BRCA1 (17q21), & breast cancer 2 gene, BRCA2 (13q12)
mutation in BRCA1 (60%-80% lifetime risk of breast/ovarian cancer)
Women
mutation in BRCA2 (increased risk of breast/colon/prostate cancer)
Men
Functions as a tumor-suppressor gene, promoting cell differentiation
von Hippel-Lindau gene, VHL (3p26)
genetic condition involving abnormal growth of blood vessels in organs (eyes, kidneys, adrenal glands, etc.)
predisposition for renal cell carcinoma & other cancers
deletions, point mutations, splice-site mutations
Somatic mutations: renal cell carcinoma & tumors of the adrenal glands
Detection method: direct sequencing
Von Hippel-Lindau syndrome
Myc family proteins: increase the expression of several genes
a. c-myc oncogene (8q24.21): amplified in breast & ovarian cancer, lymphomas, & leukemias
b. l-myc (1p34.2): amplified in oral cancer c. n-myc (2p24): amplified in neuroblastoma & retinoblastoma
Detection methods: IHC, FISH, sequencing, array analysis, transcription of n-myc through qPCR
V-myc myelocytomatosis viral-related oncogene, neuroblastoma-derived, MYCN or n -myc (2p24)
coding for a membrane receptor tyrosine kinase rearranged in a variety of human cancers (1%-3% lung adenocarcinomas)
ROS1 oncogene
its gene product participates in sending signals to the nucleus
RET proto-oncogene
ALK: receptor tyrosine kinase
Chromosomal rearrangements (most common), mutations, or amplifications tumors (lymphomas, neuroblastoma, & nonsmall cell lung cancer)
Detection methods: FISH & sequencing
Anaplastic lymphoma receptor tyrosine kinase (ALK) proto-oncogene, 2p23.1
receptor tyrosine kinase
ALK
Kit protein:
transmembrane receptor with tyrosine kinase activity
Gene mutation: gastrointestinal stromal tumors (GISTs), mast cell disease, & AML
Detection methods: a. IHC: increased KIT protein
b. Sequencing: missense mutations
V-Kit Hardy-Zuckerman 4 feline sarcoma oncogene homolog, KIT, c-KIT (4q12)
transmembrane receptor with tyrosine kinase activity
Kit protein
gastrointestinal stromal tumors (GISTs), mast cell disease, & AML
Gene mutation
Contraction & expansion of nucleotide repeat sequences in DNA
MICROSATELLITE INSTABILITY (MSI)
Cause: dysfunction of 1 or more components of mismatch repair (MMR) systems
Lynch syndrome or hereditary nonpolyposis colorectal cancer (HNPCC)
Inherited cancer predisposition syndrome, 3%-5% of colon cancers & 3% endometrial cancers
Increased risk of developing other cancers MMR mutations in MSH2 & MLH1 genes Detection methods: direct sequencing, IHC, MSI analysis, PCR, gel/capillary gel electrophoresis (more bands/peaks in the tumor tissue than the normal)
National Cancer Institute: recommended the screening of BAT25 & BAT26; & D5S346, D2S123, & D17S250 for MSI determination
MICROSATELLITE INSTABILITY (MSI)
Inherited cancer predisposition syndrome, 3%-5% of colon cancers & 3% endometrial cancers
Increased risk of developing other cancers
MMR mutations in MSH2 & MLH1 genes
Lynch syndrome or hereditary nonpolyposis colorectal cancer (HNPCC)
Deletion/inactivation of a functional allele, leaving a mutated allele
Detection methods: PCR & capillary electrophoresis (amplification of heterozygous STR/VNTR loci closely linked to the disease gene)
LOSS OF HETEROZYGOSITY (LOH)
A laboratory test done on a sample of blood (plasma/serum), urine, or other body fluid to look for cells & nucleic acids released by the tumors into a person’s body fluids
LIQUID BIOPSY
LIQUID BIOPSY 2 approaches:
- Cell-free or circulating free nucleic acids
- Circulating tumor cells (CTC)
- Cell-free or circulating free nucleic acids
Targeted:
directed at specific mutations (sequencing/PCR methods)
- Cell-free or circulating free nucleic acids
Untargeted:
whole exomes or gene panels (sequencing & CGH)
most frequent source material
Plasma DNA
Mechanism of tumor metastases from 1 tissue site to another (2 to >50 cells)
Circulating tumor cells (CTC)
- Circulating tumor cells (CTC)
Isolation methods:
antibody capture, negative depletion of leukocytes
- Circulating tumor cells (CTC)
DNA:
allele-specific PCR or other sensitive methods
Series of intrachromosomal recombination events mediated by recombinase enzymes that recognize specific sequences flanking the gene segments
GENE REARRANGEMENTS
Normal intrachromosomal breaking & specific sequences flanking joining of DNA in the genes coding for immunoglobulins and T-cell receptors
V(D)J RECOMBINATION
Gene encoding the immunoglobulin heavy chain is located on chromosome 14
As B lymphocytes mature, selected gene segments are joined together so that the rearranged gene contains only 1 of each V (variable), D (diversity) & J (joining) gene segments
Immunoglobulin heavy-chain gene rearrangement in B cells