Flashcards in Unit 7 - Cancer Genetics Deck (52)
what is a "tumor"?
overgrowth of cell material
-solid VS dispersed
-clonality (proliferate to form group of similarly abnormal cells)
-benign VS malignant
what is a "malignancy"?
uncontrolled cell growth characterized by significant change in normal organizational pattern of tissues or cells
-tend to be deleterious
what is metastasis?
cells become invasive and migrate to another site, while maintaining original cell morphology
-so a tumor in the liver that came from breast cancer cells is still called breast cancer
-IOW: a primary cancer in a escondary location is known by the primary classification
what is "cancer"
malignant tumor of potentially unlimited growth that expands locally by invasion and systemically by metastasis
-overgrowth of cell material (tumor)
what are these types of cancer?
sarcoma: mesenchymal tissue (bone, cartilage, muscle, fat)
carcinoma: epitheloid tissues
hematopoietic: leukemias (WBC from bone marrow) and lymphomas (WBC from spleen and lymph nodes)
hallmarks of cancer?
-mutation or loss of genes involved in cell control, including growth/division, proliferation, metabolism
-environmental elements may influence mutation
-mutations may be inherited or acquired
-chromosome instability (CIN)
what are the 2 types of genes associated with cancer?
what is an oncogene?
a dominantly acting gene involved in unregulated cell growth and prolfieration that is capable of transforming (changing) host cells
-most are carried by viruses and associated with disease in animals, but only 5 known in humans
what are the 5 known oncogenes in humans?
1. HPV - cervical cancer (E6/7)
2. EBV - nasopharyngeal cancer, Hodgkin and Burkitt lymphoma
3. HHV-8 (herpes virus) - Kaposi sarcoma
4. HTLV-1 - T cell leukemia
5. HTLV-2 - various leukemias
what are H-ras, sis, and abl?
oncogene viruses associated with animal disease
-Harvey rat sarcoma virus
-Simian sarcoma virus
-Abelson murine leukemia virus
what are proto-oncogenes?
structurally important "housekeeping" genes necessary in human genome for cell proliferation and development
-in native state, not associated with disease
-growth factors, cell surface receptors, intracellular signal transduction, DNA binding PRO (transcription), regulation of cell cycle
what is "activation of a proto-oncogene"? is this a dominant or recessive process?
change in the proto-oncogene that converts it oncogene-like for tumorigenesis
-caused by gain in function mutations (translocation, amplification, point mutations), which changes its gene regulation, transcription, or PRO product
-this is dominant b/c only 1 mutation is required
what is CML caused by?
chronic myelogenous leukemia (relatively common form, mainly in older adults)
-first leukemia associated with cytogenetic marker t(9,22) proto-oncogene
-caused by juxtaposition of 2 genes that generates chimeric PRO product with a new function associated with disease
how was treatment for CML discovered?
delination of genetic abnormality led to better understanding of proto-oncogenes
-allowed development of new drug targeted to genetic lesion: Gleevec/imatinib BCR/ABL specific tyrosine kinase inhibitor
what is acute promyelocytic leukemia?
proto-oncogene related disease characterized by t(15,17) breaking PML gene on 15 and RARA (retinoic acid receptor alpha) gene on 17
how is APL diagnosed via FISH?
dual fusion probe shows that the translocation splits the probe recognition site so half of each probe is moved to reciprocal Xm
-normal will have no rearrangement, but if positive, there are 2 fusion signals
-NEED POSITIVE FISH in order to have diagnosis of APL
how does FISH aid in APL disease monitoring?
-if normal signal patterns return after treatment, the patient has responded to therapy (gone into remission)
-if fusion pattern returns, patient has relapsed
what is a tumor suppressor? how is activity lost? is it dominant or recessive?
genetic element whose loss or inactivation allows cell to display alternate phenotype leading to neoplastic growth
-oncogenetic potential when gene activity is lost (deletions, Xm gain/loss, gene mutation)
-recessive b/c needs both alleles mutated
what are the 2 major subgroups of tumor suppressors?
1. gate keepers: suppress tumors by regulating cell cycle or growth inhibition
2. caretakers: repair DNA damage and maintain genomic integrity
-effect is indirect - accumulation of errors in cells (just one loss of function may not be linked directly to disease)
what is the normal function of tumor suppressor genes, whose loss can lead to disease?
-regulation of growth inhibitory substances
what kinds of genes are RB1, p53, and MTS1?
they are all tumor suppressor genes
-RB1 on 13
-p53 on 17; one of most ubiquitous tumor suppressors
--mutations identified in nearly all types of cancer
-MTS1 on 9; multiple tumor suppressor 1
are solid tumors or leukemia/lymphomas more common in mutations of proto-oncogenes or tumor suppressors?
solid tumor - tumor suppressor mutation
leukemia/lymphoma - proto-oncogene mutation
what is an Rb1 mutation?
classic gatekeeper (tumor suppressor) mutation, commonly a mutation in Xm 13q14.2
-controls progression from G1 to S, so loss of function eliminates checkpoint causing uncontrolled growth
primary cancer: retinoblastoma
secondary cancer: osteosarcoma
what is a retinoblastoma?
tumor of retinoblasts (immature retinal cells) of eye
-1/20,000, from prenatal to 5 years old
-once retinoblasts mature to retinal cells at 5 years, the target tissue of disease is gone, and disease cannot occur
-can be unilateral (often sporadic) or bilateral (often inherited)
-if untreated, tumor can grow forward, out of the skull, and back into the brain (last is lethal)
--some can treat with laser surgery (leaves blind spot on retina), severe cases need enucleation
-can have secondary osteosarcoma in teens
inherited VS sporadic mechanism of tumor suppressor gene mutation
remember that tumor suppressor gene mutations are recessive; need 2 mutated alleles to see tumor
inherited: will have one mutated allele from affected parent
-patient will have 1 somatic (sporadic) mutation in order to have cancer
sporadic: patient is born normal, but along the way gets 2 different mutations
what is Knudson's "two-hit" hypothesis for retinoblastoma?
two mutations in the same cell are needed to start cancer
-sporadic usually unilateral
-inherited usually bilateral
-appearance of dominance, even though gene itself is recessive
somatic VS familial cancers in relation to age of onset
somatic - usually older age of onset (needs both sporadic mutations)
familial - usually younger onset (only needs 1 more mutation)
what is Li Fraumeni?
familial cancer syndrome with inheritance of p53 mutation
-p53 has no one target tissue and not specific to one disease, thus multiple neoplasia
-increased risk of cancer (50% at age 30, 90% at age 70)
what is the lifetime risk of breast cancer? mutations? is it familial or sporadic? what genes are associated with it?
1/8 to 1/10, can be familial or sporadic, with errors in homologous recombination or DNA repair defects
-2 known genes: BRCA1 (Xm 17, near NF1 and p53), BRCA2 (Xm 13, near Rb1)