Exam 3 Flashcards by Amani Lyons

Which of the following is NOT commonly present at high levels in senescent cells?

SV40 large T antigen

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The structures located at the ends of chromosomes for protection and for prevention of end-to-end fusion are known as

Telomeres

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Which of the following is MOST likely true of aggressively dividing cancer cells?

Their telomeres are stabilized (not shortening with each cellular division)

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Which of the following proteins is NOT part of the shelterin complex?

None of the above

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Proteins in the shelterin complex

TRF1
TRF2
POT1
TIN2

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Human cancer cells that lack telomerase activity may

be in crisis
have shorter telomeric repeat sequences
demonstrate the exchange of sequence information between telomeres through unequal crossing over
undergo chromosomal translocations

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Why does the loss of telomerase activity in human lead to severe phenotypes in the first generation, while loss of telomerase activity in laboratory mice takes several generations to exhibit any sort of phenotype?

Humans cells have shorter telomeres

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Breakage-fusion-bridge (BFB) cycles may help drive tumorigenesis by

Providing a means for cells to acquire additional mutations

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Which of the following is NOT a characteristic of aging cells?

Lengthening of telomeric DNA sequence

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Some cancers escape crisis by

Overexpressing hTERT
Activating the ALT mechanism

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Which of the following statements is TRUE?

Senescent cells are viable

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Patients with color cancer often exhibit loss of heterozygosity at specific chromosomal arms. These chromosomal regions most likely include genes that act as

Tumor suppressors

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Which of the following is characteristic of field cancerization

Multiple tumors in an organ are separated by normal tissue

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A cell representing an intermediate between stem cells and their differentiated descendants is known as

Transit-amplifying/progenitor cell

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The rate at which mutations occur in the cells within a tumor is most likely

More frequent than in normal cells of that tissue type
Affected by the genome instability within the tumor cells

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Which of the following types of mutations would NOT be advantageous for the survival of a cancer

An inactivating mutation in an oncogene

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In experiments in which rat embryo fibroblasts were transfected with suspected oncogenes, introduction of which of the following transformed the cells?

Both Myc and H-Ras together

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When experimental mice are treated with DMBA and TPA to induce the formation of papillomas, TPA

-Serves as the promoting agent
-Must be administered multiples times in order for papillomas to form

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Which of the following statements is FALSE?

Use of NSAIDs has been associated with increased mortality from rectal cancer

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The ability of cells to form a tumor is usually

The result of multiple mutations
Influenced by chemicals that are non mutagenic but act as promoters

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Which of the following is true of “complete carcinogens”

They are capable of initiating tumorigeneisis
They promote tumorigenesis
They can induce tumor formation in lab animals on their own without the application of additional chemicals

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A patient with chronic myelogenous leukemia (CML) exhibits chromosomal translocations in both lymphocytes and myeloid cells. This suggests that the cell in which the initiating mutation occurred are MOST likely

A hematopoietic stem cell

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The DNA polymerase pol-delta

-Is involved in DNA synthesis
-Is involved in proofreading newly synthesized DNA
-Exhibits exonuclease activity

Which of the following may result in point mutations that can contribute to cancer?

-Deamination of 5-methylcytosine
-Unrepaired single-strand breaks during DNA synthesis
-Misincorporation of bases by DNA polymerase
-Exposure to UV radiation

The chemical structure formed from the reaction of a DNA base with a carcinogen is called

An adduct

Defects in which of the following cellular processes may contribute to an increased incidence of cancer?

-Nucleotide-excision repair -Mismatch repair -Base-excision repair

Which of the following is true of the BRCA1 gene?

-Its product normally functions in DNA repair -Germ-line mutations in this gene are associated with an increased risk for breast and ovarian cancers -Somatic mutations in this gene are associated with an increased risk for ovarian cancer

Which of the following may result in loss of function of a tumor suppressor gene?

-Nondisjunction of sister chromatids -Failure of a chromatid containing a tumor suppressor gene to attach to a spindle fiber during cell division -Hypermethylation of the promoter of the gene

Which of the following types of cells are most protected from genomic damage?

Stem cells

Which of the following types of mutations are advantageous to cancer cell growth?

-Those resulting in defective mismatch repair -Inherited defects in double-strand DNA repair -A defect in nucleotide-excision repair

Which of the following mechanisms is involved in double-strand DNA repair?

-Homology-dependent repair -Nonhomologous end joining

Which of the following is true of Hodgkin's lymphoma?

-The neoplastic cells within Hodgkin''s lymphoma tumors are known as Reed-Sternberg cells -Many normal lymphocytes are recruited to the site of neoplastic cells within patients who have this disease

Stromal cells formed within various types of cancerous tumors include

-Fibroblasts -Lymphocytes -Macrophages

Heterotypic signaling between different cells types in a tumor often involves the activities of

-Trophic factors favoring cell survival -Growth-inhibitory signals -Mitogenic growth factors

VEGF is involved in

-Monocytic migration -Hematopoiesis -Capillary Permeability -Angiogenesis

Which is TRUE about matrix metalloproteinases

-MMP-9 is released by inflammatory cells -MMP-9 activates previously latent VEGF by cleaving ECM components -MMP-9 activity is critical for tripping the angiogenic switch -MMPs help reinforce expression of the EMT program in epithelial cells via degradation of E-cadherin

Colony-stimulating factor-1 (CSF-1)

Stimulates the differentiation of monocytes to macrophages

The distance that oxygen can diffuse through living tissue is approximately

0.2 mm

Blood vessels within tumors are

-Often constructed in a haphazard, seemingly disorganized fashion -May stop abruptly in dead-end pouches or circle back on themselves

Which of the following is an inhibitor of angiogenesis

-angiostatin -thrombospondin-1

Angiogenesis inhibitors are an attractive anti-cancer agent because

They target the normal cells rather than the ever-mutating cancer cells

Provide TWO observations that would support the Darwinian theory for the evolution of cancer cells

1. Cells of the SAME TYPE isolated from a tumor are all found to have multiple IDENTICAL MUTATIONS 2. Cells isolated from a tumor are all found to have an inactivating mutation in a gene that is normally pro-apoptotic

The RATE at which mutations occur in the cells within a tumor is most likely

1. More frequent than in normal cells of that tissue type 2. Affect by genome instability within the tumor cells

Provide THREE types of mutations that would be advantageous for the survival of cancer cells

1. An inactivating mutation in a tumor suppressor gene 2. An inactivating mutation in a gene that promotes apoptosis 3. Methlylation of the promoter of a tumor suppressor gene

Transformation of some types of human cells has been achieved through insertion of cloned genes coding for

- Oncogenic H-Ras -SV40 early region -hTERT

When experiemental mice are treated with DMBA and TPA to induce the formation of papillomas, TPA

-Serves as the promoting agent -Must be administered multiple times in order for papillomas to form

______ are often detected in tumor samples

Inflammatory cells

Cancer often arises at sites of ____

Chronic inflammation

The _____ has been shown to have direct transforming properties

Inflammatory cytokine TNF

Levels of _______ in tumors have negatively correlated with patient prognosis

Macrophage Infiltration

FOUR examples thought to have tumor-promoting characteristics

1. Helicobacter pylori 2. Estrogen 3. Testosterone 4. Hepatitis B Virus

The ability of cells to form a tumor is usually the result of

Multiple mutations

The ability of cells to form a tumor is usually influenced by

Chemicals that are NON-mutagenic but act as promoters

Which of the following statements about cancer is false?

A mutation in even a single cancer-critical gene is sufficient to convert a normal cell into a cancer cell

Tumor Initiators

Mutagens that predispose cells to develop tumors

Tumor Promoters

Non-reactive compounds that stimulate tumor development