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HemeOnc Block > Biochem Heme/Onc 1 > Flashcards

Biochem Heme/Onc 1 Flashcards

1
Q

What are the precursors to nucleotide synthesis via de novo pathway?

A

ribose 5-P

amino acids

CO2

formate

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2
Q

What are 3 pyrimidines?

A

CTP, UTP, TTP

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3
Q

What are two purines?

A

ATP, GTP

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4
Q

In the first part of pyrimidine syntheis, carbamoyl phosphate is formed in the cytosol from what?

A

glutamine, CO2, and 2 ATP

from glutamine by carbamoyl phosphate synthetase II

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5
Q

A block in the urea cycle can cause a build up of what? What will happen because of this?

A

can cause a build up carbamoyl phosphate

increased production of pyrimidine biosynthesis will occur

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6
Q

A build up of what acid makes us think there is a problem in the urea cycle?

A

orotic acid

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7
Q

How many enzymes are used in pyrimidine syntheis? What two enzymes are linked (one enzyme with two active sites)?

A

6 enzymes

enzymes 2 and 3 are linked

enzymes 5 and 6 are linked

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8
Q

In pyrimidine synthesis, the ring is assembled first, then it is linked to _________________ to form the pyrimidine nucleotide. This comes from…

A

ribose phosphate

from PRPP

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9
Q

What is the first enzyme used in pyrimidine synthesis?

A

carbamoyl phosphate synthetase II

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10
Q

enzymes 2 and 3 in pyrimidine synthesis are linked. What are they?

A

aspartate transcarbamoylase

dihydroorotase

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11
Q

What enzyme is located in the mitochondria that participates in pyrimidine synthesis?

A

dihydroorotate dehydrogenase

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12
Q

Enzymes 5 and 6 of pyrimidine synthesis are linked. What are they?

A

orotate phosphoribosyl transferase

orotidylate decarboxylase

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13
Q

CPS I is involved in what cycle and where is it located?

A

urea cycle, located in the mitochondria

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14
Q

What is the committed step in pyrimidine biosynthesis?

A

formation of N-carbamoylaspartate, by enzyme aspartate transcarbamoylase

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15
Q

Once we have UTP, we can add ___________ to make CTP. This is from ___________.

A

nitrogen

glutamine

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16
Q

Control of pyrimidine biosynthesis is accomplished through…

A

feedback inhibition of enzymes in the de novo synthesis

UMP and CMP will build up and inhibit step 6 (OMP to UMP)

UTP and CTP will build up and inhibit step 1 (making of carbamoyl phosphate)

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17
Q

The purine ring is synthesized de novo from…

A

ribose -P

amino acids

CO2

formate

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18
Q

Ribose-5-phosphate from the ________________ is converted by PRPP by the enzymes _________________.

A

pentose phosphate pathway

PRPP synthase

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19
Q

The first stage of purine biosynthesis begins with the conversion of PRPP to ___________________ by the enzyme _______________. This is the comitted step toward purine biosynthesis.

A

5-phosphoribosyl-1-amine

PRPP aminotransferase

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20
Q

What are the 6 key points on purine synthesis?

A
  1. requires ATP
  2. 10 enzyme activities involved
  3. glutamine and aspartate are sources of nitrogen
  4. glycine is required
  5. formyl THF is required (2)
  6. CO2 is required
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21
Q

PRPP undergoes 10 steps to get to ________________. From here it can make all other purine nucleotides.

A

IMP (inosine monophosphate)

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22
Q

How does IMP make GMP?

A

IMP dehydrogenase –> Xanthosine 5’ monophosphate => glutamine adds nitrogen => GMP

need ATP to make GMP

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23
Q

How does IMP make AMP?

A

IMP + aspartate’s nitrogen => split off fumarate => AMP

need GTP to make AMP

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24
Q

What controls purine synthesis?

A

Feeback inhibition

AMP, GMP, and IMP can inhibit steps from initial steps of synthesis of PRPP

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25
Q

What is the committed step of purine nucleotides?

A

conversion of PRPP to phosphoribosylamine

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26
Q

What inhibits PRPP aminotransferase?

A

purine ribonucleotides

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27
Q

How do we make deoxyribonucleotides?

A

ribonucleotides with VIP enzyme: Ribonucleotide reductase

reduction of 2’ -OH of ribose moiety

substrates for theses reactions are ribonucleotide diphosphates

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28
Q

ribonucleotide reductase requires what reducing equivalents from NADPH? How does this make deoxyribonucleotides?

A

thioredoxin reductase reduces NADPH, creating reduced thioredoxin which RNR can use to create deoxyribonucleotides

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29
Q

Ribonucleoside diphosphate reductase is finely tuned by __________________.

Binding of ATP to overall activity site __________ the enzyme system, binding of dATP _______________ the enzyme. Under physiological conditions, there is always one bound.

A

allosteric control

activates

inactivates

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30
Q

What determines the Km and Vmax of the substrate binding sites with RNR?

A

substrate specificity sites

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31
Q

Binding of ATP in the substrate specificity site (with RNR) favors…

A

reduction of UDP and CDP (pyrimidine reductions)

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32
Q

With regard to RNR control, binding of dTTP favors _______ reduction and binding of dGTP favors _______ reduction.

A

GDP

ADP

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33
Q

What are the subunits of ribonucleotide reductase?

A

2 subunits - large regulatory and small subunit;

catalytic site is between the two

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34
Q

What accessory proteins and enzymes are required for RNRase to be activated?

A

NADPH funneled through ETC

Thioredoxin reductase

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35
Q

What does thymidylate synthetase do?

A

key enzyme for DNA synthesis

dUMP converted to dTMP by methyl group donated from methylene tetrahydrofolate

enzyme makes this happen

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36
Q

if dUTP is high in the cell, we want it to methylate so as not to incorporate ________ into DNA

A

uracil

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37
Q

What replenishes tetrahydrofolate after it donated its methyl group to be used with thymidylate synthetase?

A

dihydrofolate reductase

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38
Q

What are two potential sites around DNA synthesis that could be targets for anti-cancer drugs? What would they be inhibiting?

A
  • inhibition of thymidylate synthetase: specifically inhibit DNA replication within the cell
  • inhibition of tetrahydrofolate generation: within the cell, will also inhibit thymidylate synthetase
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39
Q

What binds to 5’ fluorodeoxyuridylate forming a suicide inhibitor? What is it dying to inhibit?

A

5-fluorouracil binds to enzyme

inhibits thymidylate synthetase

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40
Q

What blocks dihydrofolate reductase, preventing regeneration of tetrahydrofolate?

A

aminopterin and amethopterin (methotrexate)

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41
Q

Purines are being broken down into…

Adenine gets broken down to… by…

Guanine gets broken down to… by…

A

uric acid

hypoxanthine by adenine deaminase

xanthine by guanine deaminase

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42
Q

What is a flavoprotein containing iron, and generate H2O2 from oxygen? What is its role in the body?

A

Xanthine Oxidase

converts xanthine and hypoxanthine to uric acid for excretion

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43
Q

In pyrimidine catabolism, uracil is converted to ____________ and thymine is converted to _________________ and they are both excreted.

A

beta-alanine

beta-aminoisobutyrate

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44
Q

What does orotic aciduria disease cause? What are signs and symptoms of it? What are the enzymes being blocked generally?

A

blocked biosynthesis of pyrimidines

early failure to thrive around 3 mo, anemia, crystals in urine (orotic acid)

block in urea cycle enzymes like orithine transcarbamoylase, orotate phosphoybosyl transferase, and orotate decarboxylase (mainly ORPT and ODC)

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45
Q

What is the treatment for orotic aciduria?

A

oral uridine bypasses block in UMP synthesis, replacing missing product uridylate

oral uridine lowers orotic acid excretion significantly by inhibition of CPS II by UTP

less PRPP is formed, which decreases activation of CPS II

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46
Q

What are four characteristics of Lesch-Nyhan Syndrome?

A
  1. neuro dysfunction
  2. cognitive delays and self-mutilation
  3. uric acid overproduction
  4. X linked recessive
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47
Q

What is the biochemistry behidn Lesch-Nyhan syndrome?

A

lack of HGPRT, hypoxanthine-guanine phosphoribosyltransferase, a purine salvage enzyme

relation between HPRT and hyperuricemia

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48
Q

The most severe forms of Lesch-Nyhan Syndrome include…. while the more mole syndromes would only have….

A

self-mutilation

milder only have hyperuricemia and gouty arthritis associations

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49
Q

Lesch-Nyhan syndrome may be a _________ deficiency, according to mice studies.

A

dopamine

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50
Q

clinical symptoms of urate salts deposited into tissues. This is a disease of altered _________ metabolism

A

gout

purine

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51
Q

What are three potenital, infrequent causes of gout?

A

HGPRT deficiency

glucose-6-phosphatase

PRPP synthetase increase

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52
Q

Why do most pts develop gout?

A

decreased urate clearance

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53
Q

How can you diagnose gout?

A

NOT solely on urate levels. One of the following three criteria must be met.

  1. urate crystals in WBCs from acutely inflamed joint
  2. urate crystals in biopsy of tophus
  3. combo of: a)hx of acute monoarticular arthritis, followed by periods free of ssx, b) rapid and complete response to colchicine c) presence of hyperuricemia
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54
Q

How would you tx gout?

A

restrict purines in diet

promote excretion with uricosuric agents - probenecid and sulfinpyrazole

inhibit urate synthesis with allopurinol - XOase inhibitor

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55
Q

If you discontinue allopurinol, what could be an issue?

A

must maintain allopurinol tx for life; interrupted tx can cause rebound and more acute attacks along with urate nephropathy

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56
Q

What does presentation of heritable immunodeficiency look like?

A

infants less than 6 mo present with recurrent and multiple infections of the skin, GIT, and resp. tract.

SCID

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57
Q

What two SCIDs include enzymes involved in creating hypoxanthine??

A

ADA - adenosine deaminase

PNP - purine nucleoside phosphorylase

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58
Q

What contains the highest concentrations of ADA and PNP in the body? What does that imply?

A

lymphocytes and thymus

purine salvage pathway is important here

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59
Q

In ADA and PNP deficient pts, what nucleosides are increased in serum?

A

adenosine

deoxyadenosine

inosine

guanosine

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60
Q

What are the two alternative pathways for Adenosine and deoxyadenosine if pt is ADA deficient? What is the result of this in the cell?

A

can be phosphorylated to AMP or dAMP

adenosine can be condensed with homocysteine to be S-adenosylhomocysteine

results in increased dATP and S-adenosylhomocysteine levels

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61
Q

What will happen to RNRase when dATP increases?

A

inhibits RNRase, targeting WBCs can’t proliferate - toxic to B and T cells

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62
Q

With increased S-adenoxylhomocysteine levels, what will happen?

A

secondary effect, inhibition of methylation reactions

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63
Q

With PNP heritable immunodeficiency, what will happen at an intracellular level?

A

Inosine and deoxyinosine levels with rise along with guanosine and deoxyguanosine levels

this causes increase in dGTP

inhibits RNRase from functioning correctly

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64
Q

ADA deficiency causes a __________ in ATP levels and __________ in dATP levels resulting in…

A

decrease

increase

inhibition of RNRase from working correctly

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65
Q

How would you tx ADA deficiency?

A

transfusion - temporary

identical BMT

haplo-identical BMT

PEG-ADA replacement therapy

gene therapy poster child

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66
Q

What proteins are associated with HIV infection of CD4 T cells?

A
  • surface protein of HIV is glycoprotein (gp120) which connects to an integral viral membrane protein gp41
  • gp 120 binds to a surface protein on T4 cells - CD4 and chemokine receptor CCR5 or CXCR4
  • gp41 pierces the membrane of target cell and mediates virus fusion
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67
Q

After HIV has fused to its target cell, how does the virus replicate?

A
  • core of the virus enters cell and viral genome is copie into DNA
  • integrated into host cell DNA
  • after being dormant, viral DNA can be rapidly reactivated
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68
Q

What causes lysis of CD4 cells with HIV infection?

A

when replicated virus leaves the host cell, they can lyse the cell

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69
Q

What is a synctium with HIV infected cells? What is the clinical importance of this phenomenon?

A
  • infected cell binds with CD4 of uninfected cells
    • cells fuse and form large mass
  • synctium forming strains progress more rapidly to AIDS
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70
Q

How does the host immune system fight back against HIV infection?

A

Tc cells can destroy infected cells which display viral protein on their surfaces

coinfected cells which acquire gp120 on surfaces can be destroyed

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71
Q

What is the major viral surface protein and immunodeterminate of HIV?

A

gp120

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72
Q

What does the composition of HIV consist of?

A
  • 2 strands RNA
  • envelope proteins
    • gp120
    • gp41
  • inner membrane protein P17
    • attached to inner surface of the viral envelope via FA acetylation
    • core proteins p24, p7, p9 which form bullet-shaped inner core
  • enzymes
    • reverse transcriptase
    • integrase
    • protease
  • lipids of T4 lymphocytes plasma membrane
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73
Q

What do the enzymes a/w HIV do or consist of?

A
  • reverse transcriptase
    • consist of DNA polymerase and an RNase H activity
  • integrase
    • enzyme which assists in inserting the viral DNA into the host genome
  • protease
    • proteolytic enzyme which cuts the virus’ proteins out of a long polypeptide
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74
Q

What is required for integration of HIV into CD4 T cells? What process requires integration?

A

activation of T cell

transcription

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75
Q

What are the steps in viral assembly?

A
  • transcription of viral DNA into viral RNA is activated
  • precursor proteins are formed with FA acylated at an end and inserted into the host membrane
  • protease turns on and cuts
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76
Q

The course of HIV infections is ___________. Virus is constantly being produced in _______________.

A

progressive

lymphoid organs

77
Q

In the genome of HIV, what are the structural genes and what do they code for?

A
  • GAG - codes for core proteins
  • POL - enzymes
  • ENV - envelope protein
78
Q

What are three regulatory genes of HIV and what do they code for?

A
  • TAT - transactivator - potent stimulator of viral protein replication
  • REV - regulator of virion protein expression - exerts positive and negative control (allows varying amounts of regulatory or structural proteins to be made)
  • NEF - positive virulence factor
79
Q

What does TAT bind to in order to carry out transactivation?

A

HIV mRNA 5’ end TAR region

hairpin part

80
Q

TAT protein itself can impair T cell replication… how does this happen?

A

TAT released from infected CD4 T cells and with unknown toxic mechanism, can inhibit proliferation of uninfected T cells

81
Q

What is the MOA of the REV gene?

A
  • controls the extent to which viral mRNAs are spliced and exported from nucleus
  • action of REV is posttranscriptional
  • REV binds to splicing sites and prevents splice reactions
82
Q

What and where does the NEF gene do and work?

A
  • increases infectivity
  • NEF protein sequence found near the end of the viral genome in long terminal repeat
  • site of action: found in the cytosol and is thought to mediate its effects through kinases
  • Nef down regulates CD4 receptor level by stimulating internalization of receptor
    • prevents super infection of the cell, which is toxic
83
Q

What accounts for the high genetic variability of HIV?

A
  • mutations
    • viral DNA polymerase lacks error correcting features like other DNA polymerases
    • cellular RNA polymerase also has no error correcting capabilities
84
Q

What are the consequences of mutations in HIV?

A
  • non-lethal mutations
    • most mutations in part of genome with little functional role
  • natural selection
    • drug resistant variants arise rapidly
85
Q

What are 5 potential targets of anti-HIV drugs?

A
  1. viral fusion
  2. integration
  3. reverse transcriptase
  4. TAT antagonists
  5. protease inhibitors
86
Q

How does AZT work?

A
  • can increase median survival time of pts with advanced AIDS by about 1 year
  • inhibits viral reverse transcriptase
    • AZT is recognized as thymine and is incorporated into DNA strand being made from RNA
    • no free OH group causes the chain elongation to stop at this point and DNA synthesis is aborted
87
Q

AZT is particularly toxic to what?

A

Bone marrow cells

AZT is about 100x less inhibitory to DNA polymerase alpha than HIV RT

88
Q

What are some direct inhibitors of HIV fusion?

A

mutations in chemokine receptors, esp. CXCR4

89
Q

How do protease inhibitors of HIV work?

A

saquinavir, viral protease inhibitor blocks cleavage of large polyprotein, stopping viability

90
Q

What is cART?

A

combined anti-retroviral therapy

two RT inhibitors (AZT, ddI) and protease inhibitor (saquinavir)

v. important to be combined to tx HIV

91
Q

Why is there not an effective vaccine for HIV yet?

A

best vaccines are for acute diseases where the host is able to present an adequate immune response

variability of HIV prevents ab production by host, unable to prevent infection

tested HIV vaccines fail to protect against field isolates of the virus

92
Q

What are the challenges to creating an AIDS vaccine?

A

must maintain potent humoral response and induce strong CTL response to be effective

low antigenicity of envelope proteins

protein subunit vaccines cause weak CTL response

adequate viral control requires Ab and CTL response

mucosal route of viral entry is problem

93
Q

HIV is not transmitted by…

A

misquito bites

94
Q

HIV associated wasting is diagnosed in pts who…

A

unintentionally lose 5% of body weight within 3 months, 7.5% within 6 mo, or 10% in 12 mo

95
Q

What are some causes a pt with HIV might have reduced food intake?

A

oral infections - candidiasis, HSV, Kaposi’s sarcoma

medications causing anorexia, N/V/D, food aversions

respiratory disorders with symptoms interfering with eating

emotional distress, pain, and fatigue

96
Q

What are GI and complications related to fat accumulation in HIV?

A

GI infections attributed to opportunistic infections, medications

lipodystrophy/lipoatrophy: buffalo humps, lipomas, altered blood lipid levels

97
Q

A low fat, nondairy diet may be good for pts displaying what symptoms?

A

hypertriglyceridemia

elevated LDL

insulin resistance

hyperinsulinemia

98
Q

What besides physical or emotional ailments could contribute to poor nutrition while living with HIV?

A

economic - ability to earn, loss of assests, loss of social networks

environmental - famine, socio-political events

99
Q

How can you control anorexia and wasting in an HIV pt?

A

anabolic hormones, appetite stimulants, and regular physical activity

100
Q

How can you control lipodystrophy in an HIV pt?

A

aerobic activity and resistance training to reduce abdominal fat

medication to tx abnl blood lipid levels and insulin resistance

101
Q

Alternative therapies can be helpful or harmful in tryign to maintain weight in a pt with HIV. What are some reasons to monitor dietary supplements?

A

reduce likelihood of adverse effects or diet-drug interactions

St. Johns wart or garlic may reduce the effectiveness of some antiretroviral drugs

zinc megadoses may increase the progression of HIV infection

102
Q

Appetite stimulants may _________ the effects of alcohol.

A

increase

103
Q

Methotrexate may cause reduced __________ absorption. So you should probably have pt on a supplement.

A

folate

104
Q

Zidovudine should not be taken with a high-fat meal which would decrease drug absorption. It also increases the risk of…

A

insulin resistance, diabetes

105
Q

How much should an HIV pt increase their calorie consumption?

A

10-15% more calories/day required by HIV infected individuals

106
Q

What are the major things HIV pts should avoid consuming in order to avoid metabolic issues?

A

limit intake of trans fats, cholesterol, added sugars, and alcohol

107
Q

What is a pathogen that should be considered for an HIV pt who is dealing with water from different sources?

A

cryptosporidiosis

diarrheal disease caused by parasites

108
Q

What is considered the last stage of nutritional support for an HIV pt?

A

parenteral nutrition

109
Q

What two abilities are common to all cancers?

A
  • divide and reproduce in an unrestrained fashion
  • invade and colonize other tissues
110
Q

If neoplasms express only the ability to have unrestrained growth, they are considered…

A

benign

111
Q

Carcinomas arise from _____________ while sarcomas arise from_______________.

A

epithelial tissue

connective tissue, muscle or vasculature

112
Q

Most cancers (80% even) are…

A

epithelial cancer

113
Q

Evidence for the monoclonal origin of cancer involves the phenomenon known as X-inactivation. What is all this about?

A

Generally, cells in a woman’s body has either paternal or maternal X chromosome inactivated. This leaves half the cells to be one or the other, mixed throughout the body.

Tumors contains all cells which have inactivated paternal X or all cells which have inactivated maternal X. If tumors arose from many cells at once, they too would have a mix throughout.

114
Q

What is the multiple hit hypothesis?

A

multi-stage carcinogenesis contends that more than one genetic change is needed to cause cancer; these multiple hits must occur in a single cell

115
Q

Chimney sweep occupation leads to cancer because of …. present in soot

A

polycyclicaromatic hydrocarbons present that cause mutations in DNA when “activated”

116
Q

What is the MC mutagenicity test?

A

Ames test

incubate suspect chemical with bacteria

plate without histidine

see where histidine grows

117
Q

Why is inclusion of the liver homogenate in the assay important for the Ames test?

A

some chemicals require metabolic activation by a mammalian enzyme before they serve as mutagens or genotoxic agents

118
Q

Metabolic activation of some carcinogens occur through what? What ultimately is this doing?

A

cytochrome P450s

catalyze reactions to make molecules more hydrophilic and prep for excretion through the urine

119
Q

How could metabolic activation of some carcinogens back fire on the body trying to get rid of them?

A

can actually make them more carcinogenic by generating highly reactive electrophilic groups which will attack the electron-rich portions of macromolecules (esp nitrogen bases of DNA)

120
Q

What is the difference between an indirect carcinogen and direct carcinogen?

A

indirect carcinogen - metabolic activation is required to create a mutagenic and carcinogenic substance

direct carcinogen - substance is genotoxic and modifies DNA without any metabolic alternation to themselves

121
Q

What two things are really required in cell genetics in order for cancer to precipitate?

A

initiation - one or several mutations

promotion - non-mutagenic but promote growth of initiated cells; increases the number of initiated cells and perhaps increasing the further mutation frequency of treated cells

122
Q

Dealing with initators and promoters… cancer ensues only if…

A

the exposure to the promoter follows exposure to the initiator and only if the exposure of teh promter exceeds a certain threshold

or repeated exposure to the initiator alone

123
Q

The best-understood tumor promoters are the _____________. What do these include and how do they work?

A

phorbol esters

include TPA

bind to a specific receptor which turns out to be protein kinase C – mimics the action of diacylglycerol binding and thus stimulates inapproprate signal transduction via protein phosphorylation

124
Q

What is the hallmark of a promoter?

A

can be any agent (chemical or physical) which stimulates cellular proliferation

125
Q

Cancers have hyperactive signal transduction (particularly ____________) driven by…

A

tyrosine kinases

oncogenes

126
Q

Cancers switch from paracrine to __________ growth factor signaling

A

autocrine

127
Q

What virus is associated with Burkitts lymphoma?

A

EBV

128
Q

What is the oncogene theory of cancer?

A
  1. tumor viruses contain oncogenes that can directly transform cells
  2. oncogenes produce oncoproteins which disturb normal cell growth mech
  3. viral oncogenes are derived from normal cell proto-oncogenes
  4. normal cell proto-oncogenes can be converted to oncogenes without involvement of tumor virus
129
Q

What three ways can proto-oncogenes become activated toward oncogenesis?

A

deletion or point mutation in coding sequence

gene amplification

chromosome rearrangement

130
Q

What is the classic example of involvement of chromosomal translocation with myelogenous leukemia?

A

Philadelphia chromosome

bcr from chromosome 22 and abl from chromosome 9

bcr-abl point

131
Q

What drug is being used in attempt to tx chronic myelogenous leukemia by targeting the bcr-abl fusion kinase?

A

Gleevec

132
Q

Burkitts lymphoma is also caused by a chromosomal rearrangement involving different chromosomes and a oncogene —

A

myc and H-chain enhancer

133
Q

What two ways are there to block specific amplified signaling pathways?

A

monoclonal abs that block receptor function

tyrosine kinase inhibitors selective for EGFR

134
Q

What are the four classes of oncogenes?

A

growth factor receptors (c-erbB, c-fms)

protein kinases (c-src, c-fes)

GTP binding proteins (cH-ras, cNras, cKras)

nuclear proteins which act as transcription factors (c-myc, c-foc, c-jun)

135
Q

How do Ras oncogenes work?

A

three ras genes (H, K, N) found in eukaryotes

encode proteins that are synthesized in cytoplasm, modified by farnesylation, then attached to inner surface of the plasma membrane

show similarity to G protein, able to bind and hydrolyze GTP

modulate downstream effects which control cell proliferation

136
Q

What do farnesyltransferase inhibitors (FTIs) do?

A

prevent membrane attachment of Ras proteins

137
Q

What is Myc? What does it do? What disease is it found in?

A

a nuclear protein which acts like a transcription factor

contains a basic DNA binding region and a leucine zipper dimerization region

Myc expression is deranged in Burkitt’s lymphoma, small cell lung cancer, neuroblastoma, etc.

138
Q

What is c-Myc?

A

proto-oncogene crucial to cell proliferation

139
Q

What tumor suppressor gene is generally present in kidney and testis? Deletion of this lead to what disease?

A

WT1

Wilms tumor, childhood nephroblastoma

140
Q

Loss of Rb tumor suppressor can cause a loss of…

A

normal cell differentiation for most cell types

141
Q

Rb gene has been characterized as a DNA bidning protein since it contains…

A

zinc fingers

142
Q

p53 tumor suppressor gene is important in what 3 things?

A

DNA repair

growth arrest

apoptosis

143
Q

What is a major checkpoint in cells and is especially noted after cells are exposed to ionizing radiation?

A

p53

normally after radiation p53 levels increase in teh cell and result in cell arrest in G1 phase

144
Q

What is an inherited form of p53 mutation that makes the pt susceptible to wide variety of different cancers?

A

Li-Fraumeni

145
Q

Circulating tumor cells arrest where in the target organ by adherence or mechanical trapping?

A

precapillary venules

146
Q

Metastatic cell survival in circulation is actually very…

A

inefficient

147
Q

What is the three step hypothesis proposed for intravastation and extravastation?

A

tumor cell binding - to laminin, type IV collagen in basal lamina

proteolysis of ECM - digestion of basal lamina by type IV collagenase

migration of tumor cell - motility/actual movement

148
Q

What sequences do integrins recognize, found in fibronectin?

A

Arg-Gly-Asp (RGD)

149
Q

What is the main serine protease produced by tumor cells?

A

plasminogen activator, usually of urokinase type

150
Q

What are metalloproteinases and what do they do?

A

produced by tumor cells

type IV and V collagenases able to degrade basement membrane collagens

151
Q

What secretes cysteine proteases? What are they?

A

cathepsin B

lysosomal enzymes that become secreted in many cancer cell types

152
Q

The ____________ along with _____________ signal to src kinase, which in turn activates _________ and downstream ____________________ to form invadopodia which carry out ECM degradation.

A

integrins

tyrosine kinases

cortactin

actin assembly

153
Q

How are gene KO mice created?

A

embryonic stem cells

take out exon and replace with drug resistant gene

homologous recombination of mutant gene on a plasmid with the endogenous cellular gene leads to insertion of the mutated gene into the chromosome at the site of the endogenous gene

154
Q

Apoptosis is an ___________ pathway to cellular destruction which is latent, but can be…..

A

intrinsic

activated in all cell types

155
Q

Withdrawal of what from cells in culture can produce apoptosis?

What are some examples?

A

growth factors

NGF from neuroblasts and IL-2 from lymphocytic cell cultures

156
Q

What does the process of apoptosis involve?

A
  • nuclear chromatin condensation
  • plama membrane blebbing
  • fragmentation of the nucleus, accompanied by endonucleolytic cleavage of nuclear chromatin into a characteristic banding pattern
  • fragmented into small vesicles
  • loss of asymmetrical distribution of membrane lipids (signal for macrophage englufment of cellular remnants)
157
Q

What proteases are involved in the activation of apoptosis?

A

cysteine class – caspases-cysteine proteinases which cleave at aspartate residues

158
Q

What are the three classical pathways to apoptosis?

A
  1. withdrawal of growth factors (IL-2, NGF, etc) - results in release of cytochrome c from mito and activation of Apaf1 which activates caspases
  2. signaling through cell surface receptors such as Fas which activate caspases via adapter molecules (FADD) - death receptors
  3. DNA damage can activate p53 dependent pathway
159
Q

What is an anti-apoptotic gene?

A
  • Bcl-2
    • blocks apoptosis at final common pathway
    • anchored to membranes through its own hydrophobic carboxyl terminus
    • located in outer mito membrane, ER, and nuclear envelope
    • may form a pore in membranes, regulating signal/release of cytochrome c
160
Q

What can block Bcl-2?

A

death protein called bax by heterodimer formation

bax protein in excess of bcl-2 protein will signal cell death by removal of bcl-2 block of apoptosis

161
Q

What is both a transcriptional activator of bax gene while a transcriptional repressor of bcl-2 gene?

A

p53

162
Q

cancers which overproduce bcl-2 gene are….

A

resistent to cell killing by chemotherapeutic agents

163
Q

What is the bystander effect?

A

the idea that infected cells, then treated, can still cause the death of surrounding cells, despite them not having the same receptors/infection

164
Q

What is responsible for the bystander effect?

A

gap junctions created by the assembly of proteins called connexins that make up channels called connexons

allows passive exchange of molecules or ions, sufficient to allow exchange of toxic metabolites

165
Q

What is a major cause of multi-drug resistance due to?

A

product of mdr-1 gene which codes for P-glycoprotein

mdr-1 gene is sufficent to confer mdr to both cultured cells and animals by itself

p-glycoprotein is an intrinsic membrane transporter protein which utilizes ATP to cause the efflux of a wide variety of drugs from the cancer cell

166
Q

What does p-glycoprotein contain?

What is the most important determinant of the drugs transported by this system? How does this work?

A

12 transmembrane domains and 2 ATP binding site per monomer

relative hydrophobicity

works as a hydrophobic vacuum cleaner - drugs may never even enter the cell before p-glycoprotein interacts with the drug in the membrane and removes it

167
Q

What drug appars to block p-glycoprotein pump activity?

A

verapamil

168
Q

Angiogenesis is required for…

A

tumors to grow beyond 1 mm in diameter

169
Q

What are inducers of angiogenesis that may be overproduced in tumors?

A

VEGF (most important)

bFGF

170
Q

What are inhibitors of angiogenesis?

A

angiostatin

endostatin

interferons

host endothelial cells respond to inducers through receptors which activate not only proliferation but also infiltration and vessel formation with a tumor – hypoxia

171
Q

How does angiostatin work?

A

proteolytic fragments of plasminogen containing kringle domains 1-4 or 5 have activity (cleaved areas and released as angiostatin)

172
Q

What is a proteolytic fragment of collagen XVIII? How does it work?

A

endostatin

acts by inducing tumor endothelial cell death

173
Q

What is a naturally occuring inhibitor of angiogenesis?Where is it found?

A

nevoastat found in shark cartilage

blocks VEGF and metalloproteinase production

174
Q

What is the most common skin cancer in North America?

A

basal cell carcinoma

175
Q

characteristics of basal cell carcinoma include…

A

pearly lesion with telangiectasias

176
Q

What is a form of pre-malignant melanoma?

A

congenital nevi

177
Q

how is cachexia different from simple starvation?

A

it is hypermetabolism with loss of lean body mass

178
Q

How much more should CA pts eat vitamins and minerals

A

supplement 4-5x the normal RDA

179
Q

What form of food/nutrient intake is considered to have increased infections?

A

parenteral

180
Q

What are trials that alter one component of the diet versus a placebo?

A

prospective intervention trials

181
Q

How does dietary fat play a role in cancer?

A

high fat diets have promoter effect in tumorigenesis

increase in bile acids which act as tumor promoters

increased prostaglandin synthesis that can stimulate tumor cell proliferation

omega-3 fatty acids may be antagonistic

182
Q

What are the effects of fiber on colon cancer formation?

A

butyrate formation from fermentation of fiber polysaccharides

bile acid binding

bulk formation, decreasing transit time in digestive tract, limiting exposure to carcinogenic components of the diet

183
Q

How do calcium supplements appear to affect colon cancer?

A

15-20% reduction of adenomas with calcium supplementation per DBPC trial

184
Q

Inhibition of polyamines by ________________ has been succesful when it is combined with Sulindac, an NSAID that exports polyamines.

A

Elfornithine

185
Q

Myo-inositol has been shown to inhibit cancer formation in animals by acting through what potentially?

A

may act through cellular calcium levels

186
Q

How would NSAIDs decrease the incidence of colorectal cancer?

A

inhibition of COX enzymes (elevated in adenomas), through inhibition of arachidonate metabolism

187
Q

What substances in plants may act like NSAIDs and be a good route for looking at use preventing cancer?

A

phenolic compounds

188
Q

How do EGCG polyphenols in green tea work to combat cancer?

A

major anti-oxidant, induces apoptosis in multiple cancer types, interferes with cell-cell communication

189
Q

Most important dietary factor for prevention of lung cancer among smokers is consumption of diets containing…

A

high fruit and vegetable content

HemeOnc Block (4 decks)

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