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POD > Tumour Pathology 4 > Flashcards

Tumour Pathology 4 Flashcards

1
Q

What do disorders of cell growth include?

A
  • Normal and abnormal cell cycles
  • Chemical carcinogenesis
  • Radiation carcinogenesis
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2
Q

What is mitosis?

A

The mechanism of cellular replication and involves nuclear division plus cytokinesis

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3
Q

What does mitotic division generate?

A

Two genetically identical daughter cells

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4
Q

What is the cell cycle?

A

The time interval between mitotic divisions

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5
Q

What are the phases of the cell cycle?

A
  • G1
  • S
  • GS
  • M
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6
Q

What is tightly controlled during mitosis?

A

Production of cell numbers and cell types

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7
Q

What must a cell do to produce viable progeny?

A

Progress through cycle phase in the correct sequence

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8
Q

What must occur sequentially/

A

DNA synthesis and mitosis

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9
Q

What is ensured during quality control of cells?

A
  • Genetic fidelity in daughter cells
  • Each cell must receive a full chromosome complement
  • Mutations in DNA sequence must not pass on
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10
Q

What are the external factors in cell cycle control?

A
  • Hormones
  • Growth factors
  • Cytokines
  • Stroma
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11
Q

What are the intrinsic factors in cell cycle control?

A

Critical checkpoints including restriction point (R)

  • Prior to R, progress through G1 depends on external stimuli
  • After R progression becomes autonomous
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12
Q

Cell cycle checkpoints: If cell size inadequate…

A

G1 or G2 arrest

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13
Q

Cell cycle checkpoints: If nutrient supply inadequate…

A

G1 arrest

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14
Q

Cell cycle checkpoints: Essential external stimulus lacking…

A

G1 arrest

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15
Q

Cell cycle checkpoints: If DNA is not replicated

A

S arrest

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16
Q

Cell cycle checkpoints: If DNA damage is detected

A

G1 or G2 arrest

17
Q

Cell cycle checkpoints: Chromosome mis-alignment

A

M-phase arrest

18
Q

What are checkpoints?

A

A system of cyclically active and inactive enzymes

19
Q

How are checkpoints activated?

A

Catalytic sub-unit activated by regulatory sub-unit

20
Q

What are the sub-units called?

A
  • Catalytic sub-units are called cyclin-dependent kinases (CDKs)
  • Regulatory sub-units are called cyclins
  • The active enzyme complex= CDK/cyclin complex
21
Q

How CDKs work?

A
  • Different CDKs and cyclins operate at sequential stages of the cycle
  • Active CDK/cyclin complexes phosphorylate target proteins
  • Phosphorylation results in activation/inactivation of tat substrate
  • Substrates regulate events in the next cycle phase
22
Q

How is CDK activity regulated?

A
  • CDKs are constitutively expressed in an inactive form
  • Cyclins accumulate and are destroyed as cycle progresses
  • Regulation is exerted by CDK inhibitors (CKIs)
23
Q

What examples of CKIs are there?

A
  • INK4A family bind to CDK4 and 6 and prevent association of these CDKs with their cyclin regulatory proteins (p16INK41) (p15ink4B) (p18INK4C)(p19INK4D)
  • Second family of CKIs- CIP/KIP family p21CIP1
  • These inhibitor molecules bind to cyclin/CDK complexes
24
Q

Describe how the retinoblastoma gene works.

A

-Encodes a 110 kDa phosphoprotein (pRb) expressed in almost every cell of the human body
-pRb is hypophosphorylated
-Phosphorylation increases as cells progress through the cell cycle
Active cyclin D/CDK complexes phosphorylate pRb

25
Q

What is the most important target of pRb?

A

E2F transcription factor

26
Q

How does pRb interact with E2F?

A
  • Hypophosphorylated/active Rb inactivates E2F
  • Phosphorylated inactive pRb loses affinity for E2F
  • Free E2F transcription factor activates vital target genes
27
Q

What is E2F?

A

A potent stimulator of cell cycle entry

28
Q

What is carcinogenesis caused by?

A

Mutation of genetic material that upsets the normal balance between proliferation and apoptosis. Uncontrolled proliferation of cells leads to tumours

29
Q

What will cause a cell to lose control of proliferation?

A

Mutations in genes regulating cell division, apoptosis and DNA repair

30
Q

What happens in chemical carcinogenesis?

A
  • Purine and pyrimidine bases in DNA are critically damaged by various oxidizing and alkylating agents
  • Chemical carcinogens or their active metabolites react with DNA forming covalently bound products (DNA adducts)
  • Adduct formation at particular chromosome sites causes cancer
31
Q

What are critical cellular targets for radiation damage?

A

Purine and pyrimidine bases

32
Q

What types of radiation are carcinogenic in high doses?

A
  • UV
  • X-rays
  • Gamma radiation
33
Q

What is the primary defect in cancer?

A

Uncontrolled cell proliferation via cell cycle dysregulation

34
Q

What are 2 regulatory pathways often disrupted in cancer?

A
  • The cyclin D-pRb-E2F pathway

- p53 pathway

35
Q

Where are most cancers dysregulated?

A

G1-S because mutation in

  • Rb
  • CDK4
  • Cyclin D
  • p16
36
Q

What is the function of p53?

A

-Maintains genomic integrity

37
Q

What happens when p53 levels increase in damaged cells?

A
  • Induces cell cycle arrest at G1
  • Facilitates DNA repair
  • If damage is severe: p53 induced apoptosis
38
Q

What happens to cells with mutated p53?

A
  • Cells with mutated p53 do not G1 arrest or repair damaged DNA
  • Genetically damaged cells proliferate and form malignant neoplasms

POD (54 decks)

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