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BIO 202 > Cancer Intro > Flashcards

Cancer Intro Flashcards

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1
Q

Cancer

A

A disease of uncontrolled cell division

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2
Q

Development and progression of Cancer is usually linked to…

A

Changes in the activities of cell cycle regulators

–> A loss of cell cycle control

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3
Q

Main molecular causes of Cancer (4):

A

1) Growth Factor Abnormalities
2) Signaling Machinery Defects
3) Improper Replication
4) Failure of Apoptosis

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4
Q

Growth Factor Abnormalities (Cancer) (2)

A

1) Make their own growth factors
2) Growth factor pathways are always ON

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5
Q

Genes for growth factors in normal cells are usually _______ and only _________ ____ when needed

–> How is this changed in cancer cells?

A

1) OFF
2) TURNED ON
–>These genes are usually selectively activated

–> In Cancer cells, mutations in these genes cause them to ALWAYS be ON = production of growth factors even when not needed
–> Don’t need the appropriate signal to activate the production of growth facotrs

Cancer cells don’t need a signal to activate the production of growth factors

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6
Q

Cancer cells may have abnormal signaling pathways that are…

A

ALWAYS ON (Constitutively active)

OR

that fail to convey growth factor signals (specifically STOP signals from a lack of the growth factor)

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7
Q

Some Cancer cells have been observed “tricking”…

A

neighboring cells into producing their own growth factors

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8
Q

Signaling Machinery Defects in Cancer cells

A

Have defects in cdks or other singaling machinery that ensures DNA replication and mitosis occur only under FAVORABLE conditions

–> Usually defects in machinery that STOPS cell division

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9
Q

What is the result of signaling machinery defects in Cancer cells?

A

Cells with continue to divide even under UNFAVORABLE conditions

–> They can’t stop themselves

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10
Q

Improper replication/division in Cancer Cells

A

IF and when Cancer cells do STOP dividing, they usually do so at random points (not at the regular checkpoints)

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11
Q

What is the result of improper replication/division in Cancer Cells?

A

Creates abnormal cells that have stopped dividing at random points in the cell cycle

–> Usually produces cells with severe deformities such as wrong # chromosomes

–> These cells will continue on to divide, proliferating the damage and abnormalities
Proliferation of damaged cells

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12
Q

Failure of apoptosis in Cancer Cells

A

Cancer cells typically fail to undergo apoptosis even under conditions in which normal cells would (ie. DNA damage)

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13
Q

Apoptosis in Normal vs Cancer Cells

A

Normal Cells –>
Unfixable DNA Damage = APOPTOSIS

Cancer Cells –>
Unfixable DNA Damage = Cells continue dividing

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14
Q

Main families of genes causing Cancer:

A

1) Oncogenes
2) Tumor Suppressors

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15
Q

Oncogenes

A

Genes that normally promote cell division (when not mutated)

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16
Q

What do oncogenes encode for?

A

1) Growth Factors
2) Growth Factor Receptors
3) Regulatory proteins of signaling pathways involved in cell division

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17
Q

Oncogene vs Proto-Oncogene

A

Oncogene = The over-active (Cancer promoting) form of these genes

Proto-Oncogene = The not-yet-mutated (normal) form

18
Q

First identified human oncogene

A

RAS

19
Q

RAS (gene)

A

A family of genes that encode for the G-Protein (GTPase), Ras

20
Q

Ras (protein)

A

A G-Protein (GTPase)

–> Relays a signal from a growth factor receptor (TK) to a cascade of protein kinases

21
Q

GTPase

A

A G-Protein that is active when bound to GTP

22
Q

Ras signaling pathway causes…

A

Upregulation of Cyclin D levels

23
Q

Cyclin D

A

Required for transition from G1 to S phase (G1 checkpoint)

24
Q

Ras Pathway Steps

A

1) Growth factor binds to a Tyrosine Kinase Receptor

2) The TK receptor auto-phosphorylates
–> 2.1) Ras-GDP (inactive form) gets activated to Ras-GTP

3) Active Ras initiates the phosphorylation cascade involving various protein kinases

4) Cascade leads into the nucleus where a transcription factor is activated

5) Leads to transcription of the gene encoding for Cyclin D production

6) Cyclin D is produced

7) Cell cycle is stimulated (pushed through G1 checkpoint)

25
Q

In Cancer, Ras protein is…

A

HYPERACTIVE

–> It’s always “ON” = Always in the GTP bound (active) form

26
Q

Due to Ras being hyperactive…

A

There is continuous transcription of the Cyclin D gene === overproduction of Cyclin D

*** Means Ras is ON without a growth factor “turning it on”
–> Doesn’t need the growth factor signal to induce Cyclin D production, it simply does it all the time

27
Q

Normal vs Cancerous Ras Pathway

A

NORMAL
Ras-GDP <—-> Ras-GTP = Controlled Proliferation

CANCER
Ras GDP ——> Ras-GTP = Uncontrolled Proliferation

28
Q

Problems with inhibiting Ras as a treatment?

A

Ras is an essential component of the normal cell response to growth factors

–> Inhibiting Ras would also affect healthy/normal cell division

29
Q

What percent of Cancers have a Ras mutation?

A

20% of all human cancers

30
Q

Tumor Suppressors

A

Genes that normal SUPPRESS cell division (when not mutated)

31
Q

What do tumor suppressors encode for?

A

Encode proteins that HALT cell cycle progression

32
Q

p53 (protein)

A

The best characterized tumor suppressor protein

–> A transcription factor that binds and activates specific genes that encode for proteins that arrest the cell cycle, promote DNA repair, and promote apoptosis

33
Q

What does p53 do?

A

Acts at the G1 checkpoint to HALT the cell cycle in response to DNA damage

34
Q

In response to DNA damage, p53…

A

1) Stops cell cycle progression
2) Initiates DNA repair pathway
3) Promotes apoptosis (if needed)

35
Q

What is p53 known as? Why?

A

“The Guardian of the Genome”

–> Prevents the proliferation of damaged cells, specifically those with abnormal genetic content

36
Q

p53 Pathway

A

1) DNA Damage in cell –> p53 is bound to DNA

2) p53 activates 2 genes:
2.1) Activates gene that transcribes p21
2.2) Activates gene that transcribes DNA repair enzymes
3) The genes transcribe their respective encoded proteins

4) p21 = cyclin inhibitor = inhibitor of the active cdk-cyclin complex

5) G1 checkpoint arrests (prevents DNA replication)

6) DNA repair enzyme attempts to repair DNA
6.1) If DNA is repaired = Cell cycle continues
6.2) If DNA is NOT repaired = apoptosis

37
Q

p21

A

Cyclin Inhibitor –> Gets created (transcribed) thanks to p53 activating the gene that encodes for p21

38
Q

p53 in Cancers

A

Usually non-functional, missing, or under-active

== No arresting of cell cycle and/or repair of DNA

39
Q

Main mutation affecting p53

A

Causes the p53 protein unable to bind to DNA

40
Q

p53 and Ras as the most frequently mutated gene in human cancers:

A

~1/2 of all tumors contain a mutation in p53 or Ras

BIO 202 (33 decks)

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