Inducing Apoptosis in Cancer

1
Inducing Apoptosis in Cancer
2
Apoptosis is an Essential Process

• Apoptosis (programmed cell death) plays an
  important rolein normal development and
  homeostasis
• Apoptosis is activated through two principal
  signaling pathways intrinsic and extrinsic12
• Cancer is often initiated by DNA damage
• Normal cells undergo apoptosis in response to
  stress-inducing events in the cell, such as DNA
  damage
• Dysregulation of apoptosis is critical for cancer
  development and tumor cell survival3

3
Overview of the Two Major Apoptosis Pathways
Pro-apoptotic ligand
Cell-extrinsicpathway
Pro-apoptotic receptor
Caspases
BAX
Mitochondria
BCL2
PUMA
Cell-intrinsicpathway
Stress
Apoptosis
Adapted from Ashkenazi A. Nat Rev Cancer
20022420430.BAX, BCL2-associated protein
BCL2, B-cell chronic lymphocytic
leukemia/lymphoma 2 PUMA, p53-upregulated
modulator of apoptosis.
4
Apoptosis is Carried out by Caspases
Pro-apoptotic stimulus
Initiator caspases
Caspase cascade
Effector caspases
Adapted from Thornberry NA, Lazebnik Y. Science
199828113121316.Caspase, cysteine aspartase.
5
The Intrinsic Apoptosis Pathway
ChemotherapyRadiotherapy
DNA damage
Cell-intrinsicpathway
PUMA, NOXA
BCL2, BCLXL, MCL1
Mitochondria
Cytochrome c
SMAC/DIABLO
APAF1
Caspase 9
IAP
Caspase 3, 6, 7
p53
DNA damage
Adapted from Ashkenazi A. Nat Rev Cancer
20022420430.APAF1, apoptotic protease
activating factor-1 BAK, BCL2 homologous
antagonist/killer BAX, BCL2-associated protein
BCL2, B-cell chronic lymphocytic
leukemia/lymphoma 2 BCLXL, BCL2-like 1 IAP,
inhibitor of apoptosis protein MCL1, myeloid
cell leukemia sequence 1 (BCL2-related) PUMA,
p53-upregulated modulator of apoptosis
SMAC/DIABLO second mitochondria-derived
activator of caspase/direct IAP binding protein
with low pI.
6
The Intrinsic Apoptosis Pathway

• The intrinsic pathway is triggered by the p53
  tumor-suppressor in response to DNA damage and
  other types of severe cell stress
• Conventional anticancer therapies, such as
  chemotherapy and radiotherapy, activate this
  pathway via p53
• p53 activates the intrinsic pathway through
  transcriptional upregulation of pro-apoptotic
  members of the BCL2 family of proteins such as
  PUMA and BAX
• BAX causes the release of cytochrome c from the
  mitochondria, which together with the adaptor
  APAF1, activate the initiator caspase 9
• Caspase 9 activates the effector caspases 3, 6,
  and 7, which are responsible for destroying
  critical components of the cell, and inducing
  apoptosis
• p53 is inactivated by mutations in more than half
  of human cancers

7
The Extrinsic Apoptosis Pathway
Pro-apoptotic ligand
Cell-extrinsicpathway
DR5
DR4
FADD
FLIP
Procaspase 8, 10
Caspase 8, 10
Caspase 3, 6, 7
Apoptosis
Adapted from Ashkenazi A. Nat Rev Cancer
20022420430.FADD, Fas-associated death
domain FLIP, FLICE (FADD-like interleukin
1ß-converting enzyme) inhibitory protein.
8
The Extrinsic Apoptosis Pathway

• The extrinsic pathway triggers apoptosis in
  response to the activation of pro-apoptotic
  receptors, such as DR4 and DR5, by specific
  pro-apoptotic ligands, such as Apo2L/TRAIL
• This pathway stimulates apoptosis independently
  of p53
• Ligand-induced activation of DR4 and DR5 leads to
  the rapid assembly of the death-inducing
  signaling complex (DISC) and the recruitment of
  initiator caspases 8 and 10 through the adaptor
  Fas-associated death domain (FADD)
• Caspases 8 and 10 activate effector caspases 3,
  6, and 7, leading to apoptosis

9
The Two Major Apoptosis Pathways
Pro-apoptotic ligand
Cell-extrinsicpathway
ChemotherapyRadiotherapy
DR5
DR4
DNA damage
Cell-intrinsicpathway
p53
FADD
PUMA, NOXA
BCL2, BCLXL, MCL1
BID
BAX, BAK
Procaspase 8, 10
Mitochondria
Caspase 8, 10
Cytochrome c
SMAC/DIABLO
APAF1
Caspase 9
IAP
Caspase 3, 6, 7
Apoptosis
DNA damage
Adapted from Ashkenazi A. Nat Rev Can
20022420430.APAF1, apoptotic protease
activating factor-1 BAK, BCL2 homologous
antagonist/killer BAX, BCL2-associated protein
BCL2, B-cell chronic lymphocytic
leukemia/lymphoma 2 BCLXL, BCL2-like 1 BID,
BH3-interacting domain death agonist DR, death
receptor FADD, Fas-associated death domain
FLIP, FLICE (FADD-like interleukin 1ß-converting
enzyme) inhibitory protein IAP, inhibitor of
apoptosis protein MCL1, myeloid cell leukemia
sequence 1 (BCL2-related) PUMA, p53-upregulated
modulator of apoptosis SMAC/DIABLO second
mitochondria-derived activator of caspase/direct
IAP binding protein with low pI.
10
Apoptosis via Pro-apoptotic Receptors
(DR4 and DR5)
Endogenous Apo2L/TRAIL
DR4
DR5
Apo2L/TRAIL, apoptosis-inducing ligand 2/tumor
necrosis factor-related apoptosis-inducing
ligand DR, death receptor.
11
Endogenous Apo2L/TRAIL ActivatesPro-apoptotic
Receptors (DR4 and DR5)
DR4
DR5
DR, death receptor.
12
Pro-apoptotic Receptors (DR4 and/or DR5)Recruit
FADD
DR4
DR5
DR, death receptor FADD, Fas-associated death
domain.
13
FADD Recruits Initiator Caspase 8 and/or 10 to
the DISC
DR4
DR5
DISC
Procaspase 8, 10
Procaspase 8, 10
DR, death receptor DISC, death-inducing
signaling complex.
14
Activated Caspase 8 and 10 are Released Into the
Cytoplasm
DR4
DR5
Caspase 8,10
Caspase 8,10
DR, death receptor.
15
Caspase 3, 6, and 7 are Activated
DR4
DR5
Caspase 8, 10
Caspase 8, 10
Caspase 3, 6, 7
Caspase 3, 6, 7
DR, death receptor.
16
Activated Caspase 3, 6, and 7 ExecuteApoptosis
in Tumor Cells
Pro-apoptotic ligand
Cell-extrinsicpathway
ChemotherapyRadiotherapy
DR5
DR4
DNA damage
Cell-intrinsicpathway
p53
FADD
PUMA, NOXA
BCL2, BCLXL, MCL1
BID
BAX, BAK
Procaspase 8, 10
Mitochondria
Caspase 8, 10
Cytochrome c
SMAC/DIABLO
APAF1
Caspase 9
IAP
Caspase 3, 6, 7
Apoptosis
DNA damage
Adapted from Ashkenazi A. Nat Rev Cancer
20022420430.APAF1, apoptotic protease
activating factor-1 BAK, BCL2 homologous
antagonist/killer BAX, BCL2-associated protein
BCL2, B-cell chronic lumphocytic
leukemia/lymphoma 2 BCLXL, BCL2-like 1 BID,
BH3-interacting domain death agonist DR, death
receptor FADD, Fas-associated death domain
FLIP, FLICE (FADD-like interleukin 1ß-converting
enzyme) inhibitory protein IAP, inhibitor of
apoptosis protein MCL1, myeloid cell leukemia
sequence 1 (BCL2-related) PUMA, p53-upregulated
modulator of apoptosis SMAC/DIABLO second
mitochondria-derived activator of caspase/direct
IAP binding protein with low pI.
17
References

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18
References (contd)

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19
References (contd)

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