Benign vs Malignant Tumours - not all tumours are invasive Tumour - abnormal growth of tissye Tumorigenesis - formation of tumours Benign tumour: e.g. freckles and moles generally stop g___ do not i___ other parts of body t___ m___ can still cause p____ (less freq) e.g. if impact nerve when removed generally d___ g___ b___ malignant tumours can develop from benign tumours Malignant tumours p____ e____ i___ healthy tissues spread to other parts of the body (m____) d____ n____ bodily functions induce formation of new b___ v___ (a____) to obtain nutrients and O2 to e___ tumour growth can form from benign tumours

Benign tumour: e.g. freckles and moles generally stop growing do not invade other parts of body tumour mass can still cause pathology (less freq) e.g. if impact nerve when removed generally dont grow back malignant tumours can develop from benign tumours Malignant tumours proliferate endlessly invade healthy tissues spread to other parts of the body (metastasis) disrupt normal bodily functions induce formation of new blood vessels (angiogenesis) to obtain nutrients and O2 to enhance tumour growth can form from benign tumours

Cancer is linked to age Cancer cells contain many s____ mutations A single mutation is n__ e___ to change a normal cell into cancer cell Cancer cells require several a_____ mutations (takes years) number of mutations likely to increase with age

Cancer is linked to age Cancer cells contain many somatic mutations A single mutation is not enough to change a normal cell into cancer cell Cancer cells require several accumulated mutations (takes years) number of mutations likely to increase with age

Age and enhanced exposure to mutagens increases cancer incidence Why? Ageing reduces t____ length, increases chance of f____ and c____ i____ Ageing reduce ability to r___ ___ d____/e____ Premature ageing syndromes have underlying genetic DNA repair defects Longer exposure to mutagens/risk factors increases risk e.g. smoking/UV light exposure

Age and enhanced exposure to mutagens increases cancer incidence Why? Ageing reduces telomere length, increases chance of fusions and chromosomal instability Ageing reduce ability to repair DNA damage/errors Premature ageing syndromes have underlying genetic DNA repair defects Longer exposure to mutagens/risk factors increases risk e.g. smoking/UV light exposure

Oncogene a gene that when mutated or expressed at h___ l___ helps turn a nomal cell into a cancer cell (this process is called t_____) Proto-oncogene the normal form of the gene typically invovled in processes that p___ c___ p___ (i.e. d___), cell g___, or cell m____/i___ well known examples include:

Oncogene a gene that when mutated or expressed at high level helps trurn a nomal cell into a cancer cell (this process is called transformation) Proto-oncogene the normal form of the gene typically invovled in processes that promote cell proliferation (i.e. division), cell growth, or cell motility/invasivenss e.g. Ras, Myc, PI3K, B-Raf

Tumour suppressor gene (TSG) gene that acts to p___ a normal cell form turning into a cancer cell (also known as a__-o__) TSGs act by l__ c__ p___, promoting a__ (i.e. cell death), and c___ s___ or preventing m___ Mutations in TSGs may lead to cancer, but one must lose b___ c___ of the gene (Knudson 2-hit theory) well known examples include:

Tumour suppressor gene (TSG) gene that acts to prevent a normal cell form turning into a cancer cell (also known as anti-oncogenes) TSGs act by limiting cell proliferation, promoting apoptosis (i.e. cell death), and cellular senescence or preventing metastasis Mutations in TSGs may lead to cancer, but one must lost both copies of the gene (Knudson 2-hit theory) well known examples include: p53, Rb, PTEN, ECadh

Normal cellular functions of Proto-oncogenes and TSGs Proto-oncogene Typical Examples g__ f___ r__ e__ e.g. k____ t___ f___ Normal cellular roles ___ cell p___ ___cell d___ ___ a___ or s___ ___ cell m___

Normal cellular functions of Proto-oncogenes and TSGs Proto-oncogene Typical Examples growth factors receptors enzymes e.g. kinases transcription factors Normal cellular roles Promote cell proliferation inhibit cell differentiation inhibit apoptosis or senescence promote cell migration

Normal cellular functions of Proto-oncogenes and TSGs TSG Typical Examples A___ and cell p____ molecules receptors enzymes e.g. kinases transcription factors Normal cellular roles ___ cell proliferation ___ cell differentiation ___ apoptosis or senescence ___ s___ s___ ___ DNA r___ p___

Normal cellular functions of Proto-oncogenes and TSGs TSG Typical Examples Adhesion and cell polarity molecules receptors enzymes e.g. kinases transcription factors Normal cellular roles control cell proliferation promote cell differentiation promote apoptosis or senescence promote stationary state promote DNA repair programs

Cancer Biology Flashcards by Leonard Tan

What is cancer?

Cancer: uncontroled g____ of the p____ of t_____- host cells

Melanoma: M_____ t___ that arises from u_____ p_____ of m______ (pigment producing cells)

What is cancer?

Cancer: uncontroled growth of the progeny of transformed host cells

Melanoma: Malignant tumour that arises from uncontrolled proliferation of melanocytes (pigment producing cells)

How well did you know this?

Not at all

Perfectly

Cancer - Cells behaving badly

Normal somatic cells behave in a socialy responsible way to ensure survival of organism

Cancer cells behave selfishly

accumulate mutations that allow them to
- avoid d______
- divide u______
- move throughout body at expense of ______-

Cancer - Cells behaving badly

Normal somatic cells behave in a socialy responsible way to ensure survival of organism

Cancer cells behave selfishly

accumulate mutations that allow them to
- avoid death
- divide uncontrollably
- move throughout body at expense of neighbouring cells and whole organism

How well did you know this?

Not at all

Perfectly

Benign vs Malignant Tumours

not all tumours are invasive

Tumour - abnormal growth of tissye

Tumorigenesis - formation of tumours

Benign tumour:

e.g. freckles and moles
generally stop g___
do not i___ other parts of body
t___ m___ can still cause p____ (less freq) e.g. if impact nerve
when removed generally d___ g___ b___
malignant tumours can develop from benign tumours

Malignant tumours

p____ e____
i___ healthy tissues
spread to other parts of the body (m____)
d____ n____ bodily functions
induce formation of new b___ v___ (a____) to obtain nutrients and O2 to e___ tumour growth
can form from benign tumours

Benign tumour:

e.g. freckles and moles
generally stop growing
do not invade other parts of body
tumour mass can still cause pathology (less freq) e.g. if impact nerve
when removed generally dont grow back
malignant tumours can develop from benign tumours

Malignant tumours

proliferate endlessly
invade healthy tissues
spread to other parts of the body (metastasis)
disrupt normal bodily functions
induce formation of new blood vessels (angiogenesis) to obtain nutrients and O2 to enhance tumour growth
can form from benign tumours

How well did you know this?

Not at all

Perfectly

Many different types of cancer

Classified based on:

Melanoma: cancer of p____ forming s___ cells (m____)

Many different types of cancer

Classified based on: cells/tissue origin

Melanoma: cancer of pigment forming skin cells (melanocyte)

How well did you know this?

Not at all

Perfectly

Cancer - a genetic disease

Cancer is caused by genetic changes that affect gene expression or function

These genetic changes can be caused by:

m____ e.g. due to ___damage
c____ a____ e.g. translocation, gene amplification, deletion
introduction of genes by v___

These genetic changes can be caused by:

mutations e.g. due to DNA damage
chromosomal abnormalities e.g. translocation, gene amplification, deletion
introduction of genes by viruses

How well did you know this?

Not at all

Perfectly

Cancer is linked to age

Cancer cells contain many s____ mutations

A single mutation is n__ e___ to change a normal cell into cancer cell

Cancer cells require several a_____ mutations (takes years)
- number of mutations likely to increase with age

Cancer is linked to age

Cancer cells contain many somatic mutations

A single mutation is not enough to change a normal cell into cancer cell

Cancer cells require several accumulated mutations (takes years)
- number of mutations likely to increase with age

How well did you know this?

Not at all

Perfectly

Age and enhanced exposure to mutagens increases cancer incidence

Why?

Ageing reduces t____ length, increases chance of f____ and c____ i____
Ageing reduce ability to r___ ___ d____/e____
- Premature ageing syndromes have underlying genetic DNA repair defects
Longer exposure to mutagens/risk factors increases risk e.g. smoking/UV light exposure

Age and enhanced exposure to mutagens increases cancer incidence

Why?

Ageing reduces telomere length, increases chance of fusions and chromosomal instability
Ageing reduce ability to repair DNA damage/errors
- Premature ageing syndromes have underlying genetic DNA repair defects
Longer exposure to mutagens/risk factors increases risk e.g. smoking/UV light exposure

How well did you know this?

Not at all

Perfectly

Cancer progresses from accumulated mutations (clonal evolution)

The transition of a normal cell to a canrcerous cell involves the accumulation of successive mutations

First mutation might endow a cell with slight p____ a_____
Second mutation might g___ e___ p____ and i___ t___ a___
Third mutation may allow cells to i___ s____ t___ and m____ to distant tissue sites
Cancer cells are characteristically g____ u____

Cancer progresses from accumulated mutations (clonal evolution)

The transition of a normal cell to a canrcerous cell involves the accumulation of successive mutations

First mutation might endow a cell with slight proliferative advantage
Second mutation might greatly enhance proliferation and influence tissue architecture
Third mutation may allow cells to invade surrounding tissues and metastasise to distant tissue sites
Cancer cells are characteristically genetically unstable

***cancer cells with 3 mutations have out-proliferated the other cells with fewer mutations and have now become the dominant cell type in the tumour mass

generating the genetic unstability requires the cancer to mutate to overcome the selective pressures of the envronment

How well did you know this?

Not at all

Perfectly

Pathways of tumorigenesis

In normal tissues, net birth and death of cells is b____ i.e. at e____

Tumour formation (tumourigenesis) occurs when this balance is disturbed by:

INCREASED ___
DECREASED ____

Pathways of tumorigenesis

In normal tissues, net birth and death of cells is balanced i.e. at equilibrium

Tumour formation (tumourigenesis) occurs when this balance is disturbed by:

INCREASED cell birth
DECREASED cell death

How well did you know this?

Not at all

Perfectly

Hallmarks of Cancer

a multi-step process

Tumorigenesis

resisting c___ d___
sustaining p____ s___
evading g___ s___
enabling r___ i____

Metastasis

Inducing a___
activating i___and m____

Hallmarks of Cancer

a multi-step process

Tumorigenesis

resisting cell death
sustaining proliferative signaling
evading growth suppressors
enabling replicative immortality

Metastasis

Inducing angiogenesis
activating invasion and metastasis

How well did you know this?

Not at all

Perfectly

Metastasis

S____ of cancer cells to s___ a__ from the p___ t___
- is what makes cancer such a serious disease
Responsible for __% cancer-associated deaths
very common in l___ s___ c___

Metastasis

Spread of cancer cells to sites away from the primary tumour
- is what makes cancer such a serious disease
Responsible for 90% cancer-associated deaths
very common in late stage cancer

How well did you know this?

Not at all

Perfectly

Hallmarks of Cancer -an update

Emerging hallmarks

Deregulating c___ e___
- to feed the high rate of cancer cell p___
- via g___ i___ and m___
Avoiding i___ d___
- via t___-p____ i____
- “i____e_____” and c___ selection

Hallmarks of Cancer -an update

Emerging hallmarks

Deregulating cellular energetics
- to feed the high rate of cancer cell proliferation
- via genome instability and mutation
Avoiding immune destruction
- via tumour-promoting inflammation
- “immunoediting” and clonal selection

How well did you know this?

Not at all

Perfectly

Oncogene

a gene that when mutated or expressed at h___ l___ helps turn a nomal cell into a cancer cell (this process is called t_____)

Proto-oncogene

the normal form of the gene
typically invovled in processes that p___ c___ p___ (i.e. d___), cell g___, or cell m____/i___
well known examples include:

Oncogene

a gene that when mutated or expressed at high level helps trurn a nomal cell into a cancer cell (this process is called transformation)

Proto-oncogene

the normal form of the gene
typically invovled in processes that promote cell proliferation (i.e. division), cell growth, or cell motility/invasivenss
e.g. Ras, Myc, PI3K, B-Raf

How well did you know this?

Not at all

Perfectly

Tumour suppressor gene (TSG)

gene that acts to p___ a normal cell form turning into a cancer cell (also known as a__-o__)
TSGs act by l__ c__ p___, promoting a__ (i.e. cell death), and c___ s___ or preventing m___
Mutations in TSGs may lead to cancer, but one must lose b___ c___ of the gene (Knudson 2-hit theory)
well known examples include:

Tumour suppressor gene (TSG)

gene that acts to prevent a normal cell form turning into a cancer cell (also known as anti-oncogenes)
TSGs act by limiting cell proliferation, promoting apoptosis (i.e. cell death), and cellular senescence or preventing metastasis
Mutations in TSGs may lead to cancer, but one must lost both copies of the gene (Knudson 2-hit theory)
well known examples include: p53, Rb, PTEN, ECadh

How well did you know this?

Not at all

Perfectly

Normal cellular functions of Proto-oncogenes and TSGs

Proto-oncogene

Typical Examples

g__ f___
r__
e__ e.g. k____
t___ f___

Normal cellular roles

___ cell p___
___cell d___
___ a___ or s___
___ cell m___

Normal cellular functions of Proto-oncogenes and TSGs

Proto-oncogene

Typical Examples

growth factors
receptors
enzymes e.g. kinases
transcription factors

Normal cellular roles

Promote cell proliferation
inhibit cell differentiation
inhibit apoptosis or senescence
promote cell migration

How well did you know this?

Not at all

Perfectly

Normal cellular functions of Proto-oncogenes and TSGs

TSG

Typical Examples

A___ and cell p____ molecules
receptors
enzymes e.g. kinases
transcription factors

Normal cellular roles

___ cell proliferation
___ cell differentiation
___ apoptosis or senescence
___ s___ s___
___ DNA r___ p___

Normal cellular functions of Proto-oncogenes and TSGs

TSG

Typical Examples

Adhesion and cell polarity molecules
receptors
enzymes e.g. kinases
transcription factors

Normal cellular roles

control cell proliferation
promote cell differentiation
promote apoptosis or senescence
promote stationary state
promote DNA repair programs

Causative mutations to proto-oncogenes and TSGs

Oncogene

O_____ mutation (___ of function)
- Promote cell transformation
- only need o___ c___ of proto-oncogene to be mutated in order to have effect on cell

TSG

U____ mutation (___ of function)
- two i____ mutations
- loss of h___
- functionally e___ the TSG
- promote cell transformation

Causative mutations to proto-oncogenes and TSGs

Oncogene

Overactivity mutation (gain of function)
- Promote cell transformation
- only need one copy of proto-oncogene to be mutated in order to have effect on cell
- 1 accelerator*

TSG

Underactivity mutation (loss of function)
- two inactivating mutations
- loss of heterozygosity
- functionally eliminate the TSG
- promote cell transformation
- 2 brakes*

Pathways to oncogene activation

D___ or p___ m___ in coding sequence
- H__ protein made in n___ amounts
- F__ mutation
R___ mutation (in p__ region)
- n__ protein g__ o___
- I__ expression
G__ a___
- N__l protein g__ o__
- I___ expression
C___ r___
- n___ r__ DNA s___ causes n___ protein to be o___
  - I__ expression
- F___ to a__ t___ g___ produces h___ f___ protein
  - F___ mutation

Pathways to oncogene activation

Deletion or point mutation in coding sequence
- Hyperactive protein made in normal amounts
- Function mutation
Regulatory mutation (in promoter region)
- normal protein greatly overproduced
- Increased expression
Gene amplification
- Normal protein greatly overproduced
- Increased expression
Chromosome rearrangement
- nearby regulatory DNA sequence causes normal protein to be overproduced
  - Increased expression
- Fusion to actively transcribed gene produces hyperactive fusion protein
  - Function mutation

Pathways to oncogene activation

examples and recap

Deletion or point mutation in coding sequence
- e.g. mutant G12V H-Ras
  - Thyroid/bladder cancer
Regulatory mutation (in promoter region)
Gene amplification
- ErbB2 amplification
  - Breast cancer
Chromosome rearrangement
- Myc over-expression
  - Burkitt’s lymphoma
- Bcr-Abl fusion protein
  - Chronic myeloid leukaemia

Pathways to oncogene activation

Deletion or point mutation in coding sequence
- Hyperactive protein made in normal amounts
- Function mutation
  - E.g. mutant G12V H-Ras
    - Thyroid/bladder cancer
Regulatory mutation (in promoter region)
- normal protein greatly overproduced
- Increased expression
Gene amplification
- Normal protein greatly overproduced
- Increased expression
  - E.g. ErbB2 amplification
    - Breast cancer
Chromosome rearrangement
- nearby regulatory DNA sequence causes normal protein to be overproduced
  - Increased expression
    - Myc over-expression
      - Burkitt’s lymphoma
- Fusion to actively transcribed gene produces hyperactive fusion protein
  - Function mutation
    - Bcr-Abl fusion protein
      - Chronic myeloid leukaemia

Key oncogenic pathways in Melanoma

1) NRAS-BRAF-MEK-ERK pathway

activated (mutated) in 70-80% melanoma PTs
Downstream of Receptor Tyrosine Kinases (RTKs) e.g. KIT

How?

BRAF^V600E mutation (~80%)
- Results in c___ a____ Ser/Thr k___
- NRAS-i____
  - then?

Key oncogenic pathways in Melanoma

NRAS-BRAF-MEK-ERK pathway

activated (mutated) in 70-80% melanoma PTs
Downstream of Receptor Tyrosine Kinases (RTKs) e.g. KIT

How?

BRAF^V600E mutation (~80%)
- Valine-glutamic acid mutation at position 600
- Results in constituently active Ser/Thr kinase
- NRAS-independent
  - p-Mek
  - p-ERK
    - Cell growth and proliferation

Key oncogenic pathways in melanoma (2)

2) A___ NRAS mutations in codon 61 (~90% Q___/Q___ mutations)

Disrupt ____ activity of NRAS, locking it in a____ c_____
- BRAF-MEK-ERK
- P__>A___>m___ pathways
  - Activates both pathways leading to s___ c___ and i___ in gene expression responsible for p___
BRAF and NRAS mutations and m___ e___ (dont occur in the same melanomas)
- ~70% of all melanomas
- 30% of driver mutations for melanoma not yet described

Key oncogenic pathways in melanoma (2)

2) Activating NRAS mutations in codon 61 (~90% Q61R/Q61K mutations)

Disrupt GTPase activity of NRAS, locking it in active conformation
- BRAF-MEK-ERK
- PI3K>Atk>mTOR pathways
  - Activates both pathways leading to signalling cascade and increase in gene expression responsible for proliferation
BRAF and NRAS mutations and mutually exclusive (dont occur in the same melanomas)
- ~70% of all melanomas
- 30% of driver mutations for melanoma not yet described

Key oncogenic pathwyas in melanoma

3) KIT - R____ T___ K__ for s___ c__ f___ (SCF)

Mutated in ~_% skin melanomas
- S__ activates
  - Both pathways - recall

Key oncogenic pathwyas in melanoma

3) KIT - Receptor Tyrosine Kinase for stem cell factor (SCF)

Mutated in ~2% skin melanomas
- Simultaneously activates
  - NRAS-BRAF-MEK-ERK
  - PI3K>Atk>mTOR pathways

Receptor Tyrosine Kinases (RTKs) e.g. KIT

G___ f___ receptors

activated by l____-i___ d___ and a____

Receptor Tyrosine Kinases (RTKs) e.g. KIT

Growth factor receptors

activated by ligand-induced dimerization and autophosphorylation

KIT Receptor Tyrosine Kinase

Two major KIT oncogenic activating mechanisms in melanoma

Point mutation
- L___P (exon 11)
  - forces the d___
- K___E (exon 13)
  - causes a__
Results in c___ a___ RTK i.e. l__ i__ s____ without s___ from SCF
- Result in g__ a__

KIT Receptor Tyrosine Kinase

Two major KIT oncogenic activating mechanisms in melanoma

Point mutation
- L576P (exon 11)
  - forces the dimerisation
- K642E (exon 13)
  - causes autophosphorylation
Results in constitutively active RTK i.e. ligand independent signalling without stimulation from SCF
- Result in gene amplification

KIT/RAS/RAF/ERK Pathway and Therapeutic Targets in Melanoma Summary slide Note: * CCND1\>CDK4 are cell-cycle regulators * MITF is also an oncogene

Note: * CCND1\>CDK4 are cell-cycle regulators * MITF is also an oncogene

Micropthalmia-associated transcription factor (MITF) * t\_\_\_\_ factor * p\_\_\_\_ by ERK downstream of KIT/NRAS-BRAF-MAPK-ERK pathway * Required for early melanocyte d\_\_\_, c\_\_ c\_\_\_, s\_\_\_ and m\_\_\_ * Has different i\_\_\_ depending on mRNA s\_\_\_ and a\_\_\_ p\_\_\_ * MITF a\_\_\_\_ observed in \_\_% melanomas * '\_-\_\_\_' i\_\_\_ serves as l\_\_\_-s\_\_\_\_ oncogene in \>\_\_% melanomas

Micropthalmia-associated transcription factor (MITF) * transcription factor * phosphorylated by ERK downstream of KIT/NRAS-BRAF-MAPK-ERK pathway * Required for early melanocyte development, cell cycle, survival and metabolism * Has different isoforms depending on mRNA splicing and alternative promoters * MITF amplification observed in 20% melanomas * 'M-MITF' isoform serves as lineage-survival oncogene in \>80% melanomas

Key TSG pathways in Melanoma 1. ___ negatively regulates NRAS 2. ___ negatively regulates PI3K

Key TSG pathways in Melanoma 1. NF1 (Neurofibromin 1) negatively regulates NRAS 2. PTEN (Phosphataseand tensin homologue) negatively regulates PI3K\>Atk\>mTOR pathway

Neurofibromin 1 (NF1) * N\_\_\_ r\_\_\_\_ of NRAS * 'G\_\_\_ a\_\_\_ p\_\_\_ (GAP)' * e\_\_\_ NRAS G\_\_\_ activity * P\_\_\_ c\_\_\_ from ___ (active) to ___ (inactive) * NF1 loss of function mutations lead to \>NRAS-GTP and \>MAPK-ERK activation * defines ___ most common melanoma subtype after BRAF and NRAS

Neurofibromin 1 (NF1) * Negative regulator of NRAS * 'GTPase activating protein (GAP)' * enhances NRAS GTPase activity * Promotes conversion from NRAS-GTP (active) to NRAS-GDP (inactive) * NF1 loss of function mutations lead to \>NRAS-GTP and \>MAPK-ERK activation * defines 3rd most common melanoma subtype after BRAF and NRAS

Phosphatase and tensin homologue (PTEN) * PI3 Kinase (PI3K) downstream of RTKs p\_\_\_\_ PIP₂ + ATP \> PIP₃ * PIP₃ required for m\_\_\_\_ l\_\_\_\_ and a\_\_\_\_ of ATK * PTEN _____ PIP₃\>PIP₂+P_i (p\_\_\_\_ s\_\_\_\_\_ via \_\_\_) * *PTEN* d\_\_\_ and i\_\_\_\_ mutations found in melanoma, associated with e\_\_\_\_ of i\_\_\_ cells from t\_\_\_ * Treatment with PI3K i\_\_\_ e\_\_\_\_ i\_\_\_\_\_ \*PIP2 and PIP3 are m\_\_\_ b\_\_\_ p\_\_\_\_

Phosphatase and tensin homologue (PTEN) * PI3 Kinase (PI3K) downstream of RTKs promotes PIP₂ + ATP \> PIP₃ * PIP₃ required for mebrane localisation and activation of ATK * PTEN de-phosphorylates PIP₃\>PIP₂+P_i (prevents signalling via ATK) * *PTEN* deletions and inactivating mutations found in melanoma associated with exclusion of immune cells from tumour * Treatment with PI3K inhibitor enhanced immunotherapy \*PIP2 and PIP3 are membrane bound phospholipids

Key TSG across ALL CANCERS 1. Rb (r\_\_\_\_ protein) * regulates c\_\_\_ c\_\_\_ * first TSG * Rb r\_\_\_ m\_\_\_ in melanoma * suggesting a\_\_\_ p\_\_\_ to overcome Rb in melanoma 2. p53 * regulates c\_\_\_ c\_\_ * guardian of the genome * regulates ___ r\_\_\_ * regulates a\_\_\_\_ * only 19% melanomas carry p53 mutations (r\_\_\_\_ m\_\_\_ in melanomas) * suggesting a\_\_\_\_ p\_\_\_\_ to overcome p53 in melanoma \*Overcoming the Rb and p53 pathways allows cancer cells to s\_\_\_ and p\_\_\_ despite s\_\_\_ and DNA d\_\_\_

Key TSG across ALL CANCERS 1. Rb (retinoblastoma protein) * regulates cell cycle * first TSG * Rb rarely mutated in melanoma * suggesting alternative pathways to overcome Rb in melanoma 2. p53 * regulates cell cycle * guardian of the genome * regulates DNA repair * regulates apoptosis * only 19% melanomas carry p53 mutations (rarely mutated in melanomas) * suggesting alternative pathways to overcome p53 in melanoma \*Overcoming the Rb and p53 pathways allows cancer cells to survive and proliferate despite stress and DNA damage

Overcoming Rb and p53 TSG function in Melanoma Rb and p53 are key TSGs in preventing cancer, but if rarely mutated in melanoma - how are their TSG functions overcome in melanoma? 1. Rb acts downstream of ___ pathway to prevent c\_\_ c\_\_\_ e\_\_\_ 2. p53 is not downstream of ___ but can sense numerous t\_\_-a\_\_\_\_ s\_\_\_ active in melanoma

Overcoming Rb and p53 TSG function in Melanoma Rb and p53 are key TSGs in preventing cancer, but if rarely mutated in melanoma - how are their TSG functions overcome in melanoma? 1. Rb acts downstream of NRAS-BRAF-MEK-ERK pathway to prevent cell cycle entry 2. p53 is not downstream of NRAS-BRAF-MAPK-ERK but can sense numerous tumour-associated stresses active in melanoma

Overcoming Rb 1) Role of the cyclin D1-CDK4 oncogenic pathway in Melanoma * Cyclin D1 binds CDK4 (and CDK6) to ____ Rb (pRb = \_\_\_\_\_) * results in c\_\_\_ c\_\_\_ e\_\_\_ * Cyclin D-CDK4-Rb pathway d\_\_\_ in \_\_% melanomas * CCND1 (~10%) and CDK4 (~30%) genes a\_\_\_ in melanoma * CDK4 a\_\_\_\_ m\_\_\_ - h\_\_\_ melanoma

Overcoming Rb 1) Role of the cyclin D1-CDK4 oncogenic pathway in Melanoma * Cyclin D1 binds CDK4 (and CDK6) to phosphorylate Rb (pRb = inactive) * results in cell cycle entry * Cyclin D-CDK4-Rb pathway dysregulated in 90% melanomas * CCND1 (~10%) and CDK4 (~30%) genes amplified in melanoma * CDK4 activating mutations - heriditary melanoma

Overcoming Rb 2) Role of p16^INK4A TSG in melanoma * *CDKN2A* gives rise to two m\_\_\_\_ encoding **p16^INK4A** and p14^ARF respectively * p16^INK4A TSG binds to ___ and d\_\_\_ its k\_\_\_ a\_\_\_ * unable to p\_\_\_ Rb * allowing c\_\_\_ c\_\_\_ entry * *CDKN2A* d\_\_\_ and p16^INK4A i\_\_\_\_ m\_\_\_ in melanoma

Overcoming Rb 2) Role of p16^INK4A TSG in melanoma * *CDKN2A* gives rise to two mRNAs encoding p16^INK4A and p14^ARF respectively * p16^INK4A TSG binds to CDK4 and downregulates its kinase activity * unable to phosphorylate Rb * allowing cell cycle entry * *CDKN2A* deletions and p16^INK4A inactivating mutations in melanoma

p53 is a c\_\_\_ s\_\_\_ s\_\_\_\_ - activated by many tumour-associated stresses * p53 is not downstream of ___ pathway but can sense numerous t\_\_\_-a\_\_\_ s\_\_\_\_ active in melanoma

p53 is a cellular stress sensor - activated by many tumour-associated stresses * p53 is not downstream of NRAS-BRAF-MAPK-ERK pathway but can sense numerous tumour-associated stresses active in melanoma

Role of p53 and p14^ARF TSGs in melanoma * CDKN2A gives rise to two mRNAs encoding p16INK4A and **p14^ARF** respectively * MDM2 u\_\_\_ p53 = marked for d\_\_\_\_ * MDM2 important n\_\_\_ r\_\_\_ of p53 TSG function * p14^ARF b\_\_\_/s\_\_\_ MDM2 = unleashing p53 tumour suppressor function * *CDKN2A* d\_\_\_ and p14^ARF i\_\_\_\_mutations in melanoma * *CDKN2A* i\_\_\_ mutations = hereditary melanoma

Role of p53 and p14^ARF TSGs in melanoma * CDKN2A gives rise to two mRNAs encoding p16INK4A and **p14^ARF** respectively * MDM2 ubiquinates p53 = marked for degradation * MDM2 important negative regulator of p53 TSG function * p14^ARF binds/sequesters MDM2 = unleashing p53 tumour suppressor function * *CDKN2A* deletions and p14^ARF inactivating mutations in melanoma * *CDKN2A* inactivating mutations = hereditary melanoma

Overcoming Rb and p53 TSG pathways in Melanoma - summary * CDKN2A gives rise to p16^INK4A and p14^ARF mRNAs, which regulate Rb and p53 pathways respectively * CDKN2A deletions and p16^INK4A and p14^ARF inactivating mutatons in melanoma * CDKN2A inactivating mutations = hereditary melanoma

Telomeres and telomerase * 2nd barrier after overcoming p53 and Rb mutations = shortened telomeres * Telomeres * r\_\_\_ s\_\_\_ found at end of chromosomes * protect from ___ d\_\_ or c\_\_\_ f\_\_\_ events * s\_\_\_ each time a cell divides = r\_\_\_ s\_\_\_ (cell stops dividing forever) * Telomerase * E\_\_\_ that e\_\_\_ telomeres, allowing cells to c\_\_\_ to d\_\_\_ * u\_\_\_ in \_\_% cancers * T\_\_\_ r\_\_ t\_\_\_\_ (TERT) = c\_\_\_ component

Telomeres and telomerase * 2nd barrier after overcoming p53 and Rb mutations = shortened telomeres * Telomeres * repetitive sequences found at end of chromosomes * protect from DNA damage or chromosome fusion events * shorten each time a cell divides = replicative senescence (cell stops dividing forever) * Telomerase * Enzyme that extends telomeres, allowing cells to continue to divide * upregulated in 90% cancers * Telomerase reverse transcriptase (TERT) = catalytic component

Telomerase Reverse Transcriptase (TERT) * Dividing premalignant melanocytes must activate telomere maintenance mechanism (TMM) to avoids replicative senescence * Invariably involves TERT * ~77% intermediate-stage melanomas carry TERT promoter mutations (TPM) * However?? * Instead, TPM allows for....?

However, * TPMs dont induce enough telomerase in premalignant melanocytes to counteract short telomeres * Instead, TPM extends proliferative capacity between replicative senesence and crisis/apoptosis * Allows rare cells to attain additional mutations to attain a TMM, raise telomerase activity, and beome immotalised (example of how mutations work together in cancer)