Cancer Bio Final

What percentage of cancers are caused by viruses?

15 - 25%

Peyton Rous

Known for Rous protocol for inducing sarcomas in chickens

• Chicken with sarcoma in breast muscle

• Remove sarcoma and grind up tissue, collect fine filtrate

• Inject filtrate into young chicken

• Observe sarcoma in infected chicken

Rous Sarcoma Virus (RSV)

Johannes Andreas Grib Fibiger

Studied how specific viruses caused stomach cancer in rats

Spiroptera carcinoma - Roundworm parasite of rats

• Possible link between parasite and stomach cancer

• Controversial

Others recreated the experiment to different results

Renato Dulbecco

Italian-American Virologist who won nobel prize in 1975 for his work on oncoviruses

First to grow cells in a petri dish

Genes from viruses incorporated into host, cause mutations in host making them cancer cells

Howard M. Temin

Convinced that he wants to find that what was in the filtrate was a virus

Starts with RSV (Rous Sarcoma Virus)

RSV causes cell transformations

• Infected with RSV particle

• Transformation of a cell

• Multiplication

Anchorage - independent growth on soft agar

• Normal cells can’t anchor, die, but cancerous cells don’t need and can grow on soft agar

What was revolutionary about Howard Teemin’s discovery

Temin hypothesized that retroviruses used a DNA intermediate (provirus) to integrate their RNA genomes into host cells

Temin and David Baltimore discovered reverse transcriptase, and enzyme which confirmed this hypothesis and allows integration by creating DNA from RNA

Nude Mice

Growth of human ear on back of a mouse

Temin made sarcomas on mice

People started working on other viruses and found support

Temin RSV Experiment

Focused on if viruses have to be present at all times to cause mutations

Conclusion: Yes

Higher temp causes virus to be deactivated,

RSV must be present at all times to maintain cells transformations

Properties of transformed cells

Altered morphology/shape

Loss of contact inhibition

Ability to grow without attachment (anchorage independence)

Reduced requirement for mitogenic growth factors

High saturation density

Inability to halt proliferation in response to deprivation of growth factors

Increased transport of glucose

Integration of retroviruses into chromosomal DNA

1) Entry into cell and shedding of envelope

2) Reverse transcriptase (DNA/RNA and then DNA/DNA)

3) Integration of DNA copy into host chromosome

4)Integrated DNA (=provirus) transcribed and translated into proteins —> Many new virus particles

Types of Retroviruses

Transforming vs non-transforming

• Transforming: Carry viral oncogenes → Rapid tumor development

• Non-transforming: Don’t carry oncogenes, longer period of inducing tumors by inserting themselves within or near oncogenes

ALV- Infection but no-transformation

RSV-Infection and transformation

Michael Bishop / Harold Varmus and RSV, src

Studying RSV

RSV contains a gene called v-src that is responsible for transforming normal cells into cancerous ones

These genes are actually mutated forms of normal genes (c-src, which is a proto-oncogene)

c-src (proto-oncogene) is kidnapped by the RSV to cause cell transformation

List four oncogenes and how they become oncogenes

src (Rous sarcoma virus)

• non-receptor TK (Tyrosine kinase)

• Sarcoma (chickens)

ros (UR2)

• RTK, unknown ligand

• Sarcoma (chickens)

myc (myelocytomatosis 29)

• Transcription factor

• Myeloid leukemia (Chickens)

akt (AKT8)

• ser/thr kinase

• lymphoma (mouse)

What ideas came from retrovirus discovery?

1) If retroviruses could

All transforming powers of RSV derived from presence of a single gene

Maybe other transforming retroviruses had acquired other cellular genes unrelated to src

c-myc and viruses

Encodes for a transcription factor (MYC) that regulates numerous other things related to cell growth

some retroviruses, such as avian leukosis virus (ALV),

• ALV integrates its DNA randomly into a promotor / regulator region of c-myc, upregulating c-myc (insertional mutanogenesis)(expression and making it over expressed

• Some viruses carry a mutated copy

Result = uncontrolled proliferation due to over production of MYC

src and its role in cell signaling

a non-receptor tyrosine kinase, plays critical role in cell signaling

Starts pathway that recruits AKT to the membrane, AKT fully phosphorylated

phosphorylates targets like

• GSK-3β (promoting proliferation)

• BAD (inhibiting apoptosis)

• HIF-1α (promoting angiogenesis)

Viral inactivation of p53

HPV (Human papilloma virus) 16 and 18 high risk, innactivates p53

adeno E1B blocks transcriptional acctivation

Also inactivation of Rb protein fn (tumor supressor) regulating TFs like E2F

Few more oncogenes

Name of v, oncogene, type of oncoprotein, cancer in humans

Harvey sarcoma, (H-ras), small G protein, bladder carcinoma. OG in rodents

Kirsten sacroma, (K-ras), small protein, many types of cancer, og in rodents

Mechanisms of hepatocarcinogenesis

1) Chronic infection or damage from HBV, HCV, Alcohol, Alfatoxin B1 (comes from fungi)

2) Liver cirrhosis and DNA damage

3) genomic instability and loss of p53 (Aflatoxin B1 big role in loss of p53)

Which types of HPV are high risk

HPV 16 and 18

can lead to cervical cancer

sexually transmitted

How does HPV cause cancer?

Infects basal layer of cells

With persistent infection, integrates its DNA into host Genome

• E6 protein binds to p53 and causes degradation

• E7 binds to Rb (a tumor supressor which regulates the cell cycle (E2F TF which promotes cell cycle entry)

What preventative measures are there for HPV?

Gardasil vaccine

• Protects against most dangerous forms of HPV and their cancer link

• Also protects against more mild form, the formation of genital warts

Risks between diet and cancer

Obesity

• 30-40% increased cancer risk

• Free radicals

• DNA adducts

What is the significance of high fructose corn syrup?

Found in lots of high calorie foods now

Very cheap and abundant - lobbyists and corn subsidies

Was a part of cars for a little, then limited

Fructose

Vegetables and fruits have ~15g

• These typically have other fiber, vitamins, minerals

Why is Fructose / sugar bad for us?

• Normally: Glucose in blood stream, insulin released to aid glucose absorption, glucose is uptaken by muscles and brain and/or converted to glycogen

• Here: Fructose goes through this whole process without being recognized, goes directly into liver

• Most changes to fat / adipose tissue

Why is fat bad / does it increase cancer risk

• Adipose tissue releases Leptin after you eat, makes you feel full

• Leptin works on your hypothalamus, expenditure vs intake signal

  • Fat cells empty = no leptin, eat

• Too many fat cells builds leptin resistance, always hungry (Leptin resistance essentially means no productive leptin signal) (“Gas gauge broken”

Describe the Princeton experiment

Rats being fed different diets

Those with access to high fructose corn syrup gained 48% more weight

Boy that was always hungry and tired, he was born with mutation affecting leptin

Gave him a leptin supplement, went to normal body size

How does Obesity increase cancer risk

Higher sex hormone production

• ^ IGF1

• ^ Progesterone

• ^ Estrogen

v Apoptosis

^ Cell proliferation

^ levels of leptin, lower adepokines

By default, obese people have higher free radical count

Increased inflammation caused by these hormones and cytokines / interlukens

• This results in the generation of free radicals

Higher insulin resistance

Obesity/fat cells → Inflammation → Free radicals → Oxidative stress

Estrogens

Steroid ring system

Estradiol

Estrone

Estrogen broken down, estrone is a hyper free radical due to its oxygen

Estrogen effects on cancer

Estrogen can increase the chances of developing a new spontaneous mutation, stimulate division of existing mutant and uterine cells

Higher estrogen = higher cell proliferation

Lower estrogen = cell death

What is the function of estrogen? How does having children and getting a period earlier effect women (and their cancer risk)

Estrogen is a hormone found at higher levels in women

• Controls cholesterol

• Strengthens bones

• Programs milk production

• Prepares for fetus

Pregnancy and childbirth drastically lower estrogen levels in women

Lowest after menopause

Higher estrogen levels (from earlier period OR no childbirth) increase cancer risk

Cooking and cancer risk

Heterocyclic amines (HCAs) and polycyclic aromatic hydrocarbons (PAHs) formed when meats are cooked at high temperatures

• Exposure to high levels of HCAs and PAHs can cause cancer in animals; unclear if same for humans

What chemical adducts do carcinogens HCA and PAH cause

• Benzopyrene

• Estrone

• 3-methylcholanthrene

Activation of carcinogens

Many important carcinogens require chemical activation

Multiple enzyme systems involved in activation

Linkage from

• Chemical activation

• Adducts

• Specific mutations

• Cancer

What are bulky adducts?

Large, covalently attached chemical groups that form when carcinogens bind to DNA

Usually attach to guanine, lead to mutations if not repaired properly

Specifically, can cause problems in p53, leading to mutation

Describe what the differences are between human and carnivore intestines and how this may cause issues

Humans - Longer and less acidic

Carnivores - Very acidic and short

Issues:

if humans eat like obligate carnivores

• Low fiber increases colon cancer risk

  • Fiber fuels gut bacteria, reduces inflamation

  • Whole grains, fruits, vegetables

• High protein intake strains kidneys (urea)

Antioxidants

Remove excess free radicals

Colorful vegetables very high in them

Cyclins and cdks

S-Cdk:

• Initiate and complete DNA replication.

• Prevent DNA replication during mitosis.

M-Cdk:

• Induces assembly of the mitotic spindles and insure that the  replicated chromosomes attach to the spindles.

• Chromosomes condensation, microtubules rearrangement,  nuclear envelope breakdown and reorganization of the Golgi and ER. 

Cyclin conc rises gradually during interphase and then drops sharply after mitosis

R point and regulation

R point = restriction point

Cyclin D binds and activates CDK 4/6, this complex then begins to phosphorylate the Rb protein

In its active, unphosphorylated form, Rb binds to E2F (TF), prevents them from innitiating replication stuff

Phosphorylation of Rb inactivates it → causes Rb to release E2F.

E2F further induces transcription of Cyclin E, which binds to CDK 2 to hyperphosphorylate the Rb protein, this is a positive feedback loop triggering the

Phosphorylation and dephosphorylation of CDK-cyclins

M-cyclin binds to M-cdk, inhibiting it

inhibitory kinase (Wee1) and activating kinase (Cak) bind phosphate to it, so there is both an activating and inhibiting phosphate on (= innactive)

activating phosphatase (Cdc25) removes the inhibitory phosphate, activating the m-cdk

Active M-Cdk exhibits positive feedback on Cdc25 phosphatase, inhibiting it

Cyclin E and breast cancer progression

High total levels of Cyclin E = More death chance

EGFR

Epidermal Growth Factor Receptor

Receptor for EGF

Mutations to EGFR are highly linked to cancer

Three domains - Extracellular, Transmembrane, intracellular domain (Tyrosine kinase)

Ligand (EGF) binds and conforms EGFR, phosphorylates a tyrosine initiating a signaling pathway

Tyrosine at 590, 700, 1060 aa position

EGFR pathway

Grb 2 (protein) binds to phosphorylated tyrosine on the receptor, recruits SOS binds through the SH2 and SH3 domains of the Grb 2 protein

SOS binds to Ras (proto-oncogene) which further signals (this is the MAP kinase pathway (Ras→)

• recruiting Raf1

• which recruits Mek

  • Recruits Erk1/2 (= MAPK)

—>Proliferation

Phospholipids and phospholipases in signal transduction

1) Phosphatidyl-inositol (PI):

• OH groups on inositol phosphorylated

2) Phosphatidyl-inositol diphosphate (PIP2)

• PI3K (kinase)

3) PIP3

• PTEN can convert PIP3 back to PIP2

AKT / PKB binds to PIP3

Hyperactivity of PIP3 or inactivity of PTEN causes cancer

• PI3K mutation leads to much higher death rates

Role of AKT / PKB (protein kinase B) in signaling pathways

• Involved with MDM2, which degrades P53

• Can go back and turn on Raf1, which can turn on MAPK pathway

Cell cycle checkpoints

G1 Checkpoint - Enter mitosis—are conditions favorable?

G2 Checkpoint - Is all DNA replicated? Is all DNA damage repaired?

M phase checkpoint - Are all chromosomes atrached to the spindle properly

Control of R point by pRb

Message comes in, Cyclin D and CDK4/6 bind together and hypophosphorylate Rb

Normally Rb holds on to E2F

Rb gets hyperphosphorylated by CDK2 and Cyclin E (once they accumulate)

E2F released and generates more Cyclin E and CDK2, positive feedback

Passes the R point, once crossing it cannot go back

Inhibitors of Cyclins

D-CDK 4/6

• P16 INK4A

• P15 INK4B

• P18 INK4C

• P19 INK4D

Inhibitors of other cyclins

• P57 Kip2

• P27 Kip1

• P21Cip1

Result of having higher levels of cyclin E

Poorer prognosis with breast cancer

Hallmarks of Apoptosis

1) Plasma membrane herniated and form structures called blebs

2) Shrinkage of cell

3) Collapse of nucleus and fragmentation of genomic DNA

4) Fragmentation of golgi apparatus and cleavage of nuclear protein called PARP

5) Breakage of cells and formation of membrane-bound apoptotic bodies

6) Rapid phagocytosis by macrophages or neighboring cells

Apoptosis cell signaling

Cytochrome c binds to Apaf-1

• These form an apoptosome

Recruitment of the initiator procaspase procaspase-9 (turns to active caspase-9)

• This activates executioner caspases (procaspase 3, 6, 7—>caspase 3, 6, 7)

Executioner caspases cleave proteins like lamin, actin, vimentin, etc (known as death substrates)

Smac/diablo is released from mitochondria in response to apoptotic signals (in addition to cytochrome c)

• Inhibits IAPs (inhibitor of apoptosis proteins) which normally inhibit the caspases

Activation of apoptosis by p53

With damage, ATM/ATR kinases phosphorylate p53

Bax - forms holes in the mitochondrial membrane releasing cytochrome c and SMAC/Diablo

FAS also turned on by p53

IGFBP-3 released from cell, binds IGF, which binds to receptor turning on PI3K

Roles of angiogenesis

• Forms new blood vessels during healing at site of injury

• Develops collateral circulations during ischemia

• Allows tumors to grow

• Pathogenic vessel growth can result in diseases

Angiogenesis signaling

VEGFR family

• VEGFR-A most prevelant/potent

• VEGF-A binds to VEGFR-2 and other signals, allowing angiogenesis

Bevacizumab is a powerful treatment for anti-angiogenic activity

Pro and anti apoptotic genes

Pro

• Bad

• Bax

• Bak

• Puma

Anti

• BCl2

• BClx

• MCl1

Tumor grading (TNM)

T - Tumor (size, cm)

N - Nodes (Regional metastases)

M - Metastases (distant)

Stages I-IV

Stage I = Local disease, no nodal or distant metastases

Stage IV - Distant metastases

Imaging procedures

X-rays:

    X-rays use low doses of radiation to create pictures of the inside of your body.

CT Scan:

    An x-ray machine linked to a computer takes a series of detailed pictures of your organs..

Contrast CT Scan:

material helps make these pictures easier to read.

Nuclear scan:

    For this scan, you receive an injection of a small amount of radioactive material, which is sometimes called a tracer. radioactive substance quickly. This type of scan may also be called radionuclide scan.

Ultrasound:

    An ultrasound device sends out sound waves that people cannot hear. The waves bounce off tissues inside your body like an echo. A computer uses these echoes to create a picture of areas inside your body. This picture is called a sonogram.

 MRI:

    A strong magnet linked to a computer 

PET scan:

    For this scan, you receive an injection of a tracer. Then, a machine makes 3-D pictures that show where the tracer collects in the body. These scans show how organs and tissues are working.

   

Diagnosis and staging of breast cancer

IDK look up a video or something

0 - 4 with 0 being non-invasive ductal carcinoma in situ

Cancer treatments

Chemotherapy

• Alkylating agents to cause apoptosis (binds to guanine)

Antimetabolites: Interfere with DNA synthesis

• 5-florauracil

• methotrexate

Hormone therapy - Estrogen or progesterone

• Treat with tamoxifen: competes for receptors and does not allow estrogen or progesterone to bind

Antibiotics - Interfere with enzymes involved in DNA replication

• Doxorubicin

• Adriamycin

Cancer related proteins / receptors and their treatments / inhibitors

VEGF (angiogenic protein): Bevacizumab

EGFR: Gefitinib, Erlotinib

EGF: Trastuzumab, Pertuzumab

VEGFR: Sunitinib

PDL-1 and PD1

1. T cells become activated upon recognizing a foreign or tumor antigen via their T-cell receptor (TCR).

2. Tumor cells or APCs express PD-L1.

3. PD-L1 binds to PD-1 on T cells.

4. This sends an inhibitory signal into the T cell:

   • ↓ T cell proliferation

   • ↓ Cytokine production

   • ↓ Cytotoxic activity

Result: Immune response is suppressed.

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In Cancer:

• Many tumors overexpress PD-L1 to "turn off" nearby T cells.

• This allows tumors to evade immune detection and destruction.