Intro to hormone dependent cancers: breast and prostate

Question 1

What is a hormone?

Answer 1

A chemical messenger that is made up of specialist cells (usually in endocrine gland) and is released into the bloodstream to have an effect in another part of the body

• can be chemical, peptides or proteins

Question 2

In which organs are hormones produced in?

Answer 2

Endocrine organs.

• Brain there is pineal gland, hypothalamus, pituitary gland
• Thorax, there is thyroid and thymus glands
• Abdomen - pancreas, kidneys, adrenal glands
• Stomach and digestive system
• Male - testest
• female - ovaries and uterus

Question 3

Hormones are grouped into 3 main classes

Answer 3

Steroids - lipid soluble, small molecules e.g testosterone

Peptides/protein hormones - insulin

Modified amino acids / amine hormones - adrenaline

Question 4

What are all steroid hormones synthesised from?

What is the basic structure they have?

Answer 4

Cholesterol which is ingested or synthesised within body

Basic 4-ring steroid backbone structure

Question 5

How are steroids synthesised?

Starting with cholesterol

Answer 5

Cholesterol converted to bi-synthetic precursors and hormones in adrenal cortex

Adrenal cortex secretes primary hormones - corticosteroids and mineralocorticoids

and secretes androgenic and estrogenic precursors released into blood stream - less potent form of final hormone

take up into gonadal tissues (ovaries and testes), metabolised to form fully active hormones like androgens and estrogens

testosterone may be metabolised again into more potent form in some tissues like prostate

Question 6

What are sex hormones responsible for?

Answer 6

Sexual dismorphism between males and females, development of secondary sexual characteristics (e.g growth spurt, body hair, gonadal development, voice change)

Question 7

Steroid hormones work systemically, they have effect on several tissues

Answer 7

Females: oestrogen controls menstrual cycle and breast tissue development, fertility and reproductive organ development, secondary sexual characteristics – body hair etc

Males testosterone controls reproductive and supportive organs (prostate), development of sexual characteristics in men e.g deepening of voice, body hair

Question 8

Which are the top most common cancers in the UK?

Answer 8

Breast and prostate cancer.

Tissues strongly controlled by steroid hormones, hormone dependent

when breast/prostate cancer occurs steroid hormones can still influence how cells grow and function - how disease develops and progresses

can be exploited for treatment of cancers

Question 9

Describe the steroid hormone receptor mechanism

Answer 9

1. Steroid hormones cross into cell cytoplasm, bind to their receptor
2. Binding to the receptor causes conformational change in nuclear receptor, causing it to become activated (and dissociate from any cytoplasmic chaperon proteins, some nuclear receptor dimerise at this point)
3. Nuclear receptor then translocates into nucleus
4. Nuclear receptors bind to specific DNA sequences called steroid response elements located in the promoters of steroid responsive genes
5. Steroid responsive genes switched on and upregulated

Question 10

What are the three main parts of the domain structure of a nuclear receptor?

Answer 10

Highly specific ligand binding domain (LBD) - each individual receptor binds specific steroid molecules with high affinity and specificity

DNA binding domain (DBD). Binds specific DNA sequences with high degree of specificity

Activation function domain (AF1 and 2). Recruits gene activation machinery, some receptors have a secondary AF2 domain towards the C-terminal.

Question 11

Describe the steps in ligand activated transcription factors when activated

Answer 11

1. Ligand binding to the ligand binding site causes a shift in an a-helix, activating the receptor
2. Receptor dimerises, moves into the nucleus from cytoplasm, binds to specific DNA sequences
3. Receptor then recruits DNA modifying enzymes e.g histone deacetylases, other transcription factors and RNA pol to promoters of hormone responsive genes - to inititae gene transcription

Question 12

What domains do the DNA binding domain contain? What is it essential for?

Answer 12

DNA binding domain contains 2 zinc finger domains.

Essential for sequence specific DNA binding.

Sequence contains 4 cysteine residues that can bind to zinc atom and form zinc finger domain.

Holds amino acid backbone together and forms zinc finger domains required for specific DNA binding

Question 13

What is the specific DNA sequences that nuclear receptors bind to called?

What part of the receptors domain helps to recognise them?

Answer 13

Hormone response elements, found in promoters of hormone responsive genes.

Many are palindromic.

Normally 6 DNA bases separated by 3 spacer DNA bases, then another 6 DNA bases repeated again / palindromic repeat.

Receptors zinc finger domains help recognise these sequences.

Question 14

Are nuclear receptors similar in structure?

Answer 14

Have high homology in the DNA binding domain and a structure which is activated by ligand binding

differ in ligand binding domains and in N-terminal activation domains

Question 15

Breast tissue is responsive to oestrogen

Describe the breast and what it is composed of

Answer 15

Aprocrine gland, produces milk

Composed of glands and ducts which produce fatty breast milk

milk producing part of breast is organised into 15-20 sections - lobes

within each lobe is smaller structure, lobules, where milk is produced

milk travels through tiny tubes, ducts, which come together into larger ducts and eventually exist skin in nipple

Question 16

Wha does exocrine gland do?

Answer 16

Secretes substances out onto a surface or cavity via a ductal structure

Question 17

What does endocrine glands do?

Answer 17

Secrete substances directly into bloodstream

Question 18

What type of gland is an apocrine gland?

Answer 18

Specialised exocrine gland in which part of a cell’s cytoplasm breaks off, releasing the contents.

Question 19

Mammary epithelium consists of two cell compartments

Answer 19

Luminal – form a single layer of polarised epithelium around the ductal lumen, luminal cells produce milk during lactation

Basal – comprise of the cells that do not touch the lumen, basally oriented myoepithelial cells in contact with the basement membrane, have contractile function during lactation

myoepithelial (basal) on outside, luminal face in towards lumen.

Question 20

What are the two major phases in mammary gland development?

Answer 20

Hormone-independent from embryonic development up to puberty

Hormone-dependent thereafter during puberty, menstrual cycle and pregnancy

Question 21

What does estrogen do in adults?

Answer 21

Estrogen drives expression of genes involved in cellular proliferation and differentiation.

In adults allows for maintenace of mammary gland tissue + primes tissue for effects of progesterone during pregnancy for milk production

Question 22

What does progesterone cause in the breast?

Answer 22

Progesterone receptor gene switched on by oestrogen receptor.

Progesterone increases branching of the ducts (estrogen determines growth of ducts)

Prolonged progesterone receptor activity (e.g during pregnancy) leads to more side branched and lactogenic differentiation (with prolactine hormone)

Question 23

What is the aetiology of breast cancer?

Age

Genes implicated

Answer 23

Age - risk increases with age, most diagnosed after 50

Genetic mutations in BRCA1 and 2, inherting these genetic changes = higher risk of breast and ovarian cancer

Reproductive system - early onset of menstrual cycle before 12 and menopause after 55, exposed to hormones longer

previous treatment using radiation therapy - higher risk

Not physically active, overweight

Taking hormones, oral contraceptives increase risk

first pregnancy after 30, not breastfeeding

alcohol

Question 24

What is ductal breast carcinoma in situ (DCIS)?

Answer 24

Breasts are made up of lobules (milk-producing glands) and ducts (tubes that carry milk to the nipple), surrounded by glandular, fibrous and fatty tissues

Cancer cells develop within the ducts of the breast but remain within the ducts (in situ), it is called DCIS.

Question 25

What is lobular breast carcinoma in situ (LCIS)

Answer 25

Lobular carcinoma in situ (LCIS) , uncommon condition in which abnormal cells form in the milk glands (lobules) in breast 

LCIS isn’t cancer.

Being diagnosed with LCIS indicates that there could be an increased risk of developing breast cancer

Question 26

Majority of breast cancer arises from which cells?

Answer 26

Luminal cells, express estrogen receptor.

Luminal epithelial cells are inside lumen

Sit on layer of basal myoepithelial cells that are in contact with basement membrane.

Question 27

What is the difference between ER positive and negative ER breast cancers?

Answer 27

Majority are ER positive - good prognosis

ER negative - poor prognosis

ER negative breast cancers can’t be treated hormonally and patients given more conventional therapies

ER negative breast cancers develop from other cells like basal cells

Question 28

Breast cancer subtypes

Why can progesterone receptor be used as an indicator of estrogen acitvity?

Answer 28

Because it is estrogen dependent gene.

Progesterone target for cancer therapy in some subtypes, may reduce cell growth.

Question 29

Why is ER targeted in breast cancer treatment?

Answer 29

Mammary gland is estrogen sensitive and dependent

Estrogen key driver of breast cancer growth

Therefore can be used for treatment, switch off ER signalling and cancer growth

• ER targetting is Achilles heel of breast cancer

Question 30

What is the normal action of estrogen?

Answer 30

Estrogen binds to receptor at ligand binding site

Estrogen receptor dimerses, translocates into nucleus

binds DNA and recruits in proteins for gene transcription e.g co-activators, chromatin modifiers, RNA polymerase.

Activation domains, AF1 and AF2 activated, triggering gene activation, drives cell growth and cancer growth forward.

Question 31

How is estrogen action inhibited?

Answer 31

competitively blocking estrogen binding to receptor - and degrading ER protein.

No ER signal = no breast cancer cell growth

Question 32

How does fulvestrant (faslodex) work?

Answer 32

Analogue of estradiol

Completely inhibits binding of estradiol to ER, binding affinity that is 89% that of estradiol

Binding to ER impairs receptor dimerisation

receptor translocation into nucleus (nucleo-cytoplasmic shuttling) and blocks it from working / blocks nuclear localisation of receptor

fulvestrant-ER complex transcriptionally inactive because AF1/2 disabled

fulvestrant-ER complex unstable, results in accelerated degradation of ER protein

= no estrogen receptor activity and gene transcription

Question 33

How does tamoxifen work as a treatment for breast cancer?

Answer 33

Binds to ligand gated binding site, causes ER to become partially active

Binding causes conformation change in the ER, causing only one of the activation domains to become active, AF1.

AF2 domain not active.

ER remains partially inactive. Stops ER activity within breast tissue and cancer cells

However doesn’t stop ER activity in other tissues like liver and uterus

Mechanism is highly complicated, may be due to types of coactivators present in those tissue types

Question 34

What does the aromatase enzyme do in the ovaries?

Answer 34

When ovaries aren’t functional in postmenopausal women, estrogen can come from peripheral conversion of androgens via aromatase enzyme.

present in multiple organs - adipose tissue, brain, blood vessels, skin, bone, breast tissue

Question 35

What are the types of aromatase inhibitors?

Answer 35

Type 1 like exemestane (aromasin)

• androgen analogues, bind irreversibly to aromatase

Type 2 like anastrozole (Arimidex)

• contains functional group within ring structure
• binds heme iron of cytochrome P450, interfering with hydroxylation reactions

Question 36

What is the main function of the prostate?

Answer 36

Produce prostatic fluid which creates semen when mixed with sperm produced by testes.

Prostate gland under bladder, an exocrine gland composed of glandular tissue

Question 37

What type of gland is the prostate gland?

Answer 37

Specialised exocrine gland called apocrine gland (and merocrine)

Apocrine gland is specialised exocrine gland in which part of the cell’s cytoplasm breaks off releasing the contents

Question 38

What phases can prostate development be separated into?

Answer 38

Hormone independent from embryonic development up to puberty

enlargement during puberty

Hormone dependent maintenance therafter in adulthood

Reactivation of prostate gland in old age - leads to hyperplasia and prostate cancer

Question 39

What prostate abnormalities can occur?

Answer 39

Inflammation e.g due to infection

• Prostatitis linked to infertility

Dysregulated growth of prostate

• Benign: prostate hyperplasia (BPH)
• Malignant: prostate cancer

Question 40

What are the symptoms of prostate cancer?

Answer 40

Frequent trips to urinate

Poor urinary stream

Urgent need to urinate

Lower back pain

Hesitancy whilst urinating

Blood in the urine (Rare)

tumour pass of prostate cancer squeezes and presses urethra, puts pressure on bladder

Question 41

In what cells does prostate cancer start?

Answer 41

Luminal epithelial cells.

Hypoproliferate to form prostate intraepithelial neoplasia / PIN

became invasive adenocarcinoma

prostate cancer grows and divides rapidly, filling lumen, then begins to inavde outward from prostate

Question 42

How is prostate cancer detected?

Answer 42

1. Digital rectal examination (DRE)
2. PSA test, if prostate is damaged or overgrown, the prostate specific antigen can escape into the blood where it can be measured with an immune test - blood sample, antibody based assay
3. Ultrasound - to detect tumour outside prostate capsule

Question 43

What are the different stages and grading of prostate cancer?

Answer 43

T1: small, localised tumour – lowest on scale

T2: palpable tumour by digital rectal exam

TNM – t for tumour, n is for number of lymph nodes involved in cancer, M for if cancer has metastasised or not

T3: escape from prostate gland, tumour is larger, grows outside of prostate gland

T4: local spread to pelvic region, tumour grown outside of prostate and involves other surrounding organs

Question 44

What is the grading for N+ tumour in lymph nodes?

Answer 44

N0 = no cancer cells found in any lymph nodes

N1 = 1 positive lymph node <2cm across

N2 = >1 positive lymph node or 1 between 2-5cm across

N3 = Any positive lymph node >5cm across

Question 45

What is the metastasis grading for prostate cancer?

Answer 45

M1a = Non-regional lymph nodes

M1b = Bone

M1c = other sites

Question 46

What is the gleason grading system?

Answer 46

The Gleason grading system is used to help evaluate the prognosis of men using prostate biopsy samples

The samples are examined by a clinical histologist

Prostate cancer staging predicts prognosis and helps guide therapy

Cancers with a higher Gleason score are more aggressive and have worse prognosis

Question 47

How is prostate cancer treated?

Answer 47

Watchful waiting - low grade tumour, older patients , tumour may never advance enough to be any concern to them.

Radical prostatectomy – stage T1 or T2 (confined to prostate gland)

Radical radiotherapy - external up to T3 (spread past capsule). Internal implants (brachytherapy) for T1/2

Hormone therapy +/- prostatectomy or radical radiotherapy for metastatic prostate cancer

Question 48

What are the risk factors of prostate cancer?

Answer 48

Age - rare in men younger than 40, risk rises after 50

Race/ethnicity - more in african-american men and carribean men. less in asian america, latino men

Geography - common in north america, austrial, north-western europe. less common in asia, africa, central and south america - due to lifestyle difference

Family history - having father or brother with prostate cancer more than double’s risk of developing disease

Gene changes/inherited - inherited BRCA1/2 gene muations linked to increase breast/ovarian cancer also increases risk of prostate cancer. Lynch syndrome.

General risks - diet, obesity (lower risk of low grade cancer, higher risk of aggressive cancer), chemical exposures, inflammation of prosate

Question 49

What genes are associated with prostate cancer?

Answer 49

BRCA1 mutations and PTen loss.

PTen is a phosphatase that antagonises the phosphatidylinositol 3-kinase signalling pathway.

PTen is the only known 3’ phosphatase counteracting the P13K/AKT pathway (that normally leads to cell growth).

Loss of PTen results in increased growth factor signalling – inappropriate cell growth and proliferation

Question 50

What does TMPRSS2-ERD fusion cause?

Answer 50

Present in 40-80% of prostate cancers

promoter of the gene is fused with proto-oncogene ERG, strong proliferation signal driven by testosterone

AR now drives proto-oncogene ERG, leads to inappropriate gene activation

Question 51

What hormone is growth and development of prostate gland dependent on?

Describe androgen receptor signalling

Answer 51

Androgens, most common is testosterone.

AR located in cytoplasm

testosterone converted to more potent agonist as it crosses into prostate, dihydrotestosterone, by 5-a-reductase then binds to AR with high affinity

AR activated, dimerised.

AR translocates into nucleus where it binds to androgen response elements (Specific DNA sequences in promoter regions of androgen target genes)

Recruits in gene transcription machinery + coactivators needed for expression of target gene

Leads to target protein generation and cell growth

Question 52

What agent inhibits the enzymes needed to produce androgens in the body?

Answer 52

Abiraterone inhibits two main enzymes.

Has similar structure to cholesterol and steroid intermediates

In prostate cancer can swich off production of adrenal androgens, reduces overalll level of testosterone in body

Question 53

How is hormone production controlled?

Answer 53

Gonadotrophin releasing hormone secreted from hypothalamus targets pituitary to release LH and FSH.

Circulate in blood, reach target tissue the testes, stimulating them to produce more testosterone.

Hypothalamus will then be sensitive to circulating testosterone hormone

Stop production of LH and FSH if testosterone levels are sufficient.

If not hypothalamus secretes more hormones.

Question 54

How can the feedback loop of testosterone production be intercepted?

Answer 54

Goserelin – super agonist

Abarelix – antagonist

Shut down the hypothalamus to pituitary and testes signalling, reducing testosterone production.

Overall the actions of superagonists and antagonists are similar – they depress testosterone production in the testes

Question 55

How do competitive androgen antagonists inhibit DHT binding to AR?

Answer 55

Competitive androgen antagonists. Compete with testosterone for the ligand binding site on the AR, causing it to not fold or be completely active.

• Bicalutamide.
• Enzalutamide
• Flutamide
• Nilutamide

All compete with testosterone for the ligand binding site within the androgen receptor.

in the presence of androgen antagonist , it binds to ligand binding site and stops H12 from folding over, keeping the receptor inactive.

Question 56

Why do hormone therapies stop working?

Answer 56

Patient relapses with hormone refractory cancers.

Cancer cells develop mechanisms to overcome hormonal starvation.

Resistance mechanisms quickly selected for, cancers adapt to low levels of hormones.

some advanced tumours synthesis own steroid hormones, leads to autocrine stimulation.

Question 57

Explain ligand binding site mutations

Answer 57

Some receptors for steroids acquire ligand binding site mutations, makes the binding sites less specific for the hormone.

Receptor is said to be promiscuous.

so if you target testosterone for prostate cancer, ligand binding site mutations in receptor may allow it to bind estrogen or cortisol, allowing cells to grow.

Question 58

Explain receptor amplification

how cancer adapts resistance to hormonal therapies

Answer 58

Signal amplification and increased sensitivity to low hormone levels.

Steroid receptors themselves or genes expressing them are amplified, causes increased amount of receptor in the cell.

Leads to signal amplification from low hormone level.

Question 59

Explain receptor phosphorylation / activation in absence of ligand

Answer 59

Cross over with other signal pathways e.g growth factors can phosphorylate and activate receptors nappropriately in the absence of ligand– prevalent for breast cancer

In the absence of hormone steroid receptor can bind to DNA and activate target genes.

Question 60

Explain how androgen receptor transcript variants can be activated in the absence of ligands

Answer 60

Generaton of variants of nuclear receptor

some types of prostate cancer the AR can be expressed as a shorter, transcript variant, ARV7.

A truncated version of AR without C terminus in ligand binding domain.

Active without ligand in prostate cancer.

Can bind to DNA and trigger target gene activation without a ligand being present in the cell.

Question 61

Explain receptor cofactor amplification

Answer 61

Cofactors recruited by hormone receptor to DNA to help activate target genes.

Cofactor amplification can amplify the signal from steroid receptors in response to a low level of steroid hormone.

Antagonists become agonists via LBD mutations

Question 62

How can antagonists used for prostate cancer treatment become potent activators of mutant AR?

Answer 62

AR can acquire mutations in its ligand binding domain, allow antagonists to function as an agonist.

Antagonist fits in ligand binding domain and activates receptor.

Antagonists used for prostate cancer treatment can become potent activators of a mutant androgen receptor.

So sometimes patients can benefit with having therapy withdrawn.