Introduction to Hormone-Dependent Cancers (Breast/Prostate) Flashcards
What are hormones?
Hormone = A Chemical messenger produced by specialised cells usually within an endocrine gland and it is released into the bloodstream to have an effect on another part of the body.
Hormones can be chemicals/peptides/proteins
Where are hormones produced? - Endocrine Glands
Brain:
Pineeal gland , Hypothalamus and Pituitary
Thorax:
Thryoid gland and Thymus gland
Abdomen:
Pancreas, Kidney, Adrenal cortex
(stomach,liver,intestines)
Testes (Male)
Ovaries+Uterus (Female)
slide 4
How can hormones be classified ?
Steroid hormones - Small, lipid-soluble molecules (testosterone)
Peptide/protein hormones (insulin)
Modified amino acid/amine hormones (adrenaline)
What are steroid hormones ?
Steroid hormones = small, lipid-soluble molecules synthesised from cholesterol in adrenal cortex
All steroid hormones have a basic backbone 4-ring structure (of cholesterol).
Cholesterol is converted to biosynthetic precursors in adrenal cortex
Cholesterol – Adrenal cortex – Gonadal tissues
Outline the process of steroid synthesis
Cholesterol
In the adrenal cortex (secretes primary hormones):
Main corticosteroids and mineralocorticoids synthesised in the adrenal cortex
Androgenic and estrogenic precursors are released into the blood stream (less potent forms of the final hormone)
Gonadal tissues:
Androgens and oestrogens produced in target organs e.g. testes and ovaries take up less potent hormone which produce active hormone (oestrogen, testosterone), then released into the bloodstream
What are some examples of steroid hormones ?
Steroid hormones:
- Androgen (male steroid) - Testosterone
- Estrogen - Estradiol
- Progestogen - Progesterone
- Corticosteroid - Cortisol
- Mineralocorticoid - Aldosterone
What are the sex steroid hormones?
Sex Steroid Hormones
Oestrogen (ovaries), Testosterone (testes).
These are responsible for:
Sexual dimorphism between males and females.
The development of the secondary sexual characteristics :
-Growth spurt
-Body hair growth
-Gonadal development
-Voice change
-Breast growth
-Accessory organs in the reproductive organs -prostate in men
How do steroid hormones work ?
They work systemically, have effects on several tissues simultaneously.
Females - Oestrogen controls menstrual cycle, breast tissue development, fertility, reproductive organ development , secondary sexual characteristics (body hair)
Males - Testosterone controls reproductive organs, supportive organs (prostate), development of sexual characteristics in men (deep voice, body hair)
What is the steroid hormone mechanism of action?
Steroid hormones = Small 4-ringed structure; Lipophilic molecules = easily enter cells by passing through plasma membrane
Once they enter the cell, steroid hormone binds to nuclear receptors; bind in cytoplasm + cause effects in nucleus
- The steroid hormone (lipophilic) circulates in the blood then enters the cell and binds to its nuclear receptor.
- Binding causes a conformational change in the receptor causing it to dissociate from cytoplasmic chaperone proteins and translocate into the nucleus .
- In the nucleus, Steroid-Receptor Complex binds to DNA at specific sequences called Steroid Response Elements (short sequences of DNA found in the promoter region of steroid responsive genes)
- Steroid receptor then functions as a transcription factor and recruits the gene transcription machinery, induces gene expression
slide 20, 21
What are the key characteristics of Steroid Nuclear receptor ?
Ligand binding domain (LBD) - Binds specific steroid molecules with high affinity
DNA binding domain (DBD) - Binds specific DNA sequences
Activation function domain (AF1 and 2) - Recruits gene transcription machinery , some receptors have a secondary AF2 domain towards the C-terminal
The same basic domains and structure are shared with many of the major nuclear recpetors
What happens when nuclear receptors bind steroid hormones ?
When these receptors bind steroid hormones they are activated = they are caled Ligand-Activated Receptors
-The binding of steroids to ligand binding domain causes a physical restructuring of the polypeptide chains (conformational change) in the receptor, activating it
What are ligand activated transcription factors ?
slides 24,25
Nuclear R = Ligand Activated Transcription Factor:
Ligand binds to nuclear R = R activates + dimerises + translocates from cytoplasm into nucleus + binds DNA specific sequences (Hormone Response Elements). On the DNA (promoter/Steroid-Responsive Gene), Receptor recruits gene activation proteins+chromatin modifiers to initiate gene transcription
The DNA binding domain contains ………….., which are essential for ……………
- 2 zinc fingers domains
- Nuclear receptor binding to the specific Hormone Reponse Element
4 cysteine residues = sulfur-containing aas, bind to Zinc atom, forming a zinc finger domain. 2 zinc finger domains in close proximity = required for specific DNA binding
1 steroid hormone receptor can ………….. genes
1 steroid hormone receptor can upregulate/downregulate many genes
Genes include functional tissue-specific genes , cell cycle and proliferation genes and genes involved in tissue development and differentiation
What are hormone response elements ?
Hormone Response Elements = Specific DNA sequences found in the promoters of hormone responsive genes.
Palindromic
How does nuclear R bind to DNA Hormone Response Elements?
DNA-Binding Domain of Nuclear R contains zinc fingers which recognise + bind to the specific Hormone Response Elements sequences
What is the Nuclear Receptor Super Family?
- 48 nuclear receptor genes
- Common domain structure
- Activated by ligand binding
slide 30,31
What are the main steroid receptors / ligands and abbreviations ?
- ER - Oestrogen R - oestradiol, oestrone, oestriol
- AR - Androgen R - testosterone, dihydrotestosterone, androstenedione
- PR - Progestagen R - progesterone, pregnenolong
- GR - Glucocorticoid R - cortisol, cortisone
- MR - Mineralocorticoid R - aldosterone
slide 32
Nuclear Rs have high homology in which domain?
Nuclear Rs differ in which domain?
DNA-binding domain = high homology
Ligand-binding domain = differ
Which steroid Rs for breast cancer?
Which steroid R for prostate cancer?
Breast cancer Steroid Rs - Oestrogen R (ER) + Progesterone R (PR)
Prostate cancer - Androgen R (AR)
The breast is an……….gland that produces …………..
The breast is composed of …………., which ……………
The milk-producing part of the breast is organized into …………………
Within each lobe are …………………………
The milk travels through ………………..
The ducts ………. and come together into ………….., which eventually ………….
apocrine milk for infants glands and ducts produce the fatty breast milk 15-20 sections (lobes). smaller structures (lobules), where milk is produced. a network of tiny tubes (ducts) connect larger ducts exit the skin in the nipple.
What are apocrine glands ?
The mammary gland is a specialised type of exocrine gland (apocrine gland)
Apocrine glands = specialised exocrine glands in which a part of the cell’s cytoplasm breaks off, releasing the contents
Endocrine glands - secrete substances directly into bloodstream
Exocrine glands - secrete substances out onto a surface via duct
What is exocrine glands ?
Secrete substances out onto a lumen/cavity/surface/onto skin via a duct
What is an endocrine gland ?
These secrete substances directly into the bloodstream
What are the 2 types of glands ?
Exocrine - Duct ,lumen cavity or into skin
Endocrine - Into the blood
What is the mammary gland tissue structure ?
Mammary epithelium consists of 2 cell compartments:
- Luminal - form a single layer of polarised epithelium around the lumen duct, luminal cells produce milk during lactation.
- Basal - the cells that don’t touch the lumen, basally orientated myoepithelial cells in contact with the basement membrane, contract milk outwards during lactation
slide 41
What are the 2 major phases in mammary gland (breast) development?
- Hormone-independent - from embryonic development up to puberty
- Hormone-dependent - thereafter during puberty, menstrual cycle and pregnancy
What is the function of oestrogen in the normal breast?
Estrogen (+growth hormone+cortisol) drives the expression of genes involved in cellular proliferation +differentiation of breast
Hormone-dependent mammary gland development occurs after puberty - oestrogen causes ductal elongation + triggers side branching.
In the adult, oestrogen maintains mammary gland tissue + primes the tissue for effects of progesterone during pregnancy - milk production
What is the normal progesterone activity in the normal breast
Oestrogen = primary initial growth of breast cancer
Progesterone receptor gene is switched on by oestrogen receptor.
It increases branching of the ducts
Prolonged activity - leads to more side branching and lactogenic differentiation (prolactin hormone)
slide 45+notes
Outline the changes in breast tissue by oestrogen +progesterone +prolactin
slide 45+notes
What is breast cancer ?
Breast cancer occurs when abnormal cells in the breast grow + divide in an uncontrolled way and eventually form a tumour
Breast cancer starts in the breast tissue most commonly in the cells which line the milk ducts of the breast
Main risk factors - Age, lifestyle (smoking, obesity), genetic familial factors
What is the Breast Cancer Aetiology ?
Age - Risk ↑ with age - mostly 50+yo
Genetic mutations to certain genes - BRCA1, BRCA2 - genes involving DNA repair. Inherit these mutations = ↑ risk breast+ovarian cancer
Reproductive history - Menstrual cycle <12 years + menopause >55 years = ↑ hormone exposure. First pregnancy 30yo+. Not breastfeeding. No full term pregnancy. ↑ breast cancer risk
Previous treatment using radiation therapy to the chest/breast (e.g.lymphoma) = ↑risk breast cancer
Not physically active
Overweight/Obese
Taking hormones - Hormone Replacement Therapy
Oral contraceptives
Alcohol
What is Ductal Breast Carcinoma In Situ (DCIS)
Breasts are made up of lobules (milk -producing glands) and ducts (tubes that carry milk to the nipple) -which are surrounded by glandular , fibrous and fatty tissue
DCIS = Cancer cells develop within duct + remain within duct. Cancer cells have not spread outside ducts into surrounding tissue
Outline Lobular Breast carcinoma in situ (LCIS)
LCIS = Abnormal cells form in the milk glands (lobules) in the breast.
Uncommon
Not breast cancer but ↑ risk
Where do majority of breast cancers arise?
Luminal cells which express ER.
What is ER(positive) and ER(negative)?
The majority of breast cancers are ER (+ve) which means they can be treated hormonally.
ER(-ve) however have a poor prognosis. Develop not from luminal cells but other cells (basal cells etc.). Cannot be treated hormonally. Chemotherapy.
Which cancer subtypes have better prognosis?
ER+ve/PR+ve breast cancer have a better prognosis
PR indicates that ER is active bc PR is oestrogen-dependent gene
PR - therapeutic target to treat breast cancer
How is oestrogen involved in breast cancer?
In normal breast, ER controls functions such as cell proliferation,development and differentiation in a highly controlled manner.
In breast cancer , ER signalling pathway is subverted and becomes uncontrolled.
ER ability to bind DNA and open chromatin stops working and is used to transcribe many genes , non-coding RNAS and miRNAS
ER then governs cancer cell proliferation + controls and influence many genes involved in metastasis, invasion +adhesion
How can we target ER in breast cancer and why ?
Mammary gland is ER-sensitive+dependent tissue
Breast cancer cells retain this sensitivity and dependency for oestrogen
Oestrogen = key driver of breast cancer growth
Switch off ER signalling = switch off the cancer growth
ER targeting is the Achilles heel of breast cancer (ER targeting)
How can we inhibit ER signalling ?
Biopsy samples are analysed for ER expression and 75% of breast cancers are ER +ve
Therefore these women are candidates for specific treatments that block ER activity
How can we stop oestrogen receptor from functioning ?
Oestrogen binds to its receptor at the ligand binding site which causes ER to dimerise and translocate into the nucleus where it binds DNA and recruits in proteins for gene transcription.
e.g.co activators ,chromatin remodifiers,RNA polymerase
Full activation of the ER: AF1 and AF2 are activated, triggering full gene transcription = cell growth - Breast cancer growth
How can we inhibit Oestrogen action ?
Pharmaceutically competitively blocking oestrogen binding to receptor - Degrading the ER protein
No ER signalling = no breast cancer cell growth
What is Fulvestrant (Faslodex)?
Fulvestrant is an analogue of oestradiol
Fulvestrant competitively inhibits binding of estradiol to the Oestrogen receptor with a binding affinity that is 89% that of oestradiol
How does Fulvestrant cause ER degradation?
Fulvestrant-ER binding impairs receptor dimerization and receptor translocation into nucleus = blocks ER from working.
+ Any fulvestrant-ER complex that enters the nucleus is transcriptionally inactive because both AF1 and AF2 are disabled.
The fulvestrant-ER complex is unstable, causing accelerated degradation of the ER protein
No gene transcription
Outline the mechanism of action of Tamoxifen
Tamoxifen binds to ER at the ligand binding site
Tamoxifen = partial agonist = does not cause full activation of ER.
Mixed activity - Activates ER in the uterus + liver. But acts as ER antagonist in breast tissue
Tamoxifen = Selective Estrogen Receptor Modulator (SERM)
Tamoxifen-bound ER does not fold properly and the AF2 domains do not function
Describe Tamoxifen bound ER
slide 65
What happens when Tamoxifen binds to the ER?
Tamoxifen binds to the ligand binding site and causes ER partial activation = conformational change = Only activates 1 of the activation domains (AF1).
ER remains partially active = stops breast tissue activity
slide 66
What are aromatase inhibitors?
When ovaries are no longer functional in post menopausal women , potential sources of estrogen come from the peripheral conversion of androgens by aromatase enzyme.
Aromatase enzyme is present in multiple organs - adipose tissue,brain,blood vessels ,skin ,bone, endometrium, breast tissue
Androgens = testosterone, adrenal androgens (androstenedione)
Low levels of Androgens are present in females
What is the mechanism of aromatase?
Aromatase converts oxygen (ketone, androgen) → OH(alcohol, oestrogen)
Androstenedione + aromatase = estrone
Testosterone + aromatase = estradiol
Aromatic group and alcohol differentiates estrogens and androgens
slide 68+notes
What are the 2 types of aromatase inhibitors ?
Type 1: Androgen analogues, bind irreversibly to aromatase (=suicide inhibitors). Duration of inhibitory effect depends on rate of de novo synthesis of aromatase. e.g. Exemestane
Type 2: Contain a functional group within the ring structure that binds the heme iron of the cytochrome P450 of aromatase, interfering with the hydroxylation reaction. e.g. Anastrozole
What is the main function of the prostate ?
Prostate function: Produces prostatic fluid that forms semen when mixed with the sperm produced by the testes
Where is the prostate gland located and what is it made up of ?
Located just under bladder in the abdomen
Exocrine gland, Apocrine gland
Composed of glandular tissue which produce a system of ducts that secrete the fluid
Composed of luminal epithelila cells which sit on basal epithelial cells.
Luminal epithelial cells line the duct
Ducts produce prostatic fluid and it then joins sperm+seminal fluid
What are the 3 phases of development of a normal prostate gland?
What can sometimes occur to prostate development in old age?
- Hormone-independent from embryonic development up to puberty
- Hormone-Dependent Enlargement during puberty
- Hormone dependent maintenance thereafter in adulthood
-Reactivation of prostate growth in old age = Hyperplasia, Prostate Cancer
What are some abnormalities of the prostate ?
Inflammation - due to infection. Prostatitis-Inferility
Dysregulated growth of prostate. Benign : Benign prostatic hyperplasia. Malignant: Prostate cancer
What are the symptoms of prostate cancer ?
- Frequent urination
- Poor urinary stream
- Urgent need to urinate
- Hesitancy whilst urinating
- Lower back pain
- Blood in urine
- Compressed urethra
bc prostate under bladder. prostate enlargement = presses on bladder. + urethra passes through prostate gland = compresses it, reducing urine flow.
Where does prostate cancer start ?
Originate in the luminal epithelial cells
- Luminal epithelial cells Hyperproliferates, forming prostateintraepithelial neoplasia (PIN)
- Then become Invasive Adenocarcinoma = Prostate cancer cells fill lumen and then invade outwards from the prostate
slide 84
How can we detect prostate cancer ?
- Digital rectal examination (DRE)
- PSA test-blood sample: Antibody based assay. Damaged prostate = PSA enters blood.
- Ultrasound of prostate gland - To detect tumour outside prostate capsule
Describe the process of prostate cancer staging
When prostate cancer is diagnosed;
Biopsy is carried out
to stage prostate cancer to guide treatment
TNM classification of malignant tumours:
T = Size of primary tumour
N=Number of lymph nodes involved
M= Metastasised or not - PET scan
T1: Small localised tumour
T2: Palpable tumour - DRE
T3: Tumour has escaped the prostate gland
T4: Local spread to pelvic region to surrounding organs (bladder, seminal vesicles)
What is N+ in prostate staging ?
N0= No cancer cells found in lymph nodes
N1+ 1 positive lymph node (<2cm across)
N2= ,1 positive lymph node or 1 between 2-5 cm across
N3=Any positive lymph node . 5 cm across
What is M+ metastatic ?
Has the cancer metastasised and where (PET scan detects this )
M1a =Non regional lymph nodes
M1b=bone
M1c =other sites
How can the biopsy sample of prostate cancer be graded ?
- Normal prostate - clear luminal structure, ordered tissue glandular morphology
- Hyperplasia - abnormal growth of prostate
- High grade carcinoma - disordered structure, cancer cells in lumen
As it progresses there is a loss of glandular structure + irregular structure
What is the Gleason grading system ?outline this
The Gleason grading system (1-5) = Helps evaluate patient prognosis using prostate biopsy samples
Prostate cancer staging predicts prognosis + guides treatment
Cancer with ↑ Gleason score = more aggressive and worse prognosis
What are the stages of the Gleason grading system?
slide 91
1.Small uniform glands (Well differentiated )
2.More stroma between glands
3.Distinctivly infiltrative margins
(Moderately differentiated )
4.Irregular masses of neoplastic glands
(Poorly differentiated /Anaplastic)
5.Only occasional gland formation
What are the different prostate cancer treatments ?
slide 92
What gene changes can increase risk of prostate cancer ?
Inherited BRCA1 /BRAC2 gene mutations
Men with lynch syndrome
What are some of the risk factors of prostate cancer ?
Age - risk ↑ with age Race - ↑ African-American Geography - ↑ Western countries Family history - BRCA1 gene ↑ prostate cancer risk Gene changes/inherited - BRCA1/BRCA1, Lynch syndrome Diet Obesity Chemical exposure - Firefighters Prostate inflammation - Prostatitis STIs - gonorrhea, chlamydia
What is the PTEN gene ?
PTEN = A phosphatase that antagonises the phosphatidylinositol 3 kinase signalling pathway (cell growth)
PTEN is the only known 3’ phosphatase counteracting the PI3K /AKT pathway
Loss of PTEN = ↑ growth factor signalling
Loss of PTEN = ↑ cell growth + proliferation
What is TMPRSS2_ERG fusion
TMPRSS2_ERG fusion = a fusion gene which is most frequent in prostate
TMPRSS2 = driven by Androgen Receptor Transcription Factor.
ERG = proto-oncogene
Fusion causes a strong proliferation signal, driven by testosterone
Outline the androgen receptor signalling (AR)
AR is located in the cytoplasm associated with many chaperone proteins
Testosterone is converted into a more potent agonist as it crosses into the prostate.
DHT binds the AR
testosterone is converted by 5-a -reductase .
DHT then bind s to the AR with higher affinity =dimerisation.
Translocation to the nucleus ,binds DNA in promoter regions
Coactivator recruitment
SLIDE
Each class of steroid binds to
a unique nuclear R
Prostate gland is …………-sensitive, …….-dependent
Most common androgen is …………., produced in ……………
androgen-sensitive
androgen-dependent
testosterone produced in testes
AR = nuclear R protein that binds testosterone.
Mechanism of action of ARA
Testosterone (lipophilic) circulates in blood, passes through plasma membrane. prostate cell converts testosterone → DHT(more potent) by 5-alpha reductase. DHT binds AR w high affinity = activates AR + AR dimerises. AR translocates into nucleus, where it binds specific DNA sequences (Androgen Response Elements) in Promoters of Androgen Target Genes. Recruit Gene transcription machinery + coactivators to express target gene -> target protein -> cell growth
What is the Achilles Heel of prostate cancer?
AR is the Achilles Heel of prostate cancer
Switch off AR signalling = switch off cancer growth
slide 116
Pathway of Testosterone Action in the Cell
- Adrenal glands: cholesterol -> androgen precursors
- Precursors circulate in bloodstream, reach testes. Testes: androgen precursor -> testosterone
- Testosterone circulates in blood, reaches prostate gland. Prostate gland: testosterone -> DHT (↑ potent)
- AR binds DHT, translocates into nucleus, binds DNA, recruits cofactors, causes gene transactivation = cell/tumour growth
slide 117
How to inhibit testosterone synthesis?
Inhibit adrenal androgen production = lack androgen precursors
Steroid Hormones – Reactions in adrenal cortex
How to use adrenal androgen reactions to inhibit AR?
Main androgen precursors produced: androstenedione, dihydroepiandrosterone. Formed in adrenal gland, then circulate in blood, then converted to testosterone in testes
Abiraterone inhibits androgen-producing enzymes
= no adrenal androgen production = ↓ testosterone
Tight control mechanism b/w brain +testes.
How to use this to ↓ testosterone production?
Hypothalamus secretes GnRH which targets pituitary, pit releases FSH+LH. FSH+LH circulate in blood, reach testes, stimulate testosterone production. –fb of testosterone on hypothalamus
Inhibit HPG axis – GnRH antagonist
= ↓ testosterone production
Inhibit testosterone -> DHT
- Inhibit testosterone -> DHT (more potent)
- 5 alpha-reductase inhibitor = Finasteride
- Resembles androgenic intermediate = stops DHT production in prostate
- Commonly used to reduce growth in Benign Prostate Hyperplasia (BPH)
Inhibit androgen-AR binding
Competitive Androgen Antagonists
Compete w testosterone for ligand binding site in AR
Bicalutamide
Testosterone binding = alpha-helix conformational change activates AR.
Androgen antagonist binding = no alpha-helix conformational change = inactive AR
slide 129
Prostate cancer requires ……… for growth
androgens - testosterone
go through ppt slides 132-143
