Introduction To Hormone Dependant Cancers: Breast And Prostate Cancers Flashcards
What is a hormone?
Chemical messenger made by specialist cells and is released into the bloodstream to have an effect in another part of the body
Where are hormones produced?
- Pineal gland
- Hypothalamus
- Pituitary
- Thyroid
- Thymus
- Pancreas
- Adrenal cortex
What are the three groups of hormones?
- Steroids
- Peptide/proteins
- Modified amino acids/amine hormones
What are steroids synthesised from?
Cholesterol
Which tissue in the adrenal glands are steroid synthesised?
In the adrenal cortex
Name 5 different classes of steroids
- androgen (testosterone)
- estrogen (estradiol)
- progestogen (progesterone)
- corticosteroids (cortisol)
- mineralocorticoids (aldosterone)
Name the 2 most prevalent cancers in the UK
- breast
- prostate
Both tissues are heavily influenced by steroid hormones - these tissues are hormone dependant. So the cancer can also be dependant on hormones.
What are steroid response elements - describe their structure?
Specific sequences in the DNA on promoters where the steroid-receptor complex binds to. So the steroid + receptor complex acts as a TF.
- many are palindromic repeats
- hormone response elements for estrogen are called estrogen response elements etc.
Name the 3 domains in all steroid nuclear receptors
- LBD - ligand binding domain
- DBD - DNA binding domain
- AF1 and AF2 - activation function domain
What is the function of the AF1 domain?
Activation function domains -
Recruits gene activation machinery, some receptors have AF2 further towards the C terminal
Describe the general mechanism of steroid receptors
- This is after the ligand binds to LBD that changes its structure to activate it.
- Also, some of the receptors will dimerise.
- Hormone responsive genes can be downregulated or upregulted and many hundreds of genes can be regulated by a steroid receptor
What are sex hormones responsible for?
Sexual dimorphism between males and females and development of secondary sexual characteristics
What are the effects of female sex steroid hormones?
Oestrogen controls the menstrual cycle and breast tissue development, fertility and reproductive organ development
What are the effects of male sex steroid hormones?
Testosterone controls reproductive and supportive organs (prostate) and development of secondary characteristics
Why are breast/prostate cancer the most commonly diagnosed?
- Tissues are hormone dependant
- Steroids control several aspects of cellular proliferation, tissue function, gene expression and morphology
What is the steroid mechanism of action?
- Enters cell and binds to cytoplasmic receptor
→ Conformational change in the receptor (causing it to become activated) → dissociated from the cytoplasmic proteins and translocates into the nucleus
→ receptor binds to DNA promoter regions and act as transcription factors and induces gene expression
What are the key characteristics of a nuclear receptor?
- Ligand binding domain
- DNA binding domain
- Activation function domain
- Ligand activated
What does the ligand binding domain of a nuclear receptor do?
Binds specific steroids with a high affinity
What does the DNA binding domain of a nuclear receptor do?
Binds specific DNA sequences
What does the activation function domain of a nuclear receptor do?
Recruits gene activation machinery, some receptors have a secondary af2 domain towards the c-terminal
What does ligand binding to the ligand binding site cause?
A shift in the alpha helix, which activates the receptor
How are hormone responsive genes controlled?
Up or down regulated by steroid hormones
What are hormone response elements?
Specific DNA segments found in the promoters of hormone response genes
What are hormone response elements made up of?
6 bases, 3 spacer DNA bases, 6 bases
How many genes are contained in the nuclear receptor superfamily?
48
What do the nuclear receptor superfamily share?
Common domain receptor structure
What does the main steroid receptor depend on?
The thing they bind
What is a zinc finger domain?
Zinc finger, binds to hormone response elements:
- CI Zinc finger
- CII Zinc finger
Describe the function of CI Zinc finger?
specific DNA sequence binding
Describe the function of CII Zinc finger
interaction with the DNA phosphate backbone
What is the breast?
Breast is an apocrine gland that produces milk
What is the mammary gland tissue composed of?
Glands and ducts that produce fatty breast milk
What is the type of the gland that produces milk?
Apocrine gland
What is the milk producing part of the breast organised into (and what are they called)?
- 15-20 sections called lobes
- within each lobe is lobules, where milk is produced
What does milk travel through in the breast?
Networks of tiny tubules called ducts
What does an exocrine gland do?
Secretes substances out onto a surface or cavity via a ductal structure
What does an endocrine gland do?
Secrete substances directly into the bloodstream
What is an apocrine gland?
Specialised exocrine gland in which a part of the cell’s cytoplasm breaks off, releasing the contents
Describe the 2 cell types in the mammary gland
- Luminal
- Basal
What is the function of the luminal cells in the mammary gland?
Luminal cells form a single layer of polarised epithelium and the ductal lumen
What do luminal cells produce (And when?)
Milk during lactation
What is the basal mammary gland tissue structure?
Comprise the cells that do not touch the lumen and basally orient the epithelial cells in contact with the basement membrane
What are the two major phases in mammary gland development and when do they happen?
- Hormone independant (embryonic → puberty)
- Hormone dependant (after puberty)
What does hormone dependant mammary gland development cause?
Ductal elongation and side branching
In an adult what does estrogen allow for in the breast?
Maintenance of mammary gland tissue and primes it for the effects of progesterone during pregnancy for milk production
Describe the differing effects of oestrogen, progesterone and prolactin on the ducts in the mammary glands (think about their roles in the endometrium)
- Oestrogen causes ductal elongation (so mostly growth?)
- Progesterone causes ductal elongation and side branching (differentiation?)
- Prolactin causes alveogenesis and lactogenic differentiation
What is the aetiology of breast cancer (not including normal cancer ones)?
- genetic mutations such as BRCA1 and BRCA2
- reproductive history (early onset of menstrual cycle before 12 years and starting menopause after 55 years means that women are exposed to hormones for longer)
- previous radiotherapy to the chest
- taking hormones including certain oral contraceptives
- first pregnancy after 30,
What facets of the reproductive history increase the chance of breast cancer?
- Early menstrual cycle onset (before 12)
- Menopause after 55
What is meant by DCIS?
DCIS = ductal carcinoma in situ
What causes a ductal breast carcinoma in situ (DCIS)?
- This is when cancer cells develop in the ducts and remain in the ducts