Cancer as a Disease – Breast Cancer Flashcards
What is special about the breast as an organ?
It’s the only organ that develops after birth
Where do the vast majority of breast cancers originate?
Luminal epithelium of the breast (> 90%)
Describe the two layers of epithelial cells in the mammary gland.
Luminal epithelium
Myoepithelium
What is found between the tubules in the mammary gland?
Fatty stromal cells
What is special about the myoepithelial cells?
They have a contractile property, thus can squeeze the luminal epithelial cells when full of milk globules in lactation
Where are oestrogen receptors expressed in the breast?
ONLY expressed by luminal cells
Not all luminal cells express oestrogen receptors (only ~ 10)
Describe the response to oestrogen in a normal breast.
Response to oestrogen is to stimulate growth
Cells that express oestrogen receptors do NOT grow in response to oestrogen
Act as a beacon + produce growth factors that stimulate the growth of nearby cells
How is the response to oestrogen different in breast cancer?
Cells displaying oestrogen receptors directly respond to oestrogen as a growth factor + stimulate their own growth
What is the difference between lobular and medullary carcinoma?
Lobular: tumour has some resemblance of the architecture of the gland (tubules of some form)
Medullary: tumour cells don’t look anything like the epithelial cells from the mammary gland
What specific type of breast cancer accounts for almost 85% of breast cancers?
Infiltrating ductal carcinoma
What percentage of breast cancers is ER positive?
80%
State 7 risk factors for breast cancer.
Early age of onset of menstruation Late age to menopause Age to 1st full-time pregnancy Some contraceptive pills Some HRT Obesity Diet
Where is the oestrogen receptor normally located?
Cytosolic receptor
Bound to a heatshock protein
What happens when oestrogen binds to ER?
Oestrogen binds to ER + then 2 ERs dimerise + translocate to the nucleus (with oestrogen bound)
Dimer binds to oestrogen response elements in the DNA sequence + regulates transcription
What are the 4 most important target genes for the ER transcription factor?
Progesterone receptor
Cyclin D1
c-myc
TGF-alpha
Why does high dose therapy with synthetic oestrogens cause breast tumour regression in post-menopausal women with breast cancer?
High-dose therapy overstimulates the hormonal system leading to downregulation of ER so the cells are no longer responsive to oestrogen
How does the presence of ER affect prognosis?
GOOD prognosis in women
Worse prognosis in male breast cancer
What are three methods of reducing oestrogen action in the breast?
Ovarian suppression
Blocking oestrogen production by enzymatic inhibition
Inhibiting oestrogen responses
At what point during the menstrual cycle is oestrogen at its highest?
End of the follicular phase
How do post-menopausal women make oestrogen? Where does this occur?
Aromatisation of androgens Fatty tissue (+ liver + muscles)
What are 2 methods of ovarian ablation?
Surgical oophorectomy
Ovarian irradiation
What are the problems associated with Surgical oophorectomy and Ovarian irradiation?
They are irreversible
Describe a reversible and reliable medical ovarian ablation technique.
LHRH agonists bind to LHRH receptors in the pituitary leading to receptor downregulation + suppression of LH release + inhibition of ovarian function, including oestrogen production
Name an important ER receptor blocker.
Tamoxifen
What is a SERM?
Why is tamoxifen considered a SERM?
Selective oestrogen receptor modulator
Anti-oestrogenic in the breast
Oestrogenic in bone + cardiovascular system
Name a drug that is a pure anti-oestrogen, showing no oestrogen like activity at all. What are the negatives of this drug?
Faslodex
Blocks oestrogen everywhere in the body, thus increases risk of osteoporosis + CVD
What is raloxifene?
A SERM: it is oestrogenic in bone + anti-oestrogenic in the breast + uterus
What are the problems associated with tamoxifen?
Increased incidence of endometrial cancer (oestrogenic in the uterus)
Increased risk of stroke, DVT, cataracts
Which adrenal hormones are aromatised in post-menopausal women?
Androstenedione (+ testosterone, to a lesser extent)
What does the aromatase complex produce from androstenedione?
Oestrone Sulphate
What does the aromatase complex consist of?
cytochrome P450 heme containing protein
NADPH cytochrome P450 reductase
What are the two types of aromatase inhibitor?
Irreversible
Reversible
How do Irreversible aromatase inhibitors work?
Bind to active site of aromatase complex
Causes formation of alkylating species + covalent bonds
Irreversibly inactivates the enzyme
Give an example of an aromatase inhibitor
Exemestane
Give an example of a reversible aromatase inhibitor.
Anastrozole
What can progestin therapy be used for?
Metastatic breast cancer
What is the main progestin used for metastatic breast cancer?
Megestrol acetate
What is a big problem with endocrine therapy?
Resistance develops
Relapse occurs
Women in which age range are targeted for breast cancer screening? How often are they asked to go for screening?
50-64 yrs
Every 3 years
What proportion of breast tumours are first spotted by the women themselves?
> 90%
What may have contributed to the rising incidence but falling mortality of breast cancer?
Early diagnosis (public health message to self examine)
Chemo/ Radiotherapies can now be more focussed + effective
Availability of hormonal therapies
What is the major treatment approach to breast cancer?
Surgery
Followed by chemo/ radiotherapy
What is given as adjuvant therapy for breast cancer?
Endocrine therapy
Kills any tumour cells that broke away from the tumour mass/ weren’t removed in surgery
What are the 3 pathways of endocrine therapy?
Ovarian suppression (pre-menopausal)
Blocking oestrogen production by enzymatic inhibition
Inhibiting ER
How is oestrogen primarily made? (pre-menopausal)
Hypothalamus stimulates the pituitary through LHRH
Causes release of LH + FSH
Stimulates ovary to make large quantities of oestrogen
What is the most common side effect of Tamoxifen therapy?
Hot flushes
How do reversible aromatase inhibitors work?
Bind reversibly to active site, competing with androstenedione