Oncologic Endocrine Therapies (Wendt) Flashcards
Give three examples of hormone-dependent cancers.
breast cancer, prostate cancer, endometrial cancer
What hormone is the prime target in breast and endometrial cancers?
estradiol
What hormone is the primary target in prostate cancer?
dihydrotestosterone
List the steps of molecular action for steroid hormones.
- Most hydrophobic steroids are bound to plasma protein carriers. Only unbound hormones can diffuse into the target cell.
- Steroid hormone receptors are in the cytoplasm or nucleus.
- The receptor-hormone complex binds to DNA and activates or represses one or more genes.
- Activated genes create new mRNA that moves back to the cytoplasm.
- Translation produces new proteins for cell processes.
- Some steroid hormones also bind to membrane receptors that use second messenger systems to create rapid cellular responses.
What are the two ways in which endocrine therapies can inhibit steroid signaling?
- Stop steroid receptor function
- Decrease production of steroids
Which two receptors are measurable in breast cancer tumors?
estrogen and progesterone receptors (ER and PR)
Well-differentiated tumors are more likely to be ____, while poorly differentiated tumors are generally ____.
ER+; ER-
Which tumor grade are more sensitive to cytotoxic agents?
poorly differentiated tumors
The presence of which receptor strongly correlates with the likelihood of response to hormone therapy?
estrogen receptor (ER)
*even stronger correlation for ER+/PR+ tumors*
PR is ________ inducible and is a measure of biological response to _________.
estrogen; estrogen
True or false: hormone therapy in breast cancer is generally limited to ER+/PR+ tumors
true
How is hormone therapy typically used in ER+/PR- breast cancer?
as an adjunct to other chemotherapy
Which hormone is produced in the pituitary gland?
LH
Estrogen receptors primarily bind estrogen where in the cell?
in the cytoplasm
What enzyme converts androstenedione to estrone?
CYP19
What are the 4 molecular subtypes of breast cancer?
- Triple negative (ER-/PR-/HER2-)
- HER2+
- Luminal A
- Luminal B
What molecular subtype makes up the majority of breast cancers?
luminal A
Identify the drug based on its structure.
Tamoxifen (Nolvadex)
Identify the drug based on its structure.
Toremifene (Fareston)
Identify the drug based on its structure.
Clomiphene (Clomid)
Identify the drug based on its structure.
Fulvestrant (Faslodex)
Identify the drug based on its structure.
Raloxifene (Evista)
What SERM is a prodrug that must be metabolized to 4-OH-TAM?
Tamoxifen
Describe the pharmacologic actions of Tamoxifen (agonist or antagonist).
both agonist and antagonist
Which CYP converts tamoxifen to high-affinity hydroxylated and demethylated metabolites?
CYP2D6
What are the consequences of Nolvadex binding to estrogen receptors?
inhibits translocation and DNA binding
What estrogen agonist effects are seen with tamoxifen?
- 3-fold increase in incidence of endometrial cancer
- Preservation of bone density in postmenopausal women
What estrogen antagonist effect is seen with tamoxifen?
hot flashes
Regarding menopause, which group(s) is tamoxifen effective in?
both pre- and postmenopausal women
What is tamoxifen’s PRIMARY indication?
resected ER+/PR+ breast cancer (3-5 years Rx)
Besides resected ER+/PR+ breast cancer, what is tamoxifen also used to treat?
metastatic ER+/PR+ breast cancer
What was the first drug approved for breast cancer prevention?
Tamoxifen (Nolvadex)
Tamoxifen is known to be much less effective in which patients?
those with a common CYP2D6 variant
What beneficial uterine effect does raloxifene have (differs from tamoxifen)?
NO endometrial hyperplasia
What drug class does fulvestrant (Faslodex) belong to?
selective estrogen receptor down-modulator (SERD)
What drug is considered to be a “pure” ER antagonist with NO agonist effects?
fulvestrant (Faslodex)
What happens after Faslodex binds to ER and inhibits DNA binding?
rapid receptor degradation
What indication is fulvestrant (Faslodex) approved for?
treatment of metastatic ER+ breast cancer in postmenopausal women whose cancer has progressed on other antiestrogen therapy
What is one possible explanation for the relative lack of cross-resistance that Faslodex has with other antiestrogens?
it has the same target (ER) but different mechanism (receptor degradation)
What is fulvestrant’s route of administration?
IM injection once a month
What characteristic of fulvestrant limits its effectiveness?
poor solubility
What does aromatase do?
- catalyzes the demethylation of the enone ring of androgens to the aromatic ring in estrogens
- converts androstenedione ➝ estrone and testosterone ➝ estradiol
Aromatase inhibitors block the synthesis of which hormone?
estrogens
Where does estrogen originate from in postmenopausal women?
adipocytes
The primary target of aromatase inhibitors is not the ovary but _________.
peripheral (adipose) tissue
What is the primary application of aromatase inhibitors?
estradiol suppression in postmenopausal women