Cancer Chemotherapy Flashcards
What is the fractional cell kill hypothesis?
- Repeated doses of chemotherapeutic given
- Allows time for bone marrow cells to recover (recover more quickly) than tumour cells
- Get an overall reduction in tumour cells
What cancers are highly sensitive to chemotherapy?
- Lymphomas
- Germ cell tumours
- Small cell lung
- Neuroblastoma
- Wilm’s tumour
What cancers have modest sesnsitivity to chemotherapy?
- Breast
- Colorectal
- Bladder
- Ovary
- Cervix
Which tumours have low sensitivity to chemotherapy?
- Prostate
- Renal Cell
- Brain tumours
- Endometrial
How do different chemotherapeutic agents target cancer cells?
Explain how alkylating agents work
- Alkylating agent forms bond between 2 strands of DNA
- Cannot replicate at replication fork- induces double strand break
- Cell dies by apoptosis
How do Platinum compounds inhibit DNA replciation?
- Form inter and intrasand adducts → inhibits DNA synthesis
- Bulky adducts are difficult to repair
- Cells die
Explain the mechanism of action of 5-Flurouracil as a chemotherapy agent
- 5-FU inhibits thymidylate synthase
- Thymidylate synthase needed for the synthesis of folic acid
- Without folic acid- DNA and protein synthesis is reduced
Explain the mechanism of action of methotrexate
- Methotrexate inhibits dihydrofolate reductase
- Cannot form tetrahydrofolate so cannot form purines/ amino acids
Explain the mechanism of action of spindle poisons
- Spindles essential to move sister chromatids apart to opposite poles during mitosis
- Microtubule binding agents either:
- inhibit polymerisation
- stimulate polyermisate and prevent depolymerisation
Explain how Vinca alkaloids work
- Soluble alpha and betal tubulin normally form microtubule polymers
- Vinca alkaloid binds to the individual tubulins to prevent polymerisation
- Microtubules cannot form and DNA cannot replicate
Give an example of a vinca alkaloid
Vincristine
Explain how taxanes work
- Bind to the microtuble polymer and prevent its depolarisation
- Mitosis fails
Give an example of a taxane
Paclitaxel
Give 3 examples of how cells can develop resistance mechanisms to alkylating agents
- Decreased entry or increased exit of agent
- Inactivation of agent in cell → glutathione can mop up active moeity neutralising agent
- Enhanced repiar of DNA lesions produced by alkylation