Chemotherapy

Question 1

what is the site of action for alkylating agents?

Answer 1

they act directly on DNA

Question 2

describe the action of alkylating agents

Answer 2

alkyl groups form covalent bonds. In DNA they do this by attaching to free guanines. This forms X-links between strands (interstrand) or with in one strand (intrastrand). This prevents the DNA acting as a template for replication.

Question 3

what are the mechanisms of resistance to alkylating agents?

Answer 3

1. the cancer cells can develop pumps which cause the alkylating agent to be excreted, they may also decrease the ability of the alkylating agent to enter the cell.
2. the alkylating agent can be inactivated in the cell by reacting with chemicals.
3. the lesions caused by alkylating agents in the cell can be repaired

Question 4

what are the modes of action of antimetabolites?

Answer 4

mimic essential metabolites required by cell prior to cell division so they can:

1. be incorporated into nuclear material
2. bind irreversibly with vital enzymes to inhibit cell division

Question 5

which drugs interfere with spindles?

Answer 5

Vinca alkaloids

Taxanes

Question 6

what is the mode of action of Vinca alkaloids?

Answer 6

metaphase arrest agents; bind to tubuli and block microtubule formation and spindle formation (essential for metaphase of mitosis)

Question 7

what is the mode of action of taxanes?

Answer 7

promote spindles and prevent disassembly to ‘freeze’ cells at that stage of cycles

Question 8

modes of action of antimitotic antibiotics?

Answer 8

1. intercalate and inhibit DNA and RNA synthesis
2. membrane binding and increase permeability to various ions
3. free radicals disrupt DNA chain and prevent mitosis
4. metal ion chelation resulting in cytotoxic compounds
5. alkylation blocking DNA replication

Question 9

types of antimitotic antibiotics

Answer 9

anthracyclines and non-anthracyclines

Question 10

what must be kept in mind when using two chemotherapy drugs?

Answer 10

their toxicity, they must be dissimilar

Question 11

why are chemotherapies combined

Answer 11

• for synergistic or additive results

- to reduce the risk of resistance being developed

Question 12

mode of action for hormonal drugs

Answer 12

1. analogue of a hormone used

2. hormone inhibitor used eg. an anti-oestrogen drug for breast cancer

Question 13

how immunotherapy works

Answer 13

drugs are used to allow the immune system to recognise abnormal cells and destroy them