Cancer chemotherapy Flashcards Preview

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Flashcards in Cancer chemotherapy Deck (51):
1

what makes cancer cells special?

- uncontrolled proliferation
- loss of original function (anaplasia)
- invasiveness
- metastasis (malignant cells)

2

what are the treatments available for cancer?

- surgical removal
- irradiation
- chemotherapy with anticancer drugs

3

when is surgery used as a cancer therapy?

only:
- for solid tumours
- if non-metastasised

4

when is irradiation used as a cancer therapy?

only if localised

5

what is required to use chemotherapy as a cancer treatment?

selective toxicity

6

can the treatments be combined?

yes

7

what happens to a single cells after 30 doublings?

it gives a cell mass of 10^9 cells - 2cm in diameter
- detectable in skin or breast (80%)
- non-detectable in liver

8

how do normal cells become cancer cells?

through a change in DNA

9

what two main categories of genetic change are there?

- inactivation of tumour suppressor genes
- activation of photo-oncogenes to oncogenes

10

what is apoptosis of transformed cells?

- failed check points at cell division
- programmed cell death

11

what do most anticancer drugs do not do?

- de-differentiation
- invasiveness
- metastasis

12

what do cell cycle drugs attack?

only a subpopulation of the cancer cells

13

what are cell-cycle specific drugs?

drugs that are active only on dividing cells

14

what are cell-cycle non-specific drugs?

drugs also active on resting cells

15

what do solid tumours consist of?

- dividing cells - progressing through cell cycle
- resting cells - not dividing but could do so
- cells which can no longer divide but contribute to tumour size

16

what are dividing cells sensitive to?

cell-cycle specific drugs

17

what are resting cells insensitive to?

many drugs
also causes many relapses

18

how many chemotherapy drugs are there?

more than 90

19

what do chemotherapy drugs mainly affect?

cell division

20

what do anti-cancer drugs affect?

all rapidly dividing normal tissue

21

what are the general toxic effects?

- bone marrow suppression (red and white blood cells)
- loss of hair
- damage to gastrointestinal epithelium
- liver, heart, kidney
- in children, depression to growth
- sterility
- teratogenicity (damage to embryo)

22

what happens if a dose of chemotherapy drug kills 99.999% of all dividing cells in a tumour of 10^9 cells?

it still leaves 10,000 cells

23

what does chemotherapy drugs aim to?

total kill of these cells

24

why is it required a prolonged treatment?

to reduce chance of relapse from resting cells --> severe cumulative toxicity

25

what are the main classes of drugs?

- alkylating agents
- antimetabolites
- cytotoxic antibiotics
- microtubule
- steroid hormones and antagonists

26

what are alkylating agents?

- form covalent bonds with DNA
- interfere with both transcription and replication
- most alkylating agents have two reactive groups
- allow the drug to cross-link
· with one strand DNA
· across 2 strands of DNA

27

what are the types of alkylating agents?

- nitrogen mustards - derived from mustard gases
- cysplatin
- lomustine - can penetrate brain
- busulphan

28

what is mechlorethamine?

type of nitrogen mustard
- first anticancer chemotherapy drug
- blister agent
- used to treat Hodgkin's lymphoma, non-Hodgkins lymphoma
- highly reactive- must be given in vivo

29

what is melphan?

- fusion of mechlorethamine with phenylalanine (precursor of melanin)
- might accumulate specifically in melanomas
- more stable
- absorption and distribution possible without extensive alkylation
used to treat multiple myeloma, ovarian and breast cancer

30

what is cyclophosphamide?

- high phophoramidase activity in some tumours
- specific in situ activation in tumour cells
- prodrug, activated in liver
- much less toxic
- aldehyde dehydrogenase protects against drug - in bone marrow, hepatocytes and intestinal epithelium
- used to treat many cancers of tissues low in aldehyde dehydrogenase

31

what is cisplatin?

- targets N7 of purine nucleotides
- resistance from
· nucleotide excision repair mechanism
· efflux transporters for Copper

32

what are antimetabolites?

drugs that interfere with nucleotide synthesis or DNAa synthesis

33

what are the nucleotide synthesis (antifolates)?

methotrexate, ralitrexed, pemetrexed

34

what are the nucleotide analogues?

5-fluorouracil, cytarabine (Ara-C), gemcitabine, fludarabine, capecitabine

35

what are the types of antimetabolites?

- folate antagonists: methotrexate
- pyrimidine analogues: fluoro-uracil
- pruine analogues: mercaptopurines

36

what are folate antagonists?

- higher affinity for dihydrofolate reductase than folic acid
- inhibition of tetrahydrofolate formation
- inhibition of purine/pyrimidine synthesis
- ultimately, halt to DNA and RNA synthesis

37

what are pyrimidine analogues?

- prevents thymidine biosynthesis
- stops DNA synthesis

38

what are purine analogues?

- converted into false nucleotides
- disrupt purine nucleotide synthesis
- may be incorporated into DNA, disrupting helix

39

what is cytarabine?

- sugar moiety of cytidine is arabinosine rather than ribose
- isolated from the sponge cryptothethya crypto
- cellular activation to ara-CTP
- S phase cell cycle specific
- inhibit DNA polymerases
- incorporation into DNA causes chain termination

40

what are cytotoxic antibiotics?

act mainly by a direct action on DNA as intercalates
- dactinomycin

41

what is dactinomycin?

- isolated from Streptomyces
- inserts itself into the minor groove in the DNA helix
- RNA polymerase function is disrupted
- common adverse drug reaction includes bone marrow suppression, fatigue, hair loss, mouth ulcer, loss of appetite and diarrhoea

42

what is Doxorubicin?

- from Streptomyces?
- inserts itself between base pairs
- binds to the sugar-phosphate DNA backbone
- local uncoiling
- impaired DNA and RNA synthesis
- now some 2000 doxorubicin analogues (anthracyclines) exist

43

what are microtubule inhibitors?

- isolated from Madagascar periwinkles
- bind to micro tubular protein
- block tubulin polymerisation
- block normal spindle formation
- disrupt cell division

44

what do steroid hormones do?

tumour may be responsive to a specific hormone which makes it regress
- prednisone
- prednisolone

45

what is prednisone?

- synthetic adrenocortical steroid hormone
- converted in the body to active form

46

what is prednisolone?

suppresses lymphocyte growth

47

what will an antagonist of the hormone do?

suppress growth
e.g. tamoxifen - antagonist of oestrogen receptor

48

what are some breast cancers?

- oestrogen dependent
- oestrogen stimulates their growth
- can be treated with Tamoxifen

49

what are most prostrate cancers dependent on?

stimulation by testosterone

50

what could the prostrate cancer treatment be?

testosterone receptor antagonists
- e.g. glutamine (Drogenil)
- now replaces by bicalutamide (casodex)

51

what are pituitary downregulators for prostrate cancer?

- LHRH agonists inhibit release of Luteinising hormone (LH)
- LH normally stimulates testes to produce testosterone
- result: reduced testosterone release, reduced cancer growth