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Pathology > Chemotherapy > Flashcards

Chemotherapy Flashcards

1
Q

What are antimetabolites?

A

Methotrexate

5-fluorouracil

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2
Q

Methotrexate mechanism

A

Competitive inhibitor of dihydrofolate reductase (DHFR), close structural analogue of folic acid.

Inhibits biosynthesis of purines and dTMP - hence inhibits RNA synthesis and DNA replication

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3
Q

What other diseases is methotrexate used for as well as cancer?

A

Malaria, psoriasis, rheumatoid arthritis

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4
Q

5-fluorouracil action

A

Antimetabolite drug converted in vivo to FdUMP, which inhibits thymidylate sythase (TS)

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5
Q

What are alkylating/platinum drugs?

A

DNA damage leads to cell cycle arrest apoptosis

Cyclophosphamide

Cisplatin

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6
Q

What are topoisomerase inhibitors?

A

DNA damage via direct binding to DNA

Doxorubicin

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7
Q

Cyclophosphamide action

A

Alkylating agent

Displacement of each chlorine atom allows covalent cross-linking between N7 nitrogen’s of guanine bases.

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8
Q

What drug is similar to mustard gas?

A

Cyclophosphamide

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9
Q

What other diseases is cyclophosphamide used to treat?

A

Also active in autoimmune diseases (lupus, rheumatoid arthritis)

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10
Q

What selectivity does cyclophosphamide give?

A

Detoxification of aldophosphamide intermediate by aldehyde dehydrogenase (ALDH) confers some selectivity for cells with low ALDH.

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11
Q

Cisplatin action

A

Alkylating agent

Displacement of chloride ligand by water allows cross-linking of DNA bases by platinum

Intra-strand DNA crosslinks account for most of the cytotoxicity

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12
Q

Cisplatin structure

A

Central Pt with 2 Cl and 2 NH3

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13
Q

Doxorubicin action

A

Topoisomerase inhibitor

DNA intercalating anthracycline inhibits cellular enzyme DNA topoisomerase II, stabilising a reaction intermediate in which both DNA strands are broken.

Proteolytic processing of this ‘cleavable complex’ frees the double-strand breaks

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14
Q

What are anti-mitotic agents?

A

Inhibit stages of mitosis

Vincristine

Taxanes

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15
Q

Vincristine action

A

Anti-microtubule agent: inhibits tubulin polymerisation in a manner similar to colchicine

prevents assembly of mitotic spindle
arrests cells in metaphase
selectively toxic to cells with defective ‘spindle attachment’ checkpoint

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16
Q

Taxane action

A

Stabilises microtubules so they cannot be disassembled

17
Q

Neoadjuvant chemo

A

chemotherapy before surgery

reduces size of local disease; early treatment of micro metastases

18
Q

Adjuvant chemo

A

chemotherapy after surgery

early treatment of micrometastases

19
Q

Palliative chemo

A

reduce tumour bulk

slow the growth of existing lesions

delay development of new lesions

relieve symptoms

20
Q

Side effects of chemotherapy

A

Immunosuppression and myelosuppression

Neutropenic enterocolitis

Gastrointestinal distress

Anemia

Nausea and vomiting

Hair loss

Infertility

Neuropathy

Vascular damage

Cardiotoxicity

21
Q

What can neutropenia lead to?

A

Neutropenia (a decrease of the neutrophil granulocyte count below 0.5 x 109/litre) can result in neutropenic sepsis and is a common cause of morbidity and mortality

22
Q

How can low neutrophil count be counteracted with other drugs?

A

Can be improved with synthetic G-CSF (granulocyte-colony-stimulating factor, filgrastim, lenograstim).

23
Q

What is CAV therapy? Why give combination therapy?

A

Reduces resistance

CAV therapy (small cell lung cancer): cyclophosphamide, adriamycin (doxorubicin) and vincristine.

24
Q

How can therapy cause tumorigenesis?

A

Most therapies are tumorigenic

25
Q

What is a hormonal therapy?

A

Tamoxifen

26
Q

Tamoxifen action

A

Metabolised to hydroxytamoxifen, an oestrogen receptor (ER) antagonist

Binds to ER, recruits co-repressor proteins and inhibits ER-dependent transcription

Arrests growth of ER-positive breast cancer

27
Q

Aromatase inhibitors

A

Aromatase inhibitors (e.g. letrozole) block peripheral oestrogen synthesis in post-menopausal women

28
Q

Imatinib (gleevec)

A

Inhibitor of tyrosine kinase activity

Very high response rates in early-phase CML (BCR-ABL)

also effectively inhibits KIT tyrosine kinase in gastro-intestinal stromal tumour

29
Q

Herceptin (trastuzumab)

A

Humanised monoclonal antibody against the extracellular domain of HER2, down-regulates HER2-dependent mitogenic signalling, may also induce antibody-dependent cellular cytotoxicity (ADCC)

30
Q

HER2 in breast cancer?

A

A member of the epidermal growth factor receptor (EGFR) family of transmembrane receptor tyrosine kinases.

Overexpressed, often as a result of gene amplification, in ~25% of breast cancers, overexpression of HER2 drives inappropriate cell proliferation - associated with poor prognosis.

Pathology (21 decks)

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