Mar23 M3-Principles of Management of Cancer of Blood Flashcards
goal of cancer therapy + one example of targetted process
- take advantage of what’s different in cancer cells
- cells proliferating is one thing different
solid tumor vs blood (liquid) tumors preferred modalities of treatment
solid = surgery and radiation liquid = chemotherapy and host immunodefense (stimulate the immune system)
4 chemotherapeutic drug types
- DNA alkylating
- anti-metabolites
- anti-microtubules (natural products)
- topoisomerase inhibitors (natural products)
examples of specific targets of chemotherapy
- steroid hormone Rs (with prednisone, a glucocorticoid)
- enzymes involved in signaling (tyrosine kinase inhibitors (imatinib))
- cell surface molecules (target with Abs like rituximab (anti-CD20), brentuximab (anti-CD30), pembrolizumab (anti-PD1)
4 phases of the cell cycle in order + main checkpoints
G1, (checkpoint), S, G2, (checkpoint), M, (checkpoint), G0 or G1 again
S-phase specific chemotherapy drugs and some examples
- anti-metabolites*
1. S phase specific and SELF LIMITING - methotrexate
- 5-fluorouracil
2. S phase specific - cytosine arabinoside, also called cytarabine, (a nucleotide analog. blocking transformation of oxynts to deoxynts
- hydroxyurea
- topoisomerase inhibitors* (block S-G2 phase)
- daunorubicin
M-phase specific chemotherapy drugs and some examples
microtubules blocking
- vincristine
- vinblastine
- taxols
non cell cycle specific chemo drugs and some examples
DNA alkylating and damaging drugs
- cyclophosphamide
- dicarbazine
cyclophosphamide active portion
- looks like adenine, can bind guanine on position N7
- active part is N with 2 CH2CH2Cl branches
- 1 molecule of the drug binds with other molecule that is next to it on other DNA strand (cross
cyclophosphamide mechanism of action
- 1 molecule of the drug binds with other molecule that is next to it on other DNA strand (cross-linking)
- cross-linking is hard to repair. get mispairing mutations that have to be repaired.
dacarbazine mechanism of action (other alkylating agent)
- methylates guanine at O-6 and N-7 positions
- causes mispairing because it modifies guanine
- DNA damage kills the cell
problem of alkylating agents as chemo drugs
- toxicity to rapidly proliferating cells (BM, GIT, gonads)
- resistance to them (increased inactivation by nucleophilic trapping agents, increased DNA repair, decreased activation)
normal thymidine (TMP) formation cycle in the cell
- dihydrofolate is made into tetrahydrofolate by dihydrofolate reductase
- methylation reaction by thymidylate synthase to synthesize TMP
methotrexate (anti-metabolite, acts on S phase) mechanism of action
- inhibits dihydrofolate reductase (acts on normal folic acid biochem)
- methotrexate polyglutamates inhibit thymidylate synthase
- *no TMP made, building block of DNA, can’t make DNA**
ways cancer cells develop resistance to methotrexate
- inhibit active transport
- inhibit polyglutamate
- change dihydrofolate reductase
- amplify dihydrofolate reductase (more genes for it)
5-fluorouracil (anti-metabolite, S phase specific) mechanism of action
- transfers fluorine on thymine to replace its methyl group*
- inhibition of RNA processing
- incorporation into DNA
cytarabine (also called cytosine arabinoside) (anti-metabolite, S phase specific) mechanism of action
- modifies sugar (deoxyribose) on nts.
- competes with dCTP (cytosineTP) and induces strand breaks and triggers apoptosis
vincristine and vinblastine (vinca alkaloids) mechanism of action
- bind mtb monomers (tubulin)
- terminate assembly of mtbs causing depolymerization and mitotic arrest
- bad chromosome segregation: cell dies
taxols mechanism of action
promote microtubule assembly and inhibit their disassembly (necessary for chromosome segregation)
daunorubicin (doxorubicin) (topoisomerase inhibitor) mechanism of action
- intercalates in DNA
- inhibits topoisomerase II causing DNA strand breaks (this enzyme normally repairs DNA)
topoisomerase inhibitors (block cell cycle at S-G2) structure of the molecule + used in what conditions
- tetracycline, flat ring structure
- in some leukemias (AML, ALL, CML)
bleomycin what kind of drug + mechanism of action
- DNA damaging drug*
- binds DNA, Fe and forms radicals
- consequence = single and double strand breaks + chromosomal aberrations
prednisone mechanism of action (in the more specific drugs) + used more in what cancers
- glucocorticoid receptor agonist
- in response to this TF, many genes are expressed, and are involved in immune response
- blood cancers, breast cancers (act on estrogen R activation), prostate cancer (act on androgen R activation)
most discussed example of translocation in leukemia
chronic myelocytic leukemia. translocation of Abl on chrom 9 and Bcr on chrom 22. forming philadelphia chrom with both on it