Week 8 Flashcards
What is combination chemotherapy?
- Combination: use multiple different drugs at the same time or in specific sequence
What is adjuvant chemotherapy?
Adjuvant: use drugs after surgery to remove residual or metastatic cells
What is neoadjuvant chemotherapy?
Neoadjuvant: use drugs before surgery to reduce tumor mass and to initiate chemotherapy sooner
Compare and contrast cell-specific and cell-nonspecific drugs.
- Specific: target a unique phase in the cell cycle (vinca alkaloids poison mitotic spindle)
- Nonspecific: kill cells regardless of phase (DNA damaging drugs)
What order of reaction is cell killing?
First order.
What percentage of cells are killed with 1 log kill drugs, 2 log kill drugs, and 3 log kill drugs?
- 1 log kill drug = 90% cells killed
- 2 log kill drug = 99% cells killed
- 3 log kill drug = 99.9% cells killed
Why are intermittent therapies used to treat cancer?
Intermittent therapies are used to kill as many cancer cells possible without killing the patient
What are drug transporters, the gene encoding them, and how do they cause drug resistance?
- Drug Transporters: ATPases that transport small molecules out of the cell
- P-glycoprotein encoded by mdr1 gene
- Upregulation causes more drug to be pumped out
Describe the four principles of combination chemotherapy.
- Non-overlapping toxicities
- Targets are in different phases of cell cycle
- Have different mechanisms of action
- Have different mechanisms of resistance
What is the main function of alkylating agents?
covalently binds to DNA
What are examples of alkylating agents, the general mechanism of action, and side effects?
- Examples: Nitrogen mustards, cisplatin, temozolomide (TMZ)
- MOA: effectively attacks DNA of dividing cells
- Side Effects: non-specifically attacks normal dividing cells
- Hair follicles: hair loss
- RBCs: anemia
- WBCs: immunosuppression
- Epithelial cells of GI tract: GI issues
What is the overall function of antimetabolites?
inhibits synthesis of DNA
What is the mechanism of action of the antimetabolite methotrexate? Why is leucovorin used as a “rescue”?
- MOA: folate analog that binds dihydrofolate reductase (DHFR)
- DHFR is critical enzyme in purine and thymidine synthesis
- Leucovorin is THF that is selectively uptaken by specific expressed transporter only in normal cells to ensure survivability of normal cells during chemotherapy treatment
What is the mechanism of action of the antimetabolite 5-fluorouracil?
MOA: uracil analog that binds thymidylate synthase, preventing conversion of dUMP to dTMP
- Describe how the conversion of dUMP to dTMP occurs. What enzyme is used?
- Describe how the conversion of DHF to THF occurs. What enzyme is used?
What is the mechanism of action of hydroxyurea?
MOA: inhibits ribonucleotide reductase, prohibiting conversion of ribose to deoxyribose for use in DNA synthesis
What is the main mechanism of action in antitumor antibiotics?
disrupts DNA structure and function
What are several examples of antitumor antibiotics and what is their mechanism of action?
- Examples: anthracyclines, dactinomycin, and bleomycin
- MOAs
- Intercalation into DNA – structure is flat so they can slide between base pairs of DNA, preventing DNA and RNA polymerases from acting
- Generation of ROS – causes DNA cleavage
- Binding to cell membranes – hydrophobic regions disrupt processes
What does the upregulation of L-asparaginase do in cancer cells? What is the enzyme it counteracts and the two amino acids being interconverted.
- Function of L-asparaginase is to convert asparagine to aspartate intracellularly
- Function of Asparagine synthetase is to convert aspartate to asparagine intracellularly
- In cancer cells, existing low levels of Asparagine synthetase and induced high levels of L-asparaginase → insufficient [asparagine] → decrease in protein synthesis and cell growth
What is the main function of antimitotic agents?
block microtubule functions
What are the three different types of the antimitotic agents, microtubule inhibitors? What are the two contrasting mechanisms of action? What phase of the cell cycle do these drugs work in?
- Vinca alkaloids
- MOA: prevents assembly of microtubules by binding to tubulin dimers that go into structure
- Taxanes
- MOA: prevents disassembly of microtubules by binding to assembled microtubules
- Estramustine
What are the two different types of the antimitotic agents, topoisomerase inhibitors? What is one example of each? What are the two contrasting mechanisms of action? What phase of the cell cycle do these drugs work in?
- Occurs in S phase
- Topoisomerase II inhibitors
- Example: etoposide
- MOA: topoisomerase II induces ds breaks to unwind DNA and inhibitors prevent resealing by the enzyme
- Topoisomerase I inhibitors
- Example: topotecan
- MOA: collision between replication fork and topoisomerase I – DNA complex → ds breaks → cell death
What is the main function of hormonal agents?
affect signaling through steroid receptors
What is one example and the mechanism of action of glucocorticoids, a type of hormonal agent?
- Prednisone
- MOA: used for liquid tumors to bind to intracellular receptors and affect gene transcription
What is the mechanism of action of progestin, a type of hormonal agent? What is one cancer it is used to treat?
- MOA: agonists for PRs; triggers cell differentiation of immature cancer cells
- Used to treat endometrial cancer
What are two examples of drugs and their mechanism of action of antiestrogens, a type of hormonal agent?
- Tamoxifen, fulvestrant
- MOA: inhibits ERs
What is the mechanism of action of aromatase inhibitors, a type of hormonal agent? Who is it given to? What is one example of a drug used?
- Anastrozole
- Given to post-menopausal women
- MOA: acts by inhibiting aromatase which prevents conversion of antrostenedione to estrone in the adrenal gland
What is the mechanism of action of antiandrogens, a type of hormonal agent? What is one example of a drug? What type of cancer is it used to treat?
- Enzalutamide
- MOA: androgen receptor antagonists
- Used to treat prostate cancer
What is the mechanism of action of overstimulation of LHRH and GnRH receptors?
Overstimulation of LHRH and GnRH receptors with LHRH and GnRH analogues → negative feedback inhibition → internalization and desensitization of receptors → decrease in testosterone and estrogen
What is the main function of signaling inhibitors?
block critical signaling pathways
What are six different drugs used that inhibit RTKs? What does each selectively inhibit?
- Gleevec – selective inhibitor of Bcr-Abl
- Gefitinib – selective inhibitor of EGFRs
- Erlotinib – selective inhibitor of EGFRs for palliative care treatment
- Trastuzumab – selective inhibitor of HER2
- Cetuximab – selective inhibitor of EGFRs
- Rituximab – selective inhibitor of CD20 antigen
What is one example of a angiogenesis inhibitor? What RTK does it selectively inhibit?
Bevacizumab – selective inhibitor of VEGF
What is one example of a proteasome inhibitor?
Bortezomib – specific and reversible inhibitor of proteasomes that degrades pro-apoptotic proteins
What are -nib, -mab, and -mib classes of drugs?
- -nib class of drugs act on RTKs
- –mab class of drugs are monoclonal antibodies that bind to extracellular receptor or to the hormone
- monoclonal because only antibody produced by immune cell
- –mib class of drugs act on intracellular receptors
What are the functions and locations of epithelium?
- Epithelium
- Functions: absorption, secretion, transport, excretion, protection, sensory reception
- Locations: cells of organs, covering of all surfaces, glands, and sensory organs/structures
What are the functions and locations of connective tissue?
- Connective Tissue
- Functions: support, protection, movement
- Locations: tendons, ligaments, fascia, supportive fibrous, muscle, nerve, blood vessels, adipose tissue, bone, cartilage, dermis
What are the functions and locations of hematopoietic tissue?
- Hematopoietic Tissue
- Functions: immune and other defense/surveillance mechanisms, oxygen transport
- Locations: blood, bone marrow cells, and cells of related organs (lymph node, spleen, marrow)
What are the 5 different characteristics common to all epithelia?
- Closely aggregated cells
- Cell-to-cell adhesion
- Polarized – apical and basolateral surfaces
- Attachment to basement membrane
- Avascular