Module 17 Flashcards
Cancer
- uncontrolled proliferation of cells
Neoplastic cells
cancer cells
abnormal and uncontrollable cell growth
Characteristics of Cancer Cells (5)
1) persistant uncontrollable cell proliferation
2) invasive
3) metastatic
4) immortal
5) angiogenesis
Cancer - invasive
invade adjacent tissue facilitating cancer growth in different areas of the body
Cancer - is metastatic
ability of cancer cells to travel to different sites in the body and invade to form new tumours
Cancer - imortal
- cancer cells do not die they continually divide
cancer + angiogenisis
- cancer cells develop their own blood vessels to supply nutrients –> crucial for proliferation
Treatment for cancer
1) surgery
2) radiation
3) chemotherapy
Treatment for cancer - radiation
high energy radiation used to shrink tumours and kill cancer cells
- damage DNA of both cancerous and non-cancerous cells
Treatment for cancer - chemotherapy
- chemotherapeutic drugs target rapidly dividing cells
The cell cycle
- process of proliferation.
5 phases
1) G0
2) G1
3) S
4) G2
5) MG0
phase of cell cycle
cell is resting, does not replicate
G1
phase of cell cycle
cell prepares to synthesize (duplicate) its DNA
S
The cell synthesizes DNA
G2
The cell prepares for mitosis
M (cell cycle)
The cell divides in a process called mitosis
Obstacles to sucessful chemotherapy - toxicity to normal cells
Neoplastic cells are similar to normal cells … difficult to target only cancer cells during chemotherapy
Which cells does chemotherapy kill?
cells with a high growth fraction (Cancer cells and other normal cells)
What is a growth fraction
ratio of proliferating cells to cells in the resting G0 state
What cells in the body have high growth fraction? (4)
- bone marrow
- GI epithelium
- hair follicles
- germinal epithelium of testes (that gives rise to sperm)
what percent of cancer removed is considered ‘cured’
- 100% cell kill
- difficult, no good tests to determine whether cancerous cells are present in the body in low numbers
- kinetics of cell death is first order (constant percentage of cancerous cells are killed at a given dose of drug)
Why is early detection of cancer important?
- cancer is almost significantly progressed by the time it is diagnosed
ideal treatment of cancer
surgical exision followed by chemotherapy
Screening for cancer - breast cancer
- clinical breast examination every 2-3 years for women over 50
- high risk patients should be screened more often and maybe earlier than 50
Screening for cancer - cervical cancer
- sexually active women should have a pap test every 1-3 years
Risk factors for cervical cancer
- Human Papillomavirus (HPV)
- spread by sexual contact…75% of women and men will have 1 HPV infection in their lifetime
Screening for cancer - colorectal cancer (2)
- men and women 50+ who are not at high risk should have fecal occult blood test every 2 years
- colonoscopy every 5 years in high risk patients
Screening for cancer - prostate cancer
- men over 50 should have digital rectal exam
- and/or Prostate Specific Antigen blood test
Screening for cancer - skin cancer
- self checks performed regularly
- look for changes to birthmarks and/or moles, new skin growths, sores that don’t heal properly
Screening for cancer - testicular cancer
- men over age 15 should regularly perform the testicular self examination
Solid Tumours and Chemotherapy
solid tumours have a large fraction of cells int he resting G0 state
most chemo drugs target proliferating cells, solid tumours dont respond as well
Drug resistance - chemotherapy (5)
1) decreased drug uptake
2) increased drug efflux
3) decreased drug activation (ie. prodrugs)
4) reduced target sensitivity, increased cellular (DNA) repair
5) decreased apoptosis
Drug Resistance to Chemotherapy - P-glycoprotein
- P-glycoprotein is an efflux drug pump.
- by not allowing cellular accumulation of chemo drugs, P-Gp can cause multiple drug resistance
- resistant cells are not killed by chemo agents –>therapeutic failure
Strategies to achieve maximum benefit from chemotherapy
- intermittent chemotherapy
- combination chemotherapy
Intermittent chemotherapy
- kill cancer cells by administering chemo drugs intermittenly, giving time for normal cells to recover
- for this strategy to be successful, normal cells must grow back faster than cancerous cells
Combination chemotherapy - why is it more effective? (3)
1) decreased resistance (multiple drugs with multipl actions make therapy less likely to be affected by mutations)
2) increased cancer cell kill (killing them by different mechanisms of action)
3) decreased injury to normal cells (less overlapping toxicities)
Chemotherapeutic associated toxicities
- bone marrow suppression
- digestive tract injury
- nausea and vomiting
Chemotherapy + bone marrow suppression (3 effects)
1) neutropenia (decreased neutrophils)
2) thrombycytopenia (decreased platelets)
3) anemia (decreased red blood cells)
Neutropenia - what, dangers
decreased neutrophils in the blood
neutrophils = a WBC that helps fight infection
Thrombocytopenia - what, dangers
Decreased platelets in the blood
- platelets involved in coagulation of blood
- decreased platelets = increased risk of serious bleeding
Chemotherapy - digestive tract injury
- stomatitis (inflammation of oral mucosa) can lead to ulceration
- diarrhea (secondary to damage of epithelial lining of intestine)
stomatitis
inflammation of oral mucosa
Chemotherapy - nausea and vomiting (treatment)
- common and serious adverse effect (may lead patients to refuse further treatment)
- treat with anti-emetics, prevent dehydration, prevent malnutriotion
Drugs to treat cancer - classifications (2)
- Cytotoxic agents
- hormonal and other agents
Cytotoxic agents - categories (5)
- alkylating agents
- platinum compounds
- antimetabolites
- antitumour antibiotics
- mitotic inhibitors
Cytotoxic agents - classification based on cell cycle phase
1) cell cycle phase specific drugs
2) cell cycle phase non-specific drugs
Cytotoxic drugs - cell cycle phase specific drugs (when are they effective)
- only effective if the cancer cell is in a specific phase of the cell cycle (G1-M)
- EX: mitotic inhibitors are only effective when cancer cells are undergoing mitosis
- must include cells actively part of the cell cycle (not effective for cells in G0)
Cytotoxic drugs - cell cycle phase non-specific drugs (when effective)
- act during any stage of the cell cycle including G0
- they are still more toxic to cells that are proliferating than cells in G0
Alkylating Agents - mechanism of action
- highly reactive chemical that transfers an alkyl group to cell components (primarily DNA)
- they act by forming cross-bridges between nitrogen atoms on guanine nucleotides that make up our DNA
- result = miscoding, breaking of DNA, and posible inhibition of DNA replication
Alkylating agents - cell cycle classification
cell cycle phase non-specific = effective during any phase of the cell cycle
Alkylating agent common name
cyclophosphamide
Cyclophophamide - mechanism of action
- is a pro-drug - must be converted to active form by the liver
cyclophosphamide - time of onset
delayed (is a pro-drug and needs to be metabolized by liver)
cyclophosphamide - indications for use
- Hodgkins disease
- solid tumours of the head, neck, ovary, breast
Platinum compounds - structure
- drugs with platinum in their chemical structure
Platinum compounds - mechanism of action
- Act by cross-linking DNA and therefore inhibiting DNA replication
- cross-link DNA by binding to guanine nucleotides
Platinum compounds - cell cycle classification
cell cycle phase non-specific
Platinum compounds - common drug
Cisplatin
Cisplatin - indications for use
- platinum compound
- metastatic ovarian and testicular cancers, and advanced bladder cancer
Cisplatin - adverse effects (3)
- nephrotoxic
- ototoxic (toxic to ear –> deafness)
- emetogenic (causes nausea and vomiting)
Antimetabolites - what
Similar to natural compounds the body uses to
- synthesize cellular constituents
- incorporate into DNA
Antimetabolites - mechanism of action
- inhibiting particular enzymes or by preventing DNA replication
Antimetabolites - cell cycle based classification
phase-specific –> S-phase
Antimetabolites - classification based on function (3)
1) Folic acid analogs
2) purine analogs
3) pyrimidine analogs
Folic acid analogs
block conversion of folate to its active form (= no DNA replication)
Purine analogs
(purines [adenine, guanine] used to make DNA and RNA)
Purine analogs inhibit synthesis of DNA and RNA
Pyramidine analogs
(pyrimidines = cytosine, thymine, uracil)
Pyramidine analogs inhibit synthesis of DNA
Antitumour antibiotics - mechanism of action
- kill cancer cells by intercalating DNA (move between bases of DNA, bind to DNA, cause change in structure of DNA = altered DNA is unable to be used as a template for synthesis = DNA synthesis is inhibited
Antitumour antibiotics - route of administration
very poorly absorbed and therefore are given intravenously
Anthracyclines - drug class
- a type ot Antitumour antibiotic
Antitumour antibiotics - adverse effects (2)
- can cause severe bone marrow suppression and are cardiotoxic
Mitotic Inhibitors - mechanism of action
Act during cell cycle to inhibit mitosis and prevent cell division
Vinca alkaloid (what, mechanism of action)
- mitotic inhibitor
- block metaphase by binding to protein tubulin (microtubule) disrupting organization of microtubules –>disruption of chromosomes + cell death
Taxanes (what, mechanism of action)
- a mitotic inhibitor
- acts in late stage of G2 (just prior to mitosis)
- Taxanes stabilize microtubule bundles –> prevent cell division
Hormonal agents to treat cancer (6)
1) glucocorticoids
2) gonadotropin releasing hormone agonist
3) androgen receptor antagonist
4) anti-estrogens
5) aromatase inhibitors
6) Trastuzumab
Glucocorticoids - when used
- used as adjunct to other chemo agents in cancers derived from lymphoid tissue
Glucocorticoids - mechanism of action
- directly toxic to lymphoid tissue
Glucocorticoids - adverse effects (LT use) (6)
- osteoporosis
- adrenal insufficiency
- susceptibility to infection
- GI ulceration
- electrolyte disturbane
- growth retardation
Glucocorticoids - other effects (not just cancer killing) = 3
- management of complications of other chemo
1) reduction in nausea and vomitting
2) reduction of pain
3) improved appetite
Drugs for prostate cancer
- Gonadotropin Releasing Hormone (GnRH agonist)
- Androgen Receptor Antagonists
Goal of drugs treating prostate caner
androgen deprivation
Gonadotropin Releasing Hormone (GnRh) agonist - mechanism of action
- GnRH agonists - cause transient increase in testosterone production (cancer symptoms may increase at start of therapy)
- over time, testosterone synthesis release is decreased
1) GnRH cause release of testosterone from testes
2) testosterone ‘feeds’ prostate cancer cells, but also acts by negative feedback to inhibit further GnRH release
3) GnRH agonists cause transient increase in testosterone, but then cause decreased GnRJ activity through desensitization and negative feedback
4) net effect is decreased testosterone synthesis and release
Androgen Receptor Antagonists - use
Used in combo with a Gonadotropin Releasing hormone agonist or castration
Androgen Receptor Antagonists - mechanism of action
block androgen receptors in tumour cells
Drugs for breast cancer
1) anti-estrogens
2) aromatase inhibitors
3) Trastuzumab
Treatment of breast cancer
- Primary treatment = estrogen deprivation (estrogen feeds tumour)
- combine with surgery and radiation therapy
Anti-estrogens - mechanism of action
- block estrogen receptors
Tamoxifen - mechanism of action
- an anti-estrogen drug
- a partial estrogen receptor agonist (minimally activates estrogen receptor but also blocks endogenous estrogen from binding to its receptor)
Aromatase inhibitors - mechanism of action
- inhibits aromatization (process of converting androgens ino estrogen)
- decrease amount of estrogen available to breast cancer cells
Aromatase inhibitors - considerations of population
- does not stop ovarian estrogen synthesis
- therefore, only useful in post-menopausal women
Trastuzumab - mechanism of action
- breast cancer patients with increased number of Human Epidermal Growth Factor Receptor 2 (a transmembrane receptor that helps regulate cell growth) will have especially aggressive tumour growth
- Trastuzumab is a monoclonal antibody that binds to HER2 and prevents cell proliferation
Trastuzumab - route of administration
IV (antibodies are degraded in stomach and poorly absorbed)
Trastuzumab - Adverse event
- cardiotoxicity
Tyrosine Kinase Inhibitors - mechanism of action
Stops Tyrosine Kinases’ natural function
- protein kinases are enzymes that phosphorylate proteins on specific amino acids (tyrosine)
- activity of tyrosine kinase can activate gene transcription and/or DNA synthesis, making them an attractive option for the treatment of cancer
- increased activity of tyrosine kinases have been observed in many cancers
Imatinib - drug class
- prototype tyrosine kinase inhibitor
Imatinib - mechanism of action
- causes complete inhibition of cellular proliferation and cell death via apoptosis (programed cell death)
Imatinib - target disorders
- chronic myelogenous leukemia (CML)
- gastrointestinal stromal tumours (GIST)
Imatinib - adverse effects (4)
- nausea
- vomiting
- edema
- muscle cramps
