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) M
G0
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