LECTURE 2 + 3: Experimental Approaches to Cancer Flashcards
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3.7, 3.30, 4.5
Hallmarks of cancer importance
cancer isn’t a single disease
collection of diseases w similar characteristics
unification factors
enable therapeutic treatment
Tumours by tissue of origin:
blood cells (B, T, myeloid…)
hematopoietic
Tumours by tissue of origin:
epithelial cells (lung, breast…)
carcinoma
Tumours by tissue of origin:
connective tissues (muscle, bone…)
sarcoma
Tumours by tissue of origin:
nervous system (glio-, retino-blastomas…)
Neuroectodermal
Tumours by tissue of origin:
small cell lung cancer, melanoma
Non-neuroectodermal
Cancer tumors are divided into ____ and ______ tumors
liquid, solid
Totally liquid tumors
Leukemia
What is leukemia?
excessive proliferation of circulating cells
usually white blood cells (leukocytes)
totally liquid
Semi-solid/liquid tumors
Lymphoma
What is lymphoma?
elevated numbers of lymphocytes in the peripheral blood
also present as solid masses in lymph
nodes (often multi-focal)
Solid tumors
Lumps - localized cell proliferation
Found/associated with a multicellular organ
Spread around the body by metastasis
Why are leukemias and solid tumours treated differently?
Leukemias can’t be surgically removed
Etiology of the cancers is different
Most prevalent & deadly cancer
carcinomas (cancers of the epithelium)
Leading sites of new cancer and deaths (male)
Prostate, lung & bronchus, urinary bladder, colon & rectum, pancreas (deaths)
Leading sites of new cancer and deaths (female)
breast, lung & bronchus, uterine corpus, colon & rectum, pancreas (deaths)
basement membrane
cell-free matrix between epithelial cells and connective tissue
malignant cancer
disruption of the basement membrane
degrees of malignancy
normal -> hyperplasia -> dysplasia -> cancer
cancer only when it breaks past the basement membrane
malignant growth
- break past the basement membrane
- invade adjacent tissue
- enter blood and lymph
- metastasis
Approaches to Studying Cancer
Observational (Human/Patient)
- epidemiological
- genomic
- clinical
Experimental (hypothesis driven)
- carcinogens
- tissue culture assays
- mouse cancer models
Approaches to Studying Cancer: Epidemiology
what are the different ways we study it?
- Age incidence curves
- Cancer risk factors
- Incidence in different populations
Approaches to Studying Cancer: Epidemiology - Age incidence curves
what do you learn from the curves?
- cancer risk increases with age (curve steeper with age)
- cancer results from multiple events that accumulate over your life (at least 5-6 independent random events)
Why is cancer not subject to forces of evolutionary selection?
Post-reproductive age disease
Approaches to Studying Cancer: Epidemiology - Risk Factors
what are the top risk factors?
Tobacco use»_space;>obesity»pathogens
»» physical inactivity, diet > alcohol > reproductive factors > UV light > environmental pollutants
Cigarettes and lung cancer
- lots of smoking after WW1, WW2
- 30-35 year lag
- lung cancer rates peak in 1990 in the US
Approaches to Studying Cancer: Incidence in different populations
genetic vs environmental factors
environmental factors outweigh genetic factors for most cancers
eg. incidence of prostate (10x) , breast (10x) and stomach (5x) in Hawaiian-Japanese immigrants adopt rates of Hawaiians, not Japanese
Approaches to Studying Cancer: Genomic Studies
what is the goal of the genomic studies
survey the entire genome for transcriptional changes and changes at the DNA level (point mutations, insertions, deletions)
no of base pairs in human genome
3 billion
cancer genome sequencing allows us to identify
MIRA
mutations
insertions/deletions
rearrangements
amplifications
next gen sequencing technology
explain what it is
challenges of genomic studies
tumor heterogeneity
1. mixture of cell types (immune cells, fibroblasts, endothelial cells, neoplastic cells)
2. diversity of neoplastic cells (clones)
solution to tumor heterogeneity
single cell analysis
Approaches to Studying Cancer:
Clinical Studies
phases
Phase 1: SAFETY
- small groups, 50
- how the agent affects the body
- safe dosage
Phase 2: EFFECTIVENESS
- medium group, 200
- is the agent effective against the disease
Phase 3: BETTER THAN STANDARD
- large group, 2000
- randomized trial
Pharmacokinetics (PK)
Time course of drug concentration in body, usually monitored in blood
Pharmacodynamics (PD)
Time course of activity of drug in target tissue, e.g. cancer
Therapeutic Index
Dose range of drug that is therapeutically active against cancer without being highly toxic
Biomarkers
Molecules, cells, phenotypes that are identified as predictive of responsiveness to drug
Carcinogen
Agents that contribute to tumor formation
Cancers associated with occupation
- Radium girls - radium in watches increased risk of multiple cancers
- Chimney sweeps increased risk of skin cancers of scrotum
- Silver ore miners increased risk of lung cancer
- Tobacco snuff users increased risk of nasal cancer
- X-ray technicians increased risk of cancers
- Shipbuilders exposed to asbestos increased risk of mesothelioma
- Smokers increased risk of lung cancer
Yamagiwa and Ichikawa (1915)
First successful induction of cancer
by a specific agent
Induced cancer in the skin of rabbit
ears by painting them with coal tar
repeatedly for hundreds of days
Ames Test: Goal/ Accomplishments
Approach: compare carcinogenicity to mutagenicity in bacteria
Confirmed carcinogens are mutagens (altered DNA, genetic alteration)!!
Ames Test: Procedure
- Suspected carcinogen + homogenized rat liver
- metabolic activation by rat liver enzymes
- add to Salmonella with mutation that prevents synthesis of histidine
- mutagens revert defective gene, so bacterial colonies grow
Approaches to Studying Cancer:
Experimental - 2D cell cultures
title card no question
title card no question
Hayflick Limit
max 60 doublings of normal cells in cell culture, they always hit senescence
due to telemore shortening
normall cells in tissue culture
Finite lifespan (extra serum and media = extended survival, but they eventually die)
always reach senescence
HeLa cells
First immortal human-cell line (cervical cancer)
Cell culture consists of __, __ , ___
cells, medium, substrate
Cell Culture: Cells
- Fibroblasts (cells generally of mesenchymal origin that make extracellular matrix)
- Epithelial cells are harder to grow
Cell Culture: Medium
Contains salts, energy source (glucose), amino acids, vitamins, buffer (CO2/HCO3–) and growth factors (in serum)
Eg. DMEM, RPMI
Cell Culture: Substrate
Surface on which cells are grown on
Cells are plated and adhere to treated plastic/glass
Most cell types are anchorage-dependent (adhere to plastic) for growth and proliferation
Undergoes treatment to become more hydrophilic to facilitate cell attachment
Properties of normal cells in tissue culture
- GO
Growth arrest in low serum - growth factor signalling required for proliferation - STOP
Contact inhibition - cellular growth & division stops due to contact with other cells - DIE
Anchorage dependent growth - epithelial cells require attachment for survival
Properties of cancer cells in tissue culture
- Growth factor independent growth
- Loss of contact inhibition (they grow on top of each other)
- Anchorage independent growth
Assays to measure cell transformation (for cancer)
gold standard: tumorigenesis in nude mice
in vitro
- Growth factor independent growth => Serum indepndent growth
- Loss of contact inhibition => focus forming assay
- Anchorage independent growth => soft agar assay
- immortalization => infinite proliferation
focus
group of cells clustered together
soft agar assay
used to test for anchorage independent growth
base agar matrix
cell suspension + agar matrix
formation of cell colonies
counted using colorimetric detection (MTT soln)
hallmarks of cancer seen in cell culture assays
S - sustaining proliferative Signaling
A
D - resisting cell Death
I - replicative Immortality
S - evading growth Suppresors
M
pros of using cell culture to study cancer
- use of animals reduced
- Homogenous cell population, same growth requirements
- Control of the extracellular environment
- Minimize interference from other biological molecules that may occur in vivo
- Screens for cancer-causing genes (Lec. 4) or for cancer therapies
cons of using cell culture to study cancer
- Impossible to re-create in vivo environment
- Remove interaction with other cells, hormones, support structures (ECM) that would be present in vivo (the tumor microenvironment)
- Artificial conditions could cause cells to de-differentiate or change phenotyp
Lecture 3
Breakpoint go stretch :D
Approaches to Studying Cancer:
Experimental - Mouse Models
what are the different types of mouse models?
GSOX
GEMMs
Syngeneic
Orthotopic
Xenograft
Syngeneic mouse model
Transplant tumor cells from mouse to mouse
Xenograft
Transplant tumor cells from human to mouse
Grafts from human primary tumors or cell lines
Have to be injected into an immuno deficient mouse
Orthotopic
Transplant tumor cells into their native location
Can be both xenograft and syngeneic
GEMMs
Genetically engineered mouse models arise in situ
Nude mice
FOXN1 mutation
Blocks development of thymus (and hair) => no T cells
Tumors easy to monitor
SCID mice
Severe Combined Immunodeficiency (SCID)
Can’t complete VDJ recombination (DNA-PK mutation) and lack T or B cells
Limitations of Mouse Models
- Different lifespans (2 vs 80)
- Different size
- Different physiology
- Different metabolic response (PK)
- Fewer mutations required (mice fibroblasts require ~2 mutations
- Different tumors from same deficiencies (p53 mice -> sarcomas, p53 humans -> carcinomas)
- Less metastasis
