Cancer Biology Flashcards
What are characteristics of a Benign tumour?
- Slow growing
- Well-organized
- Differentiated (known origin)
- Generally non-destructive (not harmful)
- Rarely cause death
What are the characteristics of a Malignant tumour?
- Fast growing
- Unorganized
- Loss of differentiation
- Increased invasiveness
- Ability to kill host tissue
- Usually cancerous
Explain the benign and malignant tumour continuum
A benign tumour can have characteristics that lead towards malignant and become benign, but malignant tumours cannot become begign
What are Carcinomas?
Solid mass/tumours that originate in the epithelial cells (lining of all tissues)
- Most common cancer cases, 85-90% of all cancers are carcinomas
What are Melanomas?
- Originates in melanocytes (can be apparent as a mole or can be found in the eye)
- Most commonly found on skin
- Most serious type of cancer
What is the difference between a melanoma skin cancer and a non-melanoma skin cancer?
Melanoma - more deadly and have the ability to spread
Non-melanoma - More common but not deadly and cannot spread
What are Sarcomas?
Solid tumours found in connective tissues, bones, muscles, cartilage and fat (soft tissue sarcomas or osteosarcomas)
- Account for less than 2% of all cancers
Are sarcomas life threatening?
Yes, the survival rate is not great.
- Can lead to amputations due to osteosarcomas (more common in younger ages)
Where are osteosarcomas found?
Typically in long bones - Femur, Tibia, etc - but can form on any bone
- Small and hard to detect
What is Leukemia?
Non-solid type of cancer that forms in blood organs (Bone marrow, lymphatic system)
What are the two main types of leukemia?
- Acute - Sudden onset
- Chronic - Slow onset, low grade level for a long period of time
How else can leukemia be classified?
Based on cell types
- Myeloid (myelogenous leukemia)
- Lymphocytes (lymphocytic leukemia)
What are Lymphomas?
Non-solid cancer of the lymphocytes that results in enlargement of lymph nodes
- 5% of cancers are lymphomas
What are the two distinct lymphoma groups?
- Non-Hodgkin’s Lymphoma (NHL) > throughout the lymphatic system, quick to progress but hard to treat
- Hodgkin’s Lymphoma > Progress through lymphatic system one node at a time, easier to treat
What is the origin of cancer?
Cancer develops from normal cells
Is cancer an invader?
No, cancer does not invade cells it forms within them however invaders like viruses/bacteria may promote cancerous cell growth
Do all cells in tumours have the same characteristics?
Cells within a tumour all have the same genetic makeup
How can you determine the origin of cells in a tumour?
Because of their genetic makeup, all cells in a tumour are developed in one single cell. Their genetics determine their origin cell
How does a tumour arise?
From a series of mutations in the original cell and progeny of the cell
What is a mutation?
Permanent changes in DNA
How many mutations in specific genes does it take to produce a tumour?
6 independent mutations to a specific gene to produce a tumour (can occur over years of time)
What is the mutation rate in Humans?
1 in 1 million genes per cell generation (most harmless or cell repairs self)
How do mutations occur?
- Inherited (genetics)
- Arise during DNA replication and recombination
- Caused by mutagens
What are mutagens? Give examples
A mutagen is an environmental agent that cause mutations
- UV rays = risk of skin cancer
- Pollutants (air, work place substances)
- Smoking = risk of lung cancer
What can genetic mutations result in?
Results in the activation of oncogenes
What does the activation of oncogenes do?
Increases the chance of developing cancer
What are oncogenes?
Excessively active versions of normal cellular genes called proto-oncogenes
What do proto-oncogenes do?
Parts of DNA that
- Control cell division
- Cell death
- Other cell functions
What happens if proto-oncogenes don’t work properly?
Become oncogenes which
- causes increase in uncontrolled cell division
- Potential problems with cell death
- Increases the risk of cancer
What do oncogenes do to increase risk of cancer development?
Leads to excessive proliferation (cell division) and problems in signalling cell apoptosis (cell death)
- Cancer is rarely caused by one activation of a single oncogene (usually multiple)
What does a tumour suppressor do?
Normally they suppress oncogenes by controlling excessive cell division
What happens when there is a mutation in tumour-suppressor genes?
Typically less of function of t-s genes, therefore there is nothing suppressing oncogenes
How can a person have inactive tumour suppressor genes?
- Most commonly inactivation is associated with inherited cancers
- Can also be sporadic (by chance) and not inherited
What is an example of a sporadic tumour cancer suppressor?
Wilm’s tumour
What is Wilm’s Tumour (nephorblastoma)?
- It’s a tumour that originates in cells of the kidney
- Most common Kidney (renal) cancer
What is the cause of Wilm’s Tumour?
Caused by mutations in kidney cells in utero (embryonic tumour) = Paediatric tumour
- Most are not inherited but rather sporadic
What population does Wilm’s Tumour affect?
- Children up to age 10
- Majority affects age 43 months - 48 months
- Accounts for 6% of all childhood cancers (1 in 10,000 live births)
- 90-95% of cases are in a single kidney, can happen in both (commonly inherited)
What are the 4 gene types associated (mutated) in Wilm’s Tumour?
TP53 - classic tumour suppressor gene
CTNNB1 - classic oncogene
WTX - tumour suppressor gene
WT1 - similar to tumour suppressor gene
What are properties of tumour cells?
- Proliferate (divide) indefinitely
- Less cell adhesion (sticking together)
- Ability to continue growing despite crowding
- Reduced apoptosis (cell death)
What is Metastasis?
Migration of cancer cells from the original tumour site through the blood and lymph to other tissues
Why are metastases so crucial in relation to cancer?
Without metastasis, cancer would be harmless. Metastasis is a major cause of death
Is metastasis growth random?
No. Main thing to remember is each different type of cancer has a specific site where metastasis form.
E.G: Liver cancer can form metastasis in the lungs but it’s still considered liver cancer because of it’s origin
What must be in place for metastatic cells to be successful?
- Angiogenesis
- Motility
- Alterations in cell adhesion
- Secretion of proteolytic enzymes
- Ability to escape immune surveillance
What is Angiogenesis?
The development of new blood vessels to supply blood needed for primary tumour growth
Why is angiogenesis related to metastatic cells?
New blood vessels provide a route for metastatic cells to escape into the blood and travel to another part of the body
- The degree of angiogenesis determines likelihood of metastases, more blood supply = more chance of metastases
What is Motility?
The ability of a cell to move under its own power
Why is motility related to metastases?
It’s needed in order for a tumour cell to leave the primary tumour and circulate throughout the blood or lymphatic system
What is Cell Adhesion?
Allows cancer cells to stick to extracellular matrix and not to other cells allowing metastases to adhere successfully to other structures/organs
What do Proteolytic Enzymes do?
Secreted by cancer cells to break down barriers such as:
- Basement membrane
- Extracellular matrix
- Endothelial barrier
Why are proteolytic enzymes important for metastases?
Need to break down barriers to get into circulation and the new tumour bed to settle and continue growing
What immune system cells do cancer have to escape from? (cells that kill off disease)
- Cytotoxic T lymphocytes
- Activated macrophages
- Natural killer cells
What is the Metastatic Cascade?
Primary Tumour forms > Angiogenesis and Invasion >
Survival in Circulation > Tumour Cells Arrest in Capillary Bed of Organ > Establishment of Secondary Tumour
