Pathogenesis of Cancer Flashcards
What are the 5 basic steps to cancer development?
- Cell has genetic mutation
- Hyperplasia (inc. reproductive rate of cells causing enlarged tissue/organ size)
- Dysplasia (abnormal cell within tissue/organ)
- In-situ cancer
- Invasive cancer
Why do people get cancer?
Genetics cause the birth and death of cells
If the genetic mutation creates a variant that proliferates quicker, that mutant takes over the organism
(natural selection)
Who developed the theory of evolution by NATURAL SELECTION?
Charles Darwin
Define: Benign Tumour
A mass of cells (tumour) that currently LACKS the ability to:
- invade surrounding tissues
- spread to other areas of the body
Define: Malignant Tumour
A mass of cells (tumour) that HAS the ability to:
- invade surrounding tissues
- spread to other areas of the body (metastasis)
Benign vs Malignant
- edges
- metastasis
- growth rate
- nuclei
- life-threatening ?
BENIGN vs MALIGNANT Edges: Encapsulated vs Irregular Metastasis: No vs Yes Growth rate: Low vs High Nuclei: Normal vs Irregular Life-threatening: No vs Yes
Leimyo-
smooth muscle
Rhabdomyo-
striated muscle
(Structure of Tumours)
Define: Neoplastic cell
Rapid division of cells (reproduce) to variable growth patterns and/or functions to parent cell
Abnormal growth of cells that leads to a tumour (can be malignant or benign)
(Structure of Tumours)
Define: Stroma
Connective tissue framework that provides mechanical support (contains fibroblasts) and nutrition to the tumour cells
Growth of tumours depend on what?
Angiogenesis: The ability of the stroma to induce blood vessels into the tumour
Tumours are clonal. Multiple genetic changes are required
Define: Tumour Differentiation
The extent to which neoplastic cells resemble comparable normal cells which they have arisen from (morphologically and functionally)
Define: Well differentiated tumour/cancer
Neoplastic cells also composed of normal cells from the original parent cell
Where do well differentiated cancers/tumours arise from?
Mature stem cells
Where do undifferentiated cancers/tumours arise from?
Immature stem cells
How do you classify tumours/neoplasms?
Secondly, describe each stage (HINT: There are 3)
Using the TNM staging system (3 stages)
- T = Tumour. Size of primary (original) tumour and the extent of invasion
- N = Nodes. Describes the presence and number of lymph nodes if involved
- M = Metastasis. Distance of metastasis (distance it spread from one part of body to another)
What are the factors to consider during prognosis?
Or the factors prognosis is based on ?
3 factors
- Tumour type
- Grade (degree) of differentiation
- Stage or Extent of metastasis (spread)
- Assess resected (cut-out) tumour AND
- MRI imaging of patient)
Terminology! Explain the difference between sarcoma and carcinoma.
Sarcoma is a tumour originated from connective tissue
Carcinoma is a tumour originated from epithelial tissue
Terminology!
Grade vs Stage ?
Grade = degree of histological resemblance to parent tissue Stage = extent of spread
(histology = structures)
What can cause cancer? (list up to 6)
The Sun Ionising radiation Asbestos Viruses Genetics Parasites Hormones Red meat Cigarettes
What can increase cancer incidence? Lifestyle factors
Diet e.g. Fatty foods (colonal cancer)
Bacterial e.g. H pylori (stomach)
Lifestyle e.g. Smoking, Alcohol
Viral e.g. HPV (cervical)
Hormonal e.g. oestrogens (breas and ovarian)
Environmental e.g. radiation, UV
Occupational e.g. asbestos (mesothelioma - cancer develops from the thin layer of tissue that covers many internal organs. Most commonly: lungs and chest wall)
What is the difference between:
Somatic mutations
Germline mutations?
Somatic mutations occur in non-germline cells hence are non-inheritable
Germline cells are inherited because they are present in the sperm or egg. If there is a mutation in the egg or sperm then all cells affected in the offspring.
Define: Proto-oncogene
Normal gene that when altered by a mutation becomes an oncogene which contributed to cancer.
KEY: (Internal) oncogene signalling drives cell proliferation (cell division) via transcription
What are the differences in function between
Normal Cell vs Cancer Cell
Normal genes prevent cancer by removing or inactivating tumour suppressor genes (TSG)
In a cancer cell, there is damage to the genes in the nucleus due to mutated/inactivated tumour suppressor genes **QUESTION THIS
Activation of oncogenes and inactivation of TSGs
Normal genes regulate cell growth
1st mutation leads to a susceptible carrier
2nd mutation leads to cancer
What are the steps of Tumourigenesis?
Normal cell –> INITIATION –> Initiated cell –> PROMOTION–> Pre-neoplastic cells –> PROGRESSION
INITIATION: Irreversible genetic change to the cell (genetic or due to carcinogen e.g. tobacco smoke)
PROMOTION: Further genetic changes due to further mutation (e.g. increased exposure to smoke).
Associated with genomic instability and PERTURBATION of oncogenes and TSGs (p53, retinoblastoma etc.)
PROGRESSION: Errors in genes involved with cell division, cell death and DNA repair
Cells now have metastatic potential to move to diff body areas
Problem: ** No cancers have same genetic changes**
CANCER PATHOGENESIS
What are the effects of a mutation in the genome of somatic cells?
- Alters genes that promote apoptosis
- Inactives tumour suppressing genes (TSGs)
- Activates tumour growth promoting genes :(
CANCER PATHOGENESIS
Steps?
- Normal cell can undergo DNA damage
- If DNA repair is successful continues as normal cell, if unsuccessful –> mutations in genome of somatic cells occur (3 effects of this stated in another flashcard Q)
- Altered gene products expressed and regulatory gene products lost
- Clonal expansion –> Further mutation –> Heterogeneity –> NEOPLASM
What is Gene vs Genome ?
A gene is made of DNA. Genes (have enough DNA to) code one protein.
A genome is the total DNA in one organism
Colorectal tumorigenesis (overall accumulation rather than sequence is important)
- Loss OR somatic mutation of adenomatous polyposis coli (APC) gene
- DNA hypomethylation (genomic instability) - loss of the methyl group (-CH3) in the 5-methylCYTOSINE
- Mutation of K-ras
- Loss or Mutation of SMAD4
- Loss or Mutation of p53
Which of the genes listed (all tumour suppressor genes, TSG) is NOT a TSG?
APC K-ras SMAD4 p54 MSH2 MLH1
K-ras
Because it is in fact an ONCOGENE (the only one in the tumourigenesis process) hence this is GAINED whereas the TSGs are LOST in the formation of a tumor.
FUNCTION: Signal transduction for cell proliferation.
What genetic changes do oncogenes (gene amplifiers) make?
- Genetic translocation
- Activate mutations
- Activate gene promotors
What genetic changes do TSGs (gene inactivators) make?
- Silence mutations
- Haploinsufficiency (a model of dominant gene action in diploid organisms)
Epigenetic Mechanisms
Promoter Methylation
Promoter Phosphorylation
Histone Deacetylation
What is the hereditary marker for breast cancer?
BRAC1
Define: Epigenetics
Hereditary modification of genetic activity that does NOT involve DNA sequence changes
FUNCTION: alters DNA conformation (structure/shape) within chromatin resulting in an altered gene expression
E.g. DNA methylation and histone modifications can lead to silencing of gene (TSGs). Suppressing transcription of TSGs means cancer cells proliferate
List hallmarkers of cancer?
Replicative potential (limitless)
Sustain angiogenesis (stroma induce blood vessles)
Evasion of apoptosis (programmed cell death)
Ability to invade and metastasis
Evade TSGs (growth suppressors)
Self-sufficiency in growth signals