Types of cancers and mutations Flashcards
What is cancer?
The abnormal growth of cells in an uncontrolled way that can spread and metastasise into other tissues. Occurs as a result of accumulation of mutations in cell (multiple mutations, usually 3-20)
Results in uncontrolled growth and proliferation
What is the difference between a benign and malignant tumour?
- benign tumours tend to grow slowly and not spread
- malignant tumours grow rapidly and disorderly and invade surrounding tissues (mestastasis)
What are the 4 classes of cancers?
- Carcinomas
- Sarcomas
- Lymphomas
- Leukaemias
What is the most common type of cancer?
Carcinomas - 85% of cancer cases
What are the percentage of cases of each of the four types of cancers?
- Carcinomas- 85% of cancers
- Sarcomas- 12% of cancers
- Lymphomas and leukaemia account for 3% of cases together
What are carcinomas?
These are cancers that begin in epithelial cells that cover internal organs, cover the outside of the body and the body cavities e.g. chest and abdominal.
There are four types:
- squamous cell carcinoma- found in the flat squamous cells found in the skin and lining of throat and oesophagus
- adenocarcinoma- starts in glandular cells (Adenomatous cells)
- transitional cell carcinoma- these are cells that stretch as organs expand e.g. lining of the bladder
- basal cell carcinoma- basal cells form the deepest layer of the skin
What are sarcomas?
- Highly malignant cancers- hard to treat
Is found in cells in the supporting tissue of the body- connective tissues e.g. bones, cartilage, tendons, fibrous tissue that support organs
e.g.
osteosarcoma- bone tumours
liposarcoma- fat cell tumout
fibrosarcoma- tumour in fibrous tissue
What are lymphomas?
Cancers that begin in the lymph nodes/glands and cells of the lymphatic/immune system
- T-cells, B-cells, NK cells in the lymph nodes can become cancerous and metastasise to other organs
What are leukaemias?
Cancers of the white blood cells- highly proliferative and accumulate in the bloodstream
What factors determine the stage of cancer?
- The site of the primary tumour
- Size of tumour
- how far tumour has invaded local tissues/structures
- Has it spread to regional lymph nodes?
- Has it metastasised to other regions of the body?
What happens to the prevalence of cancer as we age?
Likelihood increases as we age, the cells undergo more cell divisions and therefore increases the opportunity for mistakes in gene copying and therefore increased chance of mutations.
What can cause mutations that lead to cancer?
- Mistakes in DNA replication- incorrect bases being assigned
- Nucleotides within the DNA undergo chemical changes spontaneously-this causes altered base sequences
- Effect of mutagenic agents- molecules generated endogenously by normal cell metabolism- e.g. reactive oxygen species can cause strand breaks and lesions in DNA
- mutagenic agents e.g. X-rays, UV radiation
- viruses- one of the biggest risk factors for developing cancer after smoking
What are the four most prevalent cancers in the UK?
In order of most to least:
Breast cancer (15%)
Prostate (14%)
Lung (13%)
Bowel (11%)
Together, these account for 53% of cancers in the UK
Give some cancer statistics for the uk
- Approximately 1000 cases of cancer are diagnosed per day in the UK
- Approximately 450 cancer deaths per day
- 50% of uk patients survive
- 38% of UK cancer deaths are preventable
What are the most common cancers in children?
- Most common is leukaemia
- Lymphomas
- Brain and intracranial tumours
What are the common risk factors for cancer?
- Smoking
- Genetics
- Diet
- Age
- Alcohol
- Obesity
- Sunlight exposure
- HPV
- Asbestos
- Radiation
What are some common mutated genes associated with cancer?
TP53
BRCA1/2
PTEN
What are examples of oncogenic viruses and the cancers they cause?
- Epstein-Barr virus- Burkitt’s lymphoma
- HBV + HCV- Hepatocellular carcinoma
- HPV- cervical carcinoma
- AIDs- Kaposi’s sarcoma
What are the two methods of viral carcinogenesis (normal cells become cancerous)?
- Direct: The virus acts within the cell that will become a tumour e.g. HPV
The viral genomes form episomes ( circular DNA plasmid) or integrate into the host DNA
This will cause the expression of oncogenes (growth genes) in the cells that are always turned on causing repetitive proliferation - Indirect- virus acts from outside the cell that will form the tumour e.g. HBV, HCV
The cell is infected with the virus
The infected cell will release chemokines that cause the recruitment of inflammatory cells
This creates a chronic inflammatory microenvironment which can cause tissue damage and mutations arise that can lead to cancer
What is dysplasia?
The increase in growth of immature cells with abnormal and variable appearances. These cells are not cancerous
What is metaplasia?
When one cell type is changed into another cell type that is not normal found in that area.
What is neoplasia?
The abnormal and uncontrolled growth of cells in the body to form a tumour ( can be benign or malignant)
What is the process of carcinogenesis?
INITIATION- Change in the genetic genome of the cell potentially by exposure to carcinogens. Rarely becomes cancerous due to repair mechanisms
PROMOTION- the mutated cell is stimulated to grow and divide faster
PROGRESSION- Rapid increase in tumour size and more mutations- neoplastic cells
METASTASIS- invasion into other areas
What is atrophy?
- progressive shrinkage of muscle- if not excercised
What is hypertrophy?
- increase and growth of muscle cells
What is hyperplasia?
An increase in number of normal cells- all exhibit normal regulatory control mechanisms
How do DNA and RNA viruses cause cancer?
DNA viruses (HHV, HPV,EBV,HBV)
The viral genome can persist in the infected cells as a episome (circular DNA) eg. HHV and promote the expression of proteins that promote proliferation or that inhibit tumour suppressor genes e.g. Rb and p53
RNA viruses (HCV, HTLV1)
RNA is retro transcribed into DNA and incorporated into the host genome (provirus) and allows it to replicate. RNA viruses cause carcinogenesis in two ways:
1. Providing a gene that alters growth: the RNA viruses can contain an extra gene additional to the sequences needed for viral replication
2. Insertional mutagenesis: the virus integrates into the host genome close to a host gene that regulates growth (i.e. a GF) and upregulates its expression
