Cancer Genetics Flashcards
What are the 3 factors that can cause cancer?
Chemicals (e.g. from smoking) and radiation can damage genes (environment)
Viruses can introduce their own genes into cells (exogenous factors)
By heredity, alterations in genes that make a person more susceptible to cancer can be passed to the next generation (genetics – rare and common)
Define benign and malignant tumour
A benign tumor is a mass of well-differentiated cells that grows slowly, is capsulated and lacks the ability to invade neighboring tissue or metastasize.
A malignant tumor is not self-limited in its growth (escapes apoptosis, is able to produce new blood vessels), cells are poorly differentiated and capable of invading into adjacent tissues, and may be capable of spreading to distant tissues (metastasis)
What are features of microscopic appearance of cancer cells
- Large number of dividing cells
- Large variably shaped nuclei
- Large nucleus to cytoplasm ratio
- Variation in size and shape
- Loss of normal cell features
- Disorganised arrangement
- Poorly defined tumour boundary
What is a characteristic of advanced cancers?
In advanced cancers, there is an overexpression of nucleoporins which form the structural basis of nuclear pores – therefore, the nucleopore indent in the nuclear membrane is caused by an abnormal influx of beta-cotinine into the nucleus. Some important transcription factors can also be over transcribed.
What are carcinomas, sarcomas, lymphomas and leukaemias?
Carcinomas: the most common types of cancer arise from the cells that cover external and internal body surfaces. Lung, breast, and colon are the most frequent cancers of this type (epithelial)
Sarcomas: are cancers arising from cells found in the supporting tissues of the body such as bone, cartilage, fat, connective tissue and muscle
Lymphomas: are cancers that arise in the lymph nodes and tissues of the body’s immune system
Leukaemias: are cancers of the immature blood cells that grow in the bone marrow and tend to accumulate in large numbers in the bloodstream
What is the most common childhood cancer?
Leukemias, which arecancersof the bone marrow and blood, are themost common childhood cancers. They account for about 30% of allcancers in children. Themost common typesinchildrenare acute lymphocytic leukemia (ALL) and acute myelogenous leukemia (AML).
What are the 6 hallmarks of cancer and their examples?
- Self-sufficiency of growth signal - Activate H-Ras oncogenes
- Insensitivity to anti-growth signal - Lose retinoblastoma suppressor
- Evading apoptosis - Produce KGF survival factors
- Unlimited replication potential - turn on telomerase
- Sustained angiogenesis - Produce VEGF inducer
- Tissue invasion and metastasis - Inactivate E-cadherin
Define germline mutations vs somatic mutations
Germline mutations are present in the egg/sperm, heritable (family syndromes) and rare - all cells affected in child.
Somatic mutations are those that occur in non-germline tissues, non-heritable, and very common. These cells only divide by mitosis and usually mutations in cancer genes accumulate in somatic cells over years until a cell accumulates a sufficient amount of errors to initiate tumour formation. Only cells derived from this one cell are affected.
What are cancer predisposing mutations and how are they identified?
It is possible for cancer-predisposing mutations to occur in the germline. This results in the transmission of cancer-causing genes from one generation to the next, producing families that have high incidence of specific cancers. Positional cloning linkage studies identify cancer germline mutations.
How is linkage mapping done?
Family undergoes linkage analysis where all chromosomes are mapped with the use of polymorphic markers until specific region containing mutation found to preferentially segregate with phenotype. Once chromosome region identified, all genes sequenced and identified.
