Cancer genes Flashcards
(19 cards)
What occurs when a clone of cells loses normal controls over growth and differentiation?
Cancers form from the loss of normal controls over growth and differentiation
How many cancer-causing genes have been identified?
More than 100 cancer-causing genes
What mediates one component of cell regulation?
External signals from growth factors
Name three examples of growth factors.
- Platelet-derived growth factor
- Epidermal growth factor
- Steroid hormones
What happens when a growth factor binds to its receptor?
It activates the receptor and triggers signal transduction molecules
What is the role of protein kinases in signal transduction?
They alter the activity of target proteins through phosphorylation
What are the ultimate results of signal transduction pathways?
Regulation of DNA transcription in the nucleus
What signals tell cells to stop growing and differentiate?
Signals may come from polypeptides, steroid hormones, direct contact with adjacent cells, or internal programs
What is the result of signals transduced to the nucleus?
Repression of genes that promote cell division and induction of genes that inhibit entry into the cell division cycle
List the substances that regulate cell growth.
- Growth factors
- Specific receptors for growth factors
- Signal transduction molecules
- Nuclear transcription factors
What leads to the emergence of a cancer cell?
Accumulation of mutations in cancer-causing genes
What is the multi-hit concept of carcinogenesis?
It requires more than one mutation for cancer development
What does the two-hit model of carcinogenesis suggest?
At least two mutations are required to create a retinoblastoma
What distinguishes familial retinoblastoma from sporadic retinoblastoma?
Familial is often bilateral, while sporadic is usually unilateral
What is a constitutional mutation?
A mutation present in all cells of the body
What is the nature of the second hit in the two-hit model?
It is a loss-of-function mutation
What can produce the second hit in retinoblastoma?
- Point mutation
- Deletion
- Hypermethylation of the RB1 promoter region
What is the implication of Knudson’s two-hit hypothesis?
Inherited mutations may be the same as those causing common cancers through somatic mutation
What types of tumors frequently exhibit somatic loss-of-function mutations of the RB1 gene?
- Small-cell lung carcinoma
- Breast carcinoma
- Glioblastoma
- Osteosarcoma
