Oncology 4 Flashcards
What are the 6 hallmarks of cancer?
- self-sufficiency in growth signals
- insensitivity to anti-growth signals
- evasion of apoptosis
- sustained angiogenesis
- tissue invasion and metastasis
- limitless reproductive potential
In normal cells, growth and division requires external ____s
growth factors
Growth factors are produced by ______ and bind to ______
- other cells
- cell receptors
What do growth factors trigger? What does this in turn trigger?
Growth factors trigger intracellular kinases
These trigger cell division
What is an important characteristic of growth factors regarding chemical composition?
They are diffusible
When does abnormality of growth occur with cancer cells?
- too many receptors and overstimulation of growth
- self-production and release of GFs (stimulate growth)
What type of trigger causes abnormality of growth in cancer cells?
may be genetic or environmental
What are oncogenes?
- small segments of DNA
- can transform normal cells into malignant ones
Where do oncogenes come from?
Activated from “normal” proto-oncogenes by a mutation
What signals a cell to stop reproduction?
anti-growth signals from other cells
What are the anti-growth signals used by other cells to signal a stop in reproduction?
- soluble growth factors
- immobilized inhibitors embedded in the extracellular matrix
- immobilized inhibitors on the surfaces of nearby cells
What causes cells to become insensitive to anti-growth signals?
- stop listening to normal cells
- keep dividing over normal cells that have stopped growing
Anti-growth signals are associated with this point in the cell cycle?
G1 checkpoint
How do nectins and nectin-like substances play a role in normal cells?
- contact inhibition
- limiting movement of cells
What is contact inhibition?
Mitosis is prevented once cells of a tissue come in contact with one another
How do nectins and nectin-like substances play a role in abnormal cancer cells?
- may be deficient
- lack of normal contact inhibition
- overgrowth of cancer cells
What are the phases of the cell cycle?
G0 G1 S G2 M G1 checkpoint
What is the G0 phase?
- resting phase
- cell has left the cycle and stopped dividing
What is the G1 phase?
Cell growth in preparation for increased DNA synthesis
What is the S phase?
DNA synthesis
What is the G2 phase?
Cell growth preceding mitosis
What is the M phase?
Mitosis
What is the G1 checkpoint?
- regulatory step preventing the move into DNA synthesis phase
- prevents cell division
What is another name for tumor suppressor genes?
anti-oncogenes
What do anti-oncogenes decrease when active?
Decrease risk of a cell becoming metastatic (cancerous)
What do anti-oncogenes code for?
proteins that:
- have a repressive effect on the progression through the cell cycle
- promote apoptosis
- do both
Which gene is nicknamed “the guardian of the genome”?
P53 tumor suppressor gene
What does the P53 protein do?
changes gene expression to halt proliferation and trigger apoptosis when DNA is damaged
At what phase in the cell cycle does P53 halt cell division in response to DNA damage?
G1 phase
How often is the P53 gene found to be mutated or disrupted?
in more than 50% of all cancers
Why is P53 gene mutation so bad?
- suppresses normal apoptotic proteins
- cell continues to multiply
