Cell Cycle Control System

Lecture 21

Checkpoints

where cell cycle stops until a go ahead is received

G1 Checkpoint (GO AHEAD)

G1 → S, G2, M → divides

G1 Checkpoint (NO GO AHEAD)

G1 → exits cycle → enters non dividing state (G0)

Cyclins and Kinases

regulatory protein complexes that regulate the cell cycle

Internal Signals

monitors the cell’s internal state, ensuring the cell is ready to proceed to the next stage

External Signals

originates outside the cell to determine if division is necessary, suppressing or encouraging cell division

Anchorage dependence

cell must be attached to something in order to divide

Cancer cells

have no anchorage dependence or density dependent inhibition (stops division); can signal growth without a factor

Henrietta Lacks

her (HeLa) cervical cancer cells were studied to see how cancer cells divide & led to development of treatments

Transformation

a process that is thought to cause cells (e.g. cancer cells) in culture to divide indefinitely 

Tumors

collection of cancer cells that are not eliminated by the immune system; benign if they don’t move, malignant if they invade surrounding tissues (metastasis)

Metastasis

the export of cancer cells to other parts of the body, potentially forming additional tumors

Cancer treatments

• Radiation: damages the DNA in cancer cells

• Chemotherapy: interferes with steps of the cell cycle

• Immunotherapy: new treatment