Cancer Flashcards
A disease in which a single cell escapes normal control over growth and division, and proliferates without limit
Cancer
Any abnormal new growth of cells
-Can compete with normal cells for nutrients
Tumor or Neoplasm
Tumors (neoplasms) can be either
Benign or Malignant
Non-cancerous tumor. It is localized and does not spread
-can cause secondary problems
Benign tumor
Cancerous tumors that resist treatmens, can spread to other parts of the body, and may recur after removal
Malignant Tumor
Most cancer-causing mutations are
-occur post fertilization
Somatic
Mutagens are mostly environmental. The most important are
Smoking and Viral infections
What are two common viral causes of cancer, which are responsible for 30-50% of worldwide cancer cases?
Human papilloma and Hepatitis B and C
Multiple mutations are required to cause
Cancer
Typically about a dozen signal-transduction pathways are altered in a
Tumor cell
Lose the ability to respond to ECM and neighboring cell signals
Cancer cells
Normal cells will cease division when they come into contact with neighboring cells. This is called
Contact inhibition
Normal cells do not survive or divide in the absence of signals from the
Extracellular matrix
Are immune to contact inhibition
Cancer cells
In cancer cells, detachment from other cells and invasion of neighboring tissue is promoted by
Loss of cadherins
Not dependent on signals from the ECM for cell division
Cancer cells
Cancer cells secrete metalloproteases that degrade the ECM and facilitate
Tissue invasion
Mutations in which three classes of genes underlie most cancers?
- ) Caretaker genes
- ) Gatekeeper genes
- ) Oncogenes
Its products prevent or repair damage to DNA
Caretaker genes
Is not oncogenic itself, but promotes further genetic change/increases chance
Loss of caretaker protein function
Its products restrain cell division or induce apoptosis if cells initiate division when they should not
Gatekeeper genes
Loss of gatekeeper protein allows
Uncontrolled proliferation
Its products promote cell growth and division
Oncogenes
Mutations in these genes do not inactivate their proteins, but cause loss of normal control, so that continuous activity drives cell division
Oncogenes
Were discovered as genes mutated in inherited cancer syndromes (e.g. Ptc1 in medulloblastoma)
Tumor suppressor genes
Loss-of-function mutations inactivate
Tumor suppressor protein
Are recessive, meaning both functional copies must be lost to cause a cell to become cancerous
Tumor suppressor genes
In pedigrees, tumor suppressor gene mutations appear
Dominant (even though they are actually recessive)
Caretaker genes prevent or repair DNA damage, what are three examples?
- ) MLH
- ) ERCC1
- ) BRCA-1/2
Gatekeeper genes restrict cell division. What are the two most important?
- ) Rb
2. ) p53
Inhibits the G1/S transition by inhibiting E2F
Rb
Halts cell division or initiates apoptosis in response to DNA damage or other stress
p53
Mutations in caretaker genes cause
Familial cancer syndromes
Mutations in MLH cause lynch syndrome which is associated with defects in which repair pathway?
Mismatch repair
Mutations in ERCC1 result in Xeroderma pigmentosum. This is associated with defects in which repair pathway?
NER
Mutations in BRCA-1/2 result in familial breast/ovarian cancer. This is associated with defects in which repair pathway?
Double-strand break repair
Loss of function mutations in Rb cause retinoblastoma. What are the two forms of the disease?
- ) Sporadic retinoblastoma
2) Familial (inherited) retinoblastoma
Single tumors in one eye of one person in a family
Sporadic retinoblastoma
Tumors are often bilateral and often multiple family members are affected
Familial retinoblastoma