Oncology

Question 0

MYC (tie to cancer)

Answer 0

a TF from chromosome 8,
RAPIDLY activated to promote cell division, & modulates telomerase.
*over-expressed in many tumors, esp. Burkitt’s Lymphoma

Question 1

oncogenes (examples)

Answer 1

genes that are activated (from proto-oncogenes) to promote unregulated growth => cancer
Ex: TGF-a, EGFR, Ras, MYC, Cyclins

Question 2

Tyrosine kinase

Answer 2

enzyme that phosphorylates protein tyrosine residues, important for intracellular signalling.
mutations in:
Bcr-Abl => CML (constitutively active)
Jak2 => polycythemia vera (loss of inhibition)

Question 3

RAS (tie to cancer)

Answer 3

oncogenic signal transduction protein,

1. stimulates MAP-kinase pathway (via Raf)
2. auto-inactivation (by binding Gap)
   * point muts in RAS = #1 mut in cancers => uncontrolled prolif.

Question 4

p53

Answer 4

tumor suppressor gene, #1 target of cancer chemoTx!
= G1-S checkpoint, to keep cells from progressing if damaged DNA
* loss of function –> mutated (cancer cells) progress past checkpoint

Question 5

proteins in Intrinsic Apoptosis

Answer 5

Pro-apoptotic: Bax & Bak => increase mitochondrial membrane permeability -> release cytochrome C
Anti-apoptotic: Bcl-2 & Bcl-xl => inhibit bax & bak
*over-expression of Bcl-2 -> Follicular B cell lymphoma! t(14,18)

Question 6

DNA repair mechanisms & assoc. cancers

Answer 6

1. Mismatch Repair: single base mismatches => HNPCC
2. Nucleotide Base Excision Repair: correct bulky lesions (disrupted helical architecture) => Xeroderma pigmentosa
3. Double Strand Break Repair: cut out cross-links
   => Fanconi anemia, Ataxia telangectasia, Bloom syndrome

Question 7

Initiators

Answer 7

agents that cause DNA DAMAGE, but not enough to induce cancer alone.
(exposure to initiators 1st, then promoters => cancer)
ie: chemicals, radiation, oncogenic viruses

Question 8

Promoters

Answer 8

agents that INDUCE CANCER in already initiated/altered cells
* only cause cancer IF pre-existing DNA damage.
(must occur after exposure to initiator)
ie: hormones, drugs, phenols