Oncology Flashcards
(166 cards)
6 modalities/hallmarks of cancer
- Growth factor independence (GOF)
- Loss of response to anti-growth signals/differentiation signals (LOF)
- Resistance to apoptosis
- Recruitment of blood/lymph
- Invasion and metastasis
- Limitless replicative potential
Growth factor independence
- typically related to gain of function oncogenes
Proto-oncogenes
normal genes with important roles in regulating division, differentation, survival, movement –> mutate to oncogenes (GOF)
PI3K Pathway
- PI3K phosphorylates lipid on the cytoplasmic side of membrane
RTK (e.g. EGF receptor) –> activate PI3K–> converts PIP2 –> PIP3 –> docking site for PH domains (e.g. in AKT)–> AKT/PKB –> phosphorylation of proteins
- Involved in many signaling events
- Disregulation can have significant oncogenic downstream effects
Warburg effect
elevated AKT activity due to PI3K mutation –> increased glucose transport & glycolysis (basis of PET)
PTEN
- most common mutation leading to elevated PI3K activity
- PTEN converts PIP3–> PIP2 (opp. of PI3K)
- usually via deletion of PTEN or silencing of locus
- LOF is usually more common than GOF
Tumor suppressor
genes in which loss of function promotes cancer (e.g. PTEN)
p53
- tumor suppressor gene
- activates cell cycle arrest & apoptosis
- most cancers have p53 mutation
- DNA-binding transcription factor
- regulates
- p21 cyclin inhibitor
- GADD45- DNA repair
- Bax, Puma, Noxa- pro apoptosis
- MDM2- self-regulation
- accumulates in cancer cells b/c loss of autoregulation
Li-Fraumeni Syndrome
patients with one germ-line mutant copy of p53 gene –> prone to leukemias, sarcomas, breast, brain cancers associated with loss of remaining functional p53 allele in those cells –classic example of “loss-of-heterozygosity” (LOH).
Apoptosis
- highly ordered, ATP-dependent process-proteins, subcellular components dismantled by proteases (“caspases”)and nucleases
- membrane blebbing produces “apoptotic bodies” containing cellular debris, which are then engulfed by macrophages and other cells
- avoids release of cellular components that could trigger a damaging inflammatory response.
Caspases
- proteases that use conserved cysteine residue in their active site to cleave other proteins after aspartate residues in apoptosis
- initiators
- effectors/exectuioners
- present as procaspases until stimulus initates apoptosis
Intrinsic apoptotic pathway
mitochondrial membrane loses integrity –> cytochrome C released from mitochondria –> binds Apaf 1 to form apoptosome –> recruits procaspase 9 –> cleaves executioner caspases –> apoptosis
BCL related proteins
- promote apoptosis - Bax, Bax
- inhibit apoptosis - Bcl2
- apoptosis determined by equilbirium of these stress-responding factors
Extrinsic apoptotic pathway (death receptor)
- Fas (or other TNF death receptor) receptor binds FasL/–> recruits FADD/TRADD—> recruits intiators 8 and 10 which autoactivate and trigger effectors 8/10 –> DISC
Ways cancers bypass apoptosis
- over expressing antiapoptotics like Bcl2
- downregulating proapoptotics like Bax, Bak
- losing p53 which induces proapoptotics Bax, Puma, Noxa
- downregulating death receptors Fas, Trail
Hayflick Limit
- replicative senescence:
- most cells: division of cell –> some DNA lost –> limits number of replications
- if continued replication –> breakage fusion bridge cycle would occur –> inappropriate fusing of chromosomes
Telomerase
- telomerase adds extra telomeric DNA to some some cells (stem cells, lymphocytes)
- dysregulation ensures stable chromosomes for cancer
Angiogenic switch
- recruitment of blood vessels to ensure tumor growth > 2mm
- balance between
- inhibitors
- statins
- thrombospondin
- activators
- VEGF
- FGF
- EGF
- PDGFB
- inhibitors
Tumor vasculature
highly anomalous because of inconsistent equilibrium between pro/anti angiogenic factors
VEGF
- vascular endothelial growth factor –> stimulates EC division, survival, differentiation, movement –> master regulator
- main form = VEGF A
- binds to tks on ECs (VEGFR1 and 2) –> angiogenesis
VEGF blockers
antiangiogenic therapy
- bevacizumab = mab
- sunitinib/sorafenib = kinase inhibitors
Seed and Soil Metastasis
- cancer cells follow venous and lymphatic drainage
- some tumor cells may adher in or survive better in certain organs
Importance of Philadelphia chromosome
- encodes fusion protein BCR-ABL = oncogene with abnormal tk activity
- t (9;22) –> BCR intiator, ABL gene
- present in 100% CML, 30% AML
- Tx: Gleevec/Imatinib
FFPE
Formalin fixed parafin embedded –> cut tumor specimen –> laser capture DNA –> PCR –> identify markers, resistance



