Eukaryotic cells coordinate cell growth with the availability of nutrients in their environment.
Mutation of molecules involved in cell-growth
signaling can result in the uncontrolled cellular
proliferation that is characteristic of
neoplasia.
Signal transduction in
cancer cells is a sophisticated process that involves
receptor tyrosine kinases (RTKs) that eventually trigger multiple
cytoplasmic kinases, which are often
serine/threonine kinases.
A number of tumor models have identified several key cellular signaling pathways that work independently, in parallel, and/or through interconnections to promote cancer development.
Three major signaling pathways that have been identified as playing important roles in cancer include the
phosphatidyl inositol-3-kinase (PI3K)/AKT,
protein kinase C (PKC) family, and
mitogen-activated protein kinase (MAPK)/
Ras signaling cascades.[
↓]
ATM :
ATR :
DNA-PK :
FRAP1 :
kinases :
MAPK :
mTOR :
Paks :
PI-3-K :
PIKK :
PKC :
Ras :
receptor tyrosine kinases :
serine/threonine kinases :
The
mTOR protein kinase receives stimulatory signals from nutrients as well as
Ras and
phosphatidylinositol-3-OH kinase (PI(3)K) downstream from
growth factors. Functioning as a critical growth-control node,
mTOR is the 'mammalian target of rapamycin', a fungal derivative that halts protein synthesis by complexing with immunophilin FK-506 binding protein FKBP12 peptide prolyl cis/trans isomerase.
Officially termed
FRAP1 for FK506 binding protein 12-rapamycin associated protein 1, mTOR is a
serine/threonine kinase that regulates regulates
translation and
cell division. FRAP1 (mTOR) is an
evolutionarily conserved member of the
phosphoinositol kinase-related kinase (PIKK) family that includes
DNA-PK,
ATM,
ATR and several other proteins. mTOR participates in the
regulation of cell growth through initiation of gene translation in response to nutrients by integratating input from multiple upstream pathways, including
growth factors,
mitogens,
leucine, insulin, and nutrients. mTOR initiates translation by activating the ribosomal p70S6k protein kinase (S6K1) and by inhibiting the eIF4E inhibitor 4E-BP1. FRAP1 is considered to be involved in numerous additional cellular functions including actin organization, membrane trafficking, secretion, protein degradation, protein kinase C signaling, ribosome biogenesis and tRNA synthesis. mTOR may contribute to the regulation of two pathways, referred to as TORC1 and TORC2 (for TOR Complex 1 and 2).
Components of the
Ras and
PI(3)K signalling pathways are
mutated in most human
cancers. The high frequency of
mutations in these pathways suggests that the loss of
growth-control checkpoints and the promotion of cell survival in nutrient-limited conditions may be an obligate event in
carcinogenesis.[
r]
p21-activated kinases (
Paks) are
serine/threonine kinases that function as downstream nodes
oncogenic signalling pathways. Paks are well-known
regulators of
cytoskeletal remodelling and cell motility that promote cell
proliferation, regulate
apoptosis and accelerate
mitosic abnormalities, resulting in
tumorigenesis and cell invasiveness. Alterations in Pak expression have been detected in human tumours
Signal transduction in cancer cells is a sophisticated process that involves
receptor tyrosine kinases (RTKs) that eventually trigger multiple
cytoplasmic kinases, which are often
serine/threonine kinases. A number of tumor models have identified several key cellular signaling pathways that work independently, in parallel, and/or through interconnections to promote cancer development. Three major signaling pathways that have been identified as playing important roles in cancer include the
phosphatidyl inositol-3-kinase (PI3K)/AKT,
protein kinase C (PKC) family, and
mitogen-activated protein kinase (MAPK)/
Ras signaling cascades.
Faivre S,
Djelloul S,
Raymond E.
New paradigms in anticancer therapy: targeting multiple signaling pathways with kinase inhibitors.
Semin Oncol. 2006 Aug;33(4):407-20.
~
activator ~
cadherins ¤
Cancer ¤
carcinogenesis ~
cyclin-dependent kinases ~
cytokines ~
gene regulation ¤
genetic predispositon~
growth factors ¤
oncogenes ¤
malignant transformation ¤
mitogens ¤
mutagens ¤
neoplasia ¤
non-mutagenic carcinogens ¤
p53 ¤
proliferation ¤
proto-oncogenes ~
promoters ¤
Ras ¤
Rb ~
receptor tyrosine kinases ~
regulatory proteins ~
replication ~
repressor ~
response elements ~
retrotransposons ~
restriction enzmes ~
reverse transcriptase ~
Rho GTPase ~
ribosomes ~
serine/threonine kinases ¤
signaling molecules ~
silencers ¤
T-antigens ¤
TP53 ~
transcription ~
transcription factors ~
translation ¤
tumor antigens ¤
tumor suppressors ¤
tumorigenic viruses ¤
viral carcinogens ¤
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Labels: cell-growth signaling, FRAP1, MAPK/Ras, mTOR, PI3K/AKT, PIKK, PKC, RTK, serine/threonine kinases, signal transduction