|
|
|
 |
| |
Causes |
|
 |
 |
Gastro-entero-pancreatic neuroendocrine (GEP NE) tumours produce and secrete excessive amounts of peptides and amines that are normally produced by the body in smaller amounts. These substances, which come from the neuroendocrine cell system, exert their activities through 4 different modes of regulation:
- Endocrine-the agent is produced in one cell type and released into the bloodstream. Its action is exerted via receptors located far from the source of production
- Paracrine-the agent is produced in one cell and acts on a nearby cell. It is released into the intracellular space or released directly on the receptor of a nearby cell via direct connections
- Autocrine-the cell produces a substance that is secreted and directly stimulates the same cell through a surface receptor
- Neurocrine-the agent is produced within neuronal cells and released directly into the synaptic space, and acts on another cell type
|
|
 |
|
 |
|
Genes involved in GEP NE tumours
Research indicates that the development of GEP NE tumours is associated with the following genes:
- Menin (associated with multiple endocrine neoplasia type I)
- PLCß3
- Ret-proto oncogen (associated with multiple endocrine neoplasia type II, MTC)
- PRAD
|
|
|
|
Biology
of GEP NE tumours
The biology of GEP NE tumours is not fully
understood, but 4 possible components have been identified:
- Growth factors/receptors, including
insulin-like growth factor I (IGF-I), transforming growth factor-alpha
(TGF-α ), the transforming growth factor-beta (TGF-ß)
family, and the platelet-derived growth factor (PDGF) family
- Adhesion molecules such as CD44,
particularly those with mutations in exons v-6, v-9, and v-10.
These substances are associated with a poor prognosis in many
GEP NE tumours
- Angiogenic factors, such as basic
fibroblast growth factor (FGF) and vascular endothelial growth
factor (VEGF). These play a role in angiogenesis, an important
part of tumour growth
- Seven transmembrane receptor (G-protein coupled)
cell-growth signals. These are activated and work
in tandem with traditional growth factors (acting through tyrosine
kinase receptors) to help fuel the development of GEP NE tumours
Growth Factors / Receptors
ICF-I
TGF-α, EGF-R
TGF-β, family
PDGF family
Adhesion Molecuses
CD44 (exon v6, v10)
Angiogenetic Factors
b-FGF
VEGF
Seven Transmembrane Receptor
(G-Protein Coupled) Cell-Growth Signals
|
|
|
|
Causes of carcinoid syndrome
Carcinoid syndrome mostly develops after a carcinoid tumour has metastasised to other organs (usually the liver) and released a large concentration of peptides and biogenic amines into circulation.
The probability of occurrence and the associated severity of carcinoid syndrome depend on several factors, including size and location of the tumour and the degree of metastasis. The incidence of metastases is almost 100% in tumours larger than 2 cm and less than 2% in tumours smaller than 1 cm. |
|
|
|
|
|
|
|
|
|
|
