PubMed · 14467392
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F LUNDMARK, B HEDENSIO. 1961-10-20. [Carcinoids].. https://pubmed.ncbi.nlm.nih.gov/14467392/
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Progression of colorectal cancer (CRC) involves spatial and temporal occurrences of epithelial-mesenchymal transition (EMT), whereby tumour cells acquire a more invasive and metastatic phenotype. Subsequently, the disseminated mesenchymal tumour cells must undergo a reverse transition (mesenchymal-epithelial transition, MET) at the site of metastases, as most metastases recapitulate the pathology of their corresponding primary tumours. Importantly, initiation of tumour growth at the secondary site is the rate-limiting step in metastasis. However, investigation of this dynamic reversible EMT and MET that underpins CRC morphogenesis has been hindered by a lack of suitable in vitro models. To this end, we have established a unique in vitro model of CRC morphogenesis, which we term LIM1863-Mph (morphogenetic). LIM1863-Mph cells spontaneously undergo cyclic transitions between two-dimensional monolayer (migratory, mesenchymal) and three-dimensional sphere (carcinoid, epithelial) states. Using RNAi, we demonstrate that FZD7 is necessary for MET of the monolayer cells as loss of FZD7 results in the persistence of a mesenchymal state (increased SNAI2/decreased E-cadherin). Moreover, FZD7 is also required for migration of the LIM1863-Mph monolayer cells. During development, FZD7 orchestrates either migratory or epithelialization events depending on the context. Our findings strongly implicate similar functional diversity for FZD7 during CRC morphogenesis.
Carcinoid tumours are rare neuroendocrine tumours. In 2000 the WHO developed a new classification which gives a better description of the characteristics and biological behaviour of the tumour. Their advised designation is gastroenteropancreatic neuroendocrine tumour (GEP-NET). Somatostatin receptor scintigraphy has the highest sensitivity for visualisation of GEP-NETs. In the recent past years new positron emission tomography (PET) tracers have been developed and PET scanning is likely to become an important tool in the near future. Surgical resection is the treatment of first choice for a patient with a GEP-NET. In metastatic disease a number of forms ofpalliative treatment are possible. Cytotoxic chemotherapy seems only to be effective in aggressive, poorly-differentiated tumours. Therapy with somatostatin analogues leads to objective tumour regression in a minority of patients only. New advances in peptide receptor radionuclide therapy using radioactive-labelled somatostatin analoga are showing better results.
Carcinoid tumors are rare, slow-growing neuroendocrine neoplasms that often are indolent and may not become clinically apparent until there has been metastatic spread or evidence of carcinoid syndrome. Recent evidence has revealed that the overall incidence of carcinoid tumors has been steadily increasing, and although the disease was thought to be relatively benign, it is now considered one of increasing malignancy. Carcinoid tumors derive from different embryonic divisions of the gut: foregut carcinoid tumors commonly originate in the lungs, bronchi, or stomach; midgut carcinoid tumors in the small intestine, appendix, or proximal large bowel; and hindgut carcinoid tumors in the distal colon or rectum. Carcinoid syndrome, although rare, is most associated with midgut carcinoid tumors. The diagnosis of a carcinoid tumor often is coincidental with surgery performed for another reason. Treatment and prognosis are dependent on the location of the primary tumor and the degree and extent of metastasis at the time of diagnosis.