Document Detail

Calcium, calcium-sensing receptor and colon cancer.
MedLine Citation:
PMID:  18725175     Owner:  NLM     Status:  MEDLINE    
There is much evidence that dietary Ca(2+) loading reduces colon cell proliferation and carcinogenesis in humans and rodents, but during carcinogenesis it becomes ineffective or even tumor-promoting. We are beginning to see how Ca(2+) balances the continuous massive cell production in colon crypts by driving the terminal differentiation and eventually the apoptosis of the cells mainly on the mucosal surface, and how this Ca(2+) control is lost during colon carcinogenesis. The rapid proliferation of the transit-amplifying (TA) progeny of the colon stem cells is driven by the so-called "Wnt" signaling mechanism, which involves the stimulation of proliferogenic genes such as those for c-Myc and cyclin D1 and the silencing of the gene for the cell cycle-stopping p21(Cip1/WAF1) protein by nuclear beta-catenin*Tcf-4 complexes. TA cells avoid mitotic damage and premature apoptosis by expressing the protein survivin. It appears that TA cell cycling stops and terminal differentiation starts when the cells reach a higher level in the crypt where there is enough lumenal Ca(2+) to stimulate the expression and activation of CaSRs (Ca(2+)-sensing receptors), the signals from which stimulate the expression of E-cadherin. Along with this, the APC (adenomatous polyposis coli) protein appears and some of it enters the nucleus. There it makes the TA cells susceptible to the eventual apoptotic balancing by stopping survivin expression and the beta-catenin*Tcf-4 complex from driving further cell cycling by releasing beta-catenin from the nucleus, and delivering it to cytoplasmic APC*axin*GSK-3beta complexes for ultimate proteasomal destruction. Cytoplasmic beta-catenin is then prevented from returning to the nucleus by either being intercepted and destroyed by APC*axin*GSK-3beta complexes or locked by the emerging E-cadherin into membrane adherens junctions which tie the cell into the sheet of proliferatively shut-down cells with APC-dependent cytoskeletons moving to the mouth of the crypt and onto the flat mucosal surface. A common first step in sporadic colon carcinogenesis is the loss of functional APC which disorients upwardly directed migration and causes the retention of nuclear beta-catenin and proliferogenic beta-catenin*Tcf-4 complexes as well as genomic instability. Eventually the balance between cell proliferation and terminal differentiation and death is radically tipped in favour of proliferation by the appearance of apoptosis-resistant, survivin-expressing clones of Ca(2+)-insensitive cells which are locked into the proliferative, mutation-prone mode because of CaSR-disabling gene mutations which prevent the stimulation of E-cadherin expression and terminal differentiation.
James F Whitfield
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Publication Detail:
Type:  Journal Article; Review     Date:  2008-08-23
Journal Detail:
Title:  Cancer letters     Volume:  275     ISSN:  1872-7980     ISO Abbreviation:  Cancer Lett.     Publication Date:  2009 Mar 
Date Detail:
Created Date:  2009-01-28     Completed Date:  2009-02-12     Revised Date:  2011-11-02    
Medline Journal Info:
Nlm Unique ID:  7600053     Medline TA:  Cancer Lett     Country:  Ireland    
Other Details:
Languages:  eng     Pagination:  9-16     Citation Subset:  IM    
Institute for Biological Sciences, National Research Council of Canada, Building M-54, Montreal Road Campus, Ottawa, Ont. Canada K1A 0R6.
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MeSH Terms
Basic Helix-Loop-Helix Leucine Zipper Transcription Factors
Calcium / metabolism*
Cell Nucleus / metabolism
Cell Proliferation
Colonic Neoplasms / metabolism*
Cyclin D1 / metabolism
Cytoplasm / metabolism
DNA-Binding Proteins / metabolism
Glycogen Synthase Kinase 3 / metabolism
Microtubule-Associated Proteins / metabolism
Proto-Oncogene Proteins c-myc / metabolism
Receptors, Calcium-Sensing / metabolism*
Transcription Factors / metabolism
beta Catenin / metabolism
Reg. No./Substance:
0/BIRC5 protein, human; 0/Basic Helix-Loop-Helix Leucine Zipper Transcription Factors; 0/DNA-Binding Proteins; 0/Microtubule-Associated Proteins; 0/Proto-Oncogene Proteins c-myc; 0/Receptors, Calcium-Sensing; 0/TCF4 protein, human; 0/Transcription Factors; 0/beta Catenin; 136601-57-5/Cyclin D1; 7440-70-2/Calcium; EC synthase kinase 3 beta; EC Synthase Kinase 3

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine

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