In vitro differentiation of HT-29 M6 mucus-secreting colon cancer cells involves a trychostatin A and p27(KIP1)-inducible transcriptional program of gene expression.
Tumor cell dedifferentiation-such as the loss of cell-to-cell adhesion in epithelial tumors-is associated with tumor progression. To better understand the mechanisms that maintain carcinoma cells in a differentiated state, we have dissected in vitro differentiation pathways in the mucus-secretor HT-29 M6 colon cancer cell line, which spontaneously differentiates in postconfluent cultures. By lowering the extracellular calcium concentration to levels that prevent intercellular adhesion and epithelial polarization, our results reveal that differentiation is calcium-dependent and involves: (i) a process of cell cycle exit to G(0) and (ii) the induction of a transcriptional program of differentiation gene expression (i.e., mucins MUC1 and MUC5AC, and the apical membrane peptidase DPPIV). In calcium-deprived, non-differentiated postconfluent cultures, differentiation gene promoters are repressed by a trichostatin A (TSA)-sensitive mechanism, indicating that loss of gene expression by dedifferentiation is driven by histone deacetylases (HDAC). Since TSA treatment or extracellular calcium restoration allow gene promoter activation to similar levels, we suggest that induction of differentiation is one mechanism of HDAC inhibitor antitumor action. Moreover, transcriptional de-repression can also be induced in non-differentiating culture conditions by overexpressing the cyclin-dependent kinase inhibitor p27(KIP1), which is normally induced during spontaneous differentiation. Since p27(KIP1) downregulation in colon cancer is associated with poor prognosis independently of tumor cell division rates, we propose that p27 (KIP1) may prevent tumor progression by, at least in part, enhancing the expression of some differentiation genes. Therefore, the HT-29 M6 model allows the identification of some basic mechanisms of cancer cell differentiation control, so far revealing HDAC and p27(KIP1) as key regulatory factors of differentiation gene expression.
Mayo
Clara
C
Unitat de Biologia Celñlular i Molecular, Institut Municipal d'Investigació Mèdica, Barcelona, Spain.
Lloreta
Josep
J
Real
Francisco X
FX
Mayol
Xavier
X
D002118:Calcium / Q000378:metabolism; D002453:Cell Cycle; D002454:Cell Differentiation; D003110:Colonic Neoplasms / Q000378:metabolism*; D050760:Cyclin-Dependent Kinase Inhibitor p27 / Q000378:metabolism*; D015972:Gene Expression Regulation, Neoplastic; D019073:HT29 Cells; D006655:Histone Deacetylases / Q000378:metabolism; D006801:Humans; D006877:Hydroxamic Acids / Q000494:pharmacology*; D007422:Intestines / Q000166:cytology; D009093:Mucus / Q000378:metabolism*; D011401:Promoter Regions, Genetic / Q000502:physiology; D014158:Transcription, Genetic / Q000502:physiology*
D006877:Hydroxamic Acids; D050760:Cyclin-Dependent Kinase Inhibitor p27; C012589:trichostatin A; D006655:Histone Deacetylases; D002118:Calcium