Butyrate regulates E-cadherin transcription, isoform expression and intracellular position in colon cancer cells

Cell-to-cell adhesion, an important event in differentiation, is impaired during advanced stages of tumorigenesis. In this study, we examined the possible regulation of cell-adhesion proteins by the differentiation agent butyrate in LS174T and HM7 cells, two types of human colon cancer cells that differ in their ability to produce mucin and colonize the liver of experimental animals. The more aggressive, high-mucin-producing cell line (HM7), a clone selected from LS174T cells, showed a scattered and undifferentiated ultramorphological appearance and low basal alkaline phosphatase activity; the proteins β-catenin and E-cadherin, as detected by immunostaining, were expressed in the cells’ nuclei. All of these properties were significantly less pronounced in the less aggressive, low-mucin-producing LS174T cells. In both cell lines, butyrate treatment enhanced cell-to-cell interaction, alkaline phosphate activity, translocation of β-catenin and E-cadherin from the nuclei to the membrane junctions, and transcription and translation of the 120-kDa E-cadherin isoform, but not of its 100-kDa isoform. Analysis of possible mechanisms of E-cadherin up-regulation revealed that butyrate induces the release of nuclear proteins from the E-cadherin promoter sequence, reducing transcription repression. We suggest that butyrate activates E-cadherin transcription through translocation of nuclear transcription factors bearing specific repressor activity. We surmise that abrogation of nuclear 100-kDa E-cadherin and β-catenin expression following butyrate treatment is related to the control of E-cadherin gene transcription. © 2000 Cancer Research Campaig

Butyrate down-regulates CD44 transcription and liver colonisation in a highly metastatic human colon carcinoma cell line

Over-expression of the adhesion molecule CD44 and its splice variants, especially CD44v6, is associated with poor prognosis and metastasis. We aimed at regulating the expression of CD44 in the highly metastatic human colon cancer cell line HM7 and thereby affecting its metastatic ability. HM7 cells show constitutive expression of CD44 standard and variants isoforms, which were significantly down-regulated by treatment with butyrate. Butyrate significantly inhibited transcription of the CD44 gene and abolished epidermal growth factor-mediated up-regulation of the reporter gene luciferase subcloned upstream to the CD44 promoter (−1.1 kb) and transfected to HM7 cells. Nuclear proteins from butyrate-treated cells bound to an epidermal growth factor receptor element motif present in the CD44 promoter. Epidermal growth factor receptor element-site directed mutations eliminated the inducibility of the luciferase reporter gene and did not allowed binding of nuclear proteins harvested from butyrate-treated cells. Butyrate induced CD44 gene repression by specifically interacting with an epidermal growth factor receptor element nuclear transcriptional factor. This interaction affects CD44 transcriptional activity vis-à-vis in vivo metastatic ability of HM7 cells. These results provide additional insight into the anticarcinogenic properties of butyrate

Bone Marrow Protein Oxidation in Response to Ionizing Radiation in C57BL/6J Mice

The bone marrow is one of the most radio-sensitive tissues. Accidental ionizing radiation exposure can damage mature blood cells and hematopoietic progenitor/stem cells, and mortality can result from hematopoietic insufficiency and infection. Ionizing radiation induces alterations in gene and protein expression in hematopoietic tissue. Here we investigated radiation effects on protein carbonylation, a primary marker for protein oxidative damage. C57BL/6 mice were either sham irradiated or exposed to 7.5 Gy 60Co (0.6 Gy/min) total body irradiation. Bone marrow was obtained 24 h post-irradiation. Two dimensional (2-D) gel electrophoresis and Oxyblot immunodetection were used to discover carbonylated proteins, and peptide mass fingerprinting was performed for identification. 2D gels allowed the detection of 13 carbonylated proteins in the bone marrow; seven of these were identified, with two pairs of the same protein. Baseline levels of carbonylation were found in 78 kDa glucose-related protein, heat shock protein cognate 71 KDa, actin, chitinase-like protein 3 (CHI3L1), and carbonic anhydrase 2 (CAII). Radiation increased carbonylation in four proteins, including CHI3L1 and CAII, and induced carbonylation of one additional protein (not identified). Our findings indicate that the profile of specific protein carbonylation in bone marrow is substantially altered by ionizing radiation. Accordingly, protein oxidation may be a mechanism for reduced cell viability

Protein Oxidation in the Lungs of C57BL/6J Mice Following X-Irradiation

Damage to normal lung tissue is a limiting factor when ionizing radiation is used in clinical applications. In addition, radiation pneumonitis and fibrosis are a major cause of mortality following accidental radiation exposure in humans. Although clinical symptoms may not develop for months after radiation exposure, immediate events induced by radiation are believed to generate molecular and cellular cascades that proceed during a clinical latent period. Oxidative damage to DNA is considered a primary cause of radiation injury to cells. DNA can be repaired by highly efficient mechanisms while repair of oxidized proteins is limited. Oxidized proteins are often destined for degradation. We examined protein oxidation following 17 Gy (0.6 Gy/min) thoracic X-irradiation in C57BL/6J mice. Seventeen Gy thoracic irradiation resulted in 100% mortality of mice within 127–189 days postirradiation. Necropsy findings indicated that pneumonitis and pulmonary fibrosis were the leading cause of mortality. We investigated the oxidation of lung proteins at 24 h postirradiation following 17 Gy thoracic irradiation using 2-D gel electrophoresis and OxyBlot for the detection of protein carbonylation. Seven carbonylated proteins were identified using mass spectrometry: serum albumin, selenium binding protein-1, alpha antitrypsin, cytoplasmic actin-1, carbonic anhydrase-2, peroxiredoxin-6, and apolipoprotein A1. The carbonylation status of carbonic anhydrase-2, selenium binding protein, and peroxiredoxin-6 was higher in control lung tissue. Apolipoprotein A1 and serum albumin carbonylation were increased following X-irradiation, as confirmed by OxyBlot immunoprecipitation and Western blotting. Our findings indicate that the profile of specific protein oxidation in the lung is altered following radiation exposure