ABSTRACT
Tumor growth of colorectal cancers accompanies upregulation of cyclooxygenase-2, which catalyzes a conversion step from arachidonic acid to prostaglandin H(2) (PGH(2)). Here, we compared the expression levels of thromboxane synthase (TXS), which catalyzes the conversion of PGH(2) to thromboxane A(2) (TXA(2)), between human colorectal cancer tissue and its accompanying normal mucosa. It was found that TXS protein was consistently upregulated in the cancer tissues from different patients. TXS was also highly expressed in human colonic cancer cell lines. Depletion of TXS protein by the antisense oligonucleotide inhibited proliferation of the cancer cells. This inhibition was rescued by the direct addition of a stable analogue of TXA(2). The present results suggest that overexpression of TXS and subsequent excess production of TXA(2) in the cancer cells may be involved in the tumor growth of human colorectum.
Subject(s)
Cell Proliferation/drug effects , Colorectal Neoplasms/enzymology , Thromboxane A2/pharmacology , Thromboxane-A Synthase/metabolism , Up-Regulation/drug effects , Blotting, Western , Cell Line, Tumor , Colorectal Neoplasms/pathology , Humans , Immunohistochemistry , Oligonucleotides/pharmacologyABSTRACT
Increased release of thromboxane A(2) (TXA(2)) has been shown to be involved in inflammatory bowel diseases. In the present study, we have investigated the effect of a stable TXA(2) analogue (STA(2)) on the electrical parameters in isolated human colonic mucosa. In the human mucosa set between Ussing chambers, STA(2) stimulated Cl- secretion in a concentration-dependent manner with an EC(50) of 0.06 microm. The STA(2)-induced Cl- secretion was significantly inhibited by ONO-3708 (10 microm), a specific TXA(2) receptor antagonist. The effect of STA(2) (0.3 microm) was independent of the colonic segment from which the tissue was obtained, from caecum to rectum. Chromanol 293B, an inhibitor of the cAMP-dependent KvLQT1 channel, attenuated the STA(2)-induced Cl- secretion in the human colonic mucosa (IC(50) value 1.18 microm). We found that KvLQT1 mRNA and protein were expressed in all the tested segments of the human colon. The STA(2)-induced Cl- secretion was significantly inhibited by 8-bromo-2'-monobutyryladenosine-3',5'-cyclic monophosphorothioate (50 microm), a membrane-permeant cAMP antagonist. STA(2) (0.3 microm) significantly increased the intracellular cAMP levels and the short-circuit current via TXA(2) receptor in a human colonic cell line. These results suggest that the TXA(2)-induced Cl- secretion in the colon is mediated via the cAMP pathway in addition to the Ca(2+)-calmodulin pathway which was previously reported.
Subject(s)
Chlorine/metabolism , Colon/metabolism , Cyclic AMP/metabolism , Intestinal Mucosa/metabolism , Thromboxane A2/pharmacology , Aged , Animals , Colon/drug effects , Dose-Response Relationship, Drug , Female , Humans , In Vitro Techniques , Intestinal Mucosa/drug effects , Male , Middle Aged , Rats , Rats, Wistar , Signal Transduction/drug effects , Species SpecificityABSTRACT
We investigated expression levels of Na(+),K(+)-ATPase alpha-isoforms and their ATPase activities in human colorectal cancer tissue and the accompanying normal mucosa. A decrease in expression of the alpha1-isoform protein was observed in all sampled cancer tissues compared with the normal mucosae. The level of ouabain (5 microM)-sensitive Na(+),K(+)-ATPase activity in carcinomas was 81+/-5% that of in the normal mucosae. The mRNA expression of alpha2- and alpha 4-isoforms was decreased in almost all the carcinoma samples. Interestingly, the expression level of the alpha 3-isoform protein in the cancer tissue was higher than that of the normal mucosa. These results indicate that a decrease in the alpha1-isoform expression and an increase in the alpha 3-isoform expression may be associated with colorectal cancer.
Subject(s)
Carcinoma/genetics , Colonic Neoplasms/genetics , Down-Regulation , Sodium-Potassium-Exchanging ATPase/metabolism , Up-Regulation , Asian People , Carcinoma/metabolism , Cell Line, Tumor , Colonic Neoplasms/metabolism , Female , Gene Expression , Gene Expression Regulation, Enzymologic/drug effects , Gene Expression Regulation, Neoplastic/drug effects , Humans , Isoenzymes/genetics , Isoenzymes/metabolism , Male , Ouabain/metabolism , RNA, Messenger/metabolism , Sodium-Potassium-Exchanging ATPase/geneticsABSTRACT
The expression of mRNAs encoding a human nongastric proton pump (ATP1AL1) in the colorectum was investigated. The real-time PCR gave significant levels of signals not only in the distal part of human colon and rectum, but also in the proximal part of the colon. ATP1AL1 mRNA was overexpressed in 12 out of 20 human colorectal adenocarcinomas compared with the level in the accompanying normal mucosa. It is noted that astonishing levels of the mRNA overexpression were found in 4 carcinomas, which were detected even by Northern blot. The very high levels of ATP1AL1 mRNA expression in some cancer tissues may be connected to an unknown specific pathophysiological condition.
Subject(s)
Colon/metabolism , H(+)-K(+)-Exchanging ATPase/metabolism , Proton Pumps/metabolism , Rectum/metabolism , Sodium-Potassium-Exchanging ATPase/metabolism , Adenocarcinoma/metabolism , Animals , Carcinoma/metabolism , Colorectal Neoplasms/metabolism , Computer Systems , H(+)-K(+)-Exchanging ATPase/genetics , Humans , Polymerase Chain Reaction , RNA, Messenger/metabolism , Rats , Sodium-Potassium-Exchanging ATPase/genetics , Tissue DistributionABSTRACT
It has been demonstrated that the accumulation of alterations in several oncogenes and tumor suppressor genes plays a role in the initiation and progression of esophageal carcinoma. However, to our knowledge, very few studies have described the molecular genetic changes of chromosome arm 14q in esophageal carcinoma. In this study, we examined 35 primary esophageal carcinomas for allelic imbalance on 14q32. Analysis of four polymorphic microsatellite markers identified 13 (37%) tumors exhibiting allelic imbalance on 14q32 in at least one locus. In particular, the allelic imbalance of the D14S267 marker that has been reported in various tumors as having a high frequency of deletion was observed in 10 of 26 informative cases (38.5%). The commonly deleted regions were delineated by markers D14S65 and D14S250 on 14q32. In regard to the macroscopic features of tumor, the 14q allelic imbalance rate of protruding type tumors was higher than that of the ulcerative type. These data suggest that potential suppressor loci on 14q32 are related to the development and progression of esophageal carcinoma.
