Abstract
BackgroundColon cancer is one of the most aggressive human malignancies, with a very poor prognosis. Although it has been suggested that different isoforms of the lymphoid enhancer factor (LEF-1) have opposing biological activities, the biological outcome of aberrant LEF-1 activation in colon cancer is still unclear. The aim of this study was to evaluate the effect of the different LEF-1 phenotypes on the growth of colon carcinoma cell lines. A deeper understanding of these processes might improve the targeted therapies for colon cancer by regulating the expression of LEF-1.MethodsThe role of different isoforms of LEF-1 on the growth of human colon carcinoma cell lines (SW480 and HT-29) was studied using various in vitro and in vivo assays. In vitro proliferation, migration, adhesion and apoptosis of the cells stably transfected of different isoforms of LEF-1 were monitored by MTT assay, carboxyfluorescein diacetate–succinimidyl ester staining, annexin V staining, ECM adhesion assay and transwell assay, respectively. In nude mice, the formation of neovasculature in the tumors formed by our constructed cells was measured by immunohistochemistry. All the data were analyzed using a t test, and data were treated as significant when p < 0.05.ResultsOverexpression of truncated LEF-1 (LEF-1-ΔL) in the colon cell lines, SW480 and HT29, inhibited their growth significantly in vitro and in vivo, but the full-length LEF-1 (LEF-1-FL) promoted the proliferation of HT29. Inactivation of Wnt signaling by LEF-1-ΔL reduced the expression of CXCR4 in colon cell lines, which may lead to a decrease in activities such as migration, adhesion and survival. In nude mice, the formation of neovasculature as well as an increase in tumor volume were inhibited by the short isoform of LEF-1. LEF-1-FL, however, caused an increase in all these parameters compared with controls.ConclusionsThese findings suggest that LEF-1 might play an important role in colon carcinogenesis by acting as a regulator. Enhanced expression of LEF-1-FL, which occurs frequently in colon cancer, may be a new target for clinical therapy.
Highlights
Colon cancer is one of the most aggressive human malignancies, with a very poor prognosis
In 81.8% (18/22) of the colon cancer cases we studied, the full-length isoform of Lymphoid enhancer factor 1 (LEF-1) was expressed more in colon tumors in situ relative to that in adjacent tissues and normal tissues; but the short isoform of LEF-1 was expressed to a lower extent in tumors compared with that in adjacent tissues and normal tissues (Figure 1A)
Two forms of LEF-1 could be found in Jurkat and Raji cells, while none were detected in HeLa and HT29 cells (Figure 1B)
Summary
Colon cancer is one of the most aggressive human malignancies, with a very poor prognosis. It has been suggested that different isoforms of the lymphoid enhancer factor (LEF-1) have opposing biological activities, the biological outcome of aberrant LEF-1 activation in colon cancer is still unclear. The full-length LEF-1 (LEF-1-FL) isoform, containing the β-catenin binding domain, can promote cell proliferation and inhibit differentiation through. This LEF-1 function may be abolished by the expression of a truncated LEF-1 protein that lacks the β-catenin binding domain. This shorter LEF-1 transcript (LEF-1-ΔL) is thought to be an inhibitory isoform [9,10], owing to its ability to interact with cofactors that bind LEF-1-FL, as well as compete for DNA binding sites, and has been termed “growth suppressing”
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