ABSTRACT
To investigate whether the KLF6 gene plays an important role in the development and/or progression of colorectal cancers, we searched for mutations and allelic loss of the KLF6 gene in 123 colorectal adenocarcinomas by performing PCR-SSCP sequencing. We found five somatic missense mutations: S155N, G163S, G163D, P183L and G195S. Three of them affected the activation domain of KLF6 and four mutations were predicted to disrupt the putative phosphorylation sites. On LOH analysis, 63 cases were heterozygous for at least one marker and 27 cases (42.9%) showed allelic loss at these markers. These data further support that the KLF6 gene may be one of the candidate tumor suppressor genes in colorectal cancers and that genetic alteration of the KLF6 gene might play a role in the development of colorectal carcinomas.
Subject(s)
Adenocarcinoma/genetics , Colorectal Neoplasms/genetics , Kruppel-Like Transcription Factors/genetics , Proto-Oncogene Proteins/genetics , DNA, Neoplasm/chemistry , DNA, Neoplasm/genetics , Humans , Kruppel-Like Factor 6 , Loss of Heterozygosity/genetics , Mutation, Missense , Polymerase Chain Reaction , Polymorphism, Single-Stranded ConformationalABSTRACT
KLF4 is an important regulator of cell proliferation and is maximally expressed in epithelial cells of the gastrointestinal tract. Inactivation of the KLF4 gene by genetic and epigenetic alterations has been reported in colorectal cancers, but the expression pattern of the KLF4 protein has not been studied. Here, to investigate the roles of KLF4 in colorectal carcinogenesis, we examined the expression pattern of the KLF4 protein in 123 colorectal cancers by immunohistochemistry using tissue microarray. Moderate to strong nuclear staining for KLF4 was found in normal colonic mucosa. Interestingly, loss of KLF4 expression was observed in 30 (24.4%) of 123 colorectal cancers. Statistically, loss of KLF4 protein expression was not associated with clinocopathologic parameters, including tumor stage (Bartholomew test, P>0.05), lymph node metastasis, differentiation, tumor location, and tumor size (chi2 test, P>0.05). These results indicate that loss of the KLF4 expression might play a role in tumor development as an early event for a subset of colorectal cancers.
Subject(s)
Adenocarcinoma/metabolism , Colorectal Neoplasms/metabolism , Kruppel-Like Transcription Factors/metabolism , Zinc Fingers , Adenocarcinoma/secondary , Biomarkers, Tumor/metabolism , Cell Nucleus/metabolism , Cell Nucleus/pathology , Colon/metabolism , Colon/pathology , Colorectal Neoplasms/pathology , Fluorescent Antibody Technique, Direct , Humans , Immunoenzyme Techniques , Intestinal Mucosa/metabolism , Intestinal Mucosa/pathology , Kruppel-Like Factor 4 , Tissue Array AnalysisABSTRACT
AIM: To investigate whether krUppel-like factor 6 (KLF6) plays an important role in the development and/or progression of colorectal cancer. METHODS: A total of 123 formalin-fixed and paraffin-embedded colorectal cancer specimens were analyzed by immunohistochemistry using tissue microarray for the expression of KLF6 protein. The specimens were collected over a 3-year period in the laboratories at our large teaching hospital in Seoul, Republic of Korea. The correlation of KLF6 expression with clinicopathologic parameters was analyzed by chi2 test and Bartholomew test. RESULTS: Normal colonic epithelium showed weak to moderate expression of KLF6, whereas reduced KLF 6 expression or loss of KLF6 expression was seen in 45 (36.6%) of the 123 colorectal carcinoma specimens. Interestingly, aberrant expression of KLF6 was detected in 25 (43.1%) of 58 cases with metastasis to regional lymph node and in 31 (47.0%) of 66 tumors more than 5 cm in size. Statistically, loss of KLF6 expression was significantly associated with tumor size (P < 0.05). However, there was no significant correlation between KLF6 expression and Dukes'stage (Bartholomew test, P > 0.05), tumor location and lymph node metastasis (chi2 test, P > 0.05). CONCLUSION: Loss of KLF6 expression may be a common and early event in colorectal carcinogenesis.
