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Galectin-7 is epigenetically-regulated tumor suppressor in gastric cancer.

Kim SJ, Hwang JA, Ro JY, Lee YS, Chun KH - Oncotarget (2013)

Bottom Line: Immunohistochemical staining using a tissue microarray of gastric cancer patients revealed significantly low expression levels of galectin-7 in malignant tissues compared with matched normal tissues, and decreased expression of galectin-7 in malignant tissues was associated with advanced TMN stage disease (p=0.034).More than 70% hypermethylation was observed in 7 of 9 gastric cancer cell lines tested and 5-aza-cytidine treatment lowered galectin-7 expression by reducing methylation in 24 cancer cell lines from five different organ origins.Further study of galectin-7 regulation may lead to improved gastric cancer diagnosis and therapy.

View Article: PubMed Central - PubMed

Affiliation: Department of Biochemistry and Molecular Biology, Yonsei University College of Medicine, 50 Yonsei-ro, Seodaemun-gu, Seoul, Republic of Korea.

ABSTRACT
Gastric cancer is the second leading cause of cancer death and remains a major clinical challenge due to poor prognosis and limited treatment options. Therefore, the basic mechanisms underlying gastric tumorigenesis deserve investigation. Although regulation of the galactoside-binding lectin galectin-7 in cancer has been studied, its role in tumor formation and progression remains controversial. In this study, we investigated galectin-7 expression and its role in gastric cancer. Immunohistochemical staining using a tissue microarray of gastric cancer patients revealed significantly low expression levels of galectin-7 in malignant tissues compared with matched normal tissues, and decreased expression of galectin-7 in malignant tissues was associated with advanced TMN stage disease (p=0.034). Importantly, low expression of galectin-7 in normal tissues was associated with a poor survival rate (p=0.0561). Over-expression of galectin-7 in AGS gastric adenocarcinoma cells suppressed cell proliferation, migration, and invasion, whereas ablation of galectin-7 in KATO III gastric carcinoma cells reversed these properties. AGS cells that overexpressed galectin-7 could not form gastric tumors in xenografted mice. More than 70% hypermethylation was observed in 7 of 9 gastric cancer cell lines tested and 5-aza-cytidine treatment lowered galectin-7 expression by reducing methylation in 24 cancer cell lines from five different organ origins. We analyzed CpG islands in the galectin-7 genomic region and detected hypermethylation at +1566bp of exon 2, the predicted p53 binding region. DNA hypermethylation of this region was also detected in gastric cancer tissues from 20 patients. Taken together, our data indicate that galectin-7 has a tumor suppressive function, and that the gene is epigenetically modified by DNA methylation and significantly down-regulated in gastric cancer. Further study of galectin-7 regulation may lead to improved gastric cancer diagnosis and therapy.

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Over-expression of Galectin-7 suppressed proliferation, migration, and invasion of AGS gastric cancer cells(A) mRNA and protein expression of galectin-7 in nine gastric cancer cell lines by RT-PCR and western blot. GAPDH and β-actin were used as loading controls. (B-E) AGS cells were transfected with pQE control vector and pQE-galectin-7 expression vector for 48 h. (B) Western blot analysis of galectin-7 protein expression and crystal violet staining of cells, (C) Cell proliferation measured by WST assay, (D) Cell migration assay, (E) Cell invasion assay. For cell migration and invasion assays the p value (* p<0.0001 vs. scRNA) was calculated using Student's t-test.
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Figure 2: Over-expression of Galectin-7 suppressed proliferation, migration, and invasion of AGS gastric cancer cells(A) mRNA and protein expression of galectin-7 in nine gastric cancer cell lines by RT-PCR and western blot. GAPDH and β-actin were used as loading controls. (B-E) AGS cells were transfected with pQE control vector and pQE-galectin-7 expression vector for 48 h. (B) Western blot analysis of galectin-7 protein expression and crystal violet staining of cells, (C) Cell proliferation measured by WST assay, (D) Cell migration assay, (E) Cell invasion assay. For cell migration and invasion assays the p value (* p<0.0001 vs. scRNA) was calculated using Student's t-test.

Mentions: We next investigated the role of galectin-7 in the progression in gastric cancer cells. First, we examined the expression levels of galectin-7 mRNA and protein in nine gastric cancer cell lines (Figure 2A). KATO III and SNU-16 cell lines showed high expression of galectin-7 whereas the other cell lines expressed low levels of galectin-7. We selected AGS gastric cancer cells with low expression of Galectin-7 and transiently transfected them with the expression vector pQE-9-galectin-7 for 48 h. Over-expression of galectin-7 was confirmed by western blotting (Figure 2B). Galectin-7 over-expression inhibited cell proliferation as measured by crystal violet staining (Figure 2B) and WST assay (Figure 2C), and significantly decreased gastric cancer cell migration and invasion, (Figure 2D and E). These findings suggest that galectin-7 functions as a tumor suppressor in gastric cancer.


Galectin-7 is epigenetically-regulated tumor suppressor in gastric cancer.

Kim SJ, Hwang JA, Ro JY, Lee YS, Chun KH - Oncotarget (2013)

Over-expression of Galectin-7 suppressed proliferation, migration, and invasion of AGS gastric cancer cells(A) mRNA and protein expression of galectin-7 in nine gastric cancer cell lines by RT-PCR and western blot. GAPDH and β-actin were used as loading controls. (B-E) AGS cells were transfected with pQE control vector and pQE-galectin-7 expression vector for 48 h. (B) Western blot analysis of galectin-7 protein expression and crystal violet staining of cells, (C) Cell proliferation measured by WST assay, (D) Cell migration assay, (E) Cell invasion assay. For cell migration and invasion assays the p value (* p<0.0001 vs. scRNA) was calculated using Student's t-test.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3824540&req=5

Figure 2: Over-expression of Galectin-7 suppressed proliferation, migration, and invasion of AGS gastric cancer cells(A) mRNA and protein expression of galectin-7 in nine gastric cancer cell lines by RT-PCR and western blot. GAPDH and β-actin were used as loading controls. (B-E) AGS cells were transfected with pQE control vector and pQE-galectin-7 expression vector for 48 h. (B) Western blot analysis of galectin-7 protein expression and crystal violet staining of cells, (C) Cell proliferation measured by WST assay, (D) Cell migration assay, (E) Cell invasion assay. For cell migration and invasion assays the p value (* p<0.0001 vs. scRNA) was calculated using Student's t-test.
Mentions: We next investigated the role of galectin-7 in the progression in gastric cancer cells. First, we examined the expression levels of galectin-7 mRNA and protein in nine gastric cancer cell lines (Figure 2A). KATO III and SNU-16 cell lines showed high expression of galectin-7 whereas the other cell lines expressed low levels of galectin-7. We selected AGS gastric cancer cells with low expression of Galectin-7 and transiently transfected them with the expression vector pQE-9-galectin-7 for 48 h. Over-expression of galectin-7 was confirmed by western blotting (Figure 2B). Galectin-7 over-expression inhibited cell proliferation as measured by crystal violet staining (Figure 2B) and WST assay (Figure 2C), and significantly decreased gastric cancer cell migration and invasion, (Figure 2D and E). These findings suggest that galectin-7 functions as a tumor suppressor in gastric cancer.

Bottom Line: Immunohistochemical staining using a tissue microarray of gastric cancer patients revealed significantly low expression levels of galectin-7 in malignant tissues compared with matched normal tissues, and decreased expression of galectin-7 in malignant tissues was associated with advanced TMN stage disease (p=0.034).More than 70% hypermethylation was observed in 7 of 9 gastric cancer cell lines tested and 5-aza-cytidine treatment lowered galectin-7 expression by reducing methylation in 24 cancer cell lines from five different organ origins.Further study of galectin-7 regulation may lead to improved gastric cancer diagnosis and therapy.

View Article: PubMed Central - PubMed

Affiliation: Department of Biochemistry and Molecular Biology, Yonsei University College of Medicine, 50 Yonsei-ro, Seodaemun-gu, Seoul, Republic of Korea.

ABSTRACT
Gastric cancer is the second leading cause of cancer death and remains a major clinical challenge due to poor prognosis and limited treatment options. Therefore, the basic mechanisms underlying gastric tumorigenesis deserve investigation. Although regulation of the galactoside-binding lectin galectin-7 in cancer has been studied, its role in tumor formation and progression remains controversial. In this study, we investigated galectin-7 expression and its role in gastric cancer. Immunohistochemical staining using a tissue microarray of gastric cancer patients revealed significantly low expression levels of galectin-7 in malignant tissues compared with matched normal tissues, and decreased expression of galectin-7 in malignant tissues was associated with advanced TMN stage disease (p=0.034). Importantly, low expression of galectin-7 in normal tissues was associated with a poor survival rate (p=0.0561). Over-expression of galectin-7 in AGS gastric adenocarcinoma cells suppressed cell proliferation, migration, and invasion, whereas ablation of galectin-7 in KATO III gastric carcinoma cells reversed these properties. AGS cells that overexpressed galectin-7 could not form gastric tumors in xenografted mice. More than 70% hypermethylation was observed in 7 of 9 gastric cancer cell lines tested and 5-aza-cytidine treatment lowered galectin-7 expression by reducing methylation in 24 cancer cell lines from five different organ origins. We analyzed CpG islands in the galectin-7 genomic region and detected hypermethylation at +1566bp of exon 2, the predicted p53 binding region. DNA hypermethylation of this region was also detected in gastric cancer tissues from 20 patients. Taken together, our data indicate that galectin-7 has a tumor suppressive function, and that the gene is epigenetically modified by DNA methylation and significantly down-regulated in gastric cancer. Further study of galectin-7 regulation may lead to improved gastric cancer diagnosis and therapy.

Show MeSH
Related in: MedlinePlus