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Galectin-3 is known to modulate cell proliferation and apoptosis and is highly expressed in human cancers, but its function in gastric cancer is still controversial. Here, we examined the role of galectin-3 in gastric cancer cells by silencing it with synthetic double-stranded siRNA. After silencing of galectin-3, cell numbers decreased and cell shape changed. Galectin-3 siRNA treatment also induced G 1 arrest. DNA microarray analysis was used to assess changes in gene expression following galectin-3 silencing. We found that silencing of galectin-3 caused changes in gene expression. RT-PCR and real-time PCR were utilized for validation of the changes found in microarray studies. Western blot analysis confirmed changes in the expression of proteins of interest: cyclin D1, survivin, XIAP, XAF, PUMA, and GADD45a. Generally, it tended to increase the expression of several pro-apoptotic genes, and to decrease the expression of cell cycle progressive genes. We also confirmed that changes in the expression of these genes were caused by galectin-3 overexpression. Finally, we demonstrated that silencing of galectin-3 enhanced apoptosis induction with chemotherapeutic agents by further reducing the expression of anti-apoptotic and ⁄ or cell survival molecules such as survivin, cyclin D1, and XIAP, and increasing the expression of pro-apoptotic XAF-1. We conclude that galectin-3 is involved in cancer progression and malignancy by modulating the expression of several relevant genes, and inhibition of galectin-3 may be an approach to improve chemotherapy of gastric cancers. (Cancer Sci 2010; 101: 94-102) G alectin-3 is a member of the carbohydrate-binding protein family, which are characterized by their affinity for b-galactosides.(1) It is the only chimera-type galectin, containing one CRD connected to an N-terminal proline-and glycine-rich domain. Galectin-3 is known to modulate a large number of cellular processes, especially inhibition of apoptosis and promotion of cell proliferation.(2,3) Galectin-3 contains an Asp-Trp-GlyArg (NWGR) motif in its C-terminal domain. The NWGR motif is also found in the BH-1 domain of Bcl-2 protein.(3) The NWGR motif in galectin-3 functions in the mitochondria, and exerts its anti-apoptotic activity by interacting with other apoptosis regulators and is thus crucial for its apoptotic function. Galectin-3 is also found in the nucleus as a nuclear matrix protein involved in pre-mRNA splicing, the Hedgehog or WNT signal-transduction pathway, mainly interacting with gemin4 and sufu.(4-7) These findings suggest that galectin-3 could be one of the essential factors for normal cell proliferation and ⁄ or development in the nucleus.In previous studies, a high level of cellular expression of galectin-3 was detected in many cancer types, including gastric cancer.(8-11) For example, knocked-down galectin-3 in human prostate cancer PC3 cells showed G 1 phase arrest, p21 upregulation, and hypophosphorylation of Rb, without influence on cyclin D1 or p27 protein expression levels.(12) Overexpressed gal...

Mutation of galectin-3 at position 191 (rs4644) substituting proline to histidine (gal-3H(64)) resulted in the acquisition of resistance to drug-induced apoptosis by breast cancer cells. This study employed gastric cancer cells and patient tissues in attempts to elucidate how and why this mutation in galectin-3 (gal-3H(64)) enhances cancer progression, compared to wild type galectin-3 (gal-3P(64)). First, we prepared lenti-virus constructs containing gal-3P(64), gal-3H(64) and LacZ, and used them to infect galectin-3 null SNU-638 cells. We found that gal-3H(64) over-expression increases gastric cancer cell growth more than gal-3P(64) or LacZ over-expression. Also, gal-3H(64) over-expression conferred more resistance to cisplatin or 5-FU induced cytotoxicity than gal-3P(64). Gal-3H(64) also enhanced nuclear accumulation of β-catenin as well as increased expression of TCF-4 target genes, such as fascin-1 and c-Myc through the augmented promoter binding activity of TCF-4, than gal-3P(64). We also demonstrated stronger staining of β-catenin and galectin-3 in malignant tissues from gastric cancer patients with mutated galectin-3 at position 191 (gal-3 191) (A/A) (H(64)) and greater localization in the nucleus than in gal-3 191 A/C (P(64)) cancer patients. Taken together, we elucidated in this study that germline variant of gal-3H(64) increases nuclear accumulation of β-catenin and promotes TCF transcriptional activity and enhances more the galectin-3's role in gastric cancer progression.