title: S100A6 protein negatively regulates CacyBP/SIP-mediated inhibition of gastric cancer cell proliferation and tumorigenesis.
abstract: Calcyclin-binding protein (CacyBP/SIP), identified on the basis of its ability to interact with S100 proteins in a calcium-dependent manner, was previously found to inhibit the proliferation and tumorigenesis of gastric cancer cells in our laboratory. Importantly, the effects of S100 proteins on the biological behavior of CacyBP/SIP in gastric cancer remain unclear. Herein, we report the construction of eukaryotic expression vectors for wild-type CacyBP/SIP and a truncated mutant lacking the S100 protein binding domain (CacyBP/SIPΔS100). The expressions of the wild-type and truncated recombinant proteins were demonstrated by transfection of MKN45 gastric cancer cells. Co-immunoprecipitation assays demonstrated interaction between S100A6 and wild-type CacyBP/SIP in MKN45 cells. Removal of the S100 protein binding domain dramatically reduced the affinity of CacyBP/SIP for S100 proteins as indicated by reduced co-immunoprecipitation of S100A6 by CacyBP/SIPΔS100. The MTT assay, FACS assay, clonogenic assay and tumor xenograft experiment were performed to assess the effect of CacyBP/SIP on cell growth and tumorigenesis in vitro and in vivo. Overexpression of CacyBP/SIP inhibited the proliferation and tumorigenesis of MKN45 gastric cancer cells; the proliferation and tumorigenesis rates were even further reduced by the expression of CacyBP/SIPΔS100. We also showed that S100 proteins negatively regulate CacyBP/SIP-mediated inhibition of gastric cancer cell proliferation, through an effect on β-catenin protein expression and transcriptional activation of Tcf/LEF. Although the underlying mechanism of action requires further investigation, this study provides new insight into the interaction between S100 proteins and CacyBP/SIP, which might enrich our knowledge of S100 proteins and be helpful for our understanding of the development of gastric cancer.
authors.affiliation: Department of Geriatrics, Xijing Hospital, Fourth Military Medical University, Xi'an, Shaanxi, China. ningxx01@sohu.com
authors.forename: Xiaoxuan
authors.initials: X
authors.lastname: Ning
authors.forename: Shiren
authors.initials: S
authors.lastname: Sun
authors.forename: Kun
authors.initials: K
authors.lastname: Zhang
authors.forename: Jie
authors.initials: J
authors.lastname: Liang
authors.forename: Yucai
authors.initials: Y
authors.lastname: Chuai
authors.forename: Yuan
authors.initials: Y
authors.lastname: Li
authors.forename: Xiaoming
authors.initials: X
authors.lastname: Wang
mesh_terms: D000818:Animals; D002135:Calcium-Binding Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D018797:Cell Cycle Proteins / Q000378:metabolism*; D045744:Cell Line, Tumor; D049109:Cell Proliferation; D015972:Gene Expression Regulation, Neoplastic; D005822:Genetic Vectors / Q000235:genetics; D006801:Humans; D051379:Mice; D017434:Protein Structure, Tertiary; D059748:Proteolysis; D000075383:S100 Calcium Binding Protein A6; D009418:S100 Proteins / Q000378:metabolism*; D017384:Sequence Deletion; D013274:Stomach Neoplasms / Q000473:pathology*; D051176:beta Catenin / Q000378:metabolism
chemical_list: C491778:CACYBP protein, human; D002135:Calcium-Binding Proteins; D018797:Cell Cycle Proteins; D000075383:S100 Calcium Binding Protein A6; D009418:S100 Proteins; D051176:beta Catenin; C055351:S100A6 protein, human