title: Sineoculis homeobox homolog 1 protein as an independent biomarker for gastric adenocarcinoma.
abstract: Sine oculis homeobox homolog 1 (SIX1) protein is a member of the homeobox transcription factor family. Overexpression of SIX1 contributes to cancer progression and is associated with adverse outcomes in various cancer types including breast, ovarian, uterine cervical and liver. To investigate the clinicopathological significance of SIX1 protein expression in gastric adenocarcinomas (GAC), localization of the SIX1 protein was determined in MKN-1, a gastric cancer cell line, using immunofluorescence (IF) staining; SIX1 mRNA level was detected in fresh tissues of GAC and normal gastric mucosa using quantitative real-time polymerase chain reaction (qRT-PCR); and SIX1 protein expression was assessed in 163 GAC, 35 gastric dysplasia and 26 normal gastric mucosa using immunohistochemical (IHC) staining. Correlations between SIX1 protein expression and pathological parameters of GAC were analyzed using Chi-square tests, differences in survival curves were analyzed using log-rank tests, and multivariate survival analysis was performed using the Cox proportional hazards regression model. SIX1 protein showed a mainly cytoplasmic staining pattern in GAC using IF and IHC staining. The positive SIX1 protein expression rate was 80.4% in GAC, which was significantly higher than in either gastric dysplasia (45.7%) or normal gastric mucosa (26.9%) (P<0.01). qRT-PCR data also confirmed increased levels of SIX1 mRNA expression in GAC compared with the normal gastric mucosa in fresh tissues. In addition, the strongly positive SIX1 protein expression rate was significantly correlated with clinical stage, lymph node metastasis and serosal invasion of GAC (P<0.01 or P<0.05), while there was no association with gender, age, tumor size, Lauren classification or histological types of GAC. Notably, strongly positive signals were frequently observed in tumor blood vessels and/or lymphatic vessels. GAC patients with high expression of the SIX1 had shorter overall and disease-free survival rates than those with low SIX1 protein expression (P<0.01). Furthermore, using multivariate analysis, SIX1 protein expression was found to be an independent risk factor for survival in patients with GAC along with clinical stage and serosal invasion (P<0.01). In conclusion, SIX1 protein expression status may be an independent biomarker for prognostic evaluation of GAC.
authors.affiliation: Key Laboratory of Natural Resources of Changbai Mountain & Functional Molecules, Yanbian University, Ministry of Education, Yanji 133002, China; Department of Pathology, Yanbian University Medical College, Yanji 133002, China. Electronic address: 839009337@qq.com.
authors.forename: Huixin
authors.initials: H
authors.lastname: Lv
authors.affiliation: Department of Dermatology, Yanbian University Hospital, Yanji 133000, China. Electronic address: 13843397695@163.com.
authors.forename: Aili
authors.initials: A
authors.lastname: Cui
authors.affiliation: Department of Pathology, Yanbian University Medical College, Yanji 133002, China. Electronic address: fdsun@ybu.edu.cn.
authors.forename: Fengdan
authors.initials: F
authors.lastname: Sun
authors.affiliation: Department of Pathology, Yanbian University Medical College, Yanji 133002, China. Electronic address: 403060029@qq.com.
authors.forename: Yuan
authors.initials: Y
authors.lastname: Zhang
authors.affiliation: Department of Pathology, Luhe Teaching Hospital of the Capital Medical University, Beijing 101100, China. Electronic address: liyan_20040108@163.com.
authors.forename: Yan
authors.initials: Y
authors.lastname: Li
authors.affiliation: Department of Dermatology, Yanbian University Hospital, Yanji 133000, China. Electronic address: 15526770635@163.com.
authors.forename: Lianhua
authors.initials: L
authors.lastname: Li
authors.affiliation: Key Laboratory of Natural Resources of Changbai Mountain & Functional Molecules, Yanbian University, Ministry of Education, Yanji 133002, China; Department of Pathology, Yanbian University Medical College, Yanji 133002, China. Electronic address: zhlin720@ybu.edu.cn.
authors.forename: Zhenhua
authors.initials: Z
authors.lastname: Lin
mesh_terms: D000230:Adenocarcinoma / Q000235:genetics* / Q000378:metabolism* / Q000401:mortality; D000328:Adult; D000368:Aged; D014408:Biomarkers, Tumor / Q000032:analysis* / Q000235:genetics / Q000378:metabolism; D045744:Cell Line, Tumor; D005260:Female; D005455:Fluorescent Antibody Technique; D005753:Gastric Mucosa / Q000378:metabolism / Q000473:pathology; D015972:Gene Expression Regulation, Neoplastic; D018398:Homeodomain Proteins / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D007150:Immunohistochemistry; D008297:Male; D008875:Middle Aged; D011379:Prognosis; D016016:Proportional Hazards Models; D012016:Reference Values; D013274:Stomach Neoplasms / Q000235:genetics / Q000378:metabolism* / Q000401:mortality
chemical_list: D014408:Biomarkers, Tumor; D018398:Homeodomain Proteins; C099236:SIX1 protein, human
keywords: Gastric cancer; Prognosis; SIX1; Survival analysis