Objective: To investigate the expression of four-jointed box kinase 1 (FJX1) in gastric cancer (GC), its correlation with survival outcomes of the patients, and its role in GC progression.
Methods: The expression level of FJX1 in GC tissues and normal gastric mucosal tissues and its correlation with the survival outcomes of GC patients were analyzed using TCGA and GEO database GC cohort. Immunohistochemistry was used to detect FJX1 expression level in clinical specimens of GC tissue, and its correlations with the patients' clinicopathological parameters and prognosis were analyzed. Bioinformatic analysis was performed to identify the potential pathways of FJX1 in GC. The effects of FJX1 overexpression or FJX1 silencing on GC cell proliferation and expressions of proliferation-related proteins, PI3K, AKT, p-PI3K, and p-AKT were evaluated using CCK-8 assay and Western blotting. The effect of FJX1 overexpression on GC cell tumorigenicity was evaluated in nude mice.
Results: GC tissues showed significantly higher expressions of FJX1 mRNA and protein compared with normal gastric mucosa tissues (P < 0.05). The high expression of FJX1 was associated with poor prognosis of GC patients (P < 0.05) and served as an independent risk factor for poor survival outcomes in GC (P < 0.05). FJX1 was expressed mainly in the cytoplasm of GC cells in positive correlation with Ki67 expression (R=0.34, P < 0.05), and was correlated with CA199 levels, depth of tumor infiltration and lymph node metastasis of GC (P < 0.05). In the cell experiment, FJX1 level was shown to regulate the expressions of Ki67 and PCNA and GC cell proliferation (P < 0.05). Gene set enrichment analysis indicated that the PI3K/AKT pathway potentially mediated the effect of FJX1, which regulated the expressions of PI3K and AKT and their phosphorylated proteins. In nude mice, FJX1 overexpression in GC cells significantly promoted the growth of the transplanted tumors (P < 0.05).
Conclusion: FJX1 is highly expressed in GC tissues and is correlated with poor prognosis of GC patients. FJX1 overexpression promotes GC cell proliferation through the PI3K/AKT signaling pathway, and may serve as a potential prognostic biomarker and therapeutic target for GC.
目的: 探讨四连接同源激酶1(FJX1)在胃癌(GC)中的表达以及与预后生存的关系，研究FJX1在胃癌进展中的作用及机制。
方法: 采用TCGA和GEO数据库胃癌队列分析FJX1在胃癌组织和正常胃黏膜组织中的表达情况，并分析FJX1表达与预后生存的相关性。通过免疫组化检测FJX1在胃癌组织中的蛋白表达水平，并分析FJX1蛋白表达与临床病理参数及预后的相关性。通过生物信息学探讨FJX1在胃癌中的潜在作用途径。采用慢病毒载体构建FJX1过表达和FJX1沉默的胃癌细胞株。采用免疫印记方法检测FJX1差异表达对增殖相关蛋白表达的影响，并采用CCK-8法检测FJX1对细胞增殖的影响。采用免疫印记方法检测FJX1差异表达细胞中PI3K和AKT的蛋白表达及磷酸化蛋白表达。采用裸鼠成瘤实验检测FJX1对肿瘤增殖的影响。
结果: 生物信息学分析及免疫组化结果显示，与正常胃黏膜组织相比，胃癌组织中的FJX1的mRNA和蛋白表达均显著增高(P < 0.05)。此外，FJX1的mRNA和蛋白水平高表达与胃癌患者不良预后相关(P < 0.05)，并且FJX1高表达是胃癌不良预后的独立危险因素(P < 0.05)。FJX1主要表达于胃癌细胞胞质，与Ki67表达呈正相关(R=0.34，P < 0.05)，并且FJX1表达水平与胃癌患者的CA199水平、肿瘤浸润深度(pT)和淋巴结转移(pN)相关(P < 0.05)。Western blot显示FJX1能促进增殖相关蛋白Ki67和PCNA的表达，CCK8实验结果证实FJX1能调控胃癌细胞增殖(P < 0.05)。基因集富集分析(GSEA)结果显示PI3K/AKT途径可能是FJX1的潜在分子作用机制，Western blot结果显示FJX1能促进PI3K和AKT磷酸化蛋白的表达。裸鼠移植瘤结果表明，FJX1能促进胃癌细胞在裸鼠体内的增殖(P < 0.05)。
结论: FJX1在胃癌组织中高表达并与胃癌不良预后相关，能够通过PI3K/AKT信号途径促进胃癌细胞的增殖，有潜力成为胃癌的预后生物标志物和治疗靶点。
Keywords: Gastric cancer; four-jointed box kinase 1; proliferation; survival prognosis.