Molecular and biological analysis of the mechanisms of impaired wound healing in gastrointestinal tract.-The role of fibroblast growth factor receptor 3-IIIb.

本研究的最初目的是分析成纤维细胞生长因子受体3-IIIb（FGFR 3-IIIb）在胃肠道正常或受损伤口愈合过程中的功能作用，该受体已被证明由结肠上皮细胞特异性表达，发现该受体对上皮伤口愈合的贡献不显著。我们还研究了FGFR 3基因表达和剪接变异的变化是否与人胃肠道癌的恶性进展相关。首先，我们通过RT-PCR检测了人食管癌、胃癌和结直肠癌患者中FGFR 3亚型的基因表达。FGFR 3具有三种可变剪接的同种型。FGFR 3-IIIb和FGFR 3-ILIc是跨膜型同种型，具有不同的配体特异性。第三种同种型FGFR 3 ΔTM是缺乏跨膜结构域的可溶性同种型，并分泌到细胞外。FGFR 3-IIIc在食管癌组织中的表达率明显高于正常人食管活检组织。相反，与来自相同患者的正常组织相比，FGFR 3-IIIb和FGFR 3 ΔTM在结直肠癌中显著增加。接下来，我们研究了FGFR 3-IIIc在上皮癌细胞中的重要性。我们发现，蜕皮激素诱导的FGFR 3-IIIc在人鳞状细胞癌DJM 1细胞中的表达极大地增强了对FGF 2的响应的锚定依赖性和非依赖性生长以及伤口愈合。因此，FGFR 3c具有促进上皮癌恶性进展的潜力。虽然FGFR 3 ΔΔTM的生理意义尚未确定，但我们的研究结果表明，FGFR 3-IIIc与FGFR 3-IIIb和FGFR 3 ΔATM的表达增加可能是恶性肿瘤的重要标志物和胃肠道癌症的潜在抗癌治疗靶点。

The initial purpose of the study was to analyze the functional role of Fibroblast Growth Factor Receptor 3-IlIb (FGFR3-IIIb), which has been shown to be expressed specifically by colonic epithelial cells, in the process of normal or impaired wound healing of gastrointestinal tract and found that the contribution of the receptor to epithelial wound healing was not significant. We alternatively investigate whether a change in the gene expression and splice variations of FGFR3 is associated with malignant progression in human gastrointestinal cancers. First, we examined the gene expression of FGFR3 isoforms in human esophageal, gastric, and colorectal cancer patients by RT-PCR. FGFR3 has three alternatively spliced isoforms. FGFR3-IIIb and FGFR3-ILIc are the transmembrane -type isoforms and have different ligand specificities. The third isoform, FGFR3ΔTM, is the soluble isoform lacking the transmembrane domain and secreted extracellularly. The incidence of FGFR3-IIIc in the esophageal carcinoma was significantly higher than in the normal human esophageal biopsies. In contrast, FGFR3-IIIb and FGFR3ΔTM were significantly increased in the colorectal carcinomas compared to the normal tissue from the same patients. Next, we investigated the importance of FGFR3-IIIc in epithelial cancer cells. We showed that the ecdysone-inducible expression of FGFR3-IIIc in human squamous cell carcinoma DJM1 cells greatly enhanced anchorage-dependent and -independent growth, and wound healing in response to FGF2. Thus, FGFR3c has the potential to enhance malignant progression in epithelial cancers. Although the physiological significance of FGFR3ΔΔTM has not yet been defined, our findings suggest that the increased expression of FGFR3-IIIc together with FGFR3-IIIb and FGFR3ΔATM may be important markers for malignancy and potential anti-cancer therapeutic targets in gastrointestinal cancers.