Application of midkine to diagnosis and treatment of tumors and growth of blood stem cells.

用酶联免疫法测定血清中期因子水平的大规模调查显示，80%以上的癌症患者血清中期因子水平高于正常人。中期因子水平可用作肿瘤标志物。进一步证实了midkinemRNA截短后的肿瘤特异性，所有淋巴结转移病例均有midkinemRNA截短后的表达，因此，用PCR方法检测midkinemRNA截短后的表达可作为手术后微转移的标志物。14例食管癌组织中有8例中期因子表达，而正常食管组织中均无中期因子表达。中期因子基因上游2.3kb的5区含有一个启动子序列，它能使下游基因在食管癌细胞中表达。将胸苷激酶基因置于启动子下并转染癌细胞，导致对更昔洛韦的敏感性增加。因此，提出了使用MK启动子的癌症治疗策略。中期因子在骨折部位表达。中期因子cDNA的导入和过表达诱导前软骨细胞的分化。中期因子可用于骨折的治疗。中期因子缺陷型小鼠对顺铂的肾毒性更敏感。中期因子可用于降低抗癌药物的毒性。中期因子促进巨噬细胞以及中性粒细胞的迁移。在中期因子缺陷小鼠中，球囊损伤模型未发生巨噬细胞迁移和新生内膜形成。这一发现表明，中期因子促进炎症细胞的迁移，并有助于形成病理状态。

Large scale survey of serum midkine levels determined by enzyme-linked immunoassay revealed that in more than 80% cases of cancer patients, the serum midkine levels increased as compared to that of normal human subjects. Midkine levels may be used as a tumor marker. Tumor specificity of truncated midkine mRNA was further confirmed, and all cases of lymph node metastasis had truncated midkine mRNA.Thus, the truncated mRNA can be a marker to detect minor metastasis upon surgical operation by using PCR.We also found that midkine mRNA expression was increased in adenoma before development of colon carcinoma. Midkine was expressed in 8 cases among 14 cases of esophageal carcinoma, but not in the normal tissues. The 2.3 kb 5 upstream region of midkine gene contains a promoter sequence, which enabled expression of downstream genes in esophageal carcinoma cells. Thymidine kinase gene was placed under the promoter and transfected to the carcinoma cells, resulting in increased sensitivity to ganciclovir. Thus, a strategy of cancer therapy was proposed using the MK promoter. Midkine was expressed at the site of bone fracture. Introduction of midkine cDNA and overexpression induced differentiation of prechondrocytes. Midkine may be applied to cure of bone fracture. Midkine deficient mice were more susceptible to renal toxicity of cisplatin. Midkine may be useful in reducing toxicity of anti-cancer drugs. Midkine promoted migration of macrophages as well as neutrophils. In midkine deficient mice, macrophage migration and neointima formation did not occur upon balloon injury model. This finding implicated that midkine promoted migration of inflammatory cells and contributed to formation of pathological status.