Identification of molecules responsible for invasion-independent pathway of blood-borne metastasis.

小鼠转移模型的建立及转移相关基因的筛选：从小鼠乳腺癌细胞系(MCH66P)中分离出转移潜能不同的亚系和克隆性细胞系：66C8(非转移克隆)、66HM和Lu10(全身高转移亚系)等。使用这些细胞的对比研究表明，侵袭非侵袭性转移与高血管生成活性有关，特别是肿瘤血管的正弦发展。为了确定与这种类型的转移相关的候选基因，我们使用抑制性消减杂交(SSH)方法进行了差异筛选。在亚系和克隆细胞系中克隆了高转移细胞的差异表达基因Pleiotroin、分泌性白细胞蛋白酶抑制因子(SLPD)、S3B等。接下来，我们将候选基因导入66C8细胞。将侵袭非侵袭性转移模型应用于人类癌症：使用10种常见人类癌症的档案标本的组织学研究表明，在多种人类癌症中，尤其是在大多数肾细胞癌、肝细胞癌和滤泡性甲状腺癌中，侵袭性非侵袭性转移途径是可能的。免疫组织化学研究表明，在小鼠模型中促进非侵袭性转移的SLPI在真实细胞癌中也有高表达，基于这些结果的进一步研究可能使我们能够发现与癌症转移相关的新基因，并可能为人类癌症的改善提供新的治疗策略。

Establishment of mouse metastatic model and identification of metastasisl-related genes : We separated sublines and clonal cell lines different in metastatic potential ; 66C8 (a non-metastatic clone), 66HM and Lu10 (highly metastatic sublines to general organs), etc from a mouse mammary tumor cell line (MCH66P) metastasizing via an invasion-independent pathway. A comparative study using these cells demonstrated that invasion-independent metastasis is related to high angiogenesis activity, especially sinusoidal development of tumor vasculature. To identify candidate genes responsible for this type of metastasis we performed differential screening using suppressive subtractive hybridization (SSH) method. Pleiotrophin, Secretory leukocyte protease inhibitor (SLPD), S3B, etc. were cloned as differentially expressed genes in higher metastatic cells among the sublines and clonal cell lines. We next transfected the candidate genes in 66C8 cells. Of five genes SLPI promoted spontaneous metastatic potential to the lung and induced sinusoidal development of tumor vessels as an index of invasion-independent metastasis.Application of the invasion-independent metastasis model to human cancers : Histological examination using archival specimens of 10 common types of human cancers demonstrated that an invasion-independent metastatic pathway is possible in a wide variety of human cancers, especially in most cases of renal cell carcinomas, hepatocellular carcinomas and follicular thyroid carcinomas. Immunohistochemical study showed that SLPI, which promoted invasion-independent metastasis in the mouse model, was also highly expressed in real cell carcinoma.Further studies based on these results may enable us to identify novel genes related to cancer metastasis and may present new therapeutic strategies for the amelioration of human cancers.