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鉴定：分离转移潜能不同的亚系和克隆细胞系；小鼠乳腺肿瘤细胞系（MCH66P）经侵袭无关途径转移的66C8（非转移克隆）、66HM和Lu10（一般器官高转移亚系）等。一项使用这些细胞的比较研究表明，侵袭无关转移与高血管生成活性有关，特别是肿瘤血管的正弦发展。为了确定与这种转移有关的候选基因，我们使用抑制减法杂交（SSH）方法进行了鉴别筛选。在亚系和克隆细胞系高转移细胞中克隆出了多营养因子、分泌性白细胞蛋白酶抑制剂（SLPD）、S3B等差异表达基因。接下来我们将候选基因转染到66C8细胞中。在5个基因中，SLPI促进了肺的自发转移潜能，并诱导肿瘤血管的正弦发展，作为侵袭无关转移的指标。侵袭无关转移模型在人类癌症中的应用：利用10种常见人类癌症的档案标本进行组织学检查，表明在多种人类癌症中可能存在侵袭无关转移途径，特别是在大多数肾细胞癌、肝细胞癌和滤泡性甲状腺癌中。免疫组化研究表明，在小鼠模型中促进侵袭不依赖转移的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识别与癌症转移相关的新基因，并可能为改善人类癌症提供新的治疗策略。

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.