Development of anti-cancer reagent utilizing cytotoxic potential of human ribonucleases

胰腺型RNA酶被认为具有细胞毒性潜力，因为它们在进入细胞溶质时可以降解RNA分子。然而，这些RNA酶中的大多数几乎没有毒性，因为细胞对这些RNA酶没有主动摄取机制，并且因为普遍存在的细胞质RNA酶抑制剂被认为对RNA酶从细胞外的内吞泄漏起保护作用。为了研究RNase对靶向生长因子受体的恶性细胞的细胞毒性潜力，将人RNase 1的羧基端与人碱性成纤维细胞生长因子（bFGF）的氨基端融合。该RNase-FGF融合蛋白能有效地抑制小鼠黑色素瘤细胞系B 16/BL 6的生长，该细胞系具有高水平的FGF受体，其抑制作用可能是由于延长了整个细胞周期，而不是杀死细胞或阻滞细胞周期的某一特定阶段。因此，与细胞表面分子如FGF受体的配体融合的人RNA酶1显示为针对恶性细胞的选择性细胞靶向剂的有效候选物，对正常细胞类型具有低毒性作用。

Pancreatic-type RNases are considered to have cytotoxic potential, because they can degrade RNA molecules when enter the cytosol. However, most of these RNases are virtually little toxic because cells have no active uptake mechanism for these RNases and because ubiquitous cytoplasmic RNase inhibitor is considered to play protective role against endocytotic leak of RNases from outside of cells. To study the cytotoxic potential of RNase toward malignant cells targeting growth factor receptors, the carboxyl terminus of human RNase 1 was fused to the amino terminus of human basic fibroblast growth factor (bFGF). This RNase-FGF fused protein was found to effectively inhibited the growth of mouse melanoma cell line B 16/BL6 with the high level of cell surface FGF receptor.This effect appeared to result from prolongation of overall cell cycle rather than killing cells or specific arrest in a particular phase of cell cycle. Thus human RNase 1 fused to a ligand of cell surface molecules such as FGF receptor is shown to be an effective candidate for selective cell targeting agent toward malignant cells with low toxic effects on normal cell types.