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

胰型核糖核酸酶被认为具有潜在的细胞毒性，因为它们在进入胞浆时可以降解RNA分子。然而，大多数这些核糖核酸酶几乎没有毒性，因为细胞对这些核糖核酸酶没有主动摄取机制，而且普遍存在的细胞质核糖核酸酶抑制物被认为对细胞外的核糖核酸酶的内吞泄漏起到保护作用。为研究核糖核酸酶对肿瘤细胞靶向生长因子受体的杀伤作用，将人核糖核酸酶1的羧基末端与人碱性成纤维细胞生长因子的氨基末端融合。该融合蛋白能有效抑制小鼠黑色素瘤细胞株B16/BL6的生长，且细胞表面有较高水平的成纤维细胞生长因子受体，这种作用可能是由于延长了整个细胞周期，而不是杀伤细胞或在细胞周期的特定时相发生特异性停滞。因此，将人核糖核酸酶1与成纤维细胞生长因子受体等细胞表面分子的配体融合，是一种有效的靶向肿瘤细胞的药物，对正常细胞类型的毒性较低。

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.