Structures and functions of growth inhibitors secreted from rat liver cell lines

我们一直在研究各种血清、组织和培养细胞中存在的生长抑制物质，使用大鼠肝源性上皮细胞系BRL及其致瘤性转化RSV-BRL。前期研究发现，目的细胞系自身分泌生长抑制剂，并对BRL条件培养基中发现的3种生长抑制剂（M_r 56k、21k和<10k）进行了纯化和鉴定。在这项研究中，我们试图表征RSV-BRL分泌的生长抑制剂。RSV-BRL至少分泌两种生长抑制剂：一种（Gl-1）对酸和热稳定，但对还原性试剂不稳定；另一种（Gl-2）对酸和热稳定，但对还原性试剂不稳定。Gl-1作为M_r 300-700k的潜伏复合物分泌到培养基中，当酸处理复合物时，至少有两种活性抑制剂pl 9.2和pl 7.9从复合物中解离。用pl 9.2对Gl-1的n端氨基酸序列进行分析，发现它与tgf - β -1相同。从条件培养基中部分纯化出Gl-2。估计Gl-2的M_r为10-40k。与RSV-BRL相比，gl - 1和Gl-2对BRL生长的抑制作用更强。除了这些生长抑制剂外，我们还从兔血清中高度纯化了一种含有M_r 60-70k的新型生长抑制剂，该抑制剂选择性地抑制肿瘤或恶性转化细胞的生长。

We have been studying growth-inhibitory substances present in various sera, tissues and cultured cells using a rat liver-derived epithelial cell line BRL and its tumorigenic transformant RSV-BRL. Previous studies revealed that the target cell lines themselves secreted growth inhibitors, and three kinds of growth inhibitors (M_r 56k, 21k and <10k) found in the conditioned medium of BRL were purified and characterized. In this study, we attempted to characterize growth inhibitors secreted from RSV-BRL.RSV-BRL secreted at least two kinds of growth inhibitors: one (Gl-1) was stable against acid and heat but not reducing reagents, whereas the other (Gl-2) was stable against acid and heat but labile against reducing reagents. Gl-1 was secreted as a latent complex with M_r 300-700k into the culture medium, and at least two active inhibitors with pl 9.2 and pl 7.9 were dissociated from the complex when the complex was treated with acid. Analysis of the N-terminal amino acid sequence of Gl-1 with pl 9.2 revealed that it was identical to TGF-beta1. Gl-2 was partially purified from the conditioned medium. The M_r of Gl-2 was estimated to be 10-40k. Both Gl-I and Gl-2 much more potently inhibited the growth of BRL than RSV-BRL. In addition to these growth inhibitors, we highly purified a novel growth inhibitor with M_r 60-70k from rabbit serum, which selectively inhibited the growth of tumorous or malignantly transformed cells.