Molecular cloning of cervical cancer tumor suppressor gene

虽然宫颈癌是由某些类型的人乳头瘤病毒（HPV）如16型和18型感染引起的，但这些HPV的E6 E7癌基因的表达不足以致癌。除此之外，一些肿瘤抑制基因的失活可能是必不可少的。本研究的目的是分离与宫颈癌发生有关的抑癌基因，我们利用人正常成纤维细胞cDNA文库，通过表达克隆的方法，从宫颈癌细胞系（CGL 4）中分离到一个影响肿瘤发生的基因，并获得了一个候选抑癌基因AF 337。该基因在导入时抑制了致瘤性CGL 4细胞的生长，即AF 337表达载体产生的耐药克隆数比对照载体少，并且除了一个克隆（克隆5）外，几乎（23/24）出现了不保留或不表达cDNA的克隆。AF 337 mRNA大小约为2.3kb，在所有组织中均有表达。该基因的表达在一些癌细胞系中减少。预测的基因产物由373个氨基酸组成，具有高酸性区域、富含脯氨酸的结构域和亮氨酸拉链基序，表明AF 337可能是一个转录因子。该基因与其他已知功能的基因没有明显的序列同源性。

Although cervical carcinoma is caused by infection with certain types of human papillomavirus (HPV) such as types 16 and 18, expression of the E6E7 oncogenes of these HPV is not sufficient for the carcinogenesis. In addition to it, inactivation of some tumor suppressor gene (s) may be indispensable. The objective of this research is to isolate tumor suppressor genes involved in cervical carcinogenesis.We attempted to isolate a gene (s) affecting tumorigenesity of cervical carcinoma-derived cell line (CGL4) by expression cloning using cDNA library prepared from normal human fibroblasts, and obtained a candidate tumor suppressor gene AF337. This gene suppressed growth of tumorigenic CGL4 cells when introduced, that is, AF337 expression vector gave smaller number of drug resistant colonies than control vectors, and almost (23/24), except one (clone 5), colonies appeared did not retain or express the cDNA.The clone 5 formed tumors in nude mice, but the 2 of 3 tumors formed lost the cDNA.The AF337 mRNA was about 2.3kb in size and was expressed in all tissues examined. Expression of this gene was reduced in some cancer cell lines. The predicted gene product was composed of 373 amino acids and possessed highly acidic region, proline-rich domain, and leucine-zipper motif, suggesting that AF337 may be a transcription factor. This gene had no apparent sequence homology with other genes of known function.