Bosch F X, Schwarz E, Boukamp P, Fusenig N E, Bartsch D, zur Hausen H
Institut für Zell- und Tumorbiologie, Deutsches Krebsforschungszentrum, Heidelberg, Federal Republic of Germany.
J Virol. 1990 Oct;64(10):4743-54. doi: 10.1128/JVI.64.10.4743-4754.1990.
The E6 and E7 genes of the cancer-associated human papillomavirus (HPV) types 16 (HPV16) and 18 (HPV18) can induce cell immortalization in vitro in normal human keratinocytes. This, however, is not associated with tumorigenicity in vivo. On the other hand, tumorigenicity of HPV18-positive HeLa cervical carcinoma cells can be suppressed by fusion of HeLa cells with normal human keratinocytes or fibroblasts. We have addressed the question of whether suppression of tumorigenicity in HeLa x fibroblast hybrid cells might be due to a reduced ability of these cells to express the HPV18 E6-E7 genes in vivo. Nontumorigenic hybrid cells and tumorigenic hybrid segregants were transplanted as organotypical cultures or injected subcutaneously into immunocompromised mice and were analyzed for HPV18 E6-E7 gene expression by RNA-RNA in situ hybridization. The tumorigenic hybrid cells showed a continuous and invasive growth that was associated with high levels of HPV18 E6-E7 mRNAs at all time points examined. In contrast, the nontumorigenic hybrid cells stopped cell proliferation approximately 3 days after transplantation. At this time they expressed the E6-E7 genes at low levels, whereas at day 2 high expression levels were observed. However, the mRNA levels of the cytoskeletal genes beta-actin and vimentin remained high for at least 14 days, demonstrating that inhibition of growth and of HPV18 E6-E7 gene expression was not due to cell death. These results suggest that growth inhibition of the nontumorigenic HeLa x fibroblast hybrid cells in vivo might be caused by suppression of HPV18 E6-E7 gene expression and are compatible with the idea of an intracellular surveillance mechanism for HPV gene expression existing in nontumorigenic cells.
与癌症相关的人乳头瘤病毒16型（HPV16）和18型（HPV18）的E6和E7基因可在体外诱导正常人角质形成细胞永生化。然而，这与体内致瘤性无关。另一方面，HPV18阳性的HeLa宫颈癌细胞与正常人角质形成细胞或成纤维细胞融合后，其致瘤性可被抑制。我们探讨了HeLa×成纤维细胞杂交细胞致瘤性的抑制是否可能是由于这些细胞在体内表达HPV18 E6 - E7基因的能力降低所致。将无致瘤性的杂交细胞和有致瘤性的杂交分离株作为器官型培养物移植或皮下注射到免疫受损小鼠体内，并通过RNA - RNA原位杂交分析HPV18 E6 - E7基因表达。有致瘤性的杂交细胞呈现持续侵袭性生长，在所有检测时间点均与高水平的HPV18 E6 - E7 mRNA相关。相比之下，无致瘤性的杂交细胞在移植后约3天停止细胞增殖。此时它们低水平表达E6 - E7基因，而在第2天观察到高表达水平。然而，细胞骨架基因β - 肌动蛋白和波形蛋白的mRNA水平至少14天保持较高，表明生长抑制和HPV18 E6 - E7基因表达抑制并非由于细胞死亡。这些结果表明，无致瘤性的HeLa×成纤维细胞杂交细胞在体内的生长抑制可能是由HPV18 E6 - E7基因表达的抑制引起的，并且与无致瘤性细胞中存在HPV基因表达的细胞内监测机制的观点相符。
