TY - JOUR
T1 - Genomic instability and telomerase activity in human bronchial epithelial cells during immortalization by human papillomavirus-16 E6 and E7 genes
AU - Coursen, Jill D.
AU - Bennett, William P.
AU - Gollahon, Lauren
AU - Shay, Jerry W.
AU - Harris, Curtis C.
N1 - Funding Information:
*Laboratory of Human Carcinogenesis, National Cancer Institute, National Institutes of Health, Bethesda, Maryland 20892-4255; and ²Department of Cell Biology and Neuroscience, UT Southwestern Medical Center, Dallas, Texas 75235-9039
PY - 1997/8/25
Y1 - 1997/8/25
N2 - Human papilloma virus types 16 and 18 contribute to the development of cervical carcinomas in which the E6 and E7 genes are frequently retained and expressed in the tumors. Our study explored the ability of the E6 and/or E7 genes to immortalize normal human bronchial epithelial (NHBE) cells and to reactivate telomerase expression in these cells. We have introduced the human papillomavirus type 16 E6 or E7 genes alone or in combination (E6/E7) into NHBE cells using the retroviral construct pLXSN. Cells expressing either the E6 or the E7 oncoproteins alone displayed an increased colony-forming efficiency and a slightly extended in vitro life span before entering a crisis, from which immortalized cell lines were not obtained. Telomerase activity was not detected in cells expressing either E6 or E7 individually. Cells expressing the E6/E7 oncoproteins in combination had a substantially increased life span before entering crisis. A subpopulation of these cells escaped from crisis and achieved 130 population doublings, suggesting immortalization. Telomerase activity was detected in these posterisis cells, but was not detected prior to crisis. In addition, karyotypic analysis showed evidence of genomic instability in mass cultures as well as clones expressing E6, E7, or E6/E7. Abnormalities included numerous monosomies and trisomies, chromatid gaps and breaks, double minutes, and aberrant chromosomes. These results demonstrate that expression of E6 and/or E7 is sufficient to induce genomic instability and an extended life span to NHBE cells, but the presence of both E6 and E7, along with at least one additional genetic or epigenetic event achieved during crisis, was required for reactivation of telomerase and the immortalization in this human cell type.
AB - Human papilloma virus types 16 and 18 contribute to the development of cervical carcinomas in which the E6 and E7 genes are frequently retained and expressed in the tumors. Our study explored the ability of the E6 and/or E7 genes to immortalize normal human bronchial epithelial (NHBE) cells and to reactivate telomerase expression in these cells. We have introduced the human papillomavirus type 16 E6 or E7 genes alone or in combination (E6/E7) into NHBE cells using the retroviral construct pLXSN. Cells expressing either the E6 or the E7 oncoproteins alone displayed an increased colony-forming efficiency and a slightly extended in vitro life span before entering a crisis, from which immortalized cell lines were not obtained. Telomerase activity was not detected in cells expressing either E6 or E7 individually. Cells expressing the E6/E7 oncoproteins in combination had a substantially increased life span before entering crisis. A subpopulation of these cells escaped from crisis and achieved 130 population doublings, suggesting immortalization. Telomerase activity was detected in these posterisis cells, but was not detected prior to crisis. In addition, karyotypic analysis showed evidence of genomic instability in mass cultures as well as clones expressing E6, E7, or E6/E7. Abnormalities included numerous monosomies and trisomies, chromatid gaps and breaks, double minutes, and aberrant chromosomes. These results demonstrate that expression of E6 and/or E7 is sufficient to induce genomic instability and an extended life span to NHBE cells, but the presence of both E6 and E7, along with at least one additional genetic or epigenetic event achieved during crisis, was required for reactivation of telomerase and the immortalization in this human cell type.
UR - http://www.scopus.com/inward/record.url?scp=0031586324&partnerID=8YFLogxK
U2 - 10.1006/excr.1997.3670
DO - 10.1006/excr.1997.3670
M3 - Article
C2 - 9281374
AN - SCOPUS:0031586324
SN - 0014-4827
VL - 235
SP - 245
EP - 253
JO - Experimental Cell Research
JF - Experimental Cell Research
IS - 1
ER -