Shift from Apoptotic to Necrotic Cell Death during Human Papillomavirus-induced Transformation of Keratinocytes

Oncogenic transformation is a complex, multistep process, which goes through several stages before complete malignant transformation occurs. To identify early processes in carcinogenesis, we used an in vitro model, based on the initiating event in cervical cancer, papillomavirus transformation of ke...

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Bibliographic Details
Published in:The Journal of biological chemistry 2009-04, Vol.284 (17), p.11717-11727
Main Authors: Kravchenko-Balasha, Nataly, Mizrachy-Schwartz, Sarit, Klein, Shoshana, Levitzki, Alexander
Format: Article
Language:English
Subjects:
Apoptosis
Benzo(a)pyrene
Cell Line, Tumor
Cell Proliferation
Cell Transformation, Neoplastic
Cells, Cultured
Female
HeLa Cells
Humans
Keratinocytes - metabolism
Keratinocytes - virology
Necrosis
Papillomaviridae - metabolism
Papillomavirus
Time Factors
Uterine Cervical Neoplasms - metabolism
Uterine Cervical Neoplasms - virology
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Summary:Oncogenic transformation is a complex, multistep process, which goes through several stages before complete malignant transformation occurs. To identify early processes in carcinogenesis, we used an in vitro model, based on the initiating event in cervical cancer, papillomavirus transformation of keratinocytes. We compared gene expression in primary keratinocytes (K) and papillomavirus-transformed keratinocytes from early (E) and late (L) passages and from benzo[a]pyrene-treated L cells (BP). The transformed cells exhibit similar transcriptional changes to clinical cervical carcinoma. The number of transcripts expressed progressively decreased during the evolution from K to BP cells. Bioinformatic analysis, validated by detailed biochemical analysis, revealed substantial contraction of both pro- and antiapoptotic networks during transformation. Nonetheless, L and BP cells were not resistant to apoptotic stimuli. At doses of cisplatin that led to 30-60% apoptosis of K and E cells, transformed L and BP cells underwent 80% necrotic cell death, which became the default response to genotoxic stress. Moreover, appreciable necrotic fractions were observed in the cervical carcinoma cell line, HeLa, in response to comparable doses of cisplatin. The shrinkage of biochemical networks, including the apoptotic network, may allow a cancer cell to economize on energy usage to facilitate enhanced proliferation but leaves it vulnerable to stress. This study supports the hypothesis that the process of cancer transformation may be accompanied by a shift from apoptosis to necrosis.
ISSN:0021-9258
1083-351X
DOI:10.1074/jbc.M900217200