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Gene expression analysis of HPV-immortalized keratinocytes

ABSTRACT: To identify early processes in carcinogenesis, we used an in vitro model, based on the initiating event in cervical cancer, human papillomavirus (HPV) transformation of keratinocytes. We compared gene expression in primary keratinocytes (K) and HPV16-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. We revealed a contraction in expression of the apoptotic network during HF1 cell transformation, which affected the ability of L and BP cells to execute apoptosis, but did not lead to resistance to apoptotic stimuli. The contraction in the apoptotic machinery during the process of transformation was accompanied by a switch from apoptosis to necrosis in response to CDDP. The shrinkage of the pro- and anti-apoptotic networks appears to be part of a general contraction in the number of genes transcribed in L and BP cells. We also identified a large group of genes with induced expression, which are involved in cell metabolism and cell cycle, suggesting increased investment of the transformed cell in cellular proliferation. We hypothesize that the decrease in expression of many diverse pathways, including the pro- and anti-apoptotic networks, cuts the energy requirements for cell maintenance, allowing energy to be diverted towards rapid cell proliferation. This study supports the hypothesis that the process of cancer transformation may be accompanied by a shift from apoptosis to necrosis.

ORGANISM(S): Homo sapiens

PROVIDER: GSE15156 | GEO | 2009/04/22

SECONDARY ACCESSION(S): PRJNA114925

REPOSITORIES: GEO

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Project description:Our previous study implied a correlation of inhibitors of differentiation-1 (Id-1) to cervical cancer development. However, how Id-1 contributes to cervical carcinogenesis is unknown. In the present study, we investigated the role of Id-1 in transforming cervical cells with an in vitro transformation model. The human papillomavirus (HPV) immortalized cervical epithelial cells (H8) were successfully transformed by exposure to the carcinogen N-nitrosopyrrolidine (NPYR). The results showed that both Id-1 RNA and protein expression were significantly increased in transformed H8 cells, suggesting a possible role of Id-1 in cervical cell transformation. Ectopic expression of Id-1 in H8 cells potentiated NPYR-induced cell transformation. In contrast, silencing of Id-1 suppressed NPYR-induced H8 cell transformation. A cDNA microarray assay was performed, which identified suggested potential cell signaling pathways for NPYR-induced H8 cell transformation. The results suggest that Id-1 plays an oncogenic role in the cervix, which sheds light on cervical cancer development and implies potential target for cervical cancer prevention and therapy. Id-1-shRNA H8 and the control pGIPZ-H8 cells, with or without NPYR treatment, were used for cDNA microarray assay. Total RNA was extracted by using TRIZOL Reagent (Life Technologies, Carlsbad, CA, US) following the manufacturer's instructions. Total RNA was further purified by RNeasy micro kit (QIAGEN, GmBH, Germany) and RNase-free DNase Set (QIAGEN, GmBH, Germany). The RNAs were amplified, labeled and purified by using GeneChip 3' IVT Express Kit (Affymetrix, Santa Clara, CA, US) following the manufacturer's instructions. Array hybridization and wash were performed using GeneChipÂ® Hybridization, Wash and Stain Kit (Affymetrix, Santa Clara, CA, US) in a Hybridization Oven 645 (Affymetrix) and Fluidics Station 450 (Affymetrix) following the manufacturer's instructions. The slides were scanned with GeneChipÂ® Scanner 3000 (Affymetrix) using the Command Console Software 3.1 (Affymetrix) with default settings. Raw data were normalized by using the MAS 5.0 algorithm of GeneSpring Software 11.0 (Agilent Technologies, Santa Clara, CA, US).

Project description:Senescent cells secrete a plethora of factors with potent paracrine signaling capacity. Strikingly, senescence, which acts as a defense against cell transformation, exerts pro-tumorigenic activities through its secretome by promoting numerous tumor-specific features, such as cellular proliferation, epithelial-mesenchymal transition and invasiveness. Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) has the unique activity of activating cell death exclusively in tumor cells. Given that the senescence-associated secretome supports cell transformation, we asked whether factor(s) of this secretome would establish a program required for the acquisition of TRAIL sensitivity. We found that conditioned media from several types of senescent cells (CMS) efficiently sensitized pre-transformed cells to TRAIL, while the same was not observed with normal or immortalized cells. Dynamic transcription profiling analysis of CMS-exposed pre-transformed cells revealed paracrine autoregulatory loop of senescence-associated secretome factors and a dominant role of CMS-induced MYC. Sensitization to TRAIL coincided with MYC upregulation and massive changes in gene regulation. CMS-induced MYC silenced its target gene CFLAR, encoding the apoptosis inhibitor FLIPL, thus leading to the acquisition of TRAIL sensitivity. Altogether, our results reveal that senescent cell-secreted factors exert a TRAIL sensitizing effect on pre-transformed cells by modulating the expression of MYC and CFLAR. Notably, CMS dose-dependent sensitization to TRAIL was observed with TRAIL-insensitive cancer cells and confirmed in co-culture experiments. Dissection and characterization of TRAIL-sensitizing CMS factors and the associated signaling pathway(s) may provide a mechanistic insight in the acquisition of TRAIL sensitivity and lead to novel concepts for the apoptogenic therapy of pre-malignant and TRAIL-resistant tumors. Pre-transformed BJEL cells were incubated with CMS for 0, 1, 3, 6, 8, 16 or 24 h respectively. Total RNA has been extracted from each time point and used for gene expression analysis (Affymetrix Human Gene 1.0 ST Arrays).

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Gene expression analysis of HPV-immortalized keratinocytes

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