Growth arrest of HPV-positive cells after histone deacetylase inhibition is independent of E6/E7 oncogene expression.
Inhibitors of histone deacetylase (HDAC) are capable of arresting growth in cervical carcinoma cells in the G1 phase of the cell cycle. Although HPV E6/E7 mRNA steady-state levels appeared to be constant after prolonged treatment, time-course experiments revealed that viral transcription was transiently down-regulated between 7-10 h prior to cdk2 suppression. To test whether transitory suppression was a prerequisite for the biological outcome after HDAC inhibition, we took advantage of two immortalized human keratinocyte cell lines in which E6/E7 oncogene expression was controlled by different regulatory regions. After treatment with sodium butyrate (NaB) or trichostatin A (TSA), HPV16 upstream regulatory region (URR)-directed transcription was down-regulated, showing kinetics similar to those in cervical carcinoma cells. In contrast, beta-actin promoter controlled E6/E7 transcription was even temporarily increased and finally declined to levels initially detected in the untreated controls. Both cell lines, however, were arrested in G1 and showed complete suppression of cdk2 activity that was preceded by a strong up-regulation of the cdk2 inhibitors p21(CIP1) and p27(KIP1). These results demonstrate that growth of HPV16/18-positive cells can be arrested by HDAC inhibitors despite ongoing HPV transcription and thus independently of any potential position effects uncoupling URR-directed gene expression by adjacent cellular promoters or by downstream 3'-polyadenylation sites after viral integration into the host genome during multistep carcinogenesis.
Finzer
Patrick
P
Deutsches Krebsforschungszentrum, Forschungsschwerpunkt Angewandte Tumorvirologie, Abteilung Tumorvirusimmunologie, Im Neuenheimer Feld 242, 69120 Heidelberg, Germany. p.finzer@dkfz.de
Ventz
Robert
R
Kuntzen
Christian
C
Seibert
Nadine
N
Soto
Ubaldo
U
Rösl
Frank
F
D002453:Cell Cycle / Q000187:drug effects; D018797:Cell Cycle Proteins / Q000502:physiology; D002455:Cell Division / Q000187:drug effects; D002460:Cell Line; D050759:Cyclin-Dependent Kinase Inhibitor p21; D050760:Cyclin-Dependent Kinase Inhibitor p27; D016213:Cyclins / Q000494:pharmacology / Q000502:physiology; D003609:Dactinomycin / Q000494:pharmacology; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D056572:Histone Deacetylase Inhibitors; D006801:Humans; D015603:Keratinocytes / Q000187:drug effects / Q000502:physiology; D009856:Oncogene Proteins, Viral / Q000502:physiology*; D027383:Papillomaviridae / Q000187:drug effects* / Q000235:genetics; D050725:Papillomavirus E7 Proteins; D011401:Promoter Regions, Genetic; D012097:Repressor Proteins; D014158:Transcription, Genetic / Q000187:drug effects; D025521:Tumor Suppressor Proteins / Q000502:physiology
C493956:CDKN1A protein, human; D018797:Cell Cycle Proteins; D050759:Cyclin-Dependent Kinase Inhibitor p21; D016213:Cyclins; C068651:E6 protein, Human papillomavirus type 16; D004791:Enzyme Inhibitors; D056572:Histone Deacetylase Inhibitors; D009856:Oncogene Proteins, Viral; D050725:Papillomavirus E7 Proteins; D012097:Repressor Proteins; D025521:Tumor Suppressor Proteins; C059731:oncogene protein E7, Human papillomavirus type 16; D050760:Cyclin-Dependent Kinase Inhibitor p27; D003609:Dactinomycin