Transactivation activity of human papillomavirus type 16 E6*I on aldo-keto reductase genes enhances chemoresistance in cervical cancer cells

J Gen Virol. 2012 May;93(Pt 5):1081-1092. doi: 10.1099/vir.0.038265-0. Epub 2012 Jan 25.

Abstract

The oncogenic E6 proteins produced by high-risk human papillomaviruses (HPVs) are invariably expressed in cervical carcinomas and are multifunctional proteins capable of affecting host-cell proliferation by binding and deregulating key host molecules such as p53. High-risk HPVs, including HPV16, have the unique ability to splice the E6 viral transcript, resulting in the production of a truncated E6 protein known as E6*I whose precise biological function is unclear. This study explored the changes in gene expression of the cervical cancer C33A cell line stably expressing HPV16 E6*I (16E6*I) and observed the upregulation of ten genes. Two of these genes were aldo-keto reductases (AKR1Cs), AKR1C1 and AKR1C3, which have been implicated in drug resistance. The results demonstrated that expression of 16E6*I, but not full-length E6, specifically increased AKR1C1 transcript levels although it did not alter AKR1C2 transcript levels. HPV16 E7 alone also had the ability to cause a moderate increase in AKR1C3 at both mRNA and protein levels. Site-directed mutagenesis of 16E6*I revealed that transactivation activity was abolished in R8A, R10A and T17A 16E6*I mutants without altering their intracellular localization patterns. Loss of transactivation activity of the 16E6*I mutants resulted in a significant loss of AKR1C expression and a decrease in drug resistance. Analysis of the AKR1C1 promoter revealed that, unlike the E6 protein, 16E6*I does not mediate transactivation activity solely through Sp1-binding sites. Taken together, it was concluded that 16E6*I has a novel function in upregulating expression of AKR1C and, in concert with E7, has implications for drug treatment in HPV-mediated cervical cancer.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • 20-Hydroxysteroid Dehydrogenases / biosynthesis*
  • 3-Hydroxysteroid Dehydrogenases / biosynthesis
  • Aldo-Keto Reductase Family 1 Member C3
  • Antineoplastic Agents / pharmacology*
  • Cell Line, Tumor
  • Drug Tolerance*
  • Female
  • Gene Expression Profiling
  • Gene Expression*
  • Host-Pathogen Interactions*
  • Human papillomavirus 16 / drug effects
  • Human papillomavirus 16 / genetics
  • Human papillomavirus 16 / pathogenicity*
  • Humans
  • Hydroxyprostaglandin Dehydrogenases / biosynthesis
  • Mutagenesis, Site-Directed
  • Mutant Proteins / genetics
  • Mutant Proteins / metabolism
  • Oncogene Proteins, Viral / genetics
  • Oncogene Proteins, Viral / metabolism*
  • Repressor Proteins / genetics
  • Repressor Proteins / metabolism*
  • Transcriptional Activation

Substances

  • Antineoplastic Agents
  • E6 protein, Human papillomavirus type 16
  • Mutant Proteins
  • Oncogene Proteins, Viral
  • Repressor Proteins
  • 3-Hydroxysteroid Dehydrogenases
  • 20-Hydroxysteroid Dehydrogenases
  • 3 alpha-beta, 20 beta-hydroxysteroid dehydrogenase
  • Hydroxyprostaglandin Dehydrogenases
  • AKR1C3 protein, human
  • Aldo-Keto Reductase Family 1 Member C3