Oxidant species are involved in T/B-mediated ERK1/2 phosphorylation that activates p53-p21 axis to promote KSHV lytic cycle in PEL cells

Free Radic Biol Med. 2017 Nov;112:327-335. doi: 10.1016/j.freeradbiomed.2017.08.005. Epub 2017 Aug 8.


KSHV is a gammaherpesvirus strongly associated to human cancers such as Primary Effusion Lymphoma (PEL) and Kaposi's Sarcoma. The naturally virus-infected tumor cells usually display latent infection since a minority of cells undergoes spontaneous viral replication. The lytic cycle can be induced in vitro upon appropriate stimuli such as TPA (T), alone or in combination with butyrate (B), (T/B). In previous studies, Protein Kinase C (PKC) δ, Extracellular Signal-regulated Kinase1/2 (ERK1/2) and p53-p21 axis have been separately reported to play a role in KSHV reactivation from latency. Here, we found that these pathways were interconnected to induce KSHV lytic cycle in PEL cells treated with T/B. T/B also increased H2O2 that played an important role in the activation of these pathways. Oxidant specie production correlated with PKC δ activation, as the PKC δ inhibitor rottlerin reduced both H2O2 and KSHV lytic antigen expression. H2O2 contributed to T/B-mediated ERK1/2 activation that mediated p53 phosphorylation at serine 15 (Ser15) and increased p21 expression. Oxidant specie inhibition by quercetin indeed strongly reduced the activation of these pathways, lytic antigen expression and interestingly it also increased T/B-induced cell death. The use of ERK inhibitor PD98059 or p53 silencing demonstrated the importance of p53Ser15 phosphorylation and of p53-p21 axis in KSHV lytic cycle activation. Understanding the role of oxidant species and the molecular mechanisms involved in KSHV lytic cycle induction is particularly important since oxidant species represent the most physiological stimulus for viral reactivation in vivo and it is known that viral production contributes to the maintenance/progression of KSHV associated malignancies.

Keywords: ERK1/2; KSHV; Lytic cycle; Oxidant species; P21; P53; PEL; PKC δ; ROS; TPA/Butyrate.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Antioxidants / pharmacology
  • Butyric Acid / pharmacology*
  • Cell Line, Tumor
  • Cyclin-Dependent Kinase Inhibitor p21 / genetics*
  • Cyclin-Dependent Kinase Inhibitor p21 / metabolism
  • Flavonoids / pharmacology
  • Gene Expression Regulation
  • Herpesvirus 8, Human / drug effects*
  • Herpesvirus 8, Human / pathogenicity
  • Herpesvirus 8, Human / physiology
  • Host-Pathogen Interactions
  • Humans
  • Hydrogen Peroxide / metabolism
  • Lymphocytes / metabolism
  • Lymphocytes / virology*
  • Mitogen-Activated Protein Kinase 1 / antagonists & inhibitors
  • Mitogen-Activated Protein Kinase 1 / genetics
  • Mitogen-Activated Protein Kinase 1 / metabolism
  • Mitogen-Activated Protein Kinase 3 / antagonists & inhibitors
  • Mitogen-Activated Protein Kinase 3 / genetics*
  • Mitogen-Activated Protein Kinase 3 / metabolism
  • Oxidative Stress
  • Phosphorylation
  • Quercetin / pharmacology
  • RNA, Small Interfering / genetics
  • RNA, Small Interfering / metabolism
  • Signal Transduction
  • Tetradecanoylphorbol Acetate / pharmacology*
  • Tumor Suppressor Protein p53 / antagonists & inhibitors
  • Tumor Suppressor Protein p53 / genetics*
  • Tumor Suppressor Protein p53 / metabolism
  • Virus Activation / drug effects
  • Virus Replication / drug effects


  • Antioxidants
  • Cyclin-Dependent Kinase Inhibitor p21
  • Flavonoids
  • RNA, Small Interfering
  • Tumor Suppressor Protein p53
  • Butyric Acid
  • Quercetin
  • Hydrogen Peroxide
  • MAPK1 protein, human
  • Mitogen-Activated Protein Kinase 1
  • Mitogen-Activated Protein Kinase 3
  • Tetradecanoylphorbol Acetate
  • 2-(2-amino-3-methoxyphenyl)-4H-1-benzopyran-4-one