Functional regulatory role of STAT3 in HPV16-mediated cervical carcinogenesis

PLoS One. 2013 Jul 18;8(7):e67849. doi: 10.1371/journal.pone.0067849. Print 2013.

Abstract

Signal transducer and activator of transcription 3 (STAT3) is an oncogenic transcription factor constitutively active and aberrantly expressed in cervical cancer. However, the functional role of STAT3 in regulation of HPV's viral oncogene expression and downstream events associated with cervical carcinogenesis is not known. Our present study performed on HPV16-positive cervical cancer cell lines (SiHa and CaSki) and primary tumor tissues revealed a strong positive correlation of constitutively active STAT3 with expression of HPV16 E6 and E7 oncoproteins and a negative association with levels of p53 and pRB. Pharmacologic targeting of STAT3 expression in cervical cancer cell lines either by STAT3-specific siRNA or blocking its tyrosine phosphorylation by AG490 or curcumin led to dose-dependent accumulation of p53 and pRb in cervical cancer cells. Interestingly, the suppression of STAT3 expression or activation was associated with the gradual loss of HPV16 E6 and E7 expression and was accompanied by loss of cell viability. The viability loss was specifically high in HPV16-positive cells as compared to HPV negative C33a cells. These findings substantiate the regulatory role of STAT3 in HPV16-mediated cervical carcinogenesis. Leads obtained from the present study provide a strong rationale for developing novel STAT3-based approaches for therapeutic interventions against HPV infection to control cervical cancer.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Carcinogenesis / metabolism*
  • Caspase 3 / metabolism
  • Cell Line, Tumor
  • Curcumin
  • Electrophoretic Mobility Shift Assay
  • Female
  • Flow Cytometry
  • Gene Expression Regulation, Viral / genetics*
  • Human papillomavirus 16*
  • Humans
  • Immunoblotting
  • Immunohistochemistry
  • Oncogene Proteins, Viral / metabolism*
  • RNA, Small Interfering / genetics
  • STAT3 Transcription Factor / metabolism*
  • Tetrazolium Salts
  • Thiazoles
  • Tyrphostins
  • Uterine Cervical Neoplasms / metabolism
  • Uterine Cervical Neoplasms / virology*

Substances

  • Oncogene Proteins, Viral
  • RNA, Small Interfering
  • STAT3 Transcription Factor
  • STAT3 protein, human
  • Tetrazolium Salts
  • Thiazoles
  • Tyrphostins
  • alpha-cyano-(3,4-dihydroxy)-N-benzylcinnamide
  • Caspase 3
  • thiazolyl blue
  • Curcumin

Grants and funding

The study was supported by research grants from Department of Biotechnology, Government of India to ACB (Grant Support 102/IFD/SAN/PR-1612/2007 & BT/PR6198/Med/14/756/2005), Intramural funding from ICMR to ACB and Senior Research Fellowship to SS and SM. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.