miR-496 expression is altered in oropharyngeal cancers by HPV16 E6

Mason D1, Zang X2,3, Monteiro Marques T4, Gama-Carvalho M4 and Tran N1,2

  1. School Biomedical Engineering. Centre for health Technologies. University of Technology Sydney, NSW, Australia.
  2. The Sydney Head and Neck Cancer Institute, Sydney Cancer Centre, Royal Prince Alfred Hospital, NSW, Australia.
  3. Department of Infectious Diseases and Immunology, University of Sydney, NSW, Australia.
  4. University of Lisboa, Faculty of Sciences, BiolSl- Biosystems and Integrative Sciences Institute, Campo Grande, Lisboa, Portugal.

HPV is a major risk factor for oropharyngeal cancers(OPC), with 75% being associated with HPV16. Infection by the virus is known to regulate small non-coding RNAs, known as miRNAs. MiRNAs have been shown to play a critical role in tumorigenesis. Using an LNA array we determined the expression levels of miRNAs in OPC positive for HPV. miR-33, miR-210, miR-142-3p and miR-496 were differentially expressed between HPV16(+) and HPV16(-) OPCs. Of these miR-496 and miR-33 were the most deregulated. Mechanistically we showed that E6, one of the oncoproteins of HPV16 modulates the expression of miR-496 and miR-33. We then revealed that miR-496 can regulate the transcription factor E2F2, which has been shown to be required for viral replication. A viral/miRNA interactome was constructed to map association between miRNAs and E6. From this analysis, we discovered a mechanistic link between miR-496, miR-33 and E2F2. We believe that E6 increases the expression of SREBF2 which harbours miR-33. The increase in miR-33 regulates transcription factors, (BACH1, STAT5A, and GATA2) which impacts the expression of miR-496. Our study has identified a specific regulatory pathway involving E6, miRNAs and E2F2. These events may be important for viral replication and transformation of the cell. These interactions uncovered between HPV and miRNAs may provide an insight into the cellular mechanisms in HPV positive oropharyngeal SCC, and the aetiology of the disease.