Identification of an HLA-A24-restricted cytotoxic T lymphocyte epitope from human papillomavirus type-16 E6: the combined effects of bortezomib and interferon-gamma on the presentation of a cryptic epitope

Int J Cancer. 2007 Feb 1;120(3):594-604. doi: 10.1002/ijc.22312.


About 50% of cervical cancers are associated with human papillomavirus type 16 (HPV-16), and since the HPV-16 E6 and E7 oncoproteins are constitutively expressed in the tumor cells, they are attractive targets for cytotoxic T lymphocyte (CTL)-mediated immunotherapy. Nevertheless, only a limited number of HPV-16 E6 epitopes have been identified to date. Using reverse immunological methods, we have generated a CTL clone against the HPV-16 E6(49-57) epitope restricted by HLA-A*2402, which is the most common allele in Japan and relatively frequent worldwide, capable of lysing 293T cells transduced with HLA-A*2402 and HPV-16 E6. Although it was unable to recognize the SiHa cervical cancer cell line positive for HPV-16 and HLA-A*2402, the cells became susceptible to lysis when transduced with E6-E7 genes, which was unexpectedly offset by pretreatment with interferon (IFN)-gamma alone. Interestingly, however, combined pretreatment with a proteasome inhibitor, bortezomib and IFN-gamma fully restored CTL-mediated lysis of the original SiHa cells. Furthermore, such intervention of 2 of 4 other cervical cancer cell lines expressing HPV-16 E6 and HLA-A*2402 was found to induce IFN-gamma production by specific CTLs. Tetramer analysis further revealed that induction of E6(49-57)-specific T cells was possible in 5 of 7 patients with HPV-16-positive high grade cervical intraepithelial neoplasia or cervical cancer by in vitro stimulation with E6(49-57) peptide. Thus, these findings together indicate that E6(49-57) is a candidate epitope for immunotherapy and immunological monitoring of such patients.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Amino Acid Sequence
  • Animals
  • Boronic Acids / pharmacology
  • Bortezomib
  • CD8-Positive T-Lymphocytes / immunology
  • Cell Line
  • Cell Line, Tumor
  • Drug Synergism
  • Epitopes, T-Lymphocyte / genetics
  • Epitopes, T-Lymphocyte / immunology*
  • Female
  • Flow Cytometry
  • Gene Expression / drug effects
  • HLA-A Antigens / genetics
  • HLA-A Antigens / immunology*
  • HLA-A24 Antigen
  • Humans
  • Interferon-gamma / pharmacology
  • Mice
  • Middle Aged
  • NIH 3T3 Cells
  • Oncogene Proteins, Viral / genetics
  • Oncogene Proteins, Viral / immunology*
  • Protease Inhibitors / pharmacology
  • Pyrazines / pharmacology
  • RNA, Messenger / genetics
  • RNA, Messenger / metabolism
  • Repressor Proteins / genetics
  • Repressor Proteins / immunology*
  • Reverse Transcriptase Polymerase Chain Reaction
  • T-Lymphocytes, Cytotoxic / drug effects
  • T-Lymphocytes, Cytotoxic / immunology*
  • Uterine Cervical Neoplasms / immunology
  • Uterine Cervical Neoplasms / pathology
  • Uterine Cervical Neoplasms / virology


  • Boronic Acids
  • E6 protein, Human papillomavirus type 16
  • Epitopes, T-Lymphocyte
  • HLA-A Antigens
  • HLA-A*24:02 antigen
  • HLA-A24 Antigen
  • Oncogene Proteins, Viral
  • Protease Inhibitors
  • Pyrazines
  • RNA, Messenger
  • Repressor Proteins
  • Bortezomib
  • Interferon-gamma