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Physical and methylation status of human papillomavirus 16 in asymptomatic cervical infections changes with malignant transformation
  1. Sankhadeep Dutta1,
  2. Chandraditya Chakraborty1,
  3. Arup Kumar Dutta2,
  4. Ranajit Kumar Mandal2,
  5. Susanta Roychoudhury3,
  6. Partha Basu2,
  7. Chinmay Kumar Panda1
  1. 1Department of Oncogene Regulation, Chittaranjan National Cancer Institute, Kolkata, West Bengal, India
  2. 2Department of Gynaecologic Oncology, Chittaranjan National Cancer Institute, Kolkata, West Bengal, India
  3. 3Cancer Biology and Inflammatory Disorder Division, Indian Institute of Chemical Biology, Kolkata, West Bengal, India
  1. Correspondence to Dr C K Panda, Department of Oncogene Regulation, Chittaranjan National Cancer Institute, 37, SP Mukherjee Road, Kolkata, West Bengal 700026, India; ckpanda.cnci{at}gmail.com, ckpanda{at}vsnl.net

Abstract

Aims To evaluate how the genetic and epigenetic profile of human papillomavirus 16 (HPV16) changes from asymptomatic cervical infections to cervical cancer (CaCx) development.

Methods HPV16 physical status, methylation of its early–late promoters and its upstream enhancer sequences were analysed in samples from asymptomatic cervical infections (n=89), pre-neoplastic lesions (low and high grade squamous intraepithelial lesions LSIL/HSIL, n=28) and primary CaCx (n=98).

Results In asymptomatic infection (65%, 58/89) and LSIL/HSIL (57%, 16/28) samples, the episomal form of HPV16 was predominant whereas integration of HPV16 was significantly (p=0.01) higher in CaCx (59%, 57/98). The integrated viral form was also present in asymptomatic (27%, 24/89) and LSIL/HSIL (25%, 7/28) samples. The methylation of the enhancer region was comparable (29–34%) among asymptomatic, LSIL/HSIL and CaCx samples. The episomal form exhibited relatively higher methylation of the early promoter (52%) than that of the late promoter (40%) in asymptomatic infection but the integrated form in asymptomatic carriers showed the opposite methylation pattern (early promoter (42%) vs late-promoter (54%)). A similar pattern was observed in LSIL/HSIL samples, with comparable frequencies (44%) of early and late promoter methylation of the episomal form. However, irrespective of HPV16 physical status, higher methylation of late promoter than that of early promoter was observed in CaCx samples. An inverse correlation was observed between HPV16 integration and overall methylation of the early promoter–enhancer region in CaCx (p=0.05), LSIL/HSIL (p=0.09) and asymptomatic samples (p=0.09).

Conclusions Our study indicates that integration of HPV16 along with changes in methylation pattern of early and late promoters is essential for neoplastic transformation of asymptomatic cervical infections.

  • CERVICAL CANCER
  • HPV
  • INFECTIONS

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