Human papilloma virus (HPV) is a group of 150 different types of related viruses which are known to cause warts, also called papillomas. More than 40 HPV types can cause infection in the genital area of men and women and in some cases, can lead to cervical cancer in women. Cervical cancer is the fourth most common type of cancer in women with a relatively high occurrence in women in developing countries, such as China. While 80% of women will have contracted the virus by age 50, only 1% of those women will actually develop cancer.
The mechanism by which HPV causes cancer is not well understood however; scientists believe there are specific genetic HPV variants which have greater association with the development of cancer. There are 13 types of HPV which are considered to be high-risk in terms of the potential to develop into cancer. Of those 13 types HPV16 is most prevalent, causing more than half of cervical cancer cases worldwide. HPV16 is also classified into four major lineages (A, B, C and D): lineages A1-A3 (European); lineage A4 (Asian); lineage B (African 1); lineage C (African 2); and lineage D (Asian-American and North-American).
Previous research has suggested that lineage D (Asian-American and North-American) types may be able to promote viral persistence leading to cervical cancer development. However; D lineages are rare in East Asia. The oncogenic potential between the different HPV16 variants is not known.
In a recent study published in the journal
Virology researchers sought to investigate the risk implications of HPV16 among Chinese women. They conducted a case-control study including 289 women diagnosed with cervical cancer as well as a control group including women who were HPV16-positive but did not have cancer. HPV genotyping was performed on exfoliated cervical cells of all patients. All HPV16-postive specimens were then analyzed for E6 polymorphisms by PCR in order to determine sequence variants. In addition to the case-control study, they performed a meta-analysis of all eligible epidemiological studies using specific search terms in Pubmed to calculate odds ratios and relevant 95% confidence intervals to determine the association between cervical cancer and HPV16 variants in women.
Their research demonstrated that overall, A4 lineage (Asian) HPV16 variants were significantly associated with the development of cervical cancer compared to other variants within the A lineage (A1-3). Meta-analysis of relevant studies including 703 cases and 323 controls from East Asia confirmed the association between A4 lineage HPV types and development of cervical cancer. These results show that there may be a genetic basis of differences in the ability of HPV16 variants to cause cancer.
Sources:
Virology;
Centers for Disease Control and Prevention
