Analysis of mutations in the E6/E7 oncogenes and L1 gene of human papillomavirus 16 cervical cancer isolates from China

Abstract

Human papillomavirus type 16 (HPV16) has a number of intratypic variants; each has a different geographical distribution and some are associated with enhanced oncogenic potential. Cervical samples were collected from 223 cervical cancer patients and from 196 age-matched control subjects in China. DNA samples were amplified by using primers specific for the E6, E7 and partial L1 regions. Products were sequenced and analysed. It was found by using a PCR-sequence-based typing method that HPV infection rates in China were 92?8 % in cervical cancer patients and 15?8 % in healthy controls. HPV16 was detected in 70?4 % of cervical cancer patients and in 6?1 % of controls. In HPV16-positive cervical cancers, 23?6 % belonged to the prototype, 65?5 % were of the Asian variant, 5?5 % were of African type 1 and 3?6 % were European variants, whilst only one was a new variant that differed from any variant published so far. Prevalences of HPV16 E6 D25E and E113D variants were 67?3 and 9 %, respectively. In addition to D25E and E113D, the following E6 variations were found in this study: R129K, E89Q, S138C, H78Y, L83V and F69L. The results also showed that the prevalences of three hot spots of E7 nucleotide variation, N29S, S63F and a silent variation, nt T846C, were 70?2 % (33/47), 51?1 % (24/47) and 61?7 % (29/47), respectively. The following L1 variations were found in this study: S377A, K387E, E378D, K382E and T379P. It was also found that the average age of Asian variant-positive cervical cancer patients (42?98±10?43 years) was 7?56 years lower than that of prototype-positive patients (50?54±10?91). It is suggested that the high frequency of HPV16 Asian variants might contribute to the high incidence of cervical cancer in China. INTRODUCTIONHuman papillomavirus (HPV) infection is the central cause of cervical cancer (Muñoz, 2000). It has been coevolving with its natural hosts for several million years (Ho et al., 1991). This DNA virus acts by the expression of two viral oncoproteins, E6 and E7. However, not all cervical infections with oncogenic HPV types will progress to cervical cancer. Factors that are described to be important in the risk of progression to cancer are of both host and viral origin. One viral factor is the type/subtype of the papillomavirus involved. Almost 30 distinct types of HPV, both oncogenic and non-oncogenic, have been described to infect the genital tract. Our previous study showed, by using hybrid capture 2, that high-risk HPV prevalence was 89?9 % (427/475) in invasive cervical cancer (ICC) (Wu et al., 2006a). The most common HPV DNA type found in cervical cancers among Chinese women was HPV16 (79?6 %), followed by HPV58 (5?92 %) and HPV33 (3?29 %) (Wu et al., 2006a). Other research reports that HPV16 is the most common, being associated with >50 % of cervical cancers (Muñoz, 2000). HPV16 variants are described in phylogenetic branches, the distribution of which varies geographically. The prototype described by Seedorf et al. (1985) is a German isolate and a member of the European (E) branch....

Human Papillomavirus Type 16 Variant Analysis of E6, E7, and L1 Genes and Long Control Region in Identification of Cervical Carcinomas in Patients in Northeast China

“…Based on our results, it was supposed that genetic movement of D25E mutations might exist in these neighboring areas, for northeast China lies geographically between high-frequency areas (central and southern China and southeast Asia) and low-distribution areas (Russia and Mongolia). T178A, which led to D25E amino acid changes, was found in the Chinese and Japanese populations (5,6,47). The L83V distribution was lower in the Asian population and higher in the American and European populations.…”

“…The L83V distribution was lower in the Asian population and higher in the American and European populations. In Table 3, L83V mutations in northeast China accounted for 5.77%, close to those in central China and southern China, in contrast to that in southwest China (27.61% in Sichuan), 32.56% in Japan, and 84.38% in Russia (Moscow) (5,6,8,9,19,47,52). G94A was also reported in southwest China and Mongolia (8,35).…”

“…Validation of Javanese variants needed more confirmation, because G176A, T178A, and T241G were detected in this variant apart from A276G. Amino acid mutations in HPV 16 variants should be considered in the vaccine design and evasion of the natural immune response (12,17,47). As the target of humoral and cellular immune responses, the amino acid changes of HPV 16 E6 may have effects (2,13,39).…”

“…In this study, N29S accounted for 34.62% of mutations, which varied from 14.29% (southwest China) to 70.21% (central and southern China). G666A varied between northeast China, southwest China, central and southern China, and Indonesia (11,41,47).…”

Characterization of a cluster of oncogenic mutations in E6 of a human papillomavirus 83 variant isolated from a high-grade squamous intraepithelial lesion

“…These HPV16 variants seem to be risk factors for viral persistence; this is probably because of modification of the immunogenic properties of the virus (Grodzki et al, 2006). In fact, differential pathogenicity of HPV16 variants with mutations in E6 has been reported for cervical high-grade squamous intraepithelial lesions (HSIL), invasive cervical cancer and anal HSIL (Da Costa et al, 2002;Grodzki et al, 2006;Wu et al, 2006;Zehbe et al, 1998;Zuna et al, 2009 HPV16 induce markedly faster dividing when grown as organotypic raft cultures (Asadurian et al, 2007;Zehbe et al, 2009). …”