HPV18 L1 and long control region sequences variation and E6/E7 diferential expression in nasopharyngeal and cervical cancers: a comparative study

Abstract

Background The role of high-risk human papillomaviruses (hr-HPVs) in cervical cancer (CC) pathogenesis has long been established. Knowledge about the involvement of hr-HPVs in the etiology of nasopharyngeal cancers (NPC) was not well appreciated until the early 2000s when a clear link began to emerge. However, it is not clear whether HPV oncogenesis in the diferent epithelial cancers is associated with L1 gene and long-control region (LCR) sequences variation. This study aimed to investigate the HPV18 L1 gene and LCR sequences variation in cervical and nasopharyngeal biopsies, and assessed E6 and E7 genes expression level in both cancers. Method Four-hundred and three (403) formalin-fxed parafn-embedded tissues originating from nasopharyngeal (NPC) (279) and cervical (CC) (124) sites were collected from a pathology laboratory, Pathologist Without Borders, Accra, Ghana. Haematoxylin and eosin staining was carried out to confrm the presence of cancer on prepared biopsy sections. DNA was extracted from the confrmed cancer biopsies, followed by PCR using MY09/GP5+/6+primers to detect the presence of HPV and specifc primers for the amplifcation of L1 gene and LCR. Sanger sequencing was carried out to determine HPV genotypes, and L1 and LCR sequences variant of HPV18s in CC and NPC biopsies. The HPV18 E6/E7 mRNA expression pattern in both cancers was determined using RT-qPCR. Results Most of the NPC (45%) and CC (55%) biopsies were HPV18 positive. Comparison of HPV18 L1 sequences obtained from cervical and nasopharyngeal cancer tissues, the L1 sequences from the NPC were highly dissimilar with a 59–100% variation among themselves, and in relation to the reference strains. However, the L1 sequences from the CC were more similar with a 91.0–100% variation among the amplifed sequences. Also, the LCR sequences from CC were quite diferent relative to that of NPC. Results for the diferential expression of E6/E7 in the two cancers showed a higher fold change in E6 expression in the CC tissues than the NPC tissues while a reverse expression pat tern was found for E7 gene. Conclusion The current study reports for the frst-time variations in HPV18 L1 and LCR sequences, and diferential expression of E6/E7 genes in NPC compared to CC, suggesting a possible adaptation mechanism of the virus at difer ent cancer sites.