Whole genome sequencing in high-grade cervical intraepithelial neoplasia patients from different ethnic groups in China

Abstract

Cervical cancer (CC) is the fourth most common cancer in women worldwide. It develops through precancerous lesions (cervical intraepithelial neoplasia (CIN), graded from low-grade (CIN1) to high-grade (CIN2-3)). It is well established that precancerous and cancerous cervical lesions are caused by a persistent infection with high-risk types of the human papilloma virus (hrHPV). To have a deeper understanding of the pathogenesis of CIN and CC, we systematically analyzed the landscape of genomic alterations and HPV integration profiles in high-grade CIN2/3. We performed deep whole genome sequencing on exfoliated cervical cells and matched peripheral blood samples from a cohort of 51 Chinese patients (of whom 35 were HPV+) with high-grade CIN from 3 ethnic groups and constructed strict integrated workflow of genomic analysis. In addition, the HPV types and integration breakpoints in the exfoliated cervical cells from these patients were examined. Genomic analysis identified 6 significantly mutated genes (SMGs), including CDKN2A, PIK3CB, FAM20A, RABEP1, TMPRSS2 and SS18L1, in 51 CIN2/3 samples. As none of them had previously been identified as SMGs in the Cancer Genome Atlas cervical squamous cell carcinoma and endocervical adenocarcinoma (TCGA-CESC) cohort, future studies with larger sample size of CINs may be needed to validate our findings. Mutational signature analysis showed that mutational signatures of CINs were dramatically different from CCs, highlighting their different mutational processes and etiologies. Moreover, non-silent somatic mutations were detected in all of the CIN2/3 samples, and 88% of these mutations occurred in genes that also mutated in CCs of TCGA cohort. CIN2 samples had significantly less non-silent mutations than CIN3 samples (P = .0006). Gene ontology and pathway level analysis revealed that functions of mutated genes were significantly associated with tumorigenesis, thus these genes may be involved in the development and progression of CC. HPV integration breakpoints occurred in 28.6% of the CIN2/3 samples with HPV infection. Integrations of common high risk HPV types in CCs, including HPV16, 52, 58 and 68, also occurred in the CIN samples. Our results lay the groundwork for a deeper understanding of the molecular mechanisms underlying the pathogenesis of CC and pave the way for new tools for screening, diagnosis and treatment of cervical precancerous and cancerous lesions.