Detection of mutation and polymorphism in marker genes of cervical carcinoma in Bangladeshi patients

Abstract

Cervical cancer is a gynaecologic cancer type that develops in the cervix. Annually 528,000 new cases of cervical cancer are reported with 266,000 deaths, which account for 8% mortality of all female cancer patients. Infection with specific human papillomavirus (HPV) types is considered the most severe risk factor for cervical cancer. In the context of our socioeconomic conditions, an increasing burden of this disease and high mortality rate prevail in Bangladesh. Although several researches related to the epidemiology, HPV vaccination, and treatment modalities have been carried out in our country, any research on mutation locations and frequencies in cervical cancer in Bangladesh is yet to be done. Among the high number of genes involved in different signal transduction and cell growth regulation pathways, five different genomic regions within the top three most frequently mutated genes in COSMIC database with a key role in the development of cervical cancers were selected to study mutation frequency in our patients. These genes are EGFR (Epidermal Growth Factor Receptor), KRAS (Kirsten rat sarcoma), and PIK3CA (phosphatidylinositol-4,5bisphosphate 3-kinase, catalytic subunit alpha). DNA from 46 cervical tissue samples

were extracted and amplified by PCR, using 1 set of primers designed for EGFR and 2

sets of primers designed for two different regions of both PIK3CA and KRAS gene. PCR

products

were purified and sequenced through Sanger cycle sequencing strategy. In silico analysis was done in two steps: nucleotide sequence analysis and its corresponding amino acid analysis. The mutated protein structures were determined by homology modelling using SWISS-MODEL. In total, 39 mutations were found in 28 patient samples. Eleven different mutations (23.91%) were found in amplified EGFR gene fragments, among which 1 was common in seven patient samples. On the other hand, twenty four different mutations (52.17%) were found in PIK3CA gene fragment amplicons, among which 2 were found in more than 1 patient. Four mutations (8.7%) were found in KRAS gene fragment amplified products. Our study shows that except for KRAS, the frequency of observed mutations in our patients is higher than those reported earlier in other parts of the world. The study can be used as a basis to build a mutation database for cervical cancer in Bangladesh. With the possibility of targetable oncogenic mutations, further exploration can be oriented towards establishing future diagnostics, personalized medicine decisions, and other pharmaceutical applications for specific cancer subtypes.